A diesel engine running entirely on methane will save up to 60% from the amount of normal costs and of course significantly reduce environmental pollution.
We can convert almost any diesel engine to use methane as a gas engine fuel.
Don't wait for tomorrow, start saving today!
How can a diesel engine run on methane?
A diesel engine is an engine in which the fuel is ignited by heating from compression. A standard diesel engine cannot run on gas fuel because methane has a significantly higher ignition temperature than diesel fuel (diesel fuel - 300-330 C, methane - 650 C), which cannot be achieved at the compression ratios used in diesel engines.
The second reason why a diesel engine cannot operate on gas fuel is the phenomenon of detonation, i.e. non-standard (explosive combustion of fuel, which occurs when the compression ratio is excessive. For diesel engines, the compression ratio of the fuel-air mixture is 14-22 times, a methane engine can have a compression ratio of up to 12-16 times.
Therefore, to convert a diesel engine to gas engine mode, you will need to do two main things:
- Reduce engine compression ratio
- Install a spark ignition system
After these modifications, your engine will run only on methane. Returning to diesel mode is possible only after special work has been carried out.
For more information about the essence of the work performed, see the section “How exactly is the conversion of diesel to methane carried out”
How much savings can I get?
The amount of your savings is calculated as the difference between the cost per 100 km of mileage on diesel fuel before engine conversion and the cost of purchasing gas fuel.
For example, for the Freigtleiner Cascadia truck, the average diesel fuel consumption was 35 liters per 100 km, and after conversion to run on methane, the gas fuel consumption was 42 nm3. methane Then, with the cost of diesel fuel being 31 rubles, 100 km. mileage initially cost 1,085 rubles, and after conversion, with the cost of methane being 11 rubles per normal cubic meter (nm3), 100 km of mileage began to cost 462 rubles.
The savings amounted to 623 rubles per 100 km or 57%. Taking into account the annual mileage of 100,000 km, the annual savings amounted to 623,000 rubles. The cost of installing propane on this car was 600,000 rubles. Thus, the payback period for the system was approximately 11 months.
Also, an additional advantage of methane as a gas engine fuel is that it is extremely difficult to steal and almost impossible to “drain”, since under normal conditions it is a gas. For the same reasons, it cannot be sold.
Methane consumption after converting a diesel engine into gas engine mode can vary from 1.05 to 1.25 nm3 of methane per liter of diesel fuel consumption (depending on the design of the diesel engine, its wear, etc.).
You can read examples from our experience in the consumption of methane by diesel engines we have converted.
On average, for preliminary calculations, a diesel engine when operating on methane will consume gas engine fuel at the rate of 1 liter of diesel fuel consumption in diesel mode = 1.2 nm3 of methane in gas engine mode.You can get specific savings values for your car by filling out a conversion application by clicking the red button at the end of this page.
Where can you refuel with methane?
In the CIS countries there are over 500 CNG filling stations, with Russia accounting for more than 240 CNG filling stations.
You can view current information on the location and opening hours of CNG filling stations on the interactive map below. Map courtesy of gazmap.ru
And if there is a gas pipe running next to your vehicle fleet, then it makes sense to consider options for building your own CNG filling station.
Just call us and we will be happy to advise you on all options.
How much mileage will there be on one methane filling station?
Methane on board the vehicle is stored in a gaseous state under high pressure of 200 atmospheres in special cylinders. The large weight and size of these cylinders is a significant negative factor limiting the use of methane as a gas engine fuel.
RAGSK LLC uses in its work high-quality metal-plastic composite cylinders (Type-2), certified for use in the Russian Federation.
The inside of these cylinders is made of high-strength chrome-molybdenum steel, and the outside is wrapped in fiberglass and filled with epoxy resin.
To store 1 nm3 of methane, 5 liters of hydraulic cylinder volume are required, i.e. for example, a 100 liter cylinder allows you to store approximately 20 nm3 of methane (actually a little more, due to the fact that methane is not an ideal gas and is better compressed). The weight of 1 liter of hydraulic is approximately 0.85 kg, i.e. the weight of a storage system for 20 nm3 of methane will be approximately 100 kg (85 kg is the weight of the cylinder and 15 kg is the weight of the methane itself).
Type-2 cylinders for storing methane look like this:
The assembled methane storage system looks like this:
In practice, it is usually possible to achieve the following mileage values:
- 200-250 km - for minibuses. Storage system weight - 250 kg
- 250-300 km - for medium-sized city buses. Storage system weight - 450 kg
- 500 km - for truck tractors. Storage system weight - 900 kg
You can get specific mileage values on methane for your car by filling out a conversion application by clicking the red button at the end of this page.
How exactly is diesel converted to methane carried out?
Converting a diesel engine to gas mode will require serious intervention in the engine itself.
First we have to change the compression ratio (why? see section "How can a diesel engine run on methane?") We use different methods for this, choosing the best one for your engine:
- Piston milling
- Cylinder head gasket
- Installing new pistons
- Shortening the connecting rod
In most cases, we use piston milling (see illustration above).
This is what the pistons will look like after milling:
We also install a number of additional sensors and devices (electronic gas pedal, crankshaft position sensor, oxygen quantity sensor, knock sensor, etc.).
All system components are controlled by an electronic control unit (ECU).
A set of components for installation on the engine will look something like this:
Will engine performance change when running on methane?
Power There is a common belief that an engine loses up to 25% in power when using methane. This opinion is true for dual-fuel gasoline-gas engines and is partly true for naturally aspirated diesel engines.For modern engines equipped with supercharging, this opinion is erroneous.
The high strength life of the original diesel engine, designed to operate with a compression ratio of 16-22 times, and the high octane number of gas fuel allow us to use a compression ratio of 12-14 times. This high compression ratio allows you to get the same (and even greater) power densities, operating on stoicheometric fuel mixtures. However, meeting toxicity standards higher than EURO-3 is not possible, and the thermal stress of the converted engine also increases.
Modern inflatable diesel engines (especially with intermediate cooling of the inflatable air) make it possible to operate on significantly lean mixtures while maintaining the power of the original diesel engine, keeping the thermal regime within the same limits and meeting EURO-4 toxicity standards.
For naturally aspirated diesel engines, we offer 2 alternatives: either reducing operating power by 10-15% or using a water injection system into the intake manifold in order to maintain acceptable operating temperatures and achieve EURO-4 emission standards
Type of typical dependence of power on engine speed, by fuel type:
A radical solution to the problem of shifting the torque peak for a gas engine is to replace the turbine with a special type of oversized turbine with a high-speed wastegate solenoid valve. However, the high cost of such a solution does not give us the opportunity to use it for individual conversion.
Reliability The engine life will increase significantly. Since gas combustion occurs more evenly than diesel fuel, the compression ratio of a gas engine is less than that of a diesel engine and the gas does not contain foreign impurities, unlike diesel fuel. Oil Gas engines are more demanding on the quality of oil. We recommend using high-quality all-season oils of SAE 15W-40, 10W-40 classes and changing the oil at least 10,000 km.If possible, it is advisable to use special oils, such as LUKOIL EFFORSE 4004 or Shell Mysella LA SAE 40. This is not necessary, but with them the engine will last a very long time.
Due to the higher water content in the combustion products of gas-air mixtures in gas engines, problems with the water resistance of motor oils may arise, and gas engines are also more sensitive to the formation of ash deposits in the combustion chamber. Therefore, the sulfate ash content of oils for gas engines is limited to lower values, and the requirements for oil hydrophobicity are increased.
Noise You will be very surprised! A gas engine is a very quiet car compared to a diesel engine. The noise level will decrease by 10-15 dB according to instruments, which corresponds to 2-3 times quieter operation according to subjective sensations.Of course, no one cares about the environment. But anyway… ?
A methane gas engine is significantly superior in all environmental characteristics to an engine of similar power that runs on diesel fuel and is second only to electric and hydrogen engines in terms of emissions.
This is especially noticeable in such an important indicator for large cities as smoke. All city residents are pretty annoyed by the smoky tails behind LIAZs. This will not happen on methane, as there is no soot formation when the gas burns!
As a rule, the environmental class for a methane engine is Euro 4 (without the use of urea or a gas recirculation system). However, by installing an additional catalyst, the environmental class can be increased to Euro 5 level.
1 State Scientific Center of the Russian Federation - Federal State Unitary Enterprise "Central Order of the Red Banner of Labor Scientific Research Automobile and Automotive Institute (NAMI)"
When converting a diesel engine to a gas engine, boost is used to compensate for the reduction in power. To prevent detonation, the geometric compression ratio is reduced, which causes a decrease in the indicator efficiency. The differences between geometric and actual compression ratios are analyzed. Closing the intake valve the same amount before or after BDC causes the same reduction in the actual compression ratio compared to the geometric compression ratio. A comparison of the filling process parameters with standard and shortened intake phases is given. It has been shown that early closing of the intake valve can reduce the actual compression ratio, lowering the detonation threshold, while maintaining a high geometric compression ratio and high indicator efficiency. The shortened inlet increases mechanical efficiency by reducing pumping pressure losses.
gas engine
geometric compression ratio
actual compression ratio
valve timing
indicator efficiency
mechanical efficiency
detonation
pumping losses
1. Kamenev V.F. Prospects for improving the toxic indicators of diesel engines of vehicles weighing more than 3.5 tons / V.F. Kamenev, A.A. Demidov, P.A. Shcheglov // Proceedings of NAMI: collection. scientific Art. – M., 2014. – Issue. No. 256. – P. 5–24.
2. Nikitin A.A. Adjustable drive of the valve for injecting the working medium into the engine cylinder: Pat. 2476691 Russian Federation, IPC F01L1/34 / A.A. Nikitin, G.E. Sedykh, G.G. Ter-Mkrtichyan; applicant and patent holder of the State Scientific Center of the Russian Federation FSUE "NAMI", publ. 02/27/2013.
3. Ter-Mkrtichyan G.G. Engine with quantitative throttleless power control // Automotive industry. - 2014. - No. 3. – P. 4-12.
4. Ter-Mkrtichyan G.G. Scientific foundations for creating engines with a controlled compression ratio: dis. doc. ... tech. Sci. - M., 2004. – 323 p.
5. Ter-Mkrtichyan G.G. Control of piston movement in internal combustion engines. – M.: Metallurgizdat, 2011. – 304 p.
6. Ter-Mkrtichyan G.G. Trends in the development of battery fuel systems for large diesel engines / G.G. Ter-Mkrtichyan, E.E. Starkov // Proceedings of NAMI: collection. scientific Art. – M., 2013. – Issue. No. 255. – pp. 22–47.
Recently, gas engines that are converted from diesel engines by modifying the cylinder head by replacing the injector with a spark plug and equipping the engine with equipment for supplying gas to the intake manifold or intake channels have found quite widespread use in trucks and buses. To prevent detonation, the compression ratio is reduced, as a rule, by modifying the piston.
A gas engine a priori has less power and worse fuel efficiency compared to the base diesel engine. The decrease in power of a gas engine is explained by a decrease in the filling of the cylinders with the air-fuel mixture due to the replacement of part of the air with gas, which has a larger volume compared to liquid fuel. To compensate for the reduction in power, boost is used, which requires an additional reduction in the compression ratio. At the same time, the indicator efficiency of the engine decreases, accompanied by a deterioration in fuel efficiency.
A diesel engine of the YaMZ-536 family (6ChN10.5/12.8) with a geometric compression ratio was chosen as the base engine for conversion to gas ε =17.5 and a rated power of 180 kW at a crankshaft speed of 2300 min -1.
Fig.1. Dependence of the maximum power of a gas engine on the compression ratio (detonation limit).
Figure 1 shows the dependence of the maximum power of a gas engine on the compression ratio (detonation limit). In a converted engine with standard valve timing, a given rated power of 180 kW without detonation can only be achieved with a significant reduction in the geometric compression ratio from 17.5 to 10, causing a noticeable decrease in the indicated efficiency.
Avoiding detonation without reducing or with a minimal reduction in the geometric compression ratio, and therefore a minimal reduction in the indicator efficiency, is possible by implementing a cycle with early closing of the intake valve. In this cycle, the intake valve closes before the piston reaches BDC. After the intake valve closes, when the piston moves to BDC, the gas-air mixture first expands and cools, and only after the piston passes BDC and moves to TDC does it begin to compress. Losses in cylinder filling are compensated by increasing the boost pressure.
The main objectives of the research were to identify the possibility of converting a modern diesel engine into a gas engine with external mixture formation and quantitative control while maintaining the high power and fuel efficiency of the base diesel engine. Let's consider some key points of approaches to solving the problems.
Geometric and actual compression ratio
The beginning of the compression process coincides with the moment of closing the intake valve φ a. If this occurs at BDC, then the actual compression ratio ε f equal to the geometric compression ratio ε. With the traditional organization of the working process, the inlet valve closes 20-40° after BDC in order to improve filling due to additional charging. When implementing a short intake cycle, the intake valve closes to BDC. Therefore, in real engines, the actual compression ratio is always less than the geometric compression ratio.
Closing the intake valve the same amount either before or after BDC causes the same reduction in the actual compression ratio compared to the geometric compression ratio. So, for example, when changing φ a 30° before or after BDC, the actual compression ratio is reduced by approximately 5%.
Changing the parameters of the working fluid during the filling process
During the research, the standard exhaust phases were maintained, and the intake phases were changed by varying the closing angle of the intake valve φ a. In this case, when the intake valve closes early (before BDC) and maintains the standard intake duration (Δφ VP=230°), the intake valve would have to be opened long before TDC, which, due to large valve overlap, would inevitably lead to an excessive increase in the residual gas coefficient and disruptions in the working process. Therefore, early closing of the intake valve required a significant reduction in the intake duration to 180°.
Figure 2 shows a diagram of the charge pressure during the filling process depending on the closing angle of the intake valve to BDC. Pressure at the end of filling p a lower than the pressure in the intake manifold, and the decrease in pressure is greater the earlier the intake valve closes before BDC.
When the intake valve closes at TDC, the charge temperature at the end of filling T a slightly higher than the temperature in the intake manifold Tk. When the intake valve closes earlier, the temperatures become closer and φ a>35...40° PCV charge does not heat up during filling, but cools.
1 - φ a=0°; 2 - φ a=30°; 3 - φ a=60°.
Fig. 2. The influence of the closing angle of the inlet valve on the change in pressure during the filling process.
Optimization of the intake phase at rated power mode
All other things being equal, boost or increasing the compression ratio in engines with external mixture formation is limited by the same phenomenon - the occurrence of detonation. It is obvious that with the same excess air coefficient and the same ignition timing angles, the conditions for the occurrence of detonation correspond to certain pressure values p c and temperature Tc charge at the end of compression, depending on the actual compression ratio.
For the same geometric compression ratio and, therefore, the same compression volume, the ratio p c/ Tc uniquely determines the amount of fresh charge in the cylinder. The ratio of the pressure of the working fluid to its temperature is proportional to density. Therefore, the actual compression ratio shows how much the density of the working fluid increases during the compression process. The parameters of the working fluid at the end of compression, in addition to the actual degree of compression, are significantly influenced by the pressure and temperature of the charge at the end of filling, determined by the occurrence of gas exchange processes, primarily the filling process.
Let's consider engine options with the same geometric compression ratio and the same average indicator pressure, one of which has a standard intake duration ( Δφ VP=230°), and in the other the intake is shortened ( Δφ VP=180°), the parameters of which are presented in Table 1. In the first option, the intake valve closes 30° after TDC, and in the second option, the intake valve closes 30° before TDC. Therefore, the actual compression ratio ε f the two variants with late and early closing of the intake valve are the same.
Table 1
Parameters of the working fluid at the end of filling for standard and shortened inlet
|
Δφ VP, ° |
φ a, ° |
Pk, MPa |
P a, MPa |
ρ a, kg/m 3 |
||
The average indicator pressure at a constant value of the excess air coefficient is proportional to the product of the indicator efficiency and the amount of charge at the end of filling. The indicator efficiency, all other things being equal, is determined by the geometric compression ratio, which is the same in the options under consideration. Therefore, the indicator efficiency can also be assumed to be the same.
The amount of charge at the end of filling is determined by the product of the charge density at the inlet and the filling factor ρ kηv. The use of efficient charge air coolers allows the charge temperature in the intake manifold to be maintained approximately constant regardless of the degree of pressure increase in the compressor. Therefore, we assume as a first approximation that the charge density in the intake manifold is directly proportional to the boost pressure.
In the version with a standard intake duration and closing the intake valve after BDC, the filling coefficient is 50% higher than in the version with a shortened intake and closing the intake valve before BDC.
When the filling coefficient decreases, in order to maintain the average indicator pressure at a given level, it is necessary proportionally, i.e. by the same 50%, increase the boost pressure. Moreover, in the variant with early closing of the intake valve, both the pressure and temperature of the charge at the end of filling will be 12% lower than the corresponding pressure and temperature in the variant with closing of the intake valve after BDC. Due to the fact that in the considered options the actual compression ratio is the same, the pressure and temperature of the end of compression in the option with early closing of the intake valve will also be 12% lower than when closing the intake valve after BDC.
Thus, in an engine with a shortened intake and closing the intake valve before BDC, while maintaining the same average indicator pressure, the likelihood of detonation can be significantly reduced compared to an engine with a standard intake duration and closing the intake valve after BDC.
Table 2 provides a comparison of the parameters of gas engine options when operating at nominal mode.
table 2
Gas engine options parameters
|
Option No. |
|||
|
Compression ratio ε |
|||
|
Inlet valve opening φ s, ° PKV |
|||
|
Inlet valve closing φ a, ° PKV |
|||
|
Compressor pressure ratio pk |
|||
|
Pumping loss pressure pnp, MPa |
|||
|
Mechanical loss pressure pm, MPa |
|||
|
Filling factor η v |
|||
|
Indicator efficiency η i |
|||
|
Mechanical efficiency η m |
|||
|
Effective efficiency η e |
|||
|
Compression start pressure p a, MPa |
|||
|
Compression start temperature T a, K |
Figure 3 shows gas exchange diagrams at different intake valve closing angles and the same filling duration, and Figure 4 shows gas exchange diagrams at the same actual compression ratio and different filling durations.
At rated power mode, intake valve closing angle φ a=30° before BDC actual compression ratio ε f=14.2 and the degree of pressure increase in the compressor π k=2.41. This ensures a minimum level of pumping losses. When the intake valve closes earlier due to a decrease in the filling ratio, it is necessary to significantly increase the boost pressure by 43% (π k=3.44), which is accompanied by a significant increase in pumping loss pressure.
When the intake valve closes early, the charge temperature at the beginning of the compression stroke T a, due to its preliminary expansion, is 42 K lower compared to an engine with standard intake phases.
Internal cooling of the working fluid, accompanied by the removal of part of the heat from the hottest elements of the combustion chamber, reduces the risk of detonation and glow ignition. The filling factor is reduced by a third. It becomes possible to work without detonation with a compression ratio of 15, versus 10 with standard intake duration.
1 - φ a=0°; 2 - φ a=30°; 3 - φ a=60°.
Rice. 3. Diagrams of gas exchange at different angles of closure of the intake valve.
1 -φ a=30° to TDC; 2 -φ a=30° beyond TDC.
Fig.4. Gas exchange diagrams at the same actual compression ratio.
The timing of the engine intake valves can be changed by adjusting their lift height. One of the possible technical solutions is the intake valve lift height control mechanism developed at SSC NAMI. The development of hydraulic drive devices for independent electronic control of the opening and closing of valves, based on the principles industrially implemented in diesel battery fuel systems, has great promise.
Despite the increase in boost pressure and higher compression ratio in an engine with a short intake due to earlier closing of the intake valve and therefore lower compression start pressure, the average pressure in the cylinder does not increase. Therefore, the friction pressure does not increase either. On the other hand, with a shortened inlet, the pressure of pumping losses decreases significantly (by 21%), which leads to an increase in mechanical efficiency.
The implementation of a higher compression ratio in an engine with a short intake causes an increase in indicated efficiency and, in combination with a slight increase in mechanical efficiency, is accompanied by an increase in effective efficiency by 8%.
Conclusion
The results of the studies indicate that early closing of the intake valve allows one to widely manipulate the filling ratio and the actual compression ratio, lowering the knock threshold without reducing the indicator efficiency. The shortened inlet increases mechanical efficiency by reducing pumping pressure losses.
Reviewers:
Kamenev V.F., Doctor of Technical Sciences, Professor, Leading Expert, State Scientific Center of the Russian Federation Federal State Unitary Enterprise “NAMI”, Moscow.
Saikin A.M., Doctor of Technical Sciences, Head of Department, State Scientific Center of the Russian Federation Federal State Unitary Enterprise “NAMI”, Moscow.
Bibliographic link
Ter-Mkrtichyan G.G. CONVERSION OF DIESEL INTO GAS ENGINE WITH REDUCTION OF THE ACTUAL COMPRESSION RATIO // Modern problems of science and education. – 2014. – No. 5.;URL: http://science-education.ru/ru/article/view?id=14894 (access date: 02/01/2020). We bring to your attention magazines published by the publishing house "Academy of Natural Sciences"
The advantages of gas for using it as fuel for cars are the following indicators:
Fuel economy
Fuel economy gas engine- the most important engine indicator - is determined by the octane number of the fuel and the ignition limit of the air-fuel mixture. The octane number is an indicator of the fuel's knock resistance, which limits the fuel's ability to be used in powerful and economical engines with a high compression ratio. In modern technology, the octane number is the main indicator of fuel grade: the higher it is, the better and more expensive the fuel. SPBT (technical propane-butane mixture) has an octane number of 100 to 110 units, so detonation does not occur in any engine operating mode.
An analysis of the thermophysical properties of the fuel and its combustible mixture (heat of combustion and calorific value of the combustible mixture) shows that all gases are superior to gasoline in terms of calorific value, but when mixed with air their energy indicators decrease, which is one of the reasons for the decrease in engine power. The reduction in power when operating on liquefied fuel is up to 7%. A similar engine, when running on compressed methane, loses up to 20% of power.
At the same time, high octane numbers make it possible to increase the compression ratio gas engines and raise the power rating, but only car factories can do this work cheaply. In the conditions of the installation site, this modification is too expensive and often simply impossible.
High octane numbers require an increase in ignition timing by 5°...7°. However, early ignition can lead to overheating of engine parts. In the practice of operating gas engines, there have been cases of burnout of piston crowns and valves due to ignition too early and operation on very lean mixtures.
The specific fuel consumption of the engine is lower, the poorer the fuel-air mixture on which the engine operates, that is, the less fuel there is per 1 kg of air entering the engine. However, very lean mixtures, where there is too little fuel, simply do not ignite from a spark. This sets the limit for improving fuel efficiency. In mixtures of gasoline with air, the maximum fuel content in 1 kg of air, at which ignition is possible, is 54 g. In an extremely lean gas-air mixture, this content is only 40 g. Therefore, in modes when it is not necessary to develop maximum power, an engine running on Natural gas is much more economical than gasoline. Experiments have shown that fuel consumption per 100 km when driving a car running on gas at speeds ranging from 25 to 50 km/h is 2 times less than that of the same car running on gasoline under the same conditions. Gas fuel components have ignition limits that are significantly shifted towards lean mixtures, which provides additional opportunities for improving fuel economy.
Environmental safety of gas engines
Gaseous hydrocarbon fuels are among the most environmentally friendly motor fuels. Emissions of toxic substances from exhaust gases are 3-5 times less compared to emissions when running on gasoline.
Gasoline engines, due to the high value of the lean limit (54 g of fuel per 1 kg of air), are forced to adjust to rich mixtures, which leads to a lack of oxygen in the mixture and incomplete combustion of the fuel. As a result, the exhaust of such an engine may contain a significant amount of carbon monoxide (CO), which is always formed when there is a lack of oxygen. In the case when there is enough oxygen, a high temperature (more than 1800 degrees) develops in the engine during combustion, at which air nitrogen is oxidized by excess oxygen to form nitrogen oxides, the toxicity of which is 41 times greater than the toxicity of CO.
In addition to these components, the exhaust of gasoline engines contains hydrocarbons and products of their incomplete oxidation, which are formed in the near-wall layer of the combustion chamber, where water-cooled walls do not allow liquid fuel to evaporate during the short time of the engine operating cycle and limit the access of oxygen to the fuel. In the case of using gas fuel, all of these factors are much weaker, mainly due to leaner mixtures. Products of incomplete combustion are practically not formed, since there is always an excess of oxygen. Nitrogen oxides are formed in smaller quantities, since with lean mixtures the combustion temperature is much lower. The wall layer of the combustion chamber contains less fuel with lean gas-air mixtures than with richer gasoline-air mixtures. Thus, with correctly adjusted gas engine Carbon monoxide emissions into the atmosphere are 5-10 times less than gasoline emissions, nitrogen oxides are 1.5-2.0 times less, and hydrocarbons are 2-3 times less. This makes it possible to comply with future vehicle toxicity standards (“Euro-2” and possibly “Euro-3”) with proper engine testing.
The use of gas as a motor fuel is one of the few environmental measures, the costs of which are recouped by a direct economic effect in the form of reduced costs for fuels and lubricants. The vast majority of other environmental activities are extremely costly.
In a city with a million engines, the use of gas as fuel can significantly reduce environmental pollution. In many countries, separate environmental programs are aimed at solving this problem, stimulating the conversion of engines from gasoline to gas. Moscow environmental programs are tightening requirements for vehicle owners with regard to exhaust emissions every year. The transition to the use of gas is a solution to an environmental problem combined with an economic effect.
Wear resistance and safety of the gas engine
Engine wear resistance is closely related to the interaction of fuel and engine oil. One of the unpleasant phenomena in gasoline engines is that gasoline washes away the oil film from the inner surface of the engine cylinders during a cold start, when the fuel enters the cylinders without evaporating. Next, gasoline in liquid form enters the oil, dissolves in it and dilutes it, worsening its lubricating properties. Both effects accelerate engine wear. The GOS, regardless of the engine temperature, always remains in the gas phase, which completely eliminates the noted factors. LPG (liquefied petroleum gas) cannot penetrate the cylinder, as happens when using conventional liquid fuels, so there is no need to flush the engine. The cylinder head and cylinder block wear out less, which increases engine life.
If the rules of operation and maintenance are not followed, any technical product poses a certain danger. Gas cylinder installations are no exception. At the same time, when determining potential risks, one should take into account such objective physical and chemical properties of gases as temperature and concentration limits of auto-ignition. For an explosion or ignition to occur, the formation of a fuel-air mixture is necessary, that is, volumetric mixing of gas with air. The presence of gas in a cylinder under pressure eliminates the possibility of air entering there, while in tanks with gasoline or diesel fuel there is always a mixture of their vapors and air.
As a rule, they are installed in the least vulnerable and statistically less frequently damaged areas of the car. Based on actual data, the probability of damage and structural failure of the car body was calculated. The calculation results indicate that the probability of destruction of the car body in the area where the cylinders are located is 1-5%.
Experience in operating gas engines, both here and abroad, shows that engines running on gas are less fire and explosive in emergency situations.
Economic feasibility of application
Operating a vehicle using the GOS brings about 40% savings. Since the mixture of propane and butane is closest in its characteristics to gasoline, its use does not require major alterations in the engine design. The universal engine power system maintains a full-fledged gasoline fuel system and makes it possible to easily switch from gasoline to gas and back. An engine equipped with a universal system can run on either gasoline or gas fuel. The cost of converting a gasoline car to a propane-butane mixture, depending on the selected equipment, ranges from 4 to 12 thousand rubles.
When gas is produced, the engine does not stop immediately, but stops working after 2-4 km. The combined power system “gas plus gasoline” is 1000 km on one refueling of both fuel systems. However, certain differences in the characteristics of these types of fuel still exist. Thus, when using liquefied gas, a higher voltage in the spark plug is required to produce a spark. It can exceed the voltage value when the car is running on gasoline by 10-15%.
Converting the engine to gas fuel increases its service life by 1.5-2 times. The operation of the ignition system is improved, the service life of the spark plugs increases by 40%, and the gas-air mixture is burned more completely than when running on gasoline. Carbon deposits in the combustion chamber, cylinder head and pistons are reduced as the amount of carbon deposits is reduced.
Another aspect of the economic feasibility of using SPBT as a motor fuel is that the use of gas allows us to minimize the possibility of unauthorized fuel dumping.
Cars with a fuel injection system equipped with gas equipment are easier to protect against theft than cars with gasoline engines: by disconnecting and taking with you an easily removable switch, you can reliably block the fuel supply and thereby prevent theft. Such a “blocker” is difficult to recognize, which serves as a serious anti-theft device for unauthorized starting of the engine.
Thus, in general, the use of gas as a motor fuel is cost-effective, environmentally friendly and quite safe.
Much has been said about the advantages of gas engine fuel, in particular methane, but let us remind you about them again.
This is an environmentally friendly exhaust that meets current and even future legal emissions requirements. Within the framework of the cult of global warming, this is an important advantage, since Euro 5, Euro 6 and all subsequent standards will be imposed without fail and the exhaust problem will have to be solved one way or another. By 2020, new vehicles in the European Union will be allowed to produce an average of no more than 95 g of CO2 per kilometer. By 2025, this permissible limit may be lowered further. Methane engines are able to meet these toxicity standards, and not only due to lower CO2 emissions. Particulate emissions from gas engines are also lower than their gasoline or diesel counterparts.
Further, gas engine fuel does not wash away oil from the cylinder walls, which slows down their wear. According to propagandists of gas engine fuel, the engine life magically increases significantly. At the same time, they modestly keep silent about the thermal stress of a gas-powered engine.
And the main advantage of gas engine fuel is the price. The price and only the price covers all the shortcomings of gas as a motor fuel. If we are talking about methane, then this is an undeveloped network of CNG filling stations that literally ties a gas car to a gas station. The number of filling stations with liquefied natural gas is negligible; this type of gas motor fuel today is a niche, highly specialized product. Further, gas equipment takes up part of the payload capacity and usable space; gas equipment is troublesome and expensive to maintain.
Technical progress has given rise to such a type of engine as gas-diesel, which lives in two worlds: diesel and gas. But as a universal means, gas diesel does not fully realize the possibilities of either world. It is not possible to optimize combustion, efficiency or emissions for two fuels on the same engine. To optimize the gas-air cycle, you need a specialized tool - a gas engine.
Today, all gas engines use external gas-air mixture formation and ignition from a spark plug, as in a carburetor gasoline engine. Alternative options are under development. The gas-air mixture is formed in the intake manifold by gas injection. The closer to the cylinder this process occurs, the faster the engine response. Ideally, the gas should be injected directly into the combustion chamber, as discussed below. The complexity of control is not the only disadvantage of external mixture formation.
Gas injection is controlled by an electronic unit, which also regulates the ignition timing. Methane burns slower than diesel fuel, that is, the gas-air mixture should ignite earlier, the advance angle is also adjusted depending on the load. In addition, methane requires a lower compression ratio than diesel fuel. So, in a naturally aspirated engine the compression ratio is reduced to 12–14. Aspirated engines are characterized by a stoichiometric composition of the gas-air mixture, that is, the excess air coefficient a is equal to 1, which to some extent compensates for the loss of power from a decrease in the compression ratio. The efficiency of an atmospheric gas engine is 35%, while that of an atmospheric diesel engine is 40%.
Automakers recommend using special motor oils in gas engines that are characterized by water resistance, low sulfate ash content and at the same time a high base number, but all-season oils for diesel engines of the SAE 15W-40 and 10W-40 classes are not prohibited, which in practice are used in nine cases out of ten.
A turbocharger allows you to reduce the compression ratio to 10–12, depending on the size of the engine and the pressure in the intake tract, and increase the excess air ratio to 1.4–1.5. In this case, the efficiency reaches 37%, but at the same time the thermal stress of the engine increases significantly. For comparison, the efficiency of a turbocharged diesel engine reaches 50%.
The increased thermal stress of a gas engine is associated with the impossibility of purging the combustion chamber when the valves are closed, when the exhaust and intake valves are simultaneously open at the end of the exhaust stroke. The flow of fresh air, especially in a supercharged engine, could cool the surfaces of the combustion chamber, thus reducing the thermal stress of the engine, and also reducing the heating of the fresh charge, this would increase the filling factor, but for a gas engine, valve overlap is unacceptable. Due to the external formation of the gas-air mixture, air is always supplied to the cylinder along with methane, and the exhaust valves must be closed at this time to prevent methane from entering the exhaust tract and causing an explosion.
A reduced compression ratio, increased thermal stress and features of the gas-air cycle require corresponding changes, in particular, in the cooling system, in the design of the camshaft and CPG parts, as well as in the materials used for them to maintain performance and service life. Thus, the cost of a gas engine is not so different from the cost of a diesel equivalent, if not higher. Plus the cost of gas equipment.
The flagship of the domestic automotive industry, KAMAZ PJSC serially produces gas 8-cylinder V-shaped engines of the KamAZ-820.60 and KamAZ-820.70 series with dimensions of 120x130 and a displacement of 11,762 liters. For gas engines, a CPG is used that provides a compression ratio of 12 (the diesel KamAZ-740 has a compression ratio of 17). In the cylinder, the gas-air mixture is ignited by a spark plug installed instead of an injector.
For heavy-duty vehicles with gas engines, special spark plugs are used. Thus, Federal-Mogul supplies the market with spark plugs with an iridium central electrode and a side electrode made of iridium or platinum. The design, materials and characteristics of the electrodes and the spark plugs themselves take into account the operating temperature of a heavy-duty vehicle, which is characterized by a wide range of loads, and a relatively high compression ratio.
KamAZ-820 engines are equipped with a distributed methane injection system into the intake manifold through nozzles with an electromagnetic metering device. Gas is injected into the intake tract of each cylinder individually, which makes it possible to adjust the composition of the gas-air mixture for each cylinder in order to obtain minimal emissions of harmful substances. Gas flow is regulated by a microprocessor system depending on the pressure in front of the injector, the air supply is regulated by a throttle valve driven by an electronic accelerator pedal. The microprocessor system controls the ignition timing, provides protection against methane ignition in the intake manifold in the event of a failure in the ignition system or valve malfunction, as well as engine protection from emergency modes, maintains a given vehicle speed, provides torque limitation on the driving wheels of the vehicle and self-diagnosis when the system is turned on. .
KAMAZ has largely unified the parts of gas and diesel engines, but not all, and many outwardly similar parts for diesel engines - crankshaft, camshaft, pistons with connecting rods and rings, cylinder heads, turbocharger, water pump, oil pump, intake pipeline , oil pan, flywheel housing - not suitable for gas engines.
In April 2015, KAMAZ launched a corps of gas vehicles with a capacity of 8 thousand units of equipment per year. The production is located in the former gas-diesel building of the automobile plant. The assembly technology is as follows: the chassis is assembled and a gas engine is installed on it on the main assembly line of the automobile plant. Then the chassis is towed into the body of gas vehicles for installation of gas equipment and carrying out the entire test cycle, as well as for running-in of vehicles and chassis. At the same time, KAMAZ gas engines (including those modernized with BOSCH components) assembled at the engine production facility are also fully tested and run-in.
Avtodiesel (Yaroslavl Motor Plant), in collaboration with Westport, has developed and produces a line of gas engines based on the YaMZ-530 family of 4- and 6-cylinder in-line engines. The six-cylinder version can be installed on the new generation Ural NEXT vehicles.
As mentioned above, the ideal version of a gas engine is direct gas injection into the combustion chamber, but so far the most powerful global mechanical engineering has not created such a technology. In Germany, research is being carried out by the Direct4Gas consortium, led by Robert Bosch GmbH in partnership with Daimler AG and the Stuttgart Research Institute for Automotive Technology and Engines (FKFS). The German Ministry of Economics and Energy supported the project with 3.8 million euros, which is actually not that much. The project will run from 2015 to January 2017. Na-gora must provide an industrial design of a direct methane injection system and, no less important, the technology for its production.
Compared to current systems that use multipoint manifold gas injection, the advanced direct injection system can increase low-end torque by 60%, eliminating the weak point of a gas engine. Direct injection solves a whole complex of “childhood” diseases of a gas engine, brought along with external mixture formation.
The Direct4Gas project is developing a direct injection system that can be reliable and sealed and dose the exact amount of gas for injection. Modifications to the engine itself are kept to a minimum so that the industry can use the same components. The project team is equipping experimental gas engines with a newly developed high-pressure injection valve. The system is supposed to be tested in the laboratory and directly on vehicles. Researchers are also studying the formation of the fuel-air mixture, the ignition control process and the formation of toxic gases. The long-term goal of the consortium is to create conditions under which the technology can enter the market.
So, gas engines are a young area that has not yet reached technological maturity. Maturity will come when Bosch and his friends create technology for directly injecting methane into the combustion chamber.
Evgeniy Konstantinov
While gasoline and diesel fuel are inexorably becoming more expensive, and all sorts of alternative power plants for vehicles remain terribly far from the people, losing to traditional internal combustion engines in price, autonomy and operating costs, the most realistic way to save on refueling is to switch the car to a “gas diet”. At first glance, this is beneficial: the cost of re-equipping the car soon pays off due to the difference in the price of fuel, especially for regular commercial and passenger transportation. It is not without reason that in Moscow and many other cities a significant share of municipal vehicles have long been switched to gas. But here a logical question arises: why then does the share of gas-cylinder vehicles in the traffic flow both in our country and abroad not exceed several percent? What is the other side of a gas cylinder?
Science and life // Illustrations
Warning signs at gas stations are installed for a reason: every connection of a process gas pipeline is a potential location for flammable gas leaks.
Cylinders for liquefied gas are lighter, cheaper and more varied in shape than for compressed gas, and therefore they are easier to arrange based on the free space in the car and the required power reserve.
Please note the difference in price between liquid and gaseous fuels.
Cylinders with compressed methane in the back of a tented Gazelle.
The evaporator reducer in a propane system requires heating. The photo clearly shows the hose connecting the gearbox liquid heat exchanger to the engine cooling system.
Schematic diagram of the operation of gas equipment on a carburetor engine.
Diagram of operation of equipment for liquefied gas without converting it into the gaseous phase in an internal combustion engine with distributed injection.
Propane-butane is stored and transported in tanks (in the photo - behind the blue gate). Thanks to this mobility, the gas station can be placed in any convenient place, and, if necessary, quickly moved to another.
Not only cars, but also household cylinders are refueled at a propane pump.
The liquefied gas dispenser looks different from the gasoline dispenser, but the refueling process is similar. The amount of fuel added is measured in liters.
The concept of “gas automobile fuel” includes two completely different mixtures in composition: natural gas, in which up to 98% is methane, and propane-butane produced from associated petroleum gas. In addition to unconditional flammability, they also have in common their state of aggregation at atmospheric pressure and temperatures comfortable for life. However, at low temperatures, the physical properties of these two sets of light hydrocarbons are very different. Because of this, they require completely different equipment for storage on board and supply to the engine, and in operation, cars with different gas supply systems have several significant differences.
Liquefied gas
The propane-butane mixture is well known to tourists and summer residents: it is what is filled into household gas cylinders. It also makes up the bulk of gas that is wasted in the flares of oil production and processing enterprises. The proportional composition of the propane-butane fuel mixture may vary. The point is not so much in the initial composition of petroleum gas, but in the temperature properties of the resulting fuel. As a motor fuel, pure butane (C 4 H 10) is good in all respects, except that it turns into a liquid state already at 0.5 ° C at atmospheric pressure. Therefore, less high-calorie, but more cold-resistant propane (C 2 H 8) with a boiling point of –43 ° C is added to it. The ratio of these gases in the mixture sets the lower temperature limit for the use of fuel, which for the same reason can be “summer” and “winter”.
The relatively high boiling point of propane-butane, even in the “winter” version, allows it to be stored in cylinders in the form of a liquid: already under low pressure it passes into the liquid phase. Hence another name for propane-butane fuel - liquefied gas. This is convenient and economical: the high density of the liquid phase allows you to fit a large amount of fuel into a small volume. The free space above the liquid in the cylinder is occupied by saturated steam. As the gas is consumed, the pressure in the cylinder remains constant until it is empty. When refueling, drivers of propane cars should fill the tank to a maximum of 90% in order to leave room inside for a vapor cushion.
The pressure inside the cylinder primarily depends on the ambient temperature. At subzero temperatures it drops below one atmosphere, but even this is enough to maintain the system’s functionality. But with warming it is growing rapidly. At 20°C the pressure in the cylinder is already 3-4 atmospheres, and at 50°C it reaches 15-16 atmospheres. For most automobile gas cylinders, these values are close to the maximum. This means that if it overheats on a hot afternoon in the southern sun, a dark car with a liquefied gas cylinder on board... No, it will not explode, like in a Hollywood action movie, but will begin to release excess propane-butane into the atmosphere through a safety valve designed specifically for such a case . By the evening, when it gets colder again, there will be noticeably less fuel in the cylinder, but no one and nothing will get hurt. True, as statistics show, individual fans of additional savings on a safety valve add to the chronicle of incidents from time to time.
Compressed gas
Other principles underlie the operation of gas-cylinder equipment for vehicles that consume natural gas as fuel, commonly referred to as methane after its main component. This is the same gas that is supplied through pipes to city apartments. Unlike petroleum gas, methane (CH 4) has a low density (1.6 times lighter than air), and most importantly, a low boiling point. It turns into a liquid state only at –164°C. The presence of a small percentage of impurities of other hydrocarbons in natural gas does not significantly change the properties of pure methane. This means that it is incredibly difficult to turn this gas into a liquid for use in a car. In the last decade, work has been actively carried out on the creation of so-called cryogenic tanks, which make it possible to store liquefied methane in a car at temperatures of –150°C and below and pressures of up to 6 atmospheres. Prototypes of vehicles and gas stations for this fuel option were created. But so far this technology has not received practical distribution.
Therefore, in the vast majority of cases, for use as a motor fuel, methane is simply compressed, bringing the pressure in the cylinder to 200 atmospheres. As a result, the strength and, accordingly, the mass of such a cylinder should be noticeably higher than for a propane one. Yes, and the same volume of compressed gas fits significantly less than liquefied gas (in terms of moles). And this is a reduction in the autonomy of the car. Another negative is the price. The significantly greater safety margin built into methane equipment results in the fact that the price of a complete set for a car turns out to be almost ten times higher than propane equipment of a similar class.
Methane cylinders come in three sizes, of which only the smallest, with a volume of 33 liters, can be placed in a passenger car. But in order to ensure a guaranteed range of three hundred kilometers, five such cylinders are needed, with a total mass of 150 kg. It’s clear that in a compact city runabout it makes no sense to constantly carry such cargo instead of useful luggage. Therefore, there is a reason to convert only large cars to methane. First of all, trucks and buses.
With all this, methane has two significant advantages over oil gas. Firstly, it is even cheaper and is not tied to the price of oil. And secondly, methane equipment is structurally insured against problems with winter operation and allows, if desired, to do without gasoline altogether. In the case of propane-butane, this trick will not work in our climatic conditions. The car will in fact remain dual-fuel. The reason is precisely the liquefied nature of the gas. More precisely, the gas cools sharply during the process of active evaporation. As a result, the temperature in the cylinder and especially in the gas reducer drops significantly. To prevent the equipment from freezing, the gearbox is heated by integrating a heat exchanger connected to the engine cooling system. But for this system to start working, the liquid in the line must be preheated. Therefore, it is recommended to start and warm up the engine at ambient temperatures below 10°C strictly on gasoline. And only then, when the engine reaches operating temperature, switch to gas. However, modern electronic systems switch everything themselves, without driver assistance, automatically controlling the temperature and preventing the equipment from freezing. True, to maintain the correct operation of the electronics in these systems, you should not empty the gas tank completely, even in hot weather. The gas starting mode is an emergency for such equipment, and the system can only be switched to it forcibly in case of emergency.
Methane equipment does not have any difficulties with winter start-up. On the contrary, it is even easier to start the engine with this gas in cold weather than with gasoline. The absence of a liquid phase does not require heating of the reducer, which only reduces the pressure in the system from 200 transport atmospheres to one working atmosphere.
The wonders of direct injection
The most difficult thing to convert to gas is modern engines with direct fuel injection into the cylinders. The reason is that gas injectors are traditionally located in the intake tract, where mixture formation occurs in all other types of internal combustion engines without direct injection. But the presence of such completely negates the possibility of adding gas power so easily and technologically. Firstly, ideally, gas should also be supplied directly to the cylinder, and secondly, and this is even more important, liquid fuel serves to cool its own direct injection injectors. Without it, they very quickly fail from overheating.
There are options for solving this problem, at least two. The first converts the engine into a dual-fuel engine. It was invented quite a long time ago, even before the advent of direct injection on gasoline engines, and was proposed for adapting diesel engines to run on methane. Gas does not ignite due to compression, and therefore the “carbonated diesel” starts on diesel fuel and continues to operate on it at idle speed and minimum load. And then gas comes into play. It is due to its supply that the crankshaft rotation speed is controlled in medium and high speed modes. To do this, the injection pump (high pressure fuel pump) limits the supply of liquid fuel to 25-30% of the nominal value. Methane enters the engine through its own line, bypassing the injection pump. There are no problems with its lubrication due to a decrease in diesel fuel supply at high speeds. Diesel injectors continue to be cooled by the fuel passing through them. True, the thermal load on them at high speeds still remains increased.
A similar power supply scheme began to be used for gasoline engines with direct injection. Moreover, it works with both methane and propane-butane equipment. But in the latter case, an alternative solution that appeared quite recently is considered more promising. It all started with the idea to abandon the traditional gearbox with an evaporator and supply propane-butane to the engine under pressure in the liquid phase. The next steps were the abandonment of gas injectors and the supply of liquefied gas through standard gasoline injectors. An electronic matching module was added to the circuit, connecting a gas or gasoline line depending on the situation. At the same time, the new system has lost the traditional problems with cold starts on gas: no evaporation - no cooling. True, the cost of equipment for engines with direct injection in both cases is such that it pays off only with very long mileage.
By the way, economic feasibility limits the use of gas equipment in diesel engines. It is for reasons of benefit that only methane equipment is used for engines with compression ignition, and its characteristics are suitable only for heavy equipment engines equipped with traditional fuel injection pumps. The fact is that converting small, economical passenger engines from diesel to gas does not pay for itself, and the development and technical implementation of gas-cylinder equipment for the latest engines with a common fuel rail (common rail) are considered economically unjustified at the present time.
True, there is another, alternative way to convert diesel to gas - through complete conversion into a gas engine with spark ignition. In such an engine, the compression ratio is reduced to 10-11 units, spark plugs and high-voltage electrics appear, and it says goodbye to diesel fuel forever. But it begins to consume gasoline painlessly.
Working conditions
Old Soviet instructions for converting gasoline cars to gas required grinding the cylinder heads (cylinder heads) to raise the compression ratio. This is understandable: the objects of gasification in them were the power units of commercial vehicles that ran on gasoline with an octane rating of 76 and lower. Methane has an octane number of 117, while propane-butane mixtures have an octane number of about one hundred. Thus, both types of gas fuel are significantly less prone to detonation than gasoline and allow the engine compression ratio to be raised to optimize the combustion process.
In addition, for archaic carburetor engines equipped with mechanical gas supply systems, increasing the compression ratio made it possible to compensate for the loss of power that occurred when switching to gas. The fact is that gasoline and gases are mixed with air in the intake tract in completely different proportions, which is why when using propane-butane, and especially methane, the engine has to run on a significantly leaner mixture. The result is a decrease in engine torque, leading to a drop in power by 5-7% in the first case and by 18-20% in the second. At the same time, on the graph of the external speed characteristic, the shape of the torque curve of each specific motor remains unchanged. It simply moves down along the “Newton-meter axis.”
However, for engines with electronic injection systems equipped with modern gas supply systems, all these recommendations and figures have almost no practical meaning. Because, firstly, their compression ratio is already sufficient, and even to switch to methane, work on grinding the cylinder head is completely unjustified economically. And secondly, the gas equipment processor, coordinated with the car’s electronics, organizes the fuel supply in such a way that it at least half compensates for the above-mentioned torque gap. In systems with direct injection and in gas-diesel engines, gas fuel in certain speed ranges is even capable of increasing torque.
In addition, the electronics clearly monitor the required ignition timing, which when switching to gas should be greater than for gasoline, all other things being equal. Gas fuel burns slower, which means it needs to be ignited earlier. For the same reason, the thermal load on the valves and their seats increases. On the other hand, the shock load on the cylinder-piston group becomes smaller. In addition, winter starting on methane is much more useful for it than on gasoline: the gas does not wash away the oil from the cylinder walls. And in general, gas fuel does not contain metal aging catalysts; more complete combustion of the fuel reduces exhaust toxicity and carbon deposits in the cylinders.
Autonomous swimming
Perhaps the most noticeable disadvantage of a gas car is its limited autonomy. Firstly, gas fuel consumption, if calculated by volume, is greater than gasoline and, especially, diesel fuel. And secondly, the gas car turns out to be tied to the corresponding gas stations. Otherwise, the point of converting it to alternative fuel begins to approach zero. It is especially difficult for those who drive on methane. There are very few methane gas stations, and they are all connected to main gas pipelines. These are simply small compressor stations on branches of the main pipe. In the late 80s - early 90s of the twentieth century, our country tried to actively convert transport to methane as part of a state program. It was then that most methane gas stations arose. By 1993, 368 of them had been built, and since then this number has grown, if at all, only slightly. Most gas stations are located in the European part of the country near federal highways and cities. But at the same time, their location was determined not so much from the point of view of the convenience of motorists, but from the point of view of gas workers. Therefore, only in very rare cases were gas stations located directly next to the highway and almost never inside megacities. Almost everywhere, in order to refuel with methane, you need to make a detour of several kilometers to some industrial zone. Therefore, when planning a long-distance route, you need to look for these gas stations and remember them in advance. The only thing that is convenient in such a situation is the consistently high quality of fuel at any of the methane stations. Gas from the main gas pipeline is very problematic to dilute or spoil. Unless the filter or drying system at one of these gas stations suddenly fails.
Propane-butane can be transported in tanks, and thanks to this property, the geography of gas stations for it is significantly wider. In some regions you can refuel with it even in the most remote outback. But it also wouldn’t hurt to research the availability of propane gas stations along your upcoming route, so that their sudden absence on the highway doesn’t become an unpleasant surprise. At the same time, liquefied gas always leaves some risk of using fuel that is out of season or simply of poor quality.
