Some aspects of the use of natural gas motor fuel in diesel locomotives

Due to the increase in the cost of diesel fuel, much attention is paid to the use of alternative types of fuel on diesel locomotives. Variants of using fuel obtained from coal, plants, gas fields and hydrogen are considered. Natural gas is the cheapest and most accessible today. The use of specially designed gas-piston engines on diesel locomotives, operating when the gas-air mixture is ignited from an external source, is the most attractive option. However, this approach has certain disadvantages:

• it is necessary to create a new engine, since the modernization of existing engines requires serious structural changes;

• gas piston engine operates essentially according to the Otto cycle and has lower efficiency and power indicators as compared to a diesel engine;

• when modernizing existing diesel locomotives, switching to the Otto cycle excludes the possibility of using diesel fuel.

Conversion of diesel locomotives to gas fuel must be carried out using the gas-diesel cycle. This approach is most acceptable for the modernization of diesel locomotives of the existing fleet, since it preserves the thermal performance of the engine and makes it possible to transfer diesel locomotives back to operation on diesel fuel. The main obstacle to the transfer of diesel locomotives to the gas-diesel cycle is the low degree of replacement of diesel fuel with gas. This circumstance is determined by the significant difficulties in ensuring the operation of the engine in the gas-diesel cycle at low loads and idling. It is necessary to ensure a stable supply of ignition fuel in these modes and guaranteed ignition of the gas-air mixture from it. The solution to this problem is ensured by maintaining a given stoichiometric ratio in the gas-air mixture and a temperature sufficient to ignite the ignition portion of the fuel.

The main way to regulate the stoichiometric ratio is to reduce the amount of air entering the cylinders by throttling it at the engine inlet. This article discusses the methodology for calculating the performance of the engine when throttling the air inlet.

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