Improvement of starting characteristics of a diesel engine with low compression ratio by using of inlet electric air heaters

The paper deals with the improvement of starting characteristics of diesel engine with low compression ratio. The processes in inlet manifold and cylinder of diesel engine during pre-start preparation and start-up are submitted as the subject of study. The purpose is to improve the starting characteristics of diesel engine with low compression ratio by using of inlet electrical air heaters instead of electric torch device. The object of study is a modification of tractor constant power engine of 4ChN 15/20.5 type with low compression ratio equal to 12.5. During the experiment one electric torch device and three tubular electric heaters with heat power of 0.8 kW each were sequentially installed in the inlet manifold of diesel engine. A calculation method for heat transfer from the surface of inlet manifold to the ambient air is proposed. Conditions of fuel self-ignition in the combustion chamber of diesel engine with electric torch device are theoretically substantiated, as well as its critical shortcomings, namely: raise of temperature of fuel self-ignition due to the decrease in oxygen concentration of air charge in cylinders, as a result of its consumption in the flame of electric torch device; ability to work only during engine cranking by electric starter with a limited timespan of 20 seconds. It is proved that a valid method providing the cold starting of 4ChN 15/20.5 diesel engine with low compression ratio equal to 12.5 is air preheating by tubular electric heaters placed throughout the length of inlet manifold, with total heat power of 1.6-2.4 kW. Rational design parameters of a cold start aid system with tubular electric heaters and its operation modes are determined. The results of the study were used for modernization of production models of ChTZ-Uraltrac tractor diesel engines and for development of new ones, so they can be recommended for introduction in engine building companies.

diesel engine, start-up, testing, starting aid, inlet air heating