Improvement of Start Mode and Post-Start Heating of Diesel Engines

Analysis of published data demonstrates that at present, the most common method of efficiency estimation of thermal machines is the method of thermal balance, which is characterized by certain drawbacks.This work is aimed at development of partial procedure of estimation of quantity and quality of exergy fluxes in air and fuel supply systems and their influence on engine starting characteristics and incomplete fuel combustion during poststart heating.During start, ignition in diesel cylinder is determined by air temperature at the end of compression (Tc) and heat consumptions for heating, evaporation, and overheating of fuel vapors.It is obvious that the exergy of fuel injected into cylinder in terms of quantity is significantly lower than that of compressed air, however, the fuel exergy mainly determines heat and mass transfer in the area of front of fuel sprays and, as a consequence, diesel starting properties and completeness of combustion during post-start period.Analysis of exergy balance for fuel supply system demonstrates that atomization during start and post-start heating at negative ambient temperatures can be controlled with minimum consumptions of energy by fuel preheating in nozzle immediately before its injection into combustion chamber.Partial procedure has been developed based on exergy method allowing to estimate quantitatively the exergy fluxes in air and fuel supply systems and, thus, the rate of activity of fuel spray and energy supply of air charge during start and post-start heating of tractor engine.