Some Analysises on Effective Combustion Rate of Large Bore Diesel Engine

For simulating an engine cycle in cylinder, it is an important matter how to estimate the thermal loss and the combustion behavior affecting on the engine cycle. Then, the combustion process of a large bore diesel engine was examined through the computation and analysis of effective rates of combustion in relation to rate of fuel injection. Moreover, the thermal loss and the combustion behavior were evaluated. As the results of the investigation followings were concluded.<BR>(1) The effective coefficient of combustion, that are described by the correlation between the calorific value of supplied fuel and the effective heat released by combustion, was defined. By the coefficient, the combustion behavior under the various operating conditions can be analyzed. Moreover, by the coefficient at the end of effective combustion, the thermal loss in a combustion period or the residual fuel after the end of effective combustion can be estimated.<BR>(2) The processes to crank angles of effective rates of combustion were expressed by exponential functions with proper coefficients determined experimentally, and they agree fairly with measuring values. And by the coefficients of exponential functions, the combustion phenomena can be explained well.<BR>(3) The approximate delay of combustion was computed from the correlation between rate of fuel injection and effective rate of combustion. And it is very much interesting that the delay of combustion is expressed by a curve approximately, regardless to the operating conditions, such as brake mean effective pressure, engine revolution, scavenging pressure, and so on.<BR>(4) There may be various methods to simulate the combustion process of diesel engines. One is a method to describe directly the effective rate of combustion with the exponential functions as above-mentioned (2), and another is to describe indirectly in relation to fuel rate of injection as above (1), (3) . The effective rate of combustion expressed by exponential functions and the effective coefficient of combustion are inadequate for simulating the engine cycle respectively, because, for the former, the types of the functions and the ccefficients of that are complex, and because the latter vary complicatedly according to the operating conditions. Consequently, the effective rate of combustion expressed by the approximate delay of combustion is the most convinient for simulating the engine cycle.