This project was a continuation of previous work into the performance predictions of high output diesel engines by mathematical simulation. The project specified that particular attention should be given to the problem of predicting heat transfer. To meet the aims of the project computer programs were developed in FORTRAN for the evaluation of performance. These programs have been used successfully by many people and operate satisfactorily. The computed results were compared with treasured values where possible. Having developed the programs successfully these were used for performance predictions over a very large range of engine parameters for four types of engine, viz four stroke and two stroke valve-in-head, opposed piston and loop scavenge engines. The general trend of the results was that the two stroke engines develop more power than the comparable four stroke engine throughout the range of boost ratio (2 <rc <6). However, the thennal loading of the two strokes was very much higher and this could well reduce their advantage. A method of calculating heat transfer was developed using a technique called representative velocities. This entailed calculating a representative value of the gas motion in the cylinder and relating this to the heat transfer. The method gave reasonable results for two stroke uniflow scavenge engines, using unadjusted common beat transfer expressions. It was found necessary to derive a purely empirical relationship for four stroke and two stroke loop scavenge engines. The mathematical models and the programs arc discussed in this volume.
|Date of Award||1970|