Coupling Simulation And Experimental Research On The Working Process Of An Opposed-piston Two-stroke Diesel Engine

Opposed-piston two-stroke Diesel Engine (OP2S) is a new type of reciprocating pistoninternal combustion engine. Recently, since its dramatically advantages such as highthermal efficiency, high power density and excellent balance performance, OP2S isbecoming an increasingly popular topic among researchers. There are strong relationshipsbetween gas exchange process and in-cylinder process of OP2S. Moreover, gas exchangeprocess and in-cylinder gas motion are quilt different from that in the conventional dieselengines. However, few researchers paid attention on this points and the working processand coupling relationships of OP2S need to be studied deeply.In this paper, an opposed-piston two-stroke crank fold diesel engine was analyzed. Inorder to study working process of OP2S, coupling relationships between dynamic, thermaldynamic and fluid dynamic were investigated. On this basis, coupling simulation modelsystem was established including piston dynamic model, thermal dynamic and CFD model.Then parameters influence law, in-cylinder gas motion and combustion character werestudied and analyzed. The main research contents are as follows:1. According to the working principle of OP2S, coupling relationships betweendifferent subjects were analyzed, as a result coupling simulation model system wasestablished.2. Base on the calculation generated by the coupling simulation model system, effectsof characteristic parameters on the working process were investigated. In addition,evaluation indexes of two-stroke engine gas exchange process were perfected.3. A new gas exchange system optimization method, which employed IMEP (Indicatedmean effective pressure) as optimization object was raised. The key parameters in gasexchange process were optimized with orthogonal method and the correlations between theevaluation indicator and the parameters were analyzed by the correlation coefficients.4. In-cylinder gas motion of OP2S was calculated. Influences of port structure on airflow were comparatively analyzed.5. With the consideration of the coupling between the gas exchange process and thein-cylinder working process, a cold flow calculation was made and the effect of swirl intakeports and tumble intake ports on the gas exchange process and in-cylinder gas motionprocess was analyzed. As a result, swirl intake ports contribute to the engine performance. 6. CFD numerical simulation was applied to study the nozzle diameter’s, cone angle’sand injection rate profile’s effects on the mixture formation and combustion process to findtheir optimum values.7. The heat release rate and combustion characteristic were acquired by calculationusing indicated diagrams measured by experiments. Through the study of combustioncycle-to-cycle variations in OP2S, it was found that the coefficient of variation in OP2Swas higher than that in traditional diesel engines.In this paper, to some extent, has enriched the research measures in studing OP2Sworking process, and made some useful results in explorating the mechanism of theworking process. It provides supports to optimize the performance of OP2S and guides theoptimized design in the folding crank OP2S.