디젤기관에 대한 앳킨슨사이클 구성과 사이클의 열역학적 해석에 관한 연구

Abstract

The present study composed a diesel-atkinson cycle of high expansion as a method of achieving high efficiency in diesel cycle engines. It also interpreted the cycle engine thermodynamically analysis to determine the possibility of the improvement of thermal efficiency and clarified the characteristics of several factors. According to the result of theoretical analysis, heat efficiency was highest when expansion-compression ratio . In addition, diesel engines with high apparent compression ratio had higher expansion-compression ratio than otto engines and consequently, their effect of high expansion was high, which in turn enhanced thermal efficiency. When the atkinson cycle was implemented in a real diesel engine by applying the miller cycle through the variation of the closing time of the intake valve, the effective compression ratio and the quantity of intake air decreased and as a result, the effect of high expansion was not observed. Accordingly, the atkinson cycle can be implemented when the quantity of intake air is compensated by supercharge and the effective compression ratio is maintained at its initial level through the reduction of the clearance volume. In this case, heat efficiency increased by 4.1% at the same expansion-compression ratio when the apparent compression ratio was 20 and the fuel cut off ratio was 2. As explained above, when the atkinson cycle was used for diesel cycle, heat efficiency was improved. In order to realize high expansion through retarding the intake value closing time, the engine needs to be equipped with variable valve timing equipment, variable compression ratio equipment and supercharged pressure equipment. Then a diesel-atkinson cycle engine is realized.