Performance Simulation And Optimization Design Study For A Split-cycle Engine

The split cycle engine is a new engine based on predecessors’ split cycle designconcept, which makes an optimization design on traditional four-stroke engineinternal structure with the Otto cycle. It has the advantage when trying to incorporatethe features of no throttling, high compression ratios, and miller over expansion,which brings life for the development of traditional engine, thus the split cycle engineis of great research significance. In this paper, a thorough theoretical study has beenconducted on the simulation and optimization design for Scuderi split cycle engineperformance.On the basic of analysis split cycle engine structure and working process, the1Dsimulation of which is studied with AVL BOOST software. First, a parametric modelof split cycle engine is established, and the accuracy of the model is verified. Throughthe thermodynamic cycle calculation of the model, the most performance indicators atfour speed full load are predicted, and the cylinder pressure, temperature curveschanging with the crank angle at4000r/min are analyzed. Then, a1D simulationmodel of the traditional four-stroke cycle engine with similar type is established. Thepower performance and economic performance of the two engines is compared underthe condition of the same displacement. The results show that compared with thetraditional four-stroke cycle engine, the power performance of the split cycle engineis poorer in low speed, and is better slightly at high speed. The output torque curve isflat. It has an advantage in economic performance.The improvement of the enginethermal efficiency has realized.To guide the split-cycle engine development in theory, key design parameters,such as the top dead center phase difference between the compressor cylinder and theexpander cylinder, compression ratio, expansion ratio, valve timing and maximumvalve lift values of the compressor cylinder and the expander cylinder, and enginepower output characteristics, were optimized based on simulation with responsesurface method using AVL DESIGN EXPLORER software. First, with Latinhypercube experimental design, the effect of key design parameters on engine powerperformance and the effect significance of which are analyzed, and the main influencing factors are found. Then, the quadratic polynomial response surface modelis established and the accuracy of the model is tested. Finally, the key designparameters are optimized with NLPQL algorithm to make the engine powerperformance greatest, and the best project meeting the design requirements isobtained. The results show that the expander cylinder exchange valve closing time isthe most important influence parameter. After optimization, the output torque of thefour conditions is improved under the condition of guarantee no deflagration, and themean torque was improved by3.79N.m. The optimization of the design goals isachieved.