Theoretical and Experimental Investigation of the Performance of an Atkinson Cycle Engine

摘要

In this study, an Otto cycle engine was converted to the Atkinson cycle engine using the method of late intake valve closingand increasing the compression ratio. Firstly, the thermodynamic analysis was conducted. In the analysis, the variation ofspecific heats with temperature, heat losses, pumping, and mechanical friction losses was taken into account. In-cylinder pressurevariations, torque, power, thermal efficiency and brake-specific fuel consumption variations with speed were obtained.For the experimental study, a new camshaft was designed and manufactured using a circular arc curve. The IVC timing of theAtkinson engine was delayed by a 20° crankshaft angle with respect to standard timing. The compression ratio was increasedfrom 8.5 to 9.5. Tests were conducted at 1400–3400 rpm speed range at WOT. Experiments were conducted at three differentoperating conditions: Otto cycle for the standard engine, late closing of the intake valve at 20 ° CA at 8.5 compression ratioand late closing of the intake valve at 20 ° CA at 9.5 compression ratio. In the tests, the variation of torque, power, BSFC andthermal efficiency with speed were investigated. The results showed that torque, power, BSFC and thermal efficiency wereimproved with Atkinson CR9.5 operation compared to the standard Otto cycle operation at high speeds. It was obtained thatthe torque and power of the Atkinson CR9.5 cycle engine increased by 6.7% and the thermal efficiency increased by 12.8%at 3400 rpm speeds. In addition, BSFC of the Atkinson CR9.5 engine decreased by 12.7%.