Thermodynamic Analysis and Comparison of the K6 Cycle

International concerns over small engine efficiency and emissions characteristics have lead to several efforts to develop improved internal combustion engine cycles, including investigation of Homogeneous Charge Compression Ignition (HCCI) and Premixed Charge Compression Ignition (PCCI) modifications to classic combustion cycles. Kashmerick Engine Systems LLC. has proposed a K6 cycle that moves the combustion process to an external continuous-combustion chamber to decrease the rate of combustion and allow optimization of the combustion chamber and piston-cylinder as a compression and expansion device separately to improve efficiency and reduce emissions. This paper describes 0-dimension modeling of both an air-standard dual-cycle model and an air-standard K6 cycle model in Engineering Equation Solver (EES) to compare the ideal performance of the two cycles. The dual-cycle is also correlated to a small engine currently in production to estimate typical compression and expansion efficiencies, which are then used with the K6 cycle model to estimate real-world performance. This work suggests that the K6 cycle may offer improvements over a dual-cycle for several air fuel ratios, and yields a useful tool to aid in optimization of cycle parameters for experimental work.