Date of Award
Mechanical, Automotive, and Materials Engineering
Combustion, Engine, Lean limit, Methane, Natural Gas, Split-Cycle
With increasing focus on efficiency and reduction of greenhouse gases, combustion processes need to be improve. Whether through use of alternative fuel or alternative combustion cycles, improvements to the combustion process are desired. Natural gas composed primarily of methane is an alternative fuel for internal combustion engines that has a potential to meet these goals. It has a high octane number, reduced CO2 output and lower emissions than other gases. Natural gas has a low laminar flame speed, making its implementation in internal combustion engines challenging. A split-cycle engine has been constructed at the University of Windsor to address issues typical of natural gas combustion. The architecture promotes intense turbulence leading to improved burn rates. Testing on the split-cycle has shown burn durations under 30°CA, amongst the fastest for natural gas engines presented in literature. This work will address two issues with the split-cycle engine, the high lean limit of operation and the low loads achieved by the engine. The lean limit of operation is extended using a dual coil ignition strategy, increasing energy input to the kernel, thereby increasing stability. Secondly, it has been shown that early exhaust valve closure results in excessive combustion products being in-cylinder, resulting in 15-25% charge dilution. A change in exhaust valve timing is shown to effect the lean limit of operation. Low loads are attempted to be addressed with a change of valve timing. The valve timing change results in improved combustion parameters yet poorer indicated output. This cause of this issue is determined using a mass balance analysis which shows that the mass ow rate through the system is partially dependent on the mass transfer from the crossover passage, which should be optimized for the best performance for this type of engine. A new parameter that is used to characterize split-cycle engine performance, the mass compressed ratio, is defined in this work.
Dal Bello, Steven, "Exploration of the Lean Limit in a Split-Cycle Engine" (2019). Electronic Theses and Dissertations. 7634.