Influence of high compression ratio and excess air ratio on performance and emissions of natural gas fuelled spark ignition engine

Abstract

Compressed natural gas is in automotive industry recognized as one of the "cleanest" fossil fuels which can be used in internal combustion engines with a number of benefits. Since natural gas has much higher octane rating than gasoline it is expected that higher compression ratios can be used. The goal of the research is to determine the change of performance of spark ignited engine with the increase of compression ratio to values similar to compression ignited engine while keeping the exhaust emissions on the acceptable level and avoiding knock combustion. Measurements are performed at compression ratios 12, 16, and 18 at three different values of air excess ratio. Methane with known composition from a pressure cylinder is used instead of natural gas and the results are comprised of indicating results (in-cylinder and intake pressure in a crank angle space), emissions, temperatures, and mass-flows on various intake and exhaust positions. Analysis of results shows high influence of compression ratio and excess air ratio on combustion, performance, and exhaust gas emissions.

Cost based optimization of industrial bulk compresed natural gas filling facility operations

“…It has been proposed that CO 2 emission is lower with CNG operation and thus can be a eco-friendly operation. Sremec et al [14] examined the effects of excess air ratio and engine speed on the performance and emissions of CNG fuelled spark ignition engine. As a result of the study, due to the reason of the fact that natural gas has higher octane rating than gasoline, it has been possible to use high compression ratios.…”