Comparison of gas engine performance with different gas supply methods

Abstract

The results of comparative tests of a spark-ignition engine are presented, in which natural gas was injected directly into the cylinder during different phases of the power cycle: during the intake stroke and, in the second case, during the compression stroke. The comparison was based on the cycle work, the values of which were determined by analyzing the indicator diagrams recorded during the tests. A description of the test bench and the measuring equipment used is provided. It was found that, within the investigated range of partial loads, supplying gas to the cylinder during the compression stroke allows the cycle indicator work to be increased
by 5–7%. It is noted that when gas is supplied during the intake stroke, the air filling of the cylinders is lower than at the same throttle valve position and gas supply during the compression stroke. It is shown that the observed decrease in air flow is due to a reduction in cylinder vacuum resulting from the supply of natural gas into the cylinder volume through the injector. The assumption that the observed higher combustion rate during gas injection in the compression stroke is due to the influence of the gas jet injected during the compression stroke on the turbulence parameters in the combustion chamber is substantiated.