Method to quantify and visualize abnormal combustion of a SI engine
With increased power density on gas engines, an increase in cylinder temperature deviation was observed. The combustion shows temperature variations from cylinder to cylinder. The differences can be caused by variations in the air/fuel ratio, in the homogeneity of the mixture, in the charge movement, in the wall temperatures, in the manufacturing tolerances, and the oil entry on valves and pistons, etc. All parameters lead to deviations from the optimal center of combustion and in burning efficiency of the fuel. In particular oil entry leads to abnormal combustion in single or multiple cylinders caused by selfignitions. Strong self-ignitions can express themselves by generating spontaneous cyclically unsteady combustionchamber temperatures. Further investigations with pressure sensors identified abnormal combustion with higher peak pressures sometimes combined with knocking. Nevertheless, these strong self-ignitions do not always appear but they are probably affected by the amount of oil entry into the cylinder. Self-ignition was found during normal combustion following a spark ignition, and also when a cylinder was not ignited by a spark at all. Self-ignition occurs with intensity levels related to the engine power. In extreme cases, they lead to a derating or shutdown of the engine by the monitoring system. A new procedure was developed to quantify the self-ignition. The electronic spark ignition was shut off in each cylinder, one by one and the cylinder pressure was measured by a quartz pressure sensor. Based on the cylinder pressure curves, the heat release per cycle was calculated by thermodynamic analysis. If the unfired cylinder starts with a combustion (depending on the amount of engine power) after a self-ignition, an accordingly statistically distributed number of visible combustions arises during the recorded working cycles. These combustion processes are different due to the amount of burnt fuel. The comparison of approx. 5 working cycles of multiple cylinders on the basis of the single burn functions is not revealing. The comparison of 100 working cycles is impossible. The newly introduced evaluation method presented here allows the quick detection of the number and the intensity of the abnormal combustions.
Hans-Bernhard Snuis
MWM GmbH,Germany
国际会议
上海
英文
1-10
2013-05-13（万方平台首次上网日期，不代表论文的发表时间）