Study On HCCI Combustion Of Natural Gas Engine Based On Intake Air Temperature Heating

HCCI combustion integrates the advantages of SI and CI.It is a clean and efficient combustion to reduce NOx and particulate emissions while maintaining high combustion thermal efficiency.Natural gas has a low price,high octane number and is easy to form homogeneous mixture,but its high spontaneous combustion point makes it difficult to be compressed,which limits its application in HCCI combustion.This paper adopts the heat management method of intake air heating to realize the HCCI combustion mode of natural gas engine,refits the ZR180 single cylinder machine,and installs the natural gas supply system,electronic control system and cooling system,and completes the construction and debugging of the test bench.The influence of intake air temperature and excess air ratio on the combustion mode of HCCI of natural gas engine was investigated by experiment.Its main conclusions are as follows:With the increase of intake air temperature,HCCI combustion model of the maximum cylinder pressure,maximum rate of pressure rise,maximum heat release rate is on the rise,the maximum temperature in cylinder is on the decline,the corresponding crank Angle have also been moved forward,which affected the maximum pressure rise rate,inlet temperature increased from 180 degrees to 230 degrees Celsius in the process of pressure increase rate increased by 57.2%.With the increase of excess air ratio,the starting point and the center of mass of combustion both move forward,and the delay and main combustion periods are shortened.With the increase of intake air temperature,the average indicated pressure and torque of HCCI combustion mode of the engine both showed a downward trend,and the thermal efficiency also decreased significantly.The maximum thermal efficienc y is 34% when the intake air temperature is 180?.With the increase of intake air temperature,the average indicated pressure cycle change of HCCI combustion mode shows an upward trend,but the average indicated pressure cycle change keeps within 10%,and the inlet temperature has a great influence on the cycle change.With the increase of excess air ratio of engine cylinder pressure,heat release rate of HCCI combustion mode,pressure rise rate and temperature in cylinder is a downward trend,the maximum value of the crank shaft Angle have also been back,but they fall at a speed of each are not identical,which affected the maximum pressure rise rate,excess air ratio increased from 2.2 to 3.2 in the process of pressure increase rate fell by 43.4%.With the increase of excess air ratio,both the starting point and the center of mass of combustion appear to lag.The main reason is that the excess air ratio increases,the mixture in the cylinder becomes thinner,the combustion speed slows down,and the combustion phase lags.With the increase of excess air ratio,the engine HCCI combustion mode torque shows a downward trend,thermal efficiency shows an upward trend.At 1000r/min,when the excess air ratio is 2.6,the maximum thermal efficiency is 24.77%;At 1600r/min,when the excess air coefficient is 3,the maximum thermal efficiency is 31.55%.A thinner mixture is beneficial to the thermal efficiency of the engine.With the increase of excess air ratio,the average indicated pressure circulation change of engine HCCI combustion mode showed a downward trend,and the loss of the mean indicated pressure circulation change kept within a small range,and the influence of excess air ratio on circulation change was not obvious.