Effect Of Ignition Timing And Injection Timing On Performance Of Natural Gas Engine

As the energy shortage and environment pollution become more and more stringent, the clean alternative fuel vehicles play an important role in the automobile industry. Among them, the natural gas becomes the preferred choice due to its abundant resources, clean combustion and low CO2 emission level. However, it features higher ignition temperature, lower flame propagation speed and lower power density. With the wide application of natural gas vehicles in China, requirements of low fuel consumption and emission level, the research on CNG engine's burning mechanism, optimization of construction and working process, and control technology of pollutants emission has attracted the most attention. This dissertation emphasizes on the above problems by optimize ignition timing and injection timing improve the performance of the dynamics,fuel economy and emissions for engines.Through changing ignition timing and injection timing, the experiment investigate the combustion and emissions on CA6SE1-21N heavy duty CNG (compressed natural gas)engine. The study showed that ignition timing control the combustion process efficiently, which also have a great influence on NOx. the injection time change the mixed laminated and exist optimum. for the optimum could obtained with the lowest emissions and without affect the power .The engine speeds from ESC 13-mod and other speeds were selected as experiment speeds. In condition of part loads, fixed speeds, the injection mass and throttle, change the ignition timing without change injection timing and change the injection timing without change the ignition timing. through above steps investigate the combustion boundary condition affect the performance of engines.The study showed that ignition timing have little effect on the power output. When the ignition timing attend to a certain extent, the engine begin to unsteady and the power have dropped. With the advanced of ignition timing, the start of combustion move ahead ,even reach at 15°CA; the combustion duration have change little; the maximum cylinder pressure and temperature increased and the crank angle corresponding to the maximum pressure have move ahead ,and the value of maximum cylinder pressure appeared the narrow-wide trnd.the NOx and CO emissions increased. For example ,in the1450 r/min,25%load,the NOx emissions increased about 85%,for the CH4 emissions ,when in the low speed, ignition timing have no effect on CH4 emissions,but for the middle and high speed,the CH4 emissions decreased ,even decreased about 100%. The ignition timing have little effect on the CO2 emissions.The injection timing have no effect on the engine power output,with the injection timing move backward, the start of combustion move ahead ; the combustion duration have change little; the combustion center also move forward the maximum cylinder pressure and temperature increased ,and the crank angle corresponding to the maximum pressure and temperature have move ahead ;the NOx emissions increased. And the CH4 emissions and CO emissions at first decreased and then increased up . The injection timing have little effect on the CO2 emissions.Through changing ignition timing and injection timing to investigate the combustion and emissions performance on lean burned CNG engine. For example, in the1450r/min,25%load, the ignition timing equivalent to 28°CA and the injection timing equivalent to 40°CA is the best .and the other work condition just like this. Different control strategies on the corresponding test results are compared. Based on optimize economy, the fuel consumption rate is 219.8 (g/kW.h), the BSNOx is 5.54(g/kW.h),the BSHC is 6.39(g/kW.h); Based on optimize the NOx emissions, the fuel consumption rate is 221.8 (g/kW.h), the BSNOx is 2.66(g/kW.h),the BSHC is 6.96(g/kW.h); Based on optimize the HC emissions, the fuel consumption rate is 221.17 (g/kW.h), the BSNOx is 13.80(g/kW.h),the BSHC is 5.34(g/kW.h).from the above all, through the combustion boundary condition to control should bring the NOx emissions of engine below the limit in Europe IV emission regulation.