Research On The Influence Of Spark Discharge To HCCI Combustion Process

HCCI is a new technology with advantages of low fuel consumption and low emissions. But the disadvantages of controlling combustion process difficulty and narrow operation range limit its uses in automotive industry. Normally, indirect controlling method of HCCI is not flexible and accurate enough. Now we have found out the spark ignition controlling method, which is a direct method used in conventional gasoline engine, can stabilize combustion process on the boundary of CAI and enlarge operation range of HCCI. But how to control combustion process accurately and enlarge operation range further more with this method, now there's no mature theory and technology.In this paper, one model is set up to calculate theoretic minimum ignition energy, which takes account of intake air temperature, intake air pressure, density of mixture, EGR rate et al. By calculating minimum ignition energy under different operating condition, we validate the possibility of flame propagation in HCCI combustion process. The calculation results show, flame propagation process might exist under HCCI operating condition. And increasing ignition energy can fulfill request of in-cylinder lower mixture temperature.In this paper, we developed a capacitive multi-pulse ignition system, which can ignite several times in one engine work cycle. Both pulses times and pulses intervals are changeable.Through tests, we investigate the quality of HCCI combustion with multi-pulse spark ignition, and the influence of ignition parameter to HCCI combustion process with spark ignition. Test results show: main process of HCCI combustion with multi-pulse spark ignition is compression combustion, but the prophase might be flame propagation combustion. Under CAI's steady working condition, spark has a little influence to combustion. Under the condition that CAI cannot work but HCCI with spark assistance can stably work, pulses times and pulses intervals can influence combustion. Under condition that CAI cannot work and HCCI with spark assistance is likely to misfire, more pulse times, less pulse interval, engine works more stable.