Abstract:

The pre-chamber ignition system can enhance the lean mixture combustion， which will then improve the thermal efficiency significantly. Based on a self-developed active pre-chamber and its fuel supply system， the effect of premixed gas injection pressure and fuel ratio on combustion characteristics at the lean boundary of an engine with a compression ratio of 16 is respectively investigated. The experimental results show that among the three kinds of premixed gas injection pressure of 0.19，0.14 and 0.09 MPa， the indicated mean effective pressure is the highest， and the ignition delay time and combustion duration are the lowest at the injection pressure of 0.09 MPa， with the most stable combustion. When the proportion of premixed gas fuel increases from 0.54% to 2.69% gradually， the engine's indicated mean effective pressure （IMEP） increases first， and then decreases， reaching its maximum at a ratio of 1.61% when the combustion is most stable and both the ignition delay period and combustion duration are the shortest. The active pre-chamber can realize the stable combustion with a λ of 1.8. Indicated thermal efficiency increases from 32.9% to 39.4%， a relatively increase of 19.8% compared with that of spark plug ignition.

Key words: engine, active pre-chamber, fuel control parameters, lean burn characteristics