Effect of Pre-Chamber Structure Parameters on Lean-Burn Characteristics for a Gasoline Engine
Influence of different compression ratio(CR)on thermal efficiency based on ultra-lean gasoline combus-tion was studied on a single-cylinder research engine.The effects of the structural parameters of pre-chamber on combustion and emissions were also explored.The engine run at the conditions of the optimal fuel consumption,which was the speed of 2 750 r/min and the indicated mean effective pressure(IMEP)of 1.05 MPa.The excess air coefficient(φa)in the test was controlled by adjusting the air intake quantity and the cyclic fuel injection quantity.The research results show that,when the CR increases from 12.48 to 16.40,the indicated thermal efficiency(ITE)corresponding to the same φa takes an increasing trend,and meanwhile the φa of the optimal ITE also increases.When the CR is 12.48,the φa of the peak ITE is 1.8,and the ITE is 47.1％.When the CR is increased to 16.40,the φa corresponding to the peak ITE rises to 2.8,and the corresponding ITE rises to 50.1％.In addition,the com-parative study on the effect of the pre-chamber structural parameters on combustion shows that,the structural de-sign of the straight hole with 120° jet cone angle and 6.8 mm2 nozzle area can improve the combustion rate more ef-fectively,which is conducive to the suppression of knock combustion.It is indicated that a better combustion sta-bility and lower unburned hydrocarbon(UHC),CO,NOx and emissions can be achieved when using the ultra-lean combustion technology.
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