四气门汽油机低速低负荷燃烧过程的试验研究

Experimental study on combustion process in four-valve gasoline engine at low speed and light load

在发动机试验台上,用CB-466燃烧分析仪对四气门汽油机低速低负荷燃烧压力循环变动进行了试验研究。试验结果表明,转速不变时,随着负荷的增加,指示热效率逐渐增加,达到最大值后又逐渐减小,最高燃烧压力及其标准偏差和平均指示压力逐渐增加,最高燃烧压力循环变动率和平均指示压力循环变动率则随之减小;中等负荷与小负荷相比,最高燃烧压力循环变动率减少了28.3%,平均指示压力循环变动率减少了47.6%。在负荷不变的条件下,随着转速的增加,指示热效率逐渐增加,低转速时的指示热效率仅为中等转速时的指示热效率的57.4%,最高燃烧压力随之减小,最高燃烧压力循环变动率、平均指示压力及其标准偏差和平均指示压力循环变动率逐渐增加。平均指示压力循环变动率与最高燃烧压力循环变动率相比较小,平均指示压力循环变动率仅为最高燃烧压力循环变动率的37.1%。

The cyclic variation of the combustion pressure in the cylinder of a four-valve gasoline engine was analyzed at low speed and light load with the CB-466 combustion analyzer on the engine test-bed. At the same engine speed, the indicated thermal efficiency increased gradually with the increase of load and then decreased gradually after it reached the max. The combustion peak pressure, the standard deviation of the combustion peak pressure and the indicated mean effective pressure increased gradually with the increase of load at the same engine speed, the coefficient of cyclic variation of the combustion peak pressure and the coefficient of cyclic variation of the indicated mean effective pressure decreased with the increase of load. The coefficient of cyclic variation of the combustion peak pressure at medium load decreased by 28.3% compared with that at light load, and the coefficient of cyclic variation of the indicated mean effective pressure at medium load decreased by 47. 6% compared with that at light load. At the same load, the indicated thermal efficiency increased gradually with the increase of engine speed and the indicated thermal efficiency at low engine speed was only 37.1% of the indicated thermal efficiency at medium engine speed, the combustion peak pressure decreased with the increase of engine speed, and the coefficient of cyclic variation of the combustion peak pressure, the indicated mean effective pressure, the standard deviation of the indicated mean effective pressure and the coefficient of cyclic variation of the indicated mean effective pressure increased with the increase of engine speed. The coefficient of cyclic variation of the indicated mean effective pressure was smaller than the coefficient of cyclic variation of the combustion peak pressure, and the coefficient of cyclic variation of the indicated mean effective pressure was only 37. 1% of the coefficient of cyclic variation of the combustion peak pressure.