正庚烷均质压燃燃烧特性和排放特性的实验研究

为进一步了解高十六烷值燃料均质压燃的燃烧特性和排放特性，以正庚烷（n-heptane）为燃料，在一台改装的单缸直喷柴油机上进行正庚烷均质压燃台架实验．结果表明，正庚烷在均质压燃模式下表现出明显的双阶段着火特性；随着混合气浓度增大，缸内最大爆发压力和燃烧放热率峰值升高；随着发动机转速升高，燃烧放热率峰值先降低后升高，高转速的缸内最大爆发压力降低；当废气再循环率增大，缸内最大爆发压力和燃烧放热率峰值均降低，废气再循环使正庚烷均质压燃的运转工况范围向大负荷工况扩展，废气再循环率为75％正庚烷均质压燃运转的最高平均指示压力为0．41MPa．排放测试表明，正庚烷在均质压燃模式下的氮氧化物排放接近零，且可以实现无碳烟排放，但碳氢化合物和一氧化碳排放较高．

Experimental Study on the HCCI Combustion and Emission Characteristics of n-Heptane

Experimental study on homogeneous charge compression ignition (HCCI) of n-heptane was carried out on a modified direct-injection diesel engine with single-cylinder and four strokes to learn the HCCI combustion and emission characteristics of high cetane number fuel. The results show that the HCCI combustion of n heptane is characterized by a two-stage heat release process. The increase in compound concentration increases the maximum cylinder pressure and the maximum rate of heat release of combustion. With the increase of the engine speed, the maximum rate of heat release of combustion decreases firstly and then increases, the maximum cylinder pressure at high engine speed decreases. As for the condition of adopting exhaust gas recircula tion, the increase of the exhaust gas recirculation rate decreases the maximum cylinder pressure and the maximum rate of heat release of combustion. Moreover, exhaust gas recirculation transfers the HCCI operating region to the high load area. The maximum indicated mean effective pressure of HCCI engine can be extended to 0.41 MPa when exhaust gas recirculation rate is 75%. Emission results show that a nearly zero nitric oxide emission and no smoke emission can be obtained in HCCI operation. However, the unburned hydrocarbon and carbon monoxide emission is high.