天然气-汽油双燃料发动机燃烧特性试验研究

Experimental Investigations into Combustion Characteristics of Natural Gas-Gasoline Dual-Fuel Engines

为了探究天然气-汽油双燃料燃烧模式在现代发动机上的适用性及潜在优势,基于一台增压直喷发动机结合进气道喷射天然气和缸内喷射汽油,开展了不同负荷、过量空气系数和天然气替代率下天然气-汽油双燃料燃烧特性试验研究。结果表明,低负荷固定转矩工况下,随着天然气质量流量增加,发动机最高燃烧压力提高,燃烧相位提前,循环变动降低,且在稀燃条件下尤为明显。中等负荷固定转矩工况下的燃烧特性变化规律与低负荷工况相似,而在高天然气替代率、稀燃条件下有效热效率随天然气质量流量增加明显提高。高负荷节气门全开工况下,尽管发动机最大转矩有所下降,但爆震起点和强度得到有效抑制,燃烧相位也明显改善,因此可以通过增压来弥补发动机功率不足的问题。

To investigate the feasibility and advantage of natural gas-gasoline dual-fuel combustion in modern engines,the combustion characteristics of natural gas-gasoline dual-fuel with different engine loads,excess air coefficients and substitute rates of natural gas were studied on a turbocharged direct-injection engine with port-injection of natural gas and direct-injection of gasoline.It was found that at low loads with constant torque output,peak pressure increases,combustion advances,and cyclic variation decreases with the increase of natural gas mass flow,especially at lean combustion conditions.The combustion at medium load conditions shows a similar trend to that at low loads,and with the increase of natural gas mass flow effective thermal efficiency is greatly improved at high natural gas substitute rates and lean combustion cases.At large load conditions with fully-opened throttle engine knock is effectively delayed,knocking intensity is significantly decreased and combustion is advanced even though there is some decrease in the maximum torque output.Since insufficient engine power output can be compensated by supercharging,the natural gas-gasoline dual-fuel engines,therefore,have a good application prospect.