Pilot ignited direct injection natural gas engines have been increasingly attractive owing to their advantages in thermal efficiency and emissions. For conventional pilot ignited direct injection natural gas engines, soot emissions have been considered as an urgent issue, which could be possibly resolved by the adoption of homogenous charge direct injection strategy. To prove this viewpoint, this paper experimentally studied the effects of homogenous charge direct injection strategy on the combustion, emissions, thermal efficiency and operation stability of a pilot ignited direct natural gas engine. The results indicated that at low load, the application of homogenous charge direct injection strategies has negative effects on NOx, CO and HC emissions; though soot emissions could be improved, the negative effects seem to be more predominant. At high load, though NOx and HC emissions are impaired with the application of homogenous charge direct injection strategies, CO and soot emissions could be substantially improved with optimized injection parameters. Thermal efficiency could be slightly improved at low load condition and could be greatly raised at high load condition. Additionally, the adoption of homogenous charge direct injection strategies would increase the instabilities of engine operation, however, this behavior is more significant at low load condition.

引燃直喷天然气发动机因其在热效率和排放方面的优势而越来越有吸引力。对于传统的引燃直喷天然气发动机，碳烟排放已被认为是一个紧迫的问题，可以通过采用均质充气直喷策略来解决。为证明这一观点，本文通过实验研究了均质直喷策略对引燃直燃天然气发动机燃烧、排放、热效率和运行稳定性的影响。结果表明，在低负荷下，采用均质直喷策略对NOx、CO和HC排放有负面影响；尽管可以改善烟尘排放，但负面影响似乎更为突出。在高负荷下，虽然 NOx 和 HC 排放会因应用均质充气直接喷射策略而受到影响，但通过优化喷射参数可以显着改善 CO 和碳烟排放。热效率在低负荷条件下可略有提高，在高负荷条件下可大幅度提高。此外，采用均质直喷策略会增加发动机运行的不稳定性，但这种行为在低负载条件下更为显着。低负荷时热效率可略有提高，高负荷时可大幅度提高。此外，采用均质直喷策略会增加发动机运行的不稳定性，但这种行为在低负载条件下更为显着。低负荷时热效率可略有提高，高负荷时可大幅度提高。此外，采用均质直喷策略会增加发动机运行的不稳定性，但这种行为在低负载条件下更为显着。