进气道喷射氢发动机燃烧及爆震特性试验研究

Experimental Investigations on Combustion and Knock Characteristics of Port Fuel Injection Hydrogen Engine

为探究进气道喷射(PFI)氢发动机燃烧特性,以一台四冲程PFI氢发动机为研究对象,开展了关键参数(点火时刻、当量比)对氢发动机燃烧及爆震特性影响的试验研究,其中点火时刻在-5°CA~-30°CA内变化,当量比在0.5~0.8内变化.结果表明,随着点火时刻从-5°CA提前到-30°CA,发动机做功能力逐渐降低,循环变动逐渐增大;将当量比从0.5提高到0.7时,发动机做功能力有所下降且循环变动增大,综合发动机做功能力和循环变动来看,-15°CA点火时刻发动机性能最优;根据统计学角度分析得知,从点火时刻-25°CA开始,随着点火时刻的推迟,平均爆震强度呈现先增大后降低的趋势;平均爆震强度随当量比的提高整体呈增大趋势,但其对当量比的敏感性与点火时刻密切关联,-15°CA~-20°CA点火时,增大当量比会使平均爆震强度明显增加;同时,点火时刻较为提前或推迟时爆震概率对当量比的敏感性较大,增大当量比会使爆震概率明显增加、爆震起始时刻提前.此外,在高当量比条件下,初期循环中一般强度爆震的累加作用会诱发超级爆震.

To explore the combustion and knock characteristics of a port fuel injection(PFI)hydrogen engine,this study investigates the effect of key parameters(ignition timing and equivalence ratio)on the combustion and knock characteristics of a four-stroke PFI hydrogen engine.In the experimental study,the ignition time varies from-5°CA to-30°CA and the equivalence ratio varies from 0.5 to 0.8.Results show that as the ignition time advances,the engine’s power gradually reduces,whereas the cycle’s variation gradually increases.When the equivalence ratio is increased from 0.5 to 0.7,the engine’s power reduces,whereas the cycle’s variation increases.From the perspective of comprehensive engine power and cycle variations,the engine performance is optimal when the ignition time is approximately-15°CA.The statistical analysis revealed that starting from an ignition time of-25°CA,with the ignition time delayed,the average knock intensity first increases and then decreases.Further,with increasing equivalence ratio,the average knock intensity increases;however,its sensitivity to the equivalence ratio is closely related to the ignition time.When the ignition time is between-15°CA and-20°CA,increasing the equivalence ratio will significantly increase the average knock intensity.Moreover,the sensitivity of the knock probability to the equiva-lence ratio is closely related to the ignition timing,i.e.,when the ignition time advances or delays,the sensitivity improves.Thus,increasing the equivalence ratio will significantly increase the knock probability and advance the knock onset time.In addition,at a high equivalence ratio,the cumulative effect of general intensity knock in the initial cycle will induce the occurrence of a super knock phenomenon.