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

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 equivalence 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. © 2022 Tianjin University. All rights reserved.