Development of Lean Burn High-Output Spark-Ignited Gas Engines : Experimental Study of Knocking in Lean Burn Gas Engines

Abstract

The study of knocking is key to increase the BMEP of lean burn gas engines. According to the results of FFT analysis of cylinder pressure in a 260 mm prototype engine, the peak frequency generally matches the calculated knocking frequency at a sound velocity of 900 m/s. The more severe the knocking intensity becomes, the higher the temperature of the combustion components becomes. The upper position of the liner wall and the side of the piston head show the highest rate of temperature increase. The knocking occurrence and its intensity are dependent on charge air temperature, O₂ concentration, ignition timing, or a combination of these. However, at an O₂ concentration above 13.5%, the influence of these parameters on kncoking is almost negligible. Therefore, increasing the excess air ratio is an effective way to increase engine output while suppressing the occurrence of knocking.