Experimental Research On The Transmission Characteristics Of Combustion Noise

Along with rapid development of the internal combustion engine industry, thenoise pollution become increasingly serious, and the combustion noise plays animportant role in the overall noise of the internal combustion engine. In order tocontrol and reduce the combustion noise, grasp its transfer characteristic is one of theeffective methods. This paper focuses on the Weichai WP10-240high-speed dieselengines, conducts experimental study of the transmission characteristics ofcombustion noise. The main content of this paper is as followed:（1）The experiment of the surface noise of diesel engine is designed. The dieselengine’s surface noise on the exhaust pipe side is measured, according to themeasured sound pressure signal, the effective SPL and the total SPL of each measuredpoint are calculated, and the SPL cloud images are drawed. The position of the mainnoise sources is identified, preparing for the next experiment.（2）The experiment of the diesel engine’s single-cylinder noise is designed. Thesixth cylinder is chosen as the research object. Using the results of the experiment ofthe surface noise, the main noise sources of diesel engine are covered by stereotypeand sound insulation cotton targetedly, to eliminate interference noise. Theexperiment is in two steps: normal operating and motoring. The cylinder pressuresignal, vibration and noise signals in different conditions are measured.（3）The noise of motoring condition is assumed as the the mechanical noise ofthe normal operating condition,so the SPL of combustion noise can be separated byusing SPL’s synthesis and decomposition. The one-third octave band spectrum of theseparated combustion noise is analyzed, further, in different conditions, the transferfunction between cylinder pressure and combustion noise, and the transfer functionbetween the vibration and combustion noise are calculated.（4）According to the sound pressure signals collected from different locations,the influence of the transfer charcteristics of the combustion noise caused by differentdistance is analyzed. Changing the engine working condition, the influence of thetransfer charcteristics of the combustion noise caused by different load is alsosummarised. The results showed that: the surface noise of Weichai WP10-240high-speeddiesel engine is mainly concentrated in the air compressor, cylinder heads, body partsand oil pan; the amplitude of the transfer function between the combustion noise ofthe sixth cylinder and cylinder pressure is greater in low-frequency, smaller inhigh-frequency; the transfer characteristics of combustion noise does not change withthe cylinder pressure changes.