Measurement and Characterisation of Faults in the Intake System of a Turbocharged Engine Using a Directional Acoustic Probe

Engine intake system leaks are a primary reason behind unsatisfactory operational and emission characteristics of turbocharged engines. In faulty conditions, the intake mass flow sensed by the mass flow sensor does not reach the combustion chamber, resulting in a less than required air fuel mass ratio. This may result in increased emissions along with unsatisfactory performance of exhaust gas recirculation system. In the present work, an acoustic sniffer system has been developed which identifies the presence and location of leaks in the intake system. The acoustic sniffer system uses a directional acoustic probe which records acoustic signatures of the leaks and positively identifies their presence. The sound pressure level data obtained from the acoustic probe is converted into frequency domain by FFT. Frequencies corresponding to the leaks are then identified in different octave bands. Experimental work on a four stroke 4.3 litre diesel engine demonstrates that the sniffer could be used to identify and quantify the leaks in the engine system. The system performs satisfactorily on a variety of leaks created in the intake system. It has also been found that sound pressure levels and frequency bands corresponding to different leaks could be used to estimate the amount of gas leaked from the system. This acoustics based system provides a simple and yet reliable method for leak diagnosis in engine intake system.