The passby noise is the net effect of the noise from the engine, tires, vehicle panels, the fan and the exhaust silencer. Exhaust noise is probably the loudest component of the passby noise in diesel trucks. The passby noise is measured when the vehicle is in transient condition according to the standards. A technique is developed to simulate the transient noise from the exhaust using 1-d simulation software AVL-Boost. It considers thermodynamics of combustion in the engine including the turbocharger, inertia of the engine and the vehicle. The technique helps in optimizing exhaust silencer, acceleration and in-cylinder parameters in transient conditions and the turbocharger fatigue.
A 165 kW 6-cylinder turbocharged and intercooled engine is simulated. The transient performance of the engine in the vehicle is validated by comparing the predicted results with the observed fuel consumption on road, time to accelerate to 60 km h−1 and the fluctuations in the turbocharger speed. The Linear Acoustics model of the silencer in conjunction with this transient model of the engine is used to predict the insertion loss of the silencer and the vehicle passby noise. In the first step, the silencer model is validated with test results by measuring the insertion loss in an actual vehicle. In the second step, the vehicle is modeled with the silencer by using load signals, fuelling and injection timing maps. The predicted noise is compared with the experimentally measured passby noise and the results are encouraging.
