Development of an active exhaust silencer for internal combustion engines using feedback control 1999-01-1844
A silencer to attenuate engine exhaust noise using active control methods has been developed. The device consists of an electrically driven valve, combined with a buffer volume, which is connected to the exhaust outlet. Using the mean flow through the valve and the pressure fluctuations in the volume, the valve regulates the flow in such a way that only the mean flow passes through the exhaust outlet. The fluctuations of the flow are temporally buffered in the volume.
To carry out optimization and validation experiments, a cold engine simulator has been developed. This device generates realistic exhaust noise as well as the matching gas flow using compressed air. The simulator allows quick and reliable acoustic and fluid dynamic experiments on exhaust prototypes.
The silencer is developed using electrical equivalent circuits, wherein at first instance a feedforward control is applied. The silencer has been built and the transfer function between electrical motor current of the valve and resulting acoustic pressure is measured. Based on these measurements, the feedback controller is developed and tested.
The active silencer is capable to reduce the exhaust noise with 13 dBA using feedforward and 16 dBA using feedback control, with a back pressure of 10 kPa to the engine.