Development of an active exhaust silencer for internal combustion engines.

Profil Titel	Development of an active exhaust silencer for internal combustion engines.
Referenz	06 BE FLIW 0G64
Herkunftsland	Belgium
Kooperationsart	Angebot
Eintrag/Änderung	2006-09-14 / 2007-12-11
Status	Dieses Profil ist abgelaufen! Falls Sie denoch Interesse haben, kontaktieren Sie uns. (2008-03-31)

Kurzfassung

A Belgian university has developed an active exhaust silencer for internal combustion engines. The active exhaust system reduces noise up to 13dB, requires less space and consumes less energy than a fully passive exhaust system. The research group is looking for technical collaboration to further development of the silencer. In conjunction, a cold engine test rig as well as a design and modelling tool are offered for new silencer co-development projects.

Details

The active exhaust system consists of an electrically driven valve mounted in series with a buffer volume. Using the mean flow through the valve and the pressure fluctuation in the volume, the valve regulates the flow to the exhaust outlet such that only the mean flow passes through the exhaust outlet. The fluctuating flow is temporarily buffered in the volume. The exhaust system is capable of attenuating the exhaust sound by 13 dB (4 dBA), as measured on a cold engine test setup. The mean backpressure to the engine remains below 10 kPa. The electrical power consumption is only 5W. Supporting the development of the active silencer, electrical analogue models were developed for silencer design purposes. The engine acoustical characteristics, such as its acoustical impedance and source strength, have been included in the electrical models. The models were validated by experiments and the active silencer prototype has been constructed based on the simulation results. Also, a cold engine test rig is developed which generates realistic exhaust noise using compressed air. This test rig has similar characteristics as an operational engine. This has been demonstrated by comparative measurements. The test rig permits to develop new concepts of exhaust systems economically.
The prototype active silencer has been validated on the cold engine test rig. Different control strategies were experimented with, such as a fixed feed forward controller, an x-LMS adaptive feed forward controller and a feedback controller. For further development, collaboration with an industrial partner is necessary to assist for the next stage of development, which should result in an active silencer for an operational combustion engine. The research group has a well-established research experience in the field of noise and vibration engineering. Their activities are focused along three major lines of research: numerical modelling for acoustics and vibration, identification of linear and non-linear dynamic systems, and active noise and vibration control. The research group is looking for technical collaboration to further development of the silencer. In conjunction, a cold engine test rig as well as a design and modelling tool are offered for new silencer co-development projects.

Innovative Aspects:
The major innovations resulting from the research project are:
1) In contrast to the known active exhaust systems so far, this system is able to attenuate the exhaust noise without passive attenuation prior to the active silencer.
2) A design tool for the active system has been developed wherein the engine, the active silencer and the other peripheral devices are modelled in detail using electrical equivalent circuits.
3) A cold engine test setup was developed, which exhibits similar acoustical and fluid-dynamic properties as an operational engine using compressed air. The setup is suitable for acoustic and fluid-dynamic experiments with new concepts of exhaust systems using common materials and standard measurement equipment.

The main advantages of the newly developed active silencer are:
1) The silencer volume is smaller than the volume of a passive silencer with similar noise attenuation properties.
2) The active silencer is capable of reducing very low frequency noise at large exhaust gas volume velocities, which is particularly beneficial for large engines with low rotational velocity.
3) The efficiency of the engine will be improved, resulting in a reduction of fuel consumption.
4) Integration of sound design into the active silencer is possible, for example for engines with cylinder deactivation.