Thesis-2015-Pai.pdf (34.69 MB)
Air induction noise investigation during turbocharger surge events in petrol engines
thesis
posted on 2015-11-16, 09:27 authored by Ajith V. PaiTurbocharging is used as a means to downsize petrol engines, thereby, producing more power for a
lower engine size, when compared with a naturally aspirated engine. Due to the presence of a throttle
valve in the intake system in petrol engines, flow is restricted at the outlet pipe of the compressor during
low load engine operation. For example, during transient tip out tip in maneuvers. Hence, there is a
chance of the turbocharger operating in near surge or surge conditions and, thus, generating surge noise.
This Thesis describes an experimental and simulation method to predict and measure the turbocharger
surge noise. Initially, experimental transient tip-in and tip-out maneuver was performed on a non
turbocharged car with a petrol engine. The measured noise level in the intake manifold, at a low
frequency of up to 1200 Hz, was analysed and was shown not to represent surge noise. Next, a one
dimensional simulation method was applied to simulate the noise of the engine and this demonstrated
an increase in the acoustic pressure level in the intake manifold during the tip in and tip out maneuver.
However, a surge noise pattern was not observed in the analysis of acoustic pressure signals in the
intake system using Short Time Fourier Transform (STFT). The simulation procedure was also used to
inform the design of an experimental rig to recreate the surge noise under laboratory conditions. An
experimental turbocharger noise rig, designed and built for this purpose, is explained in the Thesis.
Important component parts likely to be involved in the surge noise generation such as the intake system,
compressor, throttle body, compressor recirculation valve and measurement and control systems were
integrated into the test rig. Background noise contributions from the electric motor, AC mains,
supercharger pulley, throttle body, inverter fan, throttle body gearing and structural vibration of the
supporting structure were identified from the analysed frequency components of the signals from
surface microphone measurements taken at the intake system. This helped to clearly identify the surge
noise frequency components (3250 Hz) in the STFT analysis. The fundamental mechanism of noise
generation was identified using an analysis of the experimental results and a frequency calculation for
vortex shedding and the radial acoustic resonances. One of the main conclusions of the Thesis is that
the compressor recirculation valve (CRV) open or close position, the CRV delay time and the throttle
position are major contributing factors to the cause of the surge noise. Another major conclusion is that
the radial acoustic resonance may be a mechanism of surge noise generation. Finally, a passive solution
to reduce the surge noise is proposed. A pipe with cross ribs is designed as a passive solution using the
radial acoustic resonance calculation and the corresponding nodal patterns. This solution demonstrated
a measured intake system noise reduction of up to 10dB under compressor surge conditions.
Funding
Department of Aeronautical and Automotive Engineering, Loughborough University
History
School
- Aeronautical, Automotive, Chemical and Materials Engineering
Department
- Aeronautical and Automotive Engineering
Publisher
© Ajith Venkateswara PaiPublisher statement
This work is made available according to the conditions of the Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International (CC BY-NC-ND 4.0) licence. Full details of this licence are available at: https://creativecommons.org/licenses/by-nc-nd/4.0/Publication date
2015Notes
The open access file has had copyright material removed. A Doctoral Thesis. Submitted in partial fulfilment of the requirements for the award of Doctor of Philosophy of Loughborough University.A Doctoral Thesis. Submitted in partial fulfilment of the requirements for the award of Doctor of Philosophy of Loughborough University.Language
- en