Abstract
Particle image velocimetry is used to study the motion of gas within a duct subject to the passage of a finite amplitude pressure wave. The wave is representative of the pressure waves found in the exhaust systems of internal combustion engines. Gas particles are accelerated from stationary to 150 m/s and then back to stationary in 8 ms. It is demonstrated that gas particles at the head of the wave travel at the same velocity across the duct cross section at a given point in time. Towards the tail of the wave viscous effects are plainly evident causing the flow profile to tend towards parabolic. However, the instantaneous mean particle velocity across the section is shown to match well with the velocity calculated from a corresponding measured pressure history using 1D gas dynamic theory. The measured pressure history at a point in the duct was acquired using a high speed pressure transducer of the type typically used for engine research in intake and exhaust systems. It is demonstrated that these are unable to follow the rapid changes in pressure accurately and that they are prone to resonate under certain circumstances.
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Abbreviations
- a :
-
Local acoustic velocity at a point on a pressure wave
- a o :
-
Acoustic velocity in undisturbed gas
- c :
-
Local propagation velocity of a point on a pressure wave
- p :
-
Static pressure at a point on a pressure wave
- p o :
-
Pressure of undisturbed gas
- u :
-
Gas particle velocity at a point on a pressure wave
- γ :
-
Ratio of specific heats
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Acknowledgements
The authors would like to acknowledge the advice provided by Dr. G. Hargrave and Professor N. Haliwell in specifying the PIV system, Optimum Power Technology for financing the program of research and providing matching funding to EPSRC for purchase of the PIV system under grant number GR/M92829/01.
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Thornhill, D., Currie, T., Fleck, R. et al. Particle image velocimetry investigation of a finite amplitude pressure wave. Exp Fluids 40, 400–404 (2006). https://doi.org/10.1007/s00348-005-0077-6
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DOI: https://doi.org/10.1007/s00348-005-0077-6