Experimental Apparatus for the PIV Validation of Gas-Dynamic and CFD Engine Models

The single shot apparatus creates a pressure wave (compression or rarefaction) by releasing a pressure or vacuum from a blowdown cylinder. The wave is contrived to be representative of cylinder blowdown or the suction wave that emanates from an engine intake valve during induction. Generated waves may be fired into a quiescent pipe or system of pipes that represent the ducts found on an engine.

The most significant features that distinguish the new apparatus from any previous are that it uses a poppet valve to release the wave and that the apparatus is largely automatic, enabling the generation of a new wave every 15 seconds or so.

The particular version of the apparatus described here has been conceived to allow a low speed background flow to be maintained in the pipe system between waves. The purpose of this is to allow microscopic particles to be kept in suspension in the air to facilitate flow studies using Particle Image Velocimetry (PIV) or Laser Doppler Anemometry (LDA). Sample PIV results are presented to demonstrate the apparatus and illustrate the build up of a boundary layer in a pressure wave.