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In-Cylinder Flow Visualisation by Particle Image Velocimetry (PIV)

Researchers: Dr. Y. Li, B. Leach

Supervisors: Prof. H. Zhao, Dr. T. Ma, Prof. N. Ladommatos

Sponsors: EPSRC, Ford Motor Company

PIV Principle

The velocity vectors are derived from sub-sections of the target area of the particle-seeded flow by measuring the movement of particles between two laser pulses:

1. A special CCD camera captures two images of laser pulses separated by Δt onto separated frames.
2. The images are divided into small subsections called inter-rogation areas (IA). The interrogation areas from each image frame, I₁ and I₂, are cross-correlated with each other, pixel by pixel.
3. The correlation produces a signal peak, identifying the common particle displacement, ΔX. An accurate measure of the displacement - and thus the velocity - is achieved with sub-pixel interpolation.

Experiments & Results

In-cylinder swirl flow

Evolution of tumble flow in a modern 4-valve cylinder engine

(Left) BDC (Right) 120 BTDC

(Left) 90 BTDC (Right) 60 BTDC

50 BTDC

Cycle variation of the tumble ratio and centre

Velocity fluctuation kinetic energy