Laser and Phase Doppler Anemometry (LDA, PDA)

Contact: Dr Steve Begg

Phase Doppler Anemometry (PDA)


image of PDA instruments
PDA instrumentation setup on the optical Proteus

Laser Doppler Anemometry (LDA)

In-cylinder gas flows are invariably unsteady and highly turbulent. The features of these gas flows vary both temporally, throughout the engine cycle and spatially, within the volume of the chamber. As such, measurements of such flows require an instrument of high temporal resolution and which will not disturb the flows. LASER Doppler Anemometry is a single point measurement technique that can be utilised to measure the instantaneous velocity components of the gas flow at a single point of investigation. Mean flow and turbulence characteristics are then evaluated over many, consecutive engine cycles until a statistically significant data set is collected. Two coherent LASER beams are focused at a single point within the chamber. The interferometric pattern formed at their intersection is used to project a modulated light signal onto a photompuliplier detector by the use of suitable seeding particles added to the intake of the engine. The frequency of the scattered light signals are Doppler shifted and signal processing is used to determine the velocity component perpendicular to the fringe pattern. Second and third velocity components can be measured using additional LASER beam pairs of different wavelengths. The LDA can be operated in a backscattering mode in applications where the optical access is restricted to one window into the combustion chamber. The SHRL teams have developed different optical access scenarios to investigate the internal flow structures during motored engine operation. Such options include a glass cylinder liner, glass optical annulus, glass piston crown and mirror assembly and a spark plug mounted, indexed probe.

Selected Publications:

  • PDA Characterisation of dense diesel sprays using a common-rail injection system
    J. Lacoste, C. Crua, M.R. Heikal, D.A. Kennaird, M.R. Gold (2003) SAE paper no 2003-01-3085; Journal of Fuels and Lubricants.
  • Characteristics of diesel sprays at high temperatures and pressures
    J. Lacoste (2006) PhD Thesis, School of Engineering, University of Brighton, UK.