Laser Doppler anemometer measurements of mean velocity and turbulence in internal combustion engines

Abstract

Because fluid motions inside an engine cylinder exert a strong influence on combustion and consequent engine performance, measurements of in-cylinder flow fields can be valuable input to the design of better internal-combustion engines. Laser Doppler anemometry provides a means of measuring the in-cylinder gas velocities in both motoring and firing engines. This paper reviews the state-of-the-art of LDA (laser Doppler anemometer) measurements in engine cylinders. Representative LDA systems and some of the practical problems encountered in their application to engines are described. In an engine, the inlet flow is highly three-dimensional with a very complicated in-cylinder flow. After the inlet flow stops, the fluid motions tend to become more organized; a precessing vortical flow is typically observed. Sample flow-field measurements are presented for some different engine types. Alternative data-reduction schemes and their identification of mean velocity and turbulence are discussed, along with examples of the same data reduced in different ways.Because fluid motions inside an engine cylinder exert a strong influence on combustion and consequent engine performance, measurements of in-cylinder flow fields can be valuable input to the design of better internal-combustion engines. Laser Doppler anemometry provides a means of measuring the in-cylinder gas velocities in both motoring and firing engines. This paper reviews the state-of-the-art of LDA (laser Doppler anemometer) measurements in engine cylinders. Representative LDA systems and some of the practical problems encountered in their application to engines are described. In an engine, the inlet flow is highly three-dimensional with a very complicated in-cylinder flow. After the inlet flow stops, the fluid motions tend to become more organized; a precessing vortical flow is typically observed. Sample flow-field measurements are presented for some different engine types. Alternative data-reduction schemes and their identification of mean velocity and turbulence are discussed, along with examples ...