Heat Transfer Measurements in a Motored Engine Using Speckle Interferometry

Gas-side temperature profile measurement in engines may provide valuable information regarding surface heat transfer as well as information on other fluid characteristics such as boundary layer thickness. Due to the typical cyclic variation of fluid variables in engines, profile measurement must be accomplished essentially instantaneously. This paper describes the use of speckle interferometry for acquiring such data. The advantages and disadvantages of the method will be briefly described with respect to current spectroscopic and other interferometric techniques.

The method has been applied to measure temperature profiles normal to the cylinder head in a motored two-cycle engine. The resulting temperature profiles for a variety of crank angles are presented. Estimates of thermal boundary layer thickness and surface heat transfer are also presented.