Nonintrusive and Multidimensional Optical Diagnostics and Their Applications in the Study of Thermal-Fluid Systems

Abstract

Nonintrusive measurements are highly desirable in the study of modern thermal-fluid systems. One of the key bottlenecks of studying such systems stems from the experimental difficulty of resolving the governing processes with the necessary temporal and spatial resolution. The research and development of modern power and energy systems (e.g., aero-propulsion engine) require understanding such processes under extreme conditions, such as sub-millisecond time resolution, sub-millimeter spatial resolution, high temperature and pressure, and multiphase flows. Traditional experimental techniques are no longer capable of meeting all these requirements. Therefore, this paper discusses nonintrusive laser diagnostics and their prospective of meeting these challenges. Using laser beams as probes and being nonintrusive, laser diagnostics can be applied to any harsh environments, at least theoretically. This paper specifically focuses on the recent work from the author's group to apply tomographic laser techniques to obtain multidimensional measurements in thermal-fluid systems. Examples include two-dimensional imaging of temperature fields at 50 kHz, and three-dimensional measurements of combustion parameters using emission spectroscopy at multi-kilohertz. Lastly, as an example, this paper discusses our ongoing efforts of applying advanced laser diagnostics for the study of thermal management of batteries in a hybrid vehicle.