Abstract
In this paper, the quantitative schlieren method is extended to measure the concentration field of an injected gaseous fuel along several planes perpendicular to the jet axis. Background Oriented Schlieren (BOS) is used as a quantitative flow field concentration measurement based on the deflection made by features in the background pattern. The flow field which is located between the camera and the background pattern changes the intensity value of the background points in the transfer medium. The optical flow algorithm, which is used to measure the deflection vectors in the background due to the change in index of refraction, is modified to consider the change in intensity of the background image due to the flow field. Optical tomography is used as a tool to extract the index of refraction of the gaseous field. Mole fraction values at different planes perpendicular to the jet axis are obtained and displayed.
Highlights
The limitations of world’s fossil fuel supply and the ever increasing stringent pollution policies have brought an extensive research focus on alternative fuels
Since the near nozzle air fuel mixture is the important parameter for improved combustion and to avoid self sustained oscillation, this paper studied near nozzle flow region at a Reynolds number much less than 160
A similar imaginary setup excluding the volumetric data was used to capture the background image in order to simulate the background image without flow. These pair of images with and without the known volumetric density field were used as inputs to optical flow and tomography algorithms in order to calculate the index of refraction
Summary
The limitations of world’s fossil fuel supply and the ever increasing stringent pollution policies have brought an extensive research focus on alternative fuels. The most commonly used optical gas flow visualization techniques for measuring density (concentration) distribution use the basic principles of electron beam fluorescent images, scattered light images or light deflection [3, 4]. On the other hand, is a method that uses the deflection of light due to the change in field density to visualize the density gradients in gas flow [5]. It is most commonly used for qualitative investigations.
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