Flame Reconstructions in an Optical Diesel Engine Using Three-dimensional Computed Tomography Technology
A three-dimensional(3D)tomographic measurement system is set up around an optical diesel engine.In the system,two high-speed cameras and fiber-endoscope bundles(FEB)are used to capture flame projections in the combustion chamber from eight different orientations.Meanwhile,a special calibration plate is designed for calculating locations between the combustion chamber and FEBs.In addition,reconstruction errors induced by refractions are quantified using simulations.Finally,3D flame structures in the combustion chamber under different engine speeds are obtained using the 3D tomography technology.According to the comparison between 2D projections and 3D structures,with the increasing of engine speeds,the moment when the maximum flame area/volume and intensity are advanced.However,the moment calculated by 3D structures are delayed compared with that calculated by 3D projections because in the combustion process in the combustion chamber,flame propagate towards the direction of cylinder diameter as well as towards the direction of piston movement.Using 2D projections can only observe the propagation towards cylinder diameter.If utilizing 3D flame structures,the propagation towards the direction of the piston movement can also be obtained,which is helpful to analyze the combustion process and provide the guidance for improving the efficiency of engines.
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