Urea Selective Catalytic Reduction (urea SCR) system is widely used for diesel engine to reduce the emission of NO x by NH 3 which is provided by a hydrolysis of urea water. Concentration distribution of NH 3 in an exhaust pipe is an important factor for improvement of the SCR efficiency and prevention of NH 3 slip and urea deposit. Therefore, it is necessary to measure two-dimensional (2D) concentration of NH 3 in detail. The purpose of this study is to develop the real-time two cross-sectional measurements technology of NH 3 concentration using the computed tomography-tunable diode laser absorption spectroscopy (CT-TDLAS). Theoretical NH 3 concentration distribution which was reconstructed by CT agreed to CFD results and quadruple pipe's results showed good resolution by 14th order reconstruction. Therefore, this method has enough resolution and accuracy for measuring the concentration distribution of NH 3. And this method was employed in a bent pipe model demonstrated a urea SCR system. The experimental results of two cross-sectional 2D concentration of NH 3 show differences of the concentration distribution of NH 3 each cross-section and flow pattern like swirl flow. It was found that CT-TDLAS was an effective method to measure concentration distribution of NH 3 and observe characteristics of flow. In addition, observing flow pattern enable to validate CFD results, and it helps to improve efficiency of after treatment system.
A laser 2-focus velocimeter (L2F) was used for measurements of velocity, size and number density of droplets in diesel sprays injected into the atmosphere by using 8-hole injector nozzle. The diameter of the nozzle orifice was 0.112mm. The injection pressure was set at 65MPa. The droplets dispersion model which can estimate the number density by using the spray width and the droplet velocity was proposed. It was shown that the velocity of droplets at the spray center region was higher than the one at spray periphery region in the middle period of injection duration. The size of droplets at the spray center region was larger than the one at the spray periphery region. The number density of droplets was high at the region between the spray center and the spray periphery. The number density estimated by the droplets dispersion model was nearly same as the one evaluated by L2F measurement at the spray center region in the middle period of injection duration. It is understood that the number density was decided by the dispersion due to the changes of the spray width and the spray velocity at the center region in the middle period of injection duration.
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