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Zhao D.-F.,Tianjin Chengjian University | Liu F.-G.,Tianjin Chengjian University | You X.-Y.,Tianjin University | Zhang R.,Tianjin Chengjian University | And 2 more authors.
Energy Conversion and Management | Year: 2015

A premixed cylindrical burner is numerically and experimentally investigated to realize low pollutant emission. The geometrical parameters of nozzle exit position and nozzle diameter are optimized by using a validated Computational Fluid Dynamics model. The natural gas-air mixing in the mix chamber indicates that the uniformity of methane concentration increases with the increase of distance from ejector outlet. It is found that the nozzle exit position at -3.0 mm improves the overall performance of premixed cylindrical burner, when nozzle diameter is not less than 1.6 mm. The emission characteristics of nitrogen oxides and carbon monoxide are also examined by experimental approach. It is found that load factor has a great influence on nitrogen oxides and carbon monoxide emissions, but the effect is gradually disappeared when air coefficient is not less than 1.4. When nozzle exit position is -3.0 mm, nozzle diameter is not less than 1.6 mm and air coefficient is not less than 1.4, the emissions of nitrogen oxides and carbon monoxide are less than 20 ppm and 50 ppm, respectively. © 2015 Elsevier Ltd. Source


Liu F.-G.,Tianjin University | Liu F.-G.,Tianjin Institute of Urban Construction | You X.-Y.,Tianjin University | Wang Q.,China Quality Supervising Engineering and Test Center for Gas Appliances | Zhang R.,Tianjin Institute of Urban Construction
Energy Conversion and Management | Year: 2013

The ejector of low NOx burner based on the premixed combustion theory was designed in this study. The new designed burner focusing on the flowing and mixing processes of town gas ejector were optimized by CFD approach and validated by experiment. A comprehensive study was conducted to understand the effects of geometrical parameters on the static pressure of air and methane, and the mole fraction uniformity of methane at the outlet of ejector. The distribution chamber was applied to balance the pressure and improve the mixing process of methane and air in front of the fire hole. A distribution orifice plate with seven distribution orifices was introduced at the outlet of ejector to improve the flow organization. It was found that the nozzle exit position NXP = 5 mm and nozzle diameter d > 1.3 mm should be used to improve the flow organization and premixed combustion for the designed ejector. For the new designed burner, the concentration of NO emission is less than 40 ppm when α > 1.5, NXP = 5 mm and d > 1.3 mm. © 2013 Elsevier Ltd. All rights reserved. Source


Liu F.,Tianjin University | You X.,Tianjin University | Wang Q.,China Quality Supervising Engineering and Test Center for Gas Appliances | Zhang R.,Tianjin University
Advances in Intelligent and Soft Computing | Year: 2011

Nitrogen oxides (NOx) formed in gas instantaneous water heater combustion systems is a significant pollutant source in the domestic environment. Advances in the science of reactions, mathematical modeling, and increased performance of computer systems have made comprehensive modeling of NOx formation and destruction a valuable tool to provide insights and understanding of the NOx reaction processes in combustion systems. In this approach, the chemical combustion reactions are described by nine species and six steps. The predicted NO level is less than 30 ppm when diameter of round fire holes (d) is 0.6 or 0.7mm, and excess air ratio (α) is 1.3. Our results indicates that the vortex produced between a bunch of the round fire holes and another bunch of the round fire holes results in thermal agglomeration and the elevated value of NO. The areas of vortex regions are decreased with the increase of heat load. The lower temperature is produced in the vortex regions. The reduction of NO concentration under higher heat load is attributed to the lower temperature. © 2011 Springer-Verlag Berlin Heidelberg. Source


Liu F.-G.,Tianjin Chengjian University | Zhang R.,Tianjin Chengjian University | Liu W.-B.,China Quality Supervising Engineering and Test Center for Gas Appliances | Zhai J.,China Quality Supervising Engineering and Test Center for Gas Appliances | Zheng B.,Tianjin Chengjian University
Journal of Central South University | Year: 2014

An ejector of low NO x burner was designed for a gas instantaneous water heater in this work. The flowing and mixing process of the ejector was investigated by computational fluid dynamics (CFD) approach. A comprehensive study was conducted to understand the effects of the geometrical parameters on the static pressure of air and methane, and mole fraction uniformity of methane at the outlet of ejector. The distribution chamber was applied to balance the pressure and improve the mixing process of methane and air in front of the fire hole. A distribution orifice plate with seven distribution orifices was introduced at the outlet of the ejector to improve the flow organization. It is found that the nozzle exit position of 5 mm and nozzle diameter d >1.3 mm should be used to improve the flow organization and realize the well premixed combustion for this designed ejector. © 2014 Central South University Press and Springer-Verlag Berlin Heidelberg. Source


Liu F.-G.,Tianjin University | You X.-Y.,Tianjin University | Wang Q.,China Quality Supervising Engineering and Test Center for Gas Appliances | Liu W.-B.,China Quality Supervising Engineering and Test Center for Gas Appliances | Zhang R.,Tianjin University
Advanced Materials Research | Year: 2011

Carbon monoxide (CO) formed in gas instantaneous water heater combustion systems is a significant pollutant source in the domestic environment. With the advance of reaction science and computer performance, mathematical modeling is working for comprehensive simulation of CO formation to provide a valuable tool to study the insight and understanding of the CO reaction of combustion systems. In this approach, the chemical reactions of combustion are described by nine species and six steps. Numerical results show that the predicted CO level is less than 0.1% when diameter of round fire hole is 0.6 or 0.7mm and the excess air ratio is 1.3. The vortex appearing between two bunch of round fire holes results in a thermal agglomeration and O2 decrease. At this place, CO2 is decomposed into CO and O and CO and the reaction is mainly controlled by CO2 pyrolysis. At this time, the increase of excess air is helpful to reduce CO production. Our results indicate the excess air ratio should be kept above 1.3 to meet with the fifth class of NO emission in gas instantaneous water heater standard GB 6932-2001. © (2011) Trans Tech Publications, Switzerland. Source

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