内嵌换热面多孔介质燃烧与传热研究

发布时间：2018-03-17 17:17

本文选题：内嵌换热面　切入点：双层多孔介质　出处：《浙江大学》2017年硕士论文　论文类型：学位论文

【摘要】：多孔介质燃烧技术作为一种高效、清洁能源利用方式,具有燃烧速率高,负荷调节范围宽、污染物排放量低等优点。本文通过试验和模拟相结合的手段,对内嵌换热面双层多孔介质中的气体燃烧特性和换热面传热机理进行了研究,为内嵌受热面多孔介质燃烧装置的设计运行提供指导。主要的研究内容如下:(1)试验研究可燃气体在具有内嵌换热面泡沫型多孔介质中的燃烧、传热特性。搭建多孔介质燃烧热态试验系统,将换热面内嵌布置于双层泡沫型多孔介质下游碳化硅泡沫陶瓷中,试验研究甲烷/空气预混气体在其中的温度分布、稳燃范围、燃烧产物排放特性,并分析了燃烧器热效率和换热面在多孔介质内的传热过程。结果表明,在泡沫型多孔介质燃烧系统中内嵌换热面后燃烧器温度水平降低,仍具有较宽的稳燃范围;相较于无内嵌换热面情况,燃烧器出口 NOx排放量下降,试验工况范围内低于35mg/m3;燃烧器热效率随入口气流速度下降并保持在60%～80%范围内;换热管外壁与多孔介质气固两相的传热相较于传统的气流横向冲刷管束,平均传热系数增幅逾150%;基于MATLAB软件拟合得到内嵌换热面传热系数半经验公式,公式计算值与试验值误差低于10%。(2)试验研究不同换热面布置对于内嵌换热面多孔介质燃烧器性能的影响。结果表明:内嵌换热面多孔介质燃烧器CO排放量随着横、纵向管间距的升高均降低,为降低CO排放,在实际设计内嵌换热面时,应尽量避免换热面过于密集的布置方式;不同横纵向管间距下,氮氧化物排放量均低于20mg/m3。(3)以CFD商业软件FLUENT6.3为平台,数值模拟甲烷、空气预混气体在内嵌换热面双层多孔介质中的燃烧、传热,重点分析了换热面与多孔介质间的传热机理。结果显示:模型可以较好的预测甲烷、空气预混气体在内嵌换热面双层多孔介质中燃烧特性,温度预测值与试验结果误差低于20%;三排换热面传热量随布置位置与气体反应区距离的增加依次降低;第二、三排换热面与多孔介质气固两相间的传热以高温固体辐射传热为主,辐射传热占总传热量的55.4%,第一排换热面以导热为主,达42.6%;燃烧器热效率随下游材料消光系数升高而降低。
[Abstract]:As a kind of efficient and clean energy utilization technology, porous media combustion technology has the advantages of high combustion rate, wide load regulation range and low pollutant emission. The combustion characteristics of gas and the heat transfer mechanism of heat transfer surface in bilayer porous media with embedded heat transfer surface are studied. The main research contents are as follows: 1) Experimental study on combustion of combustible gases in porous media with embedded heat transfer surface. Heat transfer characteristics. A heat transfer test system for combustion of porous media was set up. The heat transfer surface was embedded in silicon carbide foam ceramics downstream of bilayer porous media. The temperature distribution of methane / air premixed gas was studied and the combustion range was stabilized. The characteristics of combustion product emission are analyzed, and the heat transfer process of the burner and the heat transfer surface in porous media are analyzed. The results show that the temperature level of the burner decreases after the heat transfer surface is embedded in the foam porous medium combustion system. Compared with no intercalation surface, the NOx emission from the burner outlet decreases, and is lower than 35 mg / m ~ 3 under the test conditions, and the thermal efficiency of the burner decreases with the inlet flow velocity and remains within the range of 60% or 80%. The average heat transfer coefficient between the outer wall of the heat transfer tube and the gas-solid two-phase heat transfer in porous media is increased by more than 150, compared with that of the traditional air flow, and the semi-empirical formula of the heat transfer coefficient of the embedded heat transfer surface is obtained based on the fitting of the MATLAB software. The effect of different heat transfer surface arrangement on the performance of porous media burners with intercalation surface is studied. The results show that the CO emission from porous media burners with intercalated heat transfer surfaces is transversely. In order to reduce CO emission, the arrangement of heat transfer surface should be avoided when the heat exchange surface is designed in practice. Using CFD commercial software FLUENT6.3 as a platform, numerical simulation of combustion and heat transfer in a bilayer porous medium with a heat exchanger surface of methane and air premixed gases, The heat transfer mechanism between heat transfer surface and porous media is analyzed emphatically. The results show that the model can predict the combustion characteristics of methane and air premixed gas in a bilayer porous medium with heat transfer surface. The error between the temperature prediction value and the test results is less than 20. The heat transfer rate of the three rows of heat transfer surfaces decreases with the increase of the location of the arrangement and the distance between the gas reaction zone. Secondly, the heat transfer between the three rows of heat transfer surfaces and the gas-solid phase of porous media is dominated by high temperature solid radiation heat transfer. Radiation heat transfer accounts for 55.4% of the total heat transfer, and the first heat transfer surface is mainly heat conduction, reaching 42.6.The thermal efficiency of the burner decreases with the increase of the extinction coefficient of the downstream materials.
【学位授予单位】：浙江大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TQ038.1

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