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高温空气燃烧系统中陶瓷蓄热体传热特性分析研究 总被引:15,自引:0,他引:15
针对小球、圆孔、方格孔、三角孔和正六边形孔蜂窝体等不同几何结构下的陶瓷蓄热体对高温空气燃烧系统的非稳态交替加热和冷却的传热过程的影响进行了理论分析,得出了正方形蜂窝体具有最佳的比表面积和开孔率的结论。建立了陶瓷蓄热体和气体的温度变化微分方程和数值计算的离散方程,并选取实例进行了数值计算,得出了温度变化和传热变化的特性曲线,其与实验测试结果变化规律基本一致。研究结果可以为高温空气燃烧过程中合理有效地控制蓄热体中交替换热过程提供理论依据。 相似文献
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介绍了高温空气燃烧过程中蜂窝陶瓷蓄热体的工作原理和损毁原因,采用代数雷诺应力模型和修正的速度-压力耦合算法SIMPLEC,耦合蓄热体内流体的流动和换热过程,运用有限元分析方法,对蜂窝陶瓷蓄热体格孔壁面上的应力变化规律进行数值研究,并根据计算结果对操作参数进行了改进。结果表明,频繁的蓄热和释热过程变换,使得蓄热体格孔壁面交替地受到拉应力和挤压应力的作用。流体的流速越大,应力变化越大;换向时间越短,应力交替作用的影响越大。适当地调低烧嘴负荷,延长四通阀的换向时间,有利于提高蓄热体的使用寿命,计算结果为蓄热体结构设计和操作参数的优化提供了依据。 相似文献
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蜂窝蓄热体对于改善空气燃烧过程,降低NOx起着至关重要的作用。本文通过Pointwise和Fluent软件建立了蜂窝蓄热体三维数值模型,从不同的换向时间、孔型、边长、材料的角度对比了蜂窝蓄热体的换热特性,并对实际工作中节能效率进行了理论计算。结果显示,当换向时间从15s增长到45s时,正方形蓄热体的温度效率从78.5%降低到63.1%。当边长、壁厚相同时,圆形蓄热体的温度效率最高,压降也最大;六边形蓄热体的温度效率最低,但压降最小。总结发现,孔隙率的减小可以有效的提高温度效率,但是同时会增大流动的压力损失。在实际应用中可据此选择合适的孔隙率。同时得到,在实际运行中,当a=2mm时,圆形蓄热体的节能效率最高(26.9%),六边形节能效率最低(24.4%)。 相似文献
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叙述了蜂窝体蓄热式燃烧技术的工作原理,并对其优势进行阐述。针对目前应用最广的18t熔铝炉(以天然气为燃料),建立蜂窝体蓄热室的设计模型,推导出相应的计算公式。通过工程实例证实模型和公式的正确性,为蜂窝体熔铝炉的设计与研究提供理论基础。 相似文献
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Honeycomb heat regenerators do not only reduce the fuel consumption in a high temperature air combustion (HiTAC) burning system but also provide the necessary high temperature of combustion air. A two-dimensional simulation model was developed to numerically determine the dynamic temperature and velocity profiles of gases and solid heat-storing materials in a composite material honeycomb regenerator. Consequently, the energy storage and the pressure drop are calculated and the thermal performance of honeycomb heat regenerator is evaluated at different switching times and loading. The model takes into account the thermal conductivity parallel and perpendicular to flow direction of solid and flowing gases. It considers the variation of all thermal properties of solid material and gases with temperature. Moreover, the radiation from combustion flue gases to the storage materials was considered in the analysis. The results are presented in a non-dimensional form in order to be a design tool as well. These analyses were applied on a regenerator made of two layers of ceramic materials, one is pure alumina and other is cordierite. This regenerator is contained in a 100 kW twin-type regenerative-burning system used for HiTAC. The effectiveness and the energy recovery rate were 88% and 72% respectively at nominal operating range of the regenerator and the pressure drop across the twin regenerator system was 1.16 kPa. The periodic steady state condition is reached after about 11 min and it takes only 2 min of operation until the temperature of combustion air remains above the self-ignition temperature that is required for HiTAC. Furthermore, these mathematical analyses show good agreement with experiments made on the same regenerator. In the experiments, the dynamic behavior of the heat regenerator operation was considered in order to compensate measurement readings for this effect. 相似文献