Pressure drops and heat transfer over staggered pin fin heat sinks with top bypass flow were experimentally evaluated. The authors considered liquid-cooling applications because there were few data available comparing...Pressure drops and heat transfer over staggered pin fin heat sinks with top bypass flow were experimentally evaluated. The authors considered liquid-cooling applications because there were few data available comparing to air-cooling applications. Empirical equations to predict heat transfer on the endwall were developed by obtaining experimental data on the copper base plate with acrylic pins. A new model for predicting pressure drops and heat transfer over staggered pin fin heat sinks with top bypass flow based on mass, momentum, and energy conservation within the two control volumes is proposed. The first control volume in the model is located within the finned area, and the second is located in the gap between the tip of the pins and the flow channel. This model combines two conditions according to the boundary-layer thickness. A comparison between experimental and calculated results revealed that dimensionless pressure drops and the Nusselt number could be predicted within 30% error for the former and 50% error for the latter.展开更多
In order to get a high flowrate gas-gas injector and its design methodology, the combustion flow field of a typical shear-coaxial injector was analyzed firstly. The dimensional analysis was applied in the phenomenon o...In order to get a high flowrate gas-gas injector and its design methodology, the combustion flow field of a typical shear-coaxial injector was analyzed firstly. The dimensional analysis was applied in the phenomenon of gas-gas combustion, and design parameter optimization and a structure improvement were also carded out. A high flowrate single-element injector with high 1-12/O2 momentum ratio and tapered 02 post tip was obtained and validated by both numerical and experimental studies. This high flowrate injector has simple construction and it can effectively enhance the mixing, decrease the combustion completion length and also has a benign heat environment. Furthermore, based on the study of the single-element injector, numerical optimization and validation experiments were conducted successively on a multi-element injector equipped with high flowrate injection elements. The multi-element injector with the high flowrate elements started up and shut down smoothly, and operated steadily without any stability aids. In the combustor designed with nominal parameters, this injection element can obtain high combustion efficiency with a flowrate of 3.7 times that of SSME main injector element and shows a benign chamber wall heat compatibility. This injector design and the design methodology can become a reference for the design of other types of injectors for liquid rocket engines.展开更多
High inlet solid loading is one of the most important features of cyclone separators in high density circulating fluidized beds （CFB）. In this work, the effect of high solid loading on pressure drop in a reverse-flo...High inlet solid loading is one of the most important features of cyclone separators in high density circulating fluidized beds （CFB）. In this work, the effect of high solid loading on pressure drop in a reverse-flow cyclone was experimentally studied. The particles used were sand and 2zAl203. Art extended range of inlet solid loadings （M）, up to 30 kg of solids/kg of air was tested at different inlet air velocities （Vin=16~24 m/s）, well beyond the solid loading range reported before. The experiments showed that, in the tested range of solid loadings, the cyclone pressure drop decreased dramatically with increasing solid loading when M〈7.5 kg/kg and then almost remained constant. A new semi-empirical model for predicting cyclone pressure drop was also developed. The calculated and experimental results showed good agreement for particle free flow and particle laden flow.展开更多
文摘Pressure drops and heat transfer over staggered pin fin heat sinks with top bypass flow were experimentally evaluated. The authors considered liquid-cooling applications because there were few data available comparing to air-cooling applications. Empirical equations to predict heat transfer on the endwall were developed by obtaining experimental data on the copper base plate with acrylic pins. A new model for predicting pressure drops and heat transfer over staggered pin fin heat sinks with top bypass flow based on mass, momentum, and energy conservation within the two control volumes is proposed. The first control volume in the model is located within the finned area, and the second is located in the gap between the tip of the pins and the flow channel. This model combines two conditions according to the boundary-layer thickness. A comparison between experimental and calculated results revealed that dimensionless pressure drops and the Nusselt number could be predicted within 30% error for the former and 50% error for the latter.
文摘In order to get a high flowrate gas-gas injector and its design methodology, the combustion flow field of a typical shear-coaxial injector was analyzed firstly. The dimensional analysis was applied in the phenomenon of gas-gas combustion, and design parameter optimization and a structure improvement were also carded out. A high flowrate single-element injector with high 1-12/O2 momentum ratio and tapered 02 post tip was obtained and validated by both numerical and experimental studies. This high flowrate injector has simple construction and it can effectively enhance the mixing, decrease the combustion completion length and also has a benign heat environment. Furthermore, based on the study of the single-element injector, numerical optimization and validation experiments were conducted successively on a multi-element injector equipped with high flowrate injection elements. The multi-element injector with the high flowrate elements started up and shut down smoothly, and operated steadily without any stability aids. In the combustor designed with nominal parameters, this injection element can obtain high combustion efficiency with a flowrate of 3.7 times that of SSME main injector element and shows a benign chamber wall heat compatibility. This injector design and the design methodology can become a reference for the design of other types of injectors for liquid rocket engines.
基金supported by National High-tech Research and Development Program of China under Grant No.2006AA05A103
文摘High inlet solid loading is one of the most important features of cyclone separators in high density circulating fluidized beds （CFB）. In this work, the effect of high solid loading on pressure drop in a reverse-flow cyclone was experimentally studied. The particles used were sand and 2zAl203. Art extended range of inlet solid loadings （M）, up to 30 kg of solids/kg of air was tested at different inlet air velocities （Vin=16~24 m/s）, well beyond the solid loading range reported before. The experiments showed that, in the tested range of solid loadings, the cyclone pressure drop decreased dramatically with increasing solid loading when M〈7.5 kg/kg and then almost remained constant. A new semi-empirical model for predicting cyclone pressure drop was also developed. The calculated and experimental results showed good agreement for particle free flow and particle laden flow.
