Current studies of fan performance optimization mainly focus on two aspects： one is to improve the blade profile, and another is only to consider the influence of single impeller structural parameter on fan performan...Current studies of fan performance optimization mainly focus on two aspects： one is to improve the blade profile, and another is only to consider the influence of single impeller structural parameter on fan performance. However, there are few studies on the comprehensive effect of the key parameters such as blade number, exit stagger angle of blade and the impeller outlet width on the fan performance. The G4-73 backward centrifugal fan widely used in power plants is selected as the research object. Based on orthogonal design and BP neural network, a model for predicting the centrifugal fan performance parameters is established, and the maximum relative errors of the total pressure and efficiency are 0.974% and 0.333%, respectively. Multi-objective optimization of total pressure and efficiency of the fan is conducted with genetic algorithm, and the optimum combination of impeller structural parameters is proposed. The optimized parameters of blade number, exit stagger angle of blade and the impeller outlet width are seperately 14, 43.9~, and 21 cm. The experiments on centrifugal fan performance and noise are conducted before and after the installation of the new impeller The experimental results show that with the new impeller, the total pressure of fan increases significantly in total range of the flow rate, and the fan efficiency is improved when the relative flow is above 75%, also the high efficiency area is broadened. Additionally, in 65% -100% relative flow, the fan noise is reduced. Under the design operating condition, total pressure and efficiency of the fan are improved by 6.91% and 0.5%, respectively. This research sheds light on the considering of comprehensive effect of impeller structrual parameters on fan performance, and a new impeller can be designed to satisfy the engineering demand such as energy-saving, noise reduction or solving air pressure insufficiency for power plants.展开更多
Tangential leakage loss reduction has great significance on improving the performance of scroll compressors.In this study,the flow field of a scroll compressor working with CO_(2) was numerically investigated.The deve...Tangential leakage loss reduction has great significance on improving the performance of scroll compressors.In this study,the flow field of a scroll compressor working with CO_(2) was numerically investigated.The development characteristics of the tangential leakage flow in different working chambers were carried out,which was obtained by analyzing the field quantities distributions.The impacts of the radial clearances and sidewall roughness on the tangential leakage were also taken into consideration,in order to explore the feasible method of the flow control for the tangential leakage in scroll compressors.Results showed that the tangential leakage flow had various characteristics in the suction and compression chambers due to the different interactions between the tangential leakage flow and mainstream.Owing to little reverse pressure gradient,the tangential leakage flow maintained the typical jet form in the suction chambers.By contrast,the mixing of the tangential leakage flow and mainstream induced the passage vortex and secondary flows in the compression chamber.The secondary flow was the primary factor that results in the occurrence of localized high temperature region rather than the tangential leakage.With the increase of the radial clearance,the volumetric efficiency declined and the discharge temperature increased rapidly.In terms of flow control of the tangential leakage,the increase of sidewall roughness by 2μm could achieve the same effect as the decrease of the radial clearance by 4μm,while the volumetric efficiency increased by almost 5%and average discharge temperature decreased by 5K.展开更多
基金supported by Hebei Provincial Natural Science Foundation of China(Grant No.E2012502016)Fundamental Research Funds for the Central Universities,China(Grant No.12QN39)PhD Programs Foundation of Ministry of Education of China(Grant No.20110036110009)
文摘Current studies of fan performance optimization mainly focus on two aspects： one is to improve the blade profile, and another is only to consider the influence of single impeller structural parameter on fan performance. However, there are few studies on the comprehensive effect of the key parameters such as blade number, exit stagger angle of blade and the impeller outlet width on the fan performance. The G4-73 backward centrifugal fan widely used in power plants is selected as the research object. Based on orthogonal design and BP neural network, a model for predicting the centrifugal fan performance parameters is established, and the maximum relative errors of the total pressure and efficiency are 0.974% and 0.333%, respectively. Multi-objective optimization of total pressure and efficiency of the fan is conducted with genetic algorithm, and the optimum combination of impeller structural parameters is proposed. The optimized parameters of blade number, exit stagger angle of blade and the impeller outlet width are seperately 14, 43.9~, and 21 cm. The experiments on centrifugal fan performance and noise are conducted before and after the installation of the new impeller The experimental results show that with the new impeller, the total pressure of fan increases significantly in total range of the flow rate, and the fan efficiency is improved when the relative flow is above 75%, also the high efficiency area is broadened. Additionally, in 65% -100% relative flow, the fan noise is reduced. Under the design operating condition, total pressure and efficiency of the fan are improved by 6.91% and 0.5%, respectively. This research sheds light on the considering of comprehensive effect of impeller structrual parameters on fan performance, and a new impeller can be designed to satisfy the engineering demand such as energy-saving, noise reduction or solving air pressure insufficiency for power plants.
基金supported by the National Natural Science Foundation of China(Grant Nos.52006010 and 52006009)。
文摘Tangential leakage loss reduction has great significance on improving the performance of scroll compressors.In this study,the flow field of a scroll compressor working with CO_(2) was numerically investigated.The development characteristics of the tangential leakage flow in different working chambers were carried out,which was obtained by analyzing the field quantities distributions.The impacts of the radial clearances and sidewall roughness on the tangential leakage were also taken into consideration,in order to explore the feasible method of the flow control for the tangential leakage in scroll compressors.Results showed that the tangential leakage flow had various characteristics in the suction and compression chambers due to the different interactions between the tangential leakage flow and mainstream.Owing to little reverse pressure gradient,the tangential leakage flow maintained the typical jet form in the suction chambers.By contrast,the mixing of the tangential leakage flow and mainstream induced the passage vortex and secondary flows in the compression chamber.The secondary flow was the primary factor that results in the occurrence of localized high temperature region rather than the tangential leakage.With the increase of the radial clearance,the volumetric efficiency declined and the discharge temperature increased rapidly.In terms of flow control of the tangential leakage,the increase of sidewall roughness by 2μm could achieve the same effect as the decrease of the radial clearance by 4μm,while the volumetric efficiency increased by almost 5%and average discharge temperature decreased by 5K.
