在一台涡轮增压汽油机上改装低压冷却EGR(Exhaust Gas Recirculation)系统,通过台架试验研究了EGR率对发动机燃烧性能、泵气损失、排放和经济性的影响.为解决低速及小负荷无法引入EGR废气的问题验证了混合阀的作用。EGR废气的引入减缓...在一台涡轮增压汽油机上改装低压冷却EGR(Exhaust Gas Recirculation)系统,通过台架试验研究了EGR率对发动机燃烧性能、泵气损失、排放和经济性的影响.为解决低速及小负荷无法引入EGR废气的问题验证了混合阀的作用。EGR废气的引入减缓了燃烧速率,改变燃烧相位,降低了排气温度。随着EGR率的增加,油耗率呈先降低后上升的趋势。相对来说,在大负荷时EGR对降低油耗的效果更为明显。混合阀在1000~1600 r·min-1、负荷0.6~1.0 MPa时对油耗率降低有所帮助,但作用有限。展开更多
The grain refinement of superalloy IN718 under the action of low voltage pulsed magnetic field was investigated. The experimental results show that fine equiaxed grains are acquired under the action of low voltage pul...The grain refinement of superalloy IN718 under the action of low voltage pulsed magnetic field was investigated. The experimental results show that fine equiaxed grains are acquired under the action of low voltage pulsed magnetic field. The refinement effect of the pulsed magnetic field is affected by the melt cooling rate and superheating. The decrease of cooling rate and superheating enhance the refinement effect of the low voltage pulsed magnetic field. The magnetic force and the melt flow during solidification are modeled and simulated to reveal the grain refinement mechanism. It is considered that the melt convection caused by the pulsed magnetic field, as well as cooling rate and superheating contributes to the refinement of solidified grains.展开更多
Experimental investigations were conducted to study the film cooling performance in a low speed annular cascades using Thermochromic Liquid Crystal (TLC) technique. The test blade was placed in the second stage, where...Experimental investigations were conducted to study the film cooling performance in a low speed annular cascades using Thermochromic Liquid Crystal (TLC) technique. The test blade was placed in the second stage, where 18 blades were installed with chord length of 124.3 mm and height of 99 mm. A film hole with diameter of 4 mm, angled 28° to the tangential of the pressure surface in streamwise, was set in the middle span of the blade. The Reynolds number based on the outlet mainstream velocity and the blade chord length of the second stage varied from 1.52×105 to 2.00×105. All measurements were made with the blowing ratio varying from 0.3 to 3.0. Air and CO2 worked as coolant to achieve the coolant-to-mainstream density ratio of 1.03 and 1.57. The results show that the film coverage and cooling effectiveness scale up with the blowing ratio. Higher density ratio can generate larger film cooling coverage and effectiveness. The higher the Reynolds number, the larger the film coverage and cooling effectiveness.展开更多
文摘在一台涡轮增压汽油机上改装低压冷却EGR(Exhaust Gas Recirculation)系统,通过台架试验研究了EGR率对发动机燃烧性能、泵气损失、排放和经济性的影响.为解决低速及小负荷无法引入EGR废气的问题验证了混合阀的作用。EGR废气的引入减缓了燃烧速率,改变燃烧相位,降低了排气温度。随着EGR率的增加,油耗率呈先降低后上升的趋势。相对来说,在大负荷时EGR对降低油耗的效果更为明显。混合阀在1000~1600 r·min-1、负荷0.6~1.0 MPa时对油耗率降低有所帮助,但作用有限。
基金Project(2010CB631205)supported by the National Basic Research Program of ChinaProject(51034012)supported by the National Natural Science Foundation of China
文摘The grain refinement of superalloy IN718 under the action of low voltage pulsed magnetic field was investigated. The experimental results show that fine equiaxed grains are acquired under the action of low voltage pulsed magnetic field. The refinement effect of the pulsed magnetic field is affected by the melt cooling rate and superheating. The decrease of cooling rate and superheating enhance the refinement effect of the low voltage pulsed magnetic field. The magnetic force and the melt flow during solidification are modeled and simulated to reveal the grain refinement mechanism. It is considered that the melt convection caused by the pulsed magnetic field, as well as cooling rate and superheating contributes to the refinement of solidified grains.
基金the funding support from the construction of National 985 Program
文摘Experimental investigations were conducted to study the film cooling performance in a low speed annular cascades using Thermochromic Liquid Crystal (TLC) technique. The test blade was placed in the second stage, where 18 blades were installed with chord length of 124.3 mm and height of 99 mm. A film hole with diameter of 4 mm, angled 28° to the tangential of the pressure surface in streamwise, was set in the middle span of the blade. The Reynolds number based on the outlet mainstream velocity and the blade chord length of the second stage varied from 1.52×105 to 2.00×105. All measurements were made with the blowing ratio varying from 0.3 to 3.0. Air and CO2 worked as coolant to achieve the coolant-to-mainstream density ratio of 1.03 and 1.57. The results show that the film coverage and cooling effectiveness scale up with the blowing ratio. Higher density ratio can generate larger film cooling coverage and effectiveness. The higher the Reynolds number, the larger the film coverage and cooling effectiveness.