All components of a turbocharger compressor are axisymmetric except for the spiral-shaped,gas-collecting overhung volute.In this paper,a novel experimental method to evaluate the impact of the volute's asymmetry o...All components of a turbocharger compressor are axisymmetric except for the spiral-shaped,gas-collecting overhung volute.In this paper,a novel experimental method to evaluate the impact of the volute's asymmetry on centrifugal compressor performance is proposed and applied to a high pressure-ratio turbocharger compressor.This method can isolate the impact of the volute's asymmetry on the compressor performance for the first time.Experiments prove the considerable impact of the volute's asymmetry on the compressor performance,especially the stability and efficiency.The impact of the volute's asymmetry on compressor stability correlates with rotational speed and thus with the pressure ratio,constricting the stable flow range by up to 47 percent and decreasing the maximum efficiency by 4.8 percent at the design speed.The results provide evidence to exploit the potential of intrinsic non-axisymmetric flow induced by asymmetric volute to improve the performance of turbocharger compressor with a high pressure ratio.展开更多
The effects of Reynolds number on the performance of a high pressure-ratio turbocharger compressor were investigated by both experiments and numerical simulation. The experimental results show that the pressure ratio ...The effects of Reynolds number on the performance of a high pressure-ratio turbocharger compressor were investigated by both experiments and numerical simulation. The experimental results show that the pressure ratio and the efficiency of the compressor respectively decrease by 7.9% and 6.9% when Reynolds number drops from 9.86×10 5 to 2.96×10 5 . The numerical simulation predicts a similar trend as the experimental results although it underestimates the deterioration of the performance under low Reynolds number conditions. According to simulation results, the boundary layer thickness increases at the inducer, which decreases the throat area and leads to smaller choke mass flow rate. The increments of the boundary thickness are relatively small at the rear part of the impeller. The boundary layer separation flow is severe. The interaction between boundary layer separation flows and leakage flows causes the high loss region at the rear part of the impeller passage under low Reynolds number condition.展开更多
目的:观察8周有氧运动干预对单纯性肥胖患者运动后收缩压恢复(PESBPR)、体成分以及运动能力的影响,并探讨PESBPR与体成分、运动能力的关系。方法:63名肥胖患者随机分为运动组(n=35)和对照组(n=28),运动组进行为期8周的有氧运动,对照组...目的:观察8周有氧运动干预对单纯性肥胖患者运动后收缩压恢复(PESBPR)、体成分以及运动能力的影响,并探讨PESBPR与体成分、运动能力的关系。方法:63名肥胖患者随机分为运动组(n=35)和对照组(n=28),运动组进行为期8周的有氧运动,对照组保持日常生活习惯。实验前、后双能X-线吸收仪(dual-energy X-ray absorptiometry,DXA)测定体成分,包括脂肪重量(fat mass,FM)、去脂体重(fat-free mass,FFM)和体脂百分比(percentage of body fat,BF%);利用症状限制性递增负荷运动实验测试PESBPR和运动能力,PESBPR定义为运动实验后第3min的收缩压与运动后第1min收缩压的比值(即第3min收缩压恢复比,rSBPR),运动能力包括最大耗氧量(VO2max)、最大功率(MP)和力竭时间(ET)。结果:偏相关分析显示,rSBPR与BF%正相关(r=0.412,P<0.01),与VO2max、MP和ET均呈负相关(分别为r=-0.475,P<0.01;r=-0.366,P<0.01;r=-0.308,P<0.01)。8周实验后,运动组体重(P<0.05)、BMI(P<0.05)、FM(P<0.01)、BF%(P<0.01)、安静SBP(P<0.05)、SBPmax(P<0.01)、rSBPR(P<0.05)和PESBPR延迟发生率(P<0.01)降低,VO2max(P<0.05)、最大功率(P<0.05)和力竭时间(P<0.01)升高;对照组各指标均无显著性变化(均为P>0.05)。运动组实验前、后rSBPR变化与BF%变化呈正相关(r=0.315,P<0.01),与VO2max的变化呈负相关(r=-0.338,P<0.01)。结论:1)rSBPR与BF%正相关,与运动能力负相关,rSBPR可能是肥胖患者可调控的心血管危险因素;2)8周有氧运动可显著改善肥胖患者体成分,提高有氧运动能力,下调rSBPR及PESBPR延迟发生率。展开更多
基金supported by the National Natural Science Foundation of China (Grant No. 50806040)
文摘All components of a turbocharger compressor are axisymmetric except for the spiral-shaped,gas-collecting overhung volute.In this paper,a novel experimental method to evaluate the impact of the volute's asymmetry on centrifugal compressor performance is proposed and applied to a high pressure-ratio turbocharger compressor.This method can isolate the impact of the volute's asymmetry on the compressor performance for the first time.Experiments prove the considerable impact of the volute's asymmetry on the compressor performance,especially the stability and efficiency.The impact of the volute's asymmetry on compressor stability correlates with rotational speed and thus with the pressure ratio,constricting the stable flow range by up to 47 percent and decreasing the maximum efficiency by 4.8 percent at the design speed.The results provide evidence to exploit the potential of intrinsic non-axisymmetric flow induced by asymmetric volute to improve the performance of turbocharger compressor with a high pressure ratio.
基金supported by the National Natural Science Foundation of China (Grant No. 51176087)
文摘The effects of Reynolds number on the performance of a high pressure-ratio turbocharger compressor were investigated by both experiments and numerical simulation. The experimental results show that the pressure ratio and the efficiency of the compressor respectively decrease by 7.9% and 6.9% when Reynolds number drops from 9.86×10 5 to 2.96×10 5 . The numerical simulation predicts a similar trend as the experimental results although it underestimates the deterioration of the performance under low Reynolds number conditions. According to simulation results, the boundary layer thickness increases at the inducer, which decreases the throat area and leads to smaller choke mass flow rate. The increments of the boundary thickness are relatively small at the rear part of the impeller. The boundary layer separation flow is severe. The interaction between boundary layer separation flows and leakage flows causes the high loss region at the rear part of the impeller passage under low Reynolds number condition.
文摘目的:观察8周有氧运动干预对单纯性肥胖患者运动后收缩压恢复(PESBPR)、体成分以及运动能力的影响,并探讨PESBPR与体成分、运动能力的关系。方法:63名肥胖患者随机分为运动组(n=35)和对照组(n=28),运动组进行为期8周的有氧运动,对照组保持日常生活习惯。实验前、后双能X-线吸收仪(dual-energy X-ray absorptiometry,DXA)测定体成分,包括脂肪重量(fat mass,FM)、去脂体重(fat-free mass,FFM)和体脂百分比(percentage of body fat,BF%);利用症状限制性递增负荷运动实验测试PESBPR和运动能力,PESBPR定义为运动实验后第3min的收缩压与运动后第1min收缩压的比值(即第3min收缩压恢复比,rSBPR),运动能力包括最大耗氧量(VO2max)、最大功率(MP)和力竭时间(ET)。结果:偏相关分析显示,rSBPR与BF%正相关(r=0.412,P<0.01),与VO2max、MP和ET均呈负相关(分别为r=-0.475,P<0.01;r=-0.366,P<0.01;r=-0.308,P<0.01)。8周实验后,运动组体重(P<0.05)、BMI(P<0.05)、FM(P<0.01)、BF%(P<0.01)、安静SBP(P<0.05)、SBPmax(P<0.01)、rSBPR(P<0.05)和PESBPR延迟发生率(P<0.01)降低,VO2max(P<0.05)、最大功率(P<0.05)和力竭时间(P<0.01)升高;对照组各指标均无显著性变化(均为P>0.05)。运动组实验前、后rSBPR变化与BF%变化呈正相关(r=0.315,P<0.01),与VO2max的变化呈负相关(r=-0.338,P<0.01)。结论:1)rSBPR与BF%正相关,与运动能力负相关,rSBPR可能是肥胖患者可调控的心血管危险因素;2)8周有氧运动可显著改善肥胖患者体成分,提高有氧运动能力,下调rSBPR及PESBPR延迟发生率。
