To give an insight into the clocking effect and its influence on the wake transportation and its interaction, the unsteady three-dimensional flow through a 1.5-stage axial low pressure turbine is simulated numerically...To give an insight into the clocking effect and its influence on the wake transportation and its interaction, the unsteady three-dimensional flow through a 1.5-stage axial low pressure turbine is simulated numerically by using a density-correction based, Reynolds-Averaged Navier-Stokes equations commercial CFD code. The 2nd stator clocking is applied over ten equal tangential positions. The results show that the harmonic blade number ratio is an important factor affecting the clocking effect. The clocking effect has very small influence on the turbine efficiency in this investigation. The difference between the maximum and minimum efficiency is about 0.1%. The maximum efficiency can be achieved when the 1st stator wake enters the 2nd stator passage near blade suction surface and its adjacent wake passes through the 2nd stator passage close to blade pressure surface. The minimum efficiency appears if the 1st stator wake impinges upon the leading edge of the 2nd stator and its adjacent wake of the 1st stator passes through the mid-channel in the 2nd stator. The wake convective transportation and the blade circulation variation due to its impingement on the subsequent blade are the main mechanism affecting the pressure variation in blade surface.展开更多
Magnetic confinement of fusion plasma has a wide range of issues to be addressed. Convective transport of plasma in the scrape-off layer of magnetic confinement devices is an interesting research topic for scientists ...Magnetic confinement of fusion plasma has a wide range of issues to be addressed. Convective transport of plasma in the scrape-off layer of magnetic confinement devices is an interesting research topic for scientists and engineers. The interest in scrape-off layer convective transport has grown in last two decades because of its effect on plasma interaction with the first wall and divertor. By increasing the particle flux into the far scrape-off layer, blobs negatively affect limiters, radio frequency antennas and the first wall. Increased convective heat transport influences core plasma confinement, at least in L-mode plasmas. Here we have reported blob formation in the absent of external magnetic field. It is observed that at low pressure -0.01 rob, transport seems to be dominated by diffusive process. At pressure 〉 1 mb, we observe convective transport in high speed imaging experiments. The role of background neutrals outside plasma boundary has the befitting answer for this phenomenon. Plasma temperature is the other key player. Another interesting observation is that at diffusive transport regime plasma life time is of the order of voltage pulse duration fed to plasma source, where as at convective transport regime plasma life time is increased appreciably.展开更多
基金supported by China Postdoctoral Science Foundation(Grant No.20100470694)Shanghai Postdoctoral Sustentation Fund,China(GrantNo.11R21413800)
文摘To give an insight into the clocking effect and its influence on the wake transportation and its interaction, the unsteady three-dimensional flow through a 1.5-stage axial low pressure turbine is simulated numerically by using a density-correction based, Reynolds-Averaged Navier-Stokes equations commercial CFD code. The 2nd stator clocking is applied over ten equal tangential positions. The results show that the harmonic blade number ratio is an important factor affecting the clocking effect. The clocking effect has very small influence on the turbine efficiency in this investigation. The difference between the maximum and minimum efficiency is about 0.1%. The maximum efficiency can be achieved when the 1st stator wake enters the 2nd stator passage near blade suction surface and its adjacent wake passes through the 2nd stator passage close to blade pressure surface. The minimum efficiency appears if the 1st stator wake impinges upon the leading edge of the 2nd stator and its adjacent wake of the 1st stator passes through the mid-channel in the 2nd stator. The wake convective transportation and the blade circulation variation due to its impingement on the subsequent blade are the main mechanism affecting the pressure variation in blade surface.
文摘Magnetic confinement of fusion plasma has a wide range of issues to be addressed. Convective transport of plasma in the scrape-off layer of magnetic confinement devices is an interesting research topic for scientists and engineers. The interest in scrape-off layer convective transport has grown in last two decades because of its effect on plasma interaction with the first wall and divertor. By increasing the particle flux into the far scrape-off layer, blobs negatively affect limiters, radio frequency antennas and the first wall. Increased convective heat transport influences core plasma confinement, at least in L-mode plasmas. Here we have reported blob formation in the absent of external magnetic field. It is observed that at low pressure -0.01 rob, transport seems to be dominated by diffusive process. At pressure 〉 1 mb, we observe convective transport in high speed imaging experiments. The role of background neutrals outside plasma boundary has the befitting answer for this phenomenon. Plasma temperature is the other key player. Another interesting observation is that at diffusive transport regime plasma life time is of the order of voltage pulse duration fed to plasma source, where as at convective transport regime plasma life time is increased appreciably.
