Owing to continuous efforts by many researchers the cause of mistuned vibration of turbocharger radial turbine blades has been clarified as material inhomogeneity in addition to shape deviation. And also aerodynamic damping characteristics were evaluated by CFD analysis and the vibration test varying circumferential conditions. Further the aerodynamic excitation due to VG nozzle and turbine housing scroll was studied and some countermeasures are proposed respectively. This paper introduces digestibly such technical trend from recent papers presented on main international technical conferences.

Recently the noise reduction of a small axial flow fan for cooling electronic devices is required. When the obstacles such as a fan guard grill and motor stays are located in the back of a fan, the noise of an axial flow fan becomes higher. In this study, numerical simulations were conducted by using LES (Large Eddy Simulation) with DSM (Dynamic Smagorinsky Model) about an axial flow small fan in order to clarify the noise generation mechanism of the fan with obstacle located in the back of the fan. GG model is the model with a fan guard grill. Free model is the model without a fan guard grill. The flow pattern around the fan blades and pressure fluctuation on the fan blade surfaces were compared under the conditions of with and without obstacle. The fan noise in the GG model is higher 1 dB(A)than the noise in the free model. The pressure fluctuation at pressure side surface of blades in the GG model becomes high compared with free model in the noise with frequency component of 133Hz caused by the number of motor stays. The existence of a fan guard grill and motor stays caused the reduction of axial flow velocity at the blade tip, which increased pressure fluctuation on pressure side blade surface due to the interference between tip vortex and blade surface.

The present study deals with the flow between co-rotating disks, namely, the disks which rotate co-axially in the same direction at the same angular velocity, with a narrow gap enclosed by a stationary shroud at their circumferences. The flow often accompanies azimuthally-fluctuating instabilities; a non-axisymmetric secondary flow near the shroud. In the experiments, we use a high-speed video camera and a YAG laser to visualize the flow in the axial midplane and the meridional plane between the co-rotating disks and carry out the particle image velocimetry (PIV) analysis. The torus-vortex modes are defined. In numerical calculations, the authors confirm the experimental results. Based on such PIV results, the authors define experimentally and numerically the flow torus-vortex modes TVMs in addition to core-shape modes CSMs, and reveal the details of the flow structure in each mode.

Aerodynamic performance of a twin scroll turbine was investigated under full-admission and partial-admission using steady CFD (Computational Fluid Dynamics). The CFD result shows good agreement with the experimental result quantitatively in terms of mass flow, and qualitatively in terms of efficiency. As for the flow field of CFD results, it is shown that the loss occurring downstream of the rotor inlet mainly makes the difference of the performance characteristics of each condition. Moreover, in the case of partial-admission, the flow back to non-inflow passage also generates the large loss.