Atsuhiro Tamura

Navier-Stokes computations of two- and three-dimensional cascade flowfields

Simplifying grid generations for cascade computations is one of the most important items in studying the use of computational fluid dynamics as an engineering tool for the design and analysis of cascades. In this paper, new practical techniques that simplify the grid generations for twoand three-dimensional viscous cascade flow computations are described. The accuracy of the computations has been examined by comparing it with experimental data of several turbine cascades. Particular attention has been given in investigating the ability of the Baldwin-Lomax turbulence model to predict the boundary-layer transition location. Results showed enough capability of the method to be considered an effective engineering tool for accurate and efficient prediction of cascade performance. However, an improvement of the transition/turbulence model is required for better prediction in transonic and off-design conditions.

Numerical analysis of a three-dimensional cascade flow by solving Navier-Stokes Equations.

Three-dimensional viscous flowfields in two different types of cascades, such as a turbine nozzle and fan blade, were numerically simulated by solving the Navier-Stokes Equations. For turbine nozzle flows, computed flow patterns on a vane in stationary and rotating frames were compared with those on a differently stacked vane. In a fundamental case, the computed results showed good agreement with experimental data. Three-dimensional flow separations as well as secondary flows caused by passage vortices could be predicted and effectively visualized using surface oil flow and streakline techniques, which were useful methods of three-dimensional flow representation.

A Numerical Investigation of Transonic Axial Compressor Rotor Flow Using a Low Reynolds Number k-ε Turbulence Model

We have developed a computer simulation code for three-dimensional viscous flow in turbomachinery based on the time-averaged compressible Navier-Stokes equations and a low Reynolds number k-e turbulence model. It is described in detail in this paper. The code is used to compute the flow fields for two types of rotor (a transonic fan NASA Rotor 67 and a transonic axial compressor NASA rotor 37), and numerical results are compared to experimental data based on aerodynamic probe and laser anemometer measurements. In the case of Rotor 67, calculated and experimental results are compared under the design speed to validate the code. The calculated results show good agreement with the experimental data, such as the rotor performance map and the spanwise distribution of total pressure, total temperature, and flow angle downstream of the rotor. In the case of Rotor 37, detailed comparisons between the numerical results and the experimental data are made under the design speed condition to assess the overall quality of the numerical solution. Furthermore, comparisons under the part speed condition are used to investigate a flow field without passage shock. The results are well predicted qualitatively. However, considerable quantitative discrepancies remain in predicting the flow near the tip. In order to assess the predictive capabilities of the developed code, computed flow structures are presented with the experimental data for each rotor and the cause of the discrepancies is discussed.Copyright

Numerical and Experimental Investigation of Secondary Flow in a High Speed Compressor Stator

A series of numerical and experimental studies have been conducted to understand the mechanism of loss generation in a high speed compressor stator with inlet radial shear flow over the span. In this study, numerical simulation is extensively used to investigate the complex three-dimensional flow in the cascades and to interpret the phenomena appeared in the high speed compressor tests. It has been shown that the inlet radial shear flow generated by upstream rotor had a significant influence on the stator secondary flow, and consequently on the total pressure loss. Redesign of the stator aiming at the reduction of loss by controlling secondary flow has been carried out and the resultant performance recovery was successfully demonstrated both numerically and experimentally.Copyright