Flow Characteristics of the Nozzle Blade Cascade in the Mode of the Joint Operation with the Radial Diffuser

The obtained research data are given for the nozzle cascade used by a small-size gas turbine of an average fanning in combination with the radial diffuser. Aerodynamic characteristics of the nozzle blade cascade were determined in a wide range of a change in the Reynolds number varying from 4∙105 to 106 and the reduced velocity varying in the range of 0.4 to 1.13. The flow rate coefficient of the nozzle cascade was derived for all modes using the integral methods and the drainages behind the cascade. The kinetic energy loss coefficient and the flow angles were calculated using the measurement data of flow parameters in three control modes that were obtained due to the use of orientable pneumometric probes. When the expansion degree of the convergent –divergent annular duct behind the cascade is equal to 1.43 the flow in the narrow section of this duct is “enlocked” in the mode when the reduced velocity behind the cascade is equal to 1.127. At such velocity the Reynolds number 106 is self-similar for the flow rate coefficient. At lower values of Reynolds number, the decrease of it is accompanied by an intensive decrease in the flow rate coefficient for all the values of the reduced velocity. For the Reynolds number lower than 7∙105 an increase in the velocity results in a decreased flow rate coefficient. When this number exceeds 8∙105 an increase in the velocity results in an increase of the flow coefficient up to the moment when the flow is “enlocked” in the nozzle cascade.

Aero-Structural Coupling Strategy for a Morphing Blade Cascade Study

The coupling of aerodynamics and structural mechanics is an important step in the design process of aeronautical devices with morphing parts. In this paper, a 2D-3D coupling approach is developed to study a morphing blade cascade. Two shape memory alloy actuators are placed on the upper and lower sides of the blade to make possible the change in shape of the leading-edge. In the present work, a preliminary design study is conducted by considering a two-dimensional CFD analysis of an airfoil cascade coupled with a three-dimensional structural analysis of the whole 3D blade. A methodology is developed to match 2D and 3D meshes such that the aerodynamic loads can be easily transferred to the structural analysis. From there, the deformed blade geometry due to both aerodynamic loads and actuator work can be transferred back to the CFD solver, and the iterative aero-structural coupling loop can be repeated until convergence. The aero-structural coupling strategy developed in this work is also applied to a blade cascade study aiming to improve its performance by morphing the leading-edge of the blade. The results of this application show that by morphing the leading-edge blade of only few millimeters (less than 2 mm), it is possible to achieve a relevant performance improvement in terms of total pressure loss coefficient decrease of about 53%.

Effects of a Single Blade Incidence Angle Offset on Adjacent Blades in a Linear Cascade

The paper presents a numerical and experimental investigation of the effect of incindence angle offset in a two-dimensional section of a flat blade cascade in a high-speed wind tunnel. The aim of the current work is tp determine the aerodynamic excitation forces and approximation of the unsteady blade-loading function using a quasi-stationary approach. The numerical simulations were performed with an in-house finite-volume code built on the top of the OpenFOAM framework. The experimental data were acquired for regimes corresponding to the numerical setup. The comparison of the computational and experimental results is shown for the static pressure distributions on three blades and upstream and downstream of the cascade. The plot of the aerodynamic moments acting on all five blades shows that the adjacent blades are significantly influenced by the angular offset of the middle blade.

INVESTIGATION OF COMPRESSIBLE FLOW THROUGH A TURBINE BLADE CASCADE FOR VARIOUS TRANSONIC FLOW REGIMES

This paper deals with the numerical simulation of 2D transonic flow through the SE1050 turbine blade cascade at various flow conditions. The first one concerns the design operation with a zero incidence angle involved in the ERCOFTAC Database CFD-QNET and the second one with a +20° incidence angle corresponding to an off-design operation. Advanced mathematical models with two different models of the bypass transition to turbulence were applied for the simulation of different regimes of transonic flows as well as with attached and separated flows. Transition models proposed by Dick et al. [1] and by Menter and Smirnov [2] are based on transport equations for the intermittency coefficient. Numerical results were compared with experimental data based on the optical and pressure measurements.

Numerical simulations of the 2D supersonic flow through the tip-section turbine blade cascade with a flat profile

Numerical simulations of 2D compressible flow through the tip-section turbine blade cascade with a flat profile and the supersonic inlet were carried out by the OpenFOAM code using the Favre-averaged Navier-Stokes equations completed by the γ-Re_θt bypass transition model with the SST turbulence model. Predictions completed for nominal regimes were concentrated particularly on the effect of the shock-wave/boundary layer interaction on the transition to turbulence. Further, the link between the inlet Mach number and the inlet flow angle i.e. the so called unique incidence rule was studied. Obtained numerical results were compared with experimental data covering optical and pressure measurements.