No abstract

The aerodynamic performances of three-dimensional compressor cascade are mainly influenced by secondary flow effects, such as the cross flow on the side wall and the corner separation at the wall-blade junction. Often, these secondary flows can produce a blockage and losses in the blade passage. A numerical study of active flow control using blowing technique in a linear compressor cascade has been carried out, in order to eliminate the 3D boundary layer stall and enhance the aerodynamic performance. The numerical simulation is performed using steady and incompressible RANS (Reynolds averaged Navier-Stokes) equations with Realizable k-ε turbulence model. Good agreement is found between numerical results and experimental data, in particular pressure coefficient (CP) and total pressure loss coefficient (). A detailed flow topology analysis is mentioned and gave the flow structure and the separation zone behavior. It was found that the blowing slot should be located upstream the dual nature critical point which represents the origin of separation. Furthermore, three suction slot configurations are used to control the separation, whereas one configuration on the suction side of the blade and two configurations are on the endwall. The first endwall slot is located parallel to the suction side of the blade and the second one is located perpendicular to the axial chord of the blade. Results indicate that the removal of the corner separation was not achieved using the slots on the blade suction side and on the endwall parallel to the suction side. Contrariwise, the perpendicular endwall slot was found to be most effective and the 3D separation is completely disappeared.

With the aim to increase blade loadings and stable operating range in highly loaded compressors, this article has been conducted to explore, through a numerical parametric study, the potential of passive control using slotted bladings in cascade configurations. The objective of this numerical investigation is to analyze the influence of location, width and slope of the slots and therefore identify the optimal configuration. The approach is based on two dimensional cascade geometry, low speed regime, steady state and turbulent RANS model. The results show the efficiency of this passive technique to delay separation and enhance aerodynamic performances of the compressor cascade. A maximum of 28.3% reduction in loss coefficient have been reached, the flow turning is increased with approximately 5 0 and high loading over a wide range of angle of attack have been obtained for the optimized control parameter.

The purpose of this work is to provide a method for the design of an axial flow compressor stage. This latter represents the front stage of a multistage compressor of industrial gas turbine. The proposed 2D design approach is based on the mean line concept which assumes that mean radius flow conditions prevailing at all other radial stations. The different conservation equations of fluid mechanic; mass, momentum, and energy with ideal gas state equation are applied in conjunction with the NASA empirical relations to compute both incidence and deviation angles at design condition. A FORTRAN computer program was implemented with the inputs such as mass flow rate, tip speed, pressure ratio, ambient temperature and pressure under larger flow coefficient and high reaction ratio. Design process begins with calculation of the channel geometric form from inlet to outlet stage. Thermodynamic properties of the working fluid are determined at rotor inlet, stator outlet and the intermediate station. Detailed geometry of the cascade; chord, pitch, camber and stagger angle is identified for both rotor and stator. The generation of the blade coordinates is performed on the basis of NACA65 profile with circular mean camber line.

Larbi Tebessi, Route de constantine 12002 TebessaThis work is aimed to examine the potential of two types of slots to control the long laminar separation bubble LoSB developed on the suction side of the thick symmetric NACA0021 airfoil. Two dimensional simulations are carried out under steady state and incompressible regime with the correlation-based intermittency turbulent model in order to predict the boundary layer transition aspect. Two slots are included separately in the airfoil and are proposed as a passive tool to manipulate the LoSB under the effect of pressure gradient between both high and low pressurized zones. The results without control are confronted with experimental data and give a good validation. Concerning the controlled configurations, the transversal slot fails to manipulate the LoSB, while the longitudinal slot reveals its positive potential to control the LoSB and therefore enhancing the lift coefficient of the airfoil and the length of the SB, however, the drag coefficient was increased.