Pavel Safarik

Influence of Active Methods of Flow Control on Compressor Blade Cascade Flow

This paper deals with active methods of flow control, especially synthetic jet flow control. A synthetic jet was used for flow control in the compressor blade cascade to reduce the vortex structure and reduce the value of the loss coefficients. The output slot of the synthetic jet actuator was situated on the side wall on the connecting line of the leading edges of the blades. The direction of the synthetic jet was perpendicular to the main flow. The synthetic jet excitation is more effective and more efficient than a steady blowing or suction, and its great advantage is zero mass flux supplied to, or taken from the main flow. A positive influence of the synthetic jet on the flow field was proved. The flow field was also visualized.© 2008 ASME

Loss Coefficient Dependence of Turbine Blade Cascade

This paper presents the experimental results of aerodynamic research performed on a blade cascade representing the midsection of 1220 mm long rotor blades of the last stage of a large output steam turbine. The operational regime of the blade cascade is characterized by supersonic exit velocity. Isentropic exit Mach number M2is = 1.323. The experimental data analysis concerns pneumatic measurements to calculate the total pressure and the kinetic energy loss coefficients, and to evaluate them mainly with respect to the aperiodicity of the flow field. The flow structure is also studied on the basis of results obtained by means of optical methods, such as schlieren and interferometric methods.Copyright

ON THE SPEED OF SOUND IN STEAM

A study of the speed of sound in a pure water substance is presented here. The IAPWS data on the state of water and steam are applied only for investigating the speed of sound for a one-phase medium. A special numerical model for investigating the parameters of shock waves in steam is presented here and is applied for investigating extremely weak waves to obtain velocities representing the speed of sound in both one-phase and two-phase steam. Problems with the speed of sound in two-phase steam are discussed, and three types of speed of sound are derived for the metastable region of wet steam.

Aerodynamic Research on the MCA–Type Compressor Blade Cascade

This paper deals with an analysis of the flow through a high cambered compressor blade cascade. The profiles of the blade cascade have been designed to be of MCA-type. The geometric and aerodynamic parameters of the cascade are presented here. The aerodynamic research was performed in a transonic wind tunnel. Optical methods were applied to obtain information on the flow structures taking place in the interblade channels when operating in a range of subsonic and transonic velocities and at various angles of incidence. The internal shock waves and the flow separation in the rear part of the cascade channel were observed and studied. Their influence on the loss coefficient and exit flow angle at subsonic and low transonic region was assessed. The thickness of the sidewall boundary layer in the interblade channel was measured in order to investigate the development of the axial velocity density ratio (AVDR), which plays an important role in the interpretation of the results.Copyright

Research on the Tip Sections of a Long Turbine Blade

This paper reports on the results of high-speed aerodynamic research on a blade cascade. The blade cascade represents the tip section of the last stage rotor blades of a large output steam turbine. The aerodynamic characteristics of the blade cascade are presented together with flow field photographs in a range of transonic and supersonic velocities. Pictures of the flow field were obtained by means of interferometry and the schlieren method. The pressure distribution over the profiles was also evaluated using interferometry. Finally, the data for evaluating the losses and other integral characteristics of the flow exiting from the cascade were measured pneumatically with the use of a traversing device. The results are analyzed and discussed.© 2008 ASME