The present paper continues the investigation started in Part I. The basic turbine stage remains the same as in Part I (an axial turbine stage with axisymmetric nozzles and mean diameter 103.5 mm). The numerical simulation method used in Part I was corrected by adding analytical correlation for disc friction losses. This approach was validated on the base of the experimental data for a geometrically close turbine. Variation of the radial velocity component at the rotor inlet was proposed as a new modification compared with Part I. The mathematical formulations of the rotor blade sweep and radial velocity component at the rotor inlet were proposed. The new modifications of the baseline were provided to establish the effects of the rotor blade sweep, velocity radial component at the rotor inlet and hub endwall contouring separately. The using of backward swept rotor blades together with the positive cinematic lean provided efficiency increasing up to 2.9% at the design conditions. It was also established that absence of a velocity radial component at the rotor inlet in the model with backward swept blades leads decreasing of the turbine performance. Axisymmetric hub contouring provided up to 1.9% efficiency growth at the part-load operation.
The present paper focuses on a comparison of cubic equations of state (EoS) with accurate Span-Wagner (SW) EoS. Aungier Redlich-Kwong (ARK) EoS, Soave Redlich-Kwong (SRK) EoS and standard Peng-Robinson (PR) EoS were chosen as the basic EoS implemented into ANSYS CFX commercial solver. Furthermore, modeling of transport properties was also considered. Rigid Non Interacting Sphere (NIS) and Interacting Sphere (IS) viscosity models were chosen for a comparison with REFPROP data. Analytically calculated density and viscosity were compared with the REFPROP values for 1 polar (ethanol) and 2 non-polar (R245fa, MDM) fluids at the first part of the investigation. This part showed no significant difference between compared EoS for the non-polar fluids and slightly lower accuracy of PR EoS for the polar fluid. A significant difference between NIS and IS models was showed.2D CFD simulations of VKI LS-89 cascade were performed for both MDM and MD 4 M siloxanes at the second part. It was showed that a preliminary analysis of the fundamental gasdynamic derivative behavior for isentropic expansion is needed for choosing of an appropriate cubic EoS. The choice of NIS or IS transport models does not show a significant effect on the obtained results.
The paper focuses on methods for an efficiency increasing of supersonic axial impulse turbines. There was chosen the axial turbine stage with axisymmetric nozzles and mean diameter 103.5 mm as the base model for a numerical and experimental investigation.There were chosen two modifications of the base design to provide an efficiency increasing: modification of the rotor leading edge design and modification of the rotor hub endwall design.The effect of these two factors on the turbine efficiency was analyzed separately. A preliminary numerical investigation showed that the rotor hub endwall modification provided an efficiency increasing up to 2% in comparison with the base model. Meanwhile, modification of the rotor leading edge shape did not provided significant efficiency increasing in comparison with the base model. Klonowicz et al. (2014)). KEYWORDS SMALL-SCALED TURBINES, SUPERSONIC TURBINESSupersonic turbine stages for different purposes were widely investigated since 1955 up to nowadays. The earlier investigations were made mostly experimentally, while the latest studies are mostly computational. The advanced methods of characteristics are used to apply in case of supersonic vanes and rotor blades design, nevertheless, supersonic stage total-to-static efficiency tends to stay of about 0.4 -0.5.Tomas P. Moffitt (1958) studied a high-work stage for a rocket pump drive with an inlet rotor Mach number of 2 and aftermixing Mach number of 2.43. Divergent part of the nozzle was designed in accordance with supersonic design technics. A rotor design using the supersonic-vortexflow theory was performed. A boundary layer thickness value was included to the design method. According to the experiments, the total-to-static stage efficiency (0.414) was significantly below the preliminary estimated value (0.504).Louis J. Goldman (1972) performed a comparison of analytically predicted and experimentally obtained total-to-static stage efficiency values. The nozzle vanes and rotor blades design was performed in accordance with the method of characteristics for the isentropic flow of a perfect gas. Then the corrections were involved to the stage design, taking into account the displacement thickness. The nozzle vanes design was made in order to obtain aftermixing Mach number of 2.85 (Mach number in stationary frame at the rotor inlet). The actual value of total-to-static stage efficiency (0.39) was well below the preliminary estimated value (0.50). Author assumed that this was a consequence of an unexpected flow separation regions and laminar boundary layer losses.Anderson et al. (1998) investigated a two stages super/transonic axial turbine for a pump drive in the framework of "Vulcan 2" project. A stage pressure ratio was equal to 12 in the design point. Due to non-optimal stage load coefficient the total-to-total efficiency remained rather low (0.4).A supersonic single-stage axial turbine was numerically studied by . A pressure ratio was set as 5.33 for the investigated turbine. The method of characteristics was ap...
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
customersupport@researchsolutions.com
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.