Secondary Flow and Loss Distribution in a Radial Compressor With Untwisted Backswept Vanes

1990 ◽  
Author(s):  
G. Sipos
Keyword(s):  
Three Dimensional ◽  
Leading Edge ◽  
Suction Side ◽  
Meridional Flow ◽  
Specific Work ◽  
Suction Surface ◽  
Inlet Flow ◽  
Loss Distribution ◽  
Flow Angle ◽  
Radial Compressor

The unshrouded impeller and the vaneless diffuser of a single-stage radial compressor have been investigated at three flow rates. Three-dimensional velocities and pressures were measured at a tip speed of 84 m/s by an L2F-velocimeter, a slanted single hot-wire probe and piezoresistive pressure transducers. The measurements show that upstream the blading the averaged meridional inlet flow angle is about 54 degree and a periodical variation of the meridional flow angle of about 25 degree occurs near the casing wall. Further, an inlet vortex of clockwise direction appears and an initial whirl is induced. The specific work of the initial whirl corresponds to approximately 12% of the enthalpy losses between inlet pipe and diffuser outlet. In the beginning of the passage, the inlet vortex is suppressed and a solid body vortex of counterclockwise direction can be observed. At the outlet, a heavy flow deceleration at the blade suction side with subsequent separation can be seen. Increasing the flow rate decreases the wake and causes a more uniform loss distribution in this area. The measured secondary vortex flow and rotary stagnation pressure gradients are compared with test results from impellers with inducer. The incidence of the investigated impeller is greater than that of the impellers with inducer, but the wake-jet outlet flows are very similar. Inlet losses could be reduced by improving incidence angles by matching the blade angles to the inlet flow angles. Smaller blade angles at the shroud would reduce or eliminate separation at the leading edge, and the resulting reduction in low momentum fluid along the suction surface would help to avoid separation on that surface near the outlet.

Secondary Flow and Loss Distribution in a Radial Compressor With Untwisted Backswept Vanes

1991 ◽  
Vol 113 (4) ◽  
pp. 686-695 ◽  
Author(s):  
G. Sipos
Keyword(s):  
Three Dimensional ◽  
Leading Edge ◽  
Suction Side ◽  
Periodic Variation ◽  
Specific Work ◽  
Suction Surface ◽  
Inlet Flow ◽  
Loss Distribution ◽  
Flow Angle ◽  
Radial Compressor

The unshrouded impeller and the vaneless diffuser of a single-stage radial compressor have been investigated at three flow rates. Three-dimensional velocities and pressures were measured at a tip speed of 84 m/s by an L2F-velocimeter, a slanted single hotwire probe, and piezoresistive pressure transducers. The measurements show that upstream of the blading the averaged meridional inlet flow angle is about 54 deg and a periodic variation of the meridional flow angle of about 25 deg occurs near the casing wall. Further, an inlet vortex in the clockwise direction appears and an initial whirl is induced. The specific work of the initial whirl corresponds to approximately 12 percent of the enthalpy losses between inlet pipe and diffuser outlet. In the beginning of the passage, the inlet vortex is suppressed and a solid body vortex in the counterclockwise direction can be observed. At the outlet, a heavy flow deceleration at the blade suction side with subsequent separation can be seen. Increasing the flow rate decreases the wake and causes a more uniform loss distribution in this area. The measured secondary vortex flow and rotary stagnation pressure gradients are compared with test results from impellers with inducer. The incidence of the investigated impeller is greater than that of the impellers with inducer, but the wake-jet outlet flows are very similar. Inlet losses could be reduced by improving incidence angles by matching the blade angles to the inlet flow angles. Smaller blade angles at the shroud would reduce or eliminate separation at the leading edge, and the resulting reduction in low-momentum fluid along the suction surface would help to avoid separation on that surface near the outlet.

Three-Dimensional Relief in Turbomachinery Blading

1990 ◽  
Vol 112 (4) ◽  
pp. 587-596 ◽  
Author(s):  
A. R. Wadia ◽  
B. F. Beacher
Keyword(s):  
High Speed ◽  
Three Dimensional ◽  
Axial Flow ◽  
Leading Edge ◽  
Two Dimensional ◽  
Suction Surface ◽  
Airfoil Surface ◽  
Flow Angle ◽  
Edge Loading ◽  
Cascade Analysis

The leading edge region of turbomachinery blading in the vicinity of the endwalls is typically characterized by an abrupt increase in the inlet flow angle and a reduction in total pressure associated with endwall boundary layer flow. Conventional two-dimensional cascade analysis of the airfoil sections at the endwalls indicates large leading edge loadings, which are apparently detrimental to the performance. However, experimental data exist that suggest that cascade leading edge loading conditions are not nearly as severe as those indicated by a two-dimensional cascade analysis. This discrepancy between two-dimensional cascade analyses and experimental measurements has generally been attributed to inviscid three-dimensional effects. This article reports on two and three-dimensional calculations of the flow within two axial-flow compressor stators operating near their design points. The computational results of the three-dimensional analysis reveal a significant three-dimensional relief near the casing endwall that is absent in the two-dimensional calculations. The calculated inviscid three-dimensional relief at the endwall is substantiated by airfoil surface static pressure measurements on low-speed research compressor blading designed to model the flow in the high-speed compressor. A strong spanwise flow toward the endwall along the leading edge on the suction surface of the airfoil is responsible for the relief in the leading edge loading at the endwall. This radial migration of flow results in a more uniform spanwise loading compared to that predicted by two-dimensional calculations.

Numerical Investigation on Propagation Characteristics of Inlet Total-Pressure Distortion in a Centrifugal Compressor

2021 ◽  
Author(s):  
Mingyi Wang ◽  
Zhiheng Wang ◽  
Guang Xi ◽  
Yurun Li
Keyword(s):  
Centrifugal Compressor ◽  
Total Pressure ◽  
Three Dimensional ◽  
Leading Edge ◽  
Low Pressure ◽  
Propagation Characteristics ◽  
Suction Surface ◽  
Axial Section ◽  
Flow Angle ◽  
Rotation Direction

Abstract The propagation characteristics of inlet total-pressure distortion in a centrifugal compressor are investigated by full-annulus unsteady three-dimensional numerical simulation. The inlet distortions considered in the paper are the total-pressure distortions covering a 60-deg sector (60deg distortion) and three 20-deg sectors (3*20deg distortion), respectively. One is the classical distortion form, and the other is to simulate the downstream flow of the axial section of a centrifugal-axial combined compressor. By analyzing the distributions of flow parameters, the propagation of the total-pressure distortion in the centrifugal compressor is interpreted. The results show that, with the distortion propagating to the downstream, the low-pressure region produces a phase deviation along the streamwise direction relative to the opposite direction of impeller rotation direction, and the range of distortion region is reduced. Additionally, the propagation of the inlet distortion makes the three-dimensional characteristics of airflow more complex. The flow angle increases with different amplitudes along the direction of blade height corresponding to the distorted sector. The distortion region affects the location of blades which are in a low-pressure area, and the intensity of the distortion affects the increase of the flow angle. The distortion region causes more local relative flow losses, especially near the leading edge of blade suction surface.

Aerodynamic Optimization of a Transonic Centrifugal Compressor by Using Arbitrary Blade Surfaces

2018 ◽  
Vol 140 (5) ◽  
Author(s):  
Alexander Hehn ◽  
Moritz Mosdzien ◽  
Daniel Grates ◽  
Peter Jeschke
Keyword(s):  
Centrifugal Compressor ◽  
Three Dimensional ◽  
Leading Edge ◽  
Suction Side ◽  
Ruled Surfaces ◽  
Flank Milling ◽  
Specific Work ◽  
Vaneless Diffuser ◽  
Aerodynamic Optimization ◽  
Transonic Centrifugal Compressor

A transonic centrifugal compressor was aerodynamically optimized by means of a numerical optimization process. The objectives were to increase the isentropic efficiency and to reduce the acoustic signature by decreasing the amplitude of pre-shock pressure waves at the inlet of the compressor. The optimization was performed at three operating points on the 100% speed line in order to maintain choke mass flow and surge margin. At the design point, the specific work input was kept equal. The baseline impeller was designed by using ruled surfaces due to requirements for flank milling. To investigate the benefits of arbitrary blade surfaces, the restrictions of ruled surfaces were abolished and fully three-dimensional (3D) blade profiles allowed. In total, therefore, 45 parameters were varied during the optimization. The combined geometric and aerodynamic analysis reveals that a forward swept leading edge (LE) and a concave suction side at the tip of the LE are effective design features for reducing the shock strength. Beyond that, the blade shape of the optimized compressor creates a favorable impeller outlet flow, which is the main reason why the performance of the vaneless diffuser improves. In total, a gain of 1.4% points in isentropic total-to-static efficiency, evaluated by computational fluid dynamics (CFD) at the exit plane of the vaneless diffuser, is achieved.

Three-Dimensional Relief in Turbomachinery Blading

1989 ◽  
Author(s):  
A. R. Wadia ◽  
B. F. Beacher
Keyword(s):  
High Speed ◽  
Three Dimensional ◽  
Axial Flow ◽  
Leading Edge ◽  
Two Dimensional ◽  
Suction Surface ◽  
Airfoil Surface ◽  
Flow Angle ◽  
Edge Loading ◽  
Cascade Analysis

The leading edge region of turbomachinery blading in the vicinity of the endwalls is typically characterized by an abrupt increase in the inlet flow angle and a reduction in total pressure associated with endwall boundary layer flow. Conventional two-dimensional cascade analysis of the airfoil sections at the endwalls indicates large leading edge loadings, apparently detrimental to the performance. However, experimental data exist that suggest that cascade leading edge loading conditions are not nearly as severe as those indicated by a two-dimensional cascade analysis. This discrepancy between two-dimensional cascade analyses and experimental measurements has generally been attributed to inviscid three-dimensional effects. This article reports on two- and three-dimensional calculations of the flow within two axial flow compressor Stators operating near their design points. The computational results of the three-dimensional analysis reveal a significant three-dimensional relief near the casing endwall absent in the two-dimensional calculations. The calculated inviscid three-dimensional relief at the endwall is substantiated by airfoil surface static pressure measurements on low speed research compressor blading designed to model the flow in the high speed compressor. A strong spanwise flow towards the endwall along the leading edge on the suction surface of the airfoil is responsible for the relief in the leading edge loading at the endwall. This radial migration of flow results in a more uniform spanwise loading compared to that predicted by two-dimensional calculations.

Flowfield in a Film-Cooled Three-Dimensional Contoured Endwall Passage: Aerodynamic Measurements

2007 ◽  
Author(s):  
Ross Gustafson ◽  
Gazi I. Mahmood ◽  
Sumanta Acharya
Keyword(s):  
Film Cooling ◽  
Total Pressure ◽  
Three Dimensional ◽  
Leading Edge ◽  
Suction Side ◽  
Axial Direction ◽  
Turbine Rotor ◽  
Suction Surface ◽  
Pressure Loss Coefficient ◽  
Profile Height

The influence of endwall film cooling on the aerodynamic performance of a linear blade cascade employing an asymmetric contoured endwall is measured. Cylindrical coolant holes are strategically located on the contoured endwall to provide full coverage film cooling. The endwall contour is varied along the pitch direction, and is elevated near the pressure side and depressed near the suction surface. The profile height also varies in the axial direction from the inlet to exit. Measurements of total pressure, vorticity, and velocity components are obtained at different axial locations inside the passage for six inlet blowing ratios ranging from 1.0 to 2.4. The results are compared with the measured data on the contoured endwall without any film cooling flow (uncooled case). All the tests are performed in a low speed cascade facility employing a scaled up two-dimensional blade profile of the GE-E3 turbine rotor section. The Reynolds number based on the cascade inlet velocity and blade actual chord is 2.30×105. The results near the leading edge show that the suction side-leg vortex on the uncooled endwall weakens when the film cooling jets are employed. The axial vorticity and velocity vectors near the exit plane indicate that the passage vortex is located nearer to the mid-pitch location and higher above the endwall for the film-cooled endwall than for the uncooled contoured endwall. While the overall total pressure loss coefficient across the passage decreases at the high blowing ratios compared to the uncooled case, the overall cascade loss increases with the blowing ratio.

Measurements of the Mean Flow Velocity and Velocity Fluctuations at the Exit of an FC Centrifugal Fan Rotor

1981 ◽  
Vol 103 (2) ◽  
pp. 393-399 ◽  
Author(s):  
D. Raj ◽  
W. B. Swim
Keyword(s):  
Three Dimensional ◽  
Leading Edge ◽  
Flow Region ◽  
Centrifugal Fan ◽  
Mean Flow ◽  
Suction Surface ◽  
Inlet Flow ◽  
Design Changes ◽  
Centrifugal Fans ◽  
Visualization Techniques

The flow from a small forward curved fan rotor was studied to provide guidance for fan design. The single width fan had a 0.23 m rotor containing 48 blades. It is typical of the centrifugal fans used in small air-conditioning units. Visualization techniques and hot wire measurements showed the rotor flow to be highly turbulent and strongly three-dimensional. The inlet flow was found to fill only 3/4 of the blade span. The shroud end of the rotor was an inactive or separated region. A jet-wake pattern occurred at the blade exit in the active flow region. The inlet flow separated at the leading edge of the blade suction surface. Design changes are offered to improve the performance of FC fans.

Experimental Studies of Leading Edge Contouring Influence on Secondary Losses in Transonic Turbines

2012 ◽  
Author(s):  
Ranjan Saha ◽  
Jens Fridh ◽  
Torsten Fransson ◽  
Boris I. Mamaev ◽  
Mats Annerfeldt
Keyword(s):  
Gas Turbine ◽  
Guide Vane ◽  
Experimental Studies ◽  
Three Dimensional ◽  
Leading Edge ◽  
Secondary Flows ◽  
Noticeable Effect ◽  
Flow Angle ◽  
Wide Range ◽  
Contour Plots

An experimental study of the hub leading edge contouring using fillets is performed in an annular sector cascade to observe the influence of secondary flows and aerodynamic losses. The investigated vane is a three dimensional gas turbine guide vane (geometrically similar) with a mid-span aspect ratio of 0.46. The measurements are carried out on the leading edge fillet and baseline cases using pneumatic probes. Significant precautions have been taken to increase the accuracy of the measurements. The investigations are performed for a wide range of operating exit Mach numbers from 0.5 to 0.9 at a design inlet flow angle of 90°. Data presented include the loading, fields of total pressures, exit flow angles, radial flow angles, as well as profile and secondary losses. The vane has a small profile loss of approximately 2.5% and secondary loss of about 1.1%. Contour plots of vorticity distributions and velocity vectors indicate there is a small influence of the vortex-structure in endwall regions when the leading edge fillet is used. Compared to the baseline case the loss for the filleted case is lower up to 13% of span and higher from 13% to 20% of the span for a reference condition with Mach no. of 0.9. For the filleted case, there is a small increase of turning up to 15% of the span and then a small decrease up to 35% of the span. Hence, there are no significant influences on the losses and turning for the filleted case. Results lead to the conclusion that one cannot expect a noticeable effect of leading edge contouring on the aerodynamic efficiency for the investigated 1st stage vane of a modern gas turbine.

Numerical Simulation of Clocking Effect on Wake Transportation and Interaction in a 1.5-Stage Axial Turbine

2010 ◽  
Author(s):  
Wei Li ◽  
Hua Ouyang ◽  
Zhao-hui Du
Keyword(s):  
Stokes Equations ◽  
Three Dimensional ◽  
Leading Edge ◽  
Navier Stokes ◽  
Maximum Efficiency ◽  
Suction Surface ◽  
Navier Stokes Equations ◽  
Pressure Surface ◽  
Turbine Efficiency ◽  
Small Influence

To give insight into the clocking effect and its influence on the wake transportation and its interaction, the unsteady three-dimensional flow through a 1.5-stage axial low pressure turbine is simulated numerically using a density-correction based, Reynolds-Averaged Navier-Stokes equations commercial CFD code. The 2nd stator clocking is applied over ten equal tangential positions. The results show that the harmonic blade number ratio is an important factor affecting the clocking effect. The clocking effect has a very small influence on the turbine efficiency in this investigation. The efficiency difference between the maximum and minimum configuration is nearly 0.1%. The maximum efficiency can be achieved when the 1st stator wake enters the 2nd stator passage near blade suction surface and its adjacent wake passes through the 2nd stator passage close to blade pressure surface. The minimum efficiency appears if the 1st stator wake impinges upon the leading edge of the 2nd stator and its adjacent wake of the 1st stator passed through the mid-channel in the 2nd stator.

Clocking Effects of Inlet Non-Uniformities in a Fully Cooled High-Pressure Vane: A Conjugate Heat Transfer Analysis

2015 ◽  
Author(s):  
Duccio Griffini ◽  
Massimiliano Insinna ◽  
Simone Salvadori ◽  
Francesco Martelli
Keyword(s):  
Heat Transfer ◽  
High Pressure ◽  
Film Cooling ◽  
Conjugate Heat Transfer ◽  
Cooling System ◽  
Hot Spot ◽  
Three Dimensional ◽  
Leading Edge ◽  
Suction Side ◽  
Heat Transfer Analysis

A high-pressure vane equipped with a realistic film-cooling configuration has been studied. The vane is characterized by the presence of multiple rows of fan-shaped holes along pressure and suction side while the leading edge is protected by a showerhead system of cylindrical holes. Steady three-dimensional Reynolds-Averaged Navier-Stokes (RANS) simulations have been performed. A preliminary grid sensitivity analysis with uniform inlet flow has been used to quantify the effect of spatial discretization. Turbulence model has been assessed in comparison with available experimental data. The effects of the relative alignment between combustion chamber and high-pressure vanes are then investigated considering realistic inflow conditions in terms of hot spot and swirl. The inlet profiles used are derived from the EU-funded project TATEF2. Two different clocking positions are considered: the first one where hot spot and swirl core are aligned with passage and the second one where they are aligned with the leading edge. Comparisons between metal temperature distributions obtained from conjugate heat transfer simulations are performed evidencing the role of swirl in determining both the hot streak trajectory within the passage and the coolant redistribution. The leading edge aligned configuration is resulted to be the most problematic in terms of thermal load, leading to increased average and local vane temperature peaks on both suction side and pressure side with respect to the passage aligned case. A strong sensitivity of both injected coolant mass flow and heat removed by heat sink effect has also been highlighted for the showerhead cooling system.

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