Inlet Flow Angle Determination of Transonic Compressor Cascades

1992 ◽  
Vol 114 (3) ◽  
pp. 487-493 ◽  
Author(s):  
W. Steinert ◽  
R. Fuchs ◽  
H. Starken
Keyword(s):  
Test Results ◽  
Flow Conditions ◽  
Suction Surface ◽  
Inlet Flow ◽  
Flow Angle ◽  
Transonic Compressor ◽  
Measuring Techniques ◽  
Special Measuring

Tests of transonic compressor cascades require special measuring techniques to determine the inlet flow angle around sonic inlet flow conditions. One of the main requirements for these methods is the ability to adjust the inlet flow angle during the test to a prescribed value. A method has been successfully applied that relies on theoretically determined suction surface velocities. The described method was applied in testing cascades at inlet Mack numbers between M1 = 0.75−1.18. The test results confirmed the practicability of this method.

scholarly journals Inlet Flow Angle Determination of Transonic Compressor Cascades

1991 ◽  
Author(s):  
W. Steinert ◽  
R. Fuchs ◽  
H. Starken
Keyword(s):  
Test Results ◽  
Flow Conditions ◽  
Suction Surface ◽  
Inlet Flow ◽  
Flow Angle ◽  
Transonic Compressor ◽  
Measuring Techniques ◽  
Special Measuring ◽  
Mach Numbers

Tests of transonic compressor cascades require special measuring techniques to determine the inlet flow angle around sonic inlet flow conditions. One of the main requirements for these methods is the ability to adjust the inlet flow angle during the test to a prescribed value. A method has been successfully applied which relies on theoretically determined suction surface velocities. The described method was applied in testing cascades at inlet Mach numbers between M1=0.75–1.18. The test results confirmed the practicability of this method.

Numerical simulation of circulation control turbine cascade with Coanda jet and counter-flow blowing at high Mach numbers

2017 ◽  
Vol 121 (1243) ◽  
pp. 1239-1260 ◽  
Author(s):  
Y. Feng ◽  
Y. Song ◽  
F. Chen
Keyword(s):  
Guide Vane ◽  
Inlet Guide Vane ◽  
Circulation Control ◽  
Turbine Cascade ◽  
Flow Conditions ◽  
Suction Surface ◽  
Counter Flow ◽  
Flow Angle ◽  
High Mach ◽  
Coanda Jet

ABSTRACTThe performance of a circulation-control inlet guide vane that makes use of the Coanda effect was studied numerically in a high Mach number turbine cascade. The effect of different shapes (elliptic and circular) of the Coanda surface at the blade trailing edge was investigated by implementing both a Coanda jet and a counter-flow blowing. Under high subsonic flow conditions, with a total blowing ratio of 3% of the mainstream, the circulation control cascade can reach the same performance as the reference stator with a 13.5% reduction in the axial chord length, with minimal increase of the energy loss coefficient. The Coanda surfaces with small curvature are more efficient in entraining the mainstream flow, and they achieve better aerodynamic performance. The wall attachment of the Coanda jet is improved by employing counter-flow blowing, resulting in a slight increase of both the exit flow angle and the expansion ratio. Under supersonic flow conditions at the cascade exit, it is more difficult for the circulation control cascade to reach the appropriate flow turning due to a premature shock wave, which is absent in the original cascade until the very end of the suction surface.

Experimental Investigation of Gas Turbine Axial Diffuser Performance: Part II — Effect of Inlet Flow Profiles at On- and Off-Design Conditions

2021 ◽  
Author(s):  
Kenneth Brown ◽  
Stephen Guillot ◽  
Wing Ng ◽  
Lee Iksang ◽  
Kim Dongil ◽  
...  
Keyword(s):  
Experimental Investigation ◽  
Flow Visualization ◽  
Gas Turbines ◽  
Full Scale ◽  
Flow Conditions ◽  
Inlet Flow ◽  
Flow Angle ◽  
Companion Article ◽  
Pressure Distributions ◽  
Physical Insight

Abstract An experimental investigation of the effect of inlet flow conditions and improved geometries on the performance of modern axial exhaust diffusers of gas turbines has been completed. The first article in the two-part series [1] leveraged a scaled model to examine parametric variations in both diffuser geometry and inlet flow conditions with the latter having significant consequences for diffuser performance. This second article pivots on the conclusions of the companion article and offers findings and physical insight on diffuser performance for on- and off-design inlet flow conditions. Using a high-performing diffuser design from the companion article, an experimental investigation is carried out with tailored distributions of inlet Mach distribution, inlet swirl angle, and inlet radial flow angle which are designed to replicate conditions of an industry diffuser at various loads. Six different inlet distributions were investigated including a design condition and five other conditions which feature mass flows both greater than and less than the design condition. The measurements were taken at near full-scale turbine exit Reynolds number (ReH roughly 39% of the value for an H-class diffuser) and at full-scale turbine exit Mach number. The study was accomplished in a blow-down, cold-flow wind tunnel facility, and measurements included 5-hole probe traverses at planes of interest, axial pressure distributions, strut pressure distributions, and oil-flow visualization. Over the range of inlet conditions studied, pressure recovery at the exit varied by up to 68.5% from that of on-design operation. Tracking of performance coefficients along the axial direction suggested the existence of flow phenomena which were in some cases able to be confirmed with on-strut pressure measurements and flow visualization. In addition to physical insight, the results presented here offer an experimental benchmark for the sensitivity of diffuser performance to inlet flow conditions.

The Effect of Reduced Frequency on Transition and Separation at the Leading Edge of a Compressor Stator

2012 ◽  
Author(s):  
Samuel C. T. Perkins ◽  
Alan D. Henderson
Keyword(s):  
Pressure Gradient ◽  
Steady Flow ◽  
Separation Bubble ◽  
Leading Edge ◽  
Flow Conditions ◽  
Suction Surface ◽  
Flow Angle ◽  
Pressure Surface ◽  
Reduced Frequency ◽  
Wake Passing

Studies on the effects of stator reduced frequency in low pressure turbines have shown that periodic wake-induced unsteadiness can increase steady flow circulation by as much as 15% and reduce losses compared to a steady flow datum. A large separation bubble downstream of peak suction that formed under steady flow conditions was periodically suppressed by wake passing events, resulting in significantly reduced losses within the boundary layer. This research extends this concept to a controlled diffusion compressor stator blade with a circular arc leading edge. The blade was placed inside a large scale, two-dimensional, cascade with a rotating bar mechanism used to simulate an upstream rotor blade row. The blade profile has been shown to experience leading edge separations and subsequent transition on both the pressure and suction surfaces due to a velocity overspeed caused by discontinuities in surface curvature. Testing was carried out at reduced frequencies of 0.47, 0.94 and 1.88 at the design inlet flow angle 45.5° and Reynolds number based on chord of 230,000. The freestream turbulence intensity was 4.0%. A range of experimental measurements were used to look at the blade’s performance: high resolution time-averaged blade surface static pressure measurements, inlet and exit 3-hole probe traverses and instantaneous, ensemble averaged and time average surface mounted hot-film measurements for the calculation of turbulent intermittency and quasi wall-shear stress. Results showed that increasing the stator reduced frequency from, 0–1.88, increased the overall blade pressure loss. The losses generated by the pressure surface and suction surface differed significantly and are affected very differently. The pressure surface demonstrated a clear reduction in loss with an increase in reduced frequency whereas the opposite trend was seen on the suction surface. Wake-induced turbulent strips suppressed the formation of leading edge separation bubbles that formed under steady flow conditions and in between wake passing events. Wake-induced turbulent strips reduced in width and level of turbulent intermittency through the favorable pressure gradients leading to peak suction and grew in the adverse pressure gradient of the velocity overspeed. The flow between wake-induced turbulent strips partially relaminarised through the favorable pressure gradient leading to peak suction.

Effects of Inlet Flow Field Conditions on the Performance of Centrifugal Compressor Diffusers: Part 1—Discrete-Passage Diffuser

1998 ◽  
Vol 122 (1) ◽  
pp. 1-10 ◽  
Author(s):  
V. G. Filipenco ◽  
S. Deniz ◽  
J. M. Johnston ◽  
E. M. Greitzer ◽  
N. A. Cumpsty
Keyword(s):  
Centrifugal Compressor ◽  
Total Pressure ◽  
Dynamic Pressure ◽  
Pressure Recovery ◽  
Flow Conditions ◽  
Recovery Coefficient ◽  
Inlet Flow ◽  
Flow Angle ◽  
Definition Of ◽  
Pressure Recovery Coefficient

This is Part 1 of a two-part paper considering the performance of radial diffusers for use in a high-performance centrifugal compressor. Part 1 reports on discrete-passage diffusers (shown in Fig. 1) while Part 2 describes a test of a straight-channel diffuser designed for equivalent duty. Two builds of discrete-passage diffuser were tested, with 30 and 38 separate passages. Both the 30 and 38 passage diffusers investigated showed comparable range of unstalled operation and similar level of overall diffuser pressure recovery. The paper concentrates on the influence of inlet flow conditions on the pressure recovery and operating range of radial diffusers for centrifugal compressor stages. The flow conditions examined include diffuser inlet Mach number, flow angle, blockage, and axial flow nonuniformity. The investigation was carried out in a specially built test facility, designed to provide a controlled inlet flow field to the test diffusers. The facility can provide a wide range of diffuser inlet velocity profile distortion and skew with Mach numbers up to unity and flow angles of 63 to 75 deg from the radial direction. The consequences of different averaging methods for the inlet total pressure distributions, which are needed in the definition of diffuser pressure recovery coefficient for nonuniform diffuser inlet conditions, were also assessed. The overall diffuser pressure recovery coefficient, based on suitably averaged inlet total pressure, was found to correlate well with the momentum-averaged flow angle into the diffuser. Furthermore, the pressure recovery coefficient was found to be essentially independent of the axial distortion at diffuser inlet, and the Mach number, over the wide flow range (from maximum flow to the beginning of flow instabilities) investigated. It is thus shown that the generally accepted sensitivity of diffuser pressure recovery performance to inlet flow distortion and boundary layer blockage can be largely attributed to inappropriate quantification of the average dynamic pressure at diffuser inlet. Use of an inlet dynamic pressure based on availability or mass-averaging in combination with definition of inlet flow angle based on mass average of the radial and tangential velocity at diffuser inlet removes this sensitivity. [S0889-504X(00)00101-X]

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.

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