The Effect of Blade Leading Edge Platform Shape on Upstream Disk Cavity to Mainstream Flow Interaction of a High-Pressure Turbine Stage

2007 ◽  
Author(s):  
Remo Marini ◽  
Sami Girgis
Keyword(s):  
Leading Edge ◽  
Cavity Flow ◽  
Flow Interaction ◽  
Passage Vortex ◽  
Mainstream Flow ◽  
Transient Simulations ◽  
The Impact ◽  
Stage Efficiency ◽  
Engine Condition ◽  
Blade Leading Edge

This paper presents a CFD study of a transonic highpressure 1-stage turbine that includes the blade upstream disk cavity. The emphasis of the analysis was to understand and quantify the impact of the blade leading edge platform shape on the flow interaction between the upstream disk cavity flow and the gaspath mainstream flow. Two blade platform shapes were analyzed: a recessed and a raised leading edge shape. The results presented include steadystate and transient simulations in order to describe the flow interaction and quantify the impact on stage efficiency. A sensitivity analysis on the amount of cavity flow was performed to investigate the impact on secondary losses (interpreted by entropy generation) and stage efficiency. It was found that the blade leading edge platform shape and cavity flow amount affected the blade hub passage vortex structure and location. At the nominal engine condition, the raised leading edge platform shape showed an improvement in stage efficiency. It also showed a reduced sensitivity of stage efficiency due to cavity flow amount.

Flow Field Analysis and Nearfield Acoustic Signature Reduction of a Stationary Fan Blade Array

2020 ◽  
Author(s):  
Syed Qasim Zaheer ◽  
Peter Disimile
Keyword(s):  
Flow Field ◽  
Vortex Shedding ◽  
Leading Edge ◽  
Pressure Side ◽  
Validation Data ◽  
Array Configuration ◽  
Blade Cascade ◽  
Fan Blade ◽  
The Impact ◽  
Blade Leading Edge

Abstract A highly cambered and loaded stationary fan blade cascade of an in-service centrifugal fan is analyzed in this research work at flow conditions corresponding to design point operation of subject fan. The configuration of enclosed blade cascade includes upstream and downstream ducts. A preliminary analysis of flow variables and nearfield acoustic spectra is carried out experimentally which then provided boundary conditions and validation data for an extensive numerical analysis using Embedded Large Eddy Simulation turbulence model in ANSYS Fluent 19.0 ® environment. The comprehensive analysis of flow field and nearfield aeroacoustics of blade array configuration reveals vortex shedding from blade leading edge and its interaction with pressure side surface of adjacent blade becomes one of major source in the aeroacoustics signature of blade array. The vortex shedding frequency and the frequency of upstream turbulence interaction with blade leading edge are identified. A novel method of placing rectangular cavity on pressure side of blade array to suppress the impact of impingement of leading-edge vortex via cavity acoustic wave is explored. The numerical results reveal a reduction in noise by 6dB encouraging the efficacy of this method as a passive technique to reduce aeroacoustics signature of researched blade array configuration.

Impact of Main and Splitter Blade Leading Edge Contour on the Performance of High Pressure Ratio Centrifugal Compressors

2014 ◽  
Author(s):  
Rodrigo R. Erdmenger ◽  
Vittorio Michelassi
Keyword(s):  
High Pressure ◽  
Pressure Ratio ◽  
Leading Edge ◽  
Tip Clearance ◽  
Flow Coefficient ◽  
Centrifugal Compressors ◽  
Operating Range ◽  
High Pressure Ratio ◽  
The Impact ◽  
Blade Leading Edge

The impact of leading edge sweep in an attempt to reduce shock losses and extend the stall margin on axial compressors has been extensively studied, however only a few studies have looked at understanding the impact of leading edge contouring on the performance of centrifugal compressors. The present work studies the impact of forward and aft sweep on the main and splitter blade leading edge of a generic high flow coefficient and high pressure ratio centrifugal compressor design and the impact on its overall peak efficiency, pressure ratio and operating range. The usage of aft sweep on the main blade led to an increase of the pressure ratio and efficiency, however it also led to a reduction of the stable operating range of the impeller analyzed. The forward sweep cases analyzed where the tip leading edge was displaced axially forward showed a slight increase in pressure ratio, and a significant increase on operating range. The impact of leading edge sweep on the sensitivity of the impeller performance to tip clearance was also studied. The impeller efficiency was found to be less sensitive to an increase of tip clearance for both aft and forward sweep cases studied. The forward sweep cases studied also showed a reduced sensitivity from operating range to tip clearance. The studies conducted on the splitter leading edge profile indicate that aft sweep may help to increase the operating range of the impeller analyzed by up to 16% while maintaining similar pressure ratio and efficiency characteristics of the impeller. The improvement of operating range obtained with the leading edge forward sweep and splitter aft sweep was caused by a reduction of the interaction of the tip vortex of the main blade with the splitter tip, and a reduction of the blockage caused by this interaction.

Unsteady Forcing vs. Efficiency: The Effect of Clocking on a Transonic Industrial Compressor

2013 ◽  
Author(s):  
Florian Fruth ◽  
Damian M. Vogt ◽  
Ronnie Bladh ◽  
Torsten H. Fransson
Keyword(s):  
Stokes Equations ◽  
Leading Edge ◽  
Forced Response ◽  
Navier Stokes ◽  
Navier Stokes Equations ◽  
Transonic Compressor ◽  
Design Changes ◽  
Transient Simulations ◽  
Stator Blade ◽  
The Impact

A numerical investigation on the impact of clocking on the efficiency and the aerodynamic forcing of the first 1.5 stages of an industrial transonic compressor was conducted. Using unsteady 3D Navier-Stokes equations, seven clocking positions were calculated and analyzed. Efficiency changes due to clocking were up to 0.125%, whereas modal excitation changes up to 31.7%. However, no direct correlation between the parameters of efficiency, stimulus and modal excitation was found as reported by others. It was found that potential forced response risks can be reduced by clocking, resulting only in minor efficiency penalties. Assuming almost sinusoidal behavior of efficiency and stimulus changes, as found in this investigation, both parameters can be set into correlation by using an ellipse interpolation. Direct impact of design changes on efficiency and stimulus through clocking can be deducted from that graph and quick estimations about extrema be made using only 5–6 transient simulations. Results however also stress the importance of considering modal excitation when optimizing for aerodynamic forcing, for which the ellipse interpolation is not necessarily possible. Highest efficiency is achieved with the IGV wake impinging on the stator blade leading edge at mid-span. It was found however that this alone is not a sufficient criteria in case of inclined wakes, as wake impingement at different span positions leads to different efficiencies.

Effect of Blade Geometry and Foreign Object Kinetic Energy on Blades Damage

2010 ◽  
Author(s):  
Mickhail S. Nikhamkin ◽  
Leonid V. Voronov ◽  
Irina V. Semenova
Keyword(s):  
Numerical Analysis ◽  
Numerical Model ◽  
Kinetic Energy ◽  
Leading Edge ◽  
Material Behavior ◽  
Plastic Strain Rate ◽  
Problem Solution ◽  
Foreign Object ◽  
The Impact ◽  
Blade Leading Edge

One of the main reasons of engine failure is foreign object damage (FOD) of compressor blades. Engine manufactures are constantly searching for blade endurance increasing methods. The problem solution requires investigation in the field of the structural factor effects on the blade damageability. The paper describes numerical analysis method of the damage process. Based on “the typical damage case” concept, this method can simulate typical blade damages: dents, tears, notches. The numerical analysis is performed by the finite element method (FEM). Material behavior is described with an elastic-plastic strain rate dependent model. Blade damage numerical model is thoroughly verified by the results of special experiments. To implement the experimental modeling, actual blades were damaged, a special experimental setup based on a pneumatic gun being used. The foreign object kinematic parameters before and after the impact, a blade leading edge displacements and residual deformation fields registered in the experiment are used as verification criteria for the numerical model. The blade leading edge thickness and a foreign object energy effect on the blade damageability is investigated. The research showed there are some foreign object kinetic energy critical values at which the damage mechanism and type are changed.

scholarly journals Numerical Investigations of Film Cooling and Particle Impact on the Blade Leading Edge

Energies ◽  
2021 ◽  
Vol 14 (4) ◽  
pp. 1102
Author(s):  
Ke Tian ◽  
Zicheng Tang ◽  
Jin Wang ◽  
Milan Vujanović ◽  
Min Zeng ◽  
...  
Keyword(s):  
Particle Size ◽  
Film Cooling ◽  
Gas Turbines ◽  
Three Dimensional ◽  
Leading Edge ◽  
Turbine Engines ◽  
Small Particles ◽  
The Impact ◽  
First Time ◽  
Blade Leading Edge

As a vital power propulsion device, gas turbines have been widely applied in aircraft. However, fly ash is easily ingested by turbine engines, causing blade abrasion or even film hole blockage. In this study, a three-dimensional turbine cascade model is conducted to analyze particle trajectories at the blade leading edge, under a film-cooled protection. A deposition mechanism, based on the particle sticking model and the particle detachment model, was numerically investigated in this research. Additionally, the invasion efficiency of the AGTB-B1 turbine blade cascade was investigated for the first time. The results indicate that the majority of the impact region is located at the leading edge and on the pressure side. In addition, small particles (1 μm and 5 μm) hardly impact the blade’s surface, and most of the impacted particles are captured by the blade. With particle size increasing, the impact efficiency increases rapidly, and this value exceeds 400% when the particle size is 50 μm. Invasion efficiencies of small particles (1 μm and 5 μm) are almost zero, and the invasion efficiency approaches 12% when the particle size is 50 μm.

Impact of Tip Clearance Size and Rotation Speed on the Surge Onset in a High Pressure Centrifugal Compressor

2012 ◽  
Author(s):  
Nicolas Buffaz ◽  
Isabelle Trébinjac
Keyword(s):  
Centrifugal Compressor ◽  
Rotation Speed ◽  
Pressure Sensors ◽  
Leading Edge ◽  
Suction Side ◽  
Boundary Layer Separation ◽  
Tip Clearance ◽  
Vaned Diffuser ◽  
The Impact ◽  
Blade Leading Edge

The results presented in the paper aim at investigating the impact of tip clearance size and rotation speed on the surge onset in a transonic single-stage centrifugal compressor composed of a backswept splittered unshrouded impeller and a vaned diffuser. For that purpose, various slow throttle ramps into surge were conducted from 100% to 60% design speed of the compressor and two different tip clearance heights were investigated. The 1MW LMFA-ECL test rig was used to carry out the tests in the compressor stage. Unsteady pressure measurements up to 150 KHz were carried out in the inducer (i.e. the entry zone of the impeller between the main blade leading edge and the splitter blade leading edge) and in the diffuser thanks to nine and fifteen static pressure sensors respectively. At cruise rotation speed (92.7% of the nominal rotation speed), the surge is triggered by a boundary layer separation on the diffuser vane suction side whatever the tip clearance height may be. No precursor of surge or pre-surge activity has been recorded in the diffuser or in the impeller. The surge reveals a spike-type inception and the tip clearance increase does not change the path into instability. At lower rotation speeds high frequency disturbances (nearly half the BPF) have been recorded in the inducer before surge. These disturbances can be understood as “tip clearance rotating disturbances” because they are generated at the leading edge of the main blades and move along the tip clearance trajectory. These disturbances reveal a very unstable behavior while the compressor runs into a stable operating point even if the flow at the tip of impeller is dramatically affected by these disturbances. But these disturbances do not trigger the surge which always originates in the diffuser.

Systematic Experimental Evaluations Aimed at Optimizing the Geometry of Axial Casing Groove in a Compressor

2019 ◽  
Author(s):  
Huang Chen ◽  
Subhra Shankha Koley ◽  
Yuanchao Li ◽  
Joseph Katz
Keyword(s):  
Leading Edge ◽  
Low Flow ◽  
Maximum Efficiency ◽  
Flow Angle ◽  
Efficiency Loss ◽  
Stall Margin ◽  
Blade Rotation ◽  
Stall Margin Improvement ◽  
The Impact ◽  
Blade Leading Edge

Abstract Performance and flow measurements are carried out to investigate the impact of varying the geometry of axial casing grooves on the stall margin and efficiency of an axial turbomachine. Prior studies have shown that skewed semi-circular grooves installed near the blade leading edge (LE) have multiple effects on the flow structure, including ingestion of the tip leakage vortex (TLV), suppression of backflow vortices, and periodic variations of flow angle. To determine which of these phenomena is a key contributor, the present study examines the impact of several grooves, all with the same inlet geometry, but with outlets aimed at different directions. The “U” grooves that have circumferential exits aimed against the direction of blade rotation achieve the highest stall margin improvement of well above 60% but cause a 2.0% efficiency loss near the best efficiency point (BEP). The “S” grooves, which have exits aimed with the blade rotation, achieve a relatively moderate stall margin improvement of 36%, but they do not reduce the BEP efficiency. Other grooves, which are aligned with and against the flow direction at the exit from upstream inlet guide vanes, achieve lower improvements. These trends suggest that causing high periodic variations in flow angle around the blade leading edge is particularly effective in extending the stall margin, but also reduces the peak efficiency. In contrast, maintaining low flow angles near the LE achieves more moderate improvement in stall margin, without the maximum efficiency loss. Hence, of the geometries tested, the S grooves appear to have the best overall impact on the machine performance. Velocity measurements and flow visualizations are performed in an axial plane located downstream of the grooves, near the trailing edge of the rotor. Reduced efficiency or performance co-occurs with elevated circumferential velocity in the tip region, but differences in the axial blockage are subtle. Yet, near the BEP, the regions with reduced axial velocity, or even negative velocity between the TLV and the endwall, are wider behind the U grooves compared to the S grooves. The vorticity profiles also show that at low flow rates the TLV is ingested entirely by the grooves, in contrast to the best efficiency point, where a considerable fraction of the TLV rollup occurs downstream of the grooves.

Effects of Blade Leading Edge Fillet on Near Wall Pressure and Heat Transfer in a Linear Turbine Cascade

2014 ◽  
Author(s):  
Gazi I. Mahmood ◽  
Sumanta Acharya
Keyword(s):  
Heat Transfer ◽  
Gas Turbine ◽  
Thermal Stresses ◽  
Static Pressure ◽  
Leading Edge ◽  
Secondary Flows ◽  
Blade Surface ◽  
Nusselt Numbers ◽  
Passage Vortex ◽  
Blade Leading Edge

Thermal stresses and failure of components in the gas turbine passages are common due to exposure of the passage walls to extremely hot combustion gasses. In addition, the gas turbine engine efficiency suffers due to secondary flows and passage vortex formations in turbine passages. Investigations are being conducted to reduce the thermal stresses and secondary flows in the turbine passages with endwall modifications and film cooling. The present investigation employs two types of fillets at the junction of blade leading edge and endwall in a low speed linear blade cascade to control the effects of passage vortex. Blade and endwall static pressure, axial vorticity and air temperature near endwall, and Nusselt numbers on endwall and blade wall are measured and presented in the cascade passage with and without the leading edge fillets. A constant Reynolds number of 233,000 based on the blade chord and the inlet velocity is employed for the measurements. The blade profile is obtained from the hub-side of first stage blade in the GE-E3 gas turbine and scaled 10 times in the present cascade. One of the two fillet shapes has a linear profile from the blade to endwall (Filet 1), and the other has a parabolic profile (Fillet 2) from the blade to endwall. Fillets are employed only at the blade leading edge at the bottom endwall. Results on axial vorticity and air temperature indicate that the fillets weaken passage vortex and reduce heat transfer from the endwall. This occurs as the pitchwise endwall pressure difference from the pressure side to the suction side is reduced near the filleted region. However, the distributions of wall static pressure coefficients and Nusselt numbers along the blade surface are about the same with and without the fillets and indicate no effects from the fillets on the blade surface. The blade-loadings are thus unaffected and require no design modifications with the fillets. The endwall Nusselt number distributions show lower values for the fillets than for the baseline (without fillets) which also indicate reduced heat transfer to or from the endwall. The results of the present investigations thus can be applied in designing the blade passages where the secondary flow effects are passively controlled and endwall thermal stresses are reduced.

scholarly journals Influence of Blade Leading-Edge Shape on Rotating-Stalled Flow Characteristics in a Centrifugal Pump Impeller

2020 ◽  
Vol 10 (16) ◽  
pp. 5635
Author(s):  
Hongying Luo ◽  
Ran Tao ◽  
Jiandong Yang ◽  
Zhengwei Wang
Keyword(s):  
Flow Field ◽  
Centrifugal Pump ◽  
Incidence Angle ◽  
Flow Characteristics ◽  
Leading Edge ◽  
Rotating Stall ◽  
Pump Impeller ◽  
The Impact ◽  
Centrifugal Pump Impeller ◽  
Blade Leading Edge

Rotating stall, which is a common phenomenon in turbomachinery, strongly relates to the flow rate condition. In centrifugal impellers, rotating stall was induced by the incidence angle on blade leading-edge at partial-load. The blade leading-edge shape also influences the rotating stall because of the subtle change of local flow-field. In this study, the influence of blade leading-edge shape on rotating-stalled flow characteristics was studied in a six-blade centrifugal pump impeller. The stall pattern was “alternating”: Three passages were stalled, three passages were well-behaved, and the stalled and well-behaved passages occurred alternately. The stalled flow characteristics can be studied without the interruption of stall cell movement. Four types of blade leading-edge (blunt, sharp, ellipse, and round) were numerically compared based on the initial typical impeller and the numerical–experimental verification. The numerical comparison shows that the leading-edge shape has a strong influence on the stalled flow pattern, velocity, pressure, turbulence kinetic energy, and flow-induced noise inside impellers. The blunt and sharp leading-edge impellers had a similar internal pattern; the ellipse and round leading-edge impellers were also similar in the internal flow-field. Pressure pulsation analysis showed more obvious differences among these impellers. The main frequency and the pulsation peak–peak values were completely different because of the slight leading-edge shape differences. It revealed the impact of leading-edge geometry on the transient flow-field change under the same incidence angle conditions. It also provided reference for influencing or controlling the rotating stall by blade profile design.

scholarly journals Numerical Laser Energy Deposition on Supersonic Cavity Flow and Sensor Placement Strategies to Control the Flow

2013 ◽  
Vol 2013 ◽  
pp. 1-8 ◽  
Author(s):  
Ibrahim Yilmaz ◽  
Selin Aradag
Keyword(s):  
Energy Deposition ◽  
Laser Energy ◽  
Leading Edge ◽  
Cavity Flow ◽  
Time Flow ◽  
Computational Fluid Dynamics Simulations ◽  
Dynamics Simulations ◽  
Proper Orthogonal ◽  
The Impact ◽  
Supersonic Cavity

In this study, the impact of laser energy deposition on pressure oscillations and relative sound pressure levels (SPL) in an open supersonic cavity flow is investigated. Laser energy with a magnitude of 100 mJ is deposited on the flow just above the cavity leading edge and up to 7 dB of reduction is obtained in the SPL values along the cavity back wall. Additionally, proper orthogonal decomposition (POD) method is applied to thex-velocity data obtained as a result of computational fluid dynamics simulations of the flow with laser energy deposition. Laser is numerically modeled using a spherically symmetric temperature distribution. By using the POD results, the effects of laser energy on the flow mechanism are presented. A one-dimensional POD methodology is applied to the surface pressure data to obtain critical locations for the placement of sensors for real time flow control applications.

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