Cooling Airflow Studies at the Leading Edge of a Film-Cooled Airfoil

1984 ◽  
Vol 106 (1) ◽  
pp. 214-221 ◽  
Author(s):  
E. S. Tillman ◽  
H. F. Jen
Keyword(s):  
Flow Field ◽  
Physical Model ◽  
Pipe Flow ◽  
Axial Flow ◽  
Leading Edge ◽  
External Flow ◽  
Total Flow ◽  
Momentum Ratio ◽  
Loss Coefficients ◽  
Flow Study

An experimental flow study on cooling holes in cylindrical models simulating the leading edge of a typical turbine airfoil is presented. The effect of external flow around the cylinder on the coolant discharge through a single hole is represented as a function of the momentum ratio of the cooling jet to the local external flow. A similar correlation was found for the effect of internal axial flow. The ability to separate the entrance and exit effects on the hole is due to the fact that the hole is a long orifice. The entrance and exit effects on the coolant flow are expressed as loss coefficients analogous to traditional loss coefficients in pipe flow. The loss coefficients for single holes were used to predict the total and individual flows through an array of holes in the presence of an external flow field. The total flow is predicted accurately as compared to the results of tests on arrays of holes. It can be concluded that the interaction between adjacent cooling holes is slight. The physical model can be used for coolant optimization studies.

scholarly journals Unsteady Flow Field due to Nozzle Wake Interaction With the Rotor in an Axial Flow Turbine: Part I — Rotor Passage Flow Field

1995 ◽  
Author(s):  
Michael A. Zaccaria ◽  
Budugur Lakshminarayana
Keyword(s):  
Flow Field ◽  
Unsteady Flow ◽  
Axial Flow ◽  
Leading Edge ◽  
Turbine Rotor ◽  
Suction Surface ◽  
Pressure Surface ◽  
Aerodynamic Interaction ◽  
Flow Gradients ◽  
Rotor Flow

The flow field in turbine rotor passages is complex with unsteadiness caused by the aerodynamic interaction of the nozzle and rotor flow fields. The two-dimensional steady and unsteady flow field at midspan in an axial flow turbine rotor has been investigated experimentally using an LDV with emphasis on the interaction of the nozzle wake with the rotor flow field. The flow field in the rotor passage is presented in Part I, while the flow field downstream of the rotor is presented in Part II. Measurements were acquired at 37 axial locations from just upstream of the rotor to one chord downstream of the rotor. The time average flow field and the unsteadiness caused by the wake has been captured. As the nozzle wake travels through the rotor flow field, the nozzle wake becomes distorted with the region of the nozzle wake near the rotor suction surface moving faster than the region near the rotor pressure surface, resulting in a highly distorted wake. The wake is found to be spread out along the rotor pressure surface, as it convects downstream of midchord. The magnitude of the nozzle wake velocity defect grows until close to midchord, after which it decreases. High values of unresolved unsteadiness were observed at the rotor leading edge. This is due to the large flow gradients near the leading edge and the interaction of the nozzle wake with the rotor leading edge. High values of unresolved unsteadiness were also observed near the rotor pressure surface. This increase in unresolved unsteadiness is caused by the interaction of the nozzle wake with the flow near the rotor pressure surface.

Three Components- and Tomographic-PIV Measurements of a Cyclone Cooling Flow in a Swirl Tube

2013 ◽  
Author(s):  
Christoph Biegger ◽  
Bernhard Weigand ◽  
Alice Cabitza
Keyword(s):  
Flow Field ◽  
Vortex Breakdown ◽  
Tracer Particle ◽  
Three Dimensional ◽  
Axial Flow ◽  
Leading Edge ◽  
Generic Model ◽  
Tube Axis ◽  
Tomographic Piv ◽  
Order Of Magnitude

Swirl cooling is a very efficient method for turbine blade cooling. However, the flow in such a system is quite complicated. In order to gain understanding of the flow structure, the velocity field in a leading edge swirl cooling chamber with two tangential inlet ducts is experimentally studied via Particle Image Velocimetry (PIV). The examined swirl tube is 1 m long and has a diameter of 50 mm. It represents an upscaled generic model of a leading edge swirl chamber. The Reynolds number, defined by the bulk velocity and the swirl tube diameter, ranges from 10,000 to 40,000, and the swirl number is 5.3. Velocity fields are measured in the center plane of the tube axis with stereo- and tomographic-PIV using two and four CCD cameras respectively. Tomographic-PIV is a three-dimensional PIV technique relying on the illumination, recording, reconstruction and cross correlation of a tracer particle distribution in a measurement volume opposed to a plane in stereo-PIV. For statistical analysis 2,000 vector maps are calculated and evaluations show a sample size of 1,000 ensembles is sufficient. Our experiment showed, that the flow field is characterized by a vortex system around the tube axis. Near the tube wall we observed an axial flow towards the outlet with a circumferential velocity component in the same order of magnitude. In contrast the vortex core consists of an axial backflow (vortex breakdown). The gained understanding of the flow field allows to predict regions of enhanced heat transfer in swirl chambers.

An Investigation of Axial Pump Backflow and a Method for its Control

1988 ◽  
Author(s):  
M. Abramian ◽  
J. H. G. Howard ◽  
P. Hermann
Keyword(s):  
Flow Field ◽  
Laser Doppler Velocimetry ◽  
Recirculation Zone ◽  
Reverse Flow ◽  
Axial Flow ◽  
Leading Edge ◽  
Low Flow ◽  
Flow Conditions ◽  
Axial Pump ◽  
Swirl Velocity

The flow field within an axial flow inducer pump near the blade leading edge was explored by laser-Doppler velocimetry to extend the previous studies of the recirculation zone which is observed at low flow rates. Although a considerable region of upstream reverse flow and swirl was observed, the recirculation zone within the impeller was of limited axial extent and was confined to the pressure side of the passage. In an attempt to reduce the flow reversal, a series of perforated disks were placed in front of the inducer. The optimum disk geometry produced minor changes in the pump performance. LDV measurements of the flow field ahead and behind the disk showed considerable reduction of the swirl velocity under reverse flow conditions, with the observed upstream swirl opposite to the inducer rotation.

Mechanism of affecting the performance and internal flow field of an axial flow subsonic compressor with self-recirculation casing treatment

2020 ◽  
pp. 095441002094267
Author(s):  
Hao G Zhang ◽  
Fei Y Dong ◽  
Wei Wang ◽  
Wu L Chu ◽  
Song Yan
Keyword(s):  
Flow Field ◽  
Axial Flow ◽  
Internal Flow ◽  
Leading Edge ◽  
Tip Clearance ◽  
Stall Margin ◽  
Casing Treatment ◽  
Leakage Flows ◽  
Blade Tip ◽  
Compressor Performance

This investigation aims to understand the mechanisms of affecting the axial flow compressor performance and internal flow field with the application of self-recirculation casing treatment. Besides, the potentiality of further enhancing the compressor performance and stability by optimizing the geometric structure of self-recirculation casing treatment is discussed in detail. The results show that self-recirculation casing treatment generates about 7.06, 7.89% stall margin improvements in the experiment and full-annulus unsteady calculation, respectively. Moreover, the compressor total pressure and isentropic efficiency are improved among most of operating points, and the experimental and calculated compressor peak efficiencies are increased by 0.7% and 0.6%, respectively. The comparisons between baseline shroud and self-recirculation casing treatment show that the flow conditions of the compressor rotor inlet upstream are improved well with self-recirculation casing treatment, and the degree of the pressure enhancement in the blade top passage for self-recirculation casing treatment is higher than that for baseline. Further, self-recirculation casing treatment can restrain the leading edge-spilled flows made by the blade tip clearance leakage flows and weaken the blade tip passage blockage. Hence, the flow loss near the rotor top passage is reduced after the application of self-recirculation casing treatment. The rotor performance and stability for self-recirculation casing treatment are greater than those for baseline. The flow-field analyses also indicate that the adverse effects caused by the clearance leakage flows of the blades tip rear are greater than those made by the clearance leakage flows of the blades leading edge. When one injecting part of self-recirculation casing treatment is aligned with the inlet of one blade tip passage, the flow-field quality in the passage is not the best among all the passages between two adjacent injecting parts of self-recirculation casing treatment. Further, the flow-field analyses also indicate that the effect of the relative position between the blade and self-recirculation casing treatment on the flows in the self-recirculation casing treatment may be ignored during the optimization of the recirculating loop configuration.

scholarly journals Unsteady Flow Field Due to Nozzle Wake Interaction With the Rotor in an Axial Flow Turbine: Part I—Rotor Passage Flow Field

1997 ◽  
Vol 119 (2) ◽  
pp. 201-213 ◽  
Author(s):  
M. A. Zaccaria ◽  
B. Lakshminarayana
Keyword(s):  
Flow Field ◽  
Unsteady Flow ◽  
Axial Flow ◽  
Leading Edge ◽  
Turbine Rotor ◽  
Suction Surface ◽  
Pressure Surface ◽  
Aerodynamic Interaction ◽  
Flow Gradients ◽  
Rotor Flow

The flow field in turbine rotor passages is complex with unsteadiness caused by the aerodynamic interaction of the nozzle and rotor flow fields. The two-dimensional steady and unsteady flow field at midspan in an axial flow turbine rotor has been investigated experimentally using an LDV with emphasis on the interaction of the nozzle wake with the rotor flow field. The flow field in the rotor passage is presented in Part I. while the flow field downstream of the rotor is presented in Part II. Measurements were acquired at 37 axial locations from just upstream of the rotor to one chord downstream of the rotor. The time-averaged flow field and the unsteadiness caused by the wake have been captured. As the nozzle wake travels through the rotor flow field, the nozzle wake becomes distorted with the region of the nozzle wake near the rotor suction surface moving faster than the region near the rotor pressure surface, resulting in a highly distorted wake. The wake is found to be spread out along the rotor pressure surface, as it convects downstream of midchord. The magnitude of the nozzle wake velocity defect grows until close to midchord, after which it decreases. High values of unresolved unsteadiness were observed at the rotor leading edge. This is due to the large flow gradients near the leading edge and the interaction of the nozzle wake with the rotor leading edge. High values of unresolved unsteadiness were also observed near the rotor pressure surface. This increase in unresolved unsteadiness is caused by the interaction of the nozzle wake with the flow near the rotor pressure surface.

Influence of Open and Closed Shroud Cavities on the Flowfield in a 2-Stage Turbine With Shrouded Blades

2003 ◽  
Author(s):  
Dieter E. Bohn ◽  
Ingo Balkowski ◽  
Hongwei Ma ◽  
Christian Tu¨mmers ◽  
Michael Sell
Keyword(s):  
Flow Field ◽  
Gas Turbines ◽  
Pressure Ratio ◽  
Axial Flow ◽  
Leading Edge ◽  
Operating Conditions ◽  
Complex Flow ◽  
Multi Stage ◽  
Flow Through ◽  
Insight Into

An important goal of the development of turbine bladings is to increase the efficiency for an optimized use of energy resources. This necessitates the most possible insight into the complex flow phenomena in multi-stage turbine bladings. This paper presents a combined numerical and experimental investigation of the flow field in a 2-stage axial turbine with shrouded blades, where the axial gap between the shroud and the endwall is varied between 1mm (closed cavities) and 5 mm (opened cavities). In the experimental setup at the Institute of Steam and Gas Turbines, Aachen University, the turbine is operated at a low pressure ratio of 1.4 with an inlet pressure of 3.2 bar. The rotating speed is adjusted by a water brake, which is integrated into a swing frame running in hydrostatic bearings. The rotor power dissipates in the water brake, which enables a very accurate angular momentum determination. The mass flow is measured through a calibrated nozzle installed upstream of the turbine inlet at an accuracy of better than 1%, from which stage efficiencies can be derived. For both geometric configurations (open and closed shroud cavities), the flow field at both inlet and outlet is measured using 5-hole probes as well as temperature probes at three operating conditions. The test rig is especially designed to investigate the influence of the cavity size. Therefore, the radial gaps between shroud and casing is held near zero in order to prevent an axial flow through the cavities. The experimental results are used as boundary conditions for corresponding numerical multi-stage calculations of the 3D flow through the 2-stage turbine, using the highly accurate steady Navier-Stokes inhouse computer code, CHT-Flow. The flow field measurements and the numerical simulations give deeper insight into some of the cavity-related flow field phenomena. The measurement results as well as the simulations indicate that the stator leading edge has little influence on the inlet flow field. The flow through the shroud cavities has a significant influence on the field and therefore on the machine’s performance.

scholarly journals Influence of Axial Clearance on Water-Jet Axial Flow Pump

2021 ◽  
Author(s):  
Chen Li ◽  
Hongming Wang
Keyword(s):  
Flow Field ◽  
Axial Flow ◽  
Pressure Rise ◽  
Leading Edge ◽  
Hydraulic Performance ◽  
Suction Surface ◽  
Surface Separation ◽  
Axial Clearance ◽  
Axial Flow Pump ◽  
Flow Pump

Three dimensional Reynolds averaged N-S equation and S-A turbulent model were adopted to simulate the flow field and hydraulic performance of the waterjet axial flow pump with the different impeller axial clearance. The numerical research results show that with the increase of axial clearance size, total pressure and static pressure rise at first and then decreases, torque and shaft power remain basically unchanged, the efficiency decreases gradually, the suction surface separation zone of stator expanded under the design condition. When the axial clearance is 30mm, the pump hydraulic performance and flow field are the best, and stator load distribution is the most uniform. When the axial clearance is 40–50mm the load of the lower part of stator leading edge is reduced greatly, which is not conducive to maintain static blade strength and maintain the stator rectifying action.

Probing Into the Connotation of Sweep Aerodynamics of Transonic Fans and Compressors

2001 ◽  
Author(s):  
X. Q. Xing ◽  
S. Zhou ◽  
X. L. Zhao
Keyword(s):  
Aspect Ratio ◽  
Flow Field ◽  
Numerical Optimization ◽  
Axial Flow ◽  
Leading Edge ◽  
Key Factors ◽  
Sweep Angle ◽  
Low Aspect Ratio ◽  
Definition Of ◽  
Transonic Rotor

Theory researches, numerical analyses and experiment studies of sweep aerodynamics in turbo-machinery had rapidly developed during the 1990s. Taking a low-aspect-ratio, high-loaded axial flow transonic rotor as the baseline, this paper attempts to probe the connotation of sweep aerodynamics of transonic fans and compressors. The definition of sweep angle was discussed. Flow field, key factors that affect structures of flow fields, linkage between leading edges as well as flow field structures in swept rotors were presented. In order to find out the optimum sweep leading edge curve under prescribed conditions, a numerical optimization program that can be added into design processes was developed.

The improvement of transonic compressor performance by the self-circulating casing treatment

2020 ◽  
pp. 095440622094226
Author(s):  
Song Yan ◽  
Wuli Chu
Keyword(s):  
Flow Field ◽  
Axial Flow ◽  
Leading Edge ◽  
Tip Clearance ◽  
The Self ◽  
Casing Treatment ◽  
Transonic Compressor ◽  
Compressor Rotor ◽  
Blade Tip ◽  
Stability Effect

The performance curve of the compressor is limited by the surge boundary, so it is of great significance to increase the stable working range of the compressor. The self-circulating casing treatment is an effective way to improve the stable working range of the compressor. In this paper, the study of the influence of the injector position of the self-circulating casing treatment on the transonic axial flow compressor rotor performance is carried out by using the numerical simulation. The influence mechanism of the injector position on the enhancing stability effect of the self-circulating casing treatment is revealed. It is found that the self-circulating casing treatment can reduce the blade tip blockage by restraining the blade tip clearance leakage flow and changing the trajectory of the tip clearance leakage vortex, thus delaying the deterioration of the rotor tip flow field and improving the rotor stability. When the injector position of the self-circulating casing treatment moves from the upstream of the leading edge of the blade tip to the trailing edge of the blade tip, the enhancing stability effect of the self-circulating casing treatment increases first and then decreases. But the high-velocity jet from the injector of the self-circulating casing treatment aggravates the mixing loss of the rotor tip flow field, so that the rotor efficiency slightly decreases after using the self-circulating casing treatment.

scholarly journals Effects of Tip Leakage Flow on the Aerodynamic Performance and Stability of an Axial-Flow Transonic Compressor Stage

Energies ◽  
2021 ◽  
Vol 14 (14) ◽  
pp. 4168
Author(s):  
Botao Zhang ◽  
Xiaochen Mao ◽  
Xiaoxiong Wu ◽  
Bo Liu
Keyword(s):  
Boundary Layer ◽  
Shock Wave ◽  
Axial Flow ◽  
Leading Edge ◽  
Rotating Stall ◽  
Tip Clearance ◽  
Leakage Flow ◽  
Tip Leakage Flow ◽  
Tip Leakage ◽  
Transonic Compressor

To explain the effect of tip leakage flow on the performance of an axial-flow transonic compressor, the compressors with different rotor tip clearances were studied numerically. The results show that as the rotor tip clearance increases, the leakage flow intensity is increased, the shock wave position is moved backward, and the interaction between the tip leakage vortex and shock wave is intensified, while that between the boundary layer and shock wave is weakened. Most of all, the stall mechanisms of the compressors with varying rotor tip clearances are different. The clearance leakage flow is the main cause of the rotating stall under large rotor tip clearance. However, the stall form for the compressor with half of the designed tip clearance is caused by the joint action of the rotor tip stall caused by the leakage flow spillage at the blade leading edge and the whole blade span stall caused by the separation of the boundary layer of the rotor and the stator passage. Within the investigated varied range, when the rotor tip clearance size is half of the design, the compressor performance is improved best, and the peak efficiency and stall margin are increased by 0.2% and 3.5%, respectively.

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