Effect of Weak Swirling Flow on Film Cooling Performance

1990 ◽  
Vol 112 (4) ◽  
pp. 786-791 ◽  
Author(s):  
C. Gau ◽  
W. B. Hwang
Keyword(s):  
Film Cooling ◽  
Swirling Flow ◽  
Swirl Flow ◽  
Cover Plate ◽  
Mixing Rate ◽  
Swirl Number ◽  
Cooling Effectiveness ◽  
Radial Temperature ◽  
Film Cooling Effectiveness ◽  
Annular Slot

Experiments have been performed in a large circular pipe to study and obtain the film cooling effectivenesses with the presence of weak swirling flow in the mainstream. The swirling flow is generated by a flat vane swirler situated upstream. Cooling film is injected from an annular slot formed by the pipe wall and the circular cover plate. The radial temperature distribution measurements at several axial locations were used to infer the rate of mixing of film jet with swirling flow. The swirl number, which increases with turbulence intensity and swirl velocity in the mainstream, can significantly increase the mixing rate of film jet with swirl flow and decrease the film cooling effectiveness. During the course of the experiments, the blowing ratio ranged from 0.5 to 1.75 and the swirl number ranged from 0 to 0.6. Correlation equations for the film cooling effectiveness, which account for the effect of swirling flow, are obtained.

Effects of Inlet Swirl on Pressure Side Film Cooling of Neighboring Vane Surface

2019 ◽  
Vol 11 (6) ◽  
Author(s):  
Yang Zhang ◽  
Yifei Li ◽  
Xiutao Bian ◽  
Xin Yuan
Keyword(s):  
Film Cooling ◽  
Swirling Flow ◽  
Density Ratio ◽  
Suction Side ◽  
Scale Model ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Lean Combustion ◽  
Inlet Swirl ◽  
Nozzle Guide

The lean combustion chamber of low NOx emission engines has a short distance between combustion outlet and nozzle guide vanes (NGVs), with strong swirlers located upstream of the turbine inlet to from steady circulation in the combustion region. Although the lean combustion design benefits emission control, it complicates the turbine’s aerodynamics and heat transfer. The strong swirling flow will influence the near-wall flow field where film cooling acts. This research investigates the influence of inlet swirl on the film cooling of cascades. The test cascades are a 1.95 scale model based on the GE-E3 profile, with an inlet Mach number of 0.1 and Reynolds number of 1.48 × 105. Film cooling effectiveness is measured with pressure-sensitive paint (PSP) technology, with nitrogen simulating coolant at a density ratio of near to 1.0. Two neighboring passages are investigated simultaneously, so that pressure and suction side the film cooling effectiveness can be compared. The inlet swirl is produced by a swirler placed upstream, near the inlet, with five positions along the pitchwise direction. These are as follows: blade 1 aligned, passage 1–2 aligned, blade 2 aligned, passage 2–3 aligned and blade 3 aligned. According to the experimental results, the near-hub region is strongly influenced by inlet swirl, where the averaged film cooling effectiveness can differ by up to 12% between the neighboring blades. At the spanwise location Z/Span = 0.7, when the inlet swirl is moved from blade 1 aligned (position 5) to blade 2 aligned (position 3), the film cooling effectiveness in a small area near the endwall can change by up to 100%.

Research on Film Cooling Mechanism of Vortex Reconstruction Induced by Swirling Coolant Flow

2017 ◽  
Author(s):  
Guoqiang Yue ◽  
Ping Dong ◽  
Yuting Jiang ◽  
Jie Gao ◽  
Qun Zheng
Keyword(s):  
Film Cooling ◽  
Swirling Flow ◽  
Coolant Flow ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Blowing Ratio ◽  
Cooling Mechanism ◽  
New Type ◽  
The Difference ◽  
Momentum Region

In this paper, a new-type coolant chamber with higher film cooling effectiveness is proposed based on the vortex reconstruction. Three different kinds of coolant chamber configuration based on the cylindrical hole are selected to develop the swirling flow structure of coolant, and the comparative investigations have been carried out to study the effect of different coolant chambers at blowing ratios ranging from 0.5 to 2.0. The results show that the coolant jet momentum is small at low blowing ratio, and the difference of the film cooling effectiveness for three kinds of coolant chamber configuration is little, but the advantage of swirling inflow coolant film cooling becomes obviously with the increase of blowing ratio. When the blowing ratio is 2.0, the jet momentum with original coolant chamber configuration is large and uniform, which leads to the lowest cooling effectiveness due to the formation of a strong kidney vortex. The first coolant chamber configuration has a low jet momentum region at upstream of the film hole, the coolant in this region interacts with high temperature mainstream and bypasses the large jet momentum coolant to attach cooling surface at downstream, the cooling effect is obvious at downstream. The second coolant chamber configuration is sprayed with the structure of unidirectional vortex, which forms a vortex pressing on other vortex, making the coolant in pressed vortex attach surface better. The coolant laterally velocity is large, producing the best coverage and the higher film cooling effectiveness. The average film cooling effectiveness of the first and second coolant chamber configuration are larger than original by about 10% and 25%, respectively (M = 1.0), or 50% and 550% (M = 1.5). From the distribution of average film cooling effectiveness of different blowing ratios, it can be concluded that the optimal blowing ratio of swirling coolant flow film cooling is in the range of 1.8 to 2.1.

Film Cooling With Swirling Coolant Flow Controlled by Impingement Cooling in a Closed Cavity

2011 ◽  
Author(s):  
Kenichiro Takeishi ◽  
Yutaka Oda ◽  
Yuta Egawa ◽  
Satoshi Hada
Keyword(s):  
Wind Tunnel ◽  
Film Cooling ◽  
Vertical Direction ◽  
Coolant Flow ◽  
Swirl Number ◽  
Cooling Effectiveness ◽  
Closed Cavity ◽  
Film Cooling Effectiveness ◽  
Cooling Hole ◽  
Sublimation Method

A new film cooling concept has been developed by managing the swirled film coolant induced inside a hexagonal plenum by two slant impingement jets, which are inclined at α degree toward the vertical direction and installed in a staggered position on the plenum chamber wall. Film cooling tests have been conducted by using a circular film cooling hole model mounted on a low speed wind tunnel. Heat transfer coefficient distributions of inclined jet impingements in a closed cavity was measured by naphthalene sublimation method and the film cooling effectiveness on the surface of the wind tunnel was measured by pressure sensitive paint (PSP). It appeared from experimental results that the swirled film coolant flow deteriorated the film cooling effectiveness at low swirl number but improved it at high swirl number. To investigate the mechanism of the improved film cooling effectiveness by the swirled coolant, the spatial distribution of the film cooling effectiveness and flow field were measured by laser induced fluorescence (LIF) and particle image velocimetry (PIV), respectively. The coolant jet penetration into mainstream is suppressed by the strong swirling motion of the coolant. As a result the film cooling effectiveness distribution on the wall keeps higher value behind the cooling hole over a long range. Additionally, kidney vortex structure was disappeared at high swirl number.

Investigation on flow field and heat transfer characteristics of film cooling with different swirling directions for coolant flow

2021 ◽  
pp. 095765092199763
Author(s):  
Jian Zhang ◽  
Qun Zheng ◽  
Guoqiang Yue ◽  
Yuting Jiang
Keyword(s):  
Film Cooling ◽  
Swirling Flow ◽  
Hexagonal Prism ◽  
Simulation Studies ◽  
Heat Transfer Characteristics ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Entrainment Effect ◽  
Compound Angle ◽  
Inlet Chamber

In this paper, a hexagonal prism inlet chamber is used to form a swirling flow for the film cooling, and three kinds of compound angle of film hole ( γ = 10°, 20°, 30°) with clockwise swirling or counterclockwise swirling are used for numerical simulation studies. The influence of different compound angles of film hole and the swirling directions for the film cooling effectiveness are obtained. The results show that the film cooling effectiveness and spanwise cooling coverage range of the clockwise swirling or counterclockwise swirling flow both are low when the compound angle of film hole is 10°. With the increasing compound angle of film hole, the kidney shaped vortex of film hole exit gradually weakens until it disappears, which reduces the entrainment effect by the coolant jet. So that the spanwise coverage range of two swirling modes is obviously improved. When the compound angle of film hole is 30° compared to 10°, the average spanwise film cooling effectiveness of clockwise swirling and counterclockwise swirling are increased by about 133.75 and 212.6%, respectively. The average spanwise film cooling effectiveness on the downstream of film hole for counterclockwise swirling is increased by about 140% compared with clockwise swirling.

Effects of Inlet Swirl on Suction Side Phantom Cooling

2016 ◽  
Author(s):  
Yang Zhang ◽  
Yifei Li ◽  
Xin Yuan
Keyword(s):  
Film Cooling ◽  
Swirling Flow ◽  
Guide Vane ◽  
Density Ratio ◽  
Electric Energy ◽  
Side Surface ◽  
Suction Side ◽  
Rotating Flow ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness

Though the temperature of the coolant injected from the endwall increases after the mixing process in the main flow, the injections moving from the endwall to the airfoil suction side still have the potential of second order cooling. This part of the coolant is called “Phantom cooling” in the paper. This paper is focused on the function of the coolant from fan-shaped holes on endwall surface which brought by passage vortex to the airfoil suction side. The test cascades are based on the profile of General Electric Energy Efficient Engine (GE-E3), with the inlet Mach number of 0.1 and Reynolds number of 1.46×105. The scale ratio of the test vanes is 1.95 and the film cooling effectiveness is tested with Pressure Sensitive Painting (PSP) Technology. Nitrogen is used to simulate the coolant which can provide a density ratio near 1.0. Two adjacent passages are investigated simultaneously by which the film cooling effectiveness can be compared in the same case on the suction side surface. The inlet rotating flow is simulated by an upstream swirler at the inlet, fixed at 5 different positions along the pitchwise direction. They are Blade 0 aligned, Passage 1 aligned, Blade 1 aligned, Passage 2 aligned and Blade 2 aligned. According to the experimental results, the inlet rotating flow can dominate the film cooling effectiveness distribution at the Suction Side. The averaged film cooling effectiveness changes substantially with the change in the swirler position. The inlet swirling flow effects are compared on the adjacent vanes at upstream and downstream regions. The research shows that the different pitchwise position of the inlet swirler is a significant factor which can change the phantom cooling phenomenon on the suction side. The relative position of inlet swirler cannot be ignored for Nozzle Guide Vane design.

IMPROVING ADIABATIC FILM-COOLING EFFECTIVENESS BY USING AN UPSTREAM PYRAMID

2016 ◽  
Vol 8 (2) ◽  
pp. 135-146 ◽  
Author(s):  
Zineb Hammami ◽  
Zineddine Ahmed Dellil ◽  
Fadela Nemdili ◽  
Abbes Azzi
Keyword(s):  
Film Cooling ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness

The Effect of Using Ramps with Trench Cylindrical Holes on Film Cooling Effectiveness

2015 ◽  
Vol 3 (2) ◽  
pp. 15-27
Author(s):  
Ahmed A. Imram ◽  
Humam K. Jalghef ◽  
Falah F. Hatem
Keyword(s):  
Numerical Simulation ◽  
Film Cooling ◽  
Air Injection ◽  
Baseline Model ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Blowing Ratio ◽  
Hot Air ◽  
Test Study ◽  
Cylindrical Holes

     The effect of introducing ramp with a cylindrical slot hole on the film cooling effectiveness has been investigated experimentally and numerically. The film cooling effectiveness measurements are obtained experimentally. A test study was performed at a single mainstream with Reynolds number 76600 at three different coolant to mainstream blowing ratios 1.5, 2, and 3. Numerical simulation is introduced to primarily estimate the best ramp configurations and to predict the behavior of the transport phenomena in the region linked closely to the interaction between the coolant air injection and the hot air mainstram flow. The results showed that using ramps with trench cylindrical holes would enhanced the overall film cooling effectiveness by 83.33% compared with baseline model at blowing ratio of 1.5, also  the best overall flim cooling effectevness was obtained at blowing ratio of 2 while it is reduced at blowing ratio of 3.

Conjugate Heat Transfer and Film Cooling of a Multi-Stage Cooling Scheme

2008 ◽  
Author(s):  
M. Ghorab ◽  
S. I. Kim ◽  
I. Hassan
Keyword(s):  
Heat Transfer ◽  
Film Cooling ◽  
Gas Turbines ◽  
Conjugate Heat Transfer ◽  
Density Ratio ◽  
Design Parameters ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Multi Stage ◽  
Internal Gap

Cooling techniques play a key role in improving efficiency and power output of modern gas turbines. The conjugate technique of film and impingement cooling schemes is considered in this study. The Multi-Stage Cooling Scheme (MSCS) involves coolant passing from inside to outside turbine blade through two stages. The first stage; the coolant passes through first hole to internal gap where the impinging jet cools the external layer of the blade. Finally, the coolant passes through the internal gap to the second hole which has specific designed geometry for external film cooling. The effect of design parameters, such as, offset distance between two-stage holes, gap height, and inclination angle of the first hole, on upstream conjugate heat transfer rate and downstream film cooling effectiveness performance are investigated computationally. An Inconel 617 alloy with variable properties is selected for the solid material. The conjugate heat transfer and film cooling characteristics of MSCS are analyzed across blowing ratios of Br = 1 and 2 for density ratio, 2. This study presents upstream wall temperature distributions due to conjugate heat transfer for different gap design parameters. The maximum film cooling effectiveness with upstream conjugate heat transfer is less than adiabatic film cooling effectiveness by 24–34%. However, the full coverage of cooling effectiveness in spanwise direction can be obtained using internal cooling with conjugate heat transfer, whereas adiabatic film cooling effectiveness has narrow distribution.

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