Combination Effects of Upstream-Ramp and Swirling Coolant Flow on Film Cooling Characteristics

2015 ◽  
Author(s):  
Wenshuo Yang ◽  
Jian Pu ◽  
Jianhua Wang
Keyword(s):  
Film Cooling ◽  
Swirling Flow ◽  
Measurement Techniques ◽  
Large Angle ◽  
Vortex Pair ◽  
Structure Design ◽  
Coolant Flow ◽  
Impingement Angle ◽  
Interesting Phenomenon ◽  
Time Resolved

This paper presents an experimental investigation on the performances of a new film cooling structure design, in which a ramp is placed upstream of cylindrical film hole and a cylindrical cavity with two diagonal impingement holes is set at the inlet of the film hole to generate a swirling coolant flow entering the film hole. The experiments are carried out by two undisturbed measurement techniques, Planar Laser Induced Fluorescence (PLIF) and Time-Resolved Particle Image Velocimetry (TRPIV) in a water tunnel. The effects of the upstream-ramp angle, blowing ratio (BR) and coolant impingement angle on the film cooling performances of a flat plate are studied at three ramp angles (0°, 15° and 25°), two coolant swirling directions (clockwise and counter-clockwise), two impingement angles (15° and 30°), and three BRs (0.6, 1.0, and 1.4). The experimental results show that at high BRs, the combination structures of the upstream-ramp with the swirling coolant flow generated by the impingement angles can significantly improve film cooling performances; the best combination is at 30° impingement angle and 25° ramp angle. The reason can be explained by the fact that the swirling flow is significantly pressed onto wall through the upstream-ramp. Using the analogous analysis of heat and mass transfer, the adiabatic film effectiveness averaged over a cross section is obtained, and the analysis indicates that at high BRs, the combined effect of the a ramp with a large angle of 25° with 30° impingement angle can increase the film effectiveness up to 30% in comparison with the case without ramp at the exit of the film hole. The images captured by PLIF exhibit an interesting phenomenon, i.e. the swirling coolant in different directions can influence the counter vortex pair (CVP) in rotating layer, and the coolant swirling direction in clockwise enhances the right mixing of the CVP with coolant ejection, whereas the coolant swirling direction in counter-clockwise enhances the left mixing of the CVP with coolant ejection.

The Combined Effects of an Upstream Ramp and Swirling Coolant Flow on Film Cooling Characteristics

2016 ◽  
Vol 138 (11) ◽  
Author(s):  
Wenshuo Yang ◽  
Jian Pu ◽  
Jianhua Wang
Keyword(s):  
Film Cooling ◽  
Swirling Flow ◽  
Measurement Techniques ◽  
Large Angle ◽  
Vortex Pair ◽  
Structure Design ◽  
Coolant Flow ◽  
Test Case ◽  
Impingement Angle ◽  
Interesting Phenomenon

This paper presents an experimental investigation on the performances of a new film cooling structure design, in which a ramp is placed upstream of a cylindrical film hole and a cylindrical cavity with two diagonal impingement holes is set at the inlet of the film hole to generate a swirling coolant flow entering the film hole. The experiments are carried out by two undisturbed measurement techniques, planar laser induced fluorescence (PLIF) and time-resolved particle image velocimetry (TR-PIV) in a water tunnel. The effects of the upstream ramp angle, blowing ratio (BR), and coolant impingement angle on the film cooling performances of a flat plate are studied at three ramp angles (0 deg, 15 deg, and 25 deg), two coolant swirling directions (clockwise and counterclockwise), two impingement angles (15 deg and 30 deg), and three BRs (0.6, 1.0, and 1.4). The experimental results show that at high BRs, the combination structures of the upstream ramp with the swirling coolant flow generated by the impingement angles can significantly improve film cooling performances; the best combination is at a 30 deg impingement angle and a 25 deg ramp angle. This can be explained by the fact that the swirling flow is significantly pressed on to the wall by means of the upstream ramp. Using the analogous analysis of heat and mass transfer, the adiabatic film effectiveness averaged over a cross section is obtained; the analysis indicates that at high BRs, the combined effect of a ramp with a large angle of 25 deg with 30 deg impingement angle can increase the film effectiveness up to 30% when compared to the test case without a ramp at the exit of the film hole. The images captured by PLIF exhibit an interesting phenomenon, i.e., the swirling of the coolant in different directions can influence the counter vortex pair (CVP) in rotating layers, and the coolant swirling in a clockwise direction enhances the right mixing of the CVP with coolant ejection, whereas the coolant swirling in a counterclockwise direction enhances the left-mixing of the CVP with coolant ejection.

scholarly journals Experimental and Numerical Investigation of Sweeping Jet Film Cooling

2017 ◽  
Vol 140 (3) ◽  
Author(s):  
Mohammad A. Hossain ◽  
Robin Prenter ◽  
Ryan K. Lundgreen ◽  
Ali Ameri ◽  
James W. Gregory ◽  
...  
Keyword(s):  
Film Cooling ◽  
Thermal Field ◽  
Numerical Study ◽  
Convective Heat Transfer Coefficient ◽  
Density Ratio ◽  
Vortex Pair ◽  
Lateral Direction ◽  
Time Resolved ◽  
Jet In Crossflow ◽  
Cooling Hole

A companion experimental and numerical study was conducted for the performance of a row of five sweeping jet (SJ) film cooling holes consisting of conventional curved fluidic oscillators with an aspect ratio (AR) of unity and a hole spacing of P/D = 8.5. Adiabatic film effectiveness (η), thermal field (θ), convective heat transfer coefficient (h), and discharge coefficient (CD) were measured at two different freestream turbulence levels (Tu = 0.4% and 10.1%) and four blowing ratios (M = 0.98, 1.97, 2.94, and 3.96) at a density ratio of 1.04 and hole Reynolds number of ReD = 2800. Adiabatic film effectiveness and thermal field data were also acquired for a baseline 777-shaped hole. The SJ film cooling hole showed significant improvement in cooling effectiveness in the lateral direction due to the sweeping action of the fluidic oscillator. An unsteady Reynolds-averaged Navier–Stokes (URANS) simulation was performed to evaluate the flow field at the exit of the hole. Time-resolved flow fields revealed two alternating streamwise vortices at all blowing ratios. The sense of rotation of these alternating vortices is opposite to the traditional counter-rotating vortex pair (CRVP) found in a “jet in crossflow” and serves to spread the film coolant laterally.

Time-Resolved Flow Field Analysis of Effusion Cooling System With Representative Swirling Main Flow

2020 ◽  
Vol 142 (6) ◽  
Author(s):  
T. Lenzi ◽  
L. Palanti ◽  
A. Picchi ◽  
T. Bacci ◽  
L. Mazzei ◽  
...  
Keyword(s):  
Film Cooling ◽  
Swirling Flow ◽  
Cooling System ◽  
Life Time ◽  
Open Loop ◽  
Main Flow ◽  
Field Analysis ◽  
Ansys Fluent ◽  
Time Resolved ◽  
Film Development

Abstract Film-cooling jets behavior in a combustor chamber is deeply affected by swirling flow interactions and unsteadiness; on the other hand, the jets behavior has a direct impact on different phenomena such as cooling capabilities and ignition. For these reasons, an in-depth characterization of the film-cooling flows in the presence of a swirling main flow and demands dedicated time-resolved analyses. The experimental setup consists of a nonreactive single-sector linear combustor simulator installed in an open-loop wind tunnel. It is equipped with a swirler and a multiperforated plate to simulate the effusion cooling system of the liner. The rig is scaled with respect to the engine configuration to increase spatial resolution and to reduce the characteristic frequencies of the unsteady phenomena. Time-resolved particle image velocimetry (TRPIV) was exploited for the investigation testing different values of liner pressure drop. In addition, numerical investigations were carried out to gain a deeper insight of the behavior highlighted by the experiments and to assess the capability of computational fluid dynamics (CFD) in predicting the flow physics. In this work, the stress-blended eddy simulation (SBES) approach implemented in ansys fluent was adopted. Oscillations of the jets and intermittent interactions of the mainstream with the wall of the liner and hence with the film development have been investigated in detail. The results demonstrate how an unsteady analysis of the flow structures that characterize the jets, the turbulent mixing of coolant flows, and the interaction between mainstream and cooling jets is strictly necessary to have a complete knowledge of the behavior of the coolant, which in turn affects combustor operability and life time.

Experimental and Numerical Investigation of Sweeping Jet Film Cooling

2017 ◽  
Author(s):  
Mohammad A. Hossain ◽  
Robin Prenter ◽  
Ryan K. Lundgreen ◽  
Ali Ameri ◽  
James W. Gregory ◽  
...  
Keyword(s):  
Film Cooling ◽  
Thermal Field ◽  
Numerical Study ◽  
Convective Heat Transfer Coefficient ◽  
Density Ratio ◽  
Vortex Pair ◽  
Lateral Direction ◽  
Time Resolved ◽  
Jet In Crossflow ◽  
Cooling Hole

A companion experimental and numerical study was conducted of the performance of a row of 5 sweeping jet (SJ) film cooling holes consisting of conventional curved fluidic oscillators with an aspect ratio (AR) of unity and a hole spacing of P/D = 8.5. Adiabatic film effectiveness (η), thermal field (θ), convective heat transfer coefficient (h) and discharge coefficient (CD) were measured at two different freestream turbulence levels (Tu = 0.4% and 10.1%) and four blowing ratios (M = 0.98, 1.97, 2.94 and 3.96) at a density ratio (DR) of 1.04 and hole Reynolds number of ReD = 2800. Adiabatic film effectiveness and thermal field data were also acquired for a baseline 777-shaped hole. The sweeping jet film cooling hole showed significant improvement in cooling effectiveness in the lateral direction due to the sweeping action of the fluidic oscillator. An unsteady RANS simulation was performed to evaluate the flow field at the exit of the hole. Time resolved flow fields revealed two alternating streamwise vortices at all blowing ratios. The sense of rotation of these alternating vortices is opposite to the traditional counter rotating vortex pair (CRVP) found in a ‘jet in crossflow’ and serves to spread the film coolant laterally.

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.

scholarly journals Unsteady Flow Field Characterization of Effusion Cooling Systems with Swirling Main Flow: Comparison Between Cylindrical and Shaped Holes

Energies ◽  
2020 ◽  
Vol 13 (19) ◽  
pp. 4993
Author(s):  
Tommaso Lenzi ◽  
Alessio Picchi ◽  
Tommaso Bacci ◽  
Antonio Andreini ◽  
Bruno Facchini
Keyword(s):  
Flow Field ◽  
Film Cooling ◽  
Gas Turbines ◽  
Swirling Flow ◽  
Cooling System ◽  
Complete Characterization ◽  
Time Resolved ◽  
Staggered Arrangement ◽  
Unsteady Characteristics

The presence of injectors with strongly swirled flows, used to promote flame stability in the combustion chambers of gas turbines, influences the behaviour of the effusion cooling jets and consequently of the liner’s cooling capabilities. For this reason, unsteady behaviour of the jets in the presence of swirling flow requires a characterization by means of experimental flow field analyses. The experimental setup of this work consists of a non-reactive single-sector linear combustor test rig, scaled up with respect to the real engine geometry to increase spatial resolution and to reduce the frequencies of the unsteadiness. It is equipped with a radial swirler and multi-perforated effusion plates to simulate the liner cooling system. Two effusion plates were tested and compared: with cylindrical and with laid-back fan-shaped 7-7-7 holes in staggered arrangement. Time resolved Particle Image Velocimetry has been carried out: the unsteady characteristics of the jets, promoted by the intermittent interactions with the turbulent mainstream, have been investigated as their vortex structures and turbulent decay. The results demonstrate how an unsteady analysis is necessary to provide a complete characterization of the coolant behaviour and of its turbulent mixing with mainflow, which affect, in turn, the film cooling capability and liner’s lifetime.

Scaling Considerations for Thermal and Pressure Sensitive Paint Methods Used to Determine Adiabatic Effectiveness

2020 ◽  
Author(s):  
Luke J. McNamara ◽  
Jacob P. Fischer ◽  
James L. Rutledge ◽  
Marc D. Polanka
Keyword(s):  
Mass Transfer ◽  
Flow Rate ◽  
Film Cooling ◽  
Heat Mass Transfer ◽  
Measurement Techniques ◽  
Experimental Methods ◽  
Coolant Flow ◽  
Coolant Flow Rate ◽  
Pressure Sensitive ◽  
Adiabatic Effectiveness

Abstract To be representative of engine conditions, a measurement of film cooling behavior on an experimental model must have certain nondimensional parameters matched, such as the freestream Reynolds number. However, the coolant flow rate must also be properly scaled between the low temperature tests and engine temperatures to accurately predict film cooling effectiveness. This process is complicated by gas property variation with temperature. Additionally, selection of the appropriate coolant flow rate parameter to scale from low to high temperatures is a topic of continued uncertainty. Furthermore, experiments are commonly conducted using thermal measurement techniques with infrared thermography (IR) but the use of pressure sensitive paints (PSPs) implementing the heat-mass transfer analogy is also common. Thus, the question arises of how the adiabatic effectiveness distributions compare between mass transfer experimental methods and thermal experimental methods and whether these two methods are sensitive to coolant flow rate parameters in different ways. In this study, a thermal technique with IR was compared to a heat-mass transfer method with a PSP on a flat plate model with a 7-7-7 film cooling hole. While adiabatic effectiveness is best scaled by accounting for specific heats with the advective capacity ratio (ACR) using thermal techniques, results revealed that PSP measurements are scaled best with the mass flux ratio (M). The difference in these methods has significant implications for engine designers that rely on PSP experimental data to predict engine thermal behavior as PSP is fundamentally not sensitive to the same highly relevant physical mechanisms to which thermal methods are sensitive.

Magnetic Resonance Imaging Studies of Flow and Mixing for Single-Hole Film Cooling

2011 ◽  
Author(s):  
Emin Issakhanian ◽  
Chris J. Elkins ◽  
John K. Eaton
Keyword(s):  
Magnetic Resonance Imaging ◽  
Magnetic Resonance ◽  
Film Cooling ◽  
Measurement Techniques ◽  
Vortex Pair ◽  
Secondary Flows ◽  
Resonance Imaging ◽  
Mean Velocity ◽  
Film Cooling Effectiveness ◽  
Cooling Hole

Magnetic resonance imaging (MRI) measurement techniques are used to reveal the coupled 3D velocity and coolant concentration fields for a single film cooling hole with L/D of 4, ejection angle of 60°, and blowing ratios of 0.5 and 1. The jet exits into a boundary layer with momentum thickness of 0.1D. Magnetic resonance velocimetry (MRV) measures 3 component mean velocity everywhere within the channel, cooling hole, and feed plenum. Magnetic resonance concentration (MRC) provides the coolant concentration distribution which is directly analogous to film cooling effectiveness. The coupled velocity and concentration show that high velocity ratios lead to a detached jet which lowers effectiveness. Vorticity from the feed hole creates a streamwise oriented counter rotating vortex pair which lifts the coolant stream from the surface and sweeps in main channel flow inducing a kidney-shape to the coolant jet cross-section. Without the need for optical access, MRV allows study of the flow inside the feed hole including the entrance separation and secondary flows. Cross-stream feeding of the cooling hole shows added spanwise asymmetry at the hole entrance, but this asymmetry is significantly reduced moving up the hole.

Time-Resolved Flow Field Analysis of Effusion Cooling System With Representative Swirling Main Flow

2019 ◽  
Author(s):  
T. Lenzi ◽  
L. Palanti ◽  
A. Picchi ◽  
T. Bacci ◽  
L. Mazzei ◽  
...  
Keyword(s):  
Film Cooling ◽  
Swirling Flow ◽  
Cooling System ◽  
Life Time ◽  
Open Loop ◽  
Field Analysis ◽  
Ansys Fluent ◽  
Time Resolved ◽  
Eddy Simulation ◽  
Film Development

Abstract Film cooling jets behaviour in a combustor chamber is deeply affected by swirling flow interactions and unsteadiness; on the other hand, the jets behaviour has a direct impact on different phenomena such as cooling capabilities and ignition. For these reasons, an in-depth characterization of the film-cooling flows in the presence of a swirling mainflow, demands dedicated time-resolved analyses. The experimental setup consists of a non-reactive single-sector linear combustor simulator installed in an open loop wind tunnel. It is equipped with a swirler and a multiperforated plate to simulate the effusion cooling system of the liner. The rig is scaled with respect to the engine configuration, to increase spatial resolution and to reduce the characteristic frequencies of the unsteady phenomena. Time-Resolved Particle Image Velocimetry (TRPIV) was exploited for the investigation testing different values of liner pressure drop. In addition, numerical investigations were carried out to gain a deeper insight of the behaviour highlighted by the experiments and to assess the capability of CFD in predicting the flow physics. In this work, the Stress-Blended Eddy Simulation (SBES) approach implemented in ANSYS Fluent was adopted. Oscillations of the jets and intermittent interactions of the mainstream with the wall of the liner and hence with the film development have been investigated in detail. The results demonstrate how an unsteady analysis of the flow structures that characterize the jets, the turbulent mixing of coolant flows and the interaction between mainstream and cooling jets is strictly necessary to have a complete knowledge of the behaviour of the coolant which in turn affects combustor operability and life-time.

Numerical simulation of swirling flow effect on the first stage vane film cooling distribution

2016 ◽  
Vol 07 (03) ◽  
pp. 1650031
Author(s):  
Hong Yin
Keyword(s):  
Flow Field ◽  
Film Cooling ◽  
Swirling Flow ◽  
Cooling System ◽  
Leading Edge ◽  
Suction Side ◽  
Local Area ◽  
Swirl Flow ◽  
Flow Effect ◽  
Recirculation Flow

In advanced gas turbine technology, lean premixed combustion is an effective strategy to reduce peak temperature and thus, NO[Formula: see text] emissions. The swirler is adopted to establish recirculation flow zone, enhancing mixing and stabilizing the flame. Therefore, the swirling flow is dominant in the combustor flow field and has impact on the vane. This paper mainly investigates the swirling flow effect on the turbine first stage vane cooling system by conducting a group of numerical simulations. Firstly, the numerical methods of turbulence modeling using RANS and LES are compared. The computational model of one single swirl flow field is considered. Both the RANS and LES results give reasonable recirculation zone shape. When comparing the velocity distribution, the RANS results generally match the experimental data but fail to at some local area. The LES modeling gives better results and more detailed unsteady flow field. In the second step, the RANS modeling is incorporated to investigate the vane film cooling performance under the swirling inflow boundary condition. According to the numerical results, the leading edge film cooling is largely altered by the swirling flow, especially for the swirl core-leading edge aligned case. Compared to the pressure side, the suction side film cooling is more sensitive to the swirling flow. Locally, the film cooling jet is lifted and turned by the strong swirling flow.

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