Experimental Study of the Endwall Heat Transfer of a Transonic Nozzle Guide Vane With Upstream Jet Purge Cooling: Part 1 — Effect of Density Ratio

2020 ◽  
Author(s):  
Shuo Mao ◽  
Ridge A. Sibold ◽  
Stephen Lash ◽  
Wing F. Ng ◽  
Hongzhou Xu ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Mass Flux ◽  
Guide Vane ◽  
Density Ratio ◽  
Momentum Ratio ◽  
Blowing Ratio ◽  
Nozzle Guide Vane ◽  
Nozzle Guide ◽  
The Impact

Abstract Nozzle guide vane platforms often employ complex cooling schemes to mitigate ever-increasing thermal loads on endwall. Understanding the impact of advanced cooling schemes amid the highly complex three-dimensional secondary flow is vital to engine efficiency and durability. This study analyzes and describes the effect of coolant to mainstream blowing ratio, momentum ratio and density ratio for a typical axisymmetric converging nozzle guide vane platform with an upstream doublet staggered, steep-injection, cylindrical hole jet purge cooling scheme. Nominal flow conditions were engine representative and as follows: Maexit = 0.85, Reexit/Cax = 1.5 × 106 and an inlet large-scale freestream turbulence intensity of 16%. Two blowing ratios were investigated, each corresponding to upper and lower engine extrema at M = 3.5 and 2.5, respectively. For each blowing ratio, the coolant to mainstream density ratio was varied between DR = 1.2, representing typical experimental neglect of coolant density, and DR = 1.95, representative of typical engine conditions. An optimal coolant momentum ratio between = 6.3 and 10.2 is identified for in-passage film effectiveness and net heat flux reduction, at which the coolant suppresses and overcomes secondary flows but imparts minimal turbulence and remains attached to endwall. Progression beyond this point leads to cooling effectiveness degradation and increased endwall heat flux. Endwall heat transfer does not scale well with one single parameter; increasing with increasing mass flux for the low density case but decreasing with increasing mass flux of high density coolant. From the results gathered, both coolant to mainstream density ratio and blowing ratio should be considered for accurate testing, analysis and prediction of purge jet cooling scheme performance.

EXPERIMENTAL STUDY OF THE ENDWALL HEAT TRANSFER OF A TRANSONIC NOZZLE GUIDE VANE WITH UPSTREAM JET PURGE COOLING PART 2 - EFFECT OF COMBUSTOR-NGV MISALIGNMENT

2021 ◽  
pp. 1-34
Author(s):  
Shuo Mao ◽  
Ridge A. Sibold ◽  
Wing Ng ◽  
Zhigang LI ◽  
Bo Bai ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Guide Vane ◽  
Density Ratio ◽  
Cooling Performance ◽  
Blowing Ratio ◽  
Turbine Inlet ◽  
Passage Vortex ◽  
Nozzle Guide Vane ◽  
Lift Off ◽  
Nozzle Guide

Abstract A misalignment between the combustor exit and the nozzle guide vane (NGV) platform commonly exists due to manufacturing tolerances and thermal transience. This study investigated, experimentally and computationally, the effect of the combustor-turbine misalignment on the heat transfer for an axisymmetric converging endwall with a jet purge cooling scheme at transonic conditions. The studies were conducted at engine-representative Maexit = 0.85, inlet turbulence intensity of 16%, Reexit,Cax = 1.5×106. A film cooling blowing ratio of 2.5 (design condition) and 3.5 and an engine-representative density ratio of 1.95 were used in the study. Three various step misalignments, combustor exit being 4.9% span higher than turbine inlet (backward-facing), no step (baseline), and combustor exit being 4.9% span lower than turbine inlet (forward-facing), were tested to demonstrate the misalignment effect on endwall heat transfer. Results indicated that the step misalignment affects the cooling performance by altering the interaction between the coolant and the cavity vortex, horseshoe vortex, and passage vortex. At the design blowing ratio of 2.5, the backward-facing step leads to increased coolant dissipation, causing the coolant to be later dominated by the passage vortex and leading to poor cooling performance. Meanwhile, a forward-facing step induced more coolant lift-off. At the blowing ratio of 3.5, the additional momentum ensures that enough coolant enters the passage to form a stable boundary layer. Therefore, the step misalignment no longer has a first-order effect.

Effect of Blowing Ratio on the Internal Heat Transfer of a Cooled Nozzle Guide Vane in a Linear Cascade

2016 ◽  
Vol 8 (4) ◽  
Author(s):  
Arun Kumar Pujari ◽  
B. V. S. S. S. Prasad ◽  
Nekkanti Sitaram
Keyword(s):  
Heat Transfer ◽  
Surface Temperature ◽  
Guide Vane ◽  
Internal Heat ◽  
Internal Surface ◽  
Blowing Ratio ◽  
Computational Data ◽  
Nozzle Guide Vane ◽  
Nozzle Guide ◽  
Internal Heat Transfer

Experimental and computational heat transfer investigations are reported on the interior side of a nozzle guide vane (NGV) subjected to combined impingement and film cooling. The domain of study is a two-dimensional five-vane cascade having a space chord ratio of 0.88. The vane internal surface is cooled by dry air, supplied through the two impingement inserts: the front and the aft. The blowing ratio (ρcVc/ρmVm) is varied systematically by varying the coolant mass flow through the impingement chamber and also by changing the mainstream Reynolds number, but by keeping a fixed spacing (H) to jet diameter (d) ratio of 1.2. The surface temperature distributions, at certain locations of the vane interior surface, are measured by pasting strips of liquid crystal sheets. The vane interior surface temperature distribution is also obtained by the computations carried out by using shear stress transport (SST) k–ω turbulence model in the flow solver ansys fluent-14. The computational data are in good agreement with the measured values of temperature. The internal heat transfer coefficients are thence determined from the computational data. The results show that, when the blowing ratio is increased by increasing the coolant flow rate, the average internal surface temperature decreases. However, when the blowing ratio is varied by increasing the mainstream Reynolds number, the internal surface temperature increases. Further, the temperature variations are different all along the internal surface from the leading edge to the trailing edge and are largely dependent on the coolant flow distributions on the internal as well as the external sides.

EXPERIMENTAL STUDY OF THE ENDWALL HEAT TRANSFER OF A TRANSONIC NOZZLE GUIDE VANE WITH UPSTREAM JET PURGE COOLING PART 1 - EFFECT OF DENSITY RATIO

2021 ◽  
pp. 1-36
Author(s):  
Shuo Mao ◽  
Ridge A. Sibold ◽  
Wing Ng ◽  
Zhigang LI ◽  
Bo Bai ◽  
...  
Keyword(s):  
Large Scale ◽  
Guide Vane ◽  
Flow Direction ◽  
Density Ratio ◽  
Leading Edge ◽  
Horseshoe Vortex ◽  
Vital Role ◽  
Blowing Ratio ◽  
Nozzle Guide Vane ◽  
Nozzle Guide

Abstract Nozzle guide vane platforms often employ complex cooling schemes to mitigate the ever-increasing thermal loads on endwall. This study analyzes, experimentally and numerically, and describes the effect of coolant to mainstream blowing ratio, momentum ratio and density ratio for a typical axisymmetric converging nozzle guide vane platform with an upstream doublet staggered, steep-injection, cylindrical hole purge cooling scheme. Nominal flow conditions were engine-representative and as follows: Maexit = 0.85, Reexit,Cax = 1.5×106 and an inlet large-scale freestream turbulence intensity of 16%. Two blowing ratios were investigated, each corresponding to the design condition and its upper extrema at M = 2.5 and 3.5, respectively. For each blowing ratio, the coolant to mainstream density ratio was varied between DR=1.2, representing typical experimental neglect of coolant density, and DR=1.95, representative of typical engine conditions. The results show that with a fixed coolant-to-mainstream blowing ratio, the density ratio plays a vital role in the coolant-mainstream mixing and the interaction between coolant and horseshoe vortex near the vane leading edge. A higher density ratio leads to a better coolant coverage immediately downstream of the cooling holes but exposes the in-passage endwall near the pressure side. It also causes the in-passage coolant coverage to decay at a higher rate in the flow direction. From the results gathered, both density ratio and blowing ratio should be considered for accurate testing, analysis, and prediction of purge jet cooling scheme performance.

A Converging Slot-Hole Film-Cooling Geometry—Part 2: Transonic Nozzle Guide Vane Heat Transfer and Loss

2002 ◽  
Vol 124 (3) ◽  
pp. 461-471 ◽  
Author(s):  
J. E. Sargison ◽  
S. M. Guo ◽  
M. L. G. Oldfield ◽  
G. D. Lock ◽  
A. J. Rawlinson
Keyword(s):  
Heat Transfer ◽  
Film Cooling ◽  
Guide Vane ◽  
Density Ratio ◽  
Wide Band ◽  
Nozzle Guide Vane ◽  
Cooling Hole ◽  
Hole Geometry ◽  
Temperature Levels ◽  
Nozzle Guide

This paper presents the first experimental measurements on an engine representative nozzle guide vane, of a new film-cooling hole geometry, a con¯vergings¯lot-hole¯ or console. The patented console geometry is designed to improve the heat transfer and aerodynamic performance of turbine vane and rotor blade cooling systems. These experiments follow the successful validation of the console design in low-speed flat-plate tests described in Part 1 of this paper. Stereolithography was used to manufacture a resin model of a transonic, engine representative nozzle guide vane in which seven rows of previously tested fan-shaped film-cooling holes were replaced by four rows of consoles. This vane was mounted in the annular vane ring of the Oxford cold heat transfer tunnel for testing at engine Reynolds numbers, Mach numbers and coolant to mainstream momentum flux ratios using a heavy gas to simulate the correct coolant to mainstream density ratio. Heat transfer data were measured using wide-band thermochromic liquid crystals and a modified analysis technique. Both surface heat transfer coefficient and the adiabatic cooling effectiveness were derived from computer-video records of hue changes during the transient tunnel run. The cooling performance, quantified by the heat flux at engine temperature levels, of the console vane compares favourably with that of the previously tested vane with fan-shaped holes. The new console film-cooling hole geometry offers advantages to the engine designer due to a superior aerodynamic efficiency over the fan-shaped hole geometry. These efficiency measurements are demonstrated by results from midspan traverses of a four-hole pyramid probe downstream of the nozzle guide vane.

Effect of Nozzle Guide Vane Lean Under Influence of Inlet Temperature Traverse

2013 ◽  
Vol 136 (7) ◽  
Author(s):  
A. Rahim ◽  
B. Khanal ◽  
L. He ◽  
E. Romero
Keyword(s):  
Heat Transfer ◽  
Guide Vane ◽  
Tangential Displacement ◽  
Inlet Temperature ◽  
Heat Transfer Characteristics ◽  
Transfer Characteristics ◽  
Nozzle Guide Vane ◽  
Nozzle Guide ◽  
Hot Streak ◽  
The Impact

One of the most widely studied parameters in turbine blade shaping is blade lean, i.e., the tangential displacement of spanwise sections. However, there is a lack of published research that investigates the effect of blade lean under nonuniform temperature conditions (commonly referred to as a “hot-streak”) that are present at the combustor exit. Of particular interest is the impact of such an inflow temperature profile on heat transfer when the nozzle guide vane (NGV) blades are shaped. In the present work, a computational study has been carried out for a transonic turbine stage using an efficient unsteady Navier–Stokes solver (HYDRA). The configurations with a nominal vane and a compound leaned vane under uniform and hot-streak inlet conditions are analyzed. After confirming the typical NGV loading and aeroloss redistributions as seen in previous literature on blade lean, the focus has been directed to the rotor aerothermal behavior. While the overall stage efficiencies for the configurations are largely comparable, the results show strikingly different rotor heat transfer characteristics. For a uniform inlet, a leaned NGV has a detrimental effect on the rotor heat transfer. However, once the hot-streak is introduced, the trend is reversed; the leaned NGV leads to favorable heat transfer characteristics in general and for the rotor tip region in particular. The possible causal links for the observed aerothermal features are discussed. The present findings also highlight the significance of evaluating NGV shaping designs under properly conditioned inflow profiles, rather than extrapolating the wisdom derived from uniform inlet cases. The results also underline the importance of including rotor heat transfer and coolability during the NGV design process.

Experimental Study of the Endwall Heat Transfer of a Transonic Nozzle Guide Vane With Upstream Jet Purge Cooling: Part 2 — Effect of Combustor-NGV Misalignment

2020 ◽  
Author(s):  
Ridge A. Sibold ◽  
Shuo Mao ◽  
Wing F. Ng ◽  
Hongzhou Xu ◽  
Michael Fox
Keyword(s):  
Heat Transfer ◽  
Film Cooling ◽  
Guide Vane ◽  
Backward Facing Step ◽  
Cooling Effectiveness ◽  
Blowing Ratio ◽  
Nozzle Guide Vane ◽  
Forward Facing Step ◽  
Lift Off ◽  
Nozzle Guide

Abstract A misalignment between the combustor exit and the nozzle guide vane (NGV) platform commonly exists due to manufacturing tolerances and thermal transience. This study experimentally investigated the effect of the combustor-turbine misalignment on the heat transfer for an axisymmetric converging endwall with a jet purge cooling scheme at transonic conditions. Tests were conducted at engine-representative freestream exit Mach number of 0.85, inlet turbulence intensity of 16%, film cooling blowing ratio of 2.5 (design condition) and 3.5, and density ratio of 1.95. Three different step misalignments, combustor exit 4.9% span higher than turbine inlet (backward-facing), no step (baseline), and combustor exit 4.9% span lower than turbine inlet (forward-facing), were tested to demonstrate the misalignment effect on endwall Nusselt number, adiabatic film cooling effectiveness, and net heat flux reduction. A supportive numerical simulation was conducted to provide insight into the flow field. Experimental and numerical results indicated a blowing ratio of 2.5 amid a backward-facing step leads to more turbulent mixing between the coolant and mainstream due to the horseshoe vortex and step-induced cavity vortex, reducing coolant coverage and adversely affecting coolant performance. For the same blowing ratio, a forward-facing step induced more lift-off and shifted the coverage downstream and toward the pressure side, ultimately slightly enhancing the cooling performance. Nevertheless, the forward-facing step leads to a large cooling effectiveness gradient in the pitch-wise direction. At a blowing ratio of 3.5, the baseline no-step case provided superior coolant performance, however, the effect of the step was much less significant as compared to the lower blowing case. The forward-facing step amid a blowing ratio of 3.5 results in severe jet lift-off, diminishing the returns traditionally associated with increasing coolant mass flow. Based on this study, a backward-facing step should be avoided to prevent endwall burnout in the nozzle guide. Additionally, a forward-facing step should be avoided, especially amid high blowing ratios.

A Converging Slot-Hole Film-Cooling Geometry: Part 2 — Transonic Nozzle Guide Vane Heat Transfer and Loss

2001 ◽  
Author(s):  
J. E. Sargison ◽  
S. M. Guo ◽  
M. L. G. Oldfield ◽  
G. D. Lock ◽  
A. J. Rawlinson
Keyword(s):  
Heat Transfer ◽  
Film Cooling ◽  
Guide Vane ◽  
Density Ratio ◽  
Wide Band ◽  
Nozzle Guide Vane ◽  
Cooling Hole ◽  
Hole Geometry ◽  
Temperature Levels ◽  
Nozzle Guide

This paper presents the first experimental measurements on an engine representative nozzle guide vane, of a new film cooling hole geometry, a Converging Slot-Hole or Console. The patented console geometry is designed to improve the heat transfer and aerodynamic performance of turbine vane and rotor blade cooling systems. These experiments follow the successful validation of the console design in low-speed flat-plate tests described in Part 1 of this paper (Sargison et al [1]). Stereolithography was used to manufacture a resin model of a transonic, engine representative nozzle guide vane in which 7 rows of previously tested fan-shaped film-cooling holes were replaced by 4 rows of consoles. This vane was mounted in the annular vane ring of the Oxford Cold Heat Transfer Tunnel for testing at engine Reynolds numbers, Mach numbers and coolant to mainstream momentum flux ratios using a heavy gas to simulate the correct coolant to mainstream density ratio. Heat transfer data were measured using wide band thermochromic liquid crystals and a modified analysis technique. Both surface heat transfer coefficient and the adiabatic cooling effectiveness were derived from computer-video records of hue changes during the transient tunnel run. The cooling performance, quantified by the heat flux at engine temperature levels, of the console vane compares favourably with that of the previously tested vane with fan-shaped holes. The new console film cooling hole geometry offers advantages to the engine designer due to a superior aerodynamic efficiency over the fan-shaped hole geometry. These efficiency measurements are demonstrated by results from mid span traverses of a four hole pyramid probe downstream of the nozzle guide vane.

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