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.

Heat Transfer Studies on the Interior Surfaces of Cooled Nozzle Guide Vane in a Linear Cascade

2015 ◽  
Author(s):  
Arun Kumar Pujari ◽  
Bhamidi Prasad ◽  
Nekkanti Sitaram
Keyword(s):  
Heat Transfer ◽  
Surface Temperature ◽  
Guide Vane ◽  
Internal Heat ◽  
Leading Edge ◽  
Internal Surface ◽  
Transfer Coefficients ◽  
Computational Data ◽  
Nozzle Guide Vane ◽  
Nozzle Guide

Experimental and computational heat transfer investigations are reported in 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 four passages. Each vane has a chord length of 228 mm and the pitch distance between the vanes is 200 mm. The vane internal surface is cooled by dry air supplied through the two impingement inserts: the front and the aft. The mass flow through the impingement chamber is varied, for a fixed spacing (H) to jet diameter (d) ratio of 1.2. The surface temperature distributions, at certain locations of the vane interior, are measured by pasting strips of liquid crystal sheets. The vane interior surface temperature distribution is also obtained by computations carried out by using Shear stress transport (SST) k-ω turbulence model in the ANSY FLUENT-14 flow solver. The computational data are in good agreement with the measured values of temperature. The internal heat transfer coefficients are thence determined along the leading edge and the mid span region from the computational data.

An Internal Heat Transfer Study in a Cooled Nozzle Guide Vane of a Linear Cascade

2014 ◽  
Author(s):  
Arun Kumar Pujari ◽  
Prasad B. V. S. S. Subrahmanyaa ◽  
Sitaram Nekkanti
Keyword(s):  
Heat Transfer ◽  
Surface Temperature ◽  
Film Cooling ◽  
Guide Vane ◽  
Internal Heat ◽  
Leading Edge ◽  
Internal Surface ◽  
Structure Variation ◽  
Nozzle Guide Vane ◽  
Nozzle Guide

Experimental and computational heat transfer investigations are reported in the interior mid span of the pressure surface of a Nozzle Guide Vane (NGV) subjected to combined impingement and film cooling. The study is carried out by considering a two dimensional cascade domain having four passages formed between the five vane each has a chord length of 228 mm and spacing (between the blades) of 200 mm. The vane internal surface is cooled by two impingement inserts namely front and aft impingement tubes. The front impingement tube is used to cool the internal side of the leading edge of the NGV whereas the aft impingement tube is used to cool mainly the mid span of the internal surface. The mass flow through the impingement chamber is varied for a fixed target plate distance to jet diameter ratio of 1.12. The surface temperature at the mid chord region was measured by liquid crystal technique. The surface temperature obtained from both experiments and computations are compared and the computationally obtained average heat transfer coefficient distribution along chord reported. The flow structure variation along the chord and its effect on Nusselt number distribution is presented. The computation is carried out by using Shear stress transport (SST) k-ω turbulence model in the ANSY FLUENT-14 flow solver.

Conjugate Heat Transfer Analysis on the Interior Surface of Nozzle Guide Vane with Combined Impingement and Film Cooling

2020 ◽  
Vol 37 (4) ◽  
pp. 327-342
Author(s):  
Arun Kumar Pujari ◽  
B. V. S. S. S Prasad ◽  
Nekkanti Sitaram
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Surface Temperature ◽  
Film Cooling ◽  
Conjugate Heat Transfer ◽  
Guide Vane ◽  
Internal Surface ◽  
Conducting Material ◽  
Nozzle Guide Vane ◽  
Nozzle Guide

AbstractThe effect of conjugate heat transfer is investigated on a first stage nozzle guide vane (NGV) of a high pressure gas turbine which has both impingement and film cooling holes. The study is carried out computationally by considering a linear cascade domain, having two passages formed between the vanes, with a chord length of 228 mm and spacing of 200 mm. The effect of (i) coolant and mainstream Reynolds numbers, (ii) thermal conductivity (iii) temperature difference between the mainstream and coolant at the internal surface of the nozzle guide vane are investigated under conjugate thermal condition. The results show that, with increasing coolant Reynolds number the lower conducting material shows larger percentage decrease in surface temperature as compared to the higher conducting material. However, the internal surface temperature is nearly independent of mainstream Reynolds number variation but shows significant variation for higher conducting material. Further, the temperature gradient within the solid thickness of NGV is higher for the lower conductivity material.

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.

Effect of Thermal Conductivity on Nozzle Guide Vane Internal Surface Temperature Distribution

2018 ◽  
Vol 0 (0) ◽  
Author(s):  
Arun Kumar Pujari ◽  
B. V. S. S. S Prasad ◽  
Nekkanti Sitaram
Keyword(s):  
Temperature Distribution ◽  
Surface Temperature ◽  
Guide Vane ◽  
Leading Edge ◽  
Internal Surface ◽  
Temperature Data ◽  
Heat Transfer Analysis ◽  
Surface Temperature Distribution ◽  
Nozzle Guide Vane ◽  
Nozzle Guide

Abstract Conjugate heat transfer analysis is carried out in a cascade domain for a nozzle guide vane. The nozzle guide vane is internally cooled by jet impingement cooling, and the external surface is cooled by film cooling. A computational study was carried out with three different materials, having conductivity values of 0.0048, 0.2 and 1.1 W/m.K. Distribution of local surface temperature along the leading edge, pressure and suction surface is reported. The leading edge region showed the maximum increase in internal surface temperature as the conductivity increased among the different regions of the vane internal surface. However, the pressure and suction surfaces showed relatively less increase in the surface temperature distribution. In order to validate the computational result, the obtained temperature data were compared with experimentally obtained surface temperature data. The flow phenomena like jet lift-off and self-induced cross-flow affect the local temperature distribution differently in the three materials. For a constant mainstream and coolant flow, the surface temperature gradient is higher for the lower conductivity material, and the gradient decreases as conductivity increases. Hence, a material with higher conductivity is desired in a combined impingement and film cooled nozzle guide vane, to increase the durability of the vane.

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.

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.

CFD Study of Combined Impingement and Film Cooling Flow on the Internal Surface Temperature Distribution of a Vane

2019 ◽  
Vol 0 (0) ◽  
Author(s):  
Arun Kumar Pujari
Keyword(s):  
Reynolds Number ◽  
Surface Temperature ◽  
Film Cooling ◽  
Guide Vane ◽  
Cross Flow ◽  
Internal Surface ◽  
Flow Reynolds Number ◽  
Nozzle Guide Vane ◽  
Lift Off ◽  
Nozzle Guide

Abstract Conjugate heat transfer analysis is carried out on the internal surface of the first-stage nozzle guide vane of a gas turbine, which has both impingement and film cooling holes. The mainstream flow Reynolds number and internal coolant flow Reynolds number systematically changed and its effect on internal local surface temperature variation is studied. It is found that an increase in the coolant mass flow rate causes a non-uniform decrease in the local internal surface temperature. The external film coolant jet-lift off and internal impingement cross-flow are significant contributors to the non-uniform variation in surface temperature. It is also observed that the leading edge regions are prone to jet lift-off, whereas the tip regions of the suction surface are prone to self-induced cross-flow, due to which hot patches are formed in these regions. Hot patches are observed near the hub regions of a pressure surface due to the reduced film thickness on the external surface. From these observations it is concluded that local values of internal surface temperature are differently affected in different regions of the vane surface for a given combination of mainstream and coolant flow rates. Therefore, the conventional method of obtaining the internal temperature distributions by considering generalized geometries may not yield accurate solutions, in predicting the life of the nozzle guide vane.

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