A computational investigation is carried out to study the flow and heat transfer from a row of circular jets impinging on a concave surface. The computational domain simulates the impingement cooling zone of a gas turbine nozzle guide vane. The parameters which are varied in the study include jet Reynolds number (Red=5000 to 54000). inter-jet distance to jet diameter ratio (c/d = 3.33 and 4.67) and target plate distance to jet diameter ratio (h/d=1, 3 and 4). The flow field, predicted with K- ω turbulence model (using Fluent 6.2), is characterized with the presence of a pair of counter rotating vortices, an upwash fountain flow and entrainment. The local pressure coefficient and Nusselt number variations along the concave plate are presented and these values are found to under predict the some available experimental data by about 12%. Copyright © 2006 by ASME.

B. V.S.S.S. Prasad

Department of Mechanical Engineering

Bhuvanesh V.N.Rama Kumar

CIRCULAR JETS

CONCAVE SURFACES

NUSSELT NUMBER DISTRIBUTION

Turbulence models

Computational methods

Gas turbines

Heat transfer

Reynolds number

Surface phenomena

Turbulence

Vortex flow

Jets

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IIT Madras

Computational Investigation of Flow and Heat Transfer for a Row of Circular Jets Impinging on a Concave Surface

Proceedings of the ASME Turbo Expo

In the present study, a flow visualization and heat transfer investigation is carried out computationally on a flat plate with 10x1 array of impinging jets from a corrugated plate. This corrugated structure is an Anti-Cross Flow (ACF) technique which is proved to nullify the negative effects of cross-flow thus enhancing the overall cooling performance. Governing equations are solved using k-? Shear Stress Transport (SST) turbulence model in commercial code FLUENT. The parameter variation considered for the present study are (i) three different heights of ACF corrugate (C/D=1, 2 & 3) and (ii) two different jet-to-target plate spacing (H/D=1 & 2). The dependence of ACF structure performance on the corrugate height (C/D) and the flow structure has been discussed in detail, therefore choosing an optimum corrugate height and visualizing the threedimensional flow phenomena are the main objectives of the present study. The three-dimensional flow separation and heat transfer characteristics are explained with the help of skin friction lines, upwash fountains, wall eddies, counter-rotating vortex pair (CRVP), and plots of Nusselt number. It is found that the heat transfer performance is high at larger corrugate heights for both the jet-to-plate spacing. Moreover, the deterioration of the skin friction pattern corresponding to the far downstream impingement zones is greatly reduced with ACF structure, retaining more uniform heat transfer pattern even at low H/D values where the crossflow effects are more dominant in case of the conventional cooling structure. In comparison of the overall heat transfer performance the difference between C/D=3 & C/D=2 for H/D=2 is significantly less, thus making the later as the optimal configuration in terms of reduced channel height. Copyright © 2017 ASME.

Fulltext

ASME 2017 Heat Transfer Summer Conference, HT 2017

Computational study of flow and heat transfer with anti cross flows (ACF) jet impingement cooling for different heights of corrugate

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-A.A. 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. [DOI: 10.1115/1.4034057]. © 2016 by ASME.

Journal of Thermal Science and Engineering Applications

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

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 l°Cations 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-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. © Copyright 2015 by ASME.

Heat transfer studies on the interior surfaces of cooled nozzle guide vane in a linear cascade

A computational study on conjugate heat transfer is carried out to present the behavior of nondimensional temperature and heat transfer coefficient of a Nozzle Guide Vane (NGV) leading edge. Reynolds number of both mainstream flow and coolant impinging jets are varied. The NGV has five rows of film cooling holes arranged in shower head manner and four rows of impingement holes arranged in staggered manner. The results are presented by considering materials of different thermal conductivity. The results show that the mainstream flow affects the temperature distribution on the interior side of the vane leading edge for high conductivity material whereas it has negligible effects for low conductivity material. The effect of changing blowing ratio on internal heat transfer coefficient and internal surface temperature is also presented. © 2014 Arun Kumar Pujari et al.

International Journal of Rotating Machinery

Conjugate heat transfer study at interior surface of NGV leading edge with combined shower head and impingement cooling

A computational study is reported on flow and heat transfer from a single row of circular air jets impinging on a concave surface with either one or two rows of effusion holes or without effusion holes. The effects of arrangement of jet orifices and effusion holes, spent air exit closure configurations, H/D ratio and jet Reynolds number are investigated. The pressure distribution is higher for the configuration with the air exit only through effusion holes. At higher Reynolds number, three peaks in local Nusselt number are identified and explained. Among the cases tested, the configuration with a single row of inline effusion holes shows the least heat transfer and there is a significant local enhancement in heat transfer along the stagnation line for a single row of staggered effusion holes. However, the effect of arrangement is negligible for two rows of effusion holes. Among the configurations tested the case of one edge open exit configuration with a single row of staggered effusion holes (Case-C1s) shows higher heat transfer among others. © 2019, Taylor and Francis Ltd. All rights reserved.

Engineering Applications of Computational Fluid Mechanics

Computational investigations of flow and heat transfer on an effused concave surface with a single row of impinging jets for different exit configurations

Annals of the New York Academy of Sciences

Numerical Investigation of Combined Impingement and Convection Heat Transfer

Jet-Impingement Heat Transfer in Gas Turbine Systems

Journal of Fluids Engineering

Computational Fluid Dynamics Modeling of Impinging Gas-Jet Systems: II. Application to an Industrial Cooling System Device

Journal of Aircraft

Numerical Heat Transfer Correlation for Array of Hot-Air Jets Impinging on 3-Dimensional Concave Surface

AIChE Journal

Impinging jet cooling on concave surfaces

Computational investigation of flow and heat transfer for a row of circular jets impinging on a concave surface