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Licensed Unlicensed Requires Authentication Published by De Gruyter July 26, 2017

Numerical Study on the Secondary Air Performance of the Film Holes for the Combined Impingement and Film Cooled First Stage of High Pressure Gas Turbine Nozzle Guide Vane

  • Pol Reddy Kukutla and B.V.S.S.S Prasad EMAIL logo

Abstract

The present numerical investigation of Leading Edge (LE) Nozzle Guide Vane (NGV) is considered with five rows of impingement holes combined with five rows of film cooled for the secondary coolant flow path analysis. The coolant mass flow rate variations in all the LE rows of the film holes externally subjected to the hot main stream were obtained by making a three-dimensional computational analysis of NGV with a staggered array of film cooled rows. The experiments were carried out for the same NGV using Particle Image Velocimetry technique to determine the effused coolant jet exit velocity at the stagnation row of film holes as mentioned in reference [Kukutla PR, Prasad BVSSS. Secondary flow visualization on stagnation row of a combined impingement and film cooled high pressure gas turbine nozzle guide vane using PIV technique, J Visualization, 2017; DOI: 10.1007/s12650-017-0434-6]. In this paper, results are presented for three different mass flow rates ranges from 0.0037 kg/s to 0.0075 kg/s supplied at the Front Impingement Tube (FIT) plenum. And the mainstream velocity 6 m/s was maintained for all the three coolant mass flow rates. The secondary coolant flow distribution was performed from SH1 to SH5 row of film holes. Each row of a showerhead film hole exit coolant mass flow rate varied in proportion to the amount of coolant mass rates supplied at the FIT cooling channel. The corresponding minimum and maximum values and their film hole locations were altered. The same behaviour was continued for the coolant pressure drop and temperature rise from SH1 to SH5 row of film holes. Owing to the interaction between hot main stream and the coolant that effuses out of the film holes, occasional presence of hot gas ingestion was noticed for certain flow rates. This caused nonlinear distribution in mass flow, pressure drop and temperature rise. The minimum flow rate results estimate oxidation of NGV material near the film cooled hole. And the effect of hot gas ingestion on the ejected film cooled jet which would recommends effective oxidation resistant material which in turn leads to better durability of the NGV surface.

Nomenclature

m˙

- Mass flow rate (kg/s)

P

-Pressure (Pa)

∆P

-Pressure Drop (Pa)

T

-Temperature (K)

∆T

- Coolant Temperature Raise (K)

S

- Streamwise distance from the stagnation point to the specified row position

C

-True chord length of the vane

Subscript
i

inlet

o

outlet

t

Total

s

Static

j

Film cooled jet location

c

Summation of film cooled row total values

Abbreviations
CFD

-Computational Fluid Dynamics

NGV

-Nozzle Guide Vane

FIT

-Front impingement tube

PS

Pressure Surface

SS

Suction Surface

LE

Leading Edge

SH

Showerhead

IL Impingement rows facing the leading edge region.

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Received: 2017-06-28
Accepted: 2017-07-12
Published Online: 2017-07-26
Published in Print: 2020-08-27

© 2020 Walter de Gruyter GmbH, Berlin/Boston

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