The Effects of Slot Film Cooling on Deposition on a Nozzle Guide Vane

2014 ◽  
Author(s):  
Robin Prenter ◽  
Steven M. Whitaker ◽  
Ali Ameri ◽  
Jeffrey P. Bons
Keyword(s):  
Surface Temperature ◽  
Mass Flow ◽  
Flow Rate ◽  
Film Cooling ◽  
Guide Vane ◽  
Capture Efficiency ◽  
Coolant Flow Rate ◽  
Nozzle Guide Vane ◽  
Nozzle Guide ◽  
Slot Film Cooling

The effects of slot film cooling on deposition in a high pressure nozzle guide vane passage were investigated experimentally and computationally. Experiments were conducted in Ohio State’s Turbine Reaction Flow Rig, using a four-vane cascade, operating at temperatures up to 1353 K. Film cooling was achieved on one of the vanes using a span-wise slot, located at approximately 30% chord on the pressure surface. The coolant’s effect on vane surface temperature was characterized by taking infrared images at various cooling levels. Deposition was produced by injecting sub-bituminous ash particles with a median diameter of 6.48 μm upstream of the vane passage. Several deposition tests were conducted with varying coolant levels. Results exhibit a strong relationship between the coolant flow rate and the amount of ash that deposits on the cooled vane. Capture efficiency was reduced by 70% at the highest coolant flow rate (1.27% of the mass flow rate in the passage). Capture efficiency reduction was compared to that achieved using discrete hole film cooling in other studies. The slot scheme showed similar or larger reductions in capture efficiency at lower coolant mass flow rates. Deposit distribution patterns are affected by regions of cooler temperature, both downstream of the slot where film effects dominate, and slightly upstream of the slot which is cooled by conduction. A computational simulation was conducted to model both the flow and deposition. The solid vane was also discretized to allow for conjugate heat transfer calculations, which produced results that were qualitatively similar to IR measurements, but over predicted the effectiveness of the coolant. An Eulerian-Lagrangian particle tracking model was utilized to track the ash particles through the flow. A sticking model was implemented to determine whether particles stick upon impacting the vane surface, from which deposition rates and distributions are obtained. The computational model under predicted the baseline capture efficiency and the capture efficiency reduction factors for each cooling level, suggesting that the model is not sufficiently sensitive to the temperature changes between tests. Inclusion of surface temperature and local shear dependencies was suggested as an improvement to the sticking model.

Aerodynamic Measurements and Analysis in a First Stage Nozzle Guide Vane Passage With Combustor Liner Cooling, Slot Film Cooling and Endwall Contouring

2018 ◽  
Author(s):  
Mahmood H. Alqefl ◽  
Yong W. Kim ◽  
Hee-Koo Moon ◽  
Luzeng Zhang ◽  
Terrence W. Simon
Keyword(s):  
Secondary Flow ◽  
Flow Rate ◽  
Film Cooling ◽  
Guide Vane ◽  
Secondary Flows ◽  
Cooling Flows ◽  
Nozzle Guide Vane ◽  
Nozzle Guide ◽  
Slot Film Cooling ◽  
Combustor Liner

Endwalls impose a challenge to cool because of the complex system of secondary flows and separation lines disrupting surface film coolant coverage. The interaction of film cooling flows with secondary flow structures is coupled. The momentum exchange of the film coolant with the mainstream affect the formation the secondary flows, which in turn affect the coolant coverage. Therefore, to develop better endwall cooling schemes, a good understanding of passage aerodynamics as affected by interactions with coolant flows is required. This study presents experimental and computational results for cascade representing the first stage nozzle guide vane of a high-pressure gas turbine. The cascade is subsonic, linear, and stationary with an axisymmetrically-contoured endwall. Two cooling flows are simulated; upstream combustor liner coolant-in the form of an aero-thermal profile simulated in the approach flow and endwall slot film cooling, which is injected immediately upstream of the passage inlet. The experiment is run with engine representative combustor exit flow turbulence intensity and integral length scales, with high turbine passage exit Reynolds number of 1.61 × 106. Measurements are performed with various slot film cooling mass flow rate to mainstream flow rate ratios (MFR). Aerodynamic effects are documented with five-hole probe measurements at the exit plane. Varying the slot film cooling MFR results in minimal effects on total pressure loss for the range tested. Vorticity distributions show a very thin, yet intense, cross-pitch flow on the contoured endwall side. Coolant distribution fields that were previously presented for the same cascade are discussed in context of the aerodynamic measurements. A coolant vorticity parameter presenting the advective mixing of the coolant due to secondary flow vorticity is introduced. This parameter gives developers a new prospective on aerodynamic-thermal performance associated with cooled turbine endwall. The numerical study is conducted for the same test section geometry and is run under the same conditions. The applicability of using RANS turbulence closure models for simulating this type of flow is discussed. The effects of including the combustor coolant in the approach flow is also briefly discussed in context of the numerical results.

Effects of Endwall Film Coolant Flow Rate on Secondary Flows and Coolant Mixing in a First Stage Nozzle Guide Vane

2021 ◽  
Author(s):  
Mahmood Alqefl ◽  
Kedar Nawathe ◽  
Pingting Chen ◽  
Rui Zhu ◽  
Yong Kim ◽  
...  
Keyword(s):  
Flow Rate ◽  
Guide Vane ◽  
Secondary Flows ◽  
Coolant Flow ◽  
Coolant Flow Rate ◽  
Nozzle Guide Vane ◽  
Nozzle Guide

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.

The Effect of Film Cooling on Nozzle Guide Vane Deposition

2013 ◽  
Author(s):  
C. Bonilla ◽  
C. Clum ◽  
M. Lawrence ◽  
B. Casaday ◽  
J. P. Bons
Keyword(s):  
Surface Temperature ◽  
Film Cooling ◽  
Guide Vane ◽  
Particle Temperature ◽  
Test Facility ◽  
Minor Effect ◽  
Engine Operation ◽  
Infrared Measurements ◽  
Nozzle Guide Vane ◽  
Nozzle Guide

An accelerated deposition test facility was used to study the relationship between film cooling, surface temperature, and particle temperature on deposit formation. Tests were run at gas turbine representative inlet Mach numbers (0.1) and temperatures (1090°C). Deposits were created from lignite coal fly ash with mass median diameters of 1.3 and 8.8μm. Two CFM56-5B nozzle guide vane doublets, comprising three full passages and two half passages of flow, were utilized as the test articles. Tests were run with different levels of film cooling back flow margin and coolant temperature. Particle temperature upon impact with the vane surface was shown to be the leading factor in deposition. Since the particle must traverse the boundary layer of the cooled vane before impact, deposition is directly affected by the film and metal surface temperature as well. Film coolant jet strength showed only minor effect on deposit patterns on the leading edge. However, larger Stokes number (resulting in higher particle impact temperature) corresponded with increased deposit coverage area on the showerhead region. Additionally, infrared measurements showed a strong correlation between regions of greater deposits and elevated surface temperature on the pressure surface. Thickness distribution measurements also highlighted the effect of film cooling by showing reduced deposition immediately downstream of cooling holes. Implications for engine operation in particulate-laden environments are discussed.

scholarly journals The Influence of Film-Cooling on the Aerodynamic Performance of a Turbine Nozzle Guide Vane

1997 ◽  
Author(s):  
C. Osnaghi ◽  
A. Perdichizzi ◽  
M. Savini ◽  
P. Harasgama ◽  
E. Lutum
Keyword(s):  
Carbon Dioxide ◽  
Mass Flow ◽  
Film Cooling ◽  
Momentum Flux ◽  
Guide Vane ◽  
Flux Ratio ◽  
Aerodynamic Performance ◽  
Trailing Edge ◽  
Nozzle Guide Vane ◽  
Nozzle Guide

The paper presents the results of an investigation on the aerodynamic performance of a full coverage film-cooled nozzle guide vane. The blading is a typical high pressure turbine vane of advanced design, working in the high subsonic regime. Tests have been carried out for a wide range of conditions, including variations in Mach number, coolant to mainstream mass flow rate ratio and location of the coolant injection. Both air and carbon dioxide at ambient conditions have been utilized, as coolant flow. Measurements have been performed in a plane located at 0.5 axial chord downstream of the trailing edge by means of a miniaturized five-hole pressure probe. Performances, in terms of losses, flow angles and profile pressure distributions, for different cooling mass flow rates are presented and compared to the results of the solid blade tests (i.e. with no cooling holes). The results showed a significant increase of the losses with blowing. Test with air and carbon dioxide provided almost equal losses if carried out at the same global momentum flux ratio; however the density ratio was found to influence slightly the share of the coolant fluid among the injection rows and the local momentum flux ratio as well. In order to define the individual contributions of groups of cooling rows on the performance of the blade, three different modes of injection have been tested, namely full, trailing edge and shower head injection. The main trend observed is that trailing edge injection produces the least amount of additional losses at high blowing rates. Full-coverage film-cooling injection did not lead to marked variations in the blade pressure distribution and/or outlet flow angle.

The Effect of Particle Size and Film Cooling on Nozzle Guide Vane Deposition

2012 ◽  
Author(s):  
C. Bonilla ◽  
J. Webb ◽  
C. Clum ◽  
B. Casaday ◽  
E. Brewer ◽  
...  
Keyword(s):  
Particle Size ◽  
Film Cooling ◽  
Guide Vane ◽  
Stokes Number ◽  
Capture Efficiency ◽  
Test Facility ◽  
Deposit Thickness ◽  
Nozzle Guide Vane ◽  
Effect Of Particle Size ◽  
Nozzle Guide

An accelerated deposition test facility is used to study the effect of particle size and film cooling on deposit roughness, spatial distribution and thickness. Tests were run at gas turbine representative inlet Mach numbers (0.08) and temperatures (1080°C). Deposits were created from a sub-bituminous coal fly ash with mass median diameters from 4 to 16 microns (Stokes numbers ranging from 0.1 to 1.9. Two CFM56-5B nozzle guide vane doublets comprising three full passages and two half passages of flow were utilized as the test articles. Tests were run with three levels of film cooling. The addition of film cooling to the vanes was shown to decrease deposit capture efficiency by as much as a factor of 3 and shift the primary location of deposit buildup to the leading edge coincident with an increased region of positive cooling backflow margin. Video taken during tests noted that film cooling holes with negative backflow margin were primary areas of deposit formation regardless of film cooling percentage. Stokes number was shown to have a marked effect on vane capture efficiency, with the largest Stokes number ash (St = 1.9) approximately 3 times as likely to stick to the vane as the smallest Stokes number ash (St = 0.1). Post test observations on deposit thickness were made using a coordinate measurement machine. Deposit thickness was noted to be reduced with decreasing Stokes number and increased film cooling percentage. Deposit surface roughness falls with particle size but is only weakly dependent on cooling level.

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.

Contoured Endwall Flow and Heat Transfer Experiments With Combustor Coolant and Gap Leakage Flows for a Turbine Nozzle Guide Vane

2016 ◽  
Author(s):  
Reema Saxena ◽  
Mahmood H. Alqefl ◽  
Zhao Liu ◽  
Hee-Koo Moon ◽  
Luzeng Zhang ◽  
...  
Keyword(s):  
High Pressure ◽  
Gas Turbine ◽  
Mass Flow ◽  
Film Cooling ◽  
Thermal Loading ◽  
Guide Vane ◽  
Nozzle Guide Vane ◽  
Adiabatic Effectiveness ◽  
Interfacial Gap ◽  
Nozzle Guide

Flow in a high pressure gas turbine passage is complex, involving systems of secondary vortex flows and strong transverse pressure gradients. This complexity causes difficulty in providing film cooling coverage to the hub endwall region, which is subjected to high thermal loading due to combustor exit hot core gases. Therefore, an improved understanding of these flow features and their effects on endwall film cooling is needed to assist designers in developing efficient cooling schemes. The experimental study presented in this paper is performed on a linear, stationary, two-passage cascade representing the first stage nozzle guide vane of a high-pressure gas turbine. The sources of film cooling flows are the upstream combustor liner coolant and the leakage flow from the combustor-nozzle guide vane interfacial gap. Measurements are performed on an axisymmetrically-contoured endwall passage under conditions of various leakage mass flow rates to mainstream flow ratios (MFR= 0.5%, 1.0%, 1.5%). Flow migration and mixing are documented by measuring passage thermal fields and adiabatic effectiveness values over the endwall. It is found that, compared to our previous studies with a rotor inlet leakage slot geometry, the thin slot geometry of the nozzle leakage path gives a more uniform coolant spread over the endwall with significant coverage reaching the downstream and pressure-side regions of the passage. Interestingly, the coverage is seen to be only weakly dependent on the leakage mass low ratio and even reduce slightly with an increase in mass flow ratio above 1%, as indicated by lowered endwall adiabatic effectiveness values.

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.

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

2020 ◽  
Vol 37 (3) ◽  
pp. 221-240
Author(s):  
Pol Reddy Kukutla ◽  
B.V.S.S.S Prasad
Keyword(s):  
Mass Flow ◽  
Flow Rate ◽  
Guide Vane ◽  
Main Stream ◽  
Flow Rates ◽  
Hot Gas ◽  
Nozzle Guide Vane ◽  
Mass Flow Rates ◽  
Nozzle Guide ◽  
Gas Turbine Nozzle

AbstractThe 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.

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