Experimental validation of a hot gas turbine particle deposition facility

EXPERIMENTAL VALIDATION OF A HOT GAS TURBINE PARTICLE DEPOSITION FACILITY A Thesis Presented in Partial Fulfillment of the Requirements for the Degree of Master of Science in the Graduate School of The Ohio State University By: Christopher Stephen Smith, B.S Graduate Program in Aeronautical and Astronautical Engineering The Ohio State University 2010 Master’s Examination Committee: Dr Jeffrey P Bons, Advisor Dr James Gregory Dr Ali Ameri ABSTRACT A new turbine research facility at The Ohio State University Aeronautical and Astronautical Research Lab has been constructed The purpose of this facility is to recreate deposits on the surface of actual aero-engine Nozzle Guide Vane (NGV) hardware in an environment similar to what the hardware was designed for This new facility is called the Turbine Reacting Flow Rig (TuRFR) The TuRFR provides air at temperatures up to 1200 °C and at inlet Mach numbers comparable to those found in an actual turbine (~0.1) Several validation studies have been undertaken which prove the capabilities of the TuRFR These studies show that the temperature entering the NGV cascade is uniform, and they demonstrate the capability to provide film cooling air to the NGV cascade at flow rates and density ratios comparable to the NGV design Deposition patterns have also been created on the surface of actual NGV hardware Deposition was created at different flow temperatures, and it was found that deposition levels decrease with decreasing gas temperature Also, film cooling levels were varied from 0% film cooling to 4% film cooling It was found that with increased rates of film cooling deposition decreased With the TuRFR capabilities demonstrated, research on the effects of deposition on the aerodynamic performance of the NGV hardware was conducted ii Integrated non-dimensional total pressure loss values were calculated in an exit Re c range of 0.2x106 to 1.7x106 for a deposit roughened NGV cascade and a smooth cascade The data suggests that deposition causes increased losses across the NGV cascade and possibly earlier transition The data also suggests a possible region of separated flow in the NGV cascade which disappears at higher exit Reynolds numbers These results are similar to those found in the literature iii ACKNOWLEDGMENTS I would like to take this opportunity to thank my advisor Dr Jeffrey Bons for his patience, guidance, and continual support during this endeavor It has truly been privilege learning from him I would also like to acknowledge the help of Brett Barker, Carey Clum, and Josh Webb Without their knowledge and willingness to solve problems the TuRFR would not be operational today I would also like to thank the staff of AARL, especially Ken Copely, Ken Fout, Jeff Barton and Cathy Mitchell for their undying patience and help I would also like to express my appreciation to Dr James Gregory and Dr Ali Ameri for serving on my graduate committee Finally I would like to thank my friends and family for their support and encouragement along the way iv VITA July 15, 1984 ……………………………… Born in Texas City, Texas August 2007………………………………….B.S Mechanical Engineering, The University of Texas at Austin 2007 – Present ………………………………Graduate Research Associate, Department of Aerospace Engineering The Ohio State University PUBLICATIONS Smith, C., Barker, B., Clum, C., Bons, J., “Deposition in a Turbine Cascade with Combusting Flow,” to be presented at the 2010 Turbo Expo in Glasgow, Scotland June 2010, paper # GT2010-22855 FIELDS OF STUDY Major Fields of Study: Aeronautical and Astronautical Engineering v TABLE OF CONTENTS ABSTRACT ii ACKNOWLEDGMENTS iv VITA v FIELDS OF STUDY .v TABLE OF CONTENTS vi LIST OF FIGURES ix LIST OF TABLES xii LIST OF EQUATIONS xiii NOMENCLATURE xiv CHAPTER INTRODUCTION 1.1 Background .1 1.2 Literature Review 1.2.1 Other Deposition Research CHAPTER 10 TuRFR DESCRIPTION AND VAILDATION STUDIES 10 vi 2.1 Primary Flow Path Description 10 2.2 Particulate Feed Sub-System 17 2.3 TuRFR Validation Studies 19 2.3.1 NGV Inlet Temperature Survey 21 2.3.2 Film Cooling Validation Survey 22 2.3.3 Exit Total Pressure Surveys 24 CHAPTER 30 ASH PARTICULATE 30 3.1 Description of Particulate 30 CHAPTER 34 DEPOSITION TESTING RESULTS 34 4.1 Deposition Testing 34 4.1.1 Temperature Variation 37 4.1.2 Film Cooling Variation 38 4.2 Surface Roughness Measurements 39 4.3 Deposit Structure and Chemical Composition 42 CHAPTER 45 AERODYNAMIC PERFORMANCE ASSESSMENT 45 5.1 Aerodynamic Performance Assessment Background 45 vii 5.1.1 Total Pressure and Exit Temperature Measurement Setup 46 5.1.2 Inlet Total Pressure Measurement 48 5.2 Aerodynamic Performance Results 52 5.2.1 Rough Aerodynamic Performance 53 5.2.2 Smooth Aerodynamic Performance 59 5.3 Discussion of Results 64 CHAPTER 70 6.1 Conclusions 70 6.2 Future Work 71 REFERENCES 73 APPENDIX A: 76 UNCERTAINTY ANALYSIS OF THE γ CALCULATION 76 viii LIST OF FIGURES Figure - Leading edge of turbine nozzle guide vanes exposed to high volcanic ash concentrations Note the effects of increased surface heat transfer caused by clogged film cooling holes [2] Figure - Turbine Accelerated Deposition Facility (TADF) at Brigham Young University [11] Figure - TuRFR schematic showing main flow path 12 Figure - Flameholder inside combustion section of TuRFR 13 Figure - 3D cutaway view of upper section of TuRFR showing measurement locations 15 Figure - Top view of NGV cascade and film cooling reservoir showing film cooling temperature measurement locations 16 Figure - 3D CAD schematic of particulate feeder Pressure equalization tube is not shown in the diagram 18 Figure - NGV cascade inlet temperature survey 22 Figure - Dimensionless temperature at vane exit with 4% film heating, red box shows approximate location of measurement plane 24 ix Abuaf et al [22] have also conducted studies on the effects of roughness on the aerodynamic and heat transfer performance of turbine airfoils They used a linear NGV cascade to conduct transient heat transfer and aerodynamic efficiency measurements at constant Mach number They conducted tests using airfoils of three different roughness levels: Ra/cx = 4.8x10-5, 2.14x10-5, and 1.68x10-5 These values are much smaller than the roughness levels created by the TuRFR Their local heat transfer coefficient data shows that as roughness levels are increased the laminar to turbulent transition point moves slightly closer to the leading edge of the turbine airfoil In terms of the local Re: transition happens at smaller values of local Re for the rough surfaces compared to the smooth surfaces This compares well with Figure 26 and Figure 27; as the roughness level is increased the Rec exit required for transition is smaller The trends in aerodynamic efficiency at varying levels of surface roughness also compare well with the results presented in earlier sections As roughness levels increase the aerodynamic efficiency decreases, indicating more losses across the NGV The smaller values of Ra/c used by Abuaf et al not seem to have an influence on the trends of moving the transition point or increased losses with increasing roughness Hummel et al [21] uses a linear NGV cascade to make measurements of total pressure loss at varying exit Rec and constant Mach number They used spanwise grooves to generate Ra/c values in the range of 7.6x10 -6 to 7.9x10-5 These roughness values are smaller than the ones created using the TuRFR Hummel et al found that as roughness increases the losses increase, but most of the loss increases appear on the suction side of the wake They also show that there is a slight increase in losses with 67 increasing exit Rec Data presented earlier shows similar trends in that increasing roughness results in more loss, but the data does not show which side of the airfoil is causing more of the loss Even though most of the roughness values tested by Hummel et al were smaller than those created by the TuRFR, similar trends were observed Stripf et al [23] has conducted heat transfer experiments in a linear NGV cascade They created rough surfaces in the Ra/c range of 1.06x10 -4 to 8.52x10-4 by using an evenly spaced array of truncated cones Most of these Ra/c values are higher than those formed by the TuRFR, but the lower end of the Ra/c range is quite similar to those created by the TuRFR Stripf et al show that as roughness levels increase the laminar to turbulent transition occurs closer to the leading edge of the airfoil, with more dramatic effects occurring on the suction side This is similar to the findings Hummel et al [21] At the roughness levels comparable to those created by the TuRFR boundary layer transition seems to have occurred closer to the leading edge, corroborating further the results presented in Figure 26 and Figure 27 Integrated non-dimensional total pressure loss has been shown to increase with increasing surface roughness A review of the literature has shown that this result is in agreement with studies conducted in a variety of facilities using a variety of surface roughness simulation techniques and surface roughness levels Figure 26 and Figure 27 suggest that as roughness levels are increased the laminar to turbulent transition point moves closer to the leading edge of the airfoil Other authors have also shown similar results, and have also shown that the suction surface of the airfoil is more susceptible to this effect 68 However, boundary layer separation must be conclusively ruled out before transition can be thought of as the only mechanism causing the observed trends in Figure 26 and Figure 27 69 CHAPTER CONCLUSIONS AND FUTURE WORK 6.1 Conclusions The TuRFR is a new hot gas accelerated particle deposition facility at the Aeronautical and Astronautical Research Lab, located at Don Scott Airport in Columbus Ohio This facility is capable of creating deposition patterns similar to, if not the same as, those found on actual in-service turbine hardware In order to this the TuRFR must supply an air flow at realistic Mach numbers and temperatures to actual turbine hardware Through a series of validation tests, the TuRFR has demonstrated the ability to supply a hot (~1000 °C) air flow at Mach numbers of about 0.1 This temperature and Mach number is representative of those found in power generation turbines The TuRFR has also demonstrated the ability to supply particulate to the hot flow in a steady and continuous manner using a particulate feeder The TuRFR has also demonstrated its ability to supply the hot air/particulate mixture to actual engine hardware The NGV cascade used for these studies comes from a CFM56-5B engine Deposition has been created on the surface of the NGV cascade a number of times, and has successfully been removed an equal number of times With these validation tests complete, the TuRFR is 70 ready to begin exploring areas, such as the effects of real deposition (as opposed to simulated deposition) on the aerodynamic performance of real turbine NGVs The aerodynamic performance of this cascade of NGV hardware was assessed by measuring a parameter known as the integrated non-dimensional total pressure loss This parameter is a measure of the total pressure losses incurred by the NGV across the wake of the NGV It was found that, when compared to a smooth case, roughness increases the losses across a nozzle guide vane It was also found that roughness can force laminar to turbulent transition to happen earlier along the vane surface An earlier transition can cause detrimental effects by increasing the thickness of the boundary layer at the trailing edge of the airfoil for a given Reynolds number and by increasing the local heat transfer coefficient These results have been compared to results found in current literature The trends summarized above agree well with those found in the literature 6.2 Future Work Future studies include effects of film cooling on the amount of deposition created, effects of temperature on the amount of deposition created, and the effects of particle loading on the amount of deposition created Including the effects of varying all of these parameters on the amount of deposition, the aerodynamic performance of the NGV cascade can be assessed after each flow parameter is varied to quantify the effects of different levels of deposition on the aerodynamic performance Also, the exit total pressure data used in this thesis was collected along a straight line in the NGV cascade exit plane The cascade is not a linear cascade, however Another possible future work would be to develop a data acquisition routine that takes into account the annular nature 71 of the cascade With this new routine in place a validation of the blade to blade variation being due to spanwise location variation can be conducted Finally, an attempt at isolation of the effects of roughness on the suction surfaces of the NGV cascade should be taken on so that a more direct comparison to the results found in the literature can be made Finally, the boundary layer over the surface of the NGV cascade must be characterized in order to determine if separation is occurring somewhere along the vane surface Knowledge of potential separation locations can confirm or deny the observations presented in this thesis 72 REFERENCES [1] Wenglarz, R.A., Fox, R.G Jr “Physical Aspects of Deposition From Coal-Water Fuels Under Gas Turbine Conditions”, J Engr Gas Turbine & Power Vol 120, Jan 1990, pp 9-14 [2] Kim, J., Dunn, M.G., and Baran, A.J et al, “Deposition of Volcanic Materials in the Hot Sections of Two Gas Turbine Engines,” J Engr Gas Turbines & Power Vol 115, Jul 1993, pp 641-651 [3] Wenglarz, R.A., “An Approach for Evaluation of Gas Turbine Deposition,” J Engr Gas Turbines & Power Vol 114, April 1992, pp 230-234 [4] Bogard, D.G., Schmidt, D.L., Tabbita, M., “Characterization and Laboratory Simulation of Turbine Airfoil Surface Roughness and Associated Heat Transfer,” J Turbomachinery Vol 120, April 1998, pp 337-342 [5] Sundaram, N., Thole, K., “Effects of Surface Deposition, Hole Blockage, and Thermal Barrier Coating Spallation on Vane Endwall Film Cooling,” J Turbomachinery Vol 129, July 2007, pp 599-607 [6] Schlichting, H Boundary-Layer Theory McGraw Hill Book Company, 1968, 6th edition pp 578-623 [7] Bammert, K., Sandstede, H., “Measurements of the Boundary Layer Development along a Turbine Blade with Rough Surfaces,” Journal of Engineering for Power Vol 102, Oct 1980, pp 978-983 [8] Zhang, Q., Lee, S W., Ligrani, P M., “Effects of Surface Roughness and Turbulence Intensity on the Aerodynamic Losses Produced by the Suction Surface of a Simulated Turbine Airfoil,” Journal of Fluids Engineering Vol 126, March 2004, pp 257-265 [9] Boyle, R.J., Senyitko, R.G., “Measurements and Predictions of Surface Roughness Effects on Turbine Vane Aerodynamics,” presented at ASME Turbo Expo 2003 June 16-19, Atlanta, Georgia Paper # GT-2003-38580 [10] Zhang, Q., Goodro, M., Ligrani, P M., Trindad, R., Sreekanth, S., “Influence of Surface Roughness on the Aerodynamic Losses of a Turbine Vane,” J Fluids Engineering Vol 128, May 2006, pp 568-578 73 [11] Jensen, J.W., Squire, S.W., Bons, J.P., Fletcher, T.H., “Simulated Land-Based Turbine Deposits Generated in an Accelerated Deposition Facility,” J Turbomachinery Vol 127, July 2005, pp 462-470 [12] Crosby, J.M., Lewis, S., Bons, J.P, Ai, W., Fletcher, T.H., “Effects of Particle Size, Gas Temperature, and Metal Temperature on high Pressure Turbine Deposition in Land Based Gas Turbines from Various Synfuels,” presented at ASME Turbo Expo 2007: Power for Land, Sea, and Air May 14-17, 2007, Montreal, Canada Paper #: GT2007-25731 [13] Ai, W., Fletcher, T.H., “Computational Analysis of Conjugate Heat Transfer and Particulate Deposition on a High Pressure Turbine Vane,” presented at ASME Turbo Expo 2009: Power for Land, Sea, and Air June, 2009, Florida, United States Paper #: GT2009-59573 [14] Lawson, S.A., Thole, K., “The Effects of Simulated Particle Deposition on Film Cooling,” presented at ASME Turbo Expo: Power for Land, Sea, and Air June 812, 2009, Orlando, Florida USA Paper #: GT2009-59109 [15] Vandsburger, U., Tafti, D, Ng, W., “Syngas Particulate Deposition and Erosion at the Leading Edge of a Turbine Blade with Film Cooling.” Presented at UTSR Workshop, Oct 27-29, 2009, Orlando, FL, USA [16] Cramer, K Bons, J Sammimy, M., “Design Construction and Preliminary Validation of the Turbine Reacting Flow Rig,” 2009, The Ohio State University, Master’s Thesis, Aeronautical and Astronautical Engineering [17] Probstein, R.F., Hicks, R.E., Synthetic Fuels McGraw Hill Book Company, 1982 [18] Wenglarz, R.A., Wright, I.G., “Alternative Fuels for Land-Based Turbines,” published in proceedings of the “Workshop on Materials and Practices to Improve Resistance to Fuel Derived Environmental Damage in Land-and Sea-Based Turbines,” October 22-24, 2002, Colorado School of Mines, Golden Colorado [19] Day, C.R.B., Oldfield, M.L.G., Lock, G.D., “Aerodynamic Performance of an Annular Cascade of Film Cooled Nozzle Guide Vanes Under Engine Representative Conditions,” Experiments in Fluids Vol 29, 2000, pp 117-129 [20] Bons, J.P., Taylor, R.P., McClain, S.T., Rivir, R.B., “The Many Faces of Turbine Surface Roughness,” J Turbomachinery Vol 123, No 4, Oct 2001, pp 739-748 [21] Hummel, F., Lötzerich, M., Cardamone, P., Fottner, L., “Surface Roughness Effects on Turbine Blade Aerodynamics,” J Turbomachinery Vol 127, July 2005, pp 453-461 74 [22] Abuaf, N., Bunker, R.S., Lee, C.P., “Effects of Surface Roughness on Heat Transfer and Aerodynamic Performance of Turbine Airfoils,” J Turbomachinery Vol 120, July 1998, pp 522-529 [23] Stripf, M., Schulz, A., Wittig, S., “Surface Roughness Effects on External Heat Transfer of a HP Turbine Vane,” J Turbomachinery Vol 127, Jan 2005, pp 200208 [24] Coleman, H.W., Steele, W G Experimentation and Uncertainty Analysis for Engineers 2nd Edition Wiley Intersciecnce, 1999 75 APPENDIX A: UNCERTAINTY ANALYSIS OF THE γ CALCULATION 76 This uncertainty analysis uses methods presented in Experimentation and Uncertainty Analysis for Engineers by H.W Coleman and W.G Steele [24] This analysis begins with the development of the uncertainty of the non-dimensional total pressure loss, and then proceeds to the uncertainty of the integrated non-dimensional total pressure loss The equation for non-dimensional total pressure loss is: Using continuity, the equation for N can be translated into measured variables: Where Ptot in is the total pressure at the inlet (this value is calculated from a curve fit of a Ptot passage vs curve, where Ptot passage is the total pressure in the center of the vane passage This curve was created at a different time than the Ptot meas measurements.), Ptot meas is the total pressure at the measurement location, Pamb is the ambient pressure, Texit is the exit temperature, Aexit is the exit area of the NGV cascade, is the mass flow passing through the cascade, and R is the ideal gas constant for air The ideal gas constant for air is assumed to have zero uncertainty The uncertainty of N is given by: 77 The partial derivatives are: The uncertainties of the measured variables are estimated as follows: UPtot in => This uncertainty is estimated using the polyfit() and polyval() functions built into MATLAB Polyfit() uses a 2nd order polynomial least squares regression on the data of the Ptot in vs curve to obtain the fit and the uncertainty of the fit Then polyval() uses the coefficients of the fit from polyfit() and the uncertainty estimate from polyfit() to calculate the value and the uncertainty of the inlet total pressure based on the The commands polyfit() and polyval(), however, not take into account the uncertainty of the actual used in the γ calculation is shown as Figure 19 in the text 78 The actual fit UPtot meas => This uncertainty is estimated from the pressure transducer calibration using a linear least squares regression of the psia vs mA calibration curve for the transducer MATLAB functions were not employed for this uncertainty analysis because the calibration curve is linear and not a higher order polynomial UPamb => This uncertainty was estimated as half of the measurement precision of the barometer UAexit => This uncertainty was estimated as half of the smallest scale of the ruler used to measure the exit area dimensions UTexit => This uncertainty was estimated using the manufacturer quoted uncertainties of the thermocouple Um => This uncertainty was estimated using the same procedure from Coleman and Steele as used for the N uncertainty calculations, but with a different data reduction equation and different instrument uncertainties The equation for γ is: Where L is the width of the wake trailing an NGV vane in the cascade, dx is the distance between measurement points, and N is the non-dimensional total pressure calculated at each of the measurement points This equation can be approximated by the summation: 79 Where b is the index of the N measurement where the wake begins, and a is the index of the N measurement where the wake ends The uncertainty of γ is given by: Where UN is the average uncertainty of the non-dimensional total pressure measurements, and Udx is the uncertainty of the position of the traverse at each measurement location On the traverse spec sheet the precision of the traverse is listed as 0.004 mm This precision was taken to be the uncertainty of the traverse position at each measurement location (ie: Udx = 0.004 mm) The partial derivatives are as follows: Some typical values of γ uncertainty are presented here in the table below Also, a typical UN is presented below They were taken from the gamma calculation for Re c exit = 1x106 UN Typical Uncertainty Values 0.0973 e-4 Uγ with average in partial 0.006 Typical Values of N and γ N = 5.5x10-3 ± 0.17% γ = 0.0926 ± 6.5% Table - Typical values of the N and γ uncertainties using the error propagation analysis There are a few things to note about the foregoing uncertainty analysis: 80 Examining the equations for the γ uncertainty it would seem that the uncertainty of γ would increase with increasing sample sizes This is the opposite of what is expected to happen, and leads one to believe that there is an error in the analysis The uncertainty of N is much smaller than that for γ The Uncertainty Percentage Contribution (UPC) for the variable N is on the order of 10-4 This indicates that the uncertainty in N does not propagate into the γ uncertainty and that most, if not all, errors in the value of γ come from the variability of the experiment As a result of the two notes mentioned above, the variance of the γ calculation was determined using ten independent exit total pressure surveys at Re c exit ≈ 0.5x106 conditions All of these values are tabulated below The uncertainty in all of the γ calculations was therefore taken to be the standard deviation of this set of ten measurements This value is presented as error bars, and as ± values, where appropriate on the figures inside this thesis Run No 10 γ error γ - Blade γ - Blade 0.0833 0.082 0.088 0.0881 0.0921 0.0814 0.0812 0.0827 0.0826 0.0876 0.0037 0.0723 0.0731 0.0741 0.0749 0.0769 0.0712 0.0714 0.0711 0.0722 0.0746 0.0019 Table - Values used in the γ variance determination 81 ... of the natural gas was supplied by Columbia Gas Natural Gas used in this particular study has specific gravity of 0.592, a heating value of 38.6 MJ/m3, and consists of 95% methane, 2.35% ethane,... temperature air from a separate source and are separated from the main gas path with removable plates These plates can be perforated to allow cooler air to mix with the primary gas path This capability... effects of particulate deposition on turbine hardware and film cooling effectiveness However, there has not been a facility that is capable of simulating deposition on actual turbine hardware in a