HE.Eaton,GD. Linsey/ Journal of the European Ceran ocher22(2002)274-2747 Jsi(oh, ov. (PH, 0)/(Ptotal) (3) Fig 3 shows a plot of predicted (lines)and measured recession(points) at the mid-span position along the trailing edge of Allison silicon nitride first turbine vanes where J is the flux, v is the gas velocity and P is either versus time in an Allison M50l-K industrial gas tur the total system pressure or partial pressure of steam bine.7,The predicted recession values are based on the o, Experimental work by robinson and Smialek in a high work from Refs.5 and 9. This is another example of the oressure combustion test facility measured SiC recession effect of steam exposure based on actual engine exp versus test conditions and confirmed Eq. (3)for lean ence. The fact that it covers silicon nitride illustrates the combustion conditions. Fig. I summarizes the results for generic problem probably facing all silica formers in a lean burn conditions over the temperature range of high temperature, high steam combustion environment. approximately 1200-1450C. Table I provides predic- Additional supporting documentation of the effects of tions based on the experimental data for long term reces- steam exposure can be found in Refs. 10-16. sion of SiC in a combustion environment. The predicted recession at 1200 oC of 270 microns in 1000 h in a com bustion environment for SiC is too significant to ignore 2. Environmental barrier coatings (EBCs) for a material with expected useful life 30,000 h in a pro- posed application such as a industrial gas turbine. Work to understand the mechanisms of accelerated Confirmation of this behavior in actual engine eny oxidation of sic and to document the behavior in onments has been observed in a solar Turbines Inc experimental testing and actual engine environments led Centaur 50S industrial gas turbine and in an Allison M501-K industrial gas turbine. 7 The Solar Turbines, Solar Turbines, Inc. engine testing showed more than 90% Inc engine was run with SiC CMC combustion liners at oxidation of sic Cmc combustor liner wall thickness nominally 1200C for 5018 h Recession values of up to 5018hrs test (@ nominally 1200C 2200 microns were measured. This recession rate is roughly 0.44 H per hour to result in a 1000 h calculated recession of 440 H which is similar to the predicted loss of 270 H in 1000 h at 1200C from Table 1. Fig. 2 is a view of the liner in cross section at two different locations SiC Specic Weight Loss Rate NASA HPBR-Lean Bum [), T(K, P(atm), ms] SiC CMC combustor liner wall cross sections showing (a )no oxidation. k=206(e.w-50 00 um loss/5018 hrs =-0.44 um/hr recession rate or 440 um per 1000 hrs 866264666.8 Fig. 2. Cross sectional view of Solar Turbines. Inc SiC CMC Centaur 50S combustion liner after 5018 h operation(see Ref 6). Fig 1. Experimental measurements of Sic in a high pressure combustion environment (see Ref. 5) Alison M501-K 1st stage ceramic(AS-800)van recession observed vs time and predicted Table I Predicted recession of Sic under lean burn combustion conditions(see Predicted lean burn recession (um) g§ 1000h,10atm,90m/s 9?c 80010001200 time(hrs) 1500 1230 Fig. 3. Predicted and measured Ist turbine vane loss vs time in an Allison M50l-K industrial gas turbine(Refs. 7 and 8)JSiðOHÞ4 / v1=2  PH2O
2 =ð Þ Ptotal 1=2 ð3Þ where J is the flux, v is the gas velocity and P is either the total system pressure or partial pressure of steam. Experimental work by Robinson and Smialek5 in a high pressure combustion test facility measured SiC recession versus test conditions and confirmed Eq. (3) for lean combustion conditions. Fig. 1 summarizes the results for lean burn conditions over the temperature range of approximately 1200–1450
C. Table 1 provides predic￾tions based on the experimental data for long term reces￾sion of SiC in a combustion environment. The predicted recession at 1200
C of 270 microns in 1000 h in a com￾bustion environment for SiC is too significant to ignore for a material with expected useful life 30,000 h in a pro￾posed application such as a industrial gas turbine. Confirmation of this behavior in actual engine envir￾onments has been observed in a Solar Turbines, Inc. Centaur 50S industrial gas turbine6 and in an Allison M501-K industrial gas turbine.7 The Solar Turbines, Inc. engine was run with SiC CMC combustion liners at nominally 1200
C for 5018 h. Recession values of up to 2200 microns were measured. This recession rate is roughly 0.44 m per hour to result in a 1000 h calculated recession of 440 m which is similar to the predicted loss of 270 m in 1000 h at 1200
C from Table 1. Fig. 2 is a view of the liner in cross section at two different locations. Fig. 3 shows a plot of predicted (lines) and measured recession (points) at the mid-span position along the trailing edge of Allison silicon nitride first turbine vanes versus time in an Allison M501-K industrial gas tur￾bine.7,8 The predicted recession values are based on the work from Refs. 5 and 9. This is another example of the effect of steam exposure based on actual engine experi￾ence. The fact that it covers silicon nitride illustrates the generic problem probably facing all silica formers in a high temperature, high steam combustion environment. Additional supporting documentation of the effects of steam exposure can be found in Refs. 10–16. 2. Environmental barrier coatings (EBC’s) Work to understand the mechanisms of accelerated oxidation of SiC and to document the behavior in experimental testing and actual engine environments led Fig. 1. Experimental recession measurements of SiC in a high pressure combustion environment (see Ref. 5). Table 1 Predicted recession of SiC under lean burn combustion conditions (see Ref. 5) Predicted lean burn recession (mm) T (
C) 1000 h, 10 atm, 90 m/s 1000 70 1100 140 1200 270 1300 480 1400 790 1500 1230 Fig. 2. Cross sectional view of Solar Turbines, Inc SiC CMC Centaur 50S combustion liner after 5018 h operation (see Ref. 6). Fig. 3. Predicted and measured 1st turbine vane loss vs time in an Allison M501-K industrial gas turbine (Refs. 7 and 8). 2742 H.E. Eaton, G.D. Linsey/ Journal of the European Ceramic Society 22 (2002) 2741–2747