Download or read book SiC and Si3N4 Recession Due to SiO u2082 Scale Volatility Under Combustor Conditions written by and published by . This book was released on 1999 with total page 7 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book SiC and Si3N4 Recession Due to SiO2 Scale Volatility Under Combustor Conditions written by James L. Smialek and published by . This book was released on 1999 with total page 14 pages. Available in PDF, EPUB and Kindle. Book excerpt: Silicon carbide (SiC) and Si3N4 materials were tested in various turbine engine combustion environments chosen to represent either conventional fuel-lean or fuel-rich mixtures proposed for high-speed aircraft. Representative chemical vapor-deposited (CVD), sintered, and composite materials were evaluated by furnace and high-pressure burner rig exposures. Although protective SiO2 scales formed in all cases, the evidence presented supports a model based on paralinear growth kinetics (i.e., parabolic growth moderated simultaneously by linear volatilization). The volatility rate is dependent on temperature, moisture content, system pressure, and gas velocity. The burner tests were thus used to map SiO2 volatility (and SiC recession) over a range of temperatures, pressures, and velocities. The functional dependency of material recession (volatility) that emerged followed the form A[exp(-Q / RT)](P[factor x]v[factor y]). These empirical relations were compared with rates predicted from the thermodynamics of volatile SiO and SiO[sub x]H[sub y] reaction products and a kinetic model of diffusion through a moving boundary layer. For typical combustion conditions, recession of 0.2 to 2[micro]m/hr is predicted at 1200 to 1400°C, far in excess of acceptable long-term limits.
Download or read book Sic and Si3n4 Recession Due to Sio2 Scale Volatility Under Combustor Conditions written by National Aeronautics and Space Adm Nasa and published by Independently Published. This book was released on 2018-09-25 with total page 26 pages. Available in PDF, EPUB and Kindle. Book excerpt: Silicon carbide (SiC) and Si3N4 materials were tested in various turbine engine combustion environments chosen to represent either conventional fuel-lean or fuel-rich mixtures proposed for high-speed aircraft. Representative chemical vapor-deposited (CVD), sintered, and composite materials were evaluated by furnace and high-pressure burner rig exposures. Although protective SiO2 scales formed in all cases, the evidence presented supports a model based on paralinear growth kinetics (i.e., parabolic growth moderated simultaneously by linear volatilization). The volatility rate is dependent on temperature, moisture content, system pressure, and gas velocity. The burner tests were thus used to map SiO2 volatility (and SiC recession) over a range of temperatures, pressures, and velocities. The functional dependency of material recession (volatility) that emerged followed the form A[exp(-Q / RT)](P(sup x)v(sup y). These empirical relations were compared with rates predicted from the thermodynamics of volatile SiO and SiOxHy reaction products and a kinetic model of diffusion through a moving boundary layer. For typical combustion conditions, recession of 0.2 to 2 micrometers/hr is predicted at 1200 to 1400 C, far in excess of acceptable long-term limits. Smialek, James L. and Robinson, Raymond C. and Opila, Elizabeth J. and Fox, Dennis S. and Jacobson, Nathan S. Glenn Research Center NASA/TP-1999-208696, E-11447, NAS 1.60:208696
Download or read book SiC Recession Due to SiO2 Scale Volatility Under Combustor Conditions written by Raymond Craig Robinson and published by . This book was released on 1997 with total page 104 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Sic Recession Due to Sio2 Scale Volatility Under Combustion Conditions written by Elizabeth J. Opila and published by BiblioGov. This book was released on 2013-08 with total page 52 pages. Available in PDF, EPUB and Kindle. Book excerpt: In combustion environments, volatilization of SiO2 to Si-O-H(g) species is a critical issue. Available thermochemical data for Si-O-H(g) species were used to calculate boundary layer controlled fluxes from SiO2. Calculated fluxes were compared to volatilization rates Of SiO2 scales grown on SiC which were measured in Part 1 of this paper. Calculated volatilization rates were also compared to those measured in synthetic combustion gas furnace tests. Probable vapor species were identified in both fuel-lean and fuel-rich combustion environments based on the observed pressure, temperature and velocity dependencies as well as the magnitude of the volatility rate. Water vapor is responsible for the degradation of SiO2 in the fuel-lean environment. Silica volatility in fuel-lean combustion environments is attributed primarily to the formation of Si(OH)4(g) with a small contribution of SiO(OH)2(g).
