Surface Oxidation Mechanisms of Molybdenum Disilicide in High-Temperature Combustion Environments

1993 ◽  
Vol 322 ◽  
Author(s):  
Wen-Yi Lin ◽  
Robert F. Speyer
Keyword(s):  
Surface Layer ◽  
Molybdenum Disilicide ◽  
Surface Oxidation ◽  
Combustion Products ◽  
Passive Oxidation ◽  
Temperature Combustion ◽  
The Stability ◽  
High Temperature Combustion ◽  
Surface Layer Thickness ◽  
Good Agreement

AbstractThe stability of MoSi2 was studied at 1600°C in combustion products with an incoming gas to air ratio of 1:6.7 and compared to results in a 1:10 environment. Oxidation was investigated using periodic weight measurements and characterization using XRD, SEM, and EDS. Passive oxidation was observed; MoSi2 was oxidized by H2O and CO2 to form Mo5 Si3 and SiO2. The amorphous silica product formed a surface layer and reduced the oxidation rate as it coarsened. MoO3(g) did not form which was in agreement with the thermodynamic (SOLGASMIX-PV) prediction that it would only form in the presence of molecular oxygen. A good agreement was observed between the measured and calculated weight gains based on the surface layer thickness.

scholarly journals Features of thermodynamic and thermal processes in hydrogen combustion units and systems on their basis

2021 ◽  
Vol 2039 (1) ◽  
pp. 012032
Author(s):  
A I Schastlivtsev ◽  
V I Borzenko
Keyword(s):  
High Temperature ◽  
Combustion Products ◽  
Hydrogen Combustion ◽  
Thermal Processes ◽  
Steam Generators ◽  
Temperature Combustion ◽  
Main Components ◽  
High Temperature Combustion

Abstract The main types and designs of hydrogen combustion units (HCU), including hydrogen-oxygen steam generators, superheaters and air heaters of various power levels, are considered. The main problems arising in the development, creation and testing of such installations are determined, including the problems of cooling the most heat-stressed units, mixing of the main components of the fuel and oxidizer, mixing of high-temperature combustion products and ballasting components, problems associated with the completeness of hydrogen combustion and ensuring safety during operation.

In-Depth Absorption of Externally Incident Radiation in Nongray Media

1995 ◽  
Vol 117 (1) ◽  
pp. 146-151 ◽  
Author(s):  
S. S. Manohar ◽  
A. K. Kulkarni ◽  
S. T. Thynell
Keyword(s):  
Plastic Material ◽  
Combustion Products ◽  
Incident Radiation ◽  
Radiative Properties ◽  
Spectral Variation ◽  
Radiation Model ◽  
Temperature Combustion ◽  
Clear Plastic ◽  
Almost All ◽  
High Temperature Combustion

During flame spread along a surface, the thermal radiation emitted by high-temperature combustion products supports the advancement of the flame front. To model the response of the solid to the externally incident radiation, it is necessary to consider the spectral variation of radiative properties of the solid. For highly absorbent solids, such as wood or particle board, almost all of the externally incident radiation is absorbed at or very near the surface. However, for highly semitransparent materials, such as a plastic material whose surface is not clean, the externally incident radiation is absorbed both at the surface and within the material. In this work, the objective is to study both theoretically and experimentally the importance of in-depth radiation. A transient, one-dimensional model is formulated and solved numerically. The spectral radiative properties employed in the radiation model have been obtained from separate experiments on polymethylmethacrylate (PMMA), a clear plastic. The model demonstrates the importance of in-depth absorption. Model results exhibit the same trend as those revealed in experiments for the rise in surface temperature of the sample.

Technology for fi nishing combined processing of mineral-ceramic coatings

2020 ◽  
pp. 318-323
Author(s):  
E.V. Panichev ◽  
V.P. Smolentsev ◽  
V.V. Ivanov
Keyword(s):  
Surface Layer ◽  
Protective Coatings ◽  
Combustion Products ◽  
Ceramic Coatings ◽  
Fuel Combustion ◽  
Rocket Engines ◽  
Combustion Chambers ◽  
Temperature Combustion ◽  
Liquid Rocket ◽  
Processing Zone

Technological methods for manufacturing of cooling elements of modern rocket engines are considered, they are developed taking into account the possibility of reusable use. Significant increase in the thermal load on the walls of combustion chambers of liquid rocket engines required the creation of new ways to protect the surface layer of the hot zone from the effects of the flame in the fuel combustion zone. The possibilities for using of plasma application of metal-ceramic heat-protective coatings for these purposes, which have good erosion resistance and high thermal resistance in conditions of intense exposure to high-temperature combustion products, are revealed. The analysis of the effect of the quality of the coatings surface layer on the performance characteristics of the product is presented. The need for local finishing of the applied coatings is justified, including in the transition areas of the combustion chambers and the jet nozzle, which have limited tool access to the processing zone. The most effective method is the combined alignment of the microprofile with the imposition of electric field. But for its implementation, set of studies is needed to study the mechanism of allowance removing, and to adjust the technological modes. The task of minimizing allowances for finishing combined processing is solved, which allowed to align the thickness of the heat-protective coating along the length of the fuel combustion path, including the cleaning sections, to increase the number of trouble-free engine starts by 1.5...2.0 times and ensure reusable use of product.

scholarly journals Simultaneous High-Speed Formaldehyde PLIF and Schlieren Imaging of Multiple Injections From an ECN Spray D Injector

2020 ◽  
Author(s):  
Noud Maes ◽  
Hyung Sub Sim ◽  
Lukas Weiss ◽  
Lyle Pickett
Keyword(s):  
High Temperature ◽  
High Speed ◽  
Combustion Products ◽  
Schlieren Imaging ◽  
Multiple Injections ◽  
Soot Precursors ◽  
Planar Laser ◽  
Temperature Combustion ◽  
Polycyclic Aromatic ◽  
High Temperature Combustion

Abstract The interaction of multiple injections in a diesel engine facilitates a complex interplay between freshly introduced fuel, previous combustion products, and overall combustion. To improve understanding of the relevant processes, high-speed Planar Laser-Induced Fluorescence (PLIF) with 355-nm excitation of formaldehyde and Polycyclic Aromatic Hydrocarbon (PAH) soot precursors is applied to multiple injections of n-dodecane from Engine Combustion Network Spray D, characterized by a converging 189-μm nozzle. High-speed schlieren imaging is applied simultaneously with 50-kHz PLIF excitation to visualize the spray structures, jet penetration, and ignition processes. For the first injection, formaldehyde (as an indicator of low-temperature chemistry) is first found in the jet periphery, after which it quickly propagates through the center of the jet, towards the jet head prior to high-temperature ignition. At second-stage ignition, downstream formaldehyde is consumed rapidly and upstream formaldehyde develops into a quasi-steady structure for as long as the momentum flux from the injector continues. Since the first injection in this work is relatively short, differences to a single long injection are readily observed, ultimately resulting in high-temperature combustion and PAH structures appearing farther upstream after the end of injection. For the second injection in this work, the first formaldehyde signal is significantly advanced because of the entrained high-temperature combustion products, and an obvious premixed burn event does not occur. The propensity for combustion recession after the end of the first injection changes significantly with ambient temperature, thereby affecting the level of interaction between the first- and second injection.

Features of transformation of water projectiles moving through high-temperature combustion products

2016 ◽  
Vol 42 (3) ◽  
pp. 256-259 ◽  
Author(s):  
R. S. Volkov ◽  
M. V. Zabelin ◽  
G. V. Kuznetsov ◽  
P. A. Strizhak
Keyword(s):  
High Temperature ◽  
Combustion Products ◽  
Temperature Combustion ◽  
High Temperature Combustion
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