Supersonic combustor modeling

The physical phenomena involved when a supersonic flow undergoes chemical reaction are discussed. Detailed physical models of convective and diffusive mixing, and finite rate chemical reaction in supersonic flow are presented. Numerical algorithms used to solve the equations governing these processes are introduced. Computer programs using these algorithms are used to analyze the structure of the reacting mixing layer. It is concluded that, as in subsonic flow, exothermic heat release in unconfined supersonic flows retards fuel/air mixing. Non mixing is shown to be a potential problem in reducing the efficiency of supersonic as well as subsonic combustion. Techniques for enhancing fuel/air mixing and combustion are described

Supersonic reacting internal flow fields

The national program to develop a trans-atmospheric vehicle has kindled a renewed interest in the modeling of supersonic reacting flows. A supersonic combustion ramjet, or scramjet, has been proposed to provide the propulsion system for this vehicle. The development of computational techniques for modeling supersonic reacting flow fields, and the application of these techniques to an increasingly difficult set of combustion problems are studied. Since the scramjet problem has been largely responsible for motivating this computational work, a brief history is given of hypersonic vehicles and their propulsion systems. A discussion is also given of some early modeling efforts applied to high speed reacting flows. Current activities to develop accurate and efficient algorithms and improved physical models for modeling supersonic combustion is then discussed. Some new problems where computer codes based on these algorithms and models are being applied are described

Effects of fluid flow on corrosion behaviour in pipe bends

Correlation on flow induced corrosion (FIC) for straight pipes and bends have been obtained by researchers via a two-dimensional numerical method and experimental techniques. However, for pipe bends, the correlations require further improvements as the flow in bends are more complicated. The objective of this research is to obtain more accurate correlations for FIC in bends using twodimensional and three-dimensional numerical and experimental techniques. In the numerical and experimental approach, several important parameters such as Reynolds number and selected discrete particle model (DPM) were used to obtain erosion rate for miter and smooth bend models. Validations for the modellings were compared with experimental results and locations of the eroded sections were observed to be in agreement. Then, the erosion rates were extracted and analyzed using shooting method. Finally, the new coefficients for the correlations were obtained. When the new equations were applied to the same two-dimensional models, it was shown that the previous two-dimensional models had over-predicted the mass transfer values. Furthermore, when comparisons were made between smooth and miter bends results under the same flow conditions, it was observed that mass transfer values calculated from miter bend models were much higher than that of smooth bends. Experimental results also showed similar behavior, when the surface morphology was examined under Field Emission Scanning Electron Microscope (FESEM). From numerical and experimental approach conducted, it is concluded that the inner diameter bends were the areas with the highest FIC behaviour for 300 and 450 smooth and mitre bends

Numerical study of high temperature heat exchanger and decomposer for hydrogen production

This dissertation deals with three-dimensional computational modeling of a high temperature heat exchanger and decomposer for hydrogen production based on sulfur-iodine thermochemical water splitting cycle, a candidate cycle in the U.S. Department of Energy Nuclear Hydrogen Initiative. The conceptual design of the shell and plate decomposer is developed by Ceramatec, Inc. The hot helium from a nuclear reactor (T=975°C) is used to heat the SI (sulfuric acid) feed components (H2O, H2SO4 , SO3) to get appropriate conditions for the SI decomposition reaction (T\u3e850°C). The inner wall of the SI decomposition part of the decomposer is coated by a catalyst for chemical decomposition of sulfur trioxide into sulfur dioxide and oxygen. The proposed material of the heat exchanger and decomposer is silicon carbide (SiC); According to the literature review, there is no detailed information in available publications concerning the use of this type of decomposer in the sulfur-iodine thermochemical water splitting cycle. There is an urgent need for developing models to provide this information for industry. In the present study, the detailed three-dimensional analysis on fluid flow, heat transfer and chemical reaction of the decomposer have been completed. The computational model was validated by comparisons with experimental and calculation results from other researchers; Several new designs of the decomposer plates have been proposed and evaluated to improve the uniformity of fluid flow distribution in the decomposer. To enhance the thermal efficiency of the decomposer, several alternative geometries of the internal channels such as ribbed ground channels, hexagonal channels, and diamond-shaped channels are proposed and examined. It was found that it is possible to increase the thermal efficiency of the decomposer from 89.5% (baseline design) up to 95.9% (diamond-shaped channel design); The calculated molar sulfur trioxide decomposition percentage for the baseline design is 64%. The percentage can be increased significantly by reducing reactants mass flow rate and with increasing channel length and operation pressure. The highest decomposition percentage (∼80%) for the alternative designs was obtained in the diamond-shaped channels case; The sulfur dioxide production (throughput) increases as the total mass flow rate of reacting flow increases, regardless of the fact that the decomposition percentage of sulfuric trioxide decreases as total mass flow rate of reacting flow increases

Experimental Investigation of Nozzle/Plume Aerodynamics at Hypersonic Speeds

The work performed by D. W. Bogdanoff and J.-L. Cambier during the period of 1 Feb. - 31 Oct. 1992 is presented. The following topics are discussed: (1) improvement in the operation of the facility; (2) the wedge model; (3) calibration of the new test section; (4) combustor model; (5) hydrogen fuel system for combustor model; (6) three inch calibration/development tunnel; (7) shock tunnel unsteady flow; (8) pulse detonation wave engine; (9) DCAF flow simulation; (10) high temperature shock layer simulation; and (11) the one dimensional Godunov CFD code

Institute for Computational Mechanics in Propulsion (ICOMP) fourth annual review, 1989

The Institute for Computational Mechanics in Propulsion (ICOMP) is operated jointly by Case Western Reserve University and the NASA Lewis Research Center. The purpose of ICOMP is to develop techniques to improve problem solving capabilities in all aspects of computational mechanics related to propulsion. The activities at ICOMP during 1989 are described

A numerical study of detonation diffraction

An investigation of detonation diffraction through an abrupt area change has been carried out via a set of two-dimensional numerical simulations parameterized by the activation energy of the reactant. Our analysis is specialized to a reactive mixture with a perfect gas equation of state and a single-step reaction in the Arrhenius form. Lagrangian particles are injected into the flow as a diagnostic tool for identifying the dominant terms in the equation that describes the temperature rate of change of a fluid element, expressed in the shock-based reference system. When simplified, this equation provides insight into the competition between the energy release rate and the expansion rate behind the diffracting front. The mechanism of spontaneous generation of transverse waves along the diffracting front is carefully analysed and related to the sensitivity of the reaction rate to temperature. We study in detail three highly resolved cases of detonation diffraction that illustrate different types of behaviour, super-, sub- and near-critical diffraction