Computational study of SCRAM Jet combustor with a co-axial strut fuel injector
The geometric configuration of Supersonic Combustion Ramjet (SCRAM) is relatively simple when compared to gas turbine engines as there are no moving parts, but the flow physics associated with it is quite complex. At high speeds of flight the residence time of the atmospheric air in the combustion chamber is very low it is of the order of milliseconds, within this short time the fuel injected in to air must efficiently mix and react to release energy in the combustion chamber. The Combustor length and Weight can be minimized and Thrust produced can be maximized by rapid and effective mixing of fuel and oxidizer. The present study focuses on using coaxial type fuel injectors and studies the characteristics of SCRAM Jet Engines. From the results obtained it is observed that the turbulence kinetic energy of the coaxial jets is improved by the four times at the point of fuel injection when compared with the circular jet injector. As Turbulent kinetic energy is one of the parameter indicating the mixing of the fuel and oxidized (air), it is concluded that by employing the coaxial strut fuel injectors the mixing of fuel and oxidized can be enhanced.
The CFD Analysis of Turbulence Characteristics in Combustion Chamber with Non Circular Co-Axial Jets
Co-Axial jets have applications in areas where the mixing of two fluid jets are necessary, the two fluid jets can be effectively mixed by producing the turbulence flow. Turbulence is a chaotic behavior of the fluid particles that comes in to picture when the inertia force of the flow dominates the viscous force and it is characterized by the Reynolds Number. Co-axial jets are effective in producing the turbulence. In the present study the free compressible turbulent coaxial jet problem will be computed using CFD, and compare with different non circular coaxial jets based on constant hydraulic diameter and mass flow rate. Turbulence characteristics of combustion chamber with circular coaxial and non circular coaxial jets are determined and
In search of optimum chest radiography techniques.
A nation-wide study of chest radiography in Sweden had previously revealed a large variation in the physical and technical factors involved, in particular the radiation dose. In this study the image quality could not be assessed unambiguously. The aim of the present study was to try to establish a correlation between visual grading of radiographs and physical and technical factors in order to find the optimum chest X-ray system. The physical and technical performance of 24 chest units was evaluated. Radiographs were taken of an anthropomorphic chest phantom supplied with test structures simulating various pathologies. Image quality was assessed by visual grading analysis of the radiographs. The physical and technical parameters of the units rated best were used to exemplify good radiographic practice. The results were in agreement with the recommendations issued by the Commission of the European Communities (CEC). It was also shown that low radiation dose is compatible with high-quality radiographic imaging of the chest.