The growing awareness of pollutant emissions from gas turbines has made it very important to study fuel atomization system, the spray wall interaction and hydrodynamic of film formed on engine walls. A precise fuel spray spatial distribution and efficient fuel air mixing plays important role in improving combustion performance. Cross-flow injection and film atomization technique has been studied extensively for gas turbine engines to achieve efficient combustion. Air blast atomizer is one of these kind of systems used in gas turbine engines which involves shear driven prefilmer secondary atomization. In addition to gas turbine combustor shear driven liquid wall film can be seen in IC engines, rocket nozzles, heat exchangers and also on steam turbine blades.
In our work we have used Eulerian Wall Film (EWF) [1] model to simulate the experiment performed by Arienti et al. [2]. In the Arienti’s experiment liquid jet is injected from a nozzle from the top of the chamber. Droplets shed from the jet surface due to primary and later secondary atomization in the presence of high shearing cross flowing air. Further liquid fuel particles hit the wall to form film, film moves subjected to shear from the gas phase. Liquid film can reatomizes due to subgrid processes like stripping, splashing and film breakup. In current study we have validated Arienti et al. [2] experimental data by modeling complex & coupled physics of spray, film and continuous phase and by accounting complex subgrid processes.
The full-scale fire testing of aircraft power plants has suggested that laboratory closed-vessel spontaneous ignition tests give results which are pessimistic for many practical applications. The results of a number of test programs involving specific configurations of hot and cool surfaces have indicated that, for a particular fluid, it might be possible to establish a thermal correlation which would enable the risk of ignition to be calculated at the design stage.
Tests have been carried out on two rigs, both incorporating a hot bottom plate surface onto which the test fluid was sprayed, the side walls and top plate being somewhat cooler. The first rig was a static rig in which top and bottom plate temperatures and the gap between them was varied. The effects of mixture strength, atomization, and wall materials were studied for kerosine, and the ignition temperatures for various fluids have been determined for a limited number of configurations.
The second rig consisted of a small wind tunnel in which the effect of air velocities up to 10 ft/sec and altitudes up to 20,000 ft were investigated. It is shown that air velocities up to 3 ft/sec have a large effect on spontaneous ignition temperatures.
A correlation based on gas temperature and distance from the nearest wall shows good agreement for the static and wind tunnel rigs and for closed-vessel tests of other investigations. An outline of the future program of work is given.
IN recent years, much attention has been given to spontaneous ignition problems because of the high skin temperatures of aircraft operating at high Mach numbers. The problem is not really new, however, since for many years aircraft engines have been operating with carcase temperatures above the laboratory closed vessel spontaneous ignition temperatures for fuels and lubricants, and installation engineers have collected a good deal of ad hoc data to justify the safety of particular power plants. FIG. 1 indicates the main risk areas for a typical subsonic by‐pass jet installation.
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