| 1. |
- Dahlander, Petter, 1967
(författare)
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Source Term Model Approaches to Film Cooling Simulations
- 2001
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Film cooling simulations using Computational Fluid Dynamics (CFD) are very difficult and extremely computer power demanding. This thesis deals with the development of a method to save computer power for these types of simulations. The cooling air is injected using additions to the source terms of the discretised governing equations. Cell lengths up to about one or two cooling hole diameters are used, thereby precluding modelling of the detailed flow around each cooling hole. Three different models for distributing the source terms are evaluated. In the first model, the sources are distributed to only one cell, namely the cell closest to the cooling hole, resulting in a poorly penetrating jet. To obtain better jet penetration and to be able to better control the concentration of coolant at the wall, the second model distributes the sources as a line source. This model produced reasonable results for the heat transfer rate on a film-cooled nozzle guide vane but not for temperature comparisons on multi-row effusion-cooled plates. The results were found to be sensitive to some input parameters. The third model uses limited parts of source term fields, evaluated from the averaged solutions of detailed jet simulations. This model showed the best and most realistic injection of the coolant. Owing to the different qualities of the results, especially for the first and second models, the method should be seen as a ``last way out`` when it is not possible to make detailed 3D simulations of high quality due to a lack of computer power.
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| 2. |
- Skogsberg, Mikael, 1975, et al.
(författare)
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Fuel distribution visualization from an air-assisted injector in a spray chamber
- 2004
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Ingår i: Comodia 2004, Yokohama, 2-5 aug 2004.
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Konferensbidrag (refereegranskat)abstract
- Optical measurements have been performed to visualize the fuel distribution from an air-assisted GDI injector in a constant volume spray chamber. In the air-assisted injector, fuel droplet breakup occurs as the droplets are accelerated by the expanded air flow passing out through the injector nozzle. The injector design allows for two distinct modes of operation: stratified (low load) and homogenous (full load). Therefore, measurements were taken at back-pressure and temperature settings corresponding to both low and full loads, to investigate the influence of these variables on fuel distribution, droplet sizes and velocities in the two modes.Results from PDA measurements show that most of the droplet break-up occurs inside the nozzle. Downstream of the nozzle, rates of break-up and evaporation are low. The cause of the low breakup and evaporation rates downstream of the nozzle is believed to be the low relative velocity between the liquid fuel and the surrounding cold air jet.The fuel distribution has been visualized qualitatively by simultaneous MIE and LIF measurements with two intensified digital cameras in combination with a 266 nm YAG-laser.
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