This thesis is intended to provide information whereby the design of exhaust diffusers can be placed on a sounder basis. Particular emphasis has been placed upon correlating local and overall heat transfer with various possible flow patterns and associated pressure recovery. The experimental work was performed mainly on a two- dimensional model of a supersonic parallel diffuser. For a range of initial total pressures, visual observations were made of the flow patterns developed in the diffuser together with the corresponding measurements of wall static pressure distribution and local heat transfer coefficients and fluxes. The effect of varying the area of the diffuser cross-section for the same upstream generating nozzle has also been studied. The static pressure recovery across the diffuser is found to reach a maximum at the transition from a normal shock to a multiple oblique shock system of diffusion. Mach number profiles measured at sections along the diffuser show that in the presence of shock waves and a positive pressure gradient, the flow is very much underdeveloped. Following a peak value near the diffuser entry, the heat transfer, which generally follows the static pressure distribution, fluctuates about relatively low values in the region of the shock patterns, but rises steadily when the flow becomes subsonic in the downstream section of the duct. In general, the mean level of heat transfer is found to be much greater than that predicted by conventional empirical equations for subsonic pipe flows. Further, on comparison between normal and oblique shock diffusion the former is found to give the higher level of heat transfer. The method of characteristics has been used to estimate analytically the wave patterns present in this diffuser, from which predictions have been made of wall static pressure distributions which are in good agreement with those measured. At a latter stage of the work the performance of model axi-symmetrical parallel diffusers of varying area and length was studied. In general, the static pressure distributions and flow patterns are very similar to those produced by the two-dimensional diffuser, but the axi-symmetric diffusers have a wider operating range and better pressure recovery. Within wide limits the performance is independent of diffuser length.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:602233 |
| Date | January 1963 |
| Creators | Baker, Peter John |
| Contributors | Saunders, O. A.; Martin, B. W. |
| Publisher | Imperial College London |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | http://hdl.handle.net/10044/1/13347 |
Page generated in 0.0015 seconds