A study of the thrust augmentation arising from the application of ejectors to high pressure reaction control systems typical of VSTOL aircraft is presented. A numerical analysis was undertaken to identify parameters critical to the attainment of high performance. A novel technique for improving mixing in confined ejector flows was investigated experimentally.

Theoretical work considered configurations with both sonic and supersonic primary flows. The studies show that thrust augmentation ratios ⋍ 1·3 are possible at pressure ratios around 15 using an ejector area ratio of 35. Little benefit accrues from diffusion at high pressure and performance is sensitive to mixing efficiency in terms of the mixing duct exit flow uniformity and primary nozzle losses.

Jets issuing from underexpanded nozzles fitted with castellations around their exit were compared experimentally with those leaving plain nozzles. Significant improvements in jet entrainment rates arise from the castellations. Strong correlation is observed between the free jet mixing rate and ejector secondary thrust. The level of thrust augmentation is low in conventional terms but constitutes a significant improvement over plain nozzle ejectors and non-augmented convergent nozzles.

Measurement methods using holography are non-invasive, whole-field and can be applied in real-time. They are particularly appropriate for experimental validation of current CFD (computational fluid dynamics) codes which have 3-dimensional, transient, irregular geometry capabilities.

In holographic interferometry, the fringes formed by refractive index changes represent lines of constant Mach number in isentropic compressible flows and isotherms in convection. Examples are given of two-dimensional inter-ferograms in these areas, and their quantitative interpretation.

Automatic fringe and data processing is a necessity, and the method is extendable to three dimensions using tomographical reconstruction. These issues are discussed, together with the general question of comparison with flow predictions.

Fluid fields may also be treated on a three-dimensional time-dependent basis, using HCV (holocinematographic velocimetry), a holographic extension of PIV (particle image velocimetry). It is proposeds to run an experiment to measure both fluid and thermal fields, and surface temperatures simultaneously, using HCV or PIV, holographic interferometry and liquid crystal methods respectively.

This study examines the performance of two axisymmetric nozzles which were designed to produce uniform, parallel flow with nominal Mach numbers of 4 and 8. A free-piston-driven shock tube was used to supply the nozzle with high-temperature, high-pressure test gas. The inviscid design procedure treated the nozzle expansion in two stages. Close to the nozzle throat, the nozzle wall was specified as conical and the gas flow was treated as a quasi-one-dimensional chemically-reacting flow. At the end of the conical expansion, the gas was assumed to be calorically perfect and a contoured wall was designed (using Method-of-Characteristics) to convert the source flow into a uniform and parallel flow at the end of the nozzle. Performance was assessed by measuring Pitot pressures across the exit plane of the nozzles and, over the range of operating conditions examined, the nozzles produced satisfactory test flows. However, there were flow disturbances in the Mach 8 nozzle flow that persisted for significant times after flow initiation.