Browsing by Author "Pienaar, D. v V."

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    Optimal design of intermittently operated subsonic-supersonic ejectors
    (South African Institution of Mechanical Engineers, 2002) Pienaar, D. v V.
    The optimal design for maximum run duration of intermittently operated subsonic-supersonic air-air ejector pumps of fixed geometry was investigated using an inviscid one-dimensional model of the mixing chamber. The study was confined to the case of matched static pressures of the primary and secondary air streams. An empirical correction factor was applied to the ID results in order to take approximate account of the two-dimensional velocity distributions at the inlet and outlet of the mixing chamber and of viscous shear forces. Optimisation of both the primary and secondary Mach numbers was found to yield significantly longer run durations than when the secondary is flow is sonic and just the primary Mach number is optimised. The most pronounced advantages of optimising both the primary and secondary Mach numbers were obtained in the range of high ejector performance. The main advantage is that an optimised ejector is physically smaller, and requires a smaller storage vessel than one that is not optimised.