Abstract
Centrifugal pumps and compressors perform the same function of fluid transference; a boiler feed pump also operating as a turbo-compressor, when deprived of water, illustrates the design problems involved in each sphere of duty. Water turbines are reversed pumps. Pump design theory has in the past been unnecessarily complicated; in contrast, a simple system taking into account the combination of impeller and casing gives satisfactory results over the whole range of size, specific speed and characteristics. Flow passage geometry, with exact knowledge of the accelerations in three dimensions, is attained by the concept of the impeller with its flow surfaces generated as a gear wheel, improving efficiency and cavitation performance. Critical speeds and mechanical failure modes illustrate the relationship of pumps to turbo-compressors. Experience of 20000 pumps and 700 water turbines from 5 gallons to 5 million gal/min (of which a statistically significant number were tested on site by the user's staff and instruments on a ‘no tolerance penalty/bonus’ contract) resulted in efficiency bonus payments ranging up to 10 per cent of the contract price. Worldwide, for comparable numbers, higher efficiencies have not yet been published. Imperial units are occasionally used to help mental arithmetic and to illustrate historical data.
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