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From the Rolls-Royce experimental archive: a quarter of a million communications from Rolls-Royce, 1906 to 1960's. Documents from the Sir Henry Royce Memorial Foundation (SHRMF).
Test report on gear-type hotwell pumps and injectors for evaporatively cooled engines.

Identifier  ExFiles\Box 179b\4\  img002
Date  1st April 1933
  
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to be left ticking-over for long periods with occasional opening up to 1200 R.P.M. (every 1/2 hr) to clear the hotwell.

(2) The use of a finned centre section wing condenser to deal with the condensate at tick-over speeds, this condensate draining back under gravity into the main water system.

TESTS OF THE GEAR TYPE HOTWELL PUMP.

Tests were done on two pumps on the Installation Hangar lifting water 3' from an open sum and pumping it into the main water system, and on a third pump on the Universal Hangar using a complete evaporatively cooled system with a hotwell 3' below the main water pump.

Although two of the pumps were almost new and had done very little running, they all had the same characteristics. Unprimed, they would not pick up below 2500 R.P.M. when the engine was running evaporatively cooled, and sometimes they would not pick up at any steady speed, but required violent throttle movements to give rapidly varying pressures in the suction pipe and hence to start the water in the suction pipe swinging. Using this method of rapidly varying engine R.P.M. the pumps could always, although sometimes with difficulty be made to pick up the hotwell water. A hotwell pump would then empty the hotwell with extreme rapidity (about 7 1/2 galls. per minute), start sucking air or steam together with the condensate and deprime itself, ceasing to work. This happened at every engine speed with unfailing regularity, and no hotwell pump could be made to work for more than a few seconds at any engine speed.

TESTS OF INJECTORS.

Development work was first done both on a rig using cold water and on the Installation Hangar using an evaporatively cooled engine. Later a series of tests were made using a complete evaporatively cooled installation on the Universal Hangar.

The first series of tests showed the difference in efficiency using hot and cold water with different sizes of nozzle and venturi. It was found that a serious decrease in efficiency resulted when using hot water unless the venturi throat diameter was considerably larger than the nozzle diameter owing to local boiling taking place. The best size for the Venturi diameter is from 1 1/2 to 2 1/2 times the nozzle diameter for which sizes the decrease in efficiency when using boiling water is only about 20%.

In order to avoid large depressions in the venturi throat of the injector it should be mounted below the hotwell and not
  
  


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