Precision Jet Drive
The History of Inducers:
Inducers by them selves are axial flow impellers commonly found in personal water craft like Jet skis, Sea Doo's, Wave Runners, also used in recirculation pumps.
Designed In The Early Days of Rocket Development two conflicting demands were made on the turbine pumps used; high delivery pressures at low flows, and the need for low weight, which led to high driving speeds and small size. The main problem was limitation of cavitation. Unconventional boosters or inducer stage was applied to the centrifugal impeller, to meet the problem by reducing the required NPSH (Net Positive Suction Head). The inducer was and is a high solidity axial flow impeller having few blades, which follow an Archimedean spiral like a screw thread spiral, though more advanced designs have variable lead geometry. The inducer is placed in front of the main impeller in the suction area, and has the blades set at a very shallow angle to the peripheral direction, so that in a short axial length the blade passages are long. A recent contribution by Lakshminarayana (Fluid Dynamics of inducers - Journal of Fluids Engineering, December 1982, 104, pp 411-427) gives many references to the studies made on such machines and is a very useful summary of both the experimental data and the analytical approaches that have been made to their design and behavior. The best possible design is to approach the impeller - inducer combination with a view to optimizing performance, giving good cavitation behavior and efficiency. This involves matching diameters in the suction and ensuring that the inlet angles of the impeller blades are suited to the anticipated flow directions in the space between inducer and impeller. There are obvious problems posed by the complicated flow patterns between the inducer and the impeller, noting that it is unlikely that the number of inducer blades will be the same as in the impeller. pumps equipped with inducers can operate at double the speed of conventional pumps and still have the same suction capability or NPSH. Double the speed means smaller size. Variable temperature or NPSH may cause cavitation within a pump. An inducer can prevent this problem. Cavitation results in vibration and excessive wear of mechanical seals, bearing, and shaft. There has been no excessive wear of inducers when handling liquids such as condensates, which are known to cause severe pump damage when cavitation occurs. Tests have shown that even under induced cavitation there is minimum vibration with an inducer-equipped pump. In many cases it is possible to fit inducers into existing pumps at a reasonable cost range of flow rates. It is an essential requirement that a pump with an inducer is safely operational over the total capacity range: startup, part load, full load, and standby. Three factors are critical at part load NPSH performance, possible cavitation damage to the impeller, and the vibration level. Inducers have a positive influence on the recirculation (backflow) at a pump's impeller in the suction area and reduce vibration of a centrifugal pump at part load. This is important for the wear and life of bearings, seats, and shaft. In recent years the inducer has therefore been offered by manufacturers as an extra add on option to cope with low NPSH applications. Examples of various liquids pumped with inducers: Ammonia, Water H2O, gas oil, liquid gas, black liquor gas, hexan oil, light hydrocarbons polymers, fuel oil, gasoline, crude oil, chlorine, tar oil, sea water, methanol, vinegar .
Precision Jet Drive has been a source manufacture of inducers for many major pump mfg sense the early 1990's in cryogenic pumps: ACD Airco Cryogenic Div., Rotoflow, Cryocal, Cryostar USA. and in water pumps: Flowserve pump div., Byron Jackson, Ingersoll Rand, Pacific Pump, Peerless Pump, Goulds Pump, ITT Barton, Tasco Pump, These Company's referred to inducers with many deferent names: Pre Impeller, Pre Loader, Auger, Coke Crusher, Inducer, and have anywhere from 1-10 blades depending on blade pitch and or large diameter of the inducer and application of the main impeller.
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