US3004494A

US3004494A - Turbine driven pump inducer

Info

Publication number: US3004494A
Application number: US696418A
Authority: US
Inventors: Marshall J Corbett
Original assignee: Thompson Ramo Wooldridge Inc
Current assignee: Northrop Grumman Space and Mission Systems Corp
Priority date: 1957-11-14
Filing date: 1957-11-14
Publication date: 1961-10-17
Anticipated expiration: 1978-10-17

Description

Oct. 17, 1961 M. J. coRBETT TURBINE DRIVEN PUMP INDUCER Filed Nov. 14, 1957 l l l United lStates Ohio Filed Nov. 14, 1957, Ser. No. 696,418

` 6 Claims. (Cl. 103-88) 'The present invention relates to improvements in pump assemblies, and especially those provided with an inducer for preventing cavitation.

In pump operating conditions where cavitation is likely to occur, such as where the intake of the pumpv is connected to a high lift, or where a high temperature or volatile fluid is being pumped, means have been provided heretofore for reducing cavitation, such as by providing an inducer on the intake of the pumpwhich maintains a slight pressure on the pump intake side. In a pump which has a variable output, it is not necessary that the inducer run at -full capacity for small outputs, sincev this will result in a waste of power, and will merely create turbulence at these low ow conditions.v With the use of a rotary or centrifugal pump, a simple inducer has been provided heretofore which consists of another small rotary pump mounted on the same shaft as the main pump. However, at low liow conditions, the inducer will continue to be driven at high speed and will consume a substantial amount of power, which is wasted.

Accordingly, it is an important object of the invention to provide an inducer for a pump which operates to prevent cavitation and will operate eiciently and satisfactorily at varying pump outputs, and will not consume an unwarranted amount of power at low pump outputs.

Another object of the invention is to provide an inducer for a pump wherein the output of the inducer will vary in accordance with the output of the pump, thereby elimiarent nating the waste of power which will normally occur at low output of the pump.

Another object of the invention is to provide an improved flow inducer for a pump which is driven by fluid, and more specifically is driven by fluid by-passed from the pump output. Y

Another object of the invention is to provide an im` proved pump assembly, such as that which employs a centrifugal pump wherein a rotary pump inducer is provided on the input side of the pump to reduce cavitation,

`and. wherein the impeller is driven by a iiuid turbine operated by fluid by-passed from the pump output, and wherein the turbine operating lluid liow is controlled in accordance with the ow output of the pump. l

Other objects -andadvantages will become more apparent inconnection with the disclosure and teaching of the principles of the invention in the description and illustration of the preferred embodiments thereof, in the specification, claims and drawings, in which:

FIGURE 1 is a somewhat diagrammatic view shown in elevation of the pump assembly; and

FIGURE 2 is a vertical sectional view 4taken through the pump assembly and showing the details of construction thereof.

As shown in the drawings:

The pump 'assembly is iuustrned in FIGURE 1 with a pumping unit 4 provided with an inlet line ytdeiining an inlet passageway 8, as shown in FIGURE 2, which leads to an inlet chamber 10 adjacent a pump chamber 12. Y

The pump chamber 12 is enclosed in a pump housing v nism which is indicated generally by location at 18 in FIGURE 1.

Within the pump housing 14, and within the pump chamber 12, is a rotary centrifugal pump impeller 20. The impeller is driven by a power-driven rotary shaft 22 upon which the rotary impeller 20 is mounted. For mounting the impeller, it is provided with a shaft receiving bore 24 which leads to a smaller bore 26 for the passage of a bolt 28. The bolt 2S is threaded into a threaded opening 30 inthe power-driven shaft 22 and draws the shaft tightly Vinto the bore 24 with a head 31 of the bolt resting on the upper shoulder 32 of a central hub 34 ofthe impeller.

The impeller is provided with the usual openings 36 which extend axially from the intake end of the impeller and curve out to open radially into the pump chamber 12. The chamber 12 will normally be volute shaped and lead into the discharge passageway 16.

The pump housing 14 is provided with a iirst annular seal 38 extending around the intake end of the pump rotor, and a second annular seal 40 surrounding a flange 42 at the back end of the rotor.

The pump housing 14 may be manufactured by being cast in parts in such a manner so that it may be assembled with the impeller 20 therein, as shown in FIGURE 2. The sections 14 and 15 of the housing assembly are held together by having annular iianges 43 and 44 respectively, through which pass bolts 46, which clamp the sections together.

An inducer 48 is provided to supply iiuid to the intake chamber 10 to flow into the passageways of a pump -impeller at a slight pressure to avoid cavitation. These problems of cavitation occur with high speed pumps, and are especially troublesome when high lifts are encountered, and when high temperature or volatile materials are pumped. This is frequently true with pumping high temperature fuels or the like, and in a fuel pump the pump frequently operates continually to maintain pressure in the `discharge passageway 16. The discharge flow varies over a wide range, and may vary from zero delivery to maximum delivery of the pump.

The inducer 48 is of the nature of a rotary pump having fluid impeller blades). When the inducer is driven in rotation, a pressurized ow of fluid will be driven forward through the intake passageway of the pump and through the intake chamber 16. The rot-ary inducer is mounted for rotation on a shaft 52 which is supported within the intake passageway 8 on arms 54 and 56 of a spider.

The inducer blades 50 are mounted on a central hub 58 at their inner ends, and are secured at their outer ends to an annular band `6i). Carried on the outer surface of the annular band are a plurality of turbine blades 62. The lband 60 thus separates the inducer blades 50 from the turbine blades 62.

Operating fluid for driving the turbine which is oomprised of the turbine blad-es 62 mounted on the band 60, is received from slots 64 leading from an annular turbine fluid supply chamber 66.

In accordance .with the principles of the present invention, iiuid is lay-passed from the output of the pump and this fluid is transformed to useful power for driving an inducer mechanism. As will be seen from the description vof the operative elements, the flow of by-pass fluid is controlled so that the inducer will have an output in accordance with the output delivery flow of the pump.

In the present embodiment of the invention, the inducer is in the form of a rotary iluid impeller driven by a turbine which derives its operating uid through a by-pass line 68, FIGURE l, which leads into the supply chamber 66, FIGURE 2, for the turbine. The bypass line 68 connects directly to the discharge passageway 16 of the pump and may be relatively small as compared to the output passageway, since a relatively small quantity of iluid is required for driving the inducer.

In the form illustrated, a control valve 7,0 is provided to control the amount of Y fluid flowing through the bypass line to drive the inducer. Thus, the inducer may be driven only ata speed sulieient to deliver fluid to the intake .of the pump to prevent cavitation. These cir.- cumstances may vary with the pump characteristic, the fluid pumped, `the height of fluid, and the temperature of the iluid, and other variable factors.

The huid delivered by the inducer 48 may also be varied in accordance with the output of the pump. This may be achieved by selecting valve 70 to be a howresponsive valve which will control the flow through the by-pass line 163 in accordance with the How through the pump discharge line 16. In one form, the llow control valve '70 may have a small control sensing line '72, FIG- URE l, which connects directly to the line 16, and which senses the ilow of fluid therethrough. Inasmuch as there e Thus, a .Condition such as which occurs when an inducer is mounted directly on a pump shaft, wherein a large amount of power is consumed by the inducer at low outputs of the pump and turbulence occurs, is completely eliminated.

I have, in the drawings and specification, presented a detailed disclosure of the preferred embodiments of my invention, and it is to be understood that I do not intend to limit the invention to the Vspecic form disclosed, but intend to cover all modifications, .changes and alternative constructions and methods falling within the scope of the principles taught by my invention.

`I claim as my invention:

l. A pumping unit adapted t0 operate under vhigh speed and high lift or high .temperature conditions 4with an absence of cavitation comprising in combination a rotary power-driven pump centrifugal impeller unit, `a

` housing surrounding the impeller unit and having a pump the output ilow through the line 16 is reduced, the ilow v through the by-pass line 68 is similarly reduced, thus reducing the power required to drive the inducer. As will be appreciated by those skilled in the art, in a rst type of fluid system where the output of a constant speed pump is connected to a line with a variable demand, when the demand increases the output pressure of the pump will drop and when the demand decreases the output pressure will increase. Also in a second type of system the pump may be used in an arrangement where the pump rotor is driven at a variable speed, and to meet increased demands the Speed of the pump is increased, thus increasing the output pressure. In both systems the increased output of the pump rotor is accompanied by an increased by-pass to increase the output of the inducer. ln order to operate according to ilow variation, as above described, in the first system the llow sensing valve 70 opens as a function of the decrease in pressure in the output line 16. In the second system the flow sensing valve opens as a function of the increase in pressure in the output line i6.

At minimum flow conditions, the operation of the inducer 48 can be reduced to a minimum, or in some instances stopped. This will reduce the turbulence which will be created in instances where an inducer is mounted directly on the pump shaft. In these installations, a considerable waste of power occurs at low output, since the power consumption of the inducer will be relatively high.

With the structure of the present invention, however, the power consumption of the inducer is maintained at a minimum and only the power needed is used. The uid which is by-passed to drive the inducer is delivered back into the ow stream, passing into intake chamber 10, and again owing through the pump impeller 20.

ln operation of the pump, the shaft 22 will be power driven to rotate the impeller 201, and fluid will flow through the intake passageway 8, and the intake chamber l@ to flow out through the discharge passageway 16. A portion of fluid from the discharge passageway isv bypassed through the by-pass line 68 and this fluid reacts against the turbine blades 62 to drive the coaxial impeller 4S and deliver fluid under a slight pressure to the intake of the pump thereby reducing cavitation. The control valve 70 in the bypass line controls the amount of tiuid flowing to the turbine so that at reduced or mini.- mum dow output of the pump, a minimum amount of by-pass fluid is used to drive the inducer.

Thus it will be seen lthat I have provided an improved pump assembly which provides an inducer consuming a minimum of power for efficient and satisfactory operation. The power consumption of the inducer is main.- tained at a minimum throughout the entire range ,of 011tput of the pump, and at a minimum output, ythe power consumption of the inducer may even be reduced to zero.

discharge passageway and a pump intake chamber, a rotary inducer impeller mounted in said intake chamber in close proximity to the impeller unit, a supporting shaft carrying said inducer impeller, an annular band surrounding'said inducer impeller, a series of huid-driven turbine blades mounted outside of `said band, a turbine housing surrounding said blades outside of said pump intake chamber and operative to deliver pressurized fluid to said turbine blades to drive the blades and the inducer impeller whereby fluid delivered to the intake chamber to the centrifugal pump is pressurized fluid to prevent cavitation, a by-pass fluid flow passageway connected between the turbine housingand the pump discharge passageway whereby -pressurized fluid delivered by the centrifugal pump impeller will flow to the turbine impeller and drive the turbine and inducer impeller at a speed to deliver pressurized fluid to the centrifugal pump impeller and prevent the occurrence of cavitation, and a fluid flow control by-pass valve in said by-pass line to determine the amount of fluid which will be by-passed and the power used for driving the turbine, said valve being pressure responsive and connected to the discharge passageway and operative to reduce the flow path for fluid through the by-pass line to decrease the speed of operation of the turbine and the speed of the inducer impeller at high pressures and low flow outputs of the centrifugal pump impeller.

2. A cavitation preventing pump assembly for pumping high temperature uids or high suction lifts comprising in combination a pump enclosed in a housing 'having an inlet passageway and a' discharge passageway for the ow of pumped fluid, a rotary uid impeller having impeller blades connected to deliver fluid to said pump intake passageway, a iluid driven rotary motor having reaction elements radially spaced outwardly from the impeller blades and mounted for corotation with the uid impeller and driving the impeller in rotation, an inwardly tapered guide surface leading from the discharge of said rotary motor to said inlet passageway for said pump guiding the path of fluid discharge from the reaction elements inwardly to the inlet passageway, and a'uid ilow by-pass passageway connected to bleed uid from the pump discharge passageway and deliver the iluid to drive the rotary motor in accordance with the output of the pump.

3. A cavitation preventing pump assembly for pumping high temperature fluids or high suction lifts omprising in combination a main pump enclosed in a housing having an inlet passageway and a discharge passageway for the ow of pumped uid, an inducer connected to said inlet passageway and operative to deliver fluid to said pump thereby reducing cavitation, iluid powered driving means connected to drive said inducer, a by-pass conduit connected between the pump discharge passageway and said driving means to drive said driving means in accordance with the output of said pump, a flow control valve in said by-pass conduit whereby the amount of uid operv ating the driving means may be regulated with varying pumping conditions, and a llow responsive valve control connected to operate said ow control valve and connected to said pump discharge passageway and operative to reduce the size of the ow path through the valve corresponding to decreased output of said pump so that the inducer output is reduced to a low quantity.

4. A cavitation preventing pump assembly comprising in combination a pump having a rotor with an axial intake enclosed in a housing having an axial inlet passageway and a discharge passageway for the flow of pumped fluid, a rotary iiuid liow inducer positioned in the intake passageway of the pump coaxial with said pump rotor and in close proximity thereto to deliver fluid to said pump, a rotary Huid `driven motor positioned coaxially with said flow inducer and coaxially with said pump rotor and connected to drive the inducer, a fluid llow by-pass passageway connected to bleed fluid yfrom the pump discharge passageway and deliver the fluid to drive the rotary motor in accordance with the output of the pump, and an annular discharge passageway 'for said rotary motor coaxial Awith said pump rotor communicating with said pump intake passageway in an annular flow path so that the Huid yfor operating the motor will again pass through the pump.

5. A cavitation preventing pump assembly comprising in combination a pump having a rotor with an axial intake enclosed in a housing having an axial inlet passageway and a discharge passageway efor the flow of pumped lluid, a rotary llow inducer positioned in the intake passageway of the pump having an axial flow rotor coaxial with said pump rotor to deliver fluid to said pump, a rotary uid driven motor for said inducer including vanes annularly arranged on the periphery of said inducer rotor so -as to =be coaxial with said pump rotor and in close proximity thereto and so that iluid passing therethrough will be discharged in an annular path around said inducer rotor coaxial with the pump rotor, and a Huid iiow bypass passageway connected to bleed uid from the pump discharge passageway and deliver the uid to said vanes to drive the motor in accordance with the output of the pump with said 'bled uid passing coaxially through the pump rotor after operating said motor.

6. A cavitation preventing pump assembly for pumping high temperature uids or high suction lifts comprising in combination a pump enclosed in a housing having -an inlet passageway and a discharge passageway for the iiow of pumped fluid, the pressure in the discharge passageway varying as -a function of the rate of flow through the passageway, an inducer connected to said inlet passageway and operative to deliver iiuid to said pump thereby reducing cavitat-ion, fluid powered driving means connected to drive said inducer, a by-pass conduit connected between the pump discharge passageway and said driving means to drive said driving means in accordance with the output of said pump, a ow control valve in said by-pass conduit whereby the amount of fluid operating the dniving means may be regulated, and pressure responsive means connected to said pump discharge passageway and connected to said iiow control valve to open said valve in response to change in discharge pressure occurring with an increase in the discharge of the pump and to close said valve in response to change 1in discharge pressure occurring with a decrease in discharge of the -pump so that the ow path of the by-pass conduit will be varied with pump output and fluid will ibe by-passed as an increasing function of increase in delivery of the pump.

References Cited in the le of this patent UNITED STATES PATENTS 941,834 Wing Nov. 30, 1909 1,093,116 Cubelic Apr. 14, 1914 2,141,022 Rutter Dec. 20, 1938 2,502,241 Yates Mar. 28, 1950 2,733,662 Hunter Feb. 2, 1956 2,748,711 Drude June 5, 1956 2,752,858 Benges July 3, 1956 2,781,831 Angell Feb. 19, 1957 2,814,928 Davies et al Dec. 3, 1957 2,889,780 Binford June 9, 1959 FOREIGN PATENTS 564,826 Germany Nov. 23, 1932 938,054 France Sept. 3, 1948