US2955743A - Method and apparatus for preventing surging in fans, blowers, and turbocompressors - Google Patents

Description

Oct. 11, 1960 HmETosHl KusAMA ErAL 2,955,743

METHOD AND APPARATUS FOR PREVENTING SURGING IN FANS, BLOWERS, AND TURBO-COMPRESSORS Filed March 19, 1956 4 Sheets-Sheet 1 L, wwf/rr BMNW Afro/Hvar Oct. 11, 1960 METHOD AND APPARATUS Filed March 19, 1956 KUSAMA El' L IN FANS, BLOWERS, A

HIDETOSH A FOR PREVENTING SURGING ND TURBO-COMPRESSORS 4 Sheets-Sheet 2 INVENTORS Oct. l1, 1960 HIDETosHl KusAMA ErAL 2,955,743

METHOD AND APPARATUS FOR PREVENTING SURGING IN FANS, BLOWERS, AND TURBO-COMPRESSORS Filed March 19, 1956 4 Sheets-Sheet 3 IN VEN TORS miras/w ,rasa/YA .aw/80 75u17 qw@ @w Oct. 11, 1960 HIDE-rosHi KUsAMA ETAL METHOD AND APPARATUS FOR PREVENTING SURGIN IN FANS, BLOWERS, AND TURBO-COMPRESSORS Filed March 19, 1956 4 Sheets-Sheet 4 i AF/G. 4

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IN VEN TORS ArrOPA/fy UnitedState i at Y E i@ e 2,955,743

- Patented Oct. 11, 1960 Hidetoishi Kusama and Shigeru Tsuji, Tokyo-to, Japan, assignors to Ebara Manufacturing Co., Ltd., Tokyo, Japan, a corporation of Japan Filed Mar. 19, 1956, Ser. No. 572,551

4 Claims. (Cl. 2'30-19) The present invention relates to a method and apparatus for preventing the elect of surging in the compressed uid delivery line in conjunction with high-speed and high-pressure blowers or turbocompressors.

The uid tlow is steady, or practically so, in many installations of a blower and connected piping. Cases have been reported, however, in which marked periodic fluctuation has been superposed upon the main steady ow. This uctuation has been called surging In some cases of centrifugal compressors, the surging is a very important factor. Surging is more pronounced with centrifugal compressors than with fans; it may cause the compressor to become out of order, and it may limit the useful range of operation of the machine.

Surging occurs when operation is in a region in which the blower characteristic shows an increase in pressure with an increase in volume rate of flow. Surging does not occur when the blower characteristic shows a decrease in pressure with an increase in capacity. Surging tends to occur when the volume of the connected piping system is relatively large. A relatively large volume can be realized with relatively long pipes and large diameters.

Surging cannot be explained adequately in very simple terms because the action, like many vibratory actions, is quite complicated. Many different factors are involved, each of which is essential to the complete phenomenon.

It has heretofore been proposed to provide a by-pass to waste on the discharge side of the blower, thereby to operate the blower at a capacity above that for the peak pressure, thus eliminate surging.

Furthermore, it has heretofore been proposed to provide in an appropriate part of the delivery channel of the blower an opening controlled by a valve and to open such valve when the power of the blower falls.

Generally speaking, the heretofore proposed. methods for preventing the surging of blowers are enumerated as follows: (l) machine designers have endeavored to obtain the falling characteristic of the blower, even though the eli'iciency is considerably reduced; (2) blowers are operated in the safety region by discharging excess uid by a vby-pass to waste; (3) the operating capacity of the blower is controlled by a valve installed in the inlet channel; (4) the operation at reduced capacity is made possible by reducing the rotating speed.

The machine designer has remodelled the shape of an impeller, or a guide vane of a blower so that the blower can be operated in a stable region of the blower characteristic in order to obviate the surging. The eliciency of the blower, however, cannot help being reduced considerably by such remodelling of machine elements. Besides, the means such as, suction vane control and a variable speed motor, have been applied to disadvantage in respect of construction.

We have discovered that the above-mentioned surging can be eliminated eiectively by providing a surgepreventing valve on the discharge channel of the blower.

It is an object of our invention to provide a surge preventing device which is very simple in principle, but is subject to installation in any type of the blower.

Another object of the invention is to provide a surge preventing device generally useful and effective in a blower or compressor.

Another object of the invention is to provide a surge preventing device which minimizes the unfavorable effects of heavy surges and eliminates knocking and pounding of both large and small surges.

Another object of the invention is to provide a surge preventing device which eliminates the disagreeable effects of fluctuation in pressure and volume rate of ow caused by the surging and assures the smooth and continuous operation of the machine.

Another object of the invention is to provide an automatic surge preventing device which can proceed through a complete cycle of operation once its operation has been initiated.

An additional object of the invention is to provide a surge preventing device by which a considerable amount of power cost can be saved.

With the above and other objects in view that will hereinafterl appear, the nature of the invention will be more fully understood by following the detailed description, the appended claims, and the views illustrated in the accompanying drawings, in which:

Fig. 1 shows the characteristic curve of a blower, surging region, surging stable region, and resistance curves showing maximum and minimum limits of surge prevention, respectively.

Fig. 2 is a plan of the hydraulic control of our surge preventing apparatus.

Fig. 3 is a plan of the modified hydraulic control of the surge preventing apparatus of the invention.

Fig. 4 is a plan of the electronic hydraulic control of the surge preventing apparatus of the invention.

In the figures like reference characters indicate like parts. Referring more particularly to the drawings, Fig. l shows the characteristic curve of a blower and the connected piping system. The abscissa is the capacity or volume rate of ow. The ordinate is the pressure developed by the blower and the valves.

As the capacity increases, pressurel rst increases, reaches a peak, and then decreases. For the piping system the pressure drop increases as the velocity of flow increases. In `accordance with our invention, we provide a surge-preventing valve on the discharge channel of the lower. We call a valve heretofore employed in general a capacity-control valve. in the following disclosure the resistance value of the capacity-control valve in question includes various resistance values, such as, pipe friction and load in gener-al. Assume that a given volume of ow QB is obtained in the discharge channel of the blower with an appropriate opening of the capacity-control valve. The volume rate of ow QB is determined lineally by the resistance of the capacity-control valve. If the given volume rate of flow QB is found in the surging limit, then surging takes place. At the constant volume rate of ow QB, we throttle the surge-preventing Valve slowly, then we assume the resistance loss value of the first valve to be the value shown by hBl when surging ceases. The term, load means the space or chamber wherein the compressed liuid energy is consumed, and resistance loss value means the energy loss value. Again we throttle the surge-preventing valve and open the second valve with the same volume rate of ow QB, accordingly surging occurs again, then we assume the resistance loss value of the surge-preventing valve to be hBO. In accordance with the dilferent Volume rate of ow, we plot the curves OB1L1 and OB2L2. Surging occurs when A'the resistance loss value of the invention herein described are Y only, but not limited thereto.` As described'her'einbe-V surge-preventing valve isrfound in the lower region decurve OBlLl, and the absoissa, and the up- 'Y curve OBzLg, the characteristicV ned by the per region defined by the curve, and .the ordinate. i Consequently, the resistance loss value .ofthe surge-preventing valve Vis preferably to be found in the surging stable region, ekceptV the hatched regions shown by OAB4L2B2 and ,OBlLlBm Vin order Vto prevent surging. VThe resistance lossvalue of the capacity-control valve depends upon that ofthe surge-preventingA valve. For example, if the valuebf the,` surgeof new QB, the value of Ythecapacity-control valve is shown by B334. y t l Y v As described above, the'surge preventing `apparatus of our invention is a very s1mple `one*consisting of the. surge-preventing valve' provided on vthe dlscharge channel of the blower. The mathematicalY analysis of our invention will be found in oujr' article, Y'Transactions of VtheV Japan Society ofKMechanical Engineers, vol. 2,2, No.v

117 (1956). Though veryV simple inlprinciple, however, the preferred forms of the co-ntrol mechanismY of the surge-preventing valve'are enumerated as below, Itis to b e understood that the preferred embodiments of the for illustrative purposes preventing valve is shown Yby Bs at the volume rate the compressed lfluid of constant pressure is Vct'xntinuousrly Y delivered. i a Y i t The threemet'hods of control are as follows:v

(l) Hydraulic control. (2) Modified hydraulic control. (3) Electronic hydraulic control.

Now we explain the necessity of an air chamber 65 as shown in the drawings. The volume between two valves is important in order to prevent surging in accordance with the operationof two valves. lf the volume is below a predetermined volume for a given blower and its connected piping system, surging cannot be obviated by our` invention. VFor instance, our experiment has shown that theV volume between two valves must be at least 8O litresfor fa blower with capacity 1,500 mm. of the height of water column. Therefore an air chamber 65 is preferably` provided on the delivery channel 7.

Referring to Fig. 2, in event of our desire to control the volume rate of flow, we change the opening of Vthe Vcapacity-control valve plate by turning the hand wheel 17, then the varied volume rate of dow will result in the change of suction pressure at the inlet nozzle 5, thereby operating a servo-mechanism, i.e., .the liquid enclosed in the ring balance 51 will move to the direction of an larrowwhen the rate `of ow increases. 'Then the ring balancenSl will be shifted clockwise in order. to maintain,Y equilibrium. The cam 27 is secured to the shaft 53 of the ring baltmce 51 so that theV cam 27 will be shifted clockwise, therefore the piston 28 of the pilot valve or servo-valve 66 will slide downward so that the port 3G is in open communication with the port 37, and the oil delivered from )the oil accumulator 38 is Ysupplied throughV the Yconduit 49 into the lower spaceV of the servomotor 67, thereby the piston 33of the servomotor 67V will be lifted so that thesurge-preventing valve plate 3 willbe raised because the stem 9 of the valve plate 3 is secured tothe piston 33.` On the other hand, thelever 68 ofthe return or follow-up mechanism is held on the Y 4 Y Y t are in closed position, andthe pilot valve 66 and the piston 28 resume their initial positions.

Referring to Fig. 3,V the increased volume rate of flow by opening the capacity-control valve plate 4 actuated by the valve hand wheel 17 will result in the pressure difference between the two spaces of the actuator 42, thereby lalso operatingV a servo-mechanism, i.e., cause the diaphragm 43 to move in the direction ofthe arrow. The stem 44 is secured Vto the diaphragm 43, so that the stem 44 will move in the direction of the arrow. The swinging pipe Velement 69 of 'therdistributing valve 50 is held Yon the fulcrum'34,^so that the movement of the stern 44 will cause the swinging pipe element 69 .to move to the same direction as Ythe arrow. The portY 48 is in open communication with the port 32, sothe oil 39 delivered from the accumulator 3S will enterjthe lower'space of the servomotor 67 through the port 47, thereby Vpermit the pistonl 33 to lift upward, then the,v surge-preventing valve 3 is in open position. On the 'other hand, the oilY in thelower space of the servom'otorr'45 will entrer the upper space Vof theservo-valve cylinder 46 of the returnor follow-up mechanism throu'ghfthe port 70,

landV drive the piston 71 downward. Y In` consequence,

the swinging pipe element 69Y becomes stable, and resumes its initial position. y p Y Refeningto Fig 4, this control mechanism can be applied to the machine `in which the inlet nozzle 5 -is situated at the relatively long distance fromthesurgepreventing valve.v The increased volume rate of flow at the opening of the Ycapacity-control valve plate `4 actuated by the hand wheelr17 will Yresult in the depression of the air pressure in the lower space of lthe actuator 42, so that the diaphragm 43 is lowered operating a servo-mechanism. The rotor 72 ofthe self-synchronized motor 54 is linked to the stem 44 secured to the diaphragm 43, therefore the'downward movement Vof the diaphragm 43 ,will rotate the'rotor172` of .the self- Y synchronized motor 54 by means ofth'efst'em 44.V Consequently, it willV inlluen'ce the-intensity of the magnetic eld of the self-synchronized motor 54, the intensity will be transmitted to ythe self-synchronized motor-iY 56 Vby means of the circuit 55,Y then thev intensity of the magnetic field will vary, the amount of varied intensity will be Itransmitted to the secondary winding of a transformer 57. In other words, there is provided Va diaphragm motor responsive to the inlet pressure of Vsaid blower" and an Y electrical motorpresponsive Vto the movement of Ysaid fulcrum 34, and one end of thelever 68 is secured to diaphragm motor. The varied voltage herein-obtained will be amplified by the electron tubes l58y and 59,` `then transmitted to the field coil ofV a motor 60, w-hichY will-be energized to cause the rotor 73 of the motor'tofiperform the rotaryr motion. The rotation lof the rotor 73 Vwill shift the sliding-piece 62,7beoaus'e". the rotor 73V is Vconnected to the sliding-piece 62 of the vrheostat 61. An angle displacementv of the 'sliding-piece `62 corresponds lineally to the value of the pressure derived from `the inlet nozzle.V The resistance value of lthe rheostat 61 ischosen as it is proportional to the square` of the electric current; The current Ythrough the circuit 74n-is' amplified, and altered by the displaced angle of the sliding-piece. As the coil 63 is included in the circuit" 74 thefintensity of the magnetic field of the Vcoil 63 Varies as theV current varies, therefore it causes the viron core 64 of the coil to go downward, so that the rod connected thereto 'will be lowered. As the p iston'28of'the` pilot'va'lve.- 66 is connected to the Yrod, the oil delivered from the accumuylator 38 is suppliedathroughthe conduit .40 intolthe lower space of the servornotor 67,Y because'the ports-3l) Iand 37 are now Vin openn communication, therebyi the piston 33 of Vthe servomotor 67 will be lifted so that the surge-preventing valve'plate 3 will be raised tothe position where the resistance Vvalue ofthe valvereaches the value necessary for/preventing'surging because :the'nstem 9 of the surge-preventingvalve plate-3 ,issecured to the piston v3:3. .Onthe other hand, the ,leverj68jofther return mechanism is held on the fulcrum 34, and one end 36 of the return mechanism is secured to the piston 33 of the servomotor 67, and the other end 35 to the cylinder of the pilot valve 66, so that with the lift of the servomotor piston 33 the cylinder of the pilot valve 66 will be lowered, the pilot valve 66 and the piston 28 resume their initial positions.

From the foregoing description, taken in connection with the accompanying drawings, it is thought that the novel details of construction, the manner of use, and the advantages of the invention, will be apparent to those skilled in the art to which it relates.

It is, of course, to be understood that the details of structure and arrangement of parts may be variously changed and modified without departing from the spirit and scope of our invention as set forth in the appended claims.

Having thus described the invention, what we claim as new and desire to secure by Letters Patent, are:

1. In a blower system for controlling the supply of compressed fluid to a load, a blower for supplying said Huid under pressure to said load, an inlet channel cornmunicating with the inlet of said blower, a discharge channel communicating with the discharge of said blower and with said load, a manually operated capacity-control valve positioned in said discharge channel adjacent said load on the inlet side thereof, a surge prevening valve positioned in 'said discharge channel adjacent said blower and servo-mechanism for controlling the movement of said surge preventing valve, said servo-mechanism including an inlet conduit communicating with said blower inlet channel, control means communicating with said inlet conduit and responsive to the inlet pressure of said blower, said control means being operatively connected to a servo-valve for controlling the operation thereof, a servo-motor communicating with said servo-valve and connected to said surge valve, said servo-motor being responsive to movement of said servo-valve to control the movement of said surge valve, and a follow-up mechanism responsive to movement of said servo-motor and operatively connected to said servo-valve for restoring said servo-valve to the original position thereof, thereby 'positioning said surge preventing valve within predetermined limits.

2. In a blower system as set forth in claim 1, said servo-valve including a pivotallyv mounted inlet pipe that introduces control duid therein, means connected to said control means and said inlet pipe and responsive to the inlet pressure of said blower for pivotally moving said inlet pipe, and control pipes communicating with opposite sides of the servo-motor piston, said inlet pipe pivoting into communication wth either of said control pipes in response to operation of said pivoting means.

3. In a blower system as set forth in claim 1, said control means including a iluid responsive ring balance, a cam connected to said ring balance and to said servovalve, said cam being responsive to movement of said ring balance to control the movement of said servo-valve.

`4. In a blower system as set forth in claim il, said control means including a diaphragm motor responsive to the inlet pressure of said blower, an electrical motor responsive to movement of said diaphragm motor and a magnetic coil having a core operatively connected to `said control valve, said magnetic coil being responsive to rotation of said motor to control the movement of said coil and said control valve.

References Cited in the le of this patent UNITED STATES PATENTS

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