US1415406A

US1415406A - Elastic-fluid-operated ejector

Info

Publication number: US1415406A
Application number: US172145A
Authority: US
Inventors: Scanes Arthur Edwin Leigh
Original assignee: British Westinghouse Electric and Manufacturing Co Ltd
Current assignee: Metropolitan Vickers Electrical Co Ltd
Priority date: 1917-06-01
Filing date: 1917-06-01
Publication date: 1922-05-09
Anticipated expiration: 1939-05-09

Description

A. E. L. SCANES.

ELASTIC FLUID OPERATED EJECTOR- APPLICATION FILED JUNE x, 1917.

1,415,406. Patented May 9,1922.

FIGZ.

INVENTOR WITNESSES om'reo s rerenr THE BRITISH WESTINGIETOUSE ELECTRIC ITED, A. COMPANY OF GREAT BRITAIN.

AND MANUFACTURING COMPANY LIM- EmsrIc-rLum-oPEnATnD mncron.

Application filed June 1,

T 0 all whom it may concern: I

Be it known that I, ARTHUR EDWIN LEIGH SoANns, a subject of the King of Great Britain, and a resident of Ashton-on-Mersey, in the county of Chester, England, have invented a new and useful Improvement in or Relating to Elastic-Fluid-Operated Ejectors, of which the following is a specification.

This invention relates to elastic fluid ated ejectors, steam ejectors for example and, although not limited. in this respect, is especially applicable to steam ejectors'used for exhausting air and non-condensible vapoursfrom a steam condenser.

It has been 'found that with an ejector consisting of an expanding nozzle and suitable combining cones and difl'users in which the expanding nozzle is so proportioned as to give for the pressure at which it is desired normally to operate the correct ratio of expansion to the elastic operating fluid, and particularly if the ratio of compression of the ejector is very high, the operation of the ejector is very sluggish when starting. This is due to the fact that before the-pressure is reduced in the body of the ejector, there is a tendency for the operating fluid to be expanded in the nozzle to a pressure below that obtaining in the body of'the ejector with consequentloss by shock and eddies. For example, in the case of a steam ejector used for maintaining a. high vacuum'in-a steam condenser, if the steam nozzle is designed for a vacuum of 29" Hg. with-30 barometer, when starting there will be atmospheric pressure in the ejector body and the condenser, and it has been found necessary to facilitate easy starting, to reduce the ratio of expansion in the nozzle below 29 Hg, with consequent loss' of efiiciency in the nozzle at the pressures The present invention has for its object to provide animproved elastic fluid operated ejector in which the objections above mentioned areovercome. This is accomplished, accordin to this invention, by providing means which will reduce or check the expansion of the operating fluid passing through a portion or portions of the nozzle of the ejector during the starting period, but will allow the operating fluid to expand to the full extent for which the nozzle is designed during normal operation of the ejector, that is to say when the pressures cor- Speciflcation'of Letters Patent.

operobtaining under normal operating conditions;

Patented May 9', 1922.

1917. Serial No. 172,145.

responding to the normal ratio of compression of the approximately so. I

In carrying-out the invention the expansion of the operating fluid passin through the expanding nozzle or nozzles. o the ejector i's reduced or checked byadmitting additional elastic fluid to said nozzle or noz-' zles atone or more intermediate points along its nor their length, the pressure of the ad ditional fluid so admitted being approximately equal to or greater than that to which the operating fluid normally expands at the point or points in the nozzle or nozzles at which said additional fluid is admitted. Preferably the pressure of the elastic fluid admitted to the expanding nozzle or nozzles is varied automatlcally in accordance with the pressure obtaining at a predetermined point or points in the converging or diverging portion of the mixing cone of the ejector. The fluid admitted to the expanding nozzle or nozzles may conveniently though not necessarily be derived cone or difiuser of the-ejector itself.

'In the drawings accompanying this app-licationv Figures 1 to 4, inclusive, are views diagrammatically illustrating various ex amples of ejecting-devices embodying this invention.

In Figure 1 the ejector comprises as usual a suction chamber 1, a mixing cone 2 and a diffuser 3, the air and non condensable vapours to be exhausted entering the ejector through the port 4. The expansion nozzle of the ejector is divided transversely into two co-axially located. portions 5' and 5 separated from one another by a short distanceas shown. Operating fluid (steam) is supplied tov the nozzle 5 through the pipe 6. The space between the two portions 5*, 5 of the nozzle opens intoa' closed chamber 7 connected by a conduit or passage 8 with the converging portion of the mixing cone 2 of the ejector at a point 10 at which under normal operating conditions v( of vacuum for example) there exists a pressure-approximately equal to the. pressure at the outlet of the first portion 5* of the expanding nozzle. A throttle valve 9 is preferably located in the conduit 8 for a purpose hereinafter explained.

The operation of this form of the invention is as follows At starting, the operatin fluid (steam for example) expands in the rst portion 5* of ejector have been established or from the mixing.

I ing from the nozzle to some pressure p but in the. mixing cone at the point 10 where the connection is made to the closed chamber 7 there will be a higher pressure P. There will consequently be a flow of mixture from the mixing cone 2 through the conduit 8 to the chamber" 7 surrounding the divided nozzle and this mixture will be entrained by the operating fluid leaving the first portion 5 of the nozzle and will be carried into the second portion 5 of the nozzle thereby partially filling up this portion of the nozzle and reducing or checking the expansion of the operating fluid WhllSbPfiSSlIlg therethrough. Thus the first portion 5? of the divided nozzle acts during starting as a small ejector. The combined mixture issuthe second part 5 of the divided nozzle continues to reduce the pressure in the combining cone 2, and the lower the pressure P therein becomes the nearer will it approach the value of the pressure pin the chamber 7 and the less will be the quantity of mixture flowing from the mixing cone 2 through the conduit 8 and the second part 5 of the divided nozzle. Ultimately when the pressure in the suction chamber 1 is reduced to the desired degree the pressure in the cone 2 at the point 10 where connection is made with the chamber 7 will be reduced approximately to the pressure p and no further flow of mixture will take place from the combining cone 2 through the conduit 8 and the second portion 5*. of the divided nozzle. The operating fluid will now be free to expand fully in the second part 5 of the nozzle with maximum efiiciency, the divided nozzles 5 5 then acting to all intents as one unbroken nozzle.

It is sometimes found desirable to connect the closed chamber 7 with the combining cone 2 at a oint at which under normal operating con itions the pressure P in the latter will always be slightly in excess of the pressure p in the divided nozzle, the throttle valve 9 in the conduit 8 enablin this pressure difference to be regulated eit er automatically or by hand to maintain the most advantageous flow of mixture.

For simplicity the ejector has been shown in Figure 1 as having but a single expansion nozzle. It is to be understood, however, that the invention is equally applicable to an ejector having a plurality of nozzles as showndiagrammatically in Figure 2. In this figure all of the nozzles are shown opening into a single closed chamber 7 connected with the combining cone 2 but separate chambers for each of the nozzles may be provided if desired connected to the same or to different points in the ejector.

The-expansion nozzle of the ejector may be divided into more than two parts and the co-operating closed chambers separately connected to the ejector at points of difierent naiaaoe pressure therein as shown diagrammatically ance with the reduction of pressure occurring in the body of the-ejector. An arrangement for automatically controlling the amount of fluid admitted to the closed chamber 7 is shown diagrammatically in Figure 4: in which a valve 12 controls a port 11 leading said valve belng operatively connected as from the atmosphere to the closed chamber with a diaphragm 13 or the like contained in a closed chamber subjected on one side to the pressure of the atmosphere entering through the opening 14 therein and on the other side by means of the interconnecting pipe 15 to the pressure obtaining in the body of the ejector, and that of an adjustable spring 16.

At starting atmospheric pressure will exist on either side of the diaphragm 13 and the spring 16 will maintain the valve 12 in the position shown in Figure 4 in which the closed chamber 7 is open through the port 11 to the atmosphere. As the pressure indiaphragm preponderating will gradually close the valve 12 so that when the ejector is operating under normal conditions the valve 12 will close the port 11, and the flow of air through the second portion 5 of the nozzle will cease.

ll claim as my invention:

1. The method of operating elastic fluid ejectors, which consists in reducing or checking the expansion of the operating fluid passing through the expansion nozzle of the device at-starting by admitting to said nozzle at an intermediate point of its length elastic fluid in addition to the operating fluid at a pressure approximately equal to that to which the operating fluid expands during normal operation of the device at the point in the nozzle. at which such additional fluid is admitted.

2. The method of operating elastic fluid ejectors having a combining or collecting chamber communicating with the device to be evacuated, a diffuser communicating with said chamber, and an elastic fluid expansion nozzle discharging into said chamber, which the body of the ejector falls the pressure on Q the diaphragm 13 will be consists in reducing or checking the expansion of the operating fluid passing-through a portion of said nozzle during the start ing period and in allowing the operating fluid to expand the full extent for which said nozzle is designed during normal operation orwhen the normal ratio of compression ofthe device have been approximately established.

3. In an elastic fluid operated ejector, a combining or collecting chamber adapted to be connected to the device to be evacuated, a diffuser connecting with said chamber, an expansion nozzle for discharging elastic operating fluid into saidcombinmgand collecting chamber, ancfmeans for admitting variable pressure elastic fluid to said expansion nozzle at a point intermediate its ends.

4. In an elastic fluid operated ejector, a combining or collecting chamber adapted to be connected to the device to' be evacuated,

- and for varying the amount a diffuser connecting with said chamber, an expansion nozzle for discharging elastic op-, erating fluid into said combining and collecting chamber, and means for admitting variable pressure .elastic fluid to said expansion nozzle at a point intermediate its ends of elastic fluid so admitted in accordance with the variations in pressures at a point in said combining or collecting chamber.

5. In an elastic fluid operated ejector, a combining or collecting camber adapted to be connected to the device to be evacuated,

a diffuser connecting with said chamber, an

expansion nozzle :for discharging elastic operating fluid into said combining and collecting chamber, and means for admitting variable pressure elastic fluid to said expan-- sion nozzle at a point intermediate its ends and for automatically varying the amount of elastic fluid so admitted 1n accordance with the variations in pressure at a point in said combinmg or collecting chamber.

(3. The method of operating an elastic fluid ejector, which consists in checking the expansion of the operating fluid passing through the expansion nozzle of the ejector at the time of starting by admitting elastic fluid to the nozzle at a point intermediate its-length, and in cutting off the admission of said elastic fluid after substantially normal operating conditions are attained with-' in the ejector.

7 he method of operating an ejector which consists in-checking the expansion of the operating fluid traversing the expansion nozzle of the ejector at the time of starting by causing the partially expanded operat-r mg fluid which has traversed a part of the expansion nozzle to entrain an elastic fluid' which with the operating fluid traverses a subsequent portion of the nozzle. and in cutting off the supply of entrainable fluid after substantially normal operating prespressures corresponding to the to be evacuated,

sureshave been attained within the ejector. 8. In a fluid operated ejector, a diffuser adapted to communicate with a receptacle to be evacuated, an expansion nozzle for expanding and delivering operating fluid into and through said diffuser, andmeans for delivering fluid. at an intermediate point in the traverse of the operating fluid through saidnozzle, 9. In a fluid operated ejector, a diffuser adapted to communicatewith a, receptacle to be evacuated, an expansion nozzle for expanding and delivering operating fluid to the diffuser, and means responsive to pressure variations. within the diffuser for delivering-elastic fluid to traversing said nozzle.

10. 'In a fluid operated ejector, a diffuser adapted to communicate with .a'receptacle to be evacuated, an expansion nozzle for expanding and delivering elastic fluid to said diffuser and means for delivering fluid from said diffuser to an aperture formed intermediate the ends of said nozzle.

. 11,, In an'elastic fluid operated ejector,"a diffuser adapted to communicate with a receptacle to be evacuated, a-nozzle for expanding and delivering operating fluid to said diffuser and having an aperture formed the operating fluid and delivering operating fluid to communication between said chamber and said diffuser.

13. In a fluid operated ejector, a diffuser adapted to communicate with a receptacle :1 sectionally formed nozzle for expanding and delivering operating fluid to said difl'user, separate chambers communicating with apertures between separate sections of said nozzle and with intermediate points within the diffuser.

14. In a fluid operated ejector, a diffuser adapted to communicate with-a receptacle to be evacuated, a nozzle having apertures located at different points along its length, and means for-establishing communication between said apertures and intermediate points within the diffuser.

In testimony whereof I have hereunto subscribed my name this seventh day of May 1917.

ARTHUR EDWIN LEIGH SCANES. lVitnesses FREDERICK NIXON GEORGE EDWARD drums.