US2033843A - Ejector apparatus - Google Patents

Description

March 10, 1936. J. w. McNULTY EJECTOR APPARATUS Filed NOV. 16, 1933 FIGnf.

sTEnm PRESSURE, 1.35. A85.

WITNESS ES: W W W 24 7 7 4 i atented Mar. 10, 1936 EJECTOR APPARATUS John W. McNulty, Ridley Park, Pa., assignor to Westinghouse Electric & Manufacturing Company, East Pittsburgh, Pa., a corporationv of Pennsylvania Application November 16, 1933, Serial No. 698,348

- 4 Claims.

My invention relates to ejectors and it has for an object to improve the performance thereof so as to minimize the consumptiorrof motive fluid, for example; steam.

Where ejector apparatus is used for vacuum producing purposes, for example, with steam jet cooling or refrigeration, economy insteam consumption may be secured by careful attention to the steam flow requirements and by designing the nozzles for maximum efiiciency for specific steam conditions and condenser vacuum. Greater steam flow is required to start an ejector than to maintain it in operation. Accordingly, there-, fore, if greater steam nozzle capacity is provided to secure greater flow for starting and less steam nozzle capacity with less flow is provided to maintain the'ejector in operation, more economical performance may be secured. Since flow is a function of the pressure wof steam supply, an 20 ejector may be maintained in operation, with improved economy because of the low pressure of the supply, by steam supplied at such a pressure to nozzles of such a design that it is not selfstarting. To secure the economical advantage of 25 providing only the necessary flow to maintain the ejector in operation, I provide a set of running nozzles having such design and giving such flow as will. maintain operation. However, as the running nozzles, for the pressure supplied, 30 are not self-starting, I provide an additional or starting set of nozzles which are effective, with the running nozzles, to start the ejector, the starting nozzles being stopped after stable operatic-n of the ejector is secured. It is to be understood,,of course, that the set of running nozzles would be self-starting if the pressure of steamsupplied were increased to a suiiicient point, but

better performance is to be had by maintaining the steam pressure at a value consistent with 40 safely maintaining the ejector in operation, after it is started. For example, a nozzle may have such a design, that, if steam were supplied to it at a pressure of 125 pounds per square inch or above, it would be self-starting; and, after being 5 started, it wouldbe maintained in operation until the pressure supply declined to the break point, for example, 100 pounds per square inch.

Economy of consumption may, therefore, be secured by supplying steam to a nozzle at a pres- 50 sure slightly above, the break point, for instance, in the example assumed, at a pressure around 105 pounds per square inch.

Therefore, a more particular object of my invention is to provide an ejector having two sets 55 of nozzles, the two sets being used for starting and one set being stopped after the ejector is started to economize in the consumption of steam.

These and other objects are eifected by my co invention, as will be apparent from the following description and claims taken in accordance with the accompanying drawing, forming a part of this application, in which:

Fig. 1 is a side elevation of an ejector embodying my invention; and i r 5 Fig. 2 is a diagram illustrating an operating principle involved in my invention.

Referring now to. the drawing more in detail, in Fig. 1, I show an ejector, at It), for translating medium from a suitable source, for example, from the tank or evaporator, at I I, the translated medium being compressed and discharged against a suitable back pressure, for example, to that existing in the condenser, shown at l2. The ejector, at H), is of conventional con- 10 struction, the suction end being connected to the evaporator or tank, at H, andthe discharge end communicating with the interior of the condenser, at l2. My invention consists in the modified arrangementfor supplying steam and for controlling motivation of jets so as to secure most economical operation,

The rate of steam consumption during the startingperiod is higher than that required to maintain the ejector in operation afterbeing started. Therefore, I provide two sets of jets' or nozzles, a set of running jets or nozzles l4 and a set of starting jets or nozzles l5, both sets 'being effective when the ejector is to be started and the starting set l5 being cut out after the ejector is started and is in normal operation. The reason why two sets of nozzles are employed to satisfy the above conditions is that the motive steam for the jets is supplied at such a pressure that most economical operation can be secured, the pressure being such that, for the design and capacity of running nozzles required for normal operation, the flow of the latter nozzles is insuiiicient to effect starting and it is, therefore, necessary to increase the flow atsuch time by starting nozzles.

If the characteristics of an ordinary jet are considered, it will be found that a considerable range exists between what might be termed the self-starting point and the break point. For 4 example, it might be assumed that the nozzle set 14 would have sufiicient flowto start the ejector if steam were supplied thereto at 125 lbs. per square inch and that, after starting, the ejector -would be maintained in operation by the nozzle set 14 until the pressure dropped to 100 lbs. per

' sq. in. This will be clear from a consideration of Fig. 2, wherein the line A represents the break limit for a nozzle, that is, if the pressure of motive steam supplied to the nozzle falls be- 5 low the line A for any condition, then the nozzle will cease to operate. The line B represents the limit below which the nozzle is not self-starting and above which it is self-starting, and may; therefore, be termed the curve or line of starting pressures. A substantial margin, therefore, occurs between the lines A and B where a nozzle is not self-starting but where it is able to maintain operation after being started. From the point of view of economy of steam consumption, the ejector apparatus is operated to the best advantage, if steam is supplied thereto within the margin between the lines A and B and slightly above A. In accordance with my invention, steam is supplied to the nozzles at a pressure somewhat above the break point, the steam consumption being more and more economical as the break point is approached; and to compensate for the inability of the nozzles or jets H to be self-starting, the additional nozzles or jets i5 are employed, the nozzles or jets i5 serving to assist the nozzles it during the starting period and being rendered inactive after the ejector is started and is in normal operation. To this end, I show a steam line I having a pressure control valve I! for controlling the pressure of steam supplied to the header l8 and from the latter through the passages IQ and 20 to the running and starting jets, the passages l9 and 20 having valves 2| and 22 arranged therein.

To initiate operation of the ejector l0, both valves 2| and 22 are opened, supplying steam to both the starting and running sets of nozzles. The steam jets from the two sets of nozzles establish stable ejecting action of the ejector within a relatively short time. When said ejecting action has been established, or become stable, I close the valve 22 to shut off the supply of steam to the starting nozzles I5. Admission of steam to the running nozzles H is continued to efiect normal operation of the ejector III, which is accomplished with a more economical consumption of steam than is possible in starting the ejector. To terminate operation of the ejector l0, it is only necessary, of course, to close the valve 2i.

The time of closing the valve 22 may be determined either by the elapsing of a predetermined period of time, chosen to be ample to insure stable operation of the ejector, or by determining that the ejecting has been established or made stable. The operation of the valves controlling the admission of steam to the starting and the running nozzles, in accordance with my invention, may be accomplished either manually or automatically by the control mechanisms described and claimed in the application of J. W. McNulty and M. A. Nelson, Serial No. 694,513, and the application of D. W. R. Morgan and J. W. McNulty, Serial No. 694,512, both assigned to the assignee of the present invention.

While I have referred to running and starting jets, which is the running jet and which is the starting jet may depend upon condenser temperature and pressure conditions and the relative capacities of the jets. Assuming that the capacity and steam consumption of the running jets is somewhat larger than that of the starting jets, with a sufficient reduction in condenser temperature and pressure, as may be occasioned by reduced temperature of circulating water, it

may be more economical to use the starting jets as the running jets, both sets of jets, as before, being used to initiate operation of the ejector. Then again, under other circumstances, for example, with increase in steam pressure to a sumcient extent or with decrease in condenser absolute pressure to a suflicient point, one set of nozzles may be adequate both for starting and running; however, as already pointed out, it is advantageous to reduce the steam flow, as by stopping the starting nozzles, after the ejector is in stable operation. Also, where I refer to nozzles or set of nozzles, either starting or running, it is to be understood that one or more nozzles is intended, the number being a matter of design.

While I have shown my invention in but one form, it will be obvious to those skilled in the art that it is not so limited, but is susceptible of various other changes and modifications without departing from the spirit thereof, and I desire, therefore, that only such limitations shall be placed thereupon as are imposed by the prior art or as are specifically set forth in the appended claims.

What I claimis:

1. The method of operating vacuum-producing apparatus including an ejector having starting and running nozzles, which comprises admitting motive fluid at normal pressure to both starting and running nomles to establish the ejecting action of the ejector when, initiating operation thereof, discontinuing the admission of motive fluid to the starting nozzles at a time when said ejecting action is established, and continuing to admit motive fluid at normal pressure only to the running nozzles for normal operation of the ejector, said normal pressure being sufficient to enable the running nozzles to maintain ejecting action when established but insuflicient to enable the same to start ejecting action.

2. The method 01' operating vacuum-producing apparatus including an ejector having starting and running nozzles, which comprises admitting motive fluid at normal pressure to both starting and running nozzles to establish the ejecting action of the ejector when initiating operation thereof, discontinuing the admission of motive fluid to the starting nozzles at the end of a predetermined period of time during which said ejecting action is established, and continuing to admit motive fluid at normal pressure only to the running nozzles for normal operation of the ejector, said normal pressure being suiflcient to enable the running nozzles to maintain ejecting action when established but insufficlent to enable the same to start ejecting action.

3. The method of operating an ejector having a first and a second set of nozzles which comprises admitting normal steam pressure to both sets of nozzles to start ejecting action; and shutting off the admission of steam to one set of nozzles, after ejecting action is established, and continuing the admission of normal steam pressure to the other set of nozzles for normal operation, said normal steam pressure being suflicient to enable said other set of nozzles to maintain ejecting action when established but insufficient to enable the same to start ejecting action.

4. The method of operating an ejector for translating fluid from one region to a region of higher absolute pressure which comprises providing greater than normal admission oi motive fluid to the ejector when starting operation thereof, and continuing admission of motive fluid to the ejector, for normal operation thereof after ejecting action is established, at a rate which is suflicient to maintain ejecting action after it is established but insuflicient to start ejecting action thereof.

JOHN W. MCNULTY.

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