US3772883A - Multi-cylinder external combustion power producing system - Google Patents

Abstract

In an external combustion power producing system, a condensable fluid is heated to a vapor state and such heated vapor is separated into at least two portions without changing the state thereof as regards temperature, pressure, entropy, enthalpy, or its specific volume. One portion is expanded isentropically to a lower pressure in non-compression, expansion-only cylinder and is removed entirely from such cylinder and passed to a condenser. The other portion is expanded isentropically in a companion series of expansion and compression cylinders to which, in liquid form, the weight equivalent of the condensed portion of the fluid is introduced so as to be added to the other portion of the fluid. In such cylinders, the mixture is compressed isentropically to the maximum working pressure. Thereafter, the compressed fluid is reheated and reexpanded in accordance with the foregoing to complete the power producing cycle.

Description

United States Patet 1191 Davoud et al.

[ Nov. 20, 1973 MULTI-CYLINDER EXTERNAL COMBUSTION POWER PRODUCING SYSTEM [75] inventors: John Gordon Davoud; Jerry A.

Burke, Jr., both of Richmond, Va.

[73] Assignee: D-Cycle Associates, Richmond, Va.

[22] Filed: June 13, 1972 [21] Appl. No.: 262,175

Related US. Application Data [63] Continuation-impart of Ser. No. 58,099, July 24, 1970, abandoned.

52 us. Cl. 60/94, 60 36 51 Int. Cl. F0lk 25/00, FOlk 23/00 58 Field ofSearch 60/94, 36, 39, 40, 60/64, 65, 93

[56] References Cited UNITED STATES PATENTS 3,557,554 1/1971 Martinek 61 al. 60/94 3,675,416 7/1972 Maeda 60/94 3,716,990 2/1973 Davoud... 60 36 x igo Primary Examiner-Martin P. Schwadron Assistant Examiner-Allen M. Ostrager Attorney-Harold L. Stowell et al.

[5 7 ABSTRACT In an external combustion power producing system, a condensable fluid is heated to a vapor state and such heated vapor is separated into at least two portions without changing the state thereof as regards temperature, pressure, entropy, enthalpy, or its specific volume. One portion is expanded isentropically to a lower pressure in non-compression, expansion-only cylinder and is removed entirely from such cylinder and passed to a condenser. The other portion is expanded isentropically in a companion series of expansion and compression cylinders to which, in liquid form, the weight equivalent of the condensed portion of the fluid is introduced so as to be added to the other portion of the fluid. In such cylinders, the mixture is compressed isentropically to the maximum working pressure. Thereafter, the compressed fluid is reheated and reexpanded in accordance with the foregoing to complete the power producing cycle.

12 Claims, 2 Drawing Figures IOO ZMUZI IQZOO MULTI-CYLINDER EXTERNAL COMBUSTION POWER PRODUCING SYSTEM CROSS-REFERENCE TO RELATED APPLICA- TIONS This application is a continuation-in-part application of our'earlier filed application Ser. No. 58,099, filed July 24, I970, now abandomed, entitled External Combustion Power Producing System BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention generally appertains to new and novel improvements in power producing cycles, such as the known Rankine cycle, and is particularly directed to new and novel improvements over the basic invention disclosed in the aforementioned application.

2. State of the Prior Art The nature and state of the prior art is exemplified by the disclosure in the aforementioned application wherein an external combustion power producing cycle is disclosed that has greater efficiency and more advantages than any known condensing vapor power producing cycle, such as the Rankine cycle.

The invention in such earlier application may be defined as providing an external combustion power producing cycle comprising: I

1. Heating a condensable fluid to the vapor state;

2. Expanding isentropically the vapor;

3. Separating the expanded fluid into at least two portions without substantially changing the state thereof, such as temperature, pressure, entropy, enthalpy, or specific volume;

4. Allowing one of the portions to continue furthe expansion, thereby doing useful work;

5. Condensing said portion;

6. Adding in liquid form the weight equivalent of the condensed portion of the fluid to the other portion of the fluid;

7. Thereafter or simultaneously compressing isentropically the mixture to the operating pressure;

8. Reheating the compressed working fluid in the vapor state; and

9. Reexpanding thevapor isentropically.

The invention in such earlier application may also be defined as providing an external combustion power producing system comprising:

1. Means for heating a condensable fluid to the vapor state;

2. Means for expanding the vapor isentropically;

3. Means for separating the expanded fluid into at least two portions without substantially changing the state of at least one of the portions;

4. Means for adding liquid to the at least one portion;

5. Means for compressing isentropically the mixture to the operating pressure; and,

6. Means for reheating the compressed vapor.

In such system, as disclosed in the earlier application, the power is produced for example in a single cylinder, either single or double acting. The means for separating the expanded fluid into at least two portions, in such system, may comprise a valved passage connecting opposite faces of the piston working in the bore of the cylinder or may comprise valved passage means connecting opposite ends of the cylinder, either alone or with an auxiliary piston-cylinder unit.

SUMMARY OF THE INVENTION Thus, in an embodiment of such earlier application, mechanical means are described to carry out in a piston-cylinder unit, either single or double acting, the following functions:

1. Separation of expanded steam in the cylinder into two precisely determined portions, without in the course of such separation altering the state of either portion;

2. Continued expansion of one portion to some lower pressure; and

3. Compressing the other portion plus the condensed one portion to operating pressure.

The primary object of the present invention is to provide an improved cycle and system for effecting such functions, wherein a multi-cylinder engine is provided in which one, or more, cylinders function for expansion only, while one or more cylinders are used for expansion and compression. The expansion cylinders can, but need not necessarily, operate over a larger pressure range than the expansion-compression cylinders.

TI-Ie invention of this application may be defined as providing an external combustion power producing cycle comprising:

1. Heating a condensable fluid to the vapor state;

2. Separating the heated vapor into at least two portions without changing the state thereof;

3. Allowing one portion to expand isentropically to a lower pressure in a first zone;

4. Condensing the said portion of expanded vapor;

5. Allowing the other portion to expand isentropically in a second zone;

6. Adding in liquid form the weight equivalent of the condensed first portion to the other portion in said second zone;

7. Compressing isentropically the mixture to the operating pressure in the second zone;

8. Reheating the compressed fluid; and

9. Reexpanding the heated, compressed fluid in the manner stated above.

The invention of this application may be further defined as providing an external combustion power producing system comprising:

1. Means for heating a condensable fluid to the vapor state; I

2. Means for separating the heated vapor into at least two portions without changing the state thereof;

3. A first piston-cylinder means for expanding one portion isentropically;

4. Condenser means to which such is passed;

5. A second piston-cylinder means wherein the other portion is expanded isentropically;

6. Means for adding in liquid form the weight equivaexpanded portion lent of the condensed first portion in said second pission only to the lowest desired pressure of one portion of vapor from a superheater, wherein water is heated to a vapor state, while a plurality of companion comexpanslon BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a schematic diagram illustrating the multicylinder system of the present invention.

FIG. 2 is a diagram of pressure of the working fluid plotted as Y axis against the enthalpy along the X axis of a cycle functionable in accordance with the teachings of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now more particularly to the accompanying drawing, themulti-cylinder engine system 10 includes an expansion-onlycylinder 12 having abore 14 in which apiston 16 works, with such piston being shown in its top dead center position in the bore. Therod 18 of such piston is connected in the usual way to a crankshaft (not shown). Such cylinder and piston constitute a first piston-cylinder means for expanding one portion of a heated vapor isentropically to a lower pressure and such means could be composed of several or a number of such cylinder and piston units.

Themulti-cylinder engine system 10 further includes a plurality of companion compression-expansion cylinders 20, 22 and 24 which haveidentical bores 26, 28, and 30, in whichpistons 32, 34, and 36 are workingly disposed. The pistons haverods 38, 40 and 42 that are connected in the usual way to the crankshaft (not shown). Thepiston 36 is shown in the bottom dead center postion while thepistons 32 and 34 are shown at one-half of their power and return strokes. Such cylinders and pistons constitute a second piston-cylinder means that could be made up of a single cylinder and piston or composed of more than the three units shown in the drawing.

Thecylinders 12, 20, 22, and 24 are shown as being of the crosshead type but cylinders without crossheads can be used.

Thecylinders 20, 22, and 24 are provided withinlets 44, 46, and 48 from avapor supply line 50 that extends from asuperheater 52 with such line terminating in an inlet 54 for thecylinder 12.Inlet valves 56, 58, 60, and 62 control the inlet lines, as shown in FIG. 1.

The expansion-onlycylinder 12 has anoutlet 64 leading to acondenser 66 with anoutlet value 68 controlling the flow through the outlet.

Supply lines 70, 72 and 74 for water from amain line 76 from the condenser are connected to the compression-expansion cylinders 20, 22 and 24 and are controlled byinlet valves 78, 80, and 82.

Outlet lines 84, 86, and 88 extend from thecylinders 20, 22, and 24 and are connected to areturn line 90 for thesuperheater 52 withcontrol valves 92, 94, and 96 being provided in such outlet lines to control the flow therethrough.

It will be noted that thebore 14 of the expansion-only cylinder is larger than theidentical bores 26, 28, and

s s w can ship between the bore and stroke of piston-cylinder unit 12 in respect to the bores and strokes ofpistoncylinder units 20, 22 and 24 may be variously modified to suit the particular operation range of the engine. Also, in the form shown, the timing of the opening and closing of theinlet valves 56, 58, 60 and 62 are arranged to allow a greater expansion ratio in the expansion-onlycylinder 12 than in thecompressionexpansion cylinders 20, 22, and 24; however, again this may be varied to suit the particular operating range of the engine. Steam in thecylinder 12 thus can expand to a lower pressure than in thecylinders 20, 22, and 24. Thus, in operation,cylinder 12 is used for expansion to the lowest desired pressure range. This is done to minimize the work of compression. However, the pressure range of the cylinder maybe the same, or the greater range may be provided forcylinders 20, 22, and 24.

At the end of expansion, all steam is removed from the expansion-onlycylinder 12 and passed through theline 64 to thecondenser 66 wherein it is condensed. All steam remains in the compression-expansion cylinders 20, 22, and 24 and the condensate from the condenser or its weight equivalent from some other source is injected into them, through thelines 70, 72, and 74 in three equal proportions before and/or during compression of the working fluid back to the maximum operating pressure. In each ofthe'lines 70, 72, and 74 a variablevolume injection pump 100, 102, and 103 is provided. Thepumps 100, 102, and 103 provide the means for injection of the proper volume of fluid into each cylinder and such pumps may be of the adjustable wobble plate type and driven from the engine crank or by auxiliary power.

Variable delivery piston pumps, one per cylinder, similar to commonly used diesel injection pumps, or one such pump supplying a plurality of cylinders, by the method known in the art as the common rail system, may also be used,

Compressed steam from thecylinders 20, 22, and 24 is then passed through thelines 84, 86, and88 to the superheater for the start of a new cycle.

The proporations of steam condensed, to steam compressed, and the relative pressure ranges over which the expansion-onlycylinder 12 and thecompressionexpansion cylinders 20, 22, and 24 operate is determined on the basis of the state-points required to give the desired engine performance by suitable adjustment of cut-off ratios and cylinder bore. In this regard, it is desirable from the practical point of view to maintain a constant stroke, and thus, a constant crank size, in all of the cylinders.

So that any desired portion of steam can be removed and condensed, and any desired expansion ratios can be achieved, each of thevalves 56, 58, 60 and 62, and 68, 92, 94, and 96 is provided with an actuator driven by the engine crankshaft through an adjuatable cam (not shown).

A numerical example is given below with the statepoints being as shown on the pressure-enthalpy diagram of FIG. 2 of the drawing. The dotted lines reflect a departure from isentropic expansion (D, E and compression (3C as well as a fall in pressure of psia through the superheater (C D With reference to FIGS. 1 and 2, the multi-cylinder system operates as follows:

For 1 lb. of steam from thesuperheater 52ln cylinder 12 Expand 0.37 lbs. from D, to F (950 psia and 1,000F to 13 psia and 205.9F). Remove all steam from thecylinder 12 throughline 64 and condense it at 13 psia in thecondenser 66.

Incylinders 20, 22, and 24 Expand 0.63 lbs. (0.21 lbs. in each cylinder) from D, to (950 psia and 1,000F. to 40 psia). This steam remains in thecylinders 20, 22 and 24 at the end of expansion.

Inject condensate (0.37 lbs.) throughline 76 andlines 70, 72, and 74 from condenser 66 (from cylinder 12) in equal portions 0.37/3 0.123 lbs. into each ofcylinders 20, 22, and 24 and compress wet steam 0.333 lbs. per cylinder of quality as shown at point J from 40 to 1,000 psia, (from J to C,).

At the end of compression, all steam fromcylinders 20, 22, and 24 (1 lb.) is passed throughlines 84, 86 and 88 to returnline 90 for thesuperheater 52, and heated from C, (1,000 psia and 544.6F) to D, (950 psia and 1,000F).

One pound of steam is passed from thesuperheater 52 to thecylinders 12, 20, 22 and 24 in the ratios defined above, i.e.,

Cylinder 12Cylinders 20, 22, and 24 Cycle repeats 0.37 lbs. 0.63 lbs.

Thermodynamic efficiency of the cycle is given by:

Work out Work of Compression/Heat in Expansion ratio is 10.952/0.8753 12.5:1

Steam in thecylinder 12 will have at the end of the expansion a volume of 0.37 X 28.6 10.58 c.f.

Expansion ratio will be 28.6/0.8753 32.6:1 For a given stroke, S If r radius ofcylinders 20, 22, and 24 R radius ofcylinder 12 It will be obvious to those skilled in the art that thissystem 10 lends itself readily to theprinciple of double action, i.e., admission of high pressure steam alternately to either end of the cylinder. In the case of the expansion-onlycylinder 12, this would with advantage take the form taught by the well-known Uniflow principle. Uniflow is a commonly used type of reciprocating engine, as disclosed in Barnard, Ellenwood and l-lirshfeld, Heat Power Engineering, Third Edition, Part 1, Pg. 388, Wiley & Sons, 1926 and Encyclopedia Britannica, 1952, Vol. 21, page 359. As these references show, the Uniflow principle involves a separation of the inlet and outlet ports or valves to minimize condensation. It can be used in either single or double acting cylinders.

Thecylinders 20, 22, and 24 could with advantage employ inlet andoutlet valves 58, 60, 62, and 92, 94, 96 in FIG. 1 at both ends of the cylinders, and a single inlet valve for the injection of water from thecondenser 66 during each compression stroke.

As thecylinder 12 is used only for expansion, it can be similar to a single or double acting Uniflow cylinder which is common in the art. As it is uncomplicated by the need for the injection of water or removal of only a part of the steam,such cylinder 12 can be compounded if the expansion ratio is sufficiently large to indicate problems with the inlet valve mechanism.

In the example shown above, for instance,cylinder 12 was found to have an expansion ratio of 32.6:1. Expansion ratios of this order can with advantage be carried out in a compound engine. Any of the methods of compounding-in common use could be employed.

Thus, it is recognized that various modifications may be made in the system and the functioning cycle, as disclosed herein, and it is to be understood that the illustrated example and description are merely exemplary in nature with the invention being defined by the spirit and scope of the appended claims.

What is claimed is:

1. An external combustion power producing cycle comprising:

a. heating a condensable fluid to the vapor state;

b. separating the heated vapor into at least two portions without substantially changing the state thereof;

c. expanding isentropically one portion of the vapor in a first zone; I

d. condensing such one portion of expanded fluid;

e. expanding isentropically the other portion of the vapor in a second zone;

f. adding in liquid form the weight equivalent of the condensed first portion of the fluid to the other portion of the fluid in said second zone;

g. compressing isentropically the mixture to the operating pressure in said second zone;

h. reheating the compressed fluid to the vapor state;

and

i. reexpanding the vapor in at least two portions as described in b, c and e above.

2. The invention defined in claim 1 wherein the portion of fluid which is condensed is, prior to condensation, expanded in an expansion cylinder means and removed entirely from such cylinder means and passed to a condenser.

3. The invention defined in claim 1 wherein the other portion of fluid is expanded in a cylinder means and, after addition of the liquid derived from condensation of the first portion, is compressed in the same cylinder means, in which it is expanded, to the maximum pressure.

4. An external combustion power producing cycle comprising:

a. heating a condensable fluid to the vapor state in a superheater;

b. removing the heating vapor from the superheater and separating it into at least two portions without substantially changing the state thereof;

c. introducing one portion into an expansion cylinder means wherein it is expanded isentropically;

d. passing said portion of expanded fluid to a condenser wherein it is condensed to liquid form;

e. introducing the other portion of the heated vapor into a compression-expansion cylinder means wherein it is expanded isentropically;

f. adding a liquid ofa weight equivalent to that in the condenser to the compression-expansion cylinder means;

g. compressing in the compression-expansion cylinder means the mixture isentropically to the operating pressure; and

h. passing the compressed fluid back to the superheater for the initiation of another cycle.

5. The invention of claim 4 wherein all of the expanded fluid is removed from the expansion cylinder means and condensed.

6. The invention of claim 4 wherein the liquid added to the compression-expansion cylinder means is the liquid condensate in the condenser.

7. The invention of claim 4 wherein the condensate from the condenser is injected into the compressionexpansion cylinder means before and/or during the compression step 3).

8. An external combustion power producing system comprising:

a. means for heating a condensable fluid to the vapor state;

b. means for separating the heated vapor into at least two portions without substantially changing the state thereof;

c. a first piston-cylinder means for expanding one portion isentropically to a lower pressure;

d. condenser means to which such expanded portion is passed;

e. a second piston-cylinder means wherein the other portion is expanded isentropically to a lower and different pressure from the lower pressure attained by the expansion of the first portion;

f. means for adding in liquid form from the condenser to the second piston-cylinder means the weight equivalent of the condensed first portion;

g. said second piston-cylinder means compressing the mixture to the operating pressure; and

h. means for passing the compressed fluid from the second piston-cylinder means to the heating means a for reheating in initiating a further power producing cycle.

9. The invention of claim 8 wherein said first pistoncylinder means includes at least one single acting cylinder of the Uniflow type.

10. The invention of claim 8 wherein said first pistoncylinder means includes at least one double acting cylinder of the Uniflow type.

11. The invention of claim 8 wherein said first pistoncylinder means includes two or more cylinders of the compound type.

12. The invention of claim 8 wherein said second piston-cylinder means includes at least one single acting cylinder.

Claims (12)

1. An external combustion power producing cycle comprising: a. heating a condensable fluid to the vapor state; b. separating the heated vapor into at least two portions without substantially changing the state thereof; c. expanding isentropically one portion of the vapor in a first zone; d. condensing such one portion of expanded fluid; e. expanding isentropically the other portion of the vapor in a second zone; f. adding in liquid form the weight equivalent of the condensed first portion of the fluid to the other portion of the fluid in said second zone; g. compressing isentropically the mixture to the operating pressure in said second zone; h. reheating the compressed fluid to the vapor state; and i. reexpanding the vapor in at least two portions as described in b, c and e above.

2. The invention defined in claim 1 wherein the portion of fluid which is condensed is, prior to cOndensation, expanded in an expansion cylinder means and removed entirely from such cylinder means and passed to a condenser.

3. The invention defined in claim 1 wherein the other portion of fluid is expanded in a cylinder means and, after addition of the liquid derived from condensation of the first portion, is compressed in the same cylinder means, in which it is expanded, to the maximum pressure.

4. An external combustion power producing cycle comprising: a. heating a condensable fluid to the vapor state in a superheater; b. removing the heating vapor from the superheater and separating it into at least two portions without substantially changing the state thereof; c. introducing one portion into an expansion cylinder means wherein it is expanded isentropically; d. passing said portion of expanded fluid to a condenser wherein it is condensed to liquid form; e. introducing the other portion of the heated vapor into a compression-expansion cylinder means wherein it is expanded isentropically; f. adding a liquid of a weight equivalent to that in the condenser to the compression-expansion cylinder means; g. compressing in the compression-expansion cylinder means the mixture isentropically to the operating pressure; and h. passing the compressed fluid back to the superheater for the initiation of another cycle.

5. The invention of claim 4 wherein all of the expanded fluid is removed from the expansion cylinder means and condensed.

6. The invention of claim 4 wherein the liquid added to the compression-expansion cylinder means is the liquid condensate in the condenser.

7. The invention of claim 4 wherein the condensate from the condenser is injected into the compression-expansion cylinder means before and/or during the compression step g).

8. An external combustion power producing system comprising: a. means for heating a condensable fluid to the vapor state; b. means for separating the heated vapor into at least two portions without substantially changing the state thereof; c. a first piston-cylinder means for expanding one portion isentropically to a lower pressure; d. condenser means to which such expanded portion is passed; e. a second piston-cylinder means wherein the other portion is expanded isentropically to a lower and different pressure from the lower pressure attained by the expansion of the first portion; f. means for adding in liquid form from the condenser to the second piston-cylinder means the weight equivalent of the condensed first portion; g. said second piston-cylinder means compressing the mixture to the operating pressure; and h. means for passing the compressed fluid from the second piston-cylinder means to the heating means a for reheating in initiating a further power producing cycle.

9. The invention of claim 8 wherein said first piston-cylinder means includes at least one single acting cylinder of the Uniflow type.

10. The invention of claim 8 wherein said first piston-cylinder means includes at least one double acting cylinder of the Uniflow type.

11. The invention of claim 8 wherein said first piston-cylinder means includes two or more cylinders of the compound type.

12. The invention of claim 8 wherein said second piston-cylinder means includes at least one single acting cylinder.

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