US3813882A

US3813882A - Hot-gas engines

Info

Publication number: US3813882A
Application number: US00306558A
Authority: US
Inventors: K Hubschmann
Original assignee: Motoren Werke Mannheim AG
Current assignee: Caterpillar Energy Solutions GmbH
Priority date: 1971-11-16
Filing date: 1972-11-14
Publication date: 1974-06-04
Anticipated expiration: 1991-06-04
Also published as: DE2156773B2; SE374413B; DE2156773C3; DE2156773A1

Abstract

A double-acting hot gas engine includes four or a higher even number of cylinders which comprise pairs whereof the cylinders are phase-displaced through a 180* crank angle. An expansion chamber of each cylinder is connected, by way of a heater, a regenerator and a cooler arranged in series, to a compression chamber of another cylinder. At least for partial load, the compression chambers of each pair are interconnected via an overflow path for a time period extending throughout part of each of successive working cycles of each pair, the time period being increased if the load decreases.

Description

Safies atet 1191 Hubschmann June 4, 1974 HOT-GAS ENGINES 2,611,235 9/1952 Van Weenen 60/24 2,643,507 6/1953 Dros 60/24 [75] Inventor: i Pi g fiuhglschmann 2,664,699 1/1954 Kohler 60/24 angwe1 erman [73] Assignee: Motoren-Werke Mannheim AG Primary ExaminerEdgar W. Geoghegan V0rm- Benz abta o 'fl Assistant ExaminerH. Burks glotmenball, POStfaCh, Mannheim, Attorney, Agent, or Firm-Eric H. Waters ermany [22] Filed: NOV. 14, 1972 [57] ABSTRACT [2]] Appl- NO: 306558 A double-acting hot gas engine includes four or a higher even number of cylinders which comprise pairs 30 Foreign Application priority Data whereof the cylinders are phase-displaced through a 180 crank angle. An expanslon chamber of each cyl- Nov. 16, l97l Germany 2156773 mder 15 connected, by way of a heater, a regenerator and a cooler arranged in series, to a compression (gl. chamber of another cylinden At least for partial load 58 Field 615651611IIIIIIIIIIIIIIIIIIIIIIIIIIIIII'6o/24, 525 P Chambers Of each. pair imam nected via an overflow path for a time period extend 1561 ilsstarzsi rgar ihf2:2 322225 551; 1122213611 UNITED STATES PATENTS the load decreases 2.480.525 8/l949 Van Weenen 60/24 2,486,081 10/1949 Van Weenen 60/24 8 Claims, 4 Drawing Figures PATENTEBJUH 4 IBM f 3313-1 sum 1 0F 3 j V 5 A. 10

HOT-GAS ENGINES BACKGROUND OF THE INVENTION l. Field of the Invention The invention relates to a method of obtaining loadresponsive regulation of the power of a double-acting hot-gas engine comprising four or a higher even number of cylinders, in which each cylinder contains an expansion chamber and a compression chamber separated by a working piston. For the purpose of achieving the Stirling cycle, each expansion chamber is connected to a compression chamber of another, phasedisplaced cylinder by way of a flowpath which contains a heater, a regenerator and a cooler arranged in series.

2. Description of the Prior Art A hot-gas engine of the above kind is illustrated in FIG. a on page 287 of Motortechnische Zeitschrift, No. 7, Vol. 29 I968) and is briefly described in the associated text. On pages 290 and 291 of the same issue of this journal there are given seven variables, changes in which enable the power of a hot-gas engine to be regulated, but no details are given as to how such regulation can be achieved in a double-acting hot-gas engine. One of these variables is the ratio of maximum pressure to minimum pressure in the Stirling cycle.

SUMMARY OF THE INVENTION An object of the present invention is to provide a method of regulation which results in a change of the aforementioned ratio.

According to one aspect of the invention, there is provided a method of obtaining load-responsive regulation of the power of a double-acting hot-gas engine which comprises four or a higher even number of cylinders each of which contains an expansion chamber and a compression chamber separated by a working piston and which comprise pairs of cylinders whereof the cylinders of each pair are phase-displaced with respect to each other through a 180 crank angle, the expansion chamber of each cylinder being connected, by way of a flow path containing a heater, a regenerator and a cooler arranged in series with one another, to the compression chamber of another cylinder which is phasedisplaced with respect to the first-mentioned cylinder through a crank angle which is a fraction 180 and the compression chambers of each said pair being intermittently interconnectable by way of an overflow path, comprising, at least for partial load, interconnecting the compression chambers of each said pair by way of the relevant overflow path for a time period extending throughout part of each of successiv working cycles of each said pair, and increasing said time period if the load decreases.

According to another aspect of the invention, there is provided in a double-acting hot-gas engine, a combination comprising four or a higher even number of cylinders each of which contains an expansion chamber and a compression chamber separated by a working piston and which comprise pairs of cylinders whereof the cylinders of each pair are phase-displaced with respect to each other through a 180 crank angle, a flow path connecting the expansion chamber of each cylinder to the compression chamber of another cylinder which is phase-displaced with respect to the firstmentioned cylinder, each flow path comprising a heater, a regenerator and a cooler arranged in series with one another, an overflow path whereby the compression chambers of each said pair are interconnectable intermittently, and valve means in each overflow path arranged to open and close the overflow path at intervals.

An overflow of working medium thus occurs during each working cycle at least in the range of reduced power. The indicator diagram area, and thus the ratio of the maximum pressure to the minimum pressure in the compression chamber and therefore in the associated expansion chamber, is thereby reduced. The change in the area of the diagram may be completed in one working cycle, provided that each overflow path is of a cross-section which permits a virtually unrestricted overflow of working medium between the two compression chambers. Assuming that this is so, the regulation takes place with the same low degree of inertia as in a Diesel engine. A further advantage of this invention resides in the fact that neither additional regulating vessels nor an auxiliary compressor are required for the working medium. When the overflow paths are unrestricted regulation occurs in a virtually loss-free manner.

The full capacity of a hot-gas engine of a given size is fully utilized in an advantageous manner by closing the overflow paths for full load.

' A gradual change from full load to partial load is advantageously achieved if the time periods for which the overflow paths are open occur in regions of the working cycles wherein the pressures in the relevant two compression chambers are substantially equal to each other at full loadConsequently, the relatively short open periods associated with high partial loads occur at zones in the piston travel in which the pressures in the two compression chambers differ only slightly from each other, so that only a relatively slight reduction in the diagram area occurs at high pressure differentials. With increasing open periods, associated with lower pressure differentials, a more pronounced reduction in the diagram area of necessity occurs since the open periods extend into zones of piston travel in which the pressures in the two compression chambers differto an increased extent at full load.

Continuous fluctuations in the diagram area when the load is constant are advantageously avoided by so selecting the positions of the opening and closing points of an open period that occurs or is altered for the first time that the opening and closing points of an equally long period following a crank angle coincide at least approximately with the points at which the pressures in the two compression chambers are at the same level.

An increase in the dead space in the hot-gas engine is advantageously avoided by making the valve means in each overflow path as two shut-off valves disposed one behind the other in the path.

BRIEF DESCRIPTION OF THE DRAWINGS In order that the invention may be clearly understood and readily carried into effect, reference will now be made, by way of example, to the accompanying drawings, in which:

FIG. 1 is a diagrammatic illustration of four cylinders of a six-cylinder hot-gas engine,

FIG. 2 is a diagram showing qualitatively the relationship between the pressures (P) in two interconnectible compression chambers of the engine and the crank DESCRIPTION OF THE PREFERRED EMBODIMENT FIG. I shows only four cylinders I, 2, 3 and 4 of a double-acting six-cylinder hot-gas engine. Each cylinder contains a compression chamber and an expansion chamber 6 separated from each other by a working piston 7. For the purpose of achieving the Stirling cycle the expansion chamber 6 of each cylinder is connected to a compression chamber 5 of another cylinder which when operating is phase-displaced with respect to the first-mentioned cylinder through a 60 crank angle, the connections being by way of a flow path which contains a heater 8, a regenerator 9 and a cooler It) arranged in series with one another. Thus there is connections between the expansion chamber 6 and the compression chamber 5 in the case of each cylinder pair I-2, 2-3, 3-4, 4-5 and 6'-l, the cylinders 5 and 6' not being shown in the drawings. The compression chambers 5 of each pair of cylinders of which the cylinders, when operating, are phase-displaced with respect to each other through a 180 crank angle, are interconnectible through overflow paths, only one of these paths, designated by the numeral II and between the cylinder I and the cylinder 4, being illustrated. The overflow path II can be intermittently closed by shut-off members I2 which are operated in synchronism with the associated pistons '7. Apart from the path II, the engine contains two further overflow paths, not illustrated, which can be intermittently closed in a corresponding manner and which establish connections between the compression chambers 5 of the cylinder pairs 2-5 and 3-6. The cylinders I, 2, 3 and 4 illustrated, as well as the cylinders 5' and 6 which are not illustrated, are filled with a suitable pressurised medium, usually helium. When the operating medium is forced from one of the expansion chambers 6 into the communicating compression chamber 5 by the phase-displaced movement of the two associated pistons 7, it stores most of its heat picked up from the heater 8 in the regenerator 9, whereas a smaller portion of the heat is yielded to cooling water'in the cooler I0. Thus, heat is extracted from the operating medium in this process and for this reason the compression chambers S are also called cold chambers. The heaters 8 are heated in a manner not illustrated by an external source of heat, e.g., an oil burner. When the operating medium is forced from one of the compression chambers 5 into the communicating expansion chamber 6 by the phase-displaced movement of the two associated pistons 7, it first absorbs the heat stored in the regenerator 9 and then is further heated in the heater 8. Thus, heat is supplied to the operating medium in this process and for this reason the expansion chambers 6 are also called hot chambers. The phase displacement between the movements of the individual pistons 7 has the effect of intermittently reducing and increasing the

chambers

5 and 6 interconnected in each case through the

elements

8, 9 and 10,

the compression of the operating medium taking place in the cold condition and its expansion in the hot condition. In this way an output of mechanical work is achieved, and this output is represented in the diagram of FIG. 4 by the area enclosed by the solid line, which relates to the full-load condition. In FIG. 4 the upper portion of the line represents the expansion process and the lower portion the compression process. In FIG.

2 the change in pressure in the chamber 5 of the cylinder I in relation to the crank angle (15 is shown by the curve I and that in chamber 5 of the cylinder 4 by the curve IV, both for the full-load condition. FIG. 3 shows what is meant by the crank angle (1). Under full load the shut-off members 12 are closed. Thus there is no overflow between the chambers 5 of any of the cylinders in this condition. Under partial load the shut-off members I2 are opened in the regions of the points A (FIG. 2) in the piston travel during each working cycle. When the shut-off members I2 open for the first time at points I and 4 on the curves I and IV, equalization of pressure occurs as indicated by the lines M and 4-4. The resultant confluence pressure does not necessarily occur about midway between the pressures at points I and 4 as shown in FIGS. 2 and'4, but depends upon the ratio of the energy contents of the operating medium in the interconnected chambers 5. The shut-off members remain open as far as the points designated I and 4" on the curves I and IV, so that a change in pressure corresponding to the curves I and IV now occurs. As can be seen from the broken-line curves in FIG. 4, the total diagram area is smaller than at full load, i.e., the power provided by the hot-gas engine is adapted to suit a reduced load. As the partial load increases, the points I, 4 and 4", 4 move progressively nearer to the points A until, at full load, they coincide with them.

I claim:

I. A method of obtaining load-responsive regulation of the power of a double-acting hot-gas engine comprising an even number of cylinders of at least four, each cylinder containing an expansion chamber and a compression chamber separated by a working piston, grouping said cylinders in pairs of cylinders, phasedisplacing the cylinders of each pair with respect to each other through a crank angle, connecting the expansion chamber of each cylinder, by way of a flow path containing a heater, a regenerator and a cooler arranged in series with one another, to the compression chamber of another cylinder which is phase-displaced with respect to the first-mentioned cylinder through a crank angle which is a fraction of 180, the compression chambers of each pair being intermittently interconnectable by way of an overflow path, at least for partial load, interconnecting the compression chambers of each pair of cylinders by way of the respective overflow path for a time period extending throughout part of each of successive working cycles of each pair, and increasing said time period if the load decreases.

2. A method according to claim I, and the step of maintaining the overflow paths closed at full load.

3. A method according to claim I, wherein the time periods for which the overflow path of each pair of cylinders is open occur in regions of said working cycles wherein the pressures in the respective two compression chambers would be substantially equal to each other at full load.

4. A method according to claim 3, wherein said time periods for which the overflow path of each pair is open, are displaced through 180 crank angle with respect to one another.

5. In a double-acting hot-gas engine, a combination comprising an even number of cylinders of at least four, each cylinder containing an expansion chamber and a compression chamber separated by a working piston, said cylinders being grouped in pairs of cylinders, the cylinders of each pair being phase-displaced with respect to each other through a 180 crank angle, a flow path connecting the expansion chamber of each cylinder to the compression chamber of another cylinder which is phase-displaced with respect to the firstmentioned cylinder through a crank angle which is a fraction of 180, each flow path comprising a heater, a regenerator and a cooler arranged in series, an overflow path for interconnecting intermittently the compression chambers of each pair, and valve means in each overflow path for opening and closing the overflow path at intervals.

6. A combination according to claim 5, wherein said valve means in each overflow path comprises first and second valve means adjacent the respective compression chambers interconnectable via said overflow path.

working piston.

Claims

1. A method of obtaining load-responsive regulation of the power of a double-acting hot-gas engine comprising an even number of cylinders of at least four, each cylinder containing an expansion chamber and a compression chamber separated by a working piston, grouping said cylinders in pairs of cylinders, phase-displacing the cylinders of each pair with respect to each other through a 180* crank angle, connecting the expansion chamber of each cylinder, by way of a flow path containing a heater, a regenerator and a cooler arranged in series with one another, to the compression chamber of another cylinder which is phasedisplaced with respect to the first-mentioned cylinder through a crank angle which is a fraction of 180*, the compression chambers of each pair being intermittently interconnectable by way of an overflow path, at least for partial load, interconnecting the compression chambers of each pair of cylinders by way of the respective overflow path for a time period extending throughout part of each of successive working cycles of each pair, and increasing said time period if the load decreases.

2. A method according to claim 1, and the step of maintaining the overflow paths closed at full load.

3. A method according to claim 1, wherein the time periods for which the overflow path of each pair of cylinders is open occur in regions of said working cycles wherein the pressures in the respective two compression chambers would be substantially equal to each other at full load.

4. A method according to claim 3, wherein said time periods for which the overflow path of each pair is open, are displaced through 180* crank angle with respect to one another.

5. In a double-acting hot-gas engine, a combination comprising an even number of cylinders of at least four, each cylinder containing an expansion chamber and a compression chamber separated by a working piston, said cylinders being grouped in pairs of cylinders, the cylinders of each pair being phase-displaced with respect to each other through a 180* crank angle, a flow path connecting the expansion chamber of each cylinder to the compression chamber of another cylinder which is phase-displaced with respect to the first-mentioned cylinder through a crank angle which is a fraction of 180*, each flow path comprising a heater, a regenerator and a cooler arranged in series, an overflow path for interconnecting intermittently the compression chambers of each pair, and valve means in each overflow path for opening and closing the overflow path at intervals.

7. A combinatiOn according to claim 5, wherein said valve means in each overflow path comprises a first control aperture formed in a member connected to the working piston of a cylinder of the respective pair, and a second control aperture formed in a regulating sleeve and co-operating with said first control aperture.

8. A combination according to claim 7, wherein each said member is a piston rod co-axial with the respective working piston.