GB1588612A

GB1588612A - Power control system in a hot gas engine

Info

Publication number: GB1588612A
Application number: GB9092/78A
Authority: GB
Original assignee: MAN Maschinenfabrik Augsburg Nuernberg AG
Current assignee: MAN AG
Priority date: 1977-03-09
Filing date: 1978-03-07
Publication date: 1981-04-29
Also published as: DE2710161C2; NL190128B; JPS53112351A; JPS6128825B2; SE7802647L; SE437284B; DE2710161A1; NL7801541A; NL190128C

Description

(54) POWER CONTROL SYSTEM IN A HOT GAS ENGINE (71) We, MAscHINENFABRIK AUGS- BURG-NURNBERG AKTIENGESELLSCHAFT, a German company, of 8900 Augsburg, Stadtbachstrasse 1, Germany, (Fed. Rep), do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following state ment :- This invention relates to a system for the power control of a hot gas engine (for example, a Stirling cycle engine) by the supply or removal of working gas to or from the working space of the engine.

British Patent Specification 1 307 972 shows a system in which working gas is removed from the working cycle space to lower, for example, the power of the hot gas engine, while the gas can expand into a variable volume chamber having a movable wall. Thereby, control fluid located on the other side of the movable wall is forced out of the variable volume chamber by the working gas and conducted to a store space acted on by a spring-loaded piston via a valve system.

In this known system, the expansion volume is determined by the volume of the variable volume chamber and the pressure in the working space can therefore only be lowered to a limited value corresponding to the volume of that chamber. For an effective system for lowering the power, a variable volume chamber, which would have to have a multiple of the volume of the working space, would be required for each working cylinder of the hot gas engine; such a system would therefore require a great deal of space and would incur a high production cost. As the pressure in the working space can only be lowered to a value which is determined by the size of the variable volume chamber, a relatively large residual volume of working gas remains, which is a disadvantage when the engine is dismantled in the case of damage or inspection.

An object of the invention is to provide a power control system by which the working gas can be extensively drawn out of the working space of a hot gas engine and can be conducted to a store space.

According to the present invention there is provided a hot gas engine having a system for controlling the power of the engine by transferring working gas between the working space of the engine and a storing space, said system comprising at least two variable volume chambers, each defined by a reservoir divided by a diaphragm and arranged to receive working gas on a first side of the diaphragm and a control fluid on a second side of the diaphragm, means for supplying control fluid alternatley under relatively high and low pressure to said reservoirs in turn, and a one-way valve arrangement for permitting the flow of working gas in only one selected direction between said working space and storing space, via said chambers.

The working gas is thus supplied or removed by the variable volume chambers, the diaphragms of which are acted on by communication or connection with the control fluid alternately of higher and lower pressure on their sides counter-balanced by the control fluid.

The variable volume chambers used with this system may thereby require a considerably lower volume than the variable volume chamber of the known systems. The system of the invention may be particularly advantageous in the case of hot gas engines with several cylinders, when one pair of alternately acting variable volume chambers with a common store space may be adequate, irrespective of the number of cylinders.

By way of example, should a lowering of the power of a hot gas engine be desired in the known system, then, in order to lower the cycle pressure to, for example, a tenth of the full load value of the engine, the maximum working volume of the variable chamber must be about ten times as large as the total working spaces of a cycle with which this chamber is associated. In the case of a four-cylinder engine of about 100HP and 8 dm3 working space, accordingly four variable volume chambers each of 20 dm capacity are required according to the known system.With a system of the invention, a store space with 15 dm3 capacity may be adequate for the total installation, whereby the pressure in the working cycle space of the engine can be even further reduced, and two variable volume chambers each with 1 dm3 capacity are therefore adequate for the hot gas engine. ~~ The pressure of the control fluid is advantageously produced by a supply pump which is driven by a motor and which causes the control fluid to act alternately on the diaphragms of the variable volume chambers.

It is advantageous for delivery lines leading from the supply pump to the spaces on the sides of the diaphragms remote from the working gas each to be provided with a pressure relief valve in order to avoid unacceptably high pressure surges and possible damage to the associated pipe system.

In order to use the remaining energy of the control fluid discharged by each pressure relief valve, this fluid can be conducted directly from the pressure relief valve to a suction pipe upstream of the pump, whereby the pressure drop to be overcome by the pump can be reduced.

In order to return the control fluid which escapes through leakage or through the pressure relief valves from the pressurised feed cycle between the diaphragms of the variable volume chambers and the pump, one-way valves can be disposed in suction pipes on the suction side of the pump.

The alternate action of the diaphragms of the variable volume chambers may be effected by reversing the direction of rotation of the pump motor.

In another embodiment, the alternate action on the diaphragms can be effected by reversing the direction of flow of the pump.

In the case of a pump which only supplies in one direction, the alternate action on the diaphragm of the variable volume chambers may be effected by a two-way valve which may be operated electromagnetically, or by a two-way valve which is fluid-pressure operable and is connected so as to be operated when the pressure of the control fluid on the side of the diaphragms remote from the working gas rises above or falls below a predetermined value.

In a preferred embodiment, the reversal of direction of flow of the control fluid takes place by means of a control unit acted on by a pressure switch provided for sensing a predetermined pressure level of the control fluid on the sides of the diaphragms remote from the working gas. It is advantageous to equip this control unit with a timing relay which delays the start or acceleration of the counter flow direction, in order to make possible a surge-free reversal.

The invention may be carried into practice in a number of ways but certain specific embodiments will now be described, by way of example only, with reference to the accompanying drawing, in which: Figure 1 is a functional diagram of a power control system of a hot gas engine in accordance with the invention, in the form of a block circuit diagram; Figure 2 shows another embodiment of the engine of the system according to Figure 1; and Figure 3 shows a further embodiment of a part of the system according to Figure 2.

The functional diagram according to Figure 1 shows two reservoirs 1 and 2 which are partitioned by respective flexible walls, or diaphragms 3 and 4, to define respective variable volume chambers. First and second sides of each diaphragm 3 and 4 are respectively in operative communication with two pipe systems 5 and 6 containing different media.

The pipe system 5 shown in Figure 1 to the left of the diaphragms 3 and 4 contains the working gas 7, e.g. helium, of a hot gas engine, whereas the pipe system 6 to the right of the diaphragms 3 and 4 contains a control fluid 8, e.g. hydraulic oil. The flexibly partitioned reservoirs 1 and 2 are acted upon alternately by the pressurised control fluid 8. The pressure is produced by a pump 10 driven by a motor 9, the pressurised control fluid 8 being conducted alternately to the flexibly partitioned reservoirs 1 and 2 via delivery pipes 14 and 15, so that the control fluid 8 is supplied alternately under high and low pressure to the reservoirs 1 and 2.

Pressure switches 16 and 17 are respectively disposed in the delivery pipes 14 and 15 and are actuated when a certain pressure is exceeded and act on a control unit 18, by which the pump motor is stopped and is subsequently switched to the opposite direction of rotation.

In order to avoid unacceptably high oil pressures, pressure relief valves 21 and 22 are disposed respectively in the delivery pipes 14, 15, the discharge of the valve being returned to a container 11. Suction pipes 12 and 13 which are connected to the delivery pipes 14, 15, have respective one-way valves 19 and 20 opening only in the direction of suction, through which the control fluid circuit, controlled by the pressure relief valves 21 or 22, is completed. Furthermore, coolers 23, 24 are disposed in the delivery pipes 14, 15.

In each of the embodiments according to Figures 2 and 3, there is one pump 25, supplying in one direction only, driven by a motor 26.

A delivery pipe 27 connected to the pump 25 leads to an electromagnetically actuated twoway valve 28, which alternately acts on delivery pipes 29, 30 leading to the flexibly partitioned reservoirs 1 and 2. A return pipe 31 leading from this two-way valve 28 is connected to the suction side of the pump 25 by flowing into a suction pipe 32, whereby the remaining energy contained in returned control fluid 8 can still be used to reduce the pressure drop to be overcome by the pump 25.

In order to prevent unacceptably high pressure in the delivery pipe 27, a pressure relief valve 33 is provided, which in the Figure 2 embodiment is located so that the excess pressure control fluid is returned to the container 11. In the case of the embodiment according to Figure 3, the control fluid conducted from the pressure relief valve 33 is conducted to the suction pipe 32. in order to make use of the remaining energy contained in this quantity of the control fluid to reduce the pressure drop across the pump 25.

Two containers 34 and 35 are shown connected via the pipe system 5, in which the working gas 7 of the hot gas engine is contained, to the chambers to the left of the diaphragms 3 and 4 of the flexibly partitioned reservoirs 1 and 2, as shown in Figure 1. One of the containers (34) represents the working spaces of the hot gas engine and the other (35) represents a store space. The working spaces 34 are connected to the flexibly partitioned reservoirs 1 and 2 via suction pipes 36, 37 which respectively contain one-way valves 38 and 39 which open only in the direction towards the flexibly partitioned reservoirs. Delivery pipes 40, 41 lead from the reservoirs 1 and 2 to the store space 35, the delivery pipes having respectively one-way valves 42 and 43 opening only in the direction towards the store space 35.Both delivery pipes 40, 41 join in front of the store space 35 to form a common delivery pipe 11, in which a working gas cooler 45 is disposed.

In the operation of the installation shown in Figure lithe working gas 7 is pumped from the working spaces 34 of the hot gas engine into the store space 35, whereby the cycle pressure of the engine can be lowered and thus its power can be reduced. As a result of pumping fluid 8 from the chamber to the right of the diaphragm 3 of the flexibly partitioned reservoir 1, a low pressure arises in the chamber to the left of the diaphragm 3, so that working gas 7 is sucked in through the suction pipe 36 and via the one-way valve 38 out of the working spaces 34 into the flexbly partitioned reservoir 1.During this process, the chamber to the right of the diaphragm 4 is simultaneously acted on by pressurised control fluid 8, so that the working gas 7 located in the chamber to the left of the diaphragm 4 is supplied to the store space 35 via the one-way valve 43 and the delivery pipes 41 and 44. Aback flow of the working gas 7 is prevented by the one-way valves 39 and 42, which block in the return flow direction. These working processes take place alternately in the two flexibly partitioned reservoirs 1 and 2, so that, according to the working duration of the alternately working flexibly partitioned reservoirs 1 and 2, amounts of working gas as may be desired can be pumped round from the working spaces 34 of the hot gas engine into the store space 35.

The alternate action on the flexibly partitioned reservoirs 1 and 2 by pressurised control fluid 8 takes place in such a way that control fluid 8 is supplied to the pump 10, e.g. from the reservoir 1 via the delivery pipe 14, and is supplied by the pump 10 via the delivery pipe 15 into the reservoir 2. The pump 10 works unitl a certain pressure has been attained in the reservoir 2, whereupon a pressure switch 16 is actuated, which switches the motor to the opposite direction of rotation via the control unit 18 so that the control fluid 8 is sucked out of the reservoir 2, while control fluid 8 is simultaneously conducted to the reservoir 1 via the delivery pipe 14 until a pressure switch 17, disposed in the delivery pipe 14, is again actuated once a certain pressure has been attained, and switches the motor to the opposite direction of rotation via the control unit 18.In order to avoid pressure surges in the pipe system 6, pressure relief valves 21 and 22 are disposed, through which control fuild 8 is conducted into the container 11 in the case of unacceptably high pressures. Equipping the control unit 18 with a timing relay serves to avoid these pressure surges and through this timing relay the switching of the motor 9 to the opposite direction of rotation can be delayed.

In the case of pumps 25 supplying in one direction only, as are shown in the embodiments according to the Figures 2 and 3, the alternate action on the delivery pipes 29 and 30 takes place via an electromagnetically actuated two-way valve 28, whereby the control fluid 8, returned from one of the flexibly partitioned reservoirs 1 or 2, is conducted to the suction side of the pump 25, in order to reduce the pressure drop to be overcome by the pump. Control fluid 8, which escapes from the circulation of the pipe system 6 through the pressure relief valves 21, 22 and the pump leakages, can be returned to the system from the container 11 via a suction pipe 32 containing a one-way valve 46.

In the above, there was described the lowering of the power of a hot gas engine, by operation of illustrated systems to pump working gas from the working or cycle spaces. It may readily be appreciated that a power increase can be attained by returning the highly pressurised working gas in the store (35) to the working spaces (34) of the hot gas engine. To this end, a similar one-way valve arrangement (not illustrated) can be provided in order to enable the pressure level in the store 35 to be lowered and working gas to be pumped from the store, in reverse sequence to that described above.

It may be appreciated that, in the illustrated systems, the circuits for conducting working gas between the working spaces 34 and store space 35 may readily be constructed as sealed systems, inwhichleakage of gas is substantially prevented.

WHAT WE CLAIM IS: 1. A hot gas engine having a system for controlling the power of the engine by transferring working gas between the working space of the engine and a storing space, said system comprising at least two variable volume chambers, each defined by a reservoir divided by a diaphragm and arranged to receive working gas on a first side of the diaphragm and a control fluid on a second side of the diaphragm, means for supplying control fluid alternately under relatively high and low pressure to said reservoirs in turn, and a one-way valve arrangement for permitting the flow of working gas in only one selected direction between said working space and storing space, via said chambers.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. pressure drop across the pump 25. Two containers 34 and 35 are shown connected via the pipe system 5, in which the working gas 7 of the hot gas engine is contained, to the chambers to the left of the diaphragms 3 and 4 of the flexibly partitioned reservoirs 1 and 2, as shown in Figure 1. One of the containers (34) represents the working spaces of the hot gas engine and the other (35) represents a store space. The working spaces 34 are connected to the flexibly partitioned reservoirs 1 and 2 via suction pipes 36, 37 which respectively contain one-way valves 38 and 39 which open only in the direction towards the flexibly partitioned reservoirs. Delivery pipes 40, 41 lead from the reservoirs 1 and 2 to the store space 35, the delivery pipes having respectively one-way valves 42 and 43 opening only in the direction towards the store space 35.Both delivery pipes 40, 41 join in front of the store space 35 to form a common delivery pipe 11, in which a working gas cooler 45 is disposed. In the operation of the installation shown in Figure lithe working gas 7 is pumped from the working spaces 34 of the hot gas engine into the store space 35, whereby the cycle pressure of the engine can be lowered and thus its power can be reduced. As a result of pumping fluid 8 from the chamber to the right of the diaphragm 3 of the flexibly partitioned reservoir 1, a low pressure arises in the chamber to the left of the diaphragm 3, so that working gas 7 is sucked in through the suction pipe 36 and via the one-way valve 38 out of the working spaces 34 into the flexbly partitioned reservoir 1.During this process, the chamber to the right of the diaphragm 4 is simultaneously acted on by pressurised control fluid 8, so that the working gas 7 located in the chamber to the left of the diaphragm 4 is supplied to the store space 35 via the one-way valve 43 and the delivery pipes 41 and 44. Aback flow of the working gas 7 is prevented by the one-way valves 39 and 42, which block in the return flow direction. These working processes take place alternately in the two flexibly partitioned reservoirs 1 and 2, so that, according to the working duration of the alternately working flexibly partitioned reservoirs 1 and 2, amounts of working gas as may be desired can be pumped round from the working spaces 34 of the hot gas engine into the store space 35. The alternate action on the flexibly partitioned reservoirs 1 and 2 by pressurised control fluid 8 takes place in such a way that control fluid 8 is supplied to the pump 10, e.g. from the reservoir 1 via the delivery pipe 14, and is supplied by the pump 10 via the delivery pipe 15 into the reservoir 2. The pump 10 works unitl a certain pressure has been attained in the reservoir 2, whereupon a pressure switch 16 is actuated, which switches the motor to the opposite direction of rotation via the control unit 18 so that the control fluid 8 is sucked out of the reservoir 2, while control fluid 8 is simultaneously conducted to the reservoir 1 via the delivery pipe 14 until a pressure switch 17, disposed in the delivery pipe 14, is again actuated once a certain pressure has been attained, and switches the motor to the opposite direction of rotation via the control unit 18.In order to avoid pressure surges in the pipe system 6, pressure relief valves 21 and 22 are disposed, through which control fuild 8 is conducted into the container 11 in the case of unacceptably high pressures. Equipping the control unit 18 with a timing relay serves to avoid these pressure surges and through this timing relay the switching of the motor 9 to the opposite direction of rotation can be delayed. In the case of pumps 25 supplying in one direction only, as are shown in the embodiments according to the Figures 2 and 3, the alternate action on the delivery pipes 29 and 30 takes place via an electromagnetically actuated two-way valve 28, whereby the control fluid 8, returned from one of the flexibly partitioned reservoirs 1 or 2, is conducted to the suction side of the pump 25, in order to reduce the pressure drop to be overcome by the pump. Control fluid 8, which escapes from the circulation of the pipe system 6 through the pressure relief valves 21, 22 and the pump leakages, can be returned to the system from the container 11 via a suction pipe 32 containing a one-way valve 46. In the above, there was described the lowering of the power of a hot gas engine, by operation of illustrated systems to pump working gas from the working or cycle spaces. It may readily be appreciated that a power increase can be attained by returning the highly pressurised working gas in the store (35) to the working spaces (34) of the hot gas engine. To this end, a similar one-way valve arrangement (not illustrated) can be provided in order to enable the pressure level in the store 35 to be lowered and working gas to be pumped from the store, in reverse sequence to that described above. It may be appreciated that, in the illustrated systems, the circuits for conducting working gas between the working spaces 34 and store space 35 may readily be constructed as sealed systems, inwhichleakage of gas is substantially prevented. WHAT WE CLAIM IS:

1. A hot gas engine having a system for controlling the power of the engine by transferring working gas between the working space of the engine and a storing space, said system comprising at least two variable volume chambers, each defined by a reservoir divided by a diaphragm and arranged to receive working gas on a first side of the diaphragm and a control fluid on a second side of the diaphragm, means for supplying control fluid alternately under relatively high and low pressure to said reservoirs in turn, and a one-way valve arrangement for permitting the flow of working gas in only one selected direction between said working space and storing space, via said chambers.

2. An engine as claimed in Claim 1, in which

a pump driven by a motor is provided for developing the pressure of the control fluid which acts alternately on the diaphragms to vary the volumes of the variable volume chambers.

3. An engine as claimed in Claim 2, in which delivery lines leading from the pump to the second sides of the diaphragms each include a pressure relief valve.

4. An engine as claimed in Claim 3, in which a discharge line connected to the pressure relief valve is connected into a suction pipe upstream of the pump.

5. An engine as claimed in any of Claims 2 to 4, in which a one-way valve is disposed in a suction line upstream of the pump.

6. An engine as claimed in any one of Claims 2 to 5, in which the direction of rotation of the motor is reversible and in which the pump is operable in either direction or rotation of the motor whereby the alternate action on the diaphragms is achieved by reversing the motor.

7. An engine as claimed in any one of Claims 2 to 5, in wiiich, for a given direction of rotation of the motor, the pump is adapted to pump in either direction of flow, as selected, whereby the alternate action on the diaphragms is achieved by reversing the direction of flow of the pump.

8. An engine as claimed in any of Claims 2 to 5, in which the pump is adapted to pump in one direction only and in which a two-way valve is provided for alternating the action of the fluid pressure on the diaphragms.

9. An engine as claimed in Claim 8, in which the two-way valve is electromagnetically operable.

10. An engine as claimed in Claim 8, in which the two-way valve is fluid-pressure operable and is connected so as to be operated when the pressure of the control fluid on the second side of one of the diaphragms rises above or falls below a predetermined value.

11. An engine as claimed in any of Claims 6 to 10, in which, for effecting the alternation of the action of the pressure of the control fluid on the diaphragms, a pressure-responsive switch is provided for sensing a predetermined pressure level of the control fluid on the second sides of the diaphragms, the pressure switch being connected to a control unit which is adapted to produce a change-over signal for reversing the direction of flow of the control fluid.

12. An engine as claimed in Claim 11, in which the control unit includes a timing device adapted to delay the commencement of the flow of the control fluid in the reverse direction.

13. A hot gas engine having a system for the power control thereof, substantially as specifically described herein with reference to Figure 1 or to Figure 1 as modified by Figure 2 or Figure 3 of the accompanying drawing.