DE2209482A1 - Multi-cylinder hot gas piston engine in which the fuel supply to the burner devices is regulated by means of temperature-sensitive elements - Google Patents

Description

Registration vomi j ο ο / ft 1}

"Multi-cylinder hot gas piston engine in which the fuel supply to the burner devices by means of temperature-sensitive Elements is regulated ".

The invention relates to a multi-cylinder ice-gas piston engine in which each cylinder is provided with a heater to which heat originating from an associated burner device can be supplied Brennervorrichttmg remote ends to connect to a common fuel supply line, in which a pressure control device maintains a constant pressure during operation, and the combustion air supplies with their from the associated

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Connect the burner device facing away ends to a common combustion air supply line, each The heater is equipped with a temperature-sensitive element that regulates the fuel in the Fuel supply of the associated burner device for regulating the fuel flow to the mentioned device actuated, viewed downstream in each fuel supply a flow obstruction in front of the fuel control mechanism "· Stand element is present on which, in operation, the speed of the fuel flow through the relevant Supply proportional pressure difference prevails, with the amount of combustion air to be supplied depending on the supplied amount of fuel is regulated.

A hot gas piston engine of the type relating to the invention is known from British patent specification 895 * 869. In the patent specification mentioned, a regulation of the amount of combustion air to be supplied to the burner device as a function of the amount of fuel to be supplied is described for a single-cylinder hot gas piston engine. In this case, pressure difference meters are provided in the fuel supply and the combustion air supply, which act independently of one another, but in the opposite sense, on the same element of a hydraulic system that regulates the position of a throttle valve in the combustion air supply as a function of the fuel flow in the fuel supply. This known construction for regulating the supply of fuel and combustion air to the burner device of a single-cylinder ICE gas piston engine has some disadvantages,

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which make them less recommendable for use in multi-cylinder hot gas piston engines. First of all you have to very high demands are placed on the control mechanism in the fuel line. The passage must namely over a large fuel range precisely and be reproducibly adjustable. If these requirements are not met, this is particularly the case with small ones Fuel flows all sorts of difficulties, like going out of the burner, instability of the temperature control circuit and incomplete combustion of the air-fuel mixture dirty, unhealthy exhaust gases, what through incorrect fuel metering is caused. For the Pressure difference meter in the fuel supply line means a large ratio of the largest to the smallest Fuel flow that this Hesser accurate and reproducible Must be able to measure pressure differences within a very large measuring range, the pressure difference generated is here namely, according to Bernouilli's law of flow, proportional to the square of the flow velocity,

The use of such a solution in multi-cylinder hot gas piston engines is also even less advisable because there are just as many rule systems in this case required how cylinders are present. The air-fuel control then consists in its entirety of a very complex whole, that of a large whole Number of relatively expensive components is built.

The present invention aims to provide an air-fuel control system for multi-cylinder hot gas meters

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create a simple construction with a relatively small number of inexpensive components combined with a reliable mode of operation.

In order to achieve the intended aim, the multi-cylinder hot gas piston engine according to the invention the indicator that a selection device for the automatic selection of the maximum or minimum fuel pressure from several fuel inlet pressures is present and that the outlet sides of the flow resistance elements are connected to as many inputs of the selection device, the pressure difference between the constant fuel pressure in the common fuel supply line and the selected maximum or minimum fuel pressure influences a control element, the one Combustion air control mechanism in the common combustion air supply line actuated.

By using the selection device, which can be very compact and simple, im need In contrast to the known control system already mentioned, there is no pressure differential meter and throttle valve in each Combustion air supply to be available. This results in a considerable saving in terms of components.

An even more significant saving is achieved in that it is now unnecessary for each Burner device separates the air and fuel flow to compare to the burner device and via an associated control system such as that in that mentioned hydraulic described in British Patent 895 * 869

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To coordinate the system with each other. Now is just a rule system required, with which the air flow through the common combustion air supply line to the maximum fuel flow is matched from the various fuel flows, which are generated by the fuel feeds of the burner pre-seals, flow by choosing a selection device that selects the minimum fuel pressure.

Due to the achieved savings of relatively costly components due to the introduction of a simple selection device is a multi-cylinder hot gas piston engine obtained with a cheap, simple and inexpensive air-fuel control. Doing so is irrespective on the number of cylinders, only one fuel pressure difference sensor is required, to which the fuel pressure difference signal is fed.

Furthermore, since the fuel flows to the various Burner devices with each other directly via diö Selection device are compared, the control system works regardless of the type of fuel control, Here sources of error that would occur with indirect comparisons are avoided at the same time.

The flow resistance elements can be very easily be designed, for example, as thin plates provided with a hole, such as in "Construction" 2jO (1968) No. 3, S, 1111 "Orifice plates for small Reynolds numbers" is described.

With multi-cylinder hot gas engines, ot- ± U. ^ a: the fuel flow is from

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Burner device of, for example, 0.02 gr / sec. until 1.2 g / sec. (Ratio 1 to 60) can change, this means a ratio for the preferably with one or several plates generated minimum to maximum pressure difference of 1 t 3600. Because this ratio and thus Even the required measuring range is very large, the measuring device becomes complicated and expensive · It is also almost impossible, for small fuel flows of a few hundredths of a gram per second a turbulent and to realize temperature-independent flow in the plates »

A sufficiently reliable air-fuel control in the case of small fuel flows, this is not the case possible and carries the risk of an air-fuel ratio that is too small with these small fuel flows, causing incomplete combustion and dirty exhaust gases appear.

In order to avoid this disadvantage, a favorable embodiment of the multi-cylinder hot gas piston engine according to the invention a fuel auxiliary line present, one end of which is connected to the common fuel supply line, whereby in the auxiliary line likewise a flow resistance element is added, at the input side of which the constant fuel pressure prevails, and the output side of which is also connected to an input of the selection device, which selection device selects the minimum fuel pressure, wherein also into the auxiliary fuel line, seen downstream

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is chosen according to the flow resistance element, a fixed throttle is received _f in such a way that below a certain minimum fuel flow through the fuel feeds the pressure prevailing at the output side of the flow resistance element in the fuel auxiliary line, likewise constant pressure is lower than the pressures that the in the case of Exit sides of the flow resistance elements prevail in the fuel supplies.

In this way it is achieved that below a certain minimum fuel flow without consideration to the value that the fuel flow then assumes get a constant value for the fuel pressure difference that influences the regulating body. The amount of combustion air supplied is then also constant and sufficient large for any fuel flow below the minimum mentioned. A complete combustion is therefore with small fuel flows guaranteed in all cases.

Under certain circumstances it can happen that the combustion air feed line originating from the common Airflow is not even enough across the various Combustion air supplies distributed, for example through Differences in those of the associated burner devices from counter pressures acting on the feeds or through different flow resistance values of the feeds mentioned. There is then the risk that an insufficient amount of combustion air is supplied to a burner device, in order to guarantee a complete combustion of the supplied fuel quantities. This in turn would be dirty,

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cause harmful exhaust gases. For this Sometimes it may be desirable to be more certain about the reason the amount of air flowing through the combustion air supply, namely to have the smallest flow of combustion air.

This can be done on a multi-cylinder hot gas piston engine, with a further flow resistance element in each combustion air supply is present at which, during operation, the speed of the combustion air flow through the relevant supply proportional pressure difference prevails, another selection device for automatic selection the maximum combustion air pressure from several combustion air inlet pressures, and the outlet sides of the further flow resistance elements can be connected to just as many inputs of the further selection device being the pressure difference between the combustion air pressure on the inlet side of the further flow resistance elements and the selected maximum combustion air pressure influences the regulating element in the opposite sense as the fuel pressure difference.

Since the further selection device the MaximaΙα jerk at the output sides of the further flow resistance elements selects the prevailing combustion air pressure, this device follows the smallest combustion air flow all due to the different combustion air supply en flowing streams.

A suitable setting of the control system now ensures that this minimal combustion air flow is still large enough for complete combustion

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of the maximum fuel flow from the various, too to guarantee fuel flows to the various burner devices.

In the present case, again, only a general system of rules is required, instead of that for everyone Cylinder or each burner device must have a separate control system The simple measuring plates already mentioned come into consideration again, but if desired For example, pitot tubes or venturi tubes can also be used. Just like the selection device the further selection device can also be designed in a simple and compact manner.

Therefore, there is a further development of the invention Multi-cylinder hot gas piston engine, the selection device or, the further selection device from a Number of non-return valves that only pass in one direction, next to one another with one that is aligned in the same way Passage directions are arranged, with one side of the valves having inputs for the same number of input pressures form and connect with their other side to a common output, with the bin and output side each Valve always by means of a leakage throttle in the open connector? -F stand together.

Furthermore, each check valve can have a film element as the valve body, which is sealingly with can interact with a seat, and what foil element is stranded with a hole as a lock throttle; <-.

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The invention will now be explained in more detail with the aid of some exemplary embodiments shown in the drawings. Show it:

1 to 3 embodiments of air-fuel control systems for a four-cylinder hot gas piston engine in which each control system has a selection device is provided, with the help of which the maximum fuel flow from the four fuel streams flowing to the four different burner devices or from the four mentioned Flows and a fifth constant flow is selected, and the total flow of combustion air to the burner devices is matched to the mentioned maximum fuel flow.

Fig. K shows an embodiment of an air-fuel control system for a four-cylinder hot gas piston engine, in addition to the selection device for the maximum fuel flow, a further selection device is present, with the aid of which the minimum combustion air flow is selected from the four combustion air flows flowing to the four different burner devices, where the minimum combustion air flow is compared again with the maximum fuel flow and the entire combustion air flow is derived therefrom,

5 shows three embodiments of selection devices,

6 shows an embodiment of a pressure difference transducer, in which a difference in two pressure signals supplied to it is converted into an electrical signal,

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7 shows an embodiment of a combined Pressure difference comparison and transducer element in which two pressure differences supplied to it (four pressure signals) are compared and the difference is converted into an electrical signal.

In Fig. 1, the reference number 1 is a four-cylinder hot gas piston engine referred to, in which each cylinder with a heater, not shown, with the associated burner device 2 is provided.

A fuel supply 3 and a combustion air supply h are connected to each burner device 2. Di «? fuel feeds 3 are all connected to a common fuel feed line 5 in which a fuel pump 6 is present, with which fuel can be fed from a fuel container 7 to the fuel feeds 3.

To the common fuel supply line a fuel return flow line 8 connects to it, in which has a pressure control valve 9 which, during operation, maintains a constant pressure in the common fuel supply line 5 and therefore also on the entrance sides of it subsequent fuel supplies 3 maintains.

The combustion air supplies k are all connected to a common combustion air supply line 10.

Each of the four unspecified heaters is temperature-sensitive with a thermocouple 11 Element with which the heater temperature is determined during operation,

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The electrical signals supplied by the thermocouples 11 are each separately in a central amplifier unit 12 reinforced. Each amplified signal determines the position of an electromagnetic one Valve 13 as a fuel control mechanism in the fuel supply 3 of the burner device belonging to the heater in question 2.

In each fuel supply 3 is seen downstream in front of the electromagnetic valve 13, a flow resistance selement 14 is present on which one of the during operation Speed of the fuel flow through the relevant supply proportional pressure difference prevails. The flow resistance elements can be made simple, for example like the known thin ones provided with a bore Plates. If desired, however, pitot or Venturi tubes or the like can be used.

There is a selection device 15 available, which has four inputs to which the four output sides of the flow resistance elements 1 ^ are connected via lines 16 are.

The selection device 15 selects the minimum pressure of the four on the output sides of the flow resistance elements 14 prevailing pressures from which minimum pressure is fed to a pressure difference sensor 17 as a control element. The pressure difference sensor 17 is also via a Line 18 is fed directly to the constant pressure that prevails on the input side of the flow resistance elements 1U.

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In the pressure difference sensor 17, the difference in two pressures supplied to it is converted into an electrical signal converted, which is amplified in an amplifier 19. With the amplified signal the position of an electromagnetic Valve 20 as a combustion air control mechanism in the common combustion air supply line 10 regulated. The pressure difference sensor 17 can, for example be carried out as shown in the Pig to be described.

The operation of the air-fuel control system is as follows.

During operation, the fuel pump 6 pumps fuel from the fuel tank 7 to the fuel feeds 31 while combustion air is fed to the common pre-combustion air feed line 10 in a manner not specified, which is distributed over the four combustion air feeds k .

Due to the control action of the pressure control valve 9, there is a constant pressure on the inlet sides of the Flow resistance elements 14. Via the line 18 is the pressure difference sensor 17 therefore a constant pressure signal fed.

The fuel flow passing through the relevant fuel supply 3 ²⁵ U of a burner device 2 depends on the temperature of the associated heater. If the temperature of the heater falls, for example because more power is being drawn from the relevant cylinder, the relevant thermocouple 11 ensures that the relevant

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electromagnetic valve is opened more and that more fuel can flow to the mentioned burner device. Conversely, if the temperature of the heater rises, the thermocouple 11 ensures that the valve 13 increases is closed and that less fuel is allowed through to the burner device.

Since the pressure at the inlet sides of the flow resistance elements is constant for 1 h and since the pressure drop across such an element increases with increasing fuel flow through the element, this means that the lowest of the pressures prevailing at the outlet sides of the flow resistance elements 1 k is in that fuel supply 3, through which the largest flow of fuel passes.

As noted earlier, the selection ' device 15 now this lowest fuel pressure from the four pressure signals supplied to it via lines 16. The pressure difference acting on the pressure difference sensor 17, that by the difference between the constant pressure at the inlet sides of the flow resistance elements 1 ^ and the minimum pressure is formed, which is formed from the four prevailing on the outlet sides of the mentioned elements Pressures selected therefore represents the maximum fuel flow of the various, through the four fuel supplies 3 represent currents going to the four burner devices 2.

Because of this the maximum fuel flow The pressure difference representing the total amount of the four burner devices supplied is now the same

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Combustion air is regulated by the electrical signal derived from the pressure difference after amplification in the Amplifier 19 regulates the position of the electromagnetic valve,

If the air-fuel control system is now set in such a way that the total per unit of time is supplied Pollution air volume is at least four times the polluting air volume that is required to achieve complete combustion of the maximum fuel flow guarantee, so is a complete combustion of the other three fuel flows, which are smaller than that selected fuel stream, practically always secured.

The whole control system of the present four-cylinder hot gas piston engine has a simple construction and it consists of a very small number of components, In the description of FIG. 5 is explained in more detail on which Veise the selection device 15 can be implemented.

In practice, the common combustion air supply line is often supplied with combustion air with the aid of a fan which is coupled to a shaft of the motor. Depending on the engine speed, the flow rate of the fan is changed. Be if the fan is coupled to a multi-cylinder Heissgaskolberaniotors corresponding to FIG. 1 with a shaft, it must ensured that at a variable, dependent on the rotational speed input to the VerbrennungsliiftzufUhrungsleitunß 10 to the combustion air supplies h durdigelassene combustion air amount to the maximum fuel

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stream remains matched, which is selected from the various streams through the fuel supplies.

A solution for this is shown in FIG. The air-fuel control system according to FIG. 2 is broadly the same as in FIG. 1, so that the same reference numerals are used for corresponding parts. In the present case there is a fan 21 with which combustion air is supplied to a common combustion air supply line 10. The shaft of the fan 21 is coupled to a shaft of the motor, which is not shown in the drawing. In the common combustion air supply line 10 there is a combustion air flow resistance element 22 which generates a pressure difference proportional to the combustion air flow through the mentioned line, which pressure difference is fed to a pressure difference sensor 23. The pressure difference supplied to this sensor is then converted into an electrical signal which, in the opposite sense as the electrical signal originating from the pressure difference sensor 17, influences an electrical comparison element 2k as a control element.

The comparison element 2k regulates the position of the electromagnetic valve 20 on the basis of the difference between two electrical signals supplied to this element.

If the fan speed and thus the amount of air that passes through valve 20 increases, then that also increases The size of the combustion air flow resistance element 22 created pressure difference signals au and

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thus also that of the electrical signal derived from it. The comparison element 2k now ensures that the valve 20 is closed so far that the original amount of combustion air passes through valve 20 again. If the fan speed and thus also the amount of air passing through the valve 20 decreases, the element 2k ensures that the valve 20 opens more so that the original air flow is maintained.

The combustion air flow resistance element 22 can, for example, be a Pitot tube or a Venturi tube, made up of one or more plates provided with holes, but it can also be designed as an anemometer 2k can be fed. The characteristics of this anemometer and those of the pressure difference sensor 17 must be matched to one another.

The pressure difference sensors 17 and 23 can so

be carried out, as is given as an example in FIG. 6, which is yet to be described. For both pressure sensors, together with the comparison element 2k, a combined unit can be used, as shown in FIG. 7, which is yet to be described.

With the in ELg. 1 urr. ' 2 shown air-fuel control systems the entire flow of combustion air the maximum fuel flow of the various flows through the fuel supplies 3 matched as the selection device 15 the minimum pressure from the various to the

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Output sides of the flow resistance elements selects lh prevailing pressures.

With small fuel flows through the fuel supply 3, the pressure differences between the inlet and outlet sides of the flow resistance elements 1 ** are small. Small pressure differential signals are essential for accurate air-fuel control unfavorable. In addition, it is practically impossible with the measuring plates that are preferably used is, with small fuel flows the flow through the To make plates turbulent and thus independent of temperature. This leads to inaccurate air-fuel control with small fuel flows, resulting in low air-fuel ratios with these small fuel flows and consequently incomplete combustion with dirty ones Exhaust fumes.

This problem no longer exists with the air-fuel control system According to Fig. 3, “that in broad outline is the same as that shown in Fig. 1 and the same reference numerals used for corresponding parts are.

The control system according to Fig. 3 differs ^ inasmuch from that of FIG. 1 that in the present case, a fuel auxiliary duct 30 is present, the nschliesst with one end to the common fuel supply line 5 ^a and opens with its other end in the fuel tank 7 . In the auxiliary fuel line 30, as in the fuel supply lines 3, there is a flow resistance element '\ k, the output side of which is also

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via a line 16 with an additional fifth input the selection device 5 is connected, which, as already mentioned, selects the minimum pressure. Furthermore, in the auxiliary fuel line 30 has a fixed throttle 31

Since there is a constant pressure on the inlet side of the auxiliary fuel line 30 during operation, the presence of the fixed throttle 31 on the outlet side of the flow resistance element 1 k will also result in a constant pressure in this conduit, and a constant flow of fuel through the auxiliary fuel line will lead to the fuel tank 7 flow away.

The fixed throttle 31 and that through the auxiliary fuel line 30 flowing fuel streams are now like this chosen that this fuel flow has a certain minimum value the fuel flows through the. different fuel supplies 3 corresponds. The fuel flows through the fuel supplies are above this specific minimum value s all greater than the constant fuel flow through the auxiliary fuel line 30, in which case the pressures are on the output sides of the flow resistance elements 14 in the fuel feed 3 all lower than the constant Pressure on the outlet side of the flow resistance element "l · in the auxiliary fuel line 30, as the auxiliary device 15 of the five pressure signals supplied are that selects smallest, this mini-final print is always sigial one of the four originating from the fuel supply 3 Pressure signals. The auxiliary fuel line 30 is then in with regard to the air-fuel regulation passive,

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The fuel flows come through the fuel feeders 3, however, all below the minimum value of the constant fuel flow through the auxiliary fuel line corresponds, then, since the last-mentioned flow is then the greatest, the pressure on the outlet side of the flow resistance element 14 in auxiliary fuel line 30 lower than all prevail on the outlet sides of the flow resistance elements 14 in the fuel feeders 3 the pressures. The selection device 15 then selects as Minimum pressure from the auxiliary fuel line 30 Pressure signal. Because this signal is due to the constant pressure on the outlet side of the flow resistance element is constant in this line, the pressure difference sensor 17 is supplied with a constant signal. This means, that the total amount of combustion air supplied per unit of time remains constant, since the position of the electromagnetic valve 20 no longer changes.

In this way it is achieved that below a certain minimum value for the fuel flows through the Fuel supply 3 the entire combustion air flow remains constant regardless of what value the then accept the mentioned fuel flows. If the whole Combustion air flow when the fuel flows through the Fuel feeds have 3 values that are equal to the minimum are worth is large enough to achieve complete combustion of the flows mentioned, so is the entire air flow certainly large enough for complete combustion of fuel streams by the fuel supplies that

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are below this minimum value. A complete Combustion is therefore practically always guaranteed, while an unreliable measurement of small fuel flows by the fuel supplies 3 no longer required is and is avoided.

In the air-fuel control systems shown in FIGS the entire combustion air flow is always carried through depending on the maximum fuel flow one of the fuel supplies 3 or from the maximum fuel flow of the variable currents through the fuel supplies and the constant flow through the auxiliary fuel line regulated.

It is assumed here that the entire combustion air flow through the common combustion air supply line 10 is distributed evenly over the four combustion air supplies h . Under certain circumstances, however, it can happen that the latter is not always the case to a sufficient extent. The cause may be in different ο trömung.swiderstandswerten the combustion air feeds h llof, en, it is also possible that the burner devices 2 from different back pressures of the combustion air supplies become noticeable. This can have the consequence that too little combustion air is supplied to a combustion air supply in order to guarantee complete combustion of the fuel carried by the corresponding fuel supply, which results in dirty exhaust gases as far as the burner device is concerned.

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This disadvantage is avoided in the k in Fig. Shown air-fuel control system. In this system, the same reference numerals are used for parts that correspond to the system of FIG. 3. The present system differs in the following points from that according to FIG. 3. In each combustion air supply k there is a further flow resistance element kO , on which, during operation, there is a pressure difference proportional to the speed of the combustion air flow through the relevant supply. As further flow resistance elements kO , plates, pitot tubes, venturi tubes or the like provided with one or more bores come into consideration. At the same time there is a further selection device 4i which automatically selects the maximum combustion air pressure from a plurality of combustion air inlet pressures.

The four output sides of the further flow resistance elements kO are connected to the same number of inputs of the further selection device kl via the lines k2.

The common pressure prevailing on the inlet sides of the further flow resistance elements kO , namely the pressure in the common combustion air supply line and the maximum pressure selected by the further selection device 41 from the various pressures prevailing on the outlet sides of the mentioned elements, are each separately fed to a pressure difference sensor kj. The difference between the two pressures is converted in this sensor into an electrical signal, which is an electrical

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Comparison element ^ 4 influences in the opposite sense as the electrical signal originating from the pressure difference sensor 17. The comparison element hh operates the electromagnetic valve 20 on the basis of the difference between the electrical signals supplied to this element.

The pressure difference sensor k3 has a characteristic which has the same shape as that of the differential pressure sensor 17 "Both pressure difference sensor may be designed, for example, in Fig. 6 is shown again, or they may, together with the comparison element hk be designed as a unit, for example, the type shown in Fig. 7 and ',' otherwise,

Since the further selection device hl the maximum pressure from the different, at the output sides of the further Strömungswiderstandselen'ente ho prevailing pressures selects, this means that eggs selected Maxisnaldruek from that combustion air supply neriiilirt h, by which Ström passing the small former e combustion air _a Pressure "Waste in the further flow resistance present in that combustion air supply is there; i * iralieh is the smallest, while the same common flow; on the entrance sides of all other S ^ r ^ aiingsi '/ iäex'stanäseleirä'is.te · prevails. The Druckunterscliiedfüiilei the * ^ -3 sugsftliii'te pressure difference therefore represents the closest V'erbrennuiigs "airflow all through the Verbrennungsluftzitftihren h continuous streams represent"

This means that the smallest, at least all, flowing through the various combustion air supplies h

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ZH

Flows selected combustion air flow depending on the maximum fuel flow is regulated with the Selection device 15 from the variable fuel flows through the various fuel supplies 3 and the constant flow of fuel through the auxiliary fuel line 30 is selected.

If the control system is now set in such a way that the selected minimum combustion air flow through a combustion air supply k is large enough to be able to completely burn the selected maximum fuel flow through a fuel supply 3 or through the auxiliary fuel line 30, it is automatically guaranteed under all circumstances that all Fuel flows through the fuel supplies 3 are completely burned by the combustion air flows through the corresponding combustion air supplies k. The possible cases are then that the maximum fuel flow or a smaller fuel flow is allocated the minimum combustion air flow or a larger combustion air flow.

The mode of operation of the present control system is also the same as that according to FIG. 3, so that a further description is omitted. Of course, in the present case, the control system can, if desired, be designed without auxiliary fuel line 30. In addition to the further flow resistance elements kO , only one further selection device 4i is required, which again can be compact and simply constructed. A separate regulation

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for each burner device is avoided, so that the entire control system from a relatively small Number of inexpensive components is built.

As with the control system according to FIG. 2, combustion air can also be supplied in the present case to the common combustion air supply line 10 by means of a fan directly coupled to a shaft of the motor, the flow rate of the fan changing when the engine speed changes. It should be noted that in this case, and not only in that case, it is not always necessary to maintain a constant pressure in the common combustion air supply line 10 and thus at the inlet sides of the further flow resistance elements hO . If, for example, the engine speed and thus the fan speed increase, as a result of which the total amount of combustion air supplied and the pressure on the inlet sides of the further flow resistance elements kO increase, the pressure on the outlet sides of the elements mentioned increases to the same extent. The pressure difference supplied to the pressure difference sensor 42 remains unchanged, so that the only practical consequence is a supply of a larger excess of combustion air to the burner device 2. This need by no means be disruptive, but can even be advantageous under certain circumstances. It only has to be ensured in the first place that the selected minimum combustion air flow is selected large enough in relation to the selected maximum fuel flow.

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In the control systems according to Fig. 1 to k , pressure differences are always converted into electrical signals. It is of course also possible to feed the fuel pressure differences directly to the control mechanism in the common combustion air supply line, which control mechanism can then be designed as a hydraulically controlled valve. to compare the fuel pressure difference and the combustion air pressure difference directly in, for example, a hydraulic comparison element and to have the difference between the two pressure difference signals actuate the control mechanism, which is designed as a hydraulically controlled valve, in the common combustion air supply line, for example in the manner corresponding to the British patent 895,869 for the direct Comparison on the hydraulic route of the fuel and combustion air flow to the burner device of a single-cylinder hot gas piston engine «Im Ge In contrast to this known single-cylinder hot-gas piston engine, only one comparison element is required in the present multi-cylinder hot-gas piston engine, regardless of the number of cylinders.

Further, in the control systems of Figure 1 to h is always a multi-cylinder hot-gas piston engine shown. Of course, while maintaining the advantages, the systems shown in the figures mentioned can be used equally well in multi-cylinder hot-gas piston engines which have different numbers of cylinders. An extension to, for example, eight-cylinder hot gas piston engines only means

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a relatively small increase in the total number Necessary components, as one selection device or further selection device can always suffice

How such a selection device or further selection device can be designed is shown in FIG. 5. 5a and 5b show selection devices for the automatic selection of the minimum pressure from four input pressure signals, while in FIG. 5 ° a selection device is shown which automatically selects the maximum pressure from four input pressures. In Fig. 5a, the reference number 50 denotes a housing in which four Rticksclil permeable in the same direction: · =. valves 51 are arranged side by side. Each check valve 51 has a spherical valve body 52, the mil; a valve seat 53 can cooperate in a sealing manner, lines 5k guided through the wall of the housing 50 form the inlet sides of the valves, outlet sides of the valves formed by the lines 55 are connected to a common outlet 56 which is guided to the outside through the wall of the housing. The inlet side 5 and the outlet side 55 of each valve 51 are in open communication with one another via a line 57 in which a leakage throttle 58 is located. The operation of this selection device is as follows.

If the pressures in the lines 5k, that is to say at the inlet sides of the valves 51, are all higher than in the lines 55 or the common outlet 56, the valve bodies 52 are pressed against the valve seats 53 in a sealing manner,

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ZS

If, however, a pressure occurs in only one of the lines 54 which is lower than the pressure in the common outlet 56, the check valve 51 connected to the aforementioned line $ k immediately releases the connection between this line 54 and the relevant line 55, in that the valve body 52 in question moves (upwards) from its seat 53 under the influence of the pressure difference that occurs. In the common outlet 56 , the lower pressure is then set, which prevails in the aforementioned line 5 ^, while the other check valves 51 remain closed. In this way, the minimum pressure selected from the various input pressures prevails in the common output 56. The leakage throttles 58 ensure that in the event of pressure increases in the lines 54, the pressure in the common outlet 56 can slowly follow these pressure increases so that the pressure in the outlet 56 in the steady state does not differ significantly from the lowest of the inlet pressures prevailing in the lines. The extent to which a leak can occur and the associated choice of leakage restrictors depend on the application. For the selection device 15 from the control system according to FIG. 1, the specific change in volume of the chamber of the pressure difference sensor 17 connected to the common outlet is important, paying attention to the permissible deviation in the pressure sensed by the pressure sensor from the actual minimum pressure got to"

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The same reference numerals are used for the selection device according to FIG. 5b as for that according to FIG. 5a,

The valve bodies 52 here consist of film elements which cooperate with the seats 53 in a sealing manner can. The leakage throttles 58 consist of such in the Foil elements provided holes that they cannot be closed by the seats 53. The mode of action this selection device is the same as that according to FIG. 5a, so that a description can be omitted.

The selection device according to FIG. 5 ° selects the maximum pressure from several (four) input pressures. The same reference numerals are used for the parts corresponding to FIG. 5a. The only difference to the selection device according to Fig, 5a is that in this case the check valves all pass in the opposite direction as the non-return valves according to Fig. 5a, If the pressures k in the lines $ all lower than or in the conduits 52, the common Exit 56, the valve bodies 52 remain pressed against the seats 53 in a sealing manner. If, however, a pressure occurs in only one of the lines 5 ^ which is higher than the pressure in the common outlet 56, the check valve connected to the mentioned line 5 ^ immediately establishes the connection between this line 5 ^ and the relevant line 55 free, because the valve body 52 in question is pressed downwards . In the common output 56, the jiaximal pressure of the various input pressures is then established. The leakage throttles 58 now ensure that when the pressure drops in ύβη lines 5 ^ the pressure in the

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common output 56 can slowly follow these depressions, by licking away in the direction of the common output 56 to the lines 5 ^. In the steady state, the pressure in the common outlet 56 does not differ significantly from the highest of the inlet pressures prevailing in the lines ^ k.

The selection devices described offer the advantages of a simple construction, the compactness and a reliable mode of operation. An extension to for example eight or nine inputs, which is desirable for an eight-cylinder hot gas piston engine, for example, is possible in a simple manner while retaining the advantages.

In addition to the one shown, there are of course all kinds of other embodiments of the selection devices possible.

In FIG. 6, reference numeral 60 denotes a housing in which a membrane 61 is accommodated, which is fastened to the housing and which separates a chamber 62 from a chamber 63. The chamber 62 is via an inlet 6 h 63 _t the chamber via an inlet 65 accessible.

The membrane 61 carries a magnetic element 66 ^{which faces a core 67 made of} soft iron with an induction coil 68 and arranged in the interior of the chamber 63. The electrical conductors 69, which are led through the wall of the housing 60 to the outside, are connected to the induction coil.

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If the magnetic element 66 moves in the direction of the core 67 »an electrical signal is generated in the induction coil 68, the magnitude of which is proportional to the distance over which the magnetic element 66 moves»

The inlets 6k and 65, the two different pressures may be supplied, which are produced for example by the selection device 15 and the common fuel supply line 5 of Figure 1, the present apparatus is effective as a pressure difference sensor 17th

If the pressure difference changes, the electrical signal of the induction coil 68 changes proportionally this is because the pressure difference across the membrane 61 changes and this membrane moves towards the core 67 or from it moved away.

7 shows a housing 70 with a partition wall 71 which divides the space in the housing into two sub-spaces. One subspace consists of the two chambers 72 and 73 which are separated from one another by a membrane 7k , while the other subspace consists of two chambers 75 and 76 separated from one another by a membrane 77.

The membranes 7 and 77 are on the one hand on the housing 70 attached and on the other hand connected to a common rod 78 which can be moved back and forth in the axial direction and via an opening 79 through the partition 71 is led.

The chambers 72, 73, 75 and 76 are each with

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an inlet 80, 81, 82 and 83, respectively. The rod 78 carries at one end a magnetic element 84, the a core 85 arranged inside the chamber 72 Soft iron is facing with an induction coil 86 to which electrical conductors 87 are connected, which through the Wall of the housing 70 are guided to the outside. Is moving the rod 78 again in the direction of the structure of core 85 and induction coil 86, an electrical signal is induced in the coil 86 here too, the magnitude of which is proportional is the distance that the rod 87 has moved.

By now the chambers 72 and 76, the pressure difference Δ P-i is supplied to the flow of a combustion air represents, and the chambers 73 and 75 represents the pressure difference that represents a fuel flow, a state of equilibrium arises, in which the rod 78 at a correspond to the electrical signal of the induction coil 86 a certain Takes position. The pressure differences on the rod as a result of the pressure differences at the membranes 74 and 77 The forces exerted then form an equilibrium with those due to the tension forces in the membranes on the aforementioned Forces exerted by rod.

If the pressure difference Ap ~ t changes , the equilibrium of forces is disturbed, and the rod 78 assumes a new position, a new equilibrium of forces being achieved. The induction coil 86 then supplies a new electrical signal corresponding to the new position,

With the signal supplied by the induction coil 86, the control mechanism 20 can in the common

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Combustion air supply line 10 according to FIG. 2 or h can be controlled directly.

The same medium is present in chambers 73 and 75. Any leakage of medium from the higher to the lower pressure chamber does not lead to any complications, while the pressure difference between the chambers increases little licking is hardly affected.

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Claims (1)

PATENT CLAIMS j The multi-cylinder hot-gas piston engine, is provided in which each cylinder with a heater can be supplied _for the derived from an associated burner apparatus heat, with a fuel supply and a combustion air supply connected to each burner apparatus wherein the fuel supplies with their side facing away from the associated burner device ends to connect a common fuel supply line, in which a pressure control device maintains a constant pressure during operation, and the combustion air supplies are connected with their ends facing away from the associated burner device to a common combustion air supply line, wherein each heater is provided with a temperature-sensitive element that has a fuel control mechanism actuated the fuel supply of the associated burner device for regulating the fuel flow to the mentioned device, wherein in each fuel supply, downstream g There is a flow resistance element in front of the fuel control mechanism, at which there is a pressure difference proportional to the speed of the fuel flow through the relevant supply, the amount of combustion air to be supplied being controlled as a function of the amount of fuel supplied, characterized in that a selection device for the automatic selection of the maximum or minimum fuel pressure out of several 209839/0749 Fuel inlet pressures are present and that the Output sides of the flow resistance elements are connected to as many inputs of the selection device, wherein the pressure difference between the constant fuel pressure in the common fuel supply line and the selected maximum or minimum fuel pressure is influenced by a control device that controls a combustion air control mechanism in the common combustion air supply line operated, 2, multi-cylinder hot gas piston engine according to claim 1, characterized in that an auxiliary fuel line is present, one end of which extends to the common Fuel supply line connects, where & ir Auxiliary line also a flow resistance element is located, at the inlet side of which the constant fuel? ^ - There is pressure and the output side also has an input the selection device is connected, which selection device selects the minimum fuel pressure, further being in the auxiliary fuel line, downstream seen after the flow resistance element, a fixed throttle is added, which is chosen such that below a certain minimum fuel flow through the Fuel feeds on the outlet side of the flow resistance element the also constant pressure prevailing in the auxiliary fuel line is lower than the pressures, which in this case prevail on the outlet sides of the flow resistance elements in the fuel feeds. 209839/0749 J * 3 »Multi-cylinder hot gas piston engine according to claim 1 or 2, in which there is a further flow resistance element in each combustion air supply, at which there is a pressure difference proportional to the speed of the combustion air flow due to the relevant supply during operation, characterized in that a further selection device for the automatic selection of the maximum combustion air pressure from several combustion air inlet pressures is available, and that the outlet sides of the further flow resistance elements are connected to the same number of inputs of the further selection device, the pressure difference between the combustion air pressure on the inlet side of the further flow resistance elements and the selected maximum combustion air pressure the control element in the opposite sense as the fuel pressure difference influences. k, multi-cylinder hot gas piston engine according to claim 1, 2 or 3 »characterized in that the selection device or the further selection device consists of a number of non-return valves which are only permeable in one direction and which are arranged next to one another with the same directional flow directions as one another valves form for the same number of inlet pressures with its one side inputs and to join with its other side to a common output, wherein the bond and Ausgangeseite each valve are each by means of a leakage inductor with each other in open communication. 209839/0749 5 »Multi-cylinder hot gas piston engine according to claim h _t characterized in that each non-return valve has a foil element as the valve body, which can cooperate in a sealing manner with a seat, and which pole element is provided with a bore as a leakage throttle. 209839/0749