US3822550A

US3822550A - Multicylinder thermodynamic reciprocating machine in which the fuel supply to burner devices is controlled by means of temperature-sensitive elements

Info

Publication number: US3822550A
Application number: US00374904A
Authority: US
Inventors: K Brandenburg; J Kuhlmorgen
Original assignee: US Philips Corp
Current assignee: US Philips Corp
Priority date: 1971-03-18
Filing date: 1973-06-29
Publication date: 1974-07-09
Anticipated expiration: 1991-07-09

Abstract

A multicylinder thermodynamic reciprocating machine in which a fuel supply and a supply for air of combustion communicate with each burner device, in which the ends of the fuel supplies remote from the associated burner device communicate with a common fuel supply duct in which a pressure control device during operation maintains a constant pressure and the ends of the supplies for air of combustion remote from the associated burner device communicate with a common supply duct for air of combustion, in which, taken in the direction of flow, a flow restricting element and a fuel control mechanism are incorporated in each fuel supply, in which a selecting device for the automatic selection of the maximum or minimum fuel pressure from several fuel inlet pressures is present and the outlet sides of the flow restricting elements communicate with the same number of inlets of the selecting device, the pressure differential between the constant fuel pressure in the common fuel supply duct and the selected maximum or minimum fuel pressure influencing a control member which actuates a control mechanism for air of combustion in the common supply duct for air of combustion.

Description

United States Patent 1191 Brandenburg et a1.

[ MULTICYLINDER THERMODYNAMIC RECIPROCATING MACHINE IN WHICH THE FUEL SUPPLY TO BURNER DEVICES IS CONTROLLED BY MEANS OF TEMPERATURE-SENSITIVE ELEMENTS [75] Inventors: Klaus Brandenburg, 1

Kirchen-Wehbach; Joachim Kuhlmorgen, Aachen, both of Germany [73] Assignee: U.S. Philips Corporation, New

York, NY.

[22] Filed: June 29, 1973 [21] App]. No.: 374,904 I Related US. Application Data [63] Continuation of Ser. No. 234,074, March 13,1972.

[30] Foreign Application Priority Data Mar. I8, 1971 Netherlands 713610 [52] US. Cl. [50/524,69/525 [51] Int. Cl. F03g 7/06 [58] Field of Search 60/23, 24, 33, 59

[56] References Cited UNITED STATES PATENTS 1,618,594 2/1927 Koenig 60/24 2,664,698 1/1954 Van de Poll et a1 60/24 3,600,886 8/1971 Jaspers et a1. 60/24 3,699,770 10/1972 Bennethom 60/24 11] 3,822,550 [45] Ju1y9,197

FQREIGN PATENTS OR APPLICATIONS 895,869 5/1962 Great Britain 150/24 Primary Examiner-Wendell E. Burns Attorney, Agent, or Firm-Frank: R. Trifari [57] ABSCT A multicylinder thermodynamic reciprocating machine in which a fuel supply and a supply for air of combustion communicate with each burner device, in which the ends of the fuel supplies remote from the associated burner device communicate with a common fuel supply duct in which a pressure control device during operation maintains a constant pressure and the ends of the supplies for air of combustion remote from the associated burner device communicate with a common supply duct for air of combustion, in which, taken in the direction of flow, a flow restricting element and a fuel control mechanism are incorporated in each fuel supply, in which a selecting device for the automatic selection of the maximum or minimum fuel pressure from several fuel inlet pressures is present and the outlet sides of the flow restricting elements communicate with the same number of inlets of the selecting device, the pressure differential between the constant fuel pressure in the common fuel supply duct and the selected maximum or minimum fuel pressure influencing a control member which actuates a control mechanism for air of combustion in the common supply duct for air of combustion.

11 Claims, 9 Drawing Figures PATENTED- 91914 3.822.550

SHEE! Q [If 6 MULTICYLINDER THERMODYNAMIC RECIPROCATING MACHINE IN WHICH THE FUEL SUPPLY TO BURNER DEVICES llS CONTROLLED BY MEANS OF TEMPERATURESENSITIVE ELEMENTS This is a continuation of application Ser. No. 234,074, filed Mar. 13, 1972.

The invention relates to a multicylinder thermodynamic reciprocating machine. Each cylinder comprises a heater to which thermal energy from an associated burner device can be supplied; a fuel supply and a supply for air of combustion communicate with each burner device, and the ends of the fuel supplies remote from associated burner device communicate with a common fuel supply duct in which a pressure control device maintains a constant fuel pressure during operation. The ends of the supplies for air of combustion remote from the associated burner device communicate with a common supply duct for air of combustion. Each heater comprises a temperature-sensitive element which actuates a fuel control mechanism in the fuel supply of the associated burner device for controlling the fuel flow to the said device. Each fuel supply, taken in the direction of flow, comprises before the fuel control mechanism. A flow-restricting element across which during operation, a pressure differential prevails which is proportional to the rate of the flow of fuel through the relevant supply. The quantity of air of combustion to be supplied is controlled in accordance with the supplied quantity of fuel.

A thermodynamic reciprocating machine of the type of the present invention, is known from British Pat. specification No. 895,869, which describes for a monocylinder thermodynamic reciprocating machine, a control of the quantity of air of combustion to be supplied to the burner device in accordance with the quantity of fuel to be supplied. In this case, pressure difference gauges are arranged in the supplies for fuel and air of combustion which gauges actuate, independently of each other in opposite senses, the same member of a hydraulic system which controls the position of a throttle valve in the supply for air of combustion in accordance with the fuel flow in the fuel supply. This known construction for controlling the supplies for fuel and air of combustion to the burner device of a monocylinder thermodynamic reciprocating machine exhibits a few drawbacks which make it less attractive for use also in multicylinder thermodynamic reciprocating machines. First'of all, very high requirements must be imposed upon the control mechanism in the fuel duct. As a matter of fact, the passage should be adjustable accurately and in a reproduceable manner over a large fuel flow range. When these requirements are not satisfied, this will give rise to all kinds of difficulties, notably in the case of small fuel flows, such as extinguishing of the burner, instability of the temperature control circuit, incomplete combustion of the air-fuel mixture with dirty exhaust gases which are detrimental to health, all this therefore as a result of the wrong dosing of fuel. For the pressure difference gauge in the fuel supply duct, a great ratio for the largest to the smallest fuel flow means that said gauge must be capable of measuring pressure differences accurately and in a reproduceable manner within a very large measuring range. Actually, according to Bernouillis theorem, the produced pressure differential is proportional to the square of the rate of flow.

The use in multicylinder thermodynamic reciprocating machines of such a solution is furthermore even less attractive, since in that case the number of control systems required is the same as the number of cylinders present. The air-fuel control in its totality then consists of a very complicated assembly built up from a very large number of comparatively expensive components.

It is the object of the present invention to provide an air-fuel control system for multicylinder thermodynamic machines which combines simplicity in construction, including a comparatively small number of cheap components, with a reliable operation.

In order to realize this objective, the multicylinder thermodynamic reciprocating machine according to the invention is characterized in that it includes a selecting device for the automatic selection of the maximum or minimum fuel pressure from several fuel inlet pressures. The outlet sides of the flow restricting elements communicate with an equal number of inlets of the selecting device, the pressure differential between the constant fuel pressure in the common fuel supply duct and the selected maximum or minimum fuel pressure influencing a control member which actuates a control mechanism for air of combustion in the common supply duct for air of combustion.

By using the selecting device, which may have a very compact and simple construction, a pressure difference gauge and throttle valve need not be present in each supply for air of combustion. This is in deviation from the already mentioned known control system, and as a result of this, a considerable saving of components is obtained. An evenmore important saving is obtained in this case, in that it is not necessary for each burner device to separately compare the flows of air and fuel to the burner device and to match them mutually via an associated control system such as, for example, the hydraulic system described in the said lBritish Pat. specification No. 895,869. In this case only one control system is necessary with which the air flow through the common supply duct for air of combustion is adapted to the maximum fuel flow from the various fuel flows which flow through the fuel supplies of the burner devices by choosing a selecting device which selects the minimum fuel pressure.

By the resulting great saving of comparatively expensive components with the introduction of a simple selecting device, a multicylinder thermodynamic reciprocating machine having an attractive, simple and cheap air-fuel control is obtained. Irrespective of the number of cylinders, only one fuel pressure difference sensor is necessary to which the fuel pressure difference signal is supplied.

Since furthermore the flows of fuel to the various .bumer devices are directly compared mutually via the ln multicylinder thermodynamic machines in which the fuel flow of liquid fuel may vary per burner device from, for example, 0.02 gram/sec. to 1.2 gram/sec (ratio 1 60), this means a ratio for the minimum to maximum pressure difference, produced preferably with one or more plates, of l 3600. Since this ratio and hence also the required measuring range is very large, the measuring instrument becomes complicated and expensive. It is also substantially impracticable to realize for small fuel flows of a few hundredths of grams per second a turbulent and hence temperatureindependent flow in the plates.

A sufficiently reliable air-fuel control in the case of small fuel flows then is not possible and involves the danger of too small a ratio-fuel in the case of said small fuel flows, as a result of which incomplete combustion and dirty exhaust gases occur.

In order to avoid this drawback, a favourable embodiment of the multicylinder thermodynamic reciprocating machine according to the invention comprises an auxiliary duct for fuel which communicates with one end with the common fuel supply duct. In this auxiliary duct a flow-restricting element is also incorporated on the inlet side of which the constant fuel pressure prevails. The outlet side of this duct also communicates with an inlet of the selecting device, which selects the minimum fuel pressure. The fuel auxiliary duct furthermore incorporates, taken in the direction of flow after the flow-restricting element, a fixed restriction which is chosen to be so that below a given minimum fuel flow to the fuel supplies, the pressure prevailing on the outlet side of the flow restricting element in the fuel auxiliary duct, which pressure is likewise constant, is lower than the pressures which prevail in that case on the outlet sides of the flow restricting elements in the fuel supplies.

it is achieved in this manner that below a given minimum fuel flow, irrespective of the value which the fuel flow then assumes, a constant value is obtained for the fuel pressure differential influencing the control member. The supplied quantity of air of combustion then is also constant and sufficiently large for any fuel flow below the said minimum. Therefore, complete combustion with small fuel flows is ensured in all cases.

In certain circumstances it may occur that the air flow originating from the common supply duct for air of combustion distributes insufficiently uniformly between the various supplies for air of combustion, for example, as a result of differences in counter pressures acting upon the supplies from the associated burner devices or as a result of different values of flow restricting elements of the said supplies. The danger then exists that a quantity of air of combustion which is insufficient to ensure complete combustion of the supplied quantity of fuel is supplied to a burner device. This would result again in dirty exhaust gases which are detrimental to health. For that reason it may sometimes be desirable to have more certainty about the quantities of air flowing through the supplies for air of combustion, notably about the smallest flow of air of combustion.

For that purpose, a favourable embodiment of a multicylinder thermodynamic reciprocating machine in which (a) has in each supply for air of combustion a further flow-restricting element, across which during operation, a pressure differential prevails which is proportional to the rate of the flow of air of combustion through the relevant supply, and (b) a further selecting device for the automatic selection of the maximum pressure of air of combustion from several inlet pressures of air of combustion. The outlet sides of the further flow-restricting elements communicate with the same number of inlets of the further selecting device, the pressure difierential between the pressure of air of combustion on the inlet side of the further flow restricting elements and the selected maximum pressure of air of combustion influences the control member in the opposite sense to the fuel pressure differential.

Since the further selecting device selects the maximum pressure of the pressures of air of combustion prevailing on the outlet sides of the further flow restricting elements, said device follows the smallest flow of air of combustion of all the flows flowing through the various supplies of air of combustion.

By suitable adjustment of the control system, it is achieved that said minimum flow of air of combustion always is sufficiently large to ensure complete combustion of the maximum fuel flow from the various fuel flows preceding to the various burner devices.

In the present case again, only one general control system is necessary instead of an associated control separately for each cylinder and burner device, respectively. As further flow restricting elements are to be considered again the above-mentioned simple measuring plates but if desirable, for example, Pitot tubes or Venturis may also be used. Just as the selecting device, the further selection device may also be of a simple and compact structure.

In a favourable embodiment of the multicylinder thermodynamic reciprocating machine according to the invention, the selecting device and the further selecting device, respectively, consist of a number of check valves which pass only in one direction and which are arranged beside each other with their directions of passing oriented mutually in the same direction. The valves communicate with their one side inlets for an equal number of inlet pressures and communicating with their other side with a common outlet, the inlet and outlet sides of each valve being always in open communication with each other by means of a leak restriction.

A further favorable embodiment of the multicylinder thermodynamic reciprocating machine according to the invention is characterized in that each check valve comprises a valve body, a foil element which can cooperate in a sealing manner with a seat, said foil element comprising an aperture as a leak restriction.

In order that the invention may readily be carried into effect, a few embodiments thereof will now be de scribed in greater detail, by way of example, with reference to the accompanying drawings which are diagrammatic and not drawn to scale.

BRIEF DESCRIPTION OF THE DRAWINGS machine inwhich, in addition to the selecting device for the maximum fuel flow, a further selecting device is present; the minimum flow of air of combustion is selected from the four flows of air of combustion flowing to the four burner devices, the minimum flow of air of 5 combustion is compared with the maximum fuel flow and the overall flow of air of combustion being derived therefrom.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now to FIG. 1, reference numeral 1 denotes a 4-cylinder thermodynamic reciprocating machine having with each cylinder a heater (not shown) and an associated burner device 2. A fuel supply 3 and a supply 4 for air of combustion communicate with each burner device 2. All the fuel supplies 3 communi cate with a common fuel supply duct 5 in which a fuel pump 6 is incorporated with which fuel can be supplied to the fuel supplies 3 from a fuel container 7.

Communicating with the common fuel supply duct 5 is a fuel return duct 8 in which a pressure control valve 9 is incorporated. During operation this valve maintains a constant pressure in the common fuel supply duct 5 and hence also on the inlet sides of the fuel supplies 3 communicating therewith.

All the supplies 4 for air of combustion communicate with a common supply duct 10 for air of combustion.

- Each of the heaters which are not shown in detail comprise a thermocouple 11 as a temperature sensitive element with which during operation the heater temperature is determined. The electric signals supplied by the termocouple 11 are individually amplified in a central amplifier unit 12. Each amplifiedsignal determines the position of an electromagnetic valve 13 as a fuel control mechanism in the fuel supply 3 of the burner device 2 associated with the relevant heater.

Taken in the direction of flow before the electromagnetic valve 13, a flow restricting element 14 is present in each fuel supply 3 across which during operation a pressure differential prevails which is proportional to the rate of the fuel flow through the relevant supply. The flow restricting elements may be of a simple construction, for example, as the known thin plates comprising an aperture. If desirable, Pitot tubes or Venturis or the like may also be used.

A selecting device 15 is present which has four inlets on which the four outlet sides of the flow restricting elements l4 communicate through ducts 16. The selecting device 15 selects the minimum pressure of the four pressures prevailing on the outlet sides of the flow restricting elements 14; this minimum pressure is supplied to a pressure difference sensor 17 as a control member. The constant pressure which prevails on the inlet side of the flow restricting elements 14 is also supplied directly to the pressure difference sensor 17 via a duct l8.

In the pressure difference sensor 17, the difference in the two pressures supplied to it is converted into an electric signal which is amplified in an amplifier 19. The position of an electromagnetic valve 20 as a control mechanism for air of combustion in the common supply duct id for air of combustion is controlled with the amplified signal. Pressure difference sensor 17 may be constructed, for example, as shown in FIG. 6 to be described hereinafter.

The operation of the air-fuel control system is as follows. During operation, the fuel. pump 6 pumps fuel from the fuel container 7 to the fuel supplies 3, while in a manner not shovim, air of combustion is supplied to the common supply duct It) for air of combustion, which air is distributed between the four supplies 4 for air of combustion. As a result of the control action of the pressure control valve 9, a constant pressure prevails on the inlet sides of the flow restricting elements 14. So a constant pressure signal is supplied to pressure difference sensor l7 via duct 1%.

The fuel flow flowing to a burner device 2 through the relevant fuel supply 3 depends upon the temperature of the associated heater. When the temperature of the heater decreases, for example, because more power is consumed from the relevant cylinder, the relevant thermocouple it ensures that the electromagnetic valve 13 in question is opened further and more fuel can flow to the burner device. Conversely, when the temperature of the heater increases, the thermocouple ll. ensures that the valve 13 is further closed and less fuel is passed to the burner device.

Since the pressure on the inlet. sides of the flow restricting elements M is constant and since the pressure drop across such an element increases when the fuel flow through said element increases, this means that the lowest of the pressures prevailing on the outlet sides of the flow restricting elements 14 prevails in that fuel supply 3 through which the greatest fuel flow passes.

As already described, the selecting device l5 now selects said lowest fuel pressure from the four pressure signals supplied to it via ducts 17. The pressure differential which influences the pressure difference sensor 17 and is constituted by the difi'erence between the constant pressure on the inlet side of the flow restricting elements M and the minimum pressure selected from the four pressures prevailing on the outlet sides of the said elements, therefore represents the maximum fuel flow of the various flows flowing through the four fuel supplies 3 to the four burner devices 2.

On the basis of this pressure differential representing the maximum fuel flow, the overall quantity of air of combustion supplied collectively to the four burner devices is controlled in that the electrical signal derived from the pressure differential, after amplification in the amplifier 19, controls the position of the electromagnetic valve 20.

When the air-fuel control system is adjusted so that the overall quantity of air of combustion supplied per unit of time is at least equal to four times the quantity of air of combustion necessary to ensure complete combustion of the maximum fuel flow, then the complete combustion of the other three fuel flows which as a matter of fact are smaller than the selected fuel flow, is practically always ensured.

The whole control system of the present 4-cylinder thermodynamic reciprocating machine is very simple in construction and consists of a very small number of components. In what manner the selecting device 115 may be constructed will be described in greater detail with reference to FIG. 5.

In practice, air of combustion is usually supplied to the common supply duct for air of combustion by means of a fan which is rigidly coupled to a shaft of the machine. Dependent upon the number of revolutions of the engine, the efficiency of the fan is then varied. In the case in which the fan is coupled to a shaft of a multicylinder thermodynamic reciprocating machine as that shown in FIG. 1, it should be ensured that in the case of a variable supply of supply duct for air of combustion, the quantity of air of combustion passed to the supplies 4 for air of combustion remains matched to the maximum fuel flow selected from the various flows through the fuel supplies 3.

A solution for this is shown in FIG. 2. The air-fuel control system shown in FIG. 2 in general is equal to that shown in FIG. 1, so that the same reference numerals are used for corresponding components. In the present case, a fan 21 is present with which air combustion is supplied to the common supply duct 6 for air of combustion. The shaft of fan 21, is coupled to a shaft of. the machine which is not shown in the drawing. An element 22 restricting the flow of air of combustion is present in the common supply duct 10 for air of combustion and supplies a pressure differential which is proportional to the flow of air of combustion through said duct, which pressure differential is supplied to a pressure differences sensor 23. The pressure differential supplied to said sensor is converted in it into an electric signal which influences an electric comparison element 24 as a control member in a sense opposite to the electric signal originating from the pressure difference sensor 17.

Comparison element 24 controls the position of the electromagnetic valve 20' on the basis of the difference between the two electric signals supplied to said element. When the number of revolutions of the fan increases and hence the quantity of air which passes the valve 20' increases, the value of the pressure differential signal supplied by element 22 restricting the flow of air of combustion also increases and hence the electric signal derived therefrom. Comparison element 24 ensures that the value 20 is closed to such an extent that the original quantity of air of combustion again passes valve 20. When the number of revolution of the fan decreases and hence also the quantity of air which passes the valve 20, the element 24 ensures that the valve 20' is opened to a greater extent so that the original air flow is maintained.

Element 22 restricting the flow of air of combustion may be, for example, a Pitot tube or a Venturi, may be constructed from one or more plates provided with apertures, but it may also be constructed as an anemometer. When an electric anemometer is used, the electric signal which is derived herefrom and is proportional to the flow of air of combustion can be directly supplied to the comparison element 24. The characteristics of said, anemometer and those of the pressure difference sensors 17 should then be matched mutually.

The pressure difference sensors 17' and 23 may be constructed as is shown by way of example in FIG. 6 to be described hereinafter. A combined unit, such as the one shown in FIG. 7 to be described hereinafter, may be used for the two pressure sensors together with the comparison element 24.

In the air-fuel control systems shown in FIGS. l and 2, the overall flow of air of combustion is matched to the maximum fuel flow of the various flows through the fuel supplies 3 in that the selecting device 15 selects the minimum pressure from the various pressures prevailing on the outlet sides of the flow resisting elements M.

In the case of small fuel flows through the fuel supplies 3, the pressure differentials between the inlet and outlet sides of the flow restricting elements M are small. Small pressure difference signals are unfavourable for an accurate air-fuel control. In addition it is substantially impossible in the preferably used measuring plates to cause the flow through the plates to be turbulent and hence temperature-independent in the case of small fuel flows. All this results in an inaccurate air-fuel control in the case of small fuel flows, which results in too low air-fuel ratios with said small fuel flows and consequently in incomplete combustion with dirty exhaust gases.

This problem is no longer present in the airfuel control system shown in FIG. 3 which in general is equal to that shown in FIG. I and in which therefore the same reference numerals are used for corresponding compo nents.

The control system shown in FIG. 3 differs from that shown in FIG. 1 in that in the present case a fuel auxiliary duct 30 is present which communicates at one end with the common fuel supply duct 5" and at its other end opens into the fuel container 7. A flow restricting element 14" the outlet side of which also communicates, via a duct 16', with an extra, fifth, inlet of the selecting device 15 which, as stated selects the minimum pressure, is also present in the fuel auxiliary duct 30, as in the fuel supplies 3". Furthermore, a fixed restriction 31 is incorporated in the fuel auxiliary duct 30.

Since during operation a constant pressure prevails on the inlet side of the fuel auxiliary duct 30, a constant pressure will prevail also in said duct as a result of the presence of the fifth restriction 31 on the outlet side of the flow restricting element 14" and a constant fuel flow will flow through fuel auxiliary duct 30 to fuel container 7.

Fixed restriction 3i and hence the fuel flow flowing away through the fuel auxiliary duct 30 is now chosen to be so that said fuel flow corresponds to a certain minimum value of the fuel flows through the various fuel supplies 3". Above said certain minimum value, all the fuel flows through the fuel supplies are greater than the constant fuel flow through the fuel auxiliary duct 30. In that case the pressures on the outlet sides of the flow restricting element 1 in the fuel supplies 3" are all lower than the constant pressure on the outlet side of the flow restricting element M in the fuel auxiliary duct 30. Since the selecting device 15 selects the smallest from the five supplied pressure signals, said minimum pressure signal is always one of the four pressure signals originating from the fuel supplies 3". The fuel auxiliary duct 30 is then passive relative to the airfuel control.

If all the fuel flows through the fuel supplies 3' however, fall below the minimum value which corresponds to the constant fuel flow through the fuel auxiliary duct 30, then, since the last-mentioned flow then is the greatest, the pressure on the outlet side of the flow restricting element M" in the fuel auxiliary duct 30 is lower than all the pressures prevailing on the outlet sides of the flow restricting element 14" in the fuel supplies 3". The selecting device 15" then selects as a minimum pressure the pressure signal originating from the fuel auxiliary duct 30. Since this signal is constant owing tothe constant pressure on the outlet side of the flow restricting element 14" in said duct, a constant signal is supplied to the pressure difference sensor 17''. This means that the overall quantity of air of combustion supplied per unit time then remains constant since actually the position of the electromagnetic valve 20 no longer varies.

In this manner it is achieved that below a certain minimum value for the fuel flows through the fuel flows through the fuel supplies 3", the overall flows of air of combustion remains constant irrespective of the value which the said fuel flows then assume. If, when the fuel flows through the fuel supplies 3" have values which are equal to the minimum value, the overall flow of air of combustion is sufficiently large to obtain complete combustion of the said flows, then said overall air flow is certainly sufficiently large for complete combustion of fuel flows through the fuel supplies below said minimum value. Complete combustion is therefore substantially always ensured while unreliable measurement of small fuel flows through the fuel supplies 3" is no longer necessary and is avoided. g

In the air-fuel control systems shown in FIGS. 1 to 3, the overall flow of air of combustion is always controlled in accordance with the maximum fuel flow through one of thefuel supplies 3" and the maximum fuel below flow of the variable flows through the fuel supplies 3", respectively, and the constant flo through the fuel auxiliary duct 30. i

The starting idea is that the overall flow of air of combustion through the common supply duct 10" for air of combustion distributes uniformly between the four supplies 4" for air of combustion. In circumstances, however, it may occur that this latter is not always the case to a sufficient extent. The cause hereof may be the mutually different flow restriction values of the supplies 4" for air of combustion. It is also possible that from the burner devices 2 mutually different counter pressures influence the supplies for air of combustion. The result of all this may be that too little air of com bustion is supplied to a supply for air of combustion to ensure complete combustion of the fuel supplied to the corresponding fuel supply as a result of which dirty exhaust gases of the relevant burner device are obtained.

In the air-fuel control system shown in FIG. 4 this drawback is avoided. For this system, the same reference numerals are used for components corresponding to the system shown in FIG. 3. The present system differs from that shown in FIG. 3 in the following points. a

for air of combustion.

The four outlet-sides of the further flow restricting elements 40 are connected to the same number of inlets of further selecting device 41 via ducts d2.

The common pressure prevailing on the inlet sides of the further flow restricting elements 40, namely the pressure in the common supply duct 10a for air of combustion as well as the maximum: pressure selected by the further selecting device 41 from the various pressures prevailing on the outlet sides of the said elements, are individually supplied to a pressure difference sensor 43. The difference between the two pressures is con-- verted in said sensor into an electric signal which influences an electric comparison element 44- in a sense opposite to the electric signal originating from the pressure difference sensor 170. Comparison element 44 operates the electromagnetic valve 2% on the basis of the difference between the electric signals supplied to said element.

Pressure difference sensor 43 has a characteristic which is equal to that of the pressure difference sensor 17a. Both pressure difference sensors may again be constructed; for example, as shown in FIG. 6 or may be constructed as one unit together with the comparison element 44, for example, in the manner shown in FIG. 7.

Since the further selecting device 41 selects the maximum pressure from the various pressures prevailing on the outlet sides of the further flow restricting elements 40, this means that the selected maximum pressure originates from that supply 4a for air of combustion through which the smallest flow of air of combustion passes. As a matter of fact, the pressure drop across the further flow restricting element 40 present in said supply for air of combustion is smallest there, while the same common pressure prevails on the inlet sides of all the further flow restricting elements 40. The pressure differential supplied to pressure difference sensor 43 therefore represents the smallest flow of air of combustion of all the flows passing through the supplies 4a for air of combustion. All this means that the smallest flow of air of combustion selected from all the flows passing through the various supplies 4a for air of combustion is controlled in accordance with the maximum fuel flow selected by means of the selecting device 15a from the variable fuel flows through the various fuel supplies 3a and the constant fuel flow through the fuel auxiliary duct 30.

When the control systemis adjusted so that the selected minimum flow of air of combustion through a supply 4a for air of combustion is sufiiciently large to be able to completely burn the selected maximum fuel flow through a fuel supply 3a and through the fuel auxiliary duct 30a, respectively, it is automatically ensured in all circumstances that all the fuel flows through the fuel supplies 3a are completely burnt by the flows of air of combustion through the corresponding supplies 4a of air of combustion. The possible cases then are that the minimum flow of air of combustion or a larger flow of air of combustion is supplied to the maximum fuel flow or a smaller fuel flow.

The operation of the present control system is further the same as that shown in FIG. 3 so that further description may be omitted. Of course, the control system in the present case may be constructed, if desirable, without a fuel auxiliary duct 30a. In addition to the further flow restricting elements 40, only one further selecting device 41 is necessary which can be of a compact and simple construction again. A separate control for each burner device separately is thus prevented so that the overall control system remains constructed from a comparatively small number of cheap components.

As in the control system shown in FIG. 2, air of combustion can be supplied to the common supply duct a for air of combustion in this case also by means of a fan which is coupled directly to a shaft of the machine and the efficiency of which thus varies when the number of revolutions varies. It is to be noted that in that case, and not only in that case, it is not always necessary to maintain a constant pressure in the common supply duct 10a for air of combustion and hence at the inlet sides of the further flow restricting elements 40. For example, when the number of revolutions of the machine and thus the number of revolutions of the fan increases, as a result of which the overall supplied quantity of air of combustion and the pressure on the inlet sides of the further flow restricting elements 40 also increases, then the pressure on the outlet sides of the said elements increases to the same extent. The pressure differential supplied to the pressure difference sensor 42 then remains unvaried so that the only practical result is that a greater excess of air of combustion is supplied to the burner devices 2a. This need by no means be disturbing but may in certain circumstances even be advantageous. It should be ensured only in the first instance that the selected minimum flow of air of combustion is chosen to be sufficiently large relative to the selected maximum fuel flow.

In the control system shown in FIGS. 1 to 4, pressure differentials are always converted into electric signals. It is of course also possible to supply the fuel pressure differences directly to the control mechanism in the common supply duct for air of combustion, which control mechanism may then be constructed as a hydraulically controlled valve. It is also possible to compare the fuel pressure differential and the pressure differential of air of combustion directly with each other, for example, in a hydraulic comparison element and to cause the difference between the two pressure difference signals to operate the control mechanism in the common supply duct for air of combustion constructed as a hydraulically controlled valve, for example, in a manner analogous to that described in British Pat. specification No. 895,869 for the direct hydraulic comparison of the flows of fuel and air of combustion to the burner device of a monocylinder thermodynamic reciprocating machine. In contrast with what is the case in said known monocylinder thermodynamic reciprocating machine, only one comparison element is necessary in the present multicylinder thermodynamic reciprocating machine, irrespective of the number of cylinders.

Furthermore, a four-cylinder thermodynamic reciprocating-machine is always shown in the control systems shown .in FIGS. 1 to 4. Of course, the systems shown in the said Figures may equally readily be applied to multicylinder thermodynamic reciprocating machines having a different number of cylinders while maintaining the advantages. Extension to, for example, 8-cylinder thermodynamic reciprocating machines only means a comparatively small increase of the overall number of required components since only one selecting device and further selecting device, respectively, will always be sufficient.

How such a selecting device and further selecting device, respectively, may be constructed is shown in FIG. 5a, 5b and 50. FIGS. 5a and 5b show selecting devices for the automatic selection of the minimum pressure from four inlet pressure signals, while FIG. 5c shows a selecting device which automatically selects the maximum pressure from four inlet pressures. Reference numeral in FIG. 5a denotes a housing in which four check valves 51 passing in the same direction are arranged beside each other. Each check valve 51 comprises a spherical valve body 52 which can cooperate in a sealing manner with a valve seating 53. Ducts 54 passed through the wall of the housing 50 constitute the inlet sides of the valves. Outlet sides of the valves constituted by ducts 55 communicate with a common outlet 56 which is passed to the outside through the wall of the housing. The inlet side 54 and the outlet side 55 each valve 51 are in open communication with each other via a duct 57 in which a leak restriction is incorporated. The operation of this selection device is as follows.

When the pressures in'the ducts 54, so on the inlet sides of the valves 51, are all higher than in the ducts 55 and the common outlet 56, respectively, the valve bodies 52 are forced against the valve seatings 53 in a sealing manner. When, however, in only one of the ducts 54 a pressure occurs which is lower than the pressure in the common outlet 56, the check valve 51 which communicates with the said duct 54 immediately releases the communication between said duct 54 and the relevant duct 55 in that the valve body 52 in question moves away from its seating 53 (upwards) under the influence of the occurring pressure differential. The lower pressure which prevails in the said duct 5 then adjusts in the common outlet 56, while the remaining check valves 51 remain closed. In this manner the minimum pressure selected from the various inlet pressures prevails in the common outlet 56.

The leak restrictions 58 ensure that when the pressure in the ducts 54 increases, the pressure in the common outlet 56 can slowly follow said increases in pressure so that in the stationary condition the pressure in the outlet 56 does not differ essentially from the lowest ones of the inlet pressures prevailing in the ducts 54. The extent to which leakage can occur and hence the choice of the leak restriction depends upon the use. For the selection device 15 of the control system shown in FIG. I, it is in this connection for example the specific variation in volume of the chamber of pressure difference sensor 17 communicating with the common outlet that plays a part, in which the permissible deviationin the pressure sensed by the pressure sensor from the actual minimum pressure should be observed.

For the selecting device shown in FIG. 5b the same reference numerals are used as for that shown in F IG. 5a. In this case, the valve bodies 52 consist of foil elements which can cooperate with the seatings 53 in a sealing manner. Leak restrictions 58 consist of apertures in the foil elements provided in such manner that they cannot be sealed by the seatings 53. The operation of this selection device is the same as that shown in FIG. 5a so that it need not be described here.

The selecting device shown in FIG. 50 selects the maximum pressure from several (four) inlet pressures. For components corresponding to those of FIG. 5a the same reference numerals are used. The only difference from the selecting device shown in FIG. 5a is that in the present case the check valves all pass in the opposite I direction from the check valves shown in FIG. a.

When all the pressures in ducts 54 are lower than in ducts 52 and common outlet 56, respectively, the valve bodies 52 remain forced against the seatings 53 in a sealing manner. If, however, in only one of the ducts 54 a pressure occurs which is higher than the pressure in y the common outlet 56, the check valve 51 which com- 56 does not differ essentially from the highest ones of I the inlet pressures prevailing in the ducts 54.

The selecting devices described present the advantages of simplicity in construction, compactness and reliable operation. Extension to, for example, eight or nine inlets desirable for, for example, an 8-cylinder thermodynamic reciprocating machine, is possible in a simple manner while maintaining the advantages.

In addition to the embodiments shown, all kinds of other embodiments of the selecting devices are of course possible. Reference numeral 60 in FIG. 6 denotes a housing in which a diaphragm 61 is accommodated which is secured to the housing and which separates a chamber 62 from a chamber 63. Chamber 62 is admissible via an inlet 64, chamber 63 via an inlet 65.

The diaphragm 61 supports a magnetic element 66 end a magnetic element 84 which faces a soft iron core 85 with induction coil 86 arranged within the chamber 72 and to which electric conductors 87 are connected which are passed to the outside through the wall of the housing 70. When the rod 78 again moves in the direction of the assembly core 85, induction coil 86, an electric signal is induced in this case also in the coil 86 the value of which is proportional to the distance over which the rod 78 has moved.

By supplying to the

chambers

72 and 76 the pressure differential Ap, which represents a flow of air of combustion and to the

chambers

73 and 75 the pressure differential A p which represents a fuel flow, a equilibrium condition is obtained in which the rod 78 assumes a given position with a corresponding electric signal from the induction coil 86. The forces on the rod as a result of the pressure differential prevailing across the diaphragms 7d and 77 then make equilibrium with the forces on the said rod as a result of the tension forces in the diaphragm.

When pressure differential A p varies, the equilibrium of forces is disturbed and the rod 78 assumes a new position in which a new equilibrium of forces is achieved. The induction coil 86 then supplies a new electric signal corresponding to the new position. i

The control mechanism 20 in the common supply duct 10 for air of combustion of FIGS. 2 and 4, respec which faces a soft iron core 67 with induction coil 68 arranged inside the chamber 63. Electric conductors 69 are connected to the induction coil and are passed to the outside through the wall of the housing 60.

When the magnetic element 66 moves in the direction of the core 67, an electric signal the value of which is proportional to the distance over which the magnetic element 66 moves, is produced in the induction coil 68.

The two different pressures can be supplied to the

inlets

64 and 65 and are provided, for example, by the selecting device 15 and the common fuel supply duct 15 of FIG. 1, in which the present device serves as a pressure difference sensor 17.

When the pressure difi'erential varies, the electric signal of the induction coil 68 varies proportionally thereto in that the pressure differential across the diaphragm 61 varies and said diaphragm moves towards or away from the core 67.

FIG. 7 shows a housing 70 having a partition 71 which divides the space within the housing into two sub-spaces. One sub-space consists of two

chambers

72 and 73 separated from each other by a diaphragm 74, while the other sub-space consists of two

chambers

75 and 76 separated from each other by a diaphragm 77.

Diaphragms 74 and 77 are connected at one end to the housing 70 and at the other end to a common rod 78 which can reciprocate axially and is passed through the partition 71 via an aperture 79.

Chambers

72, 73, 75 and 76 each comprise

inlets

80, 81, 82 and 83, respectively. The rod 78 supports at one tively, can be controlled directly with the signal supplied by the induction coil 86.

The same medium is present in the

chambers

73 and 75. Any medium leak from the higher to the lower pressure chamber consequently provides no complications while the pressure differential between the chambers is hardly influenced by small leakage.

What is claimed is:

l. A multicylinder thermodynamic reciprocating ma chine in which each cylinder comprises a heater to which thermal energy from an associated burner device can be supplied, in which a fuel supply and a supply for air of combustion communicate with each burner device, in which the ends of the fuel supplies remote from the associated burner device communicate with a common fuel supply duct in which a pressure control device maintains a constant fuel pressure during operation and the ends of the supplies for air of combustion remote from the associated burner device communicate with a common supply duct for air of combustion, each heater comprising a temperature-sensitive element which actuates a fuel control mechanism in the fuel supply of the associated burner device for controlling the fuel flow to the said device, each fuel supply, taken in the direction of flow, comprising before the fuel control mechanism a flow restricting element across which during operation a pressure differential prevails which is proportional to the rate of fuel flow through the relevant supply, the quantity of air of combustion to be supplied being controlled in accordance with the supplied quantity of fuel, characterized in that a selecting device is present for the automatic selection of the maximum or minimum fuel pressure from several fuel inlet pressure and the outlet sides of the flow restricting elements communicate with an equal number of inlets of the selecting device, the pressure differential between the constant fuel pressure in the common fuel supply duct and the selected maximum or minimum fuel pressure influencing a control member which actuates a control mechanism for air of combustion in the common supply duct for air of combustion.

2. Amulticylinder thermodynamic reciprocating machine as claimed in claim 1, characterized in that a fuel auxiliary duct is present which communicates with one end with the common fuel supply duct, in which auxiliary duct a flow restricting element is also incorporated von the inlet side of which the constant fuel pressure prevails and the outlet side of which also communicates with an inlet of the selecting device, which selecting device selects the minimum fuel pressure, the fuel auxiliary duct furthermore comprising, taken in the direction of flow after the flow restricting element, a fixed restriction which is chosen to be so that below a given minimum fuel flow to the fuel supplies the likewise constant pressure prevailing on the outlet side of the flow restricting element in the fuel auxiliary duct is lower than the pressures which prevail in that case on the outlet sides of the flow restricting elements in the fuel supplies.

3. A multicylinder thermodynamic reciprocating machine as claimed in claim 1 in which a further flow restricting element is present in each supply for air of combustion and across which during operation a pressure differential prevails which is proportional to the rate of the flow of air of combustion through the relevant supply, characterized in that a further selecting device is present for the automatic selection of the maximum pressure of air of combustion from several inlet pressures 'of air of combustion and the outlet sides of the further flow restricting elements communicate with an equal same number of inlets of the further selecting device, the pressure differential between the pressure of air of combustion on the inlet side of the further flow restricting elements and the selected maximum pressure of air of combustion influencing the control member in the opposite sense to the fuel pressure differential.

4. A multicylinder thermodynamic reciprocating machine as claimed in claim 1, characterized in that the selecting device and further selecting device, respectively, consist of a number of check valves which pass only in one direction and which are arranged beside each other with their directions of passage mutually in the same direction, the valves constituting with their one side inlets for an equal number of inlet pressure and communicating with their other sides with a common outlet, the inlet and outlet sides of each valve being always in open communication with each other by means of a leak restriction.

5. A multicylinder thermodynamic reciprocating machine as claimed in claim 4, characterized in that each check valve comprises as a valve body a foil element which can cooperate in a sealing manner with a seating, said foil element comprising an aperture as a leak restriction.

6. In a thermodynamic engine, operable with sources of fuel and air, the engine having a plurality of cylinders, each of which has at least one reciprocating piston therein, a heater for providing thermal energy to each cylinder, a burner for supplying thermal energy to each heater fuel and air supply ducts respectively feeding fuel and air to said burners from said fuel and air sources, the improvement in combination therewith of means for controlling the amounts of fuel and air supplied to the burners comprising: a common fuel duct feeding the fuel supply ducts from the fuel source, a

common air duct feeding the air supply ducts from the air source, first means associated with the fuel supply and common fuel duct for maintaining substantially constant pressure on said fuel, second means for measuring the temperature in each heater and providing a corresponding signal, a flow restrictor in each fuel supply duct including third means for measuring the pressure in the downstream side of the restrictor, said downstream pressure inversely corresponding to the rate of flow through the restrictor, a first flow control valve in each fuel supply duct intermediate said restrictor and the burner, a second flow control valve in the common air duct, fourth means to which is communicated the pressures from said third means, and which selects the lowest pressure, fifth means receiving said lowest pressure from the fourth means, further duct means communicating the constant pressure from the common fuel duct to said fifth means which compares and determines the difference between said lowest pressure and said constant pressure and provides a resultant output signal, sixth means communicating said output signal to said second flow control valve for adjusting said valve, seventh means receiving the temperature signals from said second means associated with each heater and providing an inversely corresponding control signal to the first flow control valve associated with that heater, whereby lower temperature in a heater causes the seventh means to open the first flow control valve in the supply fuel duct, which greater flow produces a greater pressure drop across the flow restrictor and a lower pressure reading by the third means, which low pressure is selected by the fourth means and compared with the constant pressure by the fifth means which causes the second flow control valve in the common air duct to be opened correspondingly.

7. Apparatus according to claim 6, further comprising an air-flow restrictor in said common air duct through which the air-flow has a pressure differential, eighth means communicating with said air-flow restrictor and sensing and measuring said pressure differential and providing a corresponding signal, a comparison means receiving said signal from the eighth means and said signal from said fifth means corresponding to the fuel flow pressure differential, the comparison means having a resultant output controlling the second flow control valve in said common air duct, whereby (i) a greater air-flow through the common air duct produces a greater pressure differential through said airflow restrictor, said eighth means providing a signal corresponding to said pressure differential for adjusting said second flow control valve to reduce the air-flow therethrough, and (ii) a smaller air-flow through said common air duct produces a reverse effect.

8. Apparatus according to claim 6 further comprising an auxiliary fuel duct including a flow restrictor therein communicating said common fuel supply duct with said fuel source, and further duct means communicating said common fuel supply duct with said fourth means, whereby air-flow will be constant regardless of fuel flow below predetermined minimum valve of said fuel flow.

9. Apparatus according to claim 8 further comprising an air-flow restrictor in each air supply duct, means for measuring the pressure in the downstream side of each of said air-flow restrictors, said downsream pressure imversely corresponding to the rate of flow through the air estrictor, means for selecting the maximum pressure, means for comparing said maximum pressure with the pressure in said common supply duct and providing a corresponding signal to said comparison means and in opposite sense to the signal of said fifth means that determines fuel pressure differential, said comparison means controlling said flow control valve in the common air duct.

mg v UNITED. STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,822,550 Dated ly 1974 Inventor) KLAUS BRANDENBERG ET AL It is certified that error appears in theabove-identified patent and that said Letters Patent are hereby corrected as shown below:

fl IN THE TITLE PAGE:

In the "FOREIGN APPLICATION PRIORITY DATA" the foreign application number should be --7lO36l0--.

Col. 1, line 26, change "A" to --a- Col. 4, line 47, after "comprises" insert -as-- Col. 7, line 22, delete "6"" and insert -lO'- Claim 5, line 5, "imversely" should be --inversely-;

line 6, "estrictor" should be -restrictor'- Signed and sealed this 3rd day of June 1975.

(SEAL) Attest:

C. MARSHALL DANN RUTH C. MASON Commissioner of Patents Attesting Officer and Trademarks

Claims

1. A multicylinder thermodynamic reciprocating machine in which each cylinder comprises a heater to which thermal energy from an associated burner device can be supplied, in which a fuel supply and a supply for air of combustion communicate with each burner device, in which the ends of the fuel supplies remote from the associated burner device communicate with a common fuel supply duct in which a pressure control device maintains a constant fuel pressure during operation and the ends of the supplies for air of combustion remote from the associated burner device communicate with a common supply duct for air of combustion, each heater comprising a temperature-sensitive element which actuates a fuel control mechanism in the fuel supply of the associated burner device for controlling the fuel flow to the said device, each fuel supply, taken in the direction of flow, comprising before the fuel control mechanism a flow restricting element across which during operation a pressure differential prevails which is proportional to the rate of fuel flow through the relevant supply, the quantity of air of combustion to be supplied being controlled in accordance with the supplied quantity of fuel, characterized in that a selecting device is present for the automatic selection of the maximum or minimum fuel pressure from several fuel inlet pressure and the outlet sides of the flow restricting elements communicate with an equal number of inlets of the selecting device, the pressure differential between the constant fuel pressure in the common fuel supply duct and the selected maximum or minimum fuel pressure influencing a control member which actuates a control mechanism for air of combustion in the common supply duct for air of combustion.

2. A multicylinder thermodynamic reciprocating machine as claimed in claim 1, characterized in that a fuel auxiliary duct is present which communicates with one end with the common fuel supply duct, in which auxiliary duct a flow restricting element is also incorporated on the inlet side of which the constant fuel pressure prevails and the outlet side of which also communicates with an inlet of the selecting device, which selecting device selects the minimum fuel pressure, the fuel auxiliary duct furthermore comprising, taken in the direction of flow after the flow restricting element, a fixed restriction which is chosen to be so that below a given minimum fuel flow to the fuel supplies the likewise constant pressure prevailing on the outlet side of the flow restricting element in the fuel auxiliary duct is lower than the pressures which prevail in that case on the outlet sides of the flow restricting elements in the fuel supplies.

3. A multicylinder thermodynamic reciprocating machine as claimed in claim 1 in which a further flow restricting element is present in each supply for air of combustion and across which during operation a pressure differential prevails which is proportional to the rate of the flow of air of combustion through the relevant supply, characterized in that a further selecting device is present for the automatic selection of the maximum pressure of air of combustion from several inlet pressUres of air of combustion and the outlet sides of the further flow restricting elements communicate with an equal same number of inlets of the further selecting device, the pressure differential between the pressure of air of combustion on the inlet side of the further flow restricting elements and the selected maximum pressure of air of combustion influencing the control member in the opposite sense to the fuel pressure differential.

6. In a thermodynamic engine, operable with sources of fuel and air, the engine having a plurality of cylinders, each of which has at least one reciprocating piston therein, a heater for providing thermal energy to each cylinder, a burner for supplying thermal energy to each heater, fuel and air supply ducts respectively feeding fuel and air to said burners from said fuel and air sources, the improvement in combination therewith of means for controlling the amounts of fuel and air supplied to the burners comprising: a common fuel duct feeding the fuel supply ducts from the fuel source, a common air duct feeding the air supply ducts from the air source, first means associated with the fuel supply and common fuel duct for maintaining substantially constant pressure on said fuel, second means for measuring the temperature in each heater and providing a corresponding signal, a flow restrictor in each fuel supply duct including third means for measuring the pressure in the downstream side of the restrictor, said downstream pressure inversely corresponding to the rate of flow through the restrictor, a first flow control valve in each fuel supply duct intermediate said restrictor and the burner, a second flow control valve in the common air duct, fourth means to which is communicated the pressures from said third means, and which selects the lowest pressure, fifth means receiving said lowest pressure from the fourth means, further duct means communicating the constant pressure from the common fuel duct to said fifth means which compares and determines the difference between said lowest pressure and said constant pressure and provides a resultant output signal, sixth means communicating said output signal to said second flow control valve for adjusting said valve, seventh means receiving the temperature signals from said second means associated with each heater and providing an inversely corresponding control signal to the first flow control valve associated with that heater, whereby lower temperature in a heater causes the seventh means to open the first flow control valve in the supply fuel duct, which greater flow produces a greater pressure drop across the flow restrictor and a lower pressure reading by the third means, which low pressure is selected by the fourth means and compared with the constant pressure by the fifth means which causes the second flow control valve in the common air duct to be opened correspondingly.

10. Apparatus according to claim 6 wherein said sixth means further comprises means for amplifying the signal from the fifth means.

11. Apparatus according to claim 6 wherein said engine has an output shaft, said air source is driven by said shaft.