U.S. patent number 3,780,528 [Application Number 05/226,913] was granted by the patent office on 1973-12-25 for thermodynamic reciprocating machine with controlled fuel/air supply.
This patent grant is currently assigned to U.S. Philips Corporation. Invention is credited to Klaus Brandenburg.
United States Patent |
3,780,528 |
Brandenburg |
December 25, 1973 |
THERMODYNAMIC RECIPROCATING MACHINE WITH CONTROLLED FUEL/AIR
SUPPLY
Abstract
A thermodynamic reciprocating engine in combination with a
carburetor having inlets and control apparatus responsive to air
and fuel flow for providing optimum operation.
Inventors: |
Brandenburg; Klaus
(Kirchen-Wehbach, DT) |
Assignee: |
U.S. Philips Corporation (New
York, NY)
|
Family
ID: |
19812611 |
Appl.
No.: |
05/226,913 |
Filed: |
February 16, 1972 |
Foreign Application Priority Data
Current U.S.
Class: |
60/39.27;
60/39.281; 200/83A; 60/794; 60/39.63 |
Current CPC
Class: |
F02G
1/047 (20130101) |
Current International
Class: |
F02G
1/00 (20060101); F02G 1/047 (20060101); F02g
003/02 () |
Field of
Search: |
;60/39.27,24D,39.28R,39.28T,39.29,39.63 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Gordon; Clarence R.
Claims
What is claimed is:
1. In a thermodynamic engine including a burner for combustion of
fuel and air, with a fuel inlet fed by a fuel duct, an air inlet
fed by an air duct, a flow valve in each of said ducts, a heater
heated by the burner, a temperature sensing element indicating
heater temperature, a device for supplying air to said air duct,
drive means from said engine to said device, the improvement in
combination therewith of control apparatus responsive to at least
one parameter of the engine for controlling said fuel flow and for
controlling said air flow to be proportionate to said fuel flow,
comprising, an air flow restricting element in the air duct
intermediate said air supply device and the air flow valve
responsive to air flow therethrough and providing a corresponding
1st signal, a source of constant pressure fluid medium, an outlet
duct for said medium flow, a main valve controlling flow through
said outlet duct, a second flow restricting element in said outlet
duct downstream of said main valve for providing a second flow
signal, a fixed restriction in said outlet duct downstream of said
second flow-restricting element, a control apparatus responsive to
signals from said temperature sensing element for opening wider
said fuel duct valve and said main valve in said medium outlet duct
when temperature is low, and vice versus, a control member
receiving said first and second flow signals respectively from said
flow restricting elements in said air flow and fluid medium flow
ducts, for determining the difference between said signals, and
producing a resulting control signal to said air flow valve.
2. Apparatus according to claim 1 wherein said air-flow element and
fluid medium flow restricting element register the fluid pressure
of the fluid flow in the corresponding ducts.
3. Apparatus according to claim 1 wherein said fluid medium is a
gas.
4. Apparatus according to claim 1 wherein said fluid medium is a
liquid.
5. Apparatus according to claim 1 wherein said control member
comprises a housing with first and second ports, a diaphragm within
the housing dividing same into first and second chambers, an
electromagnetic transducer having one fixed and one moving part,
one of these parts secured to said diaphragm and the other to the
housing in the first chamber, the first and second ports
communicating with said flow-restricting elements respectively of
the medium flow and air flow ducts, whereby the diaphragm registers
the pressure differential between said elements and the
electromagnetic transducer is actuated by the diaphragm and
produces a corresponding electrical signal to said flow valve in
the air flow duct.
Description
BACKGROUND OF THE INVENTION
The invention relates to a thermodynamic reciprocating machine
comprising a burner device having a fuel inlet as well as an inlet
for air of combustion with which a duct of air of combustion
communicates, which latter communicates with the outlet of a device
for supplying air of combustion coupled to a shaft of the machine,
in which a control apparatus reacting to at least one parameter of
the machine is present for controlling a fuel flow to the fuel
inlet and in which the quantity of air of combustion to be supplied
is controlled in proportion to the supplied quantity of fuel by
means of a control member which operates a control mechanism in the
duct for air of combustion, in which duct a flow restricting
element is present which provides a signal proportional to the
speed of the flow of air of combustion through the said duct, which
signal influences the control member.
In thermodynamic reciprocating machines it is known to couple a fan
for the supply of air to the burner device directly to the shaft of
the machine so that the number of revolutions of the fan is
determined only by the number of revolutions of the machine.
This is often done in machines of high powers in which the
comparatively high power required for driving the fans is directly
supplied by the machines themselves.
The control apparatus which controls the fuel supply to the burner
device can react to one or several parameters. For example, it may
react only to the heater temperature of the machine (British Patent
Specification 895,869), to both the heater temperature and to the
average pressure of the working medium in the machine (British
Patent Specification 655,935) or, for example, to the said average
pressure in combination with the number of revolutions of the
machine (British Patent Specification 691,785, Dutch Patent
Specification 68,679).
Control in a thermodynamic reciprocting machine of the quantity of
air of combustion to be supplied to the burner device in proportion
to the quantity of fuel supplied is known from the said British
Patent Specification 895,896. In this known machine, pressure
differential gauges are arranged in the fuel duct and the duct for
the supply of air of combustion, which gauges influence,
independently of each other but in opposite senses, the same
control member of a hydraulic system which controls the position of
a throttle valve as a control mechanism in the duct for air of
combustion in accordance with the flow of fuel. Since the flows of
fuel to the burner device are comparatively small, measurement of
said flows with a pressure differential gauge is hardly possible in
a reliable manner. The pressure drop across measuring plates in
small fuel flows depends upon temperature because in that case the
flow through said plates is not turbulent but laminar.
As a result of this the ratio air-fuel can easily differ from the
desirable value. The use of a pressure differential gauge in the
fuel duct therefore exhibits drawbacks.
In thermodynamic reciprocating machines in which the fan is coupled
to a shaft of the machine and in which the supply of air of
combustion is controlled in direct dependence upon the fuel supply,
it is a problem -- since the use of a fuel pressure differential
gauge is avoided for the above-mentioned reasons -- to adapt the
control of air with a given fan characteristic (yield versus number
of revolutions) to the fuel control in such manner that
irrespective of the number of revolutions of the fan the correct
air-fuel ratio is always obtained.
The use of complicated and expensive electronic circuits (for
example diode networks) which derive a suitable control signal for
the flow of air of combustion from each control signal for the fuel
flow, is then substantially unavoidable.
Since the choice of the fan depends upon the type of machine (both
as regards power and application) in question, and each type of fan
has its own characteristic, this means that for each type of
machine with associated type of fan an air-fuel control system is
necessary which has been developed especially for this type. In
addition to the condition that a satisfactory solution is not
possible in all cases, it is undesirable for practical and economic
reasons that each type of machine with associated type of fan
should need a separate air-fuel control system and that the same
number of control systems as the number of machine types should be
necessary. It is the object of the present invention to mitigate
the said drawbacks.
SUMMARY OF THE NEW INVENTION
For that purpose, the thermodynamic reciprocating machine according
to the invention is characterized in that a device is present for
supplying a pressure medium under a constant pressure and having a
mediun outlet with which a medium outlet duct communicates, the
medium outlet duct, taken from the medium outlet, comprising
successively a control element, a further flow restricting element
and a fixed restriction, the control apparatus also operating the
control element for controlling the flow of medium through the
medium outlet duct in proportion to the flow of fuel controlled by
said apparatus, the further flow restricting element providing a
further signal which is proportional to the speed of the flow of
medium and which influences the control member in a sense opposite
to the signal originating from the flow restricting element.
In the present case, the flow of air of combustion is not
controlled directly but indirectly, via the medium flow as an
auxiliary flow, in proportion to the flow of fuel. The medium flow
may be large in comaprison with the fuel flow so that the further
flow restricting element provides a comparatively large signal
representing the medium flow in a reliable manner.
The control apparatus ensures that the flow of medium is varied in
proportion to the fuel flow, for which purpose the characteristic
of the fuel control element and that of the medium control element
are adapted to each other. The control apparatus may have a
universal construction and application.
Since the flow of air of combustion is directly comapred with and
controlled in accordance with likewise a flow, the medium flow in a
separate medium control system, no special measures are required to
obtain the desirable proportionality between the flows of air of
combustion and medium. The characteristic of the fan plays
substantially no part of importance any longer. The medium control
system may have a universal construction; the elements from which
this circuit is constructed may be the same for all the cases
occurring in practice.
Measurement of small flows of fuel with all the difficulties
involved is no longer necessary. In this manner a universal
air-fuel control system of an inexpensive and simple construction
is obtained for thermodynamic reciprocating machines having their
fan coupled to a shaft of the machine, irrespective of the type of
machine and fan characteristic. The required adaptation of the air
control to the fuel control occurs once and is generally solved in
designing the control system, and is incorporated in said
system.
As regards the flow restricting element and the further flow
restricting element, respectively, there is a great possibility in
choice. To be considered are, for example, Pitot tubes Venturi
tubes, measuring plates which all provide a pressure differential
as a signal. This pressure differential may directly influence the
control member, for example, in the manner as described in the
British Patent Specification 895,869. The pressure differential may
also be converted, for example, into an electric signal in a
pressure converter and the resulting signal be applied to an
electric comparison element which reacts as a control member to the
difference between two electric signals representing the flow of
air of combustion and the medium flow, respectively.
Furthermore, for example, pressure sensors may be used which sense
the overall pressure (static pressure plus dynamic pressure) and
supply a pressure signal which again directly influences the
control member or is first converted into another signal, for
example an electric signal. To be considered are also anemometers,
for example hot wire flow meters, the latter providing an electric
signal directly.
Of course, the flow restricting element and the further flow
restricting element in the same control system need not be the same
type of element, that is to say the flow restricting element may
be, for example, a Venturi, while the further flow resricting
element is a Pitot tube, a measuring plate, an overall pressure
sensor and so on, provided the signal characteristics correspond
mutually.
As a flow restricting element in the duct for air of combustion an
element which provides a pressure differential (dynamic pressure
gauge) is to be preferred over an element which provides one
pressure signal (static pressure plug dynamic pressure). The reason
for this is that the pressure in the burner device may vary in
certain circumstances so that the static pressure in the duct for
air of combustion communicating therewith may also vary. In the
case of measurements on the basis of pressure differentials, the
influences of the variations of the static pressure in the duct for
air of combustion on the determination of the flow of air of
combustion is eliminted.
In order that the invention may be readily carried into effect, it
will now be described in greater detail, by way of example, with
reference to the accompanying diagrammatic drawings which are not
drawn to scale.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 shows a thermodynamic reciprocating machine having a fan
coupled to a shaft of the machine and comprising an air-fuel
control system.
FIG. 2 shows an embodiment of a pressure differential converter in
which a difference in two pressures supplied to it are converted
into an electric signal.
FIG. 3 shows an embodiment of a combined pressure differential
comparison and converting element in which two pressure
differentials (four pressure signals) supplied thereto are compared
and the difference therebetween is converted into an electric
signal.
DESCRIPTION OF THE PREFERRED EMBODIMENT
Reference numeral 1 in FIG. 1 denotes a thermodynamic reciprocating
machine comprising a burner device 2 having a fuel inlet 3 with
which a fuel duct 4 communicates and comprising an inlet 5 for air
of combustion with which a duct 6 for air of combustion
communicates which conmunicates with the outlet 7 of a fan 9
coupled to a shaft 8 of the machine 1. A control apparatus 10 which
reacts to the electric signal originating from a
temperature-sensitive element 11 and which element senses the
temperature of a heater of the machine not shown operates an
electromagnetic valve 12 in the fuel duct 4. By means of said valve
a fuel flow to the burner device 2 is controlled in accordance with
the heater temperature. When the heater temperature increases, for
example by reduction of the power derived from the machine, the
control apparatus 10 ensures that the valve 12 is closed more so
that less fuel flows to the burner device 2. Conversely, when the
heater temperature decreases, the control apparatus 10 ensures that
the valve 12 is opened more so that more fuel is passed. Fuel may
be supplied in the manner as described, for example, in the British
Patent Specification 895,869.
A control member 13 operates a control mechanism 14, for example a
throttle valve, in the duct for air of combustion. The control
member controls in accordance with the difference signal between
the signals originating (a) from a flow restricting element 15
present in the duct 6 for air of combustion (b) and from a further
flow restricting element 20, which elements each supply a signal
which is proportional to the flow rate through the relevant duct. A
device 16 is present which supplies a pressure medium under a
constant pressure and in this case consists of a compressor for
atomized air which normally is already present to supply the air
which is guided along the atomizers of the fuel burners so as to
obtain a good nebulisation of the fuel. The compressor 16 comprises
an outlet 17 with which an outlet duct 18 communicates.
Incorporated in the outlet duct 18 are an electromagnetic valve 19
as a control element for the air flow through the outlet duct, the
further flow restricting element 20 which, as already stated,
influences the control member 13, and a fixed restriction 21.
The control apparatus 10 operates both the valve 12 in the fuel
duct 4 and the electromagnetic valve 19. The characteristics of
electromagnetic valves 12 and 19 are matched mutually, as well as
the characteristics of the flow restricting element 15 and the
further flow restricting element 20. Otherwise, as already stated
in the preamble, the flow restricting element and the further flow
restricting element may be different types of instruments, while
other instruments are to be considered, for example, Pitot tubes,
Venturis, measuring plates with which pressure differentials
proportional to the flow rate are produced, pressure sensors which
measure the overall pressure or anemometers such as electric
anemometers which provide an electric signal which is a measure of
the flow.
The control member 13 may be a hydraulic control member which is
controlled hydraulically by pressure and pressure differential
signals, respectively, originating from elements 15 and 20. It may
also be an electric comparison element which compares electric
signals originating directly from elements 15 and 20 (anemometers)
or originating therefrom indirectly (pressure differential) signals
converted into electric signals) and operates the control mechanism
14 on the basis of the difference signal.
Conversion of a pressure differential into a corresponding electric
signal may be carried out, for example, in a converter as shown in
FIG. 2 to be described hereinafter. When the elements 15 and 20
supply pressure differentials while control mechanism 14 is
controlled electrically, a combined unit may be used as is shown in
FIG. 3 to be described hereinafter.
The operation of the control system shown in FIG. 1 is further as
follows. During operation, air of combustion is supplied to the
burner device 2 by the fan 9 coupled to the shaft 8 of the machine
1 while fuel is supplied to the said burner device via fuel duct 4,
in a manner not shown.
Compressor 16 supplies a flow of air of a sufficiently high
pressure relative to the atmospheric pressure, which flows away to
the atmosphere via outlet duct 18. In a certain fixed position of
the valve 19 a constant air flow flows through the duct 18 and the
pressure between said valve and the fixed restriction 21 is also
constant with the exception of a possible influence of variations
in the ambient pressure hereon. When the latter is disturbing, the
element 20 may be of the type which provides a pressure
differential. The influence of ambient pressure variations is then
eliminated in an analogous manner to the influence of pressure
variations in the burner device of the duct for air of
combustion.
When the heater temperature decreases, this results in a variation
in the electric signal supplied by the temperature-sensitive
element 11 in such manner that the control apparatus 10 further
opens both the valve 12 and the valve 19 and that both the fuel
flow in the fuel duct 4 and the air flow through the outlet duct 18
increase to th same extent. As a result of this, the signal
produced by the further flow restricting element 20 also varies,
increases in value, which has for its result that the control
member 13 further opens the control mechanism 14 and more air of
combustion flows to the burner device 2.
Owing to the larger flow of air of combustion, the value of the
signal produced by the flow restricting element 15 will also
increase in the first instance as a result of which the control
member 13 is forced to slightly close again the control mechanism
14 which in turn results in a reduction of the signal produced by
the flow restricting element 15 as a result of which the control
mechanism 14 is again opened slightly further, and so on. By
suitable mutual matching of the relevant components of the control
system, however, such an oscillation effect is prevented and the
equilibrium condition is rapidly reached. When the heater
temperature increases, the control system operates in the opposite
direction from in the case of a decrease of the heater temperature,
that is to say, the control apparatus 10 in that case closes the
valves 12 and 19 further so that the flow of air through the outlet
duct 19 decreases to the same extent as the fuel flow through the
fuel duct 4.
The valve of the signal supplied by the further flow restricting
element 20 also decreases, which has for its result that the
control member 13 closes the control mechanism 14 further and less
air of combustion is passed.
Instead of as is shown in the figure, the control mechanism 14 may
also be provided in other places, for example, between the fan 9
and the flow restricting element 15 or on the inlet side of the
fan. When the number of revolutions of the machine and hence the
number of revolutions of the fan vary, the signal supplied by the
flow restricting element 15 will also vary due to the varied fan
yield. In that case the control member 13 will further open or
close the control mechanism 14 so that upon variation of the number
of revolutions of the fan the quantity of air of combustion passed
to the burner device 2 remains unchanged irrespective of the fan
characteristic. The control system described is simple and compact
of construction, may have a universal construction and application
for all types of thermodynamic reciprocating machines having a fan
coupled to a shaft of the machine, irrespective of the type of fan.
Of course, all kinds of other devices are possible which supply a
pressure medium under a constant pressure, for example, a medium
storage container. Not only gases but also liquids are to be
considered as media. Medium which has flowed through the outlet
duct need not necessarily be dissipated to the atmosphere but may
be caught, if desirable, and then be returned to the device.
Reference numeral 30 in FIG. 2 denotes a housing in which a
diaphragm 31 is secured to the housing and which separates a
chamber 32 from a chamber 33. Chamber 32 is accessible via an inlet
34, chamber 33 via an inlet 35.
The diaphragm 31 supports a magnetic element 36 which faces a soft
iron core 37 with induction coil 38 inside the chamber 33. Electric
conductors 39 are connected to the induction coil and are passed
out through the wall of the housing 30.
When the magnetic element 36 moves in the direction of the core 37,
an electric signal is produced in the induction coil 38 the value
of which signal is proportional to the distance over which the
magnetic element 36 moves.
The two different pressures which are supplied by the flow
restricting element 15 or the further flow restricting element 20,
constructed, for example, as Venturies, may be applied to the
inlets 34 and 35.
When the flow of air of combustion and medium, respectively,
through the outlet duct varies, and hence the pressure differential
produced, the electric signal of the induction coil 38 varies
proportionally thereto since the pressure differential across the
diaphragm 31 varies so that said diaphragm moves towards the core
37 or away from it.
FIG. 3 shows a housing 40 having a partition 41 which divides the
space inside the housing into two sub-spaces. One sub-space
consists of two chambers 42 and 43 separated from each other by a
diaphragm 44, the other subspace consisting of two chambers 45 and
46 separated from each other by a diaphragm 47.
Diaphragms 44 and 47 are connected at one end to the housing 40 and
at the other end to a common rod 48 which can reciprocate in the
axial direction and is passed through the partition 41 through an
aperture 49.
Chambers 42, 43, 45, 46 each have an inlet 50, 51, 52 and 53,
respectively. At its one end the rod 48 has a magnetic element 54
which faces a soft iron core 55 with induction coil 56 inside the
chamber 42 and to which electric conductors 57 are connected which
are passed to the exterior through the wall of the housing 40. When
the rod 48 again moves in the direction of the assembly core
55/induction coil 56, an electric signal is induced in the coil 56
in this case also the value of which is proportional to the
distance over which the rod 48 has moved.
By supplying the pressure differential .DELTA.p.sub.1 to the
chambers 42 and 46 which represents the flow of air of combustion,
and by supplying the pressure differential .DELTA.p.sub.2 which
represents the medium flow in the outlet duct to the chambers 43
and 45, an equilibrium condition is obtained in which the rod 48
assumes a given position with a corresponding electric signal on
the induction coil 56. The forces on the rod and the result of the
pressure differentials prevailing across the diaphragms 44 and 47
then make equilibrium with the forces on the said rod as a result
of the tension forces in the diaphragms.
When the pressure differential .DELTA.p.sub.2 varies, the
equilibrium of forces is disturbed and the rod 48 assumes a new
position in which a new equilibrium of forces is achieved.
Induction coil 56 then supplies a new electric signal corresponding
to the new position.
The control mechanism 14 in the duct 6 for air of combustion of
FIG. 1 can be directly controlled by the signal supplied by the
induction coil 56.
The same medium is present in the chambers 43 and 45. Any medium
leakage from the higher to the lower pressure chamber therefore
provides no complications, while the pressure differential between
the chambers is hardly influenced by small leakage.
* * * * *