US3895901A

US3895901A - Fluidic flame detector

Info

Publication number: US3895901A
Application number: US497413A
Authority: US
Inventors: Elmer L Swartz
Original assignee: US Department of Army
Current assignee: US Department of Army
Priority date: 1974-08-14
Filing date: 1974-08-14
Publication date: 1975-07-22
Anticipated expiration: 1992-07-22

Abstract

A fluidic flame monitoring device is disclosed, the device comprising a fluidic amplifier, either of the bistable or proportional type, the power stream of which is modulated or switched in accordance with the temperature above an external flame. Connected to a control port of the fluidic amplifier is a chamber coupled to a source of fluidic pressure, the chamber incorporating a vented pressure regulating output. In the preferred inventive embodiment, an elongated thin-walled tube is coupled between the pressure regulating output of the chamber and the atmosphere, the flow resistance of the tube varying in response to the temperature of an external flame applied thereto. In one preferred embodiment, the absence of a flame alters the control signal pressure at the control port of the fluidic amplifier, switching the output power stream thereof. The switching of the output power stream is detected as an indication of flameout. When a proportional amplifier is utilized, modulation of the output power stream occurs in response to variations in flame temperature. The device can be utilized to control and shut off the fuel supply to an external burner in response to flameout.

Description

United States Patent 91 Swartz FLUIDIC FLAME DETECTOR Inventor: Elmer L. Swartz, Annandale, Va.

Assignee: The United States'of America as represented by the Secretary of the Army, Washington, DC.

Filed: Aug. 14, 1974 App], No; 497,413

References Cited UNITED STATES PATENTS 5/l970 Berrey 73/363 8/1971 Fehr et al.. 137/804 11/197 Meyer 137/804 l/l973 Monsen 137/804 X Primary Examiner-Edward G. Favors Attorney, Agent, or Firm-Nathan Edelberg; Robert P. Gibson; Saul Elbaum [451 July 22, 1975 s71 ABSTRACT A fluidic flame monitoring device is disclosed, the de ature above an external flame. Connected to a control port of the fluidic amplifier is a chamber coupled to a source of fluidic pressure, the chamber incorporating a vented pressure regulating output. In the preferred inventive embodiment, an elongated thin-walled tube is coupled between the pressure regulating output of the chamber and the atmosphere, the flow resistance of the tube varying in response to the temperature of an external flame applied thereto. In one preferred embodiment, the absence of a flame alters the control signal pressure at the control port of the fluidic amplifier, switching the output power stream thereof. The switching of the output power stream is detected as an indication of flameout. When a proportional amplifier is utilized, modulation of the output power stream occurs in response to variations in flame temperature, The device can be utilized to control and shut off the fuel supply to an external burner in response to flameout.

6 Claims, 1 Drawing Figure FUEL CONTROL VALVE READOUT -36 3s 1 4o (if 2 34\ BURNER 42 FLAME MONITOR FLUIDIC FLAME DETECTOR RIGHTS OF THE GOVERNMENT The invention described herein may be manufactured, used, and licensed by or for the United States Government for governmental purposes without the payment to me of any royalty thereon.

BACKGROUND OF THE INVENTION This invention generally relates to flame monitoring devices and is particularly concerned with a flame monitoring device manufactured of fluidic components.

For purposes of safety, as well as for other control purposes, it is often times necessary to monitor the presence or absence of a flame in a given piece of equipment. For example, and as concerns a heating system utilizing oil burners, it is necessary to detect the absence of a flame so that the fuel supply to the burner can be rapidly shut off. Another environment in which flame detectors have found utility is monitoring the occurrence of a flameout in aircraft engines, so that suitable corrective measures can be taken. Flame monitoring devices also find utility in fire alarm systems and the like.

Considering the wide-spread utility as just briefly indicated above, the prior art is replete with various apparatus all suitable for detecting the presence or absence of a flame. Most of such apparatus, however, exhibits one or more disadvantages, disqualifying the ap paratus for use in a particular environment. For example, many flame monitoring devices are electrical in nature, precluding their safe utilization in an explosive atmosphere. One specific such electrical device, utilizing thermocouples exhibits an extremely slow response time. Optical monitoring devices, on the other hand, necessarily incorporate a viewing area and it is often times difficult to maintain the viewing area clean and thus ensure reliability of the device. Mechanical apparatus, on the other hand, typically incorporate many moving parts, decreasing the useful life of the apparatus and furtherdegrading the response time thereof.

SUMMARY OF THE INVENTION It is thus apparent that a need exists in the flame monitoring art for the provision ofa device of markedly different construction and which serves to overcome the above-noted disadvantages of the prior-art. It is the primary objective of the instant invention to provide such a novel flame monitoring device.

A further objective of the instant invention is the provision of a flame monitoring device which utilizes fluidic components and requires virtually no moving parts.

Still another objective of the instant invention is the provision of a flame monitoring device which exhibits a rapid response time and which can be utilized in explosive environments with a high degree of safety.

Yet, another objective of the instant invention is the provision of a flame monitoring device which not only has the capability of indicating the presence or absence of a flame, but which further can indicate the temperature of the flame somonitored.

These objectives are implemented by the instant invention which will be seen to comprise a fluidic flame monitoring device utilizing a fluidic amplifier, either of the bistable or proportional type, having an inlet channel, an outlet channel, and a control port communicating with an interaction region such that a control signal applied to the control port modulates a power stream flowing between the inlet and outlet channels. Connected to the control port and providing the control signal thereto is the outlet of a chamber or tank which is coupled to a constant type flow or volume fluid source. The chamber further incorporates a vented pressure regulating output and an elongated thinwalled tube constituting a means for controlling the amount of venting through the pressure regulating output is connected thereto. When the elongated tube is placed in an external flame, the viscosity of the fluid flowing therein would suddenly increase as would the effective tube flow resistence, thereby reducing the I venting to the atmosphere and causing the pressure within the tank or chamber to increase. This increased pressure which, as aforestated, constitutes the control signal, causes the power stream in the outlet channel of the fluidic amplifier to be modulated. A readout mechanism, such as a meter, detects the modulation or pressure in the outlet channel and thereby serves to provide an indication of the presence, or absence, of a flame. In the event that a proportional amplifier is utilized, the amount of modulation, rather than bistable switching, indicates the temperature of the external flame.

BRIEF DESCRIPTION OF THE DRAWINGS The invention itself will be better understood and further features and advantages thereof will become apparent from the following detailed description of a preferred inventive embodiment, which description makes reference to the appended sheet of drawing, wherein the single FIGURE thereon represents in schematic illustration one embodiment of the instant invention utilizing a bistable fluidic amplifier for control of the fuel supply to an external burner.

DETAILED DESCRIPTION OF THE PREFERRED INVENTIVE EMBODIMENT With reference now to the drawing, the basic fluidic flame monitoring device of the instant invention cornprises a fluidic amplifier means generally designated by reference numeral 10 having, in typical fashion, an inlet channel 12, at least one outlet channel, such as

channels

14 and 16, at least one control port, such as

control port

18 and 20 communicating with an interaction region 22 such that a control signal applied to the control port would serve to modulate a power stream indicated by reference numeral 24 flowing between the inlet and outlet channels.

In the illustrated embodiment, a bistable fluidic amplifier is shown such that a change in control signal pressure at control port 20 will serve to switch the power stream from outlet channel 14 to outlet channel 16, and vice versa. As will be appreciated from the discussion herein-below, proportional amplifiers could similarly be utilized to advantage, the basic requirement being that any such fluidic amplifier should have a relatively high gain, and have the capability of being back loaded without deleterious switching effects.

With the embodiment of the invention shown, the fluidic amplifier is normally biased such that the power stream flows in outlet channel 16 in the presence of a normal pressure signal at control port 20, the power stream switching to outlet channel 14 upon an increase in the control pressure signal. As is also typical, the fluidic amplifier of the invention includes several atmospheric vents, such as

vents

26 and 28 ensuring stable operation.

A chamber or tank 30 is provided having an outlet 32 connected to the control port 20 to provide the control signal thereto. A fluid source. such as source 34, is coupled to the chamber or tank 30, source 34 preferably being of the variety providing a constant rate of flow, or constant volume. Chamber or tank 30 further incorporates a vented pressure regulating output indicated at reference numeral 36. Coupled to this output is a means generally designated by reference numeral 38 which controls the amount of venting therethrough in response to the temperature of an external flame indicated by reference numeral 40 as emanating from an external oil burner or the like 42. In the preferred inventive embodiment. means 38 constitute a thin-walled sensor tube which communicates flow of fluid from the tank or chamber 30 to the outside atmosphere. With the apparatus as shown, and as will be evident, a portion of the fluid provided by source 34 is vented to the atmosphere through the sensor tube, and a further portion is provided as the control signal at control port 20. Suitable and obvious pressure adjustments must, of course, be made such that the input flow from the high impedance 34 will not create enough pressure under normal conditionswithin the tank or chamber 30 to cause the power stream 24 to switch from its normal condition wherein it exits outlet channel 16, to its switched condition exiting outlet channel 14 as is shown.

When a flame, such as flame 40, is placed under the sensor tub 38, the viscosity of the fluid flowing therethrough would suddenly increase, and the effective tube flow resistence would likewise suddenly increase, thereby reducing the flow of fluid to the atmosphere, i.e. reducing the venting, and causing the pressure within the chamber or tank 30 to rise. A slight increase in this pressure would cause the high gain fluidic amplifier to switch such that the power stream exits outlet channel 14 as shown. A readout gauge 44, such as a pressure monitoring device, is coupled to the outlet channel 14 of the fluidic amplifier and, under the circumstances discussed above, readout gauge 44 will measurepressure only when a flame is present.

If the flame should suddenly go out, the pressure of fluid within the tank or chamber 30 would quickly return to its normal level and the fluidic amplifier 10 would switch back to its bias or normal side, wherein the power stream exits outlet channel 16. The reaction time of the system is fast in that the fluid supply through the tube 38 quickly cools the tube, and further due to the fact that the tube 38 is contemplated to be constructed having walls as thin as is feasible. In operation, response time of the device as illustrated constitutes a fraction of a second.

One particular utility of the preferred embodiment of the invention is to control the fuel supply to an external burner such as oil burner 42. In this respect, the outlet channel 14 of the fluidic amplifier 10 would be connected to a pressure actuated flow control valve 46 in a fuel supply line 48 for the external burner 42. In this fashion, the valve 46 would be normally biased in an open condition and, when flame-out of the burner was detected, the sudden drop of pressure at outlet channel 14 would cause the valve 46 to quickly shut off, and

thus prevent oil from unsafely accumulating at burner 42.

The basic device of the instant invention can be disposed at a location remote from the high temperature area of flame 40. In this respect, a conduit need only be coupled between the sensor tube 38 and the outlet 36 of the pressure chamber 30 as will be evident.

' For those applications in which temperature monitoring in addition to flameout monitoring is desired, fluidic amplifier 10 would constitute a proportional amplifier as opposed to the bistable device abovediscussed. In this event, a change in the temperature of flame 40 impinging upon sensor tube 38 would effect a proportional change in the amount of power stream flow through outlet channel 14 in conventional fashion.

From the foregoing description, it should be evident that the objectives set forth at the outset havebeen successfully achieved. It is to be understood that the invention described above constitutes but a preferred embodiment, and that obvious modifications thereto can be made by a person skilled in the art. ACCORD- INGLY What I claim is:

l. A fluidic flame monitoring device comprising: a fluidic amplifier means having an inlet channel, an outlet channel, and a control port communicating with an interaction region such that a control signal applied to said control port modulates a power stream flowing between said inlet and output channels; readout means coupled to said outlet channel for providing an indication of the pressure therein; a chamber coupled to a fluid source and having an output connected to said control port to provide said control signal thereto, said chamber further incorporating a vented pressure regulating output; and means coupled to said pressure regulating output for controlling the amount of venting therethrough in response to the temperature of an external flame; whereby the pressure within said chamber is varied by said external flame and the power stream within said fluidic amplifier is thereby modulated and indicated.

2. A device as defined in claim 1, wherein said means for controlling the venting of said pressure regulating output of said chamber comprises an elongated tube coupled between said pressure regulating output and the atmosphere, the flow resistence of said tube varying in response to the temperature of an external flame applied thereto.

3. A device as defined in claim 2, wherein said source of fluidic pressure for said chamber delivers a constant flow fluidic signal.

4. A device as defined in claim 2, wherein said fluidic amplifier is a bistable amplifier, said readout means thereby indicating the presence or absence of a flame.

5. A device as defined in claim 2, wherein said fluidic amplifier is a proportional amplifier, said readout means thereby indicating the temperature of the flame.

6. A device as defined in claim 2, further including in combination therewith a fuel supply line for an external flame burner, a pressure actuated flow control valve in said supply line, and wherein said outlet channel of said fluidic amplifier is connected to said flow control valve to provide the pressure for actuation thereof, whereby said fuel supply is shut off in the absence of a flame.

Claims

1. A fluidic flame monitoring device comprising: a fluidic amplifier means having an inlet channel, an outlet channel, and a control port communicating with an interaction region such that a control signal applied to said control port modulates a power stream flowing between said inlet and output channels; readout means coupled to said outlet channel for providing an indication of the pressure therein; a chamber coupled to a fluid source and having an output connected to said control port to provide said control signal thereto, said chamber further incorporating a vented pressure regulating output; and means coupled to said pressure regulating output for controlling the amount of venting therethrough in response to the temperature of an external flame; whereby the pressure within said chamber is varied by said external flame and the power stream within said fluidic amplifier is thereby modulated and indicated.