Flow control system

• US 5,601,071 A
• Filed: 01/26/1995
• Issued: 02/11/1997
• Est. Priority Date: 01/26/1995
• Status: Expired due to Fees

• Current Assignee: Honeywell International Inc.
• Original Assignee: Tridelta Industries, Inc. (Honeywell International Inc.)
• Inventors: Carr, Larry L., Mizerak, Dennis S.
• Primary Examiner(s): Dority, Carroll B.
• Application Number:
  US08/378,481
• Time in Patent Office: 747 Days
• Field of Search: 73/722, 73/716, 126/116 A, 126/110 R, 431/20
• US Class Current: 126/116.00A
• CPC Class Codes: F23N 1/022 using electronic means
• CPC Class Codes: F23N 2005/181 using detectors sensitive to rate of flow of air
• CPC Class Codes: F23N 2005/182 Air flow switch
• CPC Class Codes: F23N 2225/02 filling height in burners
• CPC Class Codes: F23N 2225/04 pressure
• CPC Class Codes: F23N 2227/02 Starting or ignition cycles
• CPC Class Codes: F23N 2227/04 Prepurge
• CPC Class Codes: F23N 2227/22 Pilot burners
• CPC Class Codes: F23N 2233/04 with variable speed
• CPC Class Codes: F23N 2233/10 forcing air through heat exchangers
• CPC Class Codes: F23N 2235/16 variable flow or proportional valves
• CPC Class Codes: F23N 2235/18 Groups of two or more valves
• CPC Class Codes: F23N 2237/02 two or more burners
• CPC Class Codes: F24H 15/20 characterised by control inputs
• CPC Class Codes: F24H 15/35 Control of the speed of fans
• CPC Class Codes: F24H 15/36 of burners
• CPC Class Codes: F24H 15/414 using electronic processing, e.g. computer-based
• CPC Class Codes: F24H 9/2085 using fluid fuel

Abstract

A control system for regulating a flow rate of a heat transfer fluid in a heat transfer system, the heat transfer system having a heat transfer fluid flow path, flow control device for creating flow along the path, a fuel source for providing a combustible fuel to the path, an air source for providing combustion air to the path, and an assembly for combusting the fuel and air, the control system comprising a sensor for sensing a measured flow value at the air source, a controller for storing an optimum flow value at the air source and for storing a range of operating control values for the flow control device, the operating control values corresponding to the optimum flow value, a system for calculating a deviation between the measured flow value and the optimum flow value, and a system for varying the operation of the flow control means in accordance with deviation.

Claims

1. A differential pressure transducer comprising:

a central housing section,

a first cap and a second cap, said caps fastened to said housing section to define a generally cylindrical housing,

a pair of generally identical pressure responsive members, each including a rigid circular diaphragm plate having a centrally located pin which extends to one side of said plate along the axis thereof, and an annular diaphragm element of resilient material molded to the outer edge of said diaphragm plate, said diaphragm element including a seal portion formed along the outer periphery thereof,

said pressure responsive members being mounted within said housing wherein said pins on said diaphragm plate are coaxially aligned and extend toward each other, the first of said pressure responsive elements being disposed between said central housing section and said first cap with said seal portion thereon forming a first chamber between said first pressure responsive member and said first cap, and the second of said pressure responsive members being disposed between said central housing section and said second cap with said seal portion thereon forming a second chamber between said second pressure responsive member and said second cap,

a first inlet port communicating with said first chamber and a second inlet port communicating with said second chamber, said first and second inlet ports adapted for connection respectively to pressure sources to be monitored,

a spoiler element mounted to said pins of said pressure responsive members for movement therewith,

resonant circuit means including coils surrounding said spoiler element, oscillator means operative to cause resonance of said circuit means and means operative upon connection of said circuit means to an electrical power source to provide an electrical signal indicative of the change in position of said pressure responsive members.

2. A transducer as defined in claim 1 wherein said first and second caps are fastened to said central housing section by crimping.

3. A transducer as defined in claim 1 further comprising a spacer means disposed between said first cap and said central housing and between said second cap and said central housing for limiting compression of said seal means.

4. A transducer as defined in claim 1 further comprising a converter circuit for converting an analog signal to a digital signal.

5. A transducer as defined in claim 1 further comprising a converter circuit for converting a digital signal to an analog signal.

6. A transducer as defined in claim 1 including means for varying the slope of an electrical signal.

7. A transducer as defined in claim 1 including means for providing a square root value of an electrical output signal.

8. A transducer as defined in claim 1 including display means for displaying an electrical output signal in engineering units.

9. A transducer as defined in claim 1 including means for providing an offset to an electrical output signal at zero pressure differential.

10. A differential pressure sensor comprised of:

a housing having first and second spaced apart fluid chamber connectable respectively to first and second fluid pressure sources to be monitored,

a pressure responsive assembly within said housing comprised of first and second pressure sensitive members connected to one another, said first pressure sensitive member being exposed to said first fluid chamber and said second pressure sensitive member being exposed to said second chamber, said pressure responsive assembly mounted to said housing wherein said assembly is moveable along a fixed axis in response to differences in fluid pressure in said first and said second chambers,

an element attached to said pressure responsive assembly for movement therewith, said element disposed between said first and said second pressure sensitive elements and external to said first and said second chambers, and

a non-contacting sensor mounted to said housing adjacent to said element, said sensor being responsive to movement of said element and providing a series of pulses having a frequency indicative of the position of said element.

11. A differential pressure sensor as defined in claim 10 wherein said element is a metallic element and wherein said non-contacting sensor is comprised of a resonant circuit means including coils surrounding said metallic element, oscillator means operative to cause resonance of said circuit means and means operative upon connection of said circuit means to an electrical power source to provide the series of pulses having a frequency indicative of the position of said element.

12. A sensor as defined in claim 11 wherein said pressure responsive assembly is comprised of two pressure responsive members, each of said pressure responsive members including an annular diaphragm element formed of resilient material having a molded outer edge for mounting to said housing.

13. A sensor as defined in claim 12 wherein said pressure responsive assembly engages said housing only along the outer edges of said diaphragm elements.

14. A differential pressure sensor comprised of:

a housing having first and second spaced apart fluid chambers connectable respectively to first and second fluid pressure sources to be monitored, said housing comprised of a plurality of housing sections which are crimped together,

a pressure responsive assembly within said housing comprised of first and second pressure sensitive members connected to one another, said first pressure sensitive member begin exposed to said first fluid chamber and said second pressure sensitive member being exposed to said second chamber, said pressure responsive assembly mounted to said housing wherein said assembly is movable along a fixed axis in response to differences in fluid pressure in said first and said second chambers,

an element attached to said pressure responsive assembly for movement therewithin, said element disposed between said first and said second pressure sensitive elements and external to said first and said second chambers, and

a non-contacting sensor mounted to said housing adjacent to said element, said sensor being responsive to movement to said element and providing electrical signals indication of the position of said element.

15. In a combustion heating system having a heat exchanger, a variable speed inducer motor for creating flow along a path including said heat exchanger, and a transducer for measuring a pressure differential along said path, a method of operating said system comprising the steps of:

establishing a plurality of system operating modes, each of said system operating modes having a predetermined optimum pressure differential value;

sensing a measured pressure differential across the heat exchanger;

providing a first and second series of pulses having a first frequency and second frequency respectively, said first and second frequencies related to the measured pressure differential;

determining a first and second time to count the same number of pulses of each first and second series of pulses respectively;

converting said first and second time into an indication of the measured pressure differential;

computing a deviation between the indication of measured pressure differential and the predetermined optimum pressure differential value; and

varying the velocity of the variable speed inducer motor in accordance with said deviation.

16. The invention of claim 15 further comprising primary burner assembly and a pilot burner;

and wherein said plurality of operating modes includes a pre-purge mode for evacuating fluid from said path after a request for heat has been initiated, an ignition mode for lighting said pilot burner, and a primary ignition mode for igniting said primary burner assembly of the heating apparatus, said pre-purge mode, said ignition mode and said primary ignition mode, each having a different optimum pressure differential value.

17. The invention of claim 15, wherein the velocity of the variable speed inducer motor is varied in steps.

18. The invention of claim 17, wherein the size of said steps vary in accordance with the relative value of the deviation.

19. The invention of claim 15, wherein the velocity of the variable speed inducer motor is varied by adjusting the velocity until a predetermined deviation is obtained.

20. The invention of claim 16, wherein the predetermined pressure differential value for said pre-purge mode is lower than the predetermined pressure differential value for said primary ignition mode.

21. A controller for regulating a combustion flow rate along a path in a combustion system having a heat exchanger and a variable speed inducer motor, said controller comprising:

means for establishing a plurality of operating modes;

means for storing a predetermined optimum pressure differential value for each said operating mode;

sensing means for sensing a measured pressure differential between two locations along said path and for providing a series of pulses having a frequency related to the measured pressure differential;

means for determining a time to count a predetermined number of said pulses and for converting said time into an indication of the measured pressure differential;

calculation means for calculating a deviation between the indication of measured pressure differential and the predetermined optimum pressure differential value; and

means for varying the velocity of the variable speed inducer motor in accordance with the deviation.

22. A heating apparatus as defined in claim 21 wherein said variable speed inducer motor is an SR motor.

23. A heating apparatus including:

a combustion air inlet,

a combustion means for receiving a flow of combustion air and for burning a mixture of combustion air and combustible fluid to produce a combusted fluid air mixture,

a heat exchanger means defining a path for a flow of combusted fluid air mixture therethrough,

a motor-driven means for creating a flow of the combustion air through said combustion means and for providing a flow of the combusted fluid air mixture along said path through said heat exchanger means,

a differential pressure transducer means for determining a difference in pressure between two positions along said path and for providing a series of pulses having a frequency related to said difference in pressure;

a microprocessor control system comprising;

means for converting the series of pulses into an indication of the difference in pressure;

means for storing at least one predetermined pressure differential value;

means for determining a deviation between the indication of difference in pressure and the at least one predetermined pressure differential value; and

means operatively connected to said variable motor-driven means for adjusting the difference in pressure between the two positions along said heat exchanger in accordance with said deviation.

24. A heating apparatus as defined in claim 23 wherein said motor-driven means for creating a flow of the combustion air is driven by a SR motor.

25. A heating apparatus as defined in claim 23, wherein said means for adjusting controls the motor-driven means to adjust the flow of the combustion air, flow of combustible fluid air mixture and flow of combustion byproducts.

26. A control system for monitoring and adjusting a pressure differential value across a fluid flow chamber, said control system comprising:

differential sensor means for sensing a first measured pressure at a first location along the fluid flow chamber and a second measured pressure at a second location along the fluid flow chamber, and providing a series of pulses having a frequency related to the pressure differential value;

means for determining a time to count a predetermined number of said series of pulses and for converting said time into an indication of the measured pressure differential value;

calculation means for calculating a deviation between the indication of measured pressure differential value and a predetermined pressure differential value; and

means for changing the pressure differential value in accordance with said deviation.

27. A control system as defined in claim 26, wherein said means for changing changes the speed of a blower means.

28. A control system as defined in claim 27, wherein said blower means is driven by a SR motor.

29. A controller for regulating a combusted fluid flow rate in a combustion system having a heat exchanger, a variable speed inducer motor, a variable gas flow regulator, said controller comprising:

means for storing a gas pressure differential value and a corresponding air pressure differential value, for a plurality of heat demand values;

first sensing means for sensing a first measured pressure differential across the heat exchanger and for providing series of pulses having a frequency related to the first measured pressure differential,

means for determining a time to count a predetermined number of said series of pulses and for converting said time into a indication of the first measured pressure differential;

second sensing means for sensing a second measured pressure differential across the variable gas flow regulator and for providing a second signal output that is related thereto;

calculation means for calculating a first deviation between the indication of first measured pressure differential and the stored air pressure differential value and a second deviation between the second signal output and the stored gas pressure differential value; and

means for changing the combustion flow rate in accordance with said first and second deviations.

30. A controller as defined in claim 29, wherein said means for changing the combustion flow rate changes the speed of the variable speed inducer motor.

31. A controller as defined in claim 29, wherein said means for changing the combustion flow rate changes the flow of fluid through said fluid flow regulator.

32. A controller for regulating a flow rate of a heat transfer fluid for maximum efficiency, said controller comprising;

means for storing a first flow rate parameter and a corresponding second flow rate parameter, for a plurality of heat transfer parameters;

first sensing means for indicating a first flow rate along a first path and for providing a series of pulses having a frequency related to said first flow rate;

processor means for counting a predetermined number of said series of pulses and for determining an interval of time required to count the same, said processor means converting said interval of time into an indication of the first flow rate;

second sensing means for indicating a second flow rate along a second path and for providing a signal output related thereto, said processor means determining from said signal output an indication of the second flow rate

comparison means for comparing said indication of first flow rate to said stored first flow rate parameter and for comparing said indication of second flow rate to said stored second flow rate parameter for a particular heat transfer parameter; and

means for changing the flow rate of the heat transfer fluid in response to said comparison.

33. A controller for regulating a flow rate of a heat transfer fluid in a heat transfer system, said heat transfer system having a heat transfer fluid flow path, means for creating flow along said path, an air flow path, air flow regulator, a fuel flow path, and a fuel flow regulator, said controller comprising:

means for storing a predetermined fuel pressure differential and a corresponding predetermined heat transfer fluid pressure differential, for a plurality of heat demand values,

first sensing means adapted to measure fuel pressure differential along the fuel flow path at said fuel source and for providing a first output signal indicative thereof;

second sensing means for sensing a measured heat transfer fluid pressure differential along the heat transfer fluid flow path and for providing a series of pulses having a frequency related thereto;

means for converting the first output into an indication of the fuel pressure differential and for converting the series of pulses into an indication of the heat transfer fluid pressure differential;

comparison means for comparing said predetermined fuel pressure differential to said indication of fuel pressure differential and for comparing said predetermined heat transfer fluid pressure differential to said indication of heat transfer fluid pressure differential; and

means for regulating said air flow regulator and said fuel flow regulator in response to said comparison means.

34. A controller as defined by claim 33, wherein said plurality of heat transfer values correspond respectively to a plurality of operating modes.

35. A controller as defined by claim 34, wherein said plurality of operating modes includes a purge mode and a primary heat mode.

36. A controller as defined in claim 33, wherein said first sensing means and said second sensing means are each comprised of a dual diaphragm transducer.

37. A control system for regulating the flow rate of a heat transfer fluid in a heat transfer system, said heat transfer system having a heat transfer fluid flow path, flow control means for creating flow along said path, a fuel source for providing a combustible fuel to said path, an air source for providing combustion air to said path, and means for combusting said fuel and air to create said heat transfer fluid, said control system comprising:

means for storing a fuel flow value and a corresponding air flow value for a plurality of heat transfer values;

first sensing means for sensing a measured flow value at said fuel source and providing a first signal output related thereto;

second sensing means for sensing a measured flow value at said air source and providing a series of pulses having a frequency related thereto;

means for determining a time to count a predetermined number of pulses and for converting said time into an indication of the flow value at said air source, said determining means converting said first signal output into an indication of the flow value at said fuel source;

comparison means for comparing said stored fuel flow value to said indication of flow value at said fuel source, and for comparing said stored air flow value to said indication of flow value at said air source;

fuel regulating means for regulating said fuel flow at said fuel source; and

means for adjusting said fuel regulating means and said flow control means in response to said comparison means.

38. A control system as defined in claim 37 wherein said fuel regulating means is a variable flow regulator.

39. A control system as defined in claim 38 wherein said first sensing means is a differential pressure sensor sensing pressure across said regulator.

40. A control system as defined in claim 37 wherein said second sensing means senses a pressure differential along said heat transfer fluid flow path.

41. A control system as defined in claim 37 wherein said second sensing means is a dual diaphragm transducer.

42. A control system as defined in claim 37 wherein said first and second sensing means are continuous output sensing devices.

43. A control system for regulating the flow rate of a heat transfer fluid in a heat transfer system, said heat transfer system having a heat transfer fluid flow path, flow control means for creating flow along said path, a fuel source for providing a combustible fuel to said path, an air source for providing combustion air to said path, and means for combusting said fuel and air to create said heat transfer fluid, said control system comprising:

sensing means for sensing a measured flow value at said air source and for producing a series of pulses having a frequency related to said sensed flow value;

means for determining an interval of time to count a predetermined number of pulses from said series of pulses and for converting said interval of time into an indication of the measured flow value;

means for storing an optimum flow value at said air source;

means for storing a range of operating control values for said flow control means, said operating control values corresponding to said optimum flow value;

calculation means for calculating a deviation between said indication of measured flow value and said optimum flow value; and

means for varying the operation of said flow control means in accordance with said deviation.

44. A control system as defined in claim 43 wherein said sensing means is a differential pressure transducer and measures a pressure differential between two locations along said heat transfer fluid flow path.

45. A control system as defined in claim 44 wherein said heat transfer system is a gas furnace having a heat exchanger defining said heat transfer fluid flow path.

46. A control system as defined in claim 43 wherein said heat transfer system includes a plurality of operating modes, each of said modes having an optimum flow value and a corresponding range of operating control values.

47. A control system as defined in claim 43 wherein said flow control means is an inducer blower and said operating control values relate to the speed of said inducer blower.

48. A control system as defined in claim 47 wherein said inducer blower is driven by an SR motor.

49. A control system as defined in claim 43, wherein said means for varying the operation of said flow control means includes means for terminating operation of said heat transfer system.

50. A control system as defined in claim 43, wherein said means for varying the operation of said flow control means includes alarm means for indicating that said flow control means is operating outside said range of operating control values.

51. A control system as defined in claim 43, wherein said means for varying the operation of said flow control means includes means for limiting operation of said flow control means to said range of operating control values.

52. A heating apparatus including:

a combustion air inlet,

a combustion means for receiving a flow of combustion air and for burning a mixture of combustion air and combustible fluid to produce a combusted fluid air mixture,

a heat exchanger means defining a path for a flow of combusted fluid air mixture therethrough,

a flow device for creating a flow of the combustion air through said combustion means and for providing a flow of the combusted fluid air mixture along said path through said heat exchanger means,

an SR motor for driving said flow device,

a differential pressure transducer for determining a pressure value at two positions along said path and providing a series of pulses having a frequency related to the pressure values,

a microprocessor control system for controlling said SR motor, said control system determining a time to count a predetermined number of said series of pulses and for converting said time into an indication of the measured pressure differential, said control system monitoring any deviation between the indication of the measured pressure differential value provided by the continuous differential pressure transducer means and a predetermined pressure differential value, and adjusting the speed of said SR motor in response thereto.