Stack damper
A damper comprising a duct defining an air flow path, opposing damper blades pivotally mounted within the duct, each damper blade having an end that is pivotally mounted in cantilevered fashion in the duct so that an opposing end is free to move within the duct, wherein each damper blade is planar in shape, cooperating flow straightening members disposed centrally in the air flow path, an air flow sensor for generating a signal cooperatively disposed between the flow straightening members, and an actuator for pivoting each damper blade within the duct in response to the signal from the air flow sensor to vary the damper blade position and thereby maintain a desired velocity of air exiting the damper.
The invention relates to a stack damper, and more particularly, to a stack damper which automatically maintains a downstream air flow velocity by adjusting a damper blade position in response to an air flow signal.
BACKGROUND OF THE INVENTIONSuitable air flow velocity is a widely accepted means of maintaining entrainment of air borne contaminants. To this end various environmental rules require that air exiting from an exhaust stack or duct be discharged into the air at a predetermined height (or some calculated distance from intake ducts) and a predetermined velocity to ensure proper diffusion.
One problem presented by this regulatory regime is the large constant volume of air which must be discharged to maintain proper velocity.
Compounding the problem is the volume of air which is required to be discharged varies during the day. For instance, the volume of discharged air could be reduced dramatically during off hours. On the other hand, regulations often require the velocity of discharged air to remain the same throughout the day. This often requires that ambient air be pumped into the stack to ensure constant discharge velocity. This in turn substantially increases the associated energy costs required to run the facility, even though the percentage of entrained contaminants may be very small.
It would be advantageous if the energy costs associated with the maintenance of a high velocity discharge could be reduced by reducing the amount of ambient air required to maintain the desired discharge velocity.
Representative of the art is U.S. Pat. No. 6,071,188 (2000) which discloses an exhaust system has an air exhaust duct having a charge opening and a discharge opening and defining an air flow path. A damper is mounted in the duct for maintaining a constant air velocity for air exiting the discharge opening. The damper has opposing damper blades pivotally mounted within the duct. Each damper blade has an end that is pivotally mounted in cantilevered fashion within the duct so that an opposing end is free to move within the duct. Each damper blade is parabolic in shape and minimizes the air turbulence over the damper blade and reduces vibration. Each damper blade can be pivoted in response to a change in air volume discharged through the discharge opening to maintain a desired velocity of air through the discharge opening.
What is needed is a stack damper which automatically maintains a downstream air flow velocity by adjusting a damper blade position in response to an air flow signal. The present invention meets this need.
SUMMARY OF THE INVENTIONThe primary aspect of the invention is to provide a stack damper which automatically maintains a downstream air flow velocity by adjusting a damper blade position in response to an air flow signal.
Other aspects of the invention will be pointed out or made obvious by the following description of the invention and the accompanying drawings.
The invention comprises a damper comprising a duct defining an air flow path, opposing damper blades pivotally mounted within the duct, each damper blade having an end that is pivotally mounted in cantilevered fashion in the duct so that an opposing end is free to move within the duct, wherein each damper blade is planar in shape, cooperating flow straightening members disposed centrally in the air flow path, an air flow sensor for generating a signal cooperatively disposed between the flow straightening members, and an actuator for pivoting each damper blade within the duct in response to the signal from the air flow sensor to vary the damper blade position and thereby maintain a desired velocity of air exiting the damper.
The accompanying drawings, which are incorporated in and form a part of the specification, illustrate preferred embodiments of the present invention, and together with a description, serve to explain the principles of the invention.
Damper blade 50 is attached in a cantilever fashion to damper shaft 30. Damper blade 51 is attached in a cantilever fashion to damper shaft 40. Vane 52 is fixedly connected between sides 10 and 13. Vane 52 is fixedly connected between sides 10 and 13. Vanes 52 and 53 are substantially parallel. Damper blades 50 and 51 are substantially parallel. Damper blades 50, 51 and vanes 52 and 53 are substantially flat (planar).
Damper blades 50 and 51 move in unison and express substantially the same position with respect to the air flow through the damper.
Air flow measuring sensor 60 is disposed between vanes 52 and 53. Sensor 60 senses air flow through the damper. Vanes 52 and 53 act as air flow straightening members to improve the measurement accuracy of sensor 60 by reducing turbulence near the sensor. Vanes 52, 53 are substantially parallel to the air flow direction. Vanes 52 and 53 also serve to reduce turbulence and vibration in the duct caused by damper blades 50, 51 when they are in the partially closed or closed position.
Skirt 15 and flange 16 are attached to an end 17 of the damper in an air tight manner to avoid air leakage. Flange 16 receives fasteners such as bolts to attach the damper to ductwork (not shown).
Linkage arm 21 is connected to a damper shaft 30. Linkage arm 22 is connected between damper shaft arm 23 and damper shaft arm 24. Damper shaft arm 24 is connected to damper shaft 40.
Actuator 20 moves the damper blades 50, 51. Actuator 20 may comprise any suitable device known in the art, including an electric motor or air piston. In this embodiment, air piston 20 is connected to a pressurized air source (not shown) and controller 603, see
Although a form of the invention has been described herein, it will be obvious to those skilled in the art that variations may be made in the construction and relation of parts without departing from the spirit and scope of the invention described herein.
Claims
1. A damper comprising:
- a duct defining an air flow path;
- opposing damper blades pivotally mounted within the duct, each damper blade having an end that is pivotally mounted in cantilevered fashion in the duct so that an opposing end is free to move within the duct, wherein each damper blade is planar in shape;
- cooperating flow straightening members disposed centrally in the air flow path;
- an air flow sensor for generating a signal cooperatively disposed between the flow straightening members; and
- an actuator for pivoting each damper blade within the duct in response to the signal from the air flow sensor to vary the damper blade position and thereby maintain a desired velocity of air exiting the damper.
2. A damper according to claim 1 wherein said actuator comprises a pneumatic piston engaged with a damper blade shaft.
3. The damper according to claim 1 further comprising a controller operatively connected to the sensor and the actuator for automatically controlling pivotal movement of each damper blade in response to the measured change in the air flow so as to maintain a substantially constant discharge air velocity.
Type: Application
Filed: Nov 9, 2007
Publication Date: May 14, 2009
Inventor: Robert M. Van Becelaere (Lake Lotawana, MO)
Application Number: 11/983,647
International Classification: F24F 13/16 (20060101); F24F 13/10 (20060101);