Patent Application
20190309941
This invention relates generally to burner nozzles and, more particularly, to high turndown ratio gaseous fuel burner nozzles, also referred to herein as high turndown ratio gas burner nozzles, and the control thereof.
Typical burner nozzle operation is limited by low turndown ratio due to the use of a fixed port size on the gas burner nozzle. The fixed gas port size in a typical burner nozzle design results in combustion having a limited modulation range resulting in the burner being completely shutdown at low heat demand and then restarted to reduce the heat produced at low demand. Each re-fire of a burner results in additional heat losses due to safety purge requirements and equipment restart. Such on-off type of control at low heat demand also increases the duty of gas train components such as blocking valves which by code require a double block and bled that vents natural gas to the atmosphere.
Thus, there is a need and demand for a high turndown gas burner nozzle design such as would allow for single start up firing and greatly improved heat low matching of the burner to the heat demand.
Further, issues associated with conventional burner nozzle designs are mostly commonly centered on flame stability and noise. In normal burner operation, the speed of the air/gas mixture is somewhat higher than the flame speed. In such operation, the flame desirably stays anchored at or in the nozzle.
The velocity of primary air/gas flow from a nozzle can, however, increase at higher firing rates and can be greater than the flame speed. Under this condition, the flame lifts off from the burner nozzle and the flame burns at an elevated location spaced from the outer face of the burner nozzle. Operation of a burner under these conditions is a major cause of the burner noise associated with burner nozzles. On the other hand, operation under conditions with the velocity of the air/gas mixture being too slow, as compared to the flame speed, can undesirably result in the burning of the fuel air mixture within the burner nozzle itself. This condition can cause overheating and result in deterioration of the nozzle.
Thus, there is a need and demand for improvements in nozzle design, operation and control such as to allow a burner to operate at or near optimal conditions over a range of firing rates and such as resulting in one or more of:
In accordance with one aspect of the subject development the invention provides a burner nozzle for natural gas, propane, hydrogen, or any other combustible gas, the burner nozzle having a mechanically adjustable port for expanded turndown control.
In accordance with another aspect of the subject development the invention provides methods or techniques for adjusting a mechanically adjustable nozzle port such as in the form of a mechanically adjustable iris port of a gaseous fuel burner nozzle.
A gaseous fuel burner nozzle in accordance with one embodiment desirably includes a mechanically adjustable iris nozzle port for expanded turndown control. The nozzle further includes a cylindrical nozzle extension longitudinally extending from and shaping flow of combustible gas from the mechanical adjustable iris nozzle port. The cylindrical nozzle extension including a laminar flow insert housed therewithin. The laminar flow insert desirably produces laminar flow of the combustible gas flowing therethrough.
In accordance with another embodiment, there is provided a gaseous fuel burner nozzle that includes a mechanically adjustable iris nozzle port for expanded turndown control. The burner nozzle also includes a cylindrical nozzle extension longitudinally extending from and shaping flow of combustible gas from the mechanical adjustable iris nozzle port. The cylindrical nozzle extension includes a laminar flow insert housed therewithin. The laminar flow insert desirably serves to result in or produce a laminar flow of the combustible gas flowing therethrough. The cylindrical nozzle extension includes a nozzle sidewall having a first proximal end portion disposed adjacent the mechanically adjustable iris nozzle port and an opposed second distal end portion forming a discharge end of the burner nozzle. In one preferred embodiment, the nozzle wall includes a plurality of recirculation ports disposed in the second distal end portion. The recirculation ports desirably serve to allow internal recirculation of at least a portion of exhaust gas produced by operation of the gaseous fuel burner nozzle. The burner nozzle further includes a burner nozzle controller in control communication with the mechanically adjustable iris nozzle port. The controller can desirably serve to adjust the size of the nozzle port to selectively maintain exit velocity of the gaseous fuel from the nozzle port for one or more of combustion stability and flame stability.
Objects and features of this invention will be better understood from the following description taken in conjunction with the drawings, wherein:
The invention provides a gaseous fuel burner nozzle, such as in the form of either an overlapping or non-overlapping mechanically adjustable iris port, for expanded turndown control of a gaseous fuel, e.g., natural gas.
While the invention is described in greater detail below making specific reference to a gaseous fuel burner nozzle having or including a mechanically adjustable nozzle port in the form of a mechanically adjustable iris port, those skilled in the art and guided by the teachings herein provided will understand and appreciate that the broader practice of the invention is not necessarily limited to or with practice of an iris port, as other shapes or forms of mechanically adjustable nozzle ports may be suitably utilized in the practice of the invention and are herein encompassed.
Turning to
As identified above and in accordance with one preferred practice of the subject invention, the mechanical iris port can be desirably controlled/adjusted either by entry of pressure measurement or fuel gas and/or oxidant, e.g., combustion air, burner control signals and can be done in or through an open or close loop control system to maintain sufficient exit velocity such as required for stable combustion and flame stability.
Turning now to
The high turndown ratio gaseous fuel burner nozzle assembly 210 primarily differs from the assembly 110 by the inclusion or incorporation of a nozzle extension 230, with the nozzle extension 230 shown in further detail in
In accordance with one preferred embodiment, the nozzle extension is a static device and there is no linkage to the stepper motor/actuators. The single stepper motor, servo motor, or actuator and linkage or the like will generally serve to control the iris port opening size with the nozzle extension shaping the flow exiting the iris opening. The use of a nozzle extension desirably serves to move the flame and the associated higher temperatures away from mechanically adjustable port and thus allowing for reduced temperatures and wider selection of material of construction.
The mechanical nozzle port size can desirably be controlled based on parameters such as gas entry pressure to the nozzle; measurement of combustion gas flows; or position sensors of the combustion gas flow control valves. The nozzle controller would provide the signal to the stepper motor, servo motor, or actuator to adjust the required port size to maintain the optimal exit velocity required for desired flame performance and stable combustion.
If desired and as shown in accordance with one preferred embodiment, a laminar flow insert 250 can desirably be at least in part housed within the nozzle extension 230. The laminar flow insert 250 desirably serves to produce or result in laminar flow of the combustible gas flowing through the laminar flow insert 250 and the nozzle extension 230 and out from the assembly 210.
In accordance with one preferred embodiment, the laminar flow insert is desirably shaped or formed by a plurality of parallel narrow diameter tubes 252 such as in the form of a bundle and such as generally extending from the first or proximal end portion 234 to or towards the opposed second or distal end portion 236.
In one preferred practice of the invention, the inclusion and use of a laminar flow insert such as herein described will facilitate and/or allow the flow of the combustible gas to be tailored to achieve or result in desired flame shapes. Also the use of the extension may allow use of more conventional control type of mechanisms that do not necessarily produce a round shaped port opening such as a simple gate or shudder as the extension and flow insert will provide for shaping the flow exiting the port.
As will be appreciated by those skilled in the art and guided by the teaching herein provided, the laminar flow insert can be various forms or design to produce or result in laminar flow of the combustible gas flowing therethrough and the broader practice of the invention is not necessarily limited to or by the shape, form or construction of the laminar flow insert.
If desired and as shown, the nozzle extension sidewall 232 may include a plurality of recirculation ports 260 disposed in the second or distal end portion 236. The recirculation ports 260 desirably can serve to allow internal recirculation of at least a portion of exhaust gas produced by operation of the gaseous fuel burner nozzle. As shown, the laminar flow insert 250 may end short of the full length of the nozzle extension sidewall 232. Further the recirculation ports 260 can be spaced, and in one embodiment uniformly spaced, about the sidewall 232 at a margin portion 262 of the nozzle extension 230 extending beyond the length of the laminar flow insert 250.
While the illustrated embodiment depicts the recirculation ports 260 as being of generally uniform shape, size and spacing, the broader practice of the invention is not necessarily so limited. For example, those skilled in the art and guided by the teachings herein provided will understand and appreciate that, if desired, not only the number of recirculation ports but also parameters such as including shape, size, and spacing can be specifically tailored for particular or specific applications.
Turning to
The high turndown ratio gaseous fuel burner nozzle assembly 310 includes or incorporates a nozzle extension 330 such as includes, contains or have associated therewith a sealing mounting flange 342 and such as may serve to permit or facilitate attachment or placement of the nozzle extension 330 into operational placement relative to the mechanically adjustable nozzle port 314.
The nozzle extension 330 further at least in part houses or contains a laminar flow insert 350. As shown, the laminar flow insert 350 desirably serves to produce or result in laminar flow of the combustible gas flowing through the laminar flow insert 350 and the nozzle extension 330 and out from the assembly 310.
The nozzle extension 330 further include a plurality of recirculation ports 360 such as may serve, as described above, to allow internal recirculation of at least a portion of exhaust gas produced by operation of the gaseous fuel burner nozzle, such as shown in
As will be appreciated by those skilled in the art and guided by the teachings herein provided, high turndown gas burner nozzle design can allow for single start up firing and greatly improved heat flow matching of the burner to the heat demand.
Such designed combustible gas burners can desirably provide or result in:
More specifically, for example, the added capability to control the nozzle port size during operation will facilitate and permit burner operation at or near optimal conditions over a range of firing rates resulting in satisfaction or one or more and preferably each of the following operational results: stable performance across a broader range of burner firing rates; increased turndown performance with a target of greater than 20:1; and reduced emissions across firing rates compared to a fix port nozzle through increased flame control from the adjustable port size of the burner nozzle.
Further, the incorporation and utilization of mechanically adjustable nozzle ports such as herein provided enables and facilitates utilization of advanced operational controls, such as the adaptive control modules currently used in the automotive industry to adjust to maintain performance and emissions limits.
Thus in accordance with at least selected embodiments, the invention desirably results or produces improvements in efficiency and overall burner nozzle performance as well as reduction in emissions across a wider operating range as compared to the current fix port nozzles burners design.
While, as compared to fixed port burner nozzles, increased costs may result from increased complexity of the nozzle design and to the controls required for proper operation, as a result of the recent acceleration in development of motion control technology for automation these components have dramatically decreased in cost and can be expected to continue to do so in the foreseeable future.
While the invention has been described above making specific reference to embodiments employing natural gas as the fuel or combustible gas, the broader practice of the invention is not necessarily so limited. For example, if desired, the invention can be applied or practiced in conjunction with or using other fuel or combustible gas including propane, methane and hydrogen, for example.
While in the foregoing detailed description this invention has been described in relation to certain preferred embodiments thereof, and many details have been set forth for purposes of illustration, it will be apparent to those skilled in the art that the invention is susceptible to additional embodiments and that certain of the details described herein can be varied considerably without departing from the basic principles of the invention.
This application claims the benefit of U.S. Provisional Patent Application, Ser. No. 62/654,880, filed on 9 Apr. 2018. This co-pending Provisional Application is hereby incorporated by reference herein in its entirety and is made a part hereof, including but not limited to those portions which specifically appear hereinafter.
| Number | Date | Country | |
|---|---|---|---|
| 62654880 | Apr 2018 | US |
