DESC:FIELD OF INVENTION
The present disclosure generally relates to a fan system having parallelly disposed axial fans to transport solid fuels, such as coal. More particularly, the disclosure relates to a stall detection system having sensors that facilitate the determination of a stall condition in one or more of the axial fans of the fan system.
BACKGROUND
Solid fuel (such as coal) powered power plants generally include a plurality of axial fans, generally referred as primary fans, to transport solid fuel from one or more pulverizers to a boiler. The axial fans generally generate an air flow by which the solid fuel is carried to the boiler. In certain situations, due to a resistance of pipes or any other obstruction present downstream of the axial fans, the axial fans may encounter a stall condition. Because of such stall conditions, a transfer of the solid fuel to the boiler may be impeded, and also, the stall condition may damage the axial fans, and/or other components. Therefore, it may be desirable to detect and control stalling of the axial fans.
SUMMARY
One aspect of the present disclosure relates to a stall detection system for a fan system having a plurality of fans that facilitate transport of a solid fuel to a boiler along an air flow generated by the plurality of fans. The stall detection system includes a plurality of sensors correspondingly disposed downstream to the plurality of fans along the air flow. Each sensor of the plurality of sensors includes a base, a first tube and a second tube extending from the base. The first tube defines a first opening inclined to at least partially face and receive air pressure from a corresponding fan of the plurality of fans. The second tube includes a second opening to receive air pressure generated by one or more fans of the plurality of fans. A difference between the air pressure received through the first opening and the air pressure received through the second opening facilitates determination of a stall condition of one or more fans of the plurality of fans.
Another aspect of the present disclosure relates to a fan system for a boiler. The fan system includes a plurality of fans, a controller, and a plurality of sensors. The fans generate and deliver air flow to a header. The header is adapted to receive and direct the air flow over and across a bed of a pulverized form of a solid fuel to transport the pulverized form of the solid fuel to the boiler along with the air flow. The controller is configured to control one or more of the plurality of fans to generate air flow and regulate the air pressure of the header based on a stall condition of one or more fans of the plurality of fans and the air pressure within the header. Further, the sensors are coupled to the controller and are correspondingly disposed downstream to the fans along the air flow. Each sensor includes a base, a first tube and a second tube extending from the base. The first tube defines a first opening inclined to at least partially face and receive air pressure from a corresponding fan. The second tube includes a second opening to receive air pressure generated by one or more fans, wherein a difference between the air pressure received through the first opening and the air pressure received through the second opening facilitates determination of a stall condition of one or more fans.
BRIEF DESCRIPTION OF DRAWINGS
FIG. 1 is a diagrammatic view of a fan system having a pair of parallelly disposed axial fans, in accordance with an embodiment of the present disclosure;
FIG. 2 is a perspective view of a first sensor of the fan system, in accordance with an embodiment of the present disclosure; and
FIG. 3 is a flowchart illustrating a method of detecting and controlling a stall condition of the pair of parallelly disposed axial fans of the fan system, in accordance with an embodiment of the present disclosure.
DETAILED DESCRIPTION
Referring to FIG. 1, a fan system 100 is shown. The fan system 100 may be utilized as primary fan system for facilitating the transport of a solid fuel, such as coal, to a boiler 103 of a power plant. Although, the fan system 100 is contemplated as a primary fan system for the boiler 103, it may be appreciated that the fan system 100 may be utilized in any other application for providing/generating air flow. The fan system 100 may include multiple fans, such as axial fans (i.e., defined according to the direction of air flow generated by the fans). For example, the fan system 100 may include a first axial fan 102 and a second axial fan 104. The second axial fan 104 may be disposed parallel to the first axial fan 102. Although a pair of axial fans (i.e., the first axial fan 102 and the second axial fan 104) is disclosed, additional axial fans (e.g., disposed parallelly to each other) may also be contemplated. Further, it will be appreciated that the aspects of the present disclosure may be applied to various other fan types and configurations.
Details of the fan system 100 will now be explained. The fan system 100 may include a first inlet conduit 106 fluidly coupled to the first axial fan 102, and a second inlet conduit 108 fluidly coupled to the second axial fan 104. The first inlet conduit 106 and the second inlet conduit 108 may respectively be configured to facilitate a flow of air to the first axial fan 102 and the second axial fan 104 from an ambient 105. The fan system 100 further includes multiple conduits or ducts that fluidly and correspondingly extend from the first axial fan 102 and the second axial fan 104 to receive the air flow and route the air flow to a header 120. For example, a first outlet duct 110 and a second outlet duct 112 are respectively (and fluidly) coupled to an outlet 114 of the first axial fan 102 and an outlet 116 of the second axial fan 104. The first outlet duct 110 and the second outlet duct 112 may respectively be configured to facilitate a flow of air exiting the first axial fan 102 and the second axial fan 104 to be directed or routed to a header 120. For example, the first outlet duct 110 and the second outlet duct 112 correspondingly receive air pressure from the first axial fan 102 and the second axial fan 104 and deliver said air pressure to the common header 120. In this regard, the header 120 may be fluidly coupled to each of the first outlet duct 110 and the second outlet duct 112 to receive air (or air pressure) from the first outlet duct 110 and the second outlet duct 112. The header 120 may further facilitate a flow of air received from both the first outlet duct 110 and the second outlet duct 112 to be directed over and across a bed (not shown) of pulverized form of the solid fuel (e.g., coal) so that the pulverized form of the solid fuel may be transported to the boiler 103 along with the air flow.
Both the first axial fan 102 and the second axial fan 104 may respectively include a plurality of rows of blades. Such rows of blades may facilitate the control of a velocity, a volume, and/or a pressure of air flow downstream of each of the first axial fan 102 and the second axial fan 104. For example, the first axial fan 102 may include a first row of blades 122 and a second row of blades 124. The second row of blades 124 may be disposed at a distance and downstream to the first row of blades 122, along a direction, C, of an air flow. The first row of blades 122 may include variable pitch blades, while the second row of blades 124 may include fixed pitch blades. Although the first axial fan 102, having one row of variable pitch blades and one row of fixed pitch blades are shown, it may be appreciated, the first axial fan 102 may include any number of rows of variable pitch blades and any number of rows of fixed pitch blades. For example, the first axial fan 102 may include two rows of variable pitch blades and / or two rows of fixed pitch blades.
Similarly, the second axial fan 104 may include a third row of blades 128 and a fourth row of blades 130. The fourth row of blades 130 may be disposed at a distance and downstream of the third row of blades 128 along a direction, D, of air flow. The third row of blades 128 may include variable pitch blades, while the fourth row of blades 130 may include fixed pitch blades. Although the second axial fan 104 having one row of variable pitch blades and one row of fixed pitch blades are shown, it may be appreciated, the second axial fan 104 may include any number of rows of variable pitch blades and any number of rows of fixed pitch blades. For example, the second axial fan 104 may include two rows of variable pitch blades and / or two rows of fixed pitch blades.
For each of the first axial fan 102 and the second axial fan 104, the variable pitch blades are the blades whose angle of pitch may be manipulated by operating a pitch control mechanism for controlling an amount of air flow across the axial fan. Such pitch control mechanisms are well known in the art, and thus will not be discussed.
The fan system 100 may further include a stall detection system 139 having a plurality of sensors, for example, a first sensor 140 and a second sensor 142, for monitoring air pressures in the respective first outlet duct 110 and the second outlet duct 112 owing to the air flow respectively provided by the first axial fan 102 and the second axial fan 104 into the first outlet duct 110 and the second outlet duct 112. For example, the first sensor 140 may be associated with the first axial fan 102 and may be disposed in the first outlet duct 110 (relatively proximate to the outlet 114 of the first axial fan 102), while the second sensor 142 may be associated with the second axial fan 104 and may be disposed in the second outlet duct 112 (relatively proximate to the outlet 116 of the second axial fan 104). The term ‘relatively proximate’, as applied here, means that the first sensor 140 may be disposed at a distance of up to 1 meter from the outlet 114 and that the second sensor 142 may be disposed at a distance of up to 1 meter from the outlet 116.
The first sensor 140 may be configured to measure a static pressure (Ps1) of air and a dynamic pressure (Pd1) of air downstream to the first axial fan 102, while the second sensor 142 may be configured to measure a static pressure (Ps2) of air and a dynamic pressure (Pd2) of air downstream to the second axial fan 104. Both the first sensor 140 and the second sensor 142 are similar in working and structure and may be mounted similarly to the first outlet duct 110 and the second outlet duct 112, respectively. For brevity, a structure of the first sensor 140 and an assembly and working of the first sensor 140 vis-à-vis the first outlet duct 110 and the first axial fan 102 is discussed. Such discussions may be applicable for the structure of the second sensor 142 and an assembly and working of the second sensor 142 vis-à-vis the second outlet duct 112 and the second axial fan 104, as well. Further, annotations and/or reference numerals provided for the first sensor 140 may be applicable for the second sensor 142 as well.
Referring to FIG. 1 and FIG. 2, the first sensor 140 may include a base 150 and a pair of (generally upstanding and parallel) tubes, including a first tube 152 and a second tube 154, each extending outwardly from the base 150. A height of the first tube 152 from the base 150 may be greater than a height of the second tube 154 from the base 150 (or the first tube 152 may be longer than the second tube 154).
The first tube 152 may define a first end 156 attached to the base 150 and a second end 158 disposed away from the base 150. The first tube 152 may be a cylindrical tube defining a longitudinal axis 200 and may define an elongated linear profile extending from the first end 156 all the way to the second end 158. The second end 158 of the first tube 152 may be a free end and may define a first opening 160 of the first tube 152. As shown in FIGS. 1 and 2, the first opening 160 is defined by an edge 163 disposed at the second end 158 of the first tube 152. The edge 163 may be disposed in and along a virtual plane 165 that may be tilted at an angle ‘A’ to the longitudinal axis 200 as the first tube 152 is viewed for elevation from any lateral side of the first tube 152 (e.g., see orientation of the first tube 152 in FIG. 1). The titled nature of the virtual plane 165 imparts an inclination to the edge 163, and thus to the first opening 160 in relation to the inflowing air from the first axial fan 102, thereby allowing portions of the inflowing air from the first axial fan 102 to relatively easily enter the first tube 152. For example, the first opening 160 is inclined to at least partially face the outlet 114 through which a corresponding fan (i.e., the first axial fan 102) delivers air into the first opening 160. In an embodiment, the angle ‘A’ may take any value between 40 degrees and 50 degrees. In some embodiments, the angle ‘A’ may be 45 degrees.
If the first tube 152 were to have a circular cross-section, the first opening 160 may be ovular or oblong in shape, as shown in FIG. 2. Nonetheless, it may be noted that the cross-section of the first tube 152 is not restricted to a circular shape. For example, the first tube 152 may include a square shaped cross-section, a rectangular shaped cross-section, or a polygonal shaped cross-section. Accordingly, the shape of the first opening 160 also need not be restricted to being ovular or oblong.
Further, the second tube 154 may also be a cylindrical tube defining an elongated linear profile and a longitudinal axis 206. The longitudinal axis 206 may be parallel to the longitudinal axis 200 (i.e., the first tube 152 may be parallel to the second tube 154). Also, a height of the second tube 154 may be lesser than a height of the first tube 152 from the base 150 (or the second tube 154 may be shorter than the first tube 152). The second tube 154 defines a first end 162 attached to the base 150, and a second end 164 disposed away from the base 150. As with the second end 158, the second end 164 is a free end of the second tube 154 and defines a second opening 166 to facilitate an entry of air inside the second tube 154. Given that the second tube 154 is shorter than the first tube 152, the second opening 166 of the second tube 154 may stop short of the first opening 160 of the first tube 152 along an elevation of the second tube 154 from the base 150, or, in other words, the second opening 166 may be lower in elevation than the first opening 160 from the base 150.
When compared to the first opening 160 of the first tube 152, the second opening 166 of the second tube 154 is defined by an edge 167 disposed at the second end 164 of the second tube 154. The edge 167 may be disposed in and along a virtual plane 169 that may be tilted at an angle ‘B’ to the longitudinal axis 206 as the second tube 154 is viewed for elevation from any lateral side of the second tube 154 (see orientation of the second tube 154 in FIG. 1). Although not limited, the angle ‘B’ may take any value between 85 degrees and 95 degrees. In an embodiment, angle ‘B’ equals 90 degrees, as depicted in FIG. 1, and, accordingly, the virtual plane 169 may be disposed generally perpendicularly to the longitudinal axis 206. The term ‘generally’, and the like, as used here and elsewhere in the application, may indicate machining tolerances.
If the second tube 154 were to have a circular cross-section, the second opening 166 may be circular in shape, as well, as shown in FIG. 2. Nonetheless, it may be noted that the cross-section of the second tube 154 is not restricted to a circular shape. For example, the second tube 154 may include a square shaped cross-section, a rectangular shaped cross-section, or a polygonal shaped cross-section. Accordingly, the shape of the second opening 166 also need not be restricted to being circular.
In some embodiments, one or both the first tube 152 and the second tube 154 may be made from stainless steel. In some embodiments, one or both the first tube 152 and the second tube 154 may include a diameter less than or equaling 6 millimetres.
It may be noted that the longitudinal nature of the first tube 152 and the second tube 154 (i.e., for the first tube 152 and the second tube 154 to be respectively defined along the longitudinal axes 200, 206) allows the first sensor 140 to be easily assembled and disassembled from the first outlet duct 110, and, thus, facilitates easy maintenance and service of the first sensor 140. The longitudinal nature of the first tube 152 and the second tube 154 also refrains the first sensor 140 from interference with wirings, lines, etc., that may need to be passed in and/or around the first outlet duct 110.
Further, the air pressure received through the first opening 160 may correspond to the dynamic pressure (Pd1) of air generated by the first axial fan 102, while the air pressure received through the second opening 166 may correspond to the static pressure (Ps1) of air generated by one or more of the first axial fan 102 and the second axial fan 104. A difference between the air pressure received through the first opening 160 and the air pressure received through the second opening 166 (i.e., a difference between the dynamic pressure of air, Pd1, and the static pressure of air, Ps1) facilitates determination of a stall condition of the first axial fan 102 (and/or the second axial fan 104). Similar discussions may be contemplated corresponding to the second sensor 142, as well.
According to some embodiments of the present disclosure, the base 150 includes a differential pressure transmitter 174 (or simply, transmitter 174 hereinafter) adapted to detect the difference between the air pressure received through the first opening 160 and the air pressure received through the second opening 166. In one example, the transmitter 174 may include a diaphragm that may divide a chamber defined within the base 150 into a first chamber portion and a second chamber portion. The first chamber portion may receive air pressure from the first opening 160, while the second chamber portion may receive air pressure from the second opening 166. Accordingly, air pressure may impinge upon the diaphragm from either of the sides of the diaphragm. An ensuing differential pressure between the first chamber portion and the second chamber portion may cause the diaphragm to either compress or expand.
Such compression or expansion of the diaphragm may be measured by resistors, for example, mounted on the diaphragm, since the resistance of such resistors may change owing to the diaphragm’s compression / expansion. Such resistance changes may be measured (e.g., by way of Wheatstone bridge principles) and may be further used to determine the differential pressure between the first chamber portion and the second chamber portion, and in turn, of the air flowing or passing through the first outlet duct 110.
Optionally or additionally, the first sensor 140 may include a first detector 170 disposed inside the first tube 152 and a second detector 172 disposed inside the second tube 154. In certain implementations, both the first detector 170 and the second detector 172 may be pressure sensors configured to measure or sense the pressure of air entering the first tube 152 and the second tube 154, respectively. The first tube 152 with the first detector 170 may facilitate detection of a dynamic pressure (Pd1) of air in the first outlet duct 110 (or the air inflowing through the first opening 160). Further, as the first opening 160 is titled or angled (according to angle ‘A’), the configuration of the first tube 152 may mitigate any reduction in pressure of air inflowing from the first axial fan 102 before the air reaches the first detector 170. In case the first sensor 140 were to use the transmitter 174, the first detector 170 and the second detector 172 may be altogether omitted.
In an assembled position of the first sensor 140 with the first outlet duct 110, the first tube 152 may protrude (e.g., normally) into the first outlet duct 110 through a wall 171 of the first outlet duct 110, and, in certain scenarios, the second end 158 of the first tube 152 may extend radially anywhere up to a central longitudinal axis 210 defined by the first outlet duct 110. In that manner, the first opening 160 extends into the first outlet duct 110 and may be disposed relatively proximate to the central longitudinal axis 210. Since the first opening 160 of the first tube 152 may be tilted or inclined towards the first axial fan 102 in the assembled position of the first sensor 140 with the first outlet duct 110, the first opening 160 may facilitate a relatively restriction free entry of air into the first tube 152.
Further, in the assembled position of the first sensor 140 with the first outlet duct 110, the second opening 166 of the second tube 154 may sit flush with an inner surface 180 of the wall 171. In certain embodiments, the second end 164 of the second tube 154 may extend into the first outlet duct 110 and may be disposed beyond the inner surface 180. However, in such cases, it may be appreciated that an extension of the second tube 154 inside the first outlet duct 110 is kept to a minimum or is kept negligible so as to facilitate measurement of a static pressure of air flowing inside the first outlet duct 110. Such a measurement of the static pressure of air relates to the measurement of air pressure generated by both the first axial fan 102 and the second axial fan 104. In effect, the second tube 154 may facilitate detection of a static pressure (Ps1) of air in the first outlet duct 110 (or inflowing through the second opening 166). Moreover, it may be noted that the first sensor 140 is deployable relative to the first axial fan 102 such that the second tube 154 is positioned downstream to the first tube 152 along an air flow generated by the first axial fan 102.
The fan system 100 may further include a first blade pitch control mechanism 182 for changing pitch angles of blades 184 of the first row of blades 122 of the first axial fan 102, and a second blade pitch control mechanism 186 for changing pitch angles of blades 188 of the third row of blades 128 of the second axial fan 104. It may be appreciated that any type of conventional blade pitch control mechanisms known in the art can be used as the first blade pitch control mechanism 182 and the second blade pitch control mechanism 186. The first blade pitch control mechanism 182 and the second blade pitch control mechanism 186 may respectively change the pitch angles of the blades 184 of the first row of blades 122 and the pitch angles of blades 188 of the third row of blades 128 based on input received from a controller 250. Therefore, the first blade pitch control mechanism 182 and the second blade pitch control mechanism 186 may be actuated and controlled by the controller 250.
According to an aspect of the disclosure, the stall detection system 139 (that includes the first sensor 140 and the second sensor 142) and the controller 250 may be a part of a control system 220 of the fan system 100. The control system 220 may also include a header pressure sensing device 252. The header pressure sensing device 252 may be disposed inside the header 120 and may be configured to measure a pressure of air flowing inside the header 120. In an embodiment, the header pressure sensing device 252 may include one or more pressure sensors to measure the pressure of air inside the header 120.
The controller 250 is communicably coupled to the first sensor 140, the second sensor 142, the first axial fan 102, the second axial fan 104, the header pressure sensing device 252, the first blade pitch control mechanism 182, and the second blade pitch control mechanism 186. The controller 250 is configured to control an operation of the first axial fan 102 and the second axial fan 104 to generate air flow and regulate the air pressure of the header 120 based on inputs received from the first sensor 140, the second sensor 142, and the header pressure sensing device 252. For example, the controller 250 is configured to detect air pressure within the header 120 based on the input from the header pressure sensing device 252 and is configured to determine a stall condition of one of the first axial fan 102 or the second axial fan 104 based on the inputs received from the first sensor 140 and the second sensor 142.
For example, the controller 250 may predict or determine a stall condition of the first axial fan 102 based on the difference of a dynamic pressure (Pd1) and a static pressure (Ps1) (i.e., an air pressure condition of the first outlet duct 110) measured by the first sensor 140. Similarly, the controller 250 may predict or determine the stall condition of the second axial fan 104 based on the difference of a dynamic pressure (Pd2) and a static pressure (Ps2) (i.e., an air pressure condition of the second outlet duct 112) measured by the second sensor 142. According to an example, if a difference between the air pressure condition of the first outlet duct 110 (as detected by the first sensor 140) and the air pressure condition of second outlet duct 112 (as detected by the second sensor 142) is greater than a threshold value, the controller 250 may determine a stall condition in one of the first axial fan 102 or the second axial fan 104. For example, if the air pressure condition of the first outlet duct 110 is greater than the air pressure condition of the second outlet duct 112 (e.g., by a threshold value), a stall condition of the second axial fan 104 is detected, and, accordingly, the controller 250 may control the first axial fan 102 to generate air flow and regulate (and compensate for) a shortage in air pressure of the header 120.
In an embodiment, the controller 250 is configured to determine or predict an occurrence of stall conditions of the first axial fan 102 and/or the second axial fan 104 and control the pitch angles of the blades 184 of the first row of blades 122 and/or the pitch angles of the blades 188 of the third row of blades 128 based on the prediction or determination of stall conditions of the first axial fan 102 and/or the second axial fan 104. In an exemplary embodiment, the controller 250 may predict the stall condition of the first axial fan 102 or the second axial fan 104 based on inputs received from the first sensor 140 and the second sensor 142 alone.
In an embodiment, the controller 250 may also check running conditions of the first axial fan 102 and the second axial fan 104 for detecting or predicting stall conditions of the first axial fan 102 and/or the second axial fan 104. Additionally, the controller 250 may seek an input of the header pressure sensing device 252 for detecting or predicting stall conditions of the first axial fan 102 and/or the second axial fan 104.
The controller 250 may be embodied as a computer device having a processor 254 and a memory 256. Instructions embodying a method for controlling the operation of the fan system 100 including a stall detection and control method for the detecting or predicting the occurrence of stall condition of the first axial fan 102 and/or stall condition of the second axial fan 104, and controlling the first axial fan 102 and/or the second axial fan 104 based on the detection of stall conditions, is stored in the memory 256. The instructions are executed by the processor 254 such that the controller 250 is configured to execute the various steps of the method, as per the operational conditions of the fan system 100. The input signals which drive the steps executed by the controller 250 may include sensed information, e.g., pressure signals corresponding to static pressures and dynamic pressures from the first sensor 140 and the second sensor 142, pressure signal from the header pressure sensing device 252, and/or information related to the pitch angles of blades 184 of the first row of blades 122, and/or an information related to the pitch angles of blades 188 of the third row of blades 128, and/or information related to running conditions of the first axial fan 102 and the second axial fan 104. Examples of the processor 254 may include, but are not limited to, an X86 processor, a Reduced Instruction Set Computing (RISC) processor, an Application Specific Integrated Circuit (ASIC) processor, a Complex Instruction Set Computing (CISC) processor, an Advanced RISC Machine (ARM) processor or any other processor.
The memory 256 may include tangible, non-transitory, computer-readable media such as read only memory (ROM), electrically programmable read-only memory (EPROM), optical and/or magnetic media, flash memory, etc. Such memory is relatively permanent, and thus may be used to retain values needed for later access by the processor. Memory 256 may also include sufficient amount of transitory memory in the form of random access memory (RAM) or any other non-transitory media.
INDUSTRIAL APPLICABILITY
A working of the fan system 100 according to the embodiment of the disclosure is discussed. During operation, an operator may switch on both the first axial fan 102 and the second axial fan 104 and operate the first axial fan 102 and the second axial fan 104 at suitable speeds to maintain a desired pressure level at the header 120. The desired pressure level may correspond to a suitable amount of air and speed of air needed to provide desired amount of solid fuel (e.g., coal) to the boiler 103. To achieve a desired pressure level, the controller 250 may send actuation signals and thereby control the first blade pitch control mechanism 182 and the second blade pitch control mechanism 186 to adjust the pitch angles of the blades 184 of the first row of blades 122 and the pitch angles of the blades 188 of the third row of blades 128, respectively.
When the first axial fan 102 and the second axial fan 104 may be running, air pressure from the first axial fan 102 may be delivered into the first tube 152 through the first opening 160. Since the second axial fan 104 may also be running, air pressure from each of the first axial fan 102 and the second axial fan 104 may be delivered into the second tube 154 through the second opening 166. The air pressure delivered into the first tube 152 may correspond to the dynamic pressure (Pd1) of air downstream to the first axial fan 102, while the air pressure delivered into the second tube 154 may correspond to the static pressure (Ps1) of air downstream to the first axial fan 102. It may be noted that the difference computed between the dynamic pressure (Pd1) and the static pressure (Ps1) (along with a similar difference as computed by the second sensor 142) facilitates determination of a stall condition of either the first axial fan 102 or the second axial fan 104. A method exemplifying such a process will be discussed below.
Also, during operation, the controller 250 may receive inputs from the first sensor 140 and may determine (or compute) a first differential pressure (DP1) of air flowing or passing through the first outlet duct 110 at a location proximate to the outlet 114 of the first axial fan 102. The first differential pressure (DP1) may correspond to a difference between the dynamic pressure (Pd1) of air and the static pressure (Ps1) of air, each measured by the first sensor 140 for the first outlet duct 110. For example, the first differential pressure (DP1) may be an application of the equation:
DP1 = Pd1 – Ps1
Similarly, the controller 250 may receive inputs from the second sensor 142 and may determine (or compute) a second differential pressure (DP2) of air flowing or passing through the second outlet duct 112 at a location proximate to the outlet 116 of the second axial fan 104. The second differential pressure (DP2) may correspond to a difference between the dynamic pressure (Pd2) of air and the static pressure (Ps2) of air, each measured by the second sensor 142 for the second outlet duct 112. For example, the second differential pressure (DP2) may be an application of the equation:
DP2 = Pd2 – Ps2
Referring to FIG. 3, a stall detection and control method (simply referred to as method 300) for the fan system 100 to determine or predict an occurrence of stall condition of a first axial fan 102 and/or a stall condition of the second axial fan 104, and control the first axial fan 102 and the second axial fan 104, is described now. The method 300 starts at step 302. At step 304, the controller 250 may check whether both the first axial fan 102 and second axial fan 104 are running. The controller 250 may maintain a status of the first axial fan 102 indicating whether the first axial fan 102 is running or stopped and stores the status in the memory 256. Similarly, the controller 250 may maintain a status of the second axial fan 104 indicating whether the second axial fan 104 is running or stopped and stores the status in the memory 256. Alternatively, the controller 250 may determine the current state of both the first axial fan 102 and the second axial fan 104 during execution of the method 300. If the controller 250 determines that one of the first axial fan 102 or the second axial fan 104 is not running at the step 304, the method 300 may return to the start of the step 302 and may keep monitoring the status of both the first axial fan 102 and the second axial fan 104. However, if the controller 250 determines that both the first axial fan 102 and the second axial fan 104 are running at the step 304, then the method 300 proceeds to step 306.
At step 306, the controller 250 may compare a header pressure (Pr) measured by the header pressure sensing device 252 to a predefined value and determines whether the header pressure (Pr) is below a predefined value. In an exemplary scenario, the predefined value may be 650 mmwc (i.e., 650 millimeters of water column). If the controller 250 determines that the header pressure (Pr) is above the predefined value, then the method 300 may return to the start of the step 306 or at the start of the step 304. If the controller 250 determines, at the step 306, that the header pressure (Pr) is below the predefined value, the method 300 may proceed to step 308 where the controller 250 may compare the first differential pressure (DP1) associated with the first axial fan 102 to the second differential pressure (DP2) associated with the second axial fan 104, and determines whether the DP1 is greater than the DP2. If the controller 250 determines that the DP1 is greater than the DP2, then the method 300 may proceed to step 310, otherwise the method 300 may proceed to step 312.
At step 310, the controller 250 may determine a first difference (Detla1) between the first differential pressure (DP1) and the second differential pressure (DP2) by subtracting the second differential pressure (DP2) from the first differential pressure (DP1), and determines whether the first difference (Delta1) is greater than a threshold value (i.e., first threshold value). If the controller 250 determines that the first difference (Delta1) is below the first threshold value, then the method 300 may return to the start of step 310 or to the start of step 308 or step 304.
If the controller 250 determines that the first difference (Delta1) is above the first threshold value, then the method 300 may proceed to step 314 where the controller 250 detects the stall condition of the second axial fan 104 as the first difference (Delta1) is above the first threshold value. Upon detection of the stall condition of the second axial fan 104, the method 300 may proceed to step 316. At step 316, the controller 250 may adjust or reduce the pitch angles of the blades 188 of the third row of blades 128 of the second axial fan 104 to overcome the stall condition of the second axial fan 104.
In an embodiment, the blades 188 of the third row of blades 128 may be fully closed so that no air flow occurs across the second axial fan 104. In response to this condition, the controller 250 may adjust or increase the pitch angles of the blades 184 of the first row of blades 122 of the first axial fan 102 to increase the air flow into the first outlet duct 110 to maintain the header pressure (Pr) in the header 120 at or above a desired level. In such a manner, damages occurring due to the stalling of the second axial fan 104 may be reduced or prevented, while ensuring the desired level of air flow to feed the required amount of solid fuel (e.g., coal) to the boiler 103.
The method 300 proceeds to step 312 if the controller 250, at step 308, determines that the DP1 is not greater than the DP2. At step 312, the controller 250 may determine a second difference (Detla2) between the second differential pressure (DP2) and the first differential pressure (DP1) by subtracting the first differential pressure (DP1) from the second differential pressure (DP2), and determines whether the second difference (Delta2) is greater than a threshold value (i.e., first threshold value). In an embodiment, the first threshold value may be 50 wc. If the controller 250 determines that the second difference (Delta2) is below the first threshold value, then the method 300 may return to the start of step 312 or at the start of step 308 or step 304.
If the controller 250 determines that the second difference (Delta2) is above the first threshold value, then the method 300 may proceed to step 318 where the controller 250 detects the stall condition of the first axial fan 102 as the second difference (Delta2) is above the first threshold value. Upon detection of the stall condition of the first axial fan 102, the method 300 may proceed to step 320. At step 320, the controller 250 may adjust or reduce the pitch angles of the blades 184 of the first row of blades 122 of the first axial fan 102 to overcome the stall condition of the first axial fan 102.
According to the foregoing working and functionality of the fan system 100, as described, damages occurring due to stalling of the first axial fan 102 (or the second axial fan 104) may be reduced or prevented, while ensuring the desired level of air flow or air pressure in the header 120 to feed the required amount of solid fuel (e.g., coal) to the boiler 103.
In an embodiment, the blades 184 of the first row of blades 122 may be (or may need to be) fully closed so that no air flow occurs across the first axial fan 102. In response to this condition, the controller 250 may adjust or increase the pitch angles of the blades 188 of the third row of blades 128 of the second axial fan 104 to increase the air flow into the second outlet duct 112 to maintain the header pressure (Pr) in the header 120 at or above a desired level. In some cases, therefore, the axial fans that may be controlled to generate air flow and regulate the air pressure of the header 120 may exclude the first axial fan 102 if the air pressure condition in the second outlet duct 112 is greater than the air pressure condition in the first outlet duct 110, (i.e., in other words, if the second differential pressure (DP2) is greater than the first differential pressure (DP1)).
In some embodiments, before moving to step 308, the controller 250 may detect that either or both DP1 and the DP2 is less than 0 mmwc. For example, if the controller 250 determines that the DP1 is less than 0 mmwc, the method 300 may directly proceed to step 318, and if the DP2 is detected to be less than 0 mmwc, the method 300 may directly proceed to step 314. Although steps 302, 304, and 306, are presented in a particular sequence, it may be appreciated that these steps may be performed in any other sequence. For example, step 306 may be performed before step 304 or step 302.
In some embodiments, a stall condition of one or more of the first axial fan 102 and the second axial fan 104 may be monitored in real time by operators or supervisors. As an example, the stall condition of the first axial fan 102 and the second axial fan 104 may be generated by way of one or more graphical representations that may be accessible to one or more of the supervisors or operators. Based on real time monitoring, it is possible that an operator or a supervisor may check fan dynamics or the air flow generated by each of the first axial fan 102 and the second axial fan 104 in real time, and, if required, may equalize or optimize the corresponding flow generated by the first axial fan 102 and the second axial fan 104 rather than altering parameters, such as a current supplied to one or more of the first axial fan 102 and the second axial fan 104, to help reduce or mitigate a stall condition of one or more of the first axial fan 102 and the second axial fan 104.
It will be apparent to those skilled in the art that various modifications and variations can be made to the system of the present disclosure without departing from the scope of the disclosure. Other embodiments will be apparent to those skilled in the art from consideration of the specification and practice of the system disclosed herein. It is intended that the specification and examples be considered as exemplary only, with a true scope of the disclosure being indicated by the following claims and their equivalent.
,CLAIMS:1. A stall detection system (139) for a fan system (100) having a plurality of fans (102, 104) that facilitate transport of a pulverized form of a solid fuel to a boiler (103) along an air flow generated by the plurality of fans (102, 104), the stall detection system (139) comprising:
a plurality of sensors (140, 142) correspondingly disposed downstream to the plurality of fans (102, 104) along the air flow, each sensor (140, 142) of the plurality of sensors (140, 142) including:
a base (150), a first tube (152) and a second tube (154) extending from the base (150), the first tube (152) defining a first opening (160) inclined to at least partially face and receive air pressure from a corresponding fan (102, 104) of the plurality of fans (102, 104), the second tube (154) including a second opening (166) to receive air pressure generated by one or more fans (102, 104) of the plurality of fans (102, 104), wherein a difference between the air pressure received through the first opening (160) and the air pressure received through the second opening (166) facilitates determination of a stall condition of one or more fans (102, 104) of the plurality of fans (102, 104).
2. The stall detection system (139) as claimed in claim 1, wherein the first tube (152) defines a longitudinal axis (200), an end (158) away from the base (150), and an edge (163) defining the first opening (160) at the end (158),
wherein the edge (163) is disposed in and along a plane (165) tilted at an angle between 40 degrees and 50 degrees to the longitudinal axis (200).
3. The stall detection system (139) as claimed in claim 1, wherein each sensor (140, 142) of the plurality of sensors (140, 142) is deployable relative to a corresponding fan (102, 104) of the plurality of fans (102, 104) such that the second tube (154) is positioned downstream to the first tube (152) along an air flow generated by the corresponding fan (102, 104).
4. The stall detection system (139) as claimed in claim 1, wherein the fan system (100) includes a plurality of ducts (110, 112) to correspondingly receive air pressure from the plurality of fans (102, 104) and deliver the air pressure to a common header (120),
wherein the first tube (152) is longer than the second tube (154), the first opening (160) of the first tube (152) being adapted to extend into a corresponding duct (110, 112) of the plurality of ducts (110, 112) and the second opening (166) being adapted to sit flush with an inner surface (180) of a wall (171) defined by the corresponding duct (110, 112).
5. The stall detection system (139) as claimed in claim 1, wherein the air pressure received through the first opening (160) corresponds to a dynamic pressure (Pd1, Pd2) of air generated by the corresponding fan (102, 104) and the air pressure received through the second opening (166) corresponds to a static pressure (Ps1, Ps2) of air generated by one or more fans (102, 104) of the plurality of fans (102, 104).
6. The stall detection system (139) as claimed in claim 1, wherein the base (150) includes a differential pressure transmitter (174) adapted to detect the difference between the air pressure received through the first opening (160) and the air pressure received through the second opening (166).
7. A fan system (100) for a boiler (103), the fan system (100) comprising:
a plurality of fans (102, 104) to generate and deliver air flow to a header (120), the header (120) adapted to receive and direct the air flow over and across a bed of a pulverized form of a solid fuel to transport the pulverized form of the solid fuel to the boiler (103) along with the air flow;
a controller (250) configured to control one or more of the plurality of fans (102, 104) to generate air flow and regulate the air pressure of the header (120) based on a stall condition of one or more fans (102, 104) of the plurality of fans (102, 104) and the air pressure within the header (120); and
a plurality of sensors (140, 142) coupled to the controller (250) and being correspondingly disposed downstream to the plurality of fans (102, 104) along the air flow, each sensor (140, 142) of the plurality of sensors (140, 142) including:
a base (150), a first tube (152) and a second tube (154) extending from the base (150), the first tube (152) defining a first opening (160) inclined to at least partially face and receive air pressure from a corresponding fan (102, 104) of the plurality of fans (102, 104), the second tube (154) including a second opening (166) to receive air pressure generated by one or more fans (102, 104) of the plurality of fans (102, 104), wherein a difference between the air pressure received through the first opening (160) and the air pressure received through the second opening (166) facilitates determination of the stall condition of one or more fans (102, 104) of the plurality of fans (102, 104).
8. The fan system (100) as claimed in claim 7, wherein the first tube (152) defines a longitudinal axis (200), an end (158) away from the base (150), and an edge (163) defining the first opening (160) at the end (158),
wherein the edge (163) is disposed in and along a plane (165) tilted at an angle between 40 degrees and 50 degrees to the longitudinal axis (200).
9. The fan system (100) as claimed in claim 7, wherein each sensor (140, 142) of the plurality of sensors (140, 142) is deployed relative to a corresponding fan (102, 104) of the plurality of fans (102, 104) such that the second tube (154) is positioned downstream to the first tube (152) along an air flow generated by the corresponding fan (102, 104).
10. The fan system (100) as claimed in claim 7 further including a plurality of ducts (110, 112) to correspondingly receive air pressure from the plurality of fans (102, 104) and deliver the air pressure to a common header (120),
wherein the first tube (152) is longer than the second tube (154), the first opening (160) of the first tube (152) being adapted to extend into a corresponding duct (110, 112) of the plurality of ducts (110, 112) and the second opening (166) being adapted to sit flush with an inner surface (180) of a wall (171) defined by the corresponding duct (110, 112).