JP5549470B2 - Fuel injection nozzle - Google Patents

Description

  The present invention relates to a single fuel injection nozzle connected to two fuel supply lines provided in a fuel supply system of a combustion apparatus such as a boiler.

  When operating a combustion device such as a boiler, the combustion amount is changed stepwise at multiple combustion positions, or the fuel supply amount is controlled steplessly to change the combustion amount continuously, thereby suppressing the number of starts and stops. However, stabilization of combustion and energy saving are performed.

  For example, the turndown ratio (minimum combustion amount: maximum combustion amount) of the current oil-fired boiler that employs a three-position control system that is controlled in three stages of stop, low combustion, and high combustion is about 1: 2. This type of oil fired boiler is required to have a multi-position or proportional combustion control and a turndown ratio of 1: 5 or more from the viewpoint of energy saving.

  Therefore, currently, a plurality of fuel injection nozzles are arranged, and a method of switching these fuel injection nozzles according to the combustion load and a return nozzle method of realizing multi-position or proportional combustion control by returning a part of the fuel are adopted. (For example, see Patent Documents 1 to 5).

Japanese Patent Laid-Open No. 5-180417 JP-A-5-264026 JP-A-7-091649 Japanese Patent Laid-Open No. 7-091650 JP 2000-146162 A

  However, in the method of realizing a multi-position or proportional combustion control by arranging a plurality of fuel injection nozzles, the center line of the combustion air nozzle in which the mounting position of each fuel injection nozzle is installed in an annular shape outside the fuel injection nozzle Since there is a deviation in the radial direction from the (air register center line), there is a problem that fuel and combustion air are not uniformly mixed in the circumferential direction, which adversely affects combustion performance.

  Also, in the return nozzle system that realizes multi-position or proportional combustion control by returning a part of the fuel, the turn-down ratio is limited to about 1: 3. There are problems that air is mixed into the line and fuel cannot be stably injected, and the fuel pump is adversely affected.

  The present invention has been made in view of the above problems, and its objective is to realize multi-position or proportional combustion control and a large turndown ratio while maintaining high combustion performance with respect to the entire combustion load. An object of the present invention is to provide a fuel injection nozzle that can be used.

  In order to achieve the above object, the invention according to claim 1 is characterized in that the fuel supply line extending from the discharge side of the fuel pump is branched into a plurality of branches, and the return line is branched from at least one of the branched fuel supply lines. Each end of the fuel supply line branched into a plurality of fuel injection nozzles provided in the fuel supply system of the combustion apparatus connected to the intake side of the fuel pump and provided with a flow rate control valve in the return line It is characterized by being connected to.

  According to a second aspect of the present invention, in the first aspect of the present invention, the fuel supply line extending from the discharge side of the fuel pump is branched into two, and the return line branched from one of the supply lines is a suction side of the fuel pump. The fuel injection nozzle provided in the fuel supply system connected to the nozzle is provided with two orifices of large and small diameters concentrically opened, the one fuel supply line is opened in one orifice, and the above-mentioned The other fuel supply line is configured to open.

  The invention according to claim 3 is the invention according to claim 2, wherein one fuel supply line on the high load side is opened to the large diameter side orifice, and the other fuel supply line on the low load side is made the small diameter side orifice. The return line is branched from the fuel supply line on the low load side while being opened.

  The invention according to claim 4 is the invention according to claim 2, wherein one fuel supply line on the high load side is opened to the large diameter side orifice, and the other fuel supply line on the low load side is made the small diameter side orifice. The return line is branched from the fuel supply line on the high load side while being opened.

  According to the present invention, since the fuel injection nozzle is formed with two orifices having different diameters that are concentrically opened, and each fuel supply line is opened in each orifice, the mounting position of the fuel injection nozzle is combusted. There is no deviation from the center line of the air nozzle (air register center line), and the mixture of the fuel injected from the small and large orifices concentrically arranged on the air register center line and the combustion air in the circumferential direction It is made uniform and high combustion performance can be obtained in the full load operation range. In addition, by controlling the opening of a flow control valve provided in a return line branched from one fuel supply line and adjusting the fuel return amount, a certain amount of fuel is injected from the other fuel supply line; In addition, multi-position or proportional control of combustion can be realized, and a high turndown ratio can be realized.

  In addition, if the proportional combustion control that returns the fuel from the fuel supply line through the return line is performed on the low load side, the benefits of the proportional combustion control can be enjoyed in a low load region that is actually frequently operated in a boiler or the like. Can do.

It is a block diagram which fractures | ruptures and shows some boilers provided with the fuel-injection nozzle which concerns on this invention. It is sectional drawing of the fuel injection nozzle principal part which concerns on this invention. It is sectional drawing of the fuel injection nozzle principal part which concerns on another form of this invention.

  Embodiments of the present invention will be described below with reference to the accompanying drawings.

  FIG. 1 is a block diagram showing a part of a boiler provided with a fuel injection nozzle according to the present invention, and FIG. 2 is a cross-sectional view of the main part of the fuel injection nozzle according to the present invention. As shown in FIG. A combustion injection nozzle 2 according to the present invention and a cylindrical combustion air nozzle 3 disposed around the combustion injection nozzle 2 according to the present invention are installed at the upper portion of the boiler 1.

  The fuel supply system of the boiler 1 is provided with a fuel tank 4 for storing fuel, and a fuel pump 6 is provided in a fuel supply line 5 extending from the fuel tank 4. An electromagnetic valve V1, which is an on-off valve, is provided on the discharge side (downstream side) of the fuel pump 6 of the fuel supply line 5. The fuel supply line 5 includes two fuel supply lines 7, downstream of the electromagnetic valve V1. Branches to 8. These fuel supply lines 7 and 8 are respectively provided with solenoid valves V2 and V3 which are on-off valves, and each fuel supply line 7 and 8 is connected to the single fuel injection nozzle 2 according to the present invention. ing.

  Here, one fuel supply line 7 is provided on the low load side, and a return line 9 branches from the fuel supply line 7 on the low load side inside the fuel injection nozzle 2. The line 9 is connected to the suction side of the fuel pump 6 of the fuel supply line 5. In the middle of the return line 9, an electromagnetic valve V4, which is an on-off valve, and a flow rate control valve 10 are provided. As will be described later, the amount of fuel returned from the return line 9 to the fuel supply line 5 is controlled by adjusting the opening of the flow rate control valve 10 to be supplied from the fuel supply line 7 to the fuel injection nozzle 2. The amount of fuel is proportionally controlled with respect to the combustion load, and an amount of fuel corresponding to a load of 20 to 60% with respect to 100% of the total combustion load is supplied from the fuel supply line 7 to the fuel injection nozzle 2.

  The other fuel supply line 8 is provided on the high load side, and a certain amount of fuel corresponding to 40% of the total combustion load 100% is supplied from the fuel injection nozzle 2 from the fuel supply line 8. Supplied to.

  Here, the structure of the fuel injection nozzle 2 is demonstrated below based on FIG.

  Two large and small orifices 11 and 12 opening concentrically are formed on the center of the lower end of the fuel injection nozzle 2 (center line (air register center line) of the combustion air nozzle 3). The high-load side fuel supply line 8 is opened to the orifice 11 on the side, and the low-load side fuel supply line 7 is opened to the orifice 12 on the small diameter side.

  More specifically, the large-diameter orifice 11 is formed at the center of the bottom wall 13 a of the housing 13 of the fuel injection nozzle 2, and the nozzle 14 arranged vertically in the center of the shaft inside the housing 13. And a holder 15 for holding it. The fuel supply line 7 on the low load side is connected to the nozzle 14, and a throttle portion 14 a that is throttled downward is formed at the tip (lower end) of the nozzle 14. The lower surface opens concentrically in the large-diameter orifice 11 as a small-diameter orifice 12.

  A cylindrical flow path 16 is formed around the nozzle 14, and the flow path 16 communicates with the inside of the nozzle 14 through a plurality of communication holes 14 b formed in the nozzle 14. A return line 9 is connected to the flow path 16.

  Further, a plurality of flow paths 15a are formed in the lateral direction at the lower end of the holder 15, and a fuel supply line 8 on the high load side is connected to the flow paths 15a. The flow path 16 opens to the large-diameter orifice 11 through a space 17 formed around the lower end throttle portion 14 a of the nozzle 14.

  On the other hand, as shown in FIG. 1, a wind box 18 constituting a combustion air supply path is installed at the upper portion of the boiler 1, and a blower 19 is connected to the wind box 18. An electric motor (not shown) that is a driving source of the blower 19 is electrically connected to an inverter device 20 for controlling the number of rotations, and a control device 21 is connected to the inverter device 20. . Further, the electromagnetic valves V1 to V4 and the flow rate control valve 10 are electrically connected to the control device 21, and the control device 21 receives the electromagnetic valves V1 to V4 and the flow rate control valve 10 in response to a request from the boiler 1. And the inverter device 20 are controlled.

  Thus, the boiler 1 according to the present embodiment employs a method of continuously changing the combustion amount by controlling the fuel supply amount steplessly according to the combustion load. When the operation is started, the boiler 1 undergoes processes such as pre-purge, pre-ignition, and ignition try from the stopped state, and a predetermined amount of fuel is injected from the fuel injection nozzle 2 in the combustion device, and combustion air is supplied from the blower 19. The fuel is supplied from the wind box 18 to the combustion air nozzle 3 and a mixture of these fuel and combustion air forms a mixture of a predetermined air-fuel ratio (A / F), and heat generated by the combustion of this mixture is generated in the boiler. 1 for steam generation.

  For example, when the boiler 1 is operated in a low load range of 20 to 60% load, the control device 21 closes the electromagnetic valve V3, opens the other electromagnetic valves V1, V2, and V4, and the flow control valve 10 The amount of fuel corresponding to the combustion load is injected from the fuel injection nozzle 2 and the required amount of combustion air is supplied from the blower 19 to the combustion air nozzle 3. Supplied. That is, the fuel in the fuel tank 4 is pressurized by the fuel pump 6 in the process of flowing through the fuel supply line 5, and this pressurized fuel is supplied to the fuel injection nozzle 2 through the fuel supply line 7 on the low load side. A part of the fuel is returned from the return line 9 to the intake side of the fuel pump 6 in the fuel supply line 4. Therefore, by adjusting the opening degree of the flow control valve 10, the amount of fuel returned to the fuel supply line 5 through the return line 9 changes. For example, the fuel control valve 10 is throttled to reduce the amount of fuel flowing through the return line 9. If the flow rate is reduced, the amount of fuel supplied from the fuel supply line 7 to the fuel injection nozzle 2 increases, and when the fuel control valve 10 is opened from this state, the flow rate of fuel flowing through the return line 9 increases. The fuel supplied from the fuel supply line 7 to the fuel injection nozzle 2 decreases.

  The fuel supplied from the fuel supply line 7 to the fuel injection nozzle 2 in this low load region passes through the nozzle 14 of the fuel injection nozzle 2 shown in FIG. 2 and is directed downward from the small-diameter orifice 12 opened on the lower surface thereof. The fuel thus injected is mixed with the combustion air supplied from the blower 19 to the combustion air nozzle 3 to form an air-fuel mixture having a predetermined air-fuel ratio (A / F). In this case, the large and small diameter orifices 11 and 12 that are concentrically opened as described above are arranged on the center line (air register center line) of the combustion air nozzle 3, so that the small diameter orifice 12 is injected. The fuel and the combustion air are uniformly mixed in the circumferential direction, and high combustion performance is ensured.

  Thus, the amount of fuel supplied from the fuel supply line 7 to the fuel injection nozzle 2 is proportionally controlled by controlling the opening of the flow control valve 10 in accordance with the combustion load as described above, and the blower The amount of combustion air supplied from 19 to the combustion air nozzle 3 is also proportionally controlled, and proportional combustion control that continuously changes the combustion load in the range of 20% to 40% can be realized.

  When the operation of the boiler 1 shifts to a high load range exceeding 60% load, the control device 21 opens the electromagnetic valve V3, and the opening degree of the flow control valve 10 and the rotation speed of the blower 19 are controlled, and the combustion load The fuel corresponding to the amount is supplied from the fuel supply line 8 to the fuel injection nozzle 2 and the required amount of combustion air is supplied to the combustion air nozzle 3.

  That is, a fuel corresponding to a 40% load is supplied to the fuel injection nozzle 2 from the fuel supply line 8 on the high load side, and the fuel whose amount is proportionally controlled by the flow control valve 10 is the fuel on the low load side. The fuel is supplied from the supply line 7 to the fuel injection nozzle 2. A certain amount of fuel (equivalent to a 40% load) supplied from the fuel supply line 8 on the high load side to the fuel injection nozzle 2 passes through the space 17 from the flow path 16 in the fuel injection nozzle 2 shown in FIG. The fuel that is injected downward from the large-diameter orifice 11 and supplied from the low-load-side fuel supply line 7 to the fuel injection nozzle 2 is injected downward from the small-diameter orifice 12 as described above. These fuels are mixed with the combustion air supplied from the blower 19 to the combustion air nozzle 3 to form a predetermined air-fuel ratio (A / F) mixture. In this case, since the orifices 11 and 12 having different diameters concentrically opening as described above are arranged on the center line (air register center line) of the combustion air nozzle 3, the orifices 11 and 12 The injected fuel and combustion air are uniformly mixed in the circumferential direction, and high combustion performance is ensured even in a high load region.

  Thus, in high load operation, a certain amount of fuel corresponding to 40% load is supplied to the fuel injection nozzle 2 from the fuel supply line 8 on the high load side, and the flow control valve 10 is opened according to the combustion load. By controlling the degree, the amount of fuel supplied from the low load side fuel supply line 7 to the fuel injection nozzle 2 is proportionally controlled in the range of 20 to 60% load, thereby reducing the combustion load to 60 to 100%. It can be changed continuously in the range.

  As described above, in the present embodiment, two orifices 11 and 12 having large and small diameters concentrically opening are formed in a single fuel injection nozzle 2, and each fuel supply line 8, 7 is employed so that the mounting position of the fuel injection nozzle 2 does not deviate from the air register center line of the combustion air nozzle 3, and the large and small orifices arranged concentrically on the air register center line The fuel injected from 11 and 12 and the combustion air are mixed uniformly in the circumferential direction, and high combustion performance can be obtained in the entire load range.

  Further, by controlling the opening degree of the flow rate control valve 10 provided in the return line 9 branched from the fuel supply line 7 on the low load side and adjusting the fuel return amount, the fuel supply line 8 on the high load side is adjusted. In addition to injecting a certain amount of fuel, proportional control of combustion can be realized, and a high turndown ratio of 1: 5 can be realized.

  Furthermore, in the present embodiment, the proportional combustion control for returning the fuel from the fuel supply line 7 via the return line 9 is performed on the low load side, so that the proportional combustion is performed in the low load region where the boiler 1 is actually frequently operated. You can enjoy the benefits of control.

  In the above embodiment, the case where the combustion amount is proportionally controlled by continuously controlling the opening degree of the flow control valve 10 has been described. However, the present invention sets the opening degree of the flow control valve 10 stepwise. Of course, the present invention can be similarly applied to a combustion apparatus that employs a system in which the amount of combustion is controlled in multiple positions.

  Further, in the above embodiment, the return line 9 is branched from the fuel supply line 7 on the low load side, and the opening of the flow control valve 10 provided in the return line 9 is controlled, so that combustion in the low load region is performed. Although the amount is proportionally controlled, as shown in FIG. 3, the return line 9 is branched from the fuel supply line 8 on the high load side, and the opening of the flow control valve 10 provided in the return line 9. By controlling this, the combustion amount in the high load range may be proportionally controlled.

DESCRIPTION OF SYMBOLS 1 Boiler 2 Fuel injection nozzle 3 Combustion air nozzle 4 Fuel tank 5 Fuel supply line 6 Fuel pump 7, 8 Fuel supply line 9 Return line 10 Flow control valve 11 Large diameter side orifice 12 Small diameter side orifice 13 Fuel injection nozzle housing 13a Bottom wall of housing 14 Nozzle 14a Nozzle restrictor 14b Nozzle communication hole 15 Holder 15a Holder flow path 16 Flow path 17 Space 18 Wind box 19 Blower 20 Inverter device 21 Control device V1-V4 Solenoid valve

Claims (4)

A fuel supply line extending from the discharge side of the fuel pump is branched into a plurality, a return line branched from one of the branched fuel supply lines is connected to the suction side of the fuel pump, and a flow rate control is performed on the return line. A fuel injection nozzle provided in a fuel supply system of a combustion apparatus configured by providing a valve,
A fuel injection nozzle configured to be connected to each end of the fuel supply line branched into a plurality. A fuel injection nozzle provided in a fuel supply system in which a fuel supply line extending from the discharge side of the fuel pump is branched into two, and a return line branched from one of the fuel supply lines is connected to the suction side of the fuel pump Because
Two orifices of large and small diameters concentrically opened are provided, the one fuel supply line is opened in one orifice, and the other fuel supply line is opened in the other orifice. The fuel injection nozzle according to claim 1.   One fuel supply line on the high load side is opened to the large diameter side orifice, the other fuel supply line on the low load side is opened to the small diameter side orifice, and the return line is connected to the fuel supply line on the low load side. 3. The fuel injection nozzle according to claim 2, wherein the fuel injection nozzle is branched.   One fuel supply line on the high load side is opened to the large diameter side orifice, the other fuel supply line on the low load side is opened to the small diameter side orifice, and the return line is connected to the fuel supply line on the high load side. 3. The fuel injection nozzle according to claim 2, wherein the fuel injection nozzle is branched.

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