JPS60249626A - Flow divider for gas turbine - Google Patents

Abstract

PURPOSE:To make it possible to appropriately drive a flow divider even upon abnormal operation, by controlling the output pressure of a fuel pump for a gas turbine such that it is made equal to the pressure which is the sum of the internal pressure of a burner, differential pressure of a fuel nozzle and the differential pressure of the flow divider. CONSTITUTION:Fuel whose pressure is boosted up by a fuel pump 11 is led to a flow divider 15 through a high pressure fuel filter 14, and then is fed into a burner 18 through a check valve 16 and a fuel nozzle 17. The flow divider 15 is controlled to be driven by a variable speed motor 27 in accordance with a set flow rate signal 21. At this stage the difference between the inlet pressure of the flow divider 15, that is, the outlet pressure of the fuel pump 11 and the outlet pressure of the flow divider 15 is made as small as possible in order to decrease the drive force of the flow divider 15. Further, a fuel bypass valve 10 is controlled such that the outlet pressure of the fuel pump 11 is made equal to the sum of the internal pressure of the burner which is detected by a pressure detector 29, the differential pressure of the fuel nozzle 17 and the differential pressure of the flow divider 15.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a flow divider used in a fuel oil system of a gas turbine.

[Background of the invention]

In general, gas turbines are designed to use all gaseous fuels and all liquid fuels ranging from kerosene to diesel oil, crude oil, and residual oil. In particular, from the standpoint of energy conservation, the use and use of unprocessed crude oil, residual oil, etc. with poor quality is being actively studied.

In addition, more than half of the troubles in gas turbines that use liquid fuel are thought to be caused by the fuel and fuel system, and the fuel oil system is one of the most important systems among the systems that make up the gas turbine. Among the fuel oil systems, the flow divider is a device that often causes trouble. A flow divider is a fuel distribution device that equally distributes fuel to each combustor in a gas turbine with multiple can combustors.

FIG. 1 shows a conceptual diagram of a flow divider.

As shown in Fig. 1, the flow divider is a flow divider element 1 consisting of a combination of driving and driven gears.The driving gears are connected by one connecting shaft 2, and multiple flow divider elements are connected to the same It has the function of forcibly evenly distributing the fuel flow rate by rotating the fuel oil in both directions at the same rotation speed.It is operated by the differential pressure ΔP between the fuel oil flow divider inlet and outlet. If the accuracy of fuel distribution in the flow divider is poor, the deviation in the fuel flow rate supplied to each combustor will increase, resulting in a difference in the combustion gas temperature in each combustor, and the combustion flowing into the turbine will increase. The gas temperature is unbalanced.

The flow rate of fuel oil to each combustor in the flow divider can cause major accidents such as damage due to thermal deformation of turbine stationary blades and high-temperature gas passage parts, and damage to turbine rotor blades due to high-cycle thermal shock. The distribution accuracy of is very important. 3 is an inlet oil passage and 4 is an outlet oil passage. FIG. 2 shows a cross-sectional view of the flow divider. The factors that determine the performance of the flow divider are the side clearance 7 and the tip clearance 8. The smaller the side clearance 7 and tip clearance 8, the better the fuel flow distribution accuracy (deviation) will be. However, if the sliding resistance of the gear 5.6 of the flow divider element 1 increases and foreign matter enters the gear. 5.6 sticking, which can lead to a major accident in which the gas turbine misfires due to fuel supply stoppage, therefore, during design, the maximum values of side clearance 7 and tip clearance 8 that keep the flow distribution accuracy within the allowable range were selected. do. The allowable flow rate deviation is expressed as the value obtained by subtracting the minimum fuel flow rate from the maximum fuel flow rate in each combustor divided by the average flow rate, and the value is several percent. The values of the side clearance 7 and tip clearance 8 to obtain a flow distribution accuracy of several percent are on the order of tens of microns. Therefore, the flow divider is manufactured with very high precision, and when in use, due to the sudden temperature change of the fuel oil, there is no clearance due to the difference in length between the outer casing and the inner gear. 5.6 It may cause the sticking phenomenon. In this way, the flow divider is a device that has many causes of trouble.

A conventional fuel oil system diagram is shown in Figure 3. As shown in FIG. 3, the fuel oil system of the gas turbine includes: a high-pressure fuel pump 11 driven via a flow cutoff valve 9, an accessory gear 12IC, and a reflatch 13 to cut off fuel when the gas turbine is stopped; Bypass flow rate adjustment valve 10. High pressure filter 14. Flow divider 15, check valve 16. Comprised of a fuel nozzle 17 and a combustor 18, the fuel oil supplied to the gas turbine is pressurized by a high-pressure fuel pump 11 to the pressure required for injecting it through the fuel nozzle 17, and then transferred to a flow divider 15 downstream thereof. is distributed to the combustor 18.

A speed sensor 19 is installed in the flow divider 15, and the actual flow rate is calculated based on the rotation speed of the flow divider.
Deviation 20 from the preset flow rate signal 21
Accordingly, the high pressure fuel pump 11 is activated by the bypass flow rate adjustment valve 10.
The fuel flow rate is adjusted by controlling the bypass flow rate.・
Figure 4 shows the pressure characteristics of each device at this time from gas turbine startup to rated load. In Figure 4.

The fuel flow rate 22 gradually increases as the gas turbine speed and load increase, the fuel nozzle differential pressure 23 increases in proportion to the square of the flow rate, and the fuel pump discharge pressure 25 increases, i.e., the flow divider inlet pressure. As for the combustor internal pressure 24, which increases rapidly as the gas turbine rotation speed approaches the rated point and gradually increases as the load is applied, the gas turbine rotation speed approaches the rated point similarly to the fuel pump discharge pressure 25. It shows a tendency to increase rapidly as the load increases and to gradually increase as the load increases. Combustor internal pressure 2
The pressure obtained by adding the fuel nozzle differential pressure 23 to 4 indicates the flow divider outlet pressure 26. It shows a tendency to increase proportionally.

In conventional fuel systems, as mentioned above, the flow divider is used with a very narrow clearance, foreign objects can enter between the gear and the casing, and corrosive components in the fuel can corrode the gear or casing. When the clearance disappears, a large braking force is applied to the gear, and since the flow divider is driven by the differential pressure between the fuel oil inlet and outlet, it can overcome the increase in braking force caused by foreign objects, etc., and provide instantaneous drive. There is a risk that the gears of the flow divider may stop because of the inability to apply force, and the risk of the gears of the flow divider becoming stuck increases as fuel oil of poor quality is used. Since the stoppage of the flow divider during operation will lead to fuel cutoff, that is, gas turbine trip, the reliability of the flow divider has a very large impact on the operational reliability of the entire gas turbine, and it is important to improve reliability. should be prioritized above all else.

[Purpose of the invention]

The purpose of the present invention is to: - make it possible to apply a large rotational force when the braking force increases due to the intrusion of foreign objects; - enable the flow divider to operate with a small driving force in normal conditions, and provide a large rotational force in abnormal situations. Therefore, it is an object of the present invention to provide a flow divider that properly controls the flow divider inlet pressure.

[Embodiments of the invention]

The present invention will be explained below with reference to the drawings. FIG. 5 shows an embodiment of the invention. The fuel oil pressurized by the fuel pump 11 is guided to the flow divider 15 via the high-pressure fuel oil filter 14. It is driven by a variable speed electric motor 27 that can control the speed. Note that variable speed motors 27 that are controlled only by setting signals are currently readily available. Also.

The 70-divider 15 shown in FIG. 5 is driven by a variable speed electric motor 27, but is essentially the same as a conventional flow divider 15 driven by a pressure differential at the inlet and outlet of the flow divider 15. Therefore, the flow divider body can be a conventional flow divider body that has a sufficient track record. Therefore.

The values of the flow divider clearance, that is, the side clearance 7 and tip clearance 8 that determine the fuel distribution accuracy of the flow divider, can also be the values of the conventional flow divider 15 that have a proven track record. The fuel oil coming out of the flow divider 15 is transferred to the check valve 16 and the fuel nozzle 1
7 and is supplied to the combustor 18. Note that the inlet pressure of the flow divider 15 is set so that the flow divider can be operated with a small driving force during normal operation, and is operated with a large margin for the maximum output of the variable speed electric motor 27, which is the driving machine. It is necessary to set it so that a large rotational force can be applied in the event of an abnormality in which the braking force increases due to the entry of foreign objects, etc. In order to keep the driving force of the flow divider 15 small, it is necessary to minimize the pressure difference between the flow divider 150 inlet pressure, that is, the fuel pump outlet pressure 25, and the flow divider outlet pressure, that is, the inlet pressure of the fuel nozzle 17. is necessary. However, as shown in FIG. 4, the outlet pressure 26 of the flow divider 15 is proportional to the square of the flow rate and varies greatly. It is necessary to control the Therefore, regarding the internal pressure of the combustor, the measurement of the internal pressure of the O combustor using the pressure sensor 29 is more indirect than the gas turbine main axial flow compressor discharge air pressure that is normally measured before entering the combustor. You can also hit the target. Furthermore, as shown in FIG. 6, a differential pressure curve 32 for the fuel flow rate of the fuel nozzle 17, which is determined by the structure of the fuel nozzle 17, and a differential pressure curve 33 set slightly lower are installed in the control circuit 31. The pressure value is obtained by adding the above-mentioned combustor internal pressure 24, the differential pressure installed in the control circuit 31, and the differential pressure value obtained by inputting the measured fuel flow rate calculated from the flow divider rotation speed. By providing a control circuit 30 to adjust the flow divider inlet pressure, that is, the fuel pump outlet pressure 25, and using the fuel bypass valve 10 as a pressure regulating valve, the differential pressure at the inlet and outlet of the flow divider 15 can be kept small. .

FIG. 7 shows the pressure characteristics from gas turbine startup to rated load when this control system is installed.

In FIG. 7, the pressure that is the sum of the differential pressure curve 34 set slightly lower than the fuel nozzle differential pressure curve 23, the differential pressure calculated from the Frode rotation speed, and the combustor internal pressure 24 is calculated at the fuel pump outlet. By setting the pressure to 25, i.e., the flow divider inlet pressure.

Fuel nozzle inlet pressure 26. which is the sum of fuel nozzle differential pressure 23 and combustor internal pressure 24. In other words, by setting the flow divider outlet, the pressure at the inlet and outlet of the flow divider,
In other words, the differential pressure between the fuel pump outlet pressure 25 and the fuel nozzle inlet pressure 26 can be kept low.

[Effect of sea opening]

According to the present invention: - When the braking force increases due to the entry of foreign matter, a large rotational force can be applied, the flow divider can be operated with a small driving force in normal conditions, and a large rotational force can be applied in abnormal conditions.

[Brief explanation of the drawing]

Figure 1 is a conceptual diagram of a flow divider, Figure 2 is a structural diagram of a flow divider, Figure 3 is a system diagram of a conventional fuel system, and Figure 4 is a diagram of a conventional fuel system.
The figure is a graph showing pressure characteristics of each device in a conventional fuel system, FIG. 5 is a system diagram of a fuel system showing an embodiment of the present invention, and FIG. 6 is a differential pressure characteristic diagram installed in a control circuit. Figure 7 is a graph showing the pressure characteristics of each device in the fuel system, 3... Inlet oil passage, 4... Outlet oil passage, 5... Drive gear, 6...
... Driven gear, 20... Control circuit. The agent and patent attorney, Akio Takahashi, also has figures 1 and 2, 3 figures, 1,000 ω figures, Fuhiichiga Portrait (7S), 6 figures, 1 figure U, υsu9-hi'n term, y=).

Claims (1)

[Claims] 1. In a gas turbine equipped with a flow divider, the outlet pressure of the fuel pump for the gas turbine is made to be the sum of the internal pressure of the combustor, the differential pressure of the fuel nozzle, and the differential pressure of the flow divider. A flow divider O for a gas turbine, characterized in that it is equipped with a control circuit.