Method for determining the flow rate of a combustible fluid injected into a combustion chamber without using an additional orifice plate

Abstract

The present invention relates to a method for determining the flow rate of a combustible fluid injected into a combustion chamber (120) of a turbine (100), the method comprising: determining the cross-section of an orifice of at least one nozzle (112, 113, 114, 115) through which the combustible fluid is injected into the combustion chamber (120); determining the pressure of the combustible fluid upstream of the orifice of the nozzle (112, 113, 114, 115); determining the pressure downstream of the orifice of the nozzle (112, 113, 114, 115); and determining the flow rate of the combustible fluid flowing through the orifice of at least one nozzle (112, 113, 114, 115).

Description

Technical Field

[0001] The invention relates to a method for determining the flow rate of a combustible fluid injected into a turbomachine having one or more turbomachine combustion chambers, in particular a gas turbine, and also to a method for triggering such a determination method. Background Art

[0002] A gas turbine generally includes an intake section, a compressor, one or more combustion chambers, a turbine, and an exhaust section. Each combustion chamber may include one or more nozzles for a combustible fluid.

[0003] A flow path through the gas turbine may be defined. In normal operation, air enters the gas turbine through an intake section. The air flows into a compressor where the pressure of the air is increased. The compressed air then flows to all combustion chambers where it is mixed with a fuel (e.g., gas) to form a combustible air-fuel mixture. The air-fuel mixture is injected into the combustion chambers for combustion. This combustion produces hot gases that are injected into a turbine to extract the energy contained in the hot gases. Thereafter, exhaust gases can be discharged from the gas turbine through an exhaust section.

[0004] The regulation and protection systems for high power gas turbines usually include protection or limitation at startup and before combustion or flame is detected. This protection consists in limiting the amount of unburned combustible gas entering the turbine and the recovery furnace located downstream during the ignition of the combustion chamber and before the flame is detected.

[0005] Typically, it is necessary to measure the flow rate of the combustible fluid in order to regulate the turbine during normal operation and also before a flame is detected. Most installed flow rate measurement systems are adapted to measure at rated load, i.e. after ignition and after the alternator has been synchronized with the network.

[0006] However, the gas flow rate before ignition is quite low compared to the flow rate at rated load, so the flow meter used for rated load will have a relatively large error margin to not properly estimate the low flow rate as required for ignition. In addition, installing a second flow meter to measure the ignition flow rate may impose an additional and undesirable pressure drop on the combustible gas in the combustible fluid system.

[0007] Known practice, in particular from document WO99067617, is to use a flow rate measuring device operating on the following principle: a fluid flowing through a restricted orifice will experience a pressure drop proportional to the square of the flow rate. If the characteristics of the fluid and the orifice are completely known, the pressure drop measured on both sides of the orifice will be able to deduce the fluid flow rate. This is then a flow rate measurement using an orifice plate. This measurement allows the instantaneous volume flow rate to be derived directly. This pressure drop at the orifice plate (or restricted orifice) has no energy loss (pressure drop), but rather converts "pressure" energy into "velocity" energy.

[0008] This measurement method requires the use of an additional orifice plate or flow restriction placed in the channel where the combustible fluid is injected. This results in an additional pressure drop in the combustible fluid line. In addition, this method is expensive because it requires an additional component dedicated to this flow rate measurement.

[0009] Therefore, there is still a need for a solution for determining the flow rate of a combustible fluid injected into a combustion chamber, which solution does not have the above-mentioned disadvantages. In particular, there is still a need for a solution for determining the flow rate of a combustible fluid injected into a combustion chamber, which solution is less expensive and easier to integrate into the combustion chamber and easier to implement.

[0010] Document US20070186557A1 defines the effective cross-sectional area (Ae) as a physical correction that depends on the pressure, velocity and temperature upstream and downstream of the nozzle. Specifically, the size of the effective cross-sectional area can define the pressure at the nozzle inlet. The size of the effective cross-sectional area can ensure that the pressure ratio in the nozzle does not exceed the maximum or minimum allowable limit, which is called the critical pressure ratio CPR (1.78), exceeding which the flow rate remains constant. Summary of the invention

[0011] To this end, the present invention proposes a method for determining the flow rate of a combustible fluid injected into a combustion chamber of a turbine, wherein the combustible fluid is injected into the combustion chamber through an orifice of at least one nozzle, the method comprising the following steps:

[0012] determining a cross-section of an orifice of the at least one nozzle through which the combustible fluid is injected into the combustion chamber;

[0013] determining a pressure of the combustible fluid upstream of an orifice of the nozzle;

[0014] determining a pressure downstream of an orifice of the nozzle;

[0015] determining a flow rate of the combustible fluid through the orifice of the at least one nozzle based on the determined cross-section of the orifice of the at least one nozzle, the determined pressure of the combustible fluid upstream of the orifice of the nozzle, and the determined pressure downstream of the orifice of the nozzle; and

[0016] The flow rate of the combustible fluid injected into the combustion chamber is determined based on the pressure difference across the at least one nozzle. According to one embodiment of the determination method, the flow rate of the combustible fluid injected into the combustion chamber is determined as the sum of the flow rates of the combustible fluid flowing through the plurality of nozzles.

[0017] According to one embodiment of the determination method, the pressure of the combustible fluid downstream of the orifice of the nozzle is the pressure inside the combustion chamber.

[0018] According to an embodiment of the determination method, the combustible fluid is a gas mixture.

[0019] According to one embodiment of the determination method, the pressure of the combustible fluid upstream of the orifice of the nozzle is determined indirectly by measuring the pressure difference between the fuel line and the pressure of the compressed air leaving the compressor.

[0020] According to one embodiment of the determination method, the flow rate of the combustible fluid injected into the combustion chamber is determined before ignition in the combustion chamber.

[0021] According to one embodiment of the determination method, the flow rate of the combustible fluid is determined when the pressure upstream of a space communicating with the at least one nozzle is strictly higher than the pressure in the space.

[0022] According to one embodiment of the determination method, the turbine comprises a plurality of combustion chambers, each combustion chamber comprising at least one nozzle for a combustible fluid, and the flow rate of the combustible fluid injected into each combustion chamber is determined until the ignition timing of all the combustion chambers is reached.

[0023] According to one embodiment of the determination method, the turbine includes at least one combustible fluid supply line for supplying the combustible fluid to the at least one combustion chamber, and the at least one combustible fluid supply line is connected to at least one distribution device to provide supply to the at least one nozzle, wherein the flow rate of the combustible fluid injected into the combustion chamber is determined based on the pressure measured at the single distribution device.

[0024] The invention also relates to a triggering method for determining the flow rate of a combustible fluid injected into a combustion chamber, the combustible fluid being injected into the combustion chamber through the orifice of at least one nozzle, the method comprising the following steps:

[0025] determining a difference between a pressure of the combustible fluid upstream of an orifice of the nozzle and a pressure of the combustible fluid downstream of an orifice of the nozzle; and

[0026] The determination method as described above is performed in the case where the pressure of the combustible fluid upstream of the orifice of the nozzle is higher than the pressure downstream of the orifice of the nozzle. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] The accompanying drawings illustrate the present invention:

[0028] Figure 1 A partial assembly diagram of a gas turbine is schematically shown.

[0029] Figure 2 Shows Figure 1 An operating diagram of a gas turbine is shown. DETAILED DESCRIPTION

[0030] Reference Figure 1 The auxiliary combustible fluid supply system 10 for the gas turbine 100 is connected to a combustible fluid source at a pressure of P1. The auxiliary system 10 may include a filter 70, a shuttle valve 80, and a pressure regulating valve 90, the downstream of which maintains a pressure of P2.

[0031] As described above, the gas turbine 100 includes an intake section 102, a compressor 104, one or more combustors 120, a turbine 106, and an exhaust section 108. Each combustor 120 may include one or more types of nozzles 112,113,114,115.

[0032] A flow path through the gas turbine 100 may be defined. In normal operation, air enters the gas turbine 100 through an air intake portion 102. The air flows into a compressor 104, which compresses the air into compressed air. The compressed air enters the overall combustion chamber via 140, mixes with a fuel such as a gas, and forms a combustible air-fuel mixture in a space 111. One or more nozzles 112, 113, 114, 115 open into the space 111.

[0033] The air-fuel mixture combusted in the combustion chamber 120 generates a flow of hot gases along the duct 130 to the turbine section 106 where the kinetic energy of the hot gases is converted to mechanical energy before being exhausted via the exhaust section 108 .

[0034] The required level of compression prior to entering the combustion chamber is typically represented by a pressure ratio related to the compressor delivery pressure (PCD) measured by pressure sensor 160. This pressure ratio is typically between 1.1×PCD and 1.5×PCD. To this end, pressure sensor 150 is used to continuously monitor the pressure difference between the combustible fluid line and the pressure PCD at the outlet of compressor 104.

[0035] The combustion system may comprise at least one combustion chamber 120 having at least one type of nozzle, each type of nozzle having a specific flow rate. An even distribution path of the combustible fluid in each type of nozzle is preferably obtained by dedicated distribution lines. Figure 1 A combustible fluid distribution system for at least one combustion chamber 120 is shown, each combustion chamber being equipped with at least one type of nozzle (e.g., four), but only one of each type 112, 113, 114, 115 is shown for each combustion chamber. Each type of nozzle is supplied by four combustible fluid supply lines C1, C2, C3, C4, each of which is connected to a distribution device D1, D2, D3, D4, respectively, thereby providing supply to the nozzle 112, 113, 114, 115, respectively. Each distribution line can have a specific flow rate characteristic. In addition, the nozzles 112, 113, 114, 115 can be arranged in the same combustion chamber 120, for example Figure 2 As shown, a circular configuration around the longitudinal axis of the combustion chamber 120. Thus, the total number of nozzles in the combustion system is the number of nozzle types per combustion chamber multiplied by the number of combustion chambers. Therefore, the total flow rate associated with the combustion can be derived in a simplified manner, namely: the flow rate through at least one nozzle of each type 112, 113, 114, 115 is estimated and then this flow rate is multiplied by the number of combustion chambers 120. Of course, in the case of partial flow rate measurements, or for the purpose of testing the combustion system, a single measurement of the distribution device can be performed.

[0036] The method is hereinafter combined with a turbine (e.g. Figure 1 and 2 Alternatively, the method for determining may be implemented in any turbine including at least one combustion chamber equipped with at least one nozzle for injecting a combustible fluid into the combustion chamber, and in normal operation, the upstream pressure of the nozzle network of each combustion chamber may exceed the downstream pressure.

[0037] The method uses the principle of measuring the flow rate through an orifice and, for this purpose, takes into account the characteristics of at least each type of nozzle 112, 113, 114, 115 used in the combustion chamber 120, such as the effective cross-sectional area (Ae) and the upstream and downstream pressures of each nozzle.

[0038] Therefore, the downstream pressure and the upstream pressure and the ratio of these pressures can estimate the mass flow rate through each type of nozzle and then determine the total flow rate of the combustible fluid injected into all combustion chambers 120. In other words, the flow rate of the combustible fluid injected into the combustion chamber 120 is determined as the sum of the estimated mass flow rate of the combustible fluid flowing through each type of nozzle 112, 113, 114, 115 multiplied by the number of chambers 120.

[0039] The method considers the effective cross-sectional area of ​​at least each type of nozzle 112, 113, 114, 115 used in the combustion chamber 120. Each nozzle is characterized by having an effective cross-sectional area to allow the combustible fluid to pass between the cover at 110 and 111 after the nozzle, the size of which is known according to the operating mode. The cross-sectional area of ​​the effective passage can be compared to a hole. Therefore, for each design point, the pressure of the cover at 110 is calculated, which can be based on: mass flow rate, pressure in the combustion chamber at 111 and the nature of the combustible gas.

[0040] Furthermore, equations relating the mass flow rate of the line, the pressure ratio of the nozzle, the fuel properties, the pressure in the combustion chamber (PCC) and the effective cross-sectional area are known to those skilled in the art.

[0041] Thus, if the effective cross-sectional area of ​​each nozzle type 112, 113, 114, 115 is known, as well as the upstream pressure at 110 and the downstream pressure at 111, the mass flow rate for each nozzle type can be calculated.

[0042] For the purposes of this specification, the term "pressure upstream" or "upstream pressure" is defined as the static pressure of the combustible fluid at a point 110 upstream or at the inlet of any nozzle 112, 113, 114, 115. To estimate the combustible gas pressure (Pc) upstream of the nozzle 110, the compressor's air delivery pressure or PCD measured at 160 and the measured value 150 of the pressure difference between the combustible fluid pipeline and the compressor delivery pressure PCD can be used. To this end, the following formula can be used:

[0043] Pc=PCD+ΔP(combustible fluid pipeline and PCD)

[0044] The pressure downstream of the nozzle or the pressure inside the combustion chamber 111 is the pressure of the air / combustible gas mixture in the chamber. This pressure cannot be measured directly, but a relatively similar pressure can be measured, namely the PCD 160. Specifically, the pressure in the combustion chamber (Pcc) is equal to the compressor discharge pressure (CPD) minus the pressure drop (this pressure drop is known or estimated as a percentage) experienced by the compressed air leaving the compressor and flowing through the combustion chamber.

[0045] Therefore, if the effective cross-sectional area of ​​the nozzle and the upstream pressure at 110 and the downstream pressure at 111 are known, the mass flow rate for each nozzle type 112, 113, 114, 115 can also be calculated.

[0046] As a result, the flow rate of the combustible fluid injected into the combustion chamber can be determined based on the flow rate of the combustible fluid flowing through the orifice of the at least one nozzle. Figure 1As shown, it is located inside the combustion chamber. Each orifice of the plurality of nozzles 112, 113, 114, 115 is disposed inside the corresponding combustion chamber. Therefore, the determination process does not require the addition of an additional flow restriction hole or orifice plate to measure the flow rate. Therefore, the method for determination is simplified and cheaper. In addition, since there is no additional orifice plate or flow restriction hole, the generation of an additional pressure drop in the combustible fluid line can be avoided.

[0047] Preferably, before the combustion chamber is ignited, when the pressure of the combustible fluid P2 upstream of the orifices of the nozzles 112, 113, 114, 115 is higher than the downstream pressure as far as the space 111, a method for determining the flow rate of the combustible fluid injected into the combustion chamber 120 is performed. In particular, this determination method makes it possible to determine the amount of unignited combustible gas injected into the combustion chamber 120 during ignition, before the flame is detected, which enters the turbine 100 and the recovery boiler located downstream. This allows the gas turbine to be regulated and thus protected.

[0048] In order to be able to improve protection, an operation is performed to determine the flow rate of the combustible fluid injected into each combustion chamber 120 until the moment of ignition of all the combustion chambers.

[0049] This method is equivalent to a method of indirect measurement of the flow rate of the combustible fluid and is suitable for measuring the flow rate before ignition. The method is particularly easy to implement because it does not use an additional orifice plate to estimate the flow rate and does not generate additional pressure drops. In addition, unlike the flow meter measurements usually performed upstream of the combustible fluid supply line, the above-mentioned measurement as close as possible to the flow rate injected into the combustion chamber can have the most correct possible value (ignoring measurement errors). In particular, there may be many leaks in the supply line between the flow meter and the combustion chamber, as is the case with the gas port, which may distort the measurement. Therefore, the flow meter measurement upstream of the pipeline, due to excessively leaking ports, can lead to a loss of operability of the machine.

Claims

1. A method for determining the flow rate of a combustible fluid injected into a combustion chamber (120) of a turbine (100), the combustible fluid being a gas mixture and the combustible fluid being injected into the combustion chamber through an orifice of at least one nozzle (112, 113, 114, 115), the orifice being arranged inside the combustion chamber, the method comprising the following steps: determining a cross-section of an orifice of the at least one nozzle (112, 113, 114, 115) through which the combustible fluid is injected into the combustion chamber (120); determining a pressure of the combustible fluid upstream of an orifice of the nozzle (112, 113, 114, 115); determining a pressure downstream of an orifice of the nozzle (112, 113, 114, 115); determining a flow rate of a combustible fluid flowing through the orifice of the at least one nozzle (112, 113, 114, 115) based on the determined cross-section of the orifice of the at least one nozzle, the determined pressure of the combustible fluid upstream of the orifice of the nozzle, and the determined pressure downstream of the orifice of the nozzle; as well as determining a flow rate of a combustible fluid injected into the combustion chamber (120) based on a pressure difference across the at least one nozzle (112, 113, 114, 115); The pressure of the combustible fluid upstream of the orifice of the nozzle (112, 113, 114, 115) is indirectly determined by measuring the pressure difference between the combustible fluid line and the pressure of the compressed air leaving the compressor (PCD).

2. The determination method according to claim 1, wherein the combustion chamber (120) comprises a plurality of nozzles (112, 113, 114, 115), wherein: The flow rate of the combustible fluid injected into the combustion chamber (120) is determined as the sum of the flow rates of the combustible fluid flowing through the plurality of nozzles (112, 113, 114, 115).

3. The determination method according to claim 1 or 2, wherein: The pressure of the combustible fluid downstream of the orifice of the nozzle (112, 113, 114, 115) is the pressure inside the combustion chamber (120).

4. The determination method according to any one of the preceding claims, wherein: Prior to ignition in the combustion chamber (120), a flow rate of the combustible fluid injected into the combustion chamber (120) is determined.

5. The determination method according to any one of the preceding claims, wherein: The flow rate of the combustible fluid is determined when the upstream pressure (P2) of the space (111) communicating with the at least one nozzle (112, 113, 114, 115) is strictly higher than the pressure in the space (111).

6. According to the determination method according to any one of the preceding claims, the turbine (100) includes a plurality of combustion chambers (120), each combustion chamber includes at least one nozzle (112, 113, 114, 115) for a combustible fluid, and the flow rate of the combustible fluid injected into each of the combustion chambers (120) is determined until the ignition moment of all the combustion chambers is reached.

7. The determination method according to any one of the preceding claims, wherein the turbine comprises at least one combustible fluid supply line (C1, C2, C3, C4) for supplying combustible fluid to the at least one combustion chamber (120), the at least one combustible fluid supply line (C1, C2, C3, C4) being connected to at least one distribution device (D1, D2, D3, D4) to provide supply to the at least one nozzle (112, 113, 114, 115), wherein: The flow rate of the combustible fluid injected into the combustion chamber is determined based on the pressure measured at the single distribution device.

8. A triggering method for determining the flow rate of a combustible fluid injected into a combustion chamber (120), the combustible fluid being injected into the combustion chamber through the orifice of at least one nozzle (112, 113, 114, 115), the method comprising the following steps: determining a difference between a pressure of the combustible fluid upstream of an orifice of the nozzle (112, 113, 114, 115) and a pressure of the combustible fluid downstream of the orifice of the nozzle (112, 113, 114, 115); as well as The determination method according to any one of claims 1 to 6 is performed in the case where the pressure of the combustible fluid upstream of the orifice of the nozzle (112, 113, 114, 115) is higher than the pressure downstream of the orifice of the nozzle (112, 113, 114, 115).

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