A method for designing the position of an ion flame detector in a reheat combustor

Abstract

The application discloses a method for designing the position of an ion flame detector of a reheat combustor, and belongs to the field of aero-engine design. The method firstly takes small reheat and full reheat working conditions as inputs, obtains corresponding backflow zones through CFD combustion simulation, and solves the intersection of the backflow zones; then sets an axial monitoring surface on the vortex core meridian plane of the intersection of the backflow zones, extracts an axial temperature variation curve, and determines an axial installation position L by using the maximum point of the axial temperature gradient; then sets a radial monitoring surface at the position, extracts a radial temperature variation curve, and determines a radial installation position R by using the maximum point of the radial temperature gradient; finally, a circumferential position θ is determined according to the position of a flame stabilizer, and a three-dimensional installation position is comprehensively obtained. The application is a direct design method facing a combustion physical field, can accurately install the detector in a high ion concentration area, and effectively solves the problems of weak and unstable signals caused by poor position design.

Description

Technical Field

[0001] This invention relates to the field of aero-engine component design technology, and in particular to a method for designing the position of an ion flame detector in an afterburner. Background Technology

[0002] An ionization flame detector is a key component of the afterburner ignition system in an aero-engine, used to detect whether the afterburner has been successfully ignited. Its working principle is based on the conductivity of charged ions in high-temperature combustion gases: when the afterburner ignites, the flame generated by fuel combustion ionizes the medium between the detector electrodes, forming a conductive circuit and generating an ion current signal. This signal is acquired by the controller, and when the current value reaches a preset threshold, the system determines that the afterburner is engaged.

[0003] In practical applications, weak or unstable ion current signals detected by the ion flame detector frequently cause the cockpit afterburner activation indicator to flash or trigger false alarms. This directly threatens flight safety and can easily lead pilots to misjudge the engine's operating status.

[0004] Studies have shown that one of the root causes of this problem lies in the improper design of the ion flame detector's installation location. The detector's sensing element is not accurately located in the core region of the combustion chamber where the ion concentration is highest and most stable. As the engine's afterburner power changes from low to full, the fuel supply and flame front position both change. If the detector's initial installation location is unreasonable, it cannot effectively cover the high ion concentration area under various operating conditions, resulting in insufficient signal under specific conditions.

[0005] Currently, a common method to solve such problems is "post-processing" physical adjustment. For example, patent application CN113654805A discloses a spatial position adjustment device and method for an ion flame detector. This method involves trial assembly, measuring the actual position parameters H1 and H2, comparing them with empirical values, and then using specialized tooling to physically bend and adjust the detector's installation angle to improve detection performance.

[0006] However, this method has significant limitations: First, it is a post-incident troubleshooting method, which is cumbersome and inefficient, increasing the manufacturing and testing costs of the engine; second, this method relies heavily on the experience accumulated through numerous tests on specific engine models, lacking universal applicability and unable to serve as a forward design method to guide the development of new engine models; third, this method only indirectly affects the detection effect by adjusting the spatial geometric distance, without directly relating it to the core physical fields inside the combustion chamber (such as temperature field and flow field) that determine ion concentration. Therefore, the adjusted position may not be the theoretically optimal position with the highest ion concentration and the most stable signal.

[0007] Therefore, there is an urgent need for a forward design method that can accurately and efficiently determine the optimal installation position of the ion flame detector during the engine design stage, so as to solve the problem of weak and unstable signal from the source. Summary of the Invention

[0008] The purpose of this invention is to overcome the shortcomings of existing technologies and provide a method for designing the position of an ion flame detector in an afterburner. This method is a forward design approach based on CFD combustion simulation and directly oriented towards the combustion physics field, aiming to solve the technical problem of weak and unstable ion current signals caused by poor detector position design.

[0009] To achieve the above objectives, the present invention provides the following technical solution: A method for designing the position of an ion flame detector in an afterburner includes the following steps: S1: Determine the design input conditions for the afterburner. Using the working parameters of the small afterburner state and the full afterburner state as input conditions, use CFD numerical simulation software to carry out combustion simulation calculations of the afterburner. Obtain the range of the recirculation zone behind the flame stabilizer under the two conditions. Find the spatial intersection of the two recirculation zones to obtain the recirculation zone intersection. S2: Based on the combustion simulation calculation results of step S1, obtain the temperature field distribution data within the intersection of the recirculation zones. Set up an axial monitoring surface on the meridional plane of the vortex core at the intersection of the recirculation zones, extract the airflow temperature data along the axial direction within the axial monitoring surface, plot the airflow temperature variation curve along the axial direction, and calculate the slope of the variation curve. By slope The magnitude of the axial temperature gradient dT / dL is characterized, the axial location of the maximum axial temperature gradient is determined, and the axial coordinate of this location is used to determine the axial installation position of the ion flame detector. ; S3: At the axial position where the maximum axial temperature gradient is located, a radial monitoring surface perpendicular to the airflow axial direction is set up. The airflow temperature data along the radial direction of the afterburner within the radial monitoring surface is extracted, and the airflow temperature variation curve along the radial direction is plotted. The slope of the variation curve is calculated. By slope The magnitude of the radial temperature gradient dT / dR is characterized, the radial position corresponding to the maximum radial temperature gradient is determined, and the radial coordinates of this radial position are used to determine the radial installation position of the ion flame detector. ; S4: Based on the circumferential installation position of the flame stabilizer in the afterburner, determine the circumferential installation position θ of the ion flame detector so that the circumferential position of the ion flame detector corresponds to that of the flame stabilizer. S5: Based on the axial position L determined in step S2, the radial position R determined in step S3, and the circumferential position θ determined in step S4, the three-dimensional installation position of the ion flame detector in the afterburner is determined comprehensively.

[0010] Preferably, in step S1, the recirculation zone is a hot recirculation zone, and its length ranges from 3 to 4 times the width of the flame stabilizer slot.

[0011] Preferably, in step S2, the axial monitoring surface is disposed on the vortex meridional surface where the recirculation zones intersect, and extends along the axial direction of the afterburner.

[0012] Preferably, in step S2, the slope of the calculated change curve is... This is achieved by performing differential or difference operations on the temperature change curve of the airflow along the axial direction.

[0013] Preferably, in step S3, the radial monitoring surface is located at the axial position where the maximum value of the axial temperature gradient is located, and extends radially along the intersection of the recirculation zones.

[0014] Preferably, in step S3, the slope of the calculated change curve is... This is achieved by performing differential or difference operations on the radial temperature variation curve of the airflow.

[0015] Preferably, in step S1, the low-power state is the state with the minimum fuel supply; the full-power state is the state with the maximum fuel supply.

[0016] Preferably, in step S1, the operating parameters for the low-power and full-power states include intake air temperature, intake air pressure, intake air velocity, and fuel flow rate.

[0017] Preferably, in step S2, the abscissa of the airflow temperature change curve along the axial direction is the axial distance along the vortex meridian, and the ordinate is the temperature; in step S3, the abscissa of the airflow temperature change curve along the radial direction is the radial distance along the radial monitoring surface, and the ordinate is the temperature.

[0018] The present invention also provides an afterburner, which includes an ion flame detector whose installation position is determined by the method described in any of the preceding claims.

[0019] Compared with the prior art, the beneficial technical effects of the present invention are as follows: (1) Achieves forward design, improving design efficiency and versatility: This invention provides a simulation-driven design method that can be implemented in the engine design stage. Without relying on physical prototypes and extensive test runs to accumulate experience, the optimal installation position of the ion flame detector can be determined efficiently and accurately during the design phase. Based on the physical field characteristics inside the combustion chamber, this method does not depend on empirical parameters specific to any particular engine model, has universal applicability, and can significantly shorten the development cycle of new engine models and reduce development costs.

[0020] (2) Direct correlation with the physical field of combustion, resulting in more scientific and accurate location determination: This invention innovatively establishes a physical correlation between ion concentration, temperature field, and reflux zone. By finding the intersection of reflux zones covering extreme operating conditions, it ensures that the detection area is within a stable reflux zone; by locating the maximum point of the temperature gradient, it accurately pinpoints the core area where the combustion reaction is most intense and the ion concentration is highest. This method directly starts from the physical essence of the combustion reaction, and the determined location is more scientific and accurate, ensuring signal strength and stability from the design source.

[0021] (3) Considering multiple operating conditions and good signal stability: This method uses both minimum and full force extreme operating conditions as inputs, and the intersection of the recirculation regions ensures that the detector's sensing part is within the recirculation region under all force conditions. The point of maximum temperature gradient is usually the region with the most intense reaction, where the detection signal is strongest and most stable. This method ensures that the detector can obtain a stable and reliable ion current signal over a wide range of operating conditions, effectively avoiding signal light flickering or false alarms caused by changes in operating conditions. Attached Figure Description

[0022] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the structures shown in these drawings without creative effort.

[0023] Figure 1 A flowchart illustrating the method for designing the position of an ion flame detector in an afterburner provided by this invention.

[0024] Figure 2 This is a schematic diagram of the recirculation zone behind the flame stabilizer.

[0025] Figure 3 This is a schematic diagram of the temperature distribution in the reflow zone after the flame stabilizer.

[0026] Figure 4 This is a graph showing the trend of airflow temperature variation along the radial direction.

[0027] Figure 5 This is a schematic diagram of the axial position of the ion flame detector.

[0028] Figure 6 for Figure 5 View from A in the middle. Detailed Implementation

[0029] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

[0030] The core idea of ​​this invention is that the ion concentration in the combustion zone is directly related to the intensity of combustion. The more intense the combustion, the faster the chemical reaction rate, and the higher the ion concentration produced. Simultaneously, intense chemical reactions mean rapid energy release, manifested as a sharp change in temperature spatially, i.e., a large temperature gradient. Furthermore, in the recirculation zone behind the flame stabilizer, ions accumulate due to the longer residence time of the airflow, resulting in a relatively high ion concentration.

[0031] Based on the above principle, this invention uses CFD simulation to first determine the spatial region (intersection of recirculation regions) that can form a stable recirculation zone under different loading conditions. Then, it finds the point with the most drastic temperature change (i.e., the point with the largest temperature gradient) in this region, which is used as the location with the highest ion concentration. Finally, this location is determined as the optimal installation location for the flame detector.

[0032] Specifically, the method includes the following steps: Step S1: Determine the intersection of the design input conditions and the reflow zone. First, based on the actual geometric dimensions of the afterburner, a three-dimensional CFD numerical simulation model including key components such as the flame stabilizer is established in a computer.

[0033] Then, two typical operating conditions, low afterburner and full afterburner, are selected as input conditions. Low afterburner represents the critical state at which the afterburner combustion chamber just begins to operate, while full afterburner represents the maximum load operating state. The input operating parameters include, but are not limited to, intake air temperature, intake air pressure, intake air velocity, and fuel flow rate corresponding to each operating condition. In this embodiment, low afterburner is the state at minimum fuel supply; full afterburner is the state at maximum fuel supply.

[0034] Combustion simulation calculations were performed on the afterburner model using commercial CFD numerical simulation software (such as Fluent or CFX) with small afterburner state parameters and full afterburner state parameters as boundary conditions, respectively.

[0035] like Figure 1As shown, after the simulation calculation is completed, the flow field structure behind the flame stabilizer can be clearly obtained in the post-processing interface. After the airflow passes through the V-shaped or slotted flame stabilizer, it will form one or a pair of symmetrical low-velocity recirculation zones behind it. In the combustion state, this region is the hot recirculation zone, which is the main site for stable flame propagation and ion generation and accumulation. Studies have shown that the length of the hot recirculation zone is generally about 3 to 4 times the width of the stabilizer slot.

[0036] In the CFD simulation results, the first recirculation region under the small-force condition and the second recirculation region under the full-force condition are identified and extracted by velocity vector diagrams, streamline diagrams or specific velocity isosurfaces.

[0037] To ensure that the sensing part of the flame detector is covered by the recirculation zone under all applied pressure conditions, this method performs a Boolean intersection operation on the first and second recirculation zones to obtain a common area, namely the recirculation zone intersection. This recirculation zone intersection represents a common area that can maintain stable recirculation characteristics under different operating conditions.

[0038] Step S2: Determine the axial installation position L like Figure 2 As shown, after obtaining the intersection of the reflow regions, the temperature field distribution data inside the region is extracted from the CFD simulation results.

[0039] On the vortex meridional surface where the recirculation zone intersects, a plane extending along the engine axis is set as an axial monitoring surface. This vortex meridional surface is a plane that passes through the central axis of the flame stabilizer and is parallel to the engine axis. It is a symmetrical or characteristic surface of the flow field and temperature field distribution.

[0040] Within this axial monitoring surface, airflow temperature data is extracted at each location along the airflow axial direction. A curve showing the change in airflow temperature along the axial direction is plotted with the axial distance from a reference point (such as the trailing edge of the stabilizer) as the x-axis and temperature as the y-axis.

[0041] The obtained axial temperature change curves are processed to calculate the slope at each point on the curve. The slope can be calculated using mathematical methods such as differentiation or difference. This slope... It reflects the rate of change of temperature with axial distance, that is, the magnitude of the axial temperature gradient dT / dL.

[0042] Within the intersection of the reflow regions, the location with the largest temperature gradient indicates the most vigorous combustion reaction and the highest ion formation rate. Therefore, this method seeks the calculated slope. The point on the curve corresponding to the maximum value of the axial temperature gradient (dT / dL)_max is the location of the maximum axial temperature gradient. The axial distance between this location and the reference point is the optimal axial installation position L of the ionization flame detector.

[0043] Step S3: Determine the radial installation position R After determining the axial installation position L, a plane perpendicular to the axial direction is drawn at this position. This plane intersects with the recirculation zone intersection A, forming a cross section. A radial monitoring surface is then installed on this cross section.

[0044] Within this radial monitoring plane, airflow temperature data is extracted at each location along the radial direction of the afterburner. A curve showing the variation of airflow temperature along the radial direction is plotted with the radial distance from a reference point (such as a point on the vortex meridian) as the x-axis and temperature as the y-axis.

[0045] Similarly, the obtained radial temperature change curves are processed to calculate the slope at each point on the curve. The slope It reflects the rate of change of temperature with radial distance, that is, the magnitude of the radial temperature gradient dT / dR.

[0046] Find the calculated slope The maximum value of the radial temperature gradient (dT / dR) is the point on the curve corresponding to this point, which is the location of the maximum radial temperature gradient (dT / dR)_max. The radial distance of this point relative to the reference point is the optimal radial mounting position R of the ion flame detector. This position ensures that the detector's sensing part is located at the core location of the most intense radial response within the reflow region.

[0047] Step S4: Determine the circumferential installation position θ Combination Figure 5 As shown, the circumferential position of the ionization flame detector typically corresponds to the circumferential distribution of the flame stabilizer to ensure that its sensing part is directly opposite the wake core region of the flame stabilizer. Therefore, in this method, the circumferential position θ of the ionization flame detector is determined by the circumferential installation position of the flame stabilizer, and is usually aligned with its circumferential center.

[0048] Step S5: Comprehensively determine the three-dimensional installation location like Figure 4 and Figure 5 As shown, through the above steps S2, S3, and S4, the axial installation position L, radial installation position R, and circumferential installation position θ of the ion flame detector in the afterburner chamber are obtained, respectively. By combining these three coordinate information, the optimal installation position of the detector can be uniquely determined in the three-dimensional space of the afterburner chamber.

[0049] Step S6: Physical Installation Finally, based on the determined axial mounting position L, radial mounting position R, and circumferential mounting position θ, the mounting base or mounting hole is machined at the corresponding position of the afterburner casing, and the ion flame detector is physically installed at the designated position.

[0050] The installation location determined by the above method ensures that the sensing element is situated at the core of the high ion concentration region in the axial, radial, and circumferential dimensions. Regardless of whether the applied force is low or full, or even during dynamic transitions, fluctuations in the flame front will not cause the sensing element to leave the high ion concentration region, thus guaranteeing the stability and robustness of the ion current signal and solving the problem of weak and unstable signals from the design stage.

[0051] The above description is merely a preferred embodiment of the present invention and does not limit the patent scope of the present invention. Any equivalent structural transformations made using the contents of the present invention's specification and drawings under the inventive concept of the present invention, or direct / indirect applications in other related technical fields, are included within the patent protection scope of the present invention.

Claims

1. A method for designing the position of an ion flame detector in an afterburner, characterized in that, Includes the following steps: S1: Determine the design input conditions for the afterburner. Using the working parameters of the small afterburner state and the full afterburner state as input conditions, use CFD numerical simulation software to carry out combustion simulation calculations of the afterburner. Obtain the range of the recirculation zone behind the flame stabilizer under the two conditions. Find the spatial intersection of the two recirculation zones to obtain the recirculation zone intersection. S2: Based on the combustion simulation calculation results of step S1, obtain the temperature field distribution data within the intersection of the recirculation zones. Set up an axial monitoring surface on the meridional plane of the vortex core at the intersection of the recirculation zones, extract the airflow temperature data along the axial direction within the axial monitoring surface, plot the airflow temperature variation curve along the axial direction, and calculate the slope of the variation curve. By slope The magnitude of the axial temperature gradient dT / dL is characterized, the axial location of the maximum axial temperature gradient is determined, and the axial coordinate of this location is used to determine the axial installation position of the ion flame detector. ; S3: At the axial position where the maximum axial temperature gradient is located, a radial monitoring surface perpendicular to the airflow axial direction is set up. The airflow temperature data along the radial direction of the afterburner within the radial monitoring surface is extracted, and the airflow temperature variation curve along the radial direction is plotted. The slope of the variation curve is calculated. By slope The magnitude of the radial temperature gradient dT / dR is characterized, the radial position corresponding to the maximum radial temperature gradient is determined, and the radial coordinates of this radial position are used to determine the radial installation position of the ion flame detector. ; S4: Based on the circumferential installation position of the flame stabilizer in the afterburner, determine the circumferential installation position θ of the ion flame detector so that the circumferential position of the ion flame detector corresponds to that of the flame stabilizer. S5: Based on the axial position L determined in step S2, the radial position R determined in step S3, and the circumferential position θ determined in step S4, the three-dimensional installation position of the ion flame detector in the afterburner is determined comprehensively.

2. The method for designing the position of an ion flame detector in an afterburner as described in claim 1, characterized in that: In step S1, the reflow zone is a hot reflow zone, and its length ranges from 3 to 4 times the width of the flame stabilizer slot.

3. The method for designing the position of an ion flame detector in an afterburner as described in claim 1, characterized in that: In step S2, the axial monitoring surface is disposed on the vortex meridional surface where the recirculation zones intersect, and extends along the axial direction of the afterburner.

4. The method for designing the position of an ion flame detector in an afterburner as described in claim 1, characterized in that: In step S2, the slope of the change curve is calculated. This is achieved by performing differential or difference operations on the temperature change curve of the airflow along the axial direction.

5. The method for designing the position of an ion flame detector in an afterburner as described in claim 1, characterized in that: In step S3, the radial monitoring surface is located at the axial position where the maximum value of the axial temperature gradient is located, and extends radially along the intersection of the recirculation zones.

6. The method for designing the position of an ion flame detector in an afterburner as described in claim 1, characterized in that: In step S3, the slope of the change curve is calculated. This is achieved by performing differential or difference operations on the radial temperature variation curve of the airflow.

7. The method for designing the position of an ion flame detector in an afterburner as described in claim 1, characterized in that: In step S1, the low-power state is the state with the minimum fuel supply; the full-power state is the state with the maximum fuel supply.

8. The method for designing the position of an ion flame detector in an afterburner as described in claim 7, characterized in that: In step S1, the operating parameters for the low-power and full-power states include intake air temperature, intake air pressure, intake air velocity, and fuel flow rate.

9. A method for designing the position of an ion flame detector in an afterburner as described in any one of claims 1 to 8, characterized in that: In step S2, the abscissa of the airflow temperature change curve along the axial direction is the axial distance along the vortex meridian, and the ordinate is the temperature; in step S3, the abscissa of the airflow temperature change curve along the radial direction is the radial distance along the radial monitoring surface, and the ordinate is the temperature.

10. An afterburner, characterized in that, This includes an ion flame detector whose installation location is determined by the method described in any one of claims 1 to 9.

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