Method and device for stepless control of pressure drop and velocity of powder fuel injection

Abstract

The present application belongs to the field of powder injection technology, and particularly relates to a method and device for stepless regulation of pressure drop and velocity of powder fuel injection, which solves the problem of backfire of the nozzle during engine ignition and thrust regulation in the prior art. The method comprises the following steps: step one: estimating the initial needle opening of the needle-type powder injector, and converting the target injection velocity into the target injection pressure drop; step two: controlling the motor and needle movement until the needle moves to the corresponding needle opening to reach the initial needle opening; step three: obtaining the actual injection pressure drop values of the needle-type powder injector at the upstream and downstream in the working state; step four: performing difference operation on the actual injection pressure drop value and the target injection pressure drop, and sending the adjustment stroke to the motor control module according to the difference operation result, so as to make the motor drive the needle to move again; and step five: repeatedly executing steps three and four until the difference between the actual injection pressure drop value and the target injection pressure drop is less than the set error.

Description

Technical Field

[0001] This invention belongs to the field of powder fuel injection technology, and specifically relates to a method and apparatus for stepless control of powder fuel injection pressure drop and speed. Background Technology

[0002] Powdered fuels, due to their high calorific value and volumetric energy density, are widely used in aerospace propulsion systems such as powder rocket engines, powder ramjet engines, and solid-powder combined ramjet engines. In the engine combustion chamber, powdered fuel is typically injected as fluidized gas at a specific injection pressure drop and velocity to achieve efficient and stable combustion. When the injection pressure drop or velocity is too low, the flame can easily backfire into the nozzle, causing nozzle erosion, blockage, or even an explosion triggered by the flame backfiring into the powder supply system. Conversely, when the injection velocity is too high, the flame may be extinguished, preventing successful engine ignition or causing engine failure. In particular, during engine ignition or thrust adjustment, the combustion chamber pressure often changes by several to tens of times, causing the injection pressure drop and velocity to deviate significantly from stable combustion conditions, potentially leading to the aforementioned backfire, ignition failure, or flameout problems.

[0003] Currently, most commonly used powder injectors are single-hole or annular structures with a fixed area. To prioritize successful ignition, their injection pressure drop and velocity are close to the design point under low-pressure conditions, resulting in injection pressure drop and velocity being far below the design point under high-pressure conditions. This can easily cause nozzle backfire or other safety issues. Therefore, there is an urgent need to develop a method and device that can actively adjust the injection pressure drop and velocity to ensure that they are always at the design point, thereby avoiding the aforementioned safety problems during engine ignition and thrust adjustment. Summary of the Invention

[0004] The purpose of this invention is to provide a method and apparatus for stepless control of the pressure drop and speed of powder fuel injection, so as to solve the technical problem that nozzle backfire is prone to occur during engine ignition and thrust adjustment when using existing powder injectors to inject fuel, which poses a safety hazard.

[0005] The technical solution adopted in this invention is a method for stepless control of powder fuel injection pressure drop and velocity, characterized by the following steps:

[0006] Step 1: Based on the gas flow rate and the target injection velocity, estimate the initial needle opening of the needle-type powder injector, and at the same time convert the target injection velocity into the target injection pressure drop;

[0007] Step 2: Send the action stroke to the motor control module so that the motor and the needle bolt are moved sequentially through the motor control module until the needle bolt moves to the corresponding needle bolt opening degree and reaches the initial needle bolt opening degree;

[0008] Step 3: Obtain the actual injection pressure drop values ​​of the needle-type powder injector upstream and downstream when it is in operation, as measured by the differential pressure sensor;

[0009] Step 4: Perform a differential calculation between the actual value of the injection pressure drop and the target injection pressure drop, and then send an adjustment stroke to the motor control module based on the differential calculation result so that the motor drives the needle to move again;

[0010] Step 5: Repeat steps 3 and 4 until the difference between the actual injection pressure drop and the target injection pressure drop is less than the set error.

[0011] Furthermore, in step one, when estimating the initial needle plug opening of the needle-type powder injector, it is assumed that the powder outlet of the needle-type powder injector is in a homogeneous flow state. The calculation process for estimating the initial needle plug opening of the needle-type powder injector is as follows:

[0012] First, use the following formula [1] to calculate the initial spray area A required for the needle-type powder injector. j0 ;

[0013] A j0 =q m,g (ρ g v js [1]

[0014] In formula [1]: q m,g ρ is the gas phase flow rate; g The gas density at the powder injector outlet can be calculated from the powder injector outlet pressure; v js The powder injection velocity is equal to the gas phase injection velocity under homogeneous flow conditions.

[0015] Then, based on the geometric structure of the needle-type powder injector, a functional relationship between the injection area and the needle opening of the needle-type powder injector is established, and the initial injection area A obtained by formula [1] is calculated. j0 Substituting into the functional relationship, the initial needle opening is obtained by solving.

[0016] Furthermore, in step one, when converting the target injection velocity into the target injection pressure drop, the conversion is performed using the injection dynamics model of the injector.

[0017] The injection dynamics model of the injector is shown in the following equation [2]:

[0018]

[0019] In equation [2]: Δp j Target injection pressure drop; q m,s Δp is the powder flow rate; A0 is the inlet area of ​​the powder injector; Δp sThe pressure drop along the friction can be calculated using the following formula [3]; Δp* is the local pressure drop, which can be calculated using the following formula [4];

[0020] The formula [3] is:

[0021]

[0022] In equation [3]: Fr is the Froude number, Where: v is the airflow velocity, ρ p Let g be the density of the powder / particle material, g be the acceleration due to gravity, and d be the acceleration due to gravity. p denoted as the diameter of the powder particles; m is the mass flow ratio of the powder particles to the fluidizing gas; l is the length of the powder flow channel of the injector, which is related to the geometry of the injector; d is the hydraulic diameter of the flow cross section of the powder flow channel of the injector, which is related to the geometry of the injector.

[0023] The formula [4] is:

[0024]

[0025] In equation [4]: ​​ξ is the local loss coefficient; ε u This represents the velocity ratio of the powder phase to the gas phase.

[0026] The present invention also provides an apparatus for stepless control of powder fuel injection pressure drop and speed in accordance with the above method, which is characterized by:

[0027] Including computers;

[0028] The computer is used to perform the method of claim 1.

[0029] Furthermore, the device also includes a needle-type powder injector, a differential pressure sensor, and a motor control module;

[0030] The needle-type powder injector includes a motor, a needle connected to the motor output shaft, and a housing fitted onto and slidably connected to the needle. The needle can extend and retract within the housing under the drive of the motor to adjust the needle opening of the needle-type powder injector, thereby changing the spraying area. A first pressure measuring port is provided at the powder inlet of the needle-type powder injector or at the outlet of the upstream pipeline supplying powder to it. A second pressure measuring port is provided at the powder outlet of the needle-type powder injector or at an adjacent downstream device connected to it.

[0031] The two pressure input interfaces of the differential pressure sensor are connected to the first pressure measuring port and the second pressure measuring port respectively, and the output terminal of the differential pressure sensor is connected to the computer; the differential pressure sensor is used to measure the actual injection pressure drop value upstream and downstream of the needle-type powder injector when it is in working state, and transmits the actual injection pressure drop value to the computer;

[0032] The motor control module is used to control the movement of the motor;

[0033] The computer is connected to the motor control module.

[0034] Furthermore, in order to keep the structure simple and to make it very convenient to adjust the needle opening, thereby realizing the adjustment of the injection area, the motor is connected to one end of the needle.

[0035] The housing is fitted onto the other end of the needle plug, forming an annular powder flow channel extending along the axial direction of the needle plug. The end of the housing near the motor is slidably connected to the needle plug, forming a closed end. The other end of the housing away from the motor is the powder outlet of the needle plug-type powder injector. The inner surface of the housing at the powder outlet end of the needle plug-type powder injector is a first truncated cone shape that tapers inward from the end. The end of the needle plug at the powder outlet end of the needle plug-type powder injector is a second truncated cone shape that tapers inward from the end and matches the first truncated cone shape. The motor drives the needle plug to extend and retract within the housing. By changing the relative position of the second truncated cone and the first truncated cone along the axial direction, the opening of the needle plug of the needle plug-type powder injector is adjusted.

[0036] A powder inlet channel communicating with the annular powder flow channel is provided on the side of the housing near the closed end. The end of the powder inlet channel that communicates with the outside is the powder inlet of the needle-type powder injector.

[0037] Furthermore, in order to make the needle-type powder injector suitable for injecting powders with relatively poor flowability compared to liquids, the powder flow channel located between the first and second cones in the annular powder flow channel is defined as the conical expansion section of the annular powder flow channel.

[0038] The annular powder flow channel further includes a converging section and a straight annular pipe section; the converging section, the straight annular pipe section, and the conical annular expansion section are arranged sequentially according to the powder flow direction.

[0039] The shape of the inner surface of the shell corresponding to the convergent section is formed by the first cylinder and the third truncated cone arranged in sequence according to the powder flow direction, with the large end of the third truncated cone close to the first cylinder, sharing an adjacent bottom surface with the first cylinder; the shape of the inner surface of the shell corresponding to the straight ring tube section is a second cylinder; the diameters of the small end face of the third truncated cone, the second cylinder, and the small end face of the first truncated cone are all equal;

[0040] The diameter of the needle plug located in the converging section and the straight ring section is equal, and it is equal to the diameter of the small end face of the second truncated cone.

[0041] The annular powder flow channel is designed in this way, which allows for a smooth transition in powder flow due to the presence of a converging section; and the presence of straight annular pipe sections ensures the stability of powder flow.

[0042] Furthermore, the axis of the powder inlet channel is perpendicular to the axis of the needle plug in a non-plane configuration, and the axis of the powder inlet channel is translated away from the needle plug in a plane perpendicular to the needle plug by a distance equal to the radius of the cross-section of the powder inlet channel, and then becomes tangent to the first cylindrical surface. This configuration allows the powder to enter the annular powder channel in a tangential swirling manner, avoiding uneven circumferential distribution of powder within the annular powder channel.

[0043] Furthermore, in order to achieve a smoother transition in powder flow, the taper of the third truncated cone is 45°±10°.

[0044] Furthermore, in order to prevent powder dune-like deposition caused by abrupt changes in the profile and to improve the stability of the gas-solid two-phase flow, the length of the straight annular pipe section along the needle plug axis is 100mm±50mm.

[0045] The initial distance between the two conical surfaces corresponding to the conical ring expansion section in the direction perpendicular to the needle bolt axis is equal to the initial distance between the two cylindrical surfaces corresponding to the straight ring section in the direction perpendicular to the needle bolt axis.

[0046] The beneficial effects of this invention are:

[0047] (1) The needle-bolt opening of the needle-bolt powder injector in this invention can be steplessly adjusted in real time, thereby enabling real-time stepless control of the injection area. During injection, the needle-bolt opening can be adjusted in real time according to the required gas flow rate and target injection speed to obtain the target injection pressure drop corresponding to the target injection speed, ensuring that the injection pressure drop and injection speed are always at the design point during injection, avoiding safety problems such as nozzle backfire during engine ignition and thrust adjustment. Therefore, this invention solves the technical problem that nozzle backfire is prone to occur during engine ignition and thrust adjustment when using existing powder injectors for fuel injection, posing a safety hazard. The method and device for stepless control of powder fuel injection pressure drop and speed of this invention can ensure stable engine operation and efficient thrust adjustment.

[0048] (2) Based on the principle of negative feedback, the needle opening is pre-adjusted first, and then the actual value of the injection pressure drop measured by the differential pressure sensor and the target injection pressure drop are differentially calculated. Based on the differential calculation result, the needle opening is finely adjusted. The injection pressure drop accuracy can be controlled within ±2.5%, and high-precision control of injection pressure drop and injection speed can be achieved.

[0049] (3) In this invention, the needle opening is pre-adjusted based on the initial needle opening prediction, that is, the initial injection area prediction and the injection dynamics model of the two-phase injector; then, based on the negative feedback principle, the needle opening is finely adjusted; the control method of pre-adjustment plus fine adjustment combination greatly improves the adjustment speed of the needle-type powder injector.

[0050] (4) This invention provides a needle-type powder injector configuration with stepless adjustment of the injection area, and the annular powder flow channel configuration of the needle-type powder injector is more suitable for the injection of powders with relatively poor flowability compared to liquids. The relevant optimization parameters of the annular powder flow channel are also given. Attached Figure Description

[0051] Figure 1 This is a system schematic diagram of an embodiment of stepless control of powder fuel injection pressure drop and speed using the method and apparatus of the present invention;

[0052] Figure 2 This is a schematic diagram of the needle-type powder injector in an embodiment of the present invention;

[0053] Figure 3 It is along Figure 2 Cross-sectional view of line AA;

[0054] Figure 4 This is a schematic diagram of the powder distribution state within the flow channel of the needle-type powder injector in an embodiment of the present invention;

[0055] Figure 5 This is a schematic diagram of the static pressure change curve inside the flow channel of the needle-type powder injector in an embodiment of the present invention;

[0056] Figure 6 The curves showing the change of the target injection pressure drop and the actual injection pressure drop over time during the process of adjusting the powder flow rate from a small flow rate to a large flow rate when the injection pressure drop and speed of powder fuel are continuously controlled using the method and device of the present invention.

[0057] Figure 7 The image shows the powder injection from a needle-type powder injector when the injection pressure drop and speed of powder fuel are infinitely controlled using the method and apparatus of this invention.

[0058] (a): The powder flow rate is low;

[0059] (b): The powder flow rate is a large flow rate.

[0060] The labels in the diagram are explained as follows:

[0061] 1-Needle-type powder injector, 11-Motor, 12-Needle, 13-Housing, 14-Annular powder flow channel, 141-Converging section, 142-Straight annular pipe section, 143-Conical annular expansion section, 15-Powder inlet flow channel, 2-Differential pressure sensor, 3-Data acquisition module, 4-Motor control module, 5-Computer. Detailed Implementation

[0062] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments.

[0063] See Figure 1 and Figure 2 The present invention provides a method for stepless control of powder fuel injection pressure drop and velocity, comprising the following steps:

[0064] Step 1: Based on the gas flow rate and the target injection velocity, estimate the initial needle opening of the needle-type powder injector 1, and at the same time convert the target injection velocity into the target injection pressure drop;

[0065] Step 2: Send the action stroke to the motor control module 4, so that the motor control module 4 can control the motor 11 and the needle bolt 12 to move sequentially until the needle bolt 12 moves to the corresponding needle bolt opening degree to reach the above-mentioned initial needle bolt opening degree.

[0066] Step 3: Obtain the actual injection pressure drop values ​​of the needle-type powder injector 1 upstream and downstream when it is in operation, as measured by the differential pressure sensor 2;

[0067] Step 4: Perform a differential calculation between the actual value of the injection pressure drop and the target injection pressure drop, and then send an adjustment stroke to the motor control module 4 based on the differential calculation result so that the motor 11 drives the needle bolt 12 to move again.

[0068] Step 5: Repeat steps 3 and 4 until the difference between the actual injection pressure drop and the target injection pressure drop is less than the set error.

[0069] During the injection process, if it is necessary to adjust the engine thrust, return to step one, and execute steps one through five again based on the gas flow rate and target injection speed corresponding to the engine thrust adjustment.

[0070] In step one above, when estimating the initial needle plug opening of the needle-plug type powder injector 1, it is assumed that the powder outlet of the needle-plug type powder injector 1 is in a homogeneous flow state. The calculation process for estimating the initial needle plug opening of the needle-plug type powder injector 1 is as follows:

[0071] First, use the following formula [1] to calculate the initial spray area A required for the needle-type powder injector 1. j0 ;

[0072] A j0 =q m,g (ρ g v js [1]

[0073] In formula [1]: q m,g ρ is the gas phase flow rate; g The gas density at the powder injector outlet can be calculated from the powder injector outlet pressure; v js The powder injection velocity is equal to the gas phase injection velocity under homogeneous flow conditions.

[0074] Then, based on the geometric structure of the needle-type powder injector 1, a functional relationship between the injection area and the needle opening of the needle-type powder injector 1 is established, and the initial injection area A obtained by formula [1] is calculated. j0 Substituting into the functional relationship, the initial needle opening is obtained by solving. In addition to establishing the functional relationship between the spraying area and the needle opening of the needle-type powder injector 1 in this embodiment, the needle opening can also be directly replaced by the motor stroke to establish the functional relationship between the spraying area and the motor stroke of the needle-type powder injector 1.

[0075] In step one above, when converting the target injection velocity into the target injection pressure drop, the conversion is performed using the injector injection dynamics model.

[0076] The injection dynamics model of the above injector is shown in the following equation [2]:

[0077]

[0078] In equation [2]: Δp j Target injection pressure drop; q m,s Δp is the powder flow rate; A0 is the inlet area of ​​the powder injector; Δp s The pressure drop along the friction can be calculated using the following formula [3]; Δp* is the local pressure drop, which can be calculated using the following formula [4];

[0079] The above formula [3] is:

[0080]

[0081] In equation [3]: Fr is the Froude number, Where: v is the airflow velocity, ρ p Let g be the density of the powder / particle material, g be the acceleration due to gravity, and d be the acceleration due to gravity. p denoted as the diameter of the powder particles; m is the mass flow ratio of the powder particles to the fluidizing gas; l is the length of the powder flow channel of the injector, which is related to the geometry of the injector; d is the hydraulic diameter of the flow cross section of the powder flow channel of the injector, which is related to the geometry of the injector.

[0082] The above formula [4] is:

[0083]

[0084] In equation [4]: ​​ξ is the local loss coefficient; ε u This represents the velocity ratio of the powder phase to the gas phase.

[0085] In specific calculations, the airflow velocity v in the above formula [3] is equal to the ratio of the gas volume flow rate to the cross-sectional area of ​​the powder channel. Specifically, in the configuration of the annular powder channel 14 provided by the present invention, the airflow velocity v is approximately equal to the ratio of the gas volume flow rate to the cross-sectional area of ​​the straight annular pipe section 142; the l is approximately equal to the length of the straight annular pipe section 142; and the d is approximately equal to the hydraulic diameter of the flow section of the straight annular pipe section 142.

[0086] See Figure 1 and Figure 2 The present invention also provides an apparatus for stepless control of the injection pressure drop and speed of powder fuel using the above-described method. The apparatus includes a computer 5; the computer 5 is used to execute the above-described method. In this embodiment, in addition to the computer 5, the apparatus also includes a needle-type powder injector 1, a differential pressure sensor 2, and a motor control module 4.

[0087] See Figure 2 The aforementioned needle-type powder injector 1 includes a motor 11, a needle 12 connected to the output shaft of the motor 11, and a housing 13 slidably connected to and fitted onto the needle 12. The needle 12 can extend and retract within the housing 13 under the drive of the motor 11 to adjust the needle opening of the needle-type powder injector 1, thereby changing the spraying area. To save space, in this embodiment, the motor 11 is preferably a micro stepper motor. A first pressure testing port is provided at the powder inlet of the needle-type powder injector 1 or at the outlet end of the upstream pipeline supplying powder to it. A second pressure testing port is provided at the powder outlet of the needle-type powder injector 1 or on an adjacent downstream device connected to it. See also... Figure 1 The two pressure input interfaces of the differential pressure sensor 2 are connected to the first pressure measuring port and the second pressure measuring port, respectively, and the output terminal of the differential pressure sensor 2 is connected to the computer 5. The differential pressure sensor 2 is used to measure the actual injection pressure drop value upstream and downstream of the needle-type powder injector 1 when it is in working state, and transmits the actual injection pressure drop value to the computer 5. In this embodiment, when the differential pressure sensor 2 transmits the actual injection pressure drop value to the computer 5, it is transmitted through the data acquisition module 3, and the data acquisition module 3 is integrated into the computer 5. In addition to being integrated into the computer 5 as in this embodiment, the data acquisition module 3 can also be an independent external module. The motor control module 4 is used to control the movement of the motor 11; the computer 5 is connected to the motor control module 4.

[0088] For simplicity of structure and ease of adjustment of the needle opening, thereby achieving adjustment of the injection area, see [link to relevant documentation]. Figure 2In this embodiment, the structure of the needle-type powder injector 1 is preferably such that the motor 11 is connected to one end of the needle plug 12; the housing 13 is fitted onto the other end of the needle plug 12, forming an annular powder flow channel 14 extending axially along the needle plug 12; the end of the housing 13 near the motor 11 is in a sealed sliding connection with the needle plug 12, forming a closed end; the other end of the housing 13 away from the motor 11 is the powder outlet of the needle-type powder injector 1, and the inner surface of the housing 13 at the end of the powder outlet of the needle-type powder injector 1 is a first frustum-shaped cone that tapers inward from the end. The end of the needle plug 12 located at the powder outlet of the needle plug powder injector 1 is a second truncated cone shape that gradually narrows inward from the end, which is adapted to the first truncated cone shape. The motor 11 drives the needle plug 12 to move telescopically within the housing 13. By changing the relative position of the second truncated cone and the first truncated cone along the axial direction, the opening of the needle plug of the needle plug powder injector 1 is adjusted. A powder inlet channel 15 communicating with the annular powder flow channel 14 is provided on the side of the housing 13 near the closed end. The end of the powder inlet channel 15 that communicates with the outside is the powder inlet of the needle plug powder injector 1.

[0089] Compared to gases or liquids, gas-solid two-phase fluid flow is more complex, and particles are prone to uneven distribution or localized deposition within the flow channel. To make the needle-type powder injector 1 suitable for injecting powders with relatively poor flowability compared to liquids, see [reference needed]. Figure 2 The powder flow channel located between the first and second truncated cones in the aforementioned annular powder flow channel 14 is defined as the conical annular expansion section 143 of the aforementioned annular powder flow channel 14. In addition to the conical annular expansion section 143, the aforementioned annular powder flow channel 14 preferably also includes a converging section 141 and a straight annular section 142. The converging section 141, the straight annular section 142, and the conical annular expansion section 143 are arranged sequentially according to the powder flow direction. The shape of the inner surface of the housing 13 corresponding to the converging section 141 is as follows: The first cylinder and the third truncated cone are arranged sequentially according to the powder flow direction, with the large end of the third truncated cone close to the first cylinder, sharing an adjacent bottom surface to form the shape. The inner surface of the shell 13 corresponding to the aforementioned straight annular pipe section 142 is shaped like a second cylinder. The diameters of the small end face of the third truncated cone, the second cylinder, and the small end face of the first truncated cone are all equal. The diameters of the pins 12 located in the aforementioned converging section 141 and the straight annular pipe section 142 are equal, and are equal to the diameter of the small end face of the aforementioned second truncated cone. The annular powder flow channel 14 is configured in this way, and due to the presence of the converging section 141, the powder flow achieves a smooth transition; due to the presence of the straight annular pipe section 142, the stability of the powder flow can be guaranteed.

[0090] To avoid uneven circumferential powder distribution after the powder enters the annular powder flow channel 14, see [reference needed]. Figure 3In this embodiment, the axis of the powder inlet channel 15 is perpendicular to the axis of the needle plug 12 in a non-plane. Furthermore, the axis of the powder inlet channel 15 is translated away from the needle plug 12 in a plane perpendicular to the axis of the needle plug 12 by a distance equal to the radius of its cross-section, and then becomes tangent to the cylindrical surface of the first cylinder. This configuration allows the powder to enter the annular powder channel 14 in a tangential swirling manner, avoiding uneven circumferential distribution of powder within the annular powder channel 14.

[0091] See Figure 2 The taper of the aforementioned third truncated cone is preferably 45°±10°, and in this embodiment, it is 45°. This setting ensures a smooth transition in powder flow. In this embodiment, the aforementioned straight annular section 142 is designed according to the homogeneous flow conditions of gas-solid two-phase flow to ensure the uniformity of the two-phase flow. Furthermore, the length of the straight annular section 142 along the axial direction of the needle plug 12 is preferably 100mm±50mm, and in this embodiment, it is 100mm. The length of the straight annular section 142 is long enough to ensure the stability of the flow, but excessive length will lead to energy waste. To prevent abrupt changes in the profile from causing powder dune-like deposition and to improve the stability of the gas-solid two-phase flow, in this embodiment, the initial distance between the two conical surfaces corresponding to the aforementioned conical annular expansion section 143 in the direction perpendicular to the axis of the needle plug 12 is preferably equal to the initial distance between the two cylindrical surfaces corresponding to the aforementioned straight annular section 142 in the direction perpendicular to the axis of the needle plug 12.

[0092] In this embodiment of the invention, a needle-type powder injector 1 specifically designed for powder spraying was used. The flow characteristics of the dense gas-solid two-phase flow within the flow channel of the designed needle-type powder injector 1 were calculated using numerical simulation. A schematic diagram of the powder distribution within the flow channel is shown below. Figure 4 ;See the schematic diagram of the static pressure change curve within the flow channel. Figure 5 .from Figure 4 and Figure 5 It can be seen that the powder particles are evenly distributed in the flow channel and the static pressure transition is smooth, which can ensure the stability of powder flow.

[0093] The method and apparatus of this invention can successfully control the injection pressure drop and injection speed during powder flow rate adjustment. Figure 6 This is a curve showing the change of the target injection pressure drop and the actual injection pressure drop over time during the process of adjusting the powder flow rate from a small flow rate to a large flow rate when the injection pressure drop and velocity of powdered fuel are steplessly controlled using the method and apparatus of this invention. Figure 6 It can be seen that the injection pressure drop is 0.137 MPa under low flow conditions and 0.535 MPa under high flow conditions. The relative fluctuation of the injection pressure drop does not exceed ±2.5%, which can fully meet the control accuracy of the injection parameters. Figure 7The images show powder injection images of a needle-type powder injector when the injection pressure drop and speed of powder fuel are infinitely controlled using the method and apparatus of the present invention, wherein (a): powder flow rate is low; (b): powder flow rate is high.

[0094] The method and apparatus for stepless control of powder fuel injection pressure drop and speed of the present invention can steplessly control injection pressure drop and injection speed in real time, so that injection pressure drop and injection speed are always at the design point during the injection process. This can avoid safety problems such as nozzle backfire during engine ignition and thrust adjustment, thereby ensuring stable engine operation and efficient thrust adjustment.

Claims

1. A method for stepless control of injection pressure drop and velocity of powdered fuel, characterized in that, Includes the following steps: Step 1: Based on the gas flow rate and the target injection velocity, estimate the initial needle opening of the needle-type powder injector (1), and at the same time convert the target injection velocity into the target injection pressure drop; Step 2: Send the action stroke to the motor control module (4) so ​​that the motor (11) and the needle bolt (12) are moved sequentially through the motor control module (4) until the needle bolt (12) moves to the corresponding needle bolt opening degree to reach the initial needle bolt opening degree; Step 3: Obtain the actual injection pressure drop values ​​upstream and downstream of the needle-type powder injector (1) when it is in working state, as measured by the differential pressure sensor (2); Step 4: Perform differential calculation between the actual value of the injection pressure drop and the target injection pressure drop, and then send the adjustment stroke to the motor control module (4) based on the differential calculation result so that the motor (11) drives the needle plug (12) to move again; Step 5: Repeat steps 3 and 4 until the difference between the actual injection pressure drop and the target injection pressure drop is less than the set error. The device used in the method includes a needle-type powder injector (1), a differential pressure sensor (2), and a motor control module (4); The needle-type powder injector (1) includes a motor (11), a needle (12) connected to the output shaft of the motor (11), and a housing (13) fitted on the needle (12) and slidably connected to the needle (12). The needle (12) can extend and retract within the housing (13) under the drive of the motor (11) to adjust the opening of the needle of the needle-type powder injector (1) and thus change the spraying area. A first pressure measuring port is provided at the powder inlet of the needle-type powder injector (1) or at the outlet of the upstream pipeline that supplies powder to it. A second pressure measuring port is provided at the powder outlet of the needle-type powder injector (1) or at the adjacent downstream device connected to it. The two pressure input interfaces of the differential pressure sensor (2) are connected to the first pressure measuring port and the second pressure measuring port respectively, and the output end of the differential pressure sensor (2) is connected to the computer (5); the differential pressure sensor (2) is used to measure the actual value of the injection pressure drop upstream and downstream of the needle-type powder injector (1) when it is in working state, and transmits the actual value of the injection pressure drop to the computer (5); The motor control module (4) is used to control the movement of the motor (11); The motor (11) is connected to one end of the needle plug (12); The housing (13) is fitted onto the other end of the needle plug (12), forming an annular powder flow channel (14) extending axially along the needle plug (12); the end of the housing (13) near the motor (11) is slidably connected to the needle plug (12) to form a closed end; the other end of the housing (13) away from the motor (11) is the powder outlet of the needle plug type powder injector (1), and the end of the inner surface of the housing (13) at the powder outlet of the needle plug type powder injector (1) is a first truncated cone shape that gradually narrows from the end, and the end of the needle plug (12) at the powder outlet of the needle plug type powder injector (1) is a second truncated cone shape that gradually narrows from the end and is adapted to the first truncated cone shape; the motor (11) drives the needle plug (12) to move telescopically within the housing (13), and the needle plug opening of the needle plug type powder injector (1) is adjusted by changing the relative position of the second truncated cone and the first truncated cone along the axial direction; A powder inlet channel (15) communicating with the annular powder channel (14) is provided on the side of the housing (13) near the closed end. The end of the powder inlet channel (15) communicating with the outside is the powder inlet of the needle-type powder injector (1). The powder flow channel located between the first and second cones in the annular powder flow channel (14) is defined as the conical ring expansion section (143) of the annular powder flow channel (14); The annular powder flow channel (14) further includes a converging section (141) and a straight annular pipe section (142); the converging section (141), the straight annular pipe section (142), and the conical annular expansion section (143) are arranged in sequence according to the powder flow direction; The inner surface of the shell (13) corresponding to the convergent section (141) is shaped as a first cylinder and a third truncated cone arranged in the direction of powder flow, with the large end of the third truncated cone close to the first cylinder, sharing an adjacent bottom surface with the first cylinder; the inner surface of the shell (13) corresponding to the straight ring pipe section (142) is shaped as a second cylinder; the diameters of the small end face of the third truncated cone, the second cylinder, and the small end face of the first truncated cone are all equal; The diameters of the needle plugs (12) located in the converging section (141) and the straight ring section (142) are equal, and they are equal to the diameter of the small end face of the second truncated cone. The axis of the powder inlet channel (15) of the needle-type powder injector (1) is perpendicular to the axis of the needle (12) in a different plane. After the axis of the powder inlet channel (15) is translated in a plane perpendicular to the axis of the needle (12) away from the needle (12) by a distance equal to the radius of the cross-section of the powder inlet channel (15), it becomes tangent to the cylindrical surface of the first cylinder.

2. The method for stepless control of powder fuel injection pressure drop and velocity according to claim 1, characterized in that: When estimating the initial needle plug opening of the needle-type powder injector (1) in step one, it is assumed that the powder outlet of the needle-type powder injector (1) is in a homogeneous flow state. The calculation process for estimating the initial needle plug opening of the needle-type powder injector (1) is as follows: First, use the following formula [1] to calculate the initial spray area A required for the needle-type powder injector (1). j0 ; A j0 =q m,g / (r g v js ) [1]; In formula [1]: q m,g ρ is the gas phase flow rate; g The gas density at the powder injector outlet can be calculated from the powder injector outlet pressure; v js The powder injection velocity is equal to the gas phase injection velocity under homogeneous flow conditions. Then, based on the geometric structure of the needle-type powder injector (1), a functional relationship between the injection area and the needle opening of the needle-type powder injector (1) is established, and the initial injection area A calculated by equation [1] is used. j0 Substituting into the functional relationship, the initial needle opening is obtained by solving.

3. The method for stepless control of powder fuel injection pressure drop and velocity according to claim 2, characterized in that: When converting the target injection velocity into the target injection pressure drop as described in step one, the conversion is performed using the injection dynamics model of the injector. The injection dynamics model of the injector is shown in the following equation [2]: In equation [2]: Δp j Target injection pressure drop; q m,s Δp is the powder flow rate; A0 is the inlet area of ​​the powder injector; Δp s The pressure drop along the friction can be calculated using the following formula [3]; Δp* is the local pressure drop, which can be calculated using the following formula [4]; The formula [3] is: In equation [3]: Fr is the Froude number, Where: v is the airflow velocity, ρ p Let g be the density of the powder / particle material, g be the acceleration due to gravity, and d be the acceleration due to gravity. p denoted as the diameter of the powder particles; m is the mass flow ratio of the powder particles to the fluidizing gas; l is the length of the powder flow channel of the injector, which is related to the geometry of the injector; d is the hydraulic diameter of the flow cross section of the powder flow channel of the injector, which is related to the geometry of the injector. The formula [4] is: In equation [4]: ​​ξ is the local loss coefficient; ε u This represents the velocity ratio of the powder phase to the gas phase.

4. An apparatus for stepless control of powder fuel injection pressure drop and velocity in accordance with the method of claim 1, characterized in that: Includes a computer (5), which is connected to the motor control module (4); The computer (5) is used to perform the method of claim 1.

5. The device for stepless control of powder fuel injection pressure drop and speed according to claim 4, characterized in that: The taper of the third truncated cone is 45°±10°.

6. The device for stepless control of powder fuel injection pressure drop and speed according to claim 5, characterized in that: The length of the straight ring section (142) along the axial direction of the needle plug (12) is 100mm ± 50mm; The initial distance between the two conical surfaces corresponding to the conical ring expansion section (143) in the direction perpendicular to the axis of the needle plug (12) is equal to the initial distance between the two cylindrical surfaces corresponding to the straight ring tube section (142) in the direction perpendicular to the axis of the needle plug (12).

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