Thrust coefficient calculation method and test system for pintle nozzle

Abstract

The invention provides a calculation method and a test system for thrust coefficients of a pintle nozzle, and mainly aims to accurately measure the thrust coefficients of the pintle nozzle under different working conditions. The method comprises the following steps: on the basis of a pintle nozzle test model, according to an engine balance pressure calculation formula, calculating a corresponding thrust coefficient under a specified combustion chamber pressure; the test system applying the thrust coefficient calculation method comprises an engine combustion chamber, an ignition device, a servo control system, a sealing connection structure, a static frame, a movable frame, a thrust sensor and a bearing pier, the pressure intensity of the combustion chamber and the throat area of an engine can be accurately controlled in the test process, and the thrust coefficient of the spray pipe under the concerned working condition is obtained.

Description

Technical Field

[0001] The invention relates to the field of variable thrust solid rocket engines, and in particular to a method for testing a nozzle thrust coefficient. Background Art

[0002] The throat-plug solid rocket engine is a relatively mature variable thrust engine that is currently widely studied. The engine thrust is adjusted by changing the throat area through a throat plug that moves along the axial direction of the nozzle.

[0003] In the design of engine schemes, the thrust coefficient of the nozzle is an important performance parameter. For a throat plug nozzle, a shock wave may be generated in the nozzle expansion section when the throat plug is actuated, and the shock wave position will change according to the different actuation positions of the throat plug. Therefore, the thrust coefficient formula derived based on one-dimensional isentropic flow is No longer applicable. The thrust coefficient of the throat plug nozzle is related to the combustion chamber p c , ambient pressure p a , Ratio of nozzle exit area to throat area In addition to the above, it is also related to the flow state of the gas in the nozzle. c , throat area A t It may vary within a large range and the operating conditions are complex. The existing technology cannot accurately measure the thrust coefficient of the pintle nozzle under different operating conditions. Summary of the invention

[0004] In order to overcome the shortcomings of the prior art and accurately measure the thrust coefficient of a pintle nozzle under different working conditions, the present invention provides a method and a system for testing the thrust coefficient of a throat plug nozzle.

[0005] A method for calculating thrust coefficient of a throat bolt nozzle includes a throat bolt nozzle test model and a thrust coefficient calculation method; the throat bolt nozzle test model includes a first throat bolt nozzle, a second throat bolt nozzle and a third throat bolt nozzle; the thrust line of the first throat bolt nozzle is collinear with the thrust line of the third throat bolt nozzle; the thrust line of the second throat bolt nozzle is perpendicular to the thrust line of the first throat bolt nozzle; a plane rectangular coordinate system is established with the horizontal plane where the thrust line of the second throat bolt nozzle is located; the thrust line of the second throat bolt nozzle is the X-axis; the projection of the thrust line of the first throat bolt nozzle and the thrust line of the third throat bolt nozzle on the plane rectangular coordinate system is the Y-axis; the second throat bolt nozzle is located in a direction where the X-axis is greater than zero; the first throat bolt nozzle and the third throat bolt nozzle are arranged on both sides of the origin of the Y-axis;

[0006] The steps of the thrust coefficient calculation method are:

[0007] According to the engine balance pressure formula:

[0008]

[0009] Among them, p c is the combustion chamber pressure, a is the burning rate coefficient, ρ is the propellant density, C* is the characteristic velocity, and n is the pressure exponent; A b A is the burning surface of the charge; t-tot is the total throat area;

[0010] After the propellant is determined, the burning rate coefficient a, propellant density ρ, characteristic velocity C*, and pressure index n are all known constants. b is a known quantity that varies with working time;

[0011] Based on the throat plug nozzle test model and according to the engine balance pressure calculation formula, at the specified combustion chamber pressure p c First, according to the engine balance pressure calculation formula and known parameters, the total throat area A of the three nozzles is calculated. t-tot After the throat area of ​​the second plug-in nozzle is determined, the throat areas of the first plug-in nozzle and the third plug-in nozzle are adjusted to make the total throat area of ​​the three nozzles reach A. t-tot , the combustion chamber pressure p c ;

[0012] According to the specified combustion chamber pressure p c The first throat plug nozzle obtained by the test has a throat area of ​​A t The thrust F at this time, according to the thrust formula F = p c A t C f , the corresponding thrust coefficient C can be calculated f ;

[0013] Change the combustion chamber pressure p c and the throat area A of the second throat plug nozzle t , we can get the thrust coefficient of the second throat plug nozzle at different pressures and different throat areas.

[0014] Furthermore, a test system for calculating the thrust coefficient of a throat plug nozzle is applied, including an engine combustion chamber, an ignition device, a servo control system, a sealing connection structure, a static frame, a dynamic frame, a thrust sensor and a bearing pier;

[0015] The engine combustion chamber comprises a barrel section, a bottom cover and a head; a head is arranged on the top surface of the barrel section; a bottom cover is arranged on the bottom surface of the barrel section; a first through hole, a second through hole and a third through hole are arranged on the outer surface of the head; the position of the first through hole is the same as the position of the first throat plug nozzle of the throat plug nozzle test model; the position of the second through hole is the same as the position of the second throat plug nozzle of the throat plug nozzle test model; the position of the third through hole is the same as the position of the third throat plug nozzle of the throat plug nozzle test model; a first flange seat is arranged in the first through hole; a second flange seat is arranged in the second through hole; a third flange seat is arranged in the third through hole; a first throat plug nozzle is arranged in the first flange seat; a second throat plug nozzle is arranged in the second flange seat; a third throat plug nozzle is arranged in the third flange seat; the head and the barrel section are fixedly connected by a sealing connection structure;

[0016] The engine combustion chamber is arranged on the moving frame;

[0017] The movable frame includes a base and a roller; the base is a rectangular plate; the base is fixedly connected to the bottom cover; the bottom surface of the base is provided with a roller; the engine combustion chamber is perpendicular to the base;

[0018] A dynamic frame is arranged inside the static frame; the static frame includes a load-bearing pier and a base; the base is parallel to the horizontal plane; the load-bearing pier and the dynamic frame are arranged on the top surface of the base; a thrust sensor is arranged on the load-bearing pier; one end of the thrust sensor is fixedly connected to the load-bearing pier; the other end of the thrust sensor is fixedly connected to the engine combustion chamber; the position where the thrust sensor is fixedly connected to the engine combustion chamber is located on the thrust line of the second throat plug nozzle.

[0019] Furthermore, the sealing connection structure includes a bottom flange of the cover, a top flange of the barrel section and bolts; the bottom flange of the cover is arranged at the outer circumference of the bottom surface of the cover; the bottom flange of the cover is a circular ring; a plurality of screw holes are arranged on the end surface of the bottom flange of the cover; the top flange of the barrel section is arranged at the outer circumference of the top surface of the barrel section; the top flange of the barrel section is a circular ring; a plurality of screw holes are arranged on the top flange of the barrel section; the bottom flange of the cover and the top flange of the barrel section are fixedly connected by bolts;

[0020] Furthermore, the first throat plug-type nozzle, the second throat plug-type nozzle and the third throat plug-type nozzle are respectively provided with actuators;

[0021] Furthermore, a fourth through hole is arranged on the outer surface of the head; an ignition device is arranged in the fourth through hole; a fifth through hole is arranged on the outer surface of the head; the fifth through hole is a pressure measuring hole; a pressure sensor is arranged in the fifth through hole; the pressure sensor and the actuator are respectively connected to the servo control system.

[0022] Furthermore, the servo control system includes a controller and control software; the controller is connected to the actuator and the pressure sensor respectively; the controller receives the signal of the pressure sensor, and the control software sends an actuation instruction to the actuator according to the signal of the pressure sensor to drive the throat plug to move axially; after the servo control system collects the combustion chamber pressure, it performs closed-loop control on the throat area of ​​the nozzle, improves the adjustment accuracy of the combustion chamber pressure, and obtains a more accurate thrust coefficient;

[0023] Furthermore, a charge is arranged in the combustion chamber; an insulating structure and a lining are arranged in sequence between the charge, the barrel section, the cover and the bottom cover;

[0024] Furthermore, a thrust transfer structure is provided on the cover; the thrust transfer structure is connected to the engine combustion chamber to facilitate the transmission of thrust; the thrust transfer structure is a rectangular plate; a flange is provided on the bottom surface of the thrust transfer structure; the flange is fixedly connected to the cover; a through hole is provided on the side surface of the thrust transfer structure; the through hole is used to set a thrust sensor;

[0025] Furthermore, the thrust transfer structure and the cover are integrally processed.

[0026] The beneficial effects of the present invention are:

[0027] 1. The present invention designs an engine for testing the thrust coefficient of a throat-plug nozzle. A throat-plug nozzle is installed on quadrant lines I, II, and IV of the engine respectively. The thrust test of the nozzle on the quadrant line I can be realized by adopting a conventional thrust test step structure.

[0028] 2. Continuous adjustment of throat area is achieved by adjusting the throat plug position of the nozzle on the quadrant I line. Combustion chamber pressure regulation is achieved by equally adjusting the throat areas of the nozzles on the quadrant II and IV lines. The thrust generated by the nozzle on the quadrant I line is obtained from the test. The thrust coefficient corresponding to different pressures and different throat areas of the nozzle on the quadrant I line can be calculated according to the thrust formula. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 This is a schematic diagram of the structure of a traditional pintle nozzle;

[0030] Figure 2 Testing the engine structure for thrust coefficient;

[0031] Figure 3 This is a cross-sectional view of the engine;

[0032] Figure 4 It is a top view of the engine combustion chamber;

[0033] Figure 5 It is the combustion chamber structure;

[0034] Figure 6It is the top view of the head;

[0035] Figure 7 This is a schematic diagram of the thrust test bench;

[0036] Figure 8 This is a top view of the thrust test bench;

[0037] In the figure, T1 is the gas outlet; T2 is the throat area that changes with the action of the throat plug; T3 is the throat plug body; T4 is the gas inlet; T5 is the thrust nozzle; 1 is the combustion chamber; 2 is the throat plug nozzle; 3 is the servo control system; 4 is the ignition device; 5 is the sealing connection structure; 6 is the static frame; 7 is the dynamic frame; 8 is the thrust sensor; 9 is the bearing pier; 1a is the bottom cover; 1b is the barrel section; 1c is the head; 1d is the insulation structure; 1e is the lining; 1f is the charge column; 1c-1 is the thrust transfer structure; 1c-2 is the pressure measuring hole; 1c-3 is the first hanging point; 1c-4 is the third flange; 1c-5 is the second flange; 1c-6 is the first flange; 1c-7 is the second hanging point; 1c-8 is the ignition hole. DETAILED DESCRIPTION

[0038] A method for calculating thrust coefficient of a throat bolt nozzle includes a throat bolt nozzle test model and a thrust coefficient calculation method; the throat bolt nozzle test model includes a first throat bolt nozzle, a second throat bolt nozzle and a third throat bolt nozzle; the thrust line of the first throat bolt nozzle is collinear with the thrust line of the third throat bolt nozzle; the thrust line of the second throat bolt nozzle is perpendicular to the thrust line of the first throat bolt nozzle; a plane rectangular coordinate system is established with the horizontal plane where the thrust line of the second throat bolt nozzle is located; the thrust line of the second throat bolt nozzle is the X-axis; the projection of the thrust line of the first throat bolt nozzle and the thrust line of the third throat bolt nozzle on the plane rectangular coordinate system is the Y-axis; the second throat bolt nozzle is located in a direction where the X-axis is greater than zero; the first throat bolt nozzle and the third throat bolt nozzle are arranged on both sides of the origin of the Y-axis;

[0039] The steps of the thrust coefficient calculation method are:

[0040] According to the engine balance pressure formula:

[0041]

[0042] Among them, p c is the combustion chamber pressure, a is the burning rate coefficient, ρ is the propellant density, C* is the characteristic velocity, and n is the pressure exponent; A b A is the burning surface of the charge; t-tot is the total throat area;

[0043] After the propellant is determined, the burning rate coefficient a, propellant density ρ, characteristic velocity C*, and pressure index n are all known constants. bis a known quantity that varies with working time;

[0044] Based on the throat plug nozzle test model and according to the engine balance pressure calculation formula, at the specified combustion chamber pressure p c First, according to the engine balance pressure calculation formula and known parameters, the total throat area A of the three nozzles is calculated. t-tot After the throat area of ​​the second plug-in nozzle is determined, the throat areas of the first plug-in nozzle and the third plug-in nozzle are adjusted to make the total throat area of ​​the three nozzles reach A. t-tot , the combustion chamber pressure p c ;

[0045] According to the specified combustion chamber pressure p c The first throat plug nozzle obtained by the test has a throat area of ​​A t The thrust F at this time, according to the thrust formula F = p c A t C f , the corresponding thrust coefficient C can be calculated f ;

[0046] Change the combustion chamber pressure p c and the throat area A of the second throat plug nozzle t , we can get the thrust coefficient of the second throat plug nozzle at different pressures and different throat areas;

[0047] A test system using a method for calculating the thrust coefficient of a throat plug nozzle includes an engine combustion chamber, an ignition device, a servo control system, a sealing connection structure, a static frame, a dynamic frame, a thrust sensor and a bearing pier;

[0048] The engine combustion chamber comprises a barrel section, a bottom cover and a head; a head is arranged on the top surface of the barrel section; a bottom cover is arranged on the bottom surface of the barrel section; a first through hole, a second through hole and a third through hole are arranged on the outer surface of the head; the position of the first through hole is the same as the position of the first throat plug nozzle of the throat plug nozzle test model; the position of the second through hole is the same as the position of the second throat plug nozzle of the throat plug nozzle test model; the position of the third through hole is the same as the position of the third throat plug nozzle of the throat plug nozzle test model; a first flange seat is arranged in the first through hole; a second flange seat is arranged in the second through hole; a third flange seat is arranged in the third through hole; a first throat plug nozzle is arranged in the first flange seat; a second throat plug nozzle is arranged in the second flange seat; a third throat plug nozzle is arranged in the third flange seat; the head and the barrel section are fixedly connected by a sealing connection structure;

[0049] The sealing connection structure comprises a bottom flange of the sealing cover, a top flange of the barrel section and bolts; the bottom flange of the sealing cover is arranged on the outer circumference of the bottom surface of the sealing cover; the bottom flange of the sealing cover is a circular ring; a plurality of screw holes are arranged on the end surface of the bottom flange of the sealing cover; the top flange of the barrel section is arranged on the outer circumference of the top surface of the barrel section; the top flange of the barrel section is a circular ring; a plurality of screw holes are arranged on the top flange of the barrel section; the bottom flange of the cover and the top flange of the barrel section are fixedly connected by bolts;

[0050] The engine combustion chamber is arranged on the moving frame;

[0051] The movable frame includes a base and a roller; the base is a rectangular plate; the base is fixedly connected to the bottom cover; the bottom surface of the base is provided with a roller; the engine combustion chamber is perpendicular to the base;

[0052] The moving frame is arranged inside the static frame; the static frame comprises a bearing pier and a base; the base is parallel to the horizontal plane; the bearing pier is arranged on the top surface of the base; a thrust sensor is arranged on the bearing pier; one end of the thrust sensor is fixedly connected to the bearing pier; the other end of the thrust sensor is fixedly connected to the engine combustion chamber; the position where the thrust sensor is fixedly connected to the engine combustion chamber is located on the thrust line of the second throat plug nozzle;

[0053] Actuators are respectively arranged on the first throat plug-type nozzle, the second throat plug-type nozzle and the third throat plug-type nozzle;

[0054] A fourth through hole is provided on the outer surface of the sealing head; an ignition device is provided in the fourth through hole; a fifth through hole is provided on the outer surface of the sealing head; the fifth through hole is a pressure measuring hole; a pressure sensor is provided in the fifth through hole;

[0055] The pressure sensor and the actuator are respectively connected to the servo control system;

[0056] The servo control system includes a controller and control software; the controller is connected to the actuator respectively; the controller drives the throat plug to move axially according to the instruction; the pressure sensor is used to collect the combustion chamber pressure, the controller receives the combustion chamber pressure signal, and sends an actuation instruction to the actuator according to the control software; after the servo control system collects the combustion chamber pressure, the throat area of ​​the nozzle is closed-loop controlled to improve the adjustment accuracy of the combustion chamber pressure and obtain a more accurate thrust coefficient;

[0057] A charge is arranged in the combustion chamber; a heat insulation structure and a lining are arranged in sequence between the charge, the barrel section, the sealing cover and the bottom cover;

[0058] A thrust transfer structure is provided on the cover; the thrust transfer structure is connected to the engine combustion chamber to facilitate the transmission of thrust; the thrust transfer structure is a rectangular plate; a flange is provided on the bottom surface of the thrust transfer structure; the flange is fixedly connected to the cover; a through hole is provided on the side surface of the thrust transfer structure; the through hole is used to set a thrust sensor;

[0059] The thrust transfer structure and the cover are processed in an integrated manner.

[0060] The present invention is further described below in conjunction with the accompanying drawings and embodiments.

[0061] The structure and appearance of the thrust coefficient test engine are shown in Figure 2 , engine section view Figure 3 , engine top view see Figure 4 ,Depend on Figure 4 The quadrant lines Ⅰ, Ⅱ, Ⅲ, and Ⅳ are defined as shown, and the quadrant line definitions of each component are consistent with the engine. The engine consists of a combustion chamber, three throat-plug nozzles, an ignition device, a servo control system, and a sealed connection structure. The engine is placed vertically on the ground, and the thrust lines of the three throat-plug nozzles are parallel to the ground. The engine achieves continuous adjustment of the throat area by adjusting the throat position of the nozzle on the quadrant line Ⅰ, and achieves combustion chamber pressure regulation by equally adjusting the throat area of ​​the nozzle on the quadrant lines Ⅱ and Ⅳ. The thrust generated by the nozzle on the quadrant line Ⅰ is obtained by testing. According to the thrust formula F=p c A t C f The thrust coefficient of the nozzle on the quadrant I line corresponding to different pressures and different throat areas can be calculated.

[0062] Combustion Chamber:

[0063] Combustion chamber structure Figure 5 The combustion chamber is composed of a bottom cover, a barrel section, a head, an insulation structure, a liner, and a charge.

[0064] The bottom cover is a stepped disc-shaped structure, and high-strength steel materials such as 30CrMnSiA steel can be selected. Circumferentially evenly distributed threaded holes and through holes are designed respectively. The threaded holes are used to connect with the barrel section, and the through holes are used to connect with the test fixture to play the role of fixing the engine.

[0065] The barrel section is a cylindrical structure, and high-strength steel materials such as 30CrMnSiA steel can be selected. Circumferentially evenly distributed threaded holes and through holes are designed at both ends of the barrel section. The threaded holes are used to connect with the head, and the through holes are used to connect with the bottom cover. The end face is designed with a sealing groove for installing a sealing ring.

[0066] The head is an ellipsoidal structure with three flange seats spaced 90° apart in the circumference. High-strength steel materials such as 30CrMnSiA steel can be used. Figure 6. The outer end of the head is designed with circumferentially evenly distributed through holes for connection with the barrel section. Flange seats are designed on the quadrant lines Ⅰ, Ⅱ, and Ⅳ for installing three throat plug nozzles. The upper surface of the head is designed with pressure measuring holes and ignition holes for installing pressure sensors and ignition electrical connectors. The positions of the pressure measuring holes and ignition holes are based on the structural layout and there are no special requirements. The outer edges of the quadrant lines Ⅱ and Ⅳ of the head extend out of the lifting point for engine lifting. The outer edge of the quadrant line Ⅲ of the head is designed with a thrust transfer structure, which has sufficient strength to transfer thrust to the thrust sensor. The thrust transfer point is colinear with the thrust line of the throat plug nozzle installed on the quadrant line Ⅰ. The thrust transfer structure can be processed as a whole with the head, or it can be processed separately and then welded to the head, or it can be processed separately and connected to the head with a plug-in structure.

[0067] The insulation structure can be made of nitrile or EPDM insulation materials commonly used in solid rocket engines, which are bonded to the inside of the combustion chamber to resist the ablation of high-temperature combustion gas in the combustion chamber.

[0068] The lining layer can be made of a grade that is chemically compatible with the insulation material and the propellant, and can be sprayed on the insulation structure of the cast propellant to enhance the adhesion of the propellant and relieve stress.

[0069] The grain can use conventional solid propellants, can be cast against the wall or freely loaded, and the grain structure can be designed as needed.

[0070] Laryngeal plug nozzle:

[0071] The three throat plug nozzles are installed on the flange seats of the head's quadrant lines I, II, and IV respectively. The nozzle thrust line is collinear with the quadrant line, and the nozzle outlet faces outward. The thrust transfer point on the head's quadrant line III is collinear with the throat plug nozzle thrust line on the quadrant line I.

[0072] Ignition device:

[0073] The ignition device includes an ignition electrical connector and an ignition charge. The ignition charge is bonded to the surface of the charge column; the ignition electrical connector is installed on the head, the inner cable is connected to the ignition charge, and the outer cable receives the ignition current to ignite the ignition charge, which in turn ignites the charge column.

[0074] Servo control system:

[0075] The servo control system includes three actuators, one pressure sensor, one controller, cables and control software. The three actuators are installed on three throat plug nozzles respectively, and drive the throat plugs to move axially according to the instructions. The pressure sensor is installed on the head to collect the combustion chamber pressure and provide it to the controller. The controller receives the combustion chamber pressure signal and sends an actuation instruction to the actuator according to the algorithm of the control software. The cable is used to connect the controller and the actuator, pressure sensor, and power supply for power supply and communication. The control software is installed in the controller to drive the hardware to run, process signals, and send actuation instructions according to the control algorithm.

[0076] Sealed connection structure:

[0077] The sealing connection structure is used for the connection and sealing between the various components of the engine, including bolts, spring washers and sealing rings.

[0078] Thrust test bench:

[0079] Thrust test bench Figure 7 , top view Figure 8 , including a static frame, a dynamic frame, a thrust sensor, and a bearing pier. The dynamic frame has a bearing roller, which is installed on the track of the static frame and can roll along the track direction. The thrust sensor is installed on the bearing pier. The engine is installed on the dynamic frame through the bottom cover. The thrust line of the throat bolt nozzle of the quadrant line I is parallel to the dynamic frame track, and the thrust transfer point of the quadrant line III is in contact with the thrust sensor. The thrust of the throat bolt nozzle of the quadrant line I can be tested by the thrust test bench. By adjusting the throat bolt stroke of the quadrant line nozzle, the throat area of ​​the quadrant line nozzle can be changed to achieve thrust tests with different throat areas.

[0080] Combustion chamber pressure realization method:

[0081] The engine balance pressure formula is: After the propellant is selected, the burning rate coefficient a, propellant density ρ, characteristic velocity C * , pressure index n are known constants, and the burning surface A of the grain b is a known quantity that changes with the working time. In order to achieve the specified combustion chamber pressure p c First, the total throat area A of the three nozzles is calculated based on the engine balance pressure formula and known parameters. t-tot After the nozzle throat area of ​​quadrant Ⅰ is determined, the nozzle throat areas of quadrant Ⅱ and Ⅳ are adjusted to make the total throat area of ​​the three nozzles reach A. t-tot , so that the combustion chamber pressure p c .

[0082] After the servo control system collects the combustion chamber pressure, it can perform closed-loop control on the throat area of ​​the II and IV quadrant line nozzles, thereby improving the regulation accuracy of the combustion chamber pressure.

[0083] In this way, the specified combustion chamber pressure p c The throat area of ​​the nozzle on the quadrant I line obtained by the test is A t The thrust F at this time, according to the thrust formula F = p c A t C f The corresponding thrust coefficient can be calculated. c and the nozzle throat area A on the quadrant I line t , we can get the thrust coefficient of the nozzle on the quadrant I line at different pressures and different throat areas.

[0084] Beneficial effects:

[0085] 1. The present invention designs an engine for testing the thrust coefficient of a throat-plug nozzle. A throat-plug nozzle is installed on quadrant lines I, II, and IV of the engine respectively. The thrust test of the nozzle on the quadrant line I can be realized by adopting a conventional thrust test step structure.

[0086] 2. The throat area is continuously adjusted by adjusting the throat plug position of the nozzle on the quadrant I line, and the combustion chamber pressure is adjusted by adjusting the throat area of ​​the nozzle on the quadrant II and IV lines. The thrust generated by the nozzle on the quadrant I line is obtained by testing. According to the thrust formula F = p c A t C f The thrust coefficient of the nozzle on the quadrant I line corresponding to different pressures and different throat areas can be calculated.

Claims

1. A method for calculating the thrust coefficient of a throat plug nozzle, characterized in that: Including the test model of the plug-on nozzle and the thrust coefficient calculation method; The throat-bolt nozzle test model includes a first throat-bolt nozzle, a second throat-bolt nozzle and a third throat-bolt nozzle; the thrust line of the first throat-bolt nozzle is collinear with the thrust line of the third throat-bolt nozzle; the thrust line of the second throat-bolt nozzle is perpendicular to the thrust line of the first throat-bolt nozzle; a plane rectangular coordinate system is established with the horizontal plane where the thrust line of the second throat-bolt nozzle is located; the thrust line of the second throat-bolt nozzle is the X-axis; the projection of the thrust line of the first throat-bolt nozzle and the thrust line of the third throat-bolt nozzle on the plane rectangular coordinate system is the Y-axis; the second throat-bolt nozzle is located in the direction where the X-axis is greater than zero; the first throat-bolt nozzle and the third throat-bolt nozzle are arranged on both sides of the origin of the Y-axis; The steps of the thrust coefficient calculation method are: According to the engine balance pressure formula: Among them, p c is the combustion chamber pressure, a is the burning rate coefficient, ρ is the propellant density, C* is the characteristic velocity, and n is the pressure exponent; A b A is the burning surface of the charge; t-tot is the total throat area; After the propellant is determined, the burning rate coefficient a, propellant density ρ, characteristic velocity C*, and pressure index n are all known constants. b is a known quantity that varies with working time; Based on the throat plug nozzle test model and according to the engine balance pressure calculation formula, at the specified combustion chamber pressure p c First, according to the engine balance pressure calculation formula and known parameters, the total throat area A of the three nozzles is calculated. t-tot After the throat area of ​​the second plug-in nozzle is determined, the throat areas of the first plug-in nozzle and the third plug-in nozzle are adjusted to make the total throat area of ​​the three nozzles reach A. t-tot , that is, to achieve the combustion chamber pressure p c ; According to the specified combustion chamber pressure p c The first throat plug nozzle obtained by the test has a throat area of ​​A t The thrust F at this time, according to the thrust formula F = p c A t C f , that is, solve the corresponding thrust coefficient C f ; Change the combustion chamber pressure p c and the throat area A of the second throat plug nozzle t , that is, the thrust coefficient of the second throat plug nozzle corresponding to different pressures and different throat areas is obtained.

2. A test system using the method for calculating the thrust coefficient of a throat plug nozzle according to claim 1, characterized in that: It includes an engine combustion chamber, a static frame, a dynamic frame, a thrust sensor and a bearing pier; the static frame includes a base; the base is parallel to the horizontal plane; the dynamic frame and the bearing pier are arranged on the base; the engine combustion chamber is arranged on the dynamic frame; the engine combustion chamber and the bearing pier are connected through the thrust sensor; The engine combustion chamber comprises a barrel section, a bottom cover and a head; a head is arranged on the top surface of the barrel section; a bottom cover is arranged on the bottom surface of the barrel section; the head and the barrel section are fixedly connected by a sealing connection structure; a first through hole, a second through hole and a third through hole are arranged on the outer surface of the head; the position of the first through hole is the same as the position of the first throat bolt nozzle of the throat bolt nozzle test model; the position of the second through hole is the same as the position of the second throat bolt nozzle of the throat bolt nozzle test model; the position of the third through hole is the same as the position of the third throat bolt nozzle of the throat bolt nozzle test model; a first flange seat is arranged in the first through hole; a second flange seat is arranged in the second through hole; a third flange seat is arranged in the third through hole; a first throat bolt nozzle is arranged in the first flange seat; a second throat bolt nozzle is arranged in the second flange seat; a third throat bolt nozzle is arranged in the third flange seat; The moving frame includes a base and a roller; the base is a rectangular plate; the base is fixedly connected to the bottom cover; the roller is arranged on the bottom surface of the base; the engine combustion chamber is perpendicular to the base; a thrust sensor is arranged on the load-bearing pier; one end of the thrust sensor is fixedly connected to the load-bearing pier; the other end of the thrust sensor is fixedly connected to the engine combustion chamber; the position where the thrust sensor is fixedly connected to the engine combustion chamber is located on the thrust line of the second throat plug nozzle.

3. The test system for calculating the thrust coefficient of a throat plug nozzle according to claim 2, characterized in that: The sealing connection structure includes a bottom flange of the cover, a top flange of the barrel section and bolts; the bottom flange of the cover is arranged at the outer circumferential edge of the bottom surface of the cover; the bottom flange of the cover is a circular ring; a plurality of screw holes are arranged on the end surface of the bottom flange of the cover; the top flange of the barrel section is arranged at the outer circumferential edge of the top surface of the barrel section; the top flange of the barrel section is a circular ring; a plurality of screw holes are arranged on the top flange of the barrel section; the bottom flange of the cover and the top flange of the barrel section are fixedly connected by bolts.

4. The test system for calculating the thrust coefficient of a throat plug nozzle according to claim 2, characterized in that: Actuators are respectively arranged on the first throat plug-type nozzle, the second throat plug-type nozzle and the third throat plug-type nozzle.

5. The test system for calculating the thrust coefficient of a throat plug nozzle according to claim 4, characterized in that: A fourth through hole is arranged on the outer surface of the sealing head; an ignition device is arranged in the fourth through hole; a fifth through hole is arranged on the outer surface of the sealing head; the fifth through hole is a pressure measuring hole; a pressure sensor is arranged in the fifth through hole; the pressure sensor and the actuator are respectively connected to the servo control system.

6. A test system for calculating the thrust coefficient of a throat plug nozzle according to claim 5, characterized in that: The servo control system includes a controller and control software; the controller is connected to the actuator and the pressure sensor respectively; the controller receives the signal of the pressure sensor, and the control software sends an actuation instruction to the actuator according to the signal of the pressure sensor to drive the laryngeal plug to move axially.

7. The test system for calculating the thrust coefficient of a throat plug nozzle according to claim 2, characterized in that: A charge is arranged in the combustion chamber; and an insulation structure and a lining are arranged in sequence between the charge and the barrel section, the sealing cover and the bottom cover.

8. The test system for calculating the thrust coefficient of a throat plug nozzle according to claim 2, characterized in that: A thrust transfer structure is arranged on the cover; the thrust transfer structure is connected to the engine combustion chamber to facilitate the transmission of thrust; the thrust transfer structure is a rectangular plate; a flange is arranged on the bottom surface of the thrust transfer structure; the flange is fixedly connected to the cover; a through hole is arranged on the side surface of the thrust transfer structure; the through hole is used to arrange a thrust sensor.

9. A test system for calculating the thrust coefficient of a throat plug nozzle according to claim 8, characterized in that: The thrust transfer structure and the cover are processed in an integrated manner.

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