KR100408093B1 - Measurement Method of Horizontal Six-Component Thrust - Google Patents

Abstract

The present invention relates to a method for measuring the six-component of the thrust generated against the combustion gas discharged from the rocket engine, the combustion gas generated by the combustion of the propellant during the performance test in the liquid rocket engine ground test through the nozzle It relates to a six-component horizontal type thrust measurement method that is transmitted to the reaction force through the engine adapter installed on the top of the engine when injected during.

Conventional load cells have the drawback that unwanted thrust values are measured by load components other than the direction of the load cells provided by mutual interference.

Therefore, in the present invention, in the measurement of thrust in the liquid rocket engine ground test, a calibration load cell and a measurement load cell are installed for 6 components and a force applied to the calibration load cell is applied to the calibration constant of the thrust measuring device itself. The first step of obtaining the calibration constant when the engine is mounted, the second step of performing the calibration based on the calibration constant obtained in the first step, and the matrix of calibration constants applied in the second step are two or more. It consists of a third step of applying and verifying the calibration force at the same time to improve the accuracy of the measurement by directly obtaining the calibration constants when the engine as well as the structure of the thrust measuring device itself is actually mounted.

Description

Measurement Method of Horizontal Six-Component Thrust

The present invention relates to a method for measuring the six-component of the thrust generated against the combustion gas discharged from the rocket engine, the combustion gas generated by the combustion of the propellant during the performance test in the liquid rocket engine ground test through the nozzle It is related to a six-component horizontal thrust verification method that is transmitted to the reaction force through the engine adapter installed on the top of the engine when injected during.

When performing rocket combustion test, if misalignment and stirling characteristics of thrust are obtained, it is necessary to measure the force in each direction very precisely.

In multi-component measurements, amplifying the measured component multiplies the complexity due to the interference between the measuring systems and the effect of each component on the mounting error of the rocket.

Interference between each measurement system is affected by the characteristics of the flexure supporting the rocket, the load cell characteristics, and the rocket's support mechanism.

In addition, the installation accuracy of the rocket is influenced by the operator's work proficiency such as the level of the test bench, the precision of the attachment part, and the installation error of the rocket attachment.

Also, in the actual combustion test, unwanted thrust values are measured by load components other than the direction of the load cell in which load cells in each direction are installed due to mutual interference.

It was not possible to carry out the calibration of the engine mounting and the structure itself, no two or more calibrations were possible, and no verification was possible.

The present invention is to measure the thrust component of the horizontal six-component force transmitted to the reaction force through the engine adapter installed on the top of the engine when the combustion gas generated by the combustion is injected into the atmosphere through the nozzle during the performance test in the liquid rocket engine ground test do.

The present invention applies a force to the calibration load cell when the calibration and measurement load cells are installed for each of the six components, respectively, and directly calculates the calibration constants when the engine is actually mounted as well as the structure of the thrust measurement device itself. The present invention provides a thrust measurement method that increases the accuracy of the measurement.

The present invention is characterized in that it is possible to perform calibration on the engine mounting and the structure itself by obtaining a six-component calibration matrix through calibration, and to verify by applying two or more calibrations simultaneously to a matrix composed of calibration constants.

1 is a schematic diagram of a six-component horizontal thrust measurement of the present invention

Figure 2 is a definition of the thrust vector of the present invention Figure 3 is a coupling relationship diagram between the calibration and measurement load cell of the present invention Figure 4 is a state diagram of the installation of the measurement load string of the present invention Figure 5 State diagram

The present invention relates to a schematic diagram of a six-component horizontal thrust measurement as shown in FIG. 1 wherein the origin of the coordinates is at the center of the live bed and the thrust is evaluated at the nozzle throat of the engine.

In the present invention, in the measurement of the thrust in the liquid rocket engine ground test, a calibration load cell and a measurement load cell are installed for 6 components and a force is applied to the calibration load cell so that the calibration constant and the engine of the thrust measuring device are mounted. The first step of obtaining a correction constant when

A second step of performing calibration based on the calibration constants obtained in the first step;

The matrix of calibration constants applied in the second step is composed of a third step of verifying by applying two or more calibration forces simultaneously, as shown in FIG. Is the measurement load cell for the actual measurement, Is a combination of an actuator for applying calibration force and a calibration load cell for measuring calibration force, an actuator for applying calibration force symmetrically on the same plane to apply an ideal calibration force for each measurement load cell, and a calibration force for measuring calibration force The load cell combination is arranged as shown in FIG. 3. In the load cell combination, a measurement load string 1 is installed in two directions of the live bed 2, and a calibration load string 10 is installed in the other directions. The load string is composed of a load cell and a universal flexure, and has a mechanism for transmitting only the force in the central axis direction of the string. ) Is a universal flexure (4, 4 ') which is a mechanical device capable of transmitting an axial force to the load cell (5) for measurement and its both ends as shown in FIG. The load rod 1 for measurement is mounted between the live bed 2 and the fixed bed 3 so that the live bed 2 coupled with the measurement object (engine) is placed on a three-dimensional space. When the deformation occurs in the live bed (2) and other structures due to thrust loads due to the mechanical characteristics of the two universal flexures (4, 4 '), 5) can be positioned at right angles to the axis of the applied load to reduce the error caused by the deviation of the mechanism or structure or the thrust deviation to ensure the accuracy of the measurement. During the calibration operation to correct the errors caused by the deformation of the structure that occurs when the external interference and the external load of the mechanism installed between the live bed (2) and the fixed bed (3), such as 5 Unlike the measurement, the load cell 5 is equipped with a universal flexure 4 and an actuator 12 for applying the calibration force, and the other side of the load cell 5 is used to provide the information about the force. A rod eye 11 for transferring to the bed 2 is mounted. The rod eye 11 is a kind of joint, which is formed in the form of a pin and a ring, and there is a gap therebetween, so It is separated and has a mechanism that does not interfere with accurate thrust measurement in actual combustion test. During the calibration operation, the ring 12 of the rod eye 11 is moved forward and backward by the actuator 12, so that the ring and the pin come into contact with the live bed. (2) has a structure that can apply the corrective force of the tension and compression generated in the actuator 12. The hydraulic actuator is a control panel and a separate panel through a computer and dedicated software In this case, the horizontal type is used to classify the direction of measurement of the thrust measuring device (engine installation method). Even in the same type of measuring device, the horizontal type and the vertical type have the effect of gravity, Different analysis methods should be used in consideration of the engine weight effect.

The ideal force balance equation is

Load balance

Moment equilibrium

This is expressed as a determinant.

Since zero load cells in each direction interfere with each other, unwanted thrust values are measured by load components other than the direction components of the installed load cells.

Therefore, in the actual combustion test, it is necessary to newly consider the data reduction equation for accurate thrust value measurement.

Ideal calibration of load cells due to the ideal balance of forces ) And a load cell for measuring the position of the corresponding load when the corrective force is applied using the actuator attached to it. Only the force should be detected, however. In practice, all measurement load cells are connected to a live bed so that forces are detected in all measurement load cells by the characteristics and interference of the six-component horizontal thrust measurement device itself, i.e. one calibration force. The force is measured on the six load cells for measurement, and the force measured at the load cell becomes a signal including all the interference between the load cells, the characteristics of the six-component horizontal thrust measuring device itself, and various error factors. As shown in Figure 6, each calibration load cell (each calibration load cell is equipped with a hydraulic cylinder capable of applying calibration force) and six measurement load cells are ideally subjected to a force balancing equation such as Will be affected by each other. Therefore, this correlation needs to be identified and corrected. As shown in FIG. 3, the calibration force (F _i ) is used by using one of the six calibration load cells (each calibration load cell is equipped with a hydraulic cylinder capable of applying calibration force). _] ) Is applied to the structure connected to the engine to be measured, and the characteristics of how the structures connected to the engine affect each other through the signals measured by the six measurement load cells (L _i] ) installed on the structure. If the equation is expressed as Equation 4, the correction constant can be obtained through this Equation 4. If this is expressed as Equation 4, it can be expressed as Equation 4 below.

In this case, it is not a problem to install the engine to be measured because it is a process of determining the effect of the structure on which the engine to be tested is mounted and the six load cells for measurement. When performed, the calibration load vector F and the measurement load cell signal vector L have a relationship as shown in Equation 5 below.

The above matrix A is used as a calibration constant to correct for the structural error caused by the connection of the live bed and the loadstring. The matrix A takes into account the calibration of six measuring load cells for each of six distributed load components (calibration forces). 36 factors in total If all 36 calibration constants are known, the relationship between the measured signal value and the ideal load distribution in the load cell can be known. The ideal load distribution F is the component of the thrust vector generated during the actual test. In the same way, the process of finding 36 calibration constants is a process of finding the relationship between the load cell signal and the thrust.

Therefore, the following equation (6) can be obtained.

Where T is the thrust vector, F is the force vector applied for calibration, L is the actual signal vector from the load cell, J is the ideal Jacobian matrix describing the force balance, and A is the calibration matrix.

The calibration method is as follows through this calibration matrix.

Performing calibration refers to a procedure for making the measured thrust value most similar to the thrust generated during the test, taking into account the error factors of the structure as a whole. After identifying and correcting the error characteristic, the actual test can be performed to make more reliable measurement.

Therefore, when the desired load value is input from the PC, a proportional value is controlled to drive the actuator to apply a load to the load cell for calibration.

In this case, a row vector composed of a calibration constant as shown in Equation 4 may be configured from an output from the load cell for measuring the six-component.

Thus, the iterative procedure for six components can construct a matrix A of calibration constants of 6 × 6, Comprehensively includes the load cell characteristics in the structure, manufacturing errors of the structure.

Although the above-described method of performing calibration for independently applied calibration force has been described, the actual thrust can be regarded as a situation in which two or more are applied in combination, so the matrix of calibration constants obtained above can be verified by applying two or more calibration forces simultaneously. It is necessary.

At this time, if the applied correction force is F ' , the error E can be evaluated from the relationship as shown in Equation (7).

Thrust characteristics can be calculated using the data reduction equation.

Magnitude of Thrust Vector

-Location of Thrust Vector

Angle of Thrust Vector Equation 10 can be obtained by defining the thrust vector of FIG. 2.

Since the deformation amount of the structure is not large, considering the elastic deformation Can be said to have repeatability, but every time It is not reasonable to obtain and calibrate, so if there are methods and criteria for assessing the degree of calibration, The second and third steps have been invented as a technique to evaluate the degree of correction.However, environmental factors (e.g., abnormal high temperatures, long periods of time) are outside the operating conditions of the designed six-component horizontal thrust measurement device. In case of exposure to period of heavy rain, earthquake, etc.) or when the test has not been performed for a long period of time, the replacement of some parts requires systematic correction from detailed parts. In this test, the liquid rocket engine generates thrust in the nozzle neck as combustion gas is discharged through the nozzle.The purpose of the six-component propulsion measurement is to obtain the thrust characteristics of the test object that is actually applied. This is not it. Therefore, it is necessary to calibrate (convert) the thrust vector generated in the actual engine nozzle neck by using the reaction force generated in the test apparatus during the test. Therefore, the second step is performed through the repeated procedure of the first step. Jacobian matrix J that corrects (converts) the reaction force measured at the structure to the thrust vector at the nozzle neck in relation to the calibration constant matrix A, the engine under test, the structure to which it is coupled, and the application location of the load cell [example in Figure 1]. The third step is to verify the calibration graph of two steps by applying two or more correction forces, and to combine the structure and each load cell in one step. In order to find the correction constants, the combination was used by applying a force with one component. However, in the actual test, the component has a multi-component thrust, which creates a multi-component reaction force in the structure. Therefore, it is necessary to use two or more of the six calibration load cells applied (with a hydraulic cylinder that can apply force). At the same time, the force (F ') is applied to the structure, and at this time, the AL and the actually applied calibration force (F') are calibrated with the calibration matrix (A), which is obtained in two steps using the value (L) measured by the measurement load cell. The difference (E) can be evaluated by.

The present invention provides a horizontal component of the six-component thrust component that is transmitted to the reaction force through the engine adapter installed on the engine when the combustion gas generated by the combustion of the propellant is injected into the atmosphere through the nozzle during the performance test in the liquid rocket engine ground test. It can be measured.

The present invention is to enable the calibration of the engine mounting and the structure itself by obtaining a six-component calibration matrix through calibration, and to enable verification by applying two or more calibrations simultaneously to a matrix composed of calibration constants.

Claims (4)

In measuring thrust in the liquid rocket engine ground test, A first step in which a calibration load cell and a measurement load cell are installed for each of the six components and a force is applied to the calibration load cell to obtain a calibration constant of the thrust measuring device itself and a calibration constant when the engine is mounted; A second step of performing calibration based on the calibration constants obtained in the first step; The matrix of calibration constants applied in the second step is a six-component horizontal thrust verification method, characterized in that consisting of a third step of applying the two or more correction force at the same time to verify. The method of claim 1 wherein the correction constant is A six-component horizontal thrust verification method characterized by the following formula. The thrust vector of claim 1, wherein the second step constitutes a calibration matrix A of the calibration constants of 6 × 6 through repeated procedures for six components. T is the thrust vector, F is the force vector applied for calibration, L is the actual signal vector from the load cell, J is the ideal Jacobian matrix describing the balance of forces, A is the calibration matrix, 6-component horizontal thrust verification method characterized in that the load cell characteristics in the structure. The method of claim 1, wherein the third step is a matrix from the relationship of E = F'-AL when the applied corrective force is F '. 6-component horizontal thrust verification method characterized in that the error can be evaluated through.