TEST SETUP

Technical field of the invention

The invention relates to a liquid fuel rocket engine test setup that ensures the accuracy of the data received from the load cell during the test by calibrating the load cell used in the static ignition test of the liquid fuel rocket engine with full automation.

State of the Art

Liquid fuel rocket engines are known as a type of rocket engine oxidizer and fuel of which are in the liquid phase. Their fuel tanks consist of two parts, and they are large- volume, heavy rockets. There are flammable and combustible liquid tanks in the rocket body. Advantages of liquid fuel rockets are that the combustion rate in the combustion chamber can be controlled, the material sprayed from the holes with an equal intensity can be burned homogeneously since the combustion chamber has a perforated structure, the exhaust is cooled by the fuel itself, and that they can carry more than one target load (two or three satellites or more than one nuclear fuel head).

It is necessary to measure the performance and reliability of rocket engines, which are used extensively in the Space and Defence Industry, during the development, evaluation and verification of their designs. One of the tests performed in this process is the static ignition tests. One of the most important parameters to be measured in static ignition tests is the thrust value produced by the engine. In many rocket engines, lateral thrust and rolling moment are also generated by means of the thrust vector control (TVC) system, along with axial thrust. In the development, evaluation and design verification processes of thrust systems, measurements related to their performance and reliability are needed in all axes. In static ignition tests, the measured thrust force, combustion chamber pressure and various temperature data are the main measurement parameters. Different methods can be used for thrust measurement, such as direct force measurement, measurement of the output properties of exhaust gases, and momentum balance. Direct force measurement is the most widely used of these methods. A special mechanism is also required to measure the thrust force directly. These force-measuring devices basically consist of a fixed cage, movable carrier system, support columns, load cells and calibration system and are called “thrust measurement system”.

It is difficult to calibrate a six-axis load cell mounted on a liquid fuel rocket engine hardware, but it is necessary to calibrate the load cell as measurement values may deviate over time due to mechanical changes in the load cell structure. Especially the tests performed on the liquid fuel rocket engine assembly are expensive and challenging in terms of operating conditions. It is important to calibrate the load cell before each test.

Loadmeters require periodic calibration by comparison with a reference standard loadmeter or a standard weight. Calibration should be performed with a series of increasing forces according to international standards. In most cases, a test machine or standard weight can be used to calibrate. In current applications, six axis load cells are removed from the position where they are used/operated, and the calibration process is done manually. This process is carried out using a similar type of load cell with calibration. This method used causes loss of precision in measurement, additional labour and time loss.

The most basic and common method in load cell calibration currently used is to calibrate using a standard/dead weight. This method is not suitable for use in liquid fuel rocket engine equipment, since the calibration interval is limited, and it is not possible to perform it where the test cell is used/operated. It is an inadequate approach in terms of sensitivity and the range of loads that can be applied.

Another method used in the state of the art is to connect the pre-calibrated load cell in series and calibrate the test load cell with the help of a computer. This method is not sufficient in terms of sensitivity since the load cell is not in the location where it is operated or used.

There are also calibration systems in the art adapted by applying dead weights to the liquid fuel rocket engine equipment. The biggest handicap of these approaches is that they allow calibration on a single axis. In addition, since dead weight limits the load range of the application, this approach is insufficient in terms of the load range that can be applied and the number of axes it can calibrate. The mentioned approaches also have problems in terms of performing the calibration process while the liquid fuel rocket engine is mounted on the test setup. One leading problem is the calibration process when the engine weight is on the loadmeter. In this case, it creates sensitivity problems.

The prior art application numbered “CN100529703C” relates to a calibration device of a six-axis force sensor suitable for a wide range and a large size. Wherein, the six-axis force is indicated as (F _x , F _y and F _z ) (M _x , M _y and M _z ). It is stated that this system can be used especially in aviation robots, space station placement simulation, and rocket engine thrust test. Calibration operations are performed on the relevant axis by using the fixing holes.

The application numbered “CN105004525A” in the state of the art relates to a calibration system and method developed for the test thrust of a liquid fuel rocket engine. It comprises hydraulic system, force transmission system, measuring system and control system. The measurement and control system comprises a servo drive connected to an electro-hydraulic servo valve. Servo drive includes two modes, manual and automatic. In the system of the invention, the calibration stability point and the deviation range are first calculated on the computer. The computer controls the servo drive to extract the hydraulic oil according to the calibration stability point, thus controlling the output force value of the double acting cylinder. The computer converts the output signal of the sensor into an output force value and then these values are compared.

In the state of the art, force ring and weight are also used in the calibration of six-axis load cells. The force ring type loading adopts the rod method, and the load force value is also read by the force ring. This type of loading allows for a greater load force, but the reading accuracy is lower, and the cost of the high precision force ring is high. In the weight type calibration, the tilt weight is adopted to provide the standard loading force and the tilt weight is used as a direct reference. Force value accuracy is relatively high but not suitable for large scale force. In the article titled "Design and implementation of a thrust vector control (TVC) test system” in the state of the art, the dynamic behaviour of the TVC Performance Test System designed for thrust vector controlled solid fuel rocket engine development tests is examined. In the test system, the forces and moments produced by the rocket engine during ignition were measured according to six degrees of freedom. The designed test system can measure the axial thrust, lateral thrust components and rolling moment of rocket engines producing axial thrust up to 50 kN.

During the six-axis load cell operations/uses used on the liquid fuel rocket engine static ignition test equipment, the calibration deteriorates over time or as a result of a sudden situation and makes inaccurate measurements. Incorrect values measured from the load cell cause the static ignition test to fail, but also cause the test to be repeated. This situation causes great losses in terms of time and cost.

Since existing similar applications are based on disassembling the loadmeter and calibrating it elsewhere, or performing the calibration using standard/dead weights, there are time, labour, measurement range and accuracy problems.

As a result, there is a need for a new technology that can overcome the disadvantages described above, ensures the accuracy of the data received from the load cell during the test by calibrating the load cell with full automation, includes a hydraulic system and thereby in which the entire measuring range of the load meter can be scanned, through which high precision can be obtained by performing the calibration process at the location where the load cell is operated/used by being separated from the liquid fuel rocket engine test setup with automation, and that is practical to use and low in cost.

Brief Description and Aims of the Invention

The most important aim of the invention is to calibrate the load cell used in the static ignition test of the liquid fuel rocket engine with full automation to ensure the accuracy of the data received from the load cell during the test. Double validation is performed to ensure the accuracy of the data received from the load cell.

Another aim of the invention is to calibrate all axes of the six-axis loadmeter independently from one another. In the system developed for this purpose, a uniaxial loadmeter is used. In addition, the rocket engine is installed on the test setup and the full capacity of the loadmeter is scanned. Another aim of the invention is to scan the entire measuring range of the loadmeter. There is a hydraulic system for this purpose. The force data obtained by converting the pressure values from the hydraulic system into force and the data from the calibrated uniaxial loadmeter are compared with the data of the tested loadmeter with the help of a computer, and the calibration process is performed.

Another aim of the invention is to obtain high sensitivity. For this purpose, during the calibration process to be carried out with computer control, the liquid fuel rocket engine is separated from the test equipment by automation and the calibration process is carried out at the location where the load cell is operated/used.

Description of Figures:

FIGURE-1 ; is the general view of the liquid fuel rocket engine test setup calibration system that is the subject of the invention.

FIGURE-2; is the general view of the liquid fuel rocket engine test setup calibration system that is the subject of the invention.

FIGURE-3; is the drawing that gives the appearance of the part that separates and connects the liquid fuel rocket engine and the test setup, which are the subject of the invention.

FIGURE-4; is the drawing that gives the view of the part that performs the calibration of the six-axis loadmeter that is the subject of the invention.

FIGURE-5; is the drawing that gives the appearance of the six-axis loadmeter axes selection process in the calibration system that is the subject of the invention.

Definition of Elements/Parts Composing the Invention

Parts and elements in the figures are numbered in order to better explain the system that ensures the accuracy of the data received from the load cell during the test by calibrating the load cell used in the liquid fuel rocket engine test setup with full automation developed with this invention, and The equivalent of each number is given below: 1. Liquid fuel rocket engine test setup

2. Calibrated loadmeter

3. Rocket engine connection interface

4. Axis selection system reels

5. Axis selection system motor

6. Main hydraulic piston

7. Auxiliary hydraulic piston

8. Uniaxial loadmeter

9. Axis selection system rope

Detailed Description of the Invention

The invention relates to a liquid fuel rocket engine test setup that ensures the accuracy of the data received from the load cell during the test by calibrating the load cell used in the static ignition test of the liquid fuel rocket engine with full automation. This process can be performed without any operator intervention.

The system developed with the invention is a liquid fuel rocket engine test setup (1 ) comprises the rocket engine connection interface (3), which is positioned in conjunction with calibrated loadmeter (2) verified with data from a calibrated uniaxial loadmeter (8) with hydraulic system consisting of both the main hydraulic piston (6) and the auxiliary hydraulic piston (7), and enables the equipment to be tested to be integrated into the system so that it is not disassembled in subsequent calibration processes; at least one auxiliary hydraulic piston (7) enabling the reassembly of the liquid fuel rocket engine separated from the calibrated loadmeter (2) with the test equipment; the main hydraulic piston (6), which enables the measurement range of the loadmeter to be determined, measures the pressure value and enables the calibration to be made by comparing the data of the loadmeter (2) tested with this pressure value; the axis selection system reel (4), which enables the axis selection to be made by calibrating the load cell with the axis selection system motor (5) by positioning it in connection with the loadmeter (2) and the rocket engine connection interface (3) being tested; axis selection system motor (5), which is combined with the uniaxial loadmeter (8) after the calibration process is completed, enabling axis selection in the six-axis load meter; axis selection system rope (9), which is located on each axis and enables axis selection with its tensioned structure; uniaxial loadmeter (8) which enables the calibration of all axes of the six-axis tested loadmeter (2) independently from one another by comparing the data of the tested loadmeter with the help of a computer.

In this system, while the liquid fuel rocket engine is mounted on the equipment, firstly, it disconnects the connection between the rocket engine and the load cell and takes the weight of the engine on the uniaxial loadmeter (8). When the load cell is idle, the axis selection system is calibrated with the motor (5) and the axis selection system reels (4), and the axis selection is made. Then, a force is applied in the measuring range to the loadmeter to be calibrated by the hydraulic system consisting of the main hydraulic piston (6) and the auxiliary hydraulic piston (7) within the system. The calibration process is performed by comparing the force data obtained by converting the pressure values obtained from the hydraulic system consisting of the main hydraulic piston (6) and the auxiliary hydraulic piston (7) into force, and the data from the calibrated uniaxial loadmeter (8) with the data of the tested loadmeter with the help of a computer.

The loadmeter and the liquid fuel rocket engine are activated and separated from each other. After the calibration process is completed, the axis selection system is combined with the motor (5) and the uniaxial loadmeter (8). This process is provided by back and forth movement by means of the hydraulic system consisting of the main hydraulic piston (6) and the auxiliary hydraulic piston (7). The part that is active during the calibration of the loadmeter is shown as dashed in Figure-3 and Figure-4. The axis selection and reset of the loadmeter and the force applied during the test are performed in this section.

The axes are calibrated by performing the same operations on all axes of the six-axis loadmeter. After the calibration process is completed, the liquid fuel rocket engine, which is separated from the loadmeter by the hydraulic system consisting of the main hydraulic piston (6) and the auxiliary hydraulic piston (7), is reassembled with the test equipment.

During the calibration process to be carried out with computer control, the liquid fuel rocket engine is separated from the test equipment by automation, and the calibration process is performed at the location where the load cell is operated and/or used, ensuring high sensitivity. With the developed system, the calibration process can be performed while it is mounted on the liquid fuel rocket engine test setup (1 ).

In the liquid fuel rocket engine test setup calibration system, the part where the axis selection reset is performed with the axis selection system motor (5) and its structural parts that ensure the merging and integration of the elements in the system comprises a calibrated uniaxial loadmeter (8) and axis selection system reels (4) used in axis selection. The axis to be calibrated is selected using the axis selection system motor (5) and the axis selection system reel (4). This process is provided by regulating the tension of the axis selection system ropes (9) on each axis. Axis selection system ropes (9) are made of steel.

By means of the rocket engine connection interface (3) in the test setup, the test equipment (liquid fuel rocket engine) to be tested is integrated into the system and there is no need to remove it from the system for subsequent calibration processes. In this way, labour is also reduced.

In the developed system, all axes of the six-axis calibrated loadmeter (2) can be calibrated independently of one another by using a uniaxial loadmeter (8).

The measurement of the pressure values taken from the hydraulic system is measured with a manometer over the hydraulic system. The data from the forcemeter is verified by the conversion of the pressure values (P=F/A) taken from the hydraulic system. At the same time, a second verification process is performed with a pre-calibrated uniaxial loadmeter. Since both pressure and uniaxial loadmeters are used in the system developed with the invention, the precision is increased.

The system performs the calibration process of the six-axis load cell with its own electronic equipment at the operating/use location. Since the hydraulic principle consisting of the main hydraulic piston (6) and the auxiliary hydraulic piston (7) is used for the load applied during the calibration, there is no force problem. By means of the hydraulic system consisting of the main hydraulic piston (6) and the auxiliary hydraulic piston (7), the measuring range of the calibrated loadmeter can be scanned.

The entire calibration process is carried out with full automation using a computer. All parts in the system are in communication and control with the computer. In addition, the data obtained as a result of the measurement of the pressure values taken from the hydraulic system are collected and recorded in the computer.

In the liquid fuel rocket engine test setup, it is fixed on the test setup with bolts and remains mounted before and after the tests. While the calibration system is in the passive position during the rocket engine ignition test, it becomes active when calibration is requested. Said calibration system is also computer controlled. The data received from the sensors are recorded with the computer and the hydraulic system and axis selection system motors are controlled with the help of the computer.

The system developed with the invention provides savings in terms of labour and time while achieving high precision. Another aspect of the developed system that distinguishes it from previous techniques is the verification of the loadmeter (2), which is calibrated with the data it receives from both the hydraulic system and the calibrated loadmeter during calibration. This provides high accuracy in terms of precision. Precision rate can also be specified as 1 %. With this system, calibration can be performed in the range of 0-250 kN.

With the developed system, the calibration of the six-axis loadmeter on the liquid fuel rocket engine test setup can be performed with high precision, saving time and labour compared to other applications. It does this by using its own electronic infrastructure and hydraulic principle at the location of the loadmeter. In addition, with the developed system, the loadmeter can be calibrated again and again without the need for disassembly on the test setup where the liquid fuel rocket engine is mounted.

In the system that ensures the accuracy of the data received from the load cell during the test by calibrating the load cell used in the static ignition test setup of the liquid fuel rocket engine with full automation, stainless steel (304 quality) is used in structural parts, rocket motor connection interface (3), and uniaxial load meter (8).