GB/T 47709-2026Test method for the measurement of pressure fluctuation induced by the rotor of a ducted propulsor (English PDF)

Foreword

The symbols given in Table 1 are applicable to this document.

2 Flowchart of measurement uncertainty analysis using the GUM method

11.2 Calculation of measurement uncertainty in catheter pulsating pressure test Based on the influencing factors of catheter pulsation pressure test measurements, the main input quantities affecting the measurement are. test water density, propeller rotation... The calculation process for speed, propeller diameter, accuracy of measuring equipment (including sensors, amplifiers, data acquisition cards, etc.) and repeatability is shown in Table 2.

12 Test Report The test report should include the following.

a) Test number and name;

b) Testing instruments and equipment;

d) Experimental objective;

e) Testing basis;

f) Specimen test type;

g) Test installation and test conditions;

h) Experimental results and brief analysis;

i) Test results. Relevant data and charts from the experiment are included in the experiment report as attachments.

5 Test Instruments and Meters

5.1 Miniature Pulsating Pressure Sensor Miniature pulsating pressure sensors should meet the following requirements.

a) The outer diameter is no greater than 5mm, or less than 3% of the rotor model diameter;

b) The height is no more than 12mm, or less than 6% of the rotor model diameter;

c) The measured frequency response range is greater than 10kHz;

d) The measuring range is no greater than.200 kPa and the accuracy is no greater than 0.5%.

5.2 DC Amplifier For DC amplifiers used to amplify pulsating pressure signals, the maximum amplification factor should not be less than 1000 times, and the accuracy should not exceed 0.1%. The amplifier should provide an external excitation power supply output.

5.3 Dynamic Signal Acquisition Card The data acquisition A/D card used for dynamic signal acquisition has no fewer channels than the number of pulsating pressure measurement points, and each channel can sample simultaneously. The channel's highest sampling frequency is no less than 10kHz, the A/D conversion resolution is 16 bits or higher, and it has external triggering and internal timing. Clock-triggered sampling function and clock function.

5.4 Speed Encoder An incremental speed encoder should be used to acquire the rotor speed signal. The speed encoder should have both multi-pulse and single-pulse signal output functions, and The number of multi-pulse signals per revolution shall not be less than 128.

7 Test Similarity Criteria

7.1 Geometric Similarity The ship and propeller models are all made and manufactured to scale with the actual objects to ensure geometric similarity.

7.2 Similarity of motion The Reynolds number Rnm(0.75R) of the blade section chord at 0.75R on the rotor of the propeller model exceeds the critical Reynolds number, and is calculated according to formula (1).

7.3 Similar Power In the experiment, the total load factor of the propeller model was equal to that of the actual model, achieving the goal of dynamic similarity between the model and the actual model. That is, the model... The total thrust coefficient is equal to the actual total thrust coefficient. KTm = KTs, and KTm and KTs are calculated according to formulas (2) and (3). (3)

8 Pre-test measurement requirements

8.1 Requirements for Test Equipment and Instruments The equipment and instruments used in the test should meet the following requirements.

a) The test water should be clean and transparent;

b) Each ship and propeller model has a unique identifier;

c) All instruments and meters used in the test are within their metrological validity period;

d) The instrument should be powered on for at least 15 minutes before measurement.

8.2 Determination of Experimental Parameters The procedure for determining experimental parameters is as follows:

a) Test pressure. Ensure that the thruster does not generate cavitation, and that the ambient pressure in the circulating water tank/pool during the test is less than the pulsating pressure. Maximum range of the pressure sensor.

b) Test rotation speed. determined based on the equal load coefficient condition and water velocity.

c) Test water velocity. Determined to meet the conditions of supercritical Reynolds number and equal load factor, and in conjunction with the rotational speed.

d) Propeller rotor diameter. The diameter of the propeller model should ideally be between 180mm and 250mm. The specific dimensions should be determined based on the design of the boat model. The design and installation, similarity criteria for testing, and electrical characteristics of the drive motor are comprehensively considered.

9 Test Measurement Procedure

9.1 Model Assembly The assembly process for the experimental model is as follows:

a) Install a watertight motor, speed encoder, and tail shaft in the boat model and adjust them to be aligned with the boat's axis.

b) The model mounting frame is hoisted to the working section of the water tank/pool, and the boat model is fixed to the model mounting frame by the airfoil spar or connecting rod.

c) Adjust the position of the sword or connecting rod on the mounting bracket so that the axis of the boat model is parallel to the center line of the working section.

d) The test model is mounted on the tank/pool model mounting bracket, ensuring a secure connection.

e) When installing the catheter pulsating pressure sensor, ensure that the pressure sensor's sensing surface is flush with the inner surface of the catheter, and that the sensor mounting hole is within... The inner surface of the catheter is free of burrs.

f) After the catheter pulsating pressure sensor is installed and fixed, the gap between its outer circle and the inner circle of the mounting hole should not exceed

0.2 mm. The gap was filled with a soft material to reduce its size.

g) The circumferential and axial sensor signal lines are fixed inside the guide wire groove of the conduit, and the filler material is used to make the wires and the outer surface of the conduit smooth. Transition. The sensor cable is introduced into the boat model using conduit and then led out of the tank/pool.

9.2 Determination of DC Amplifier Gain Factor and Calibration of Pulsating Pressure Sensor Based on the upper limit of the measurement frequency and the signal strength, appropriately set the low-pass filter frequency (10 times the leaf frequency) and amplification factor of the DC amplifier. (After balancing the DC component, the output voltage should ideally be 3V~5V under normal test conditions.) Before the test, calibrate each sensor to adapt to pressure changes. Equilibrium coefficient. After the coefficient calibration is completed, the DC component of the pressure can be balanced.

9.3 Catheter Pulsating Pressure Measurement Based on the actual operating conditions of the vessel, and following the principles of equal load factor and exceeding the critical Reynolds number, appropriate water velocity and rotational speed are selected, and the microcomputer... The system synchronously acquires K pulsating pressure signals for each rotor revolution triggered by pulse signals, continuously acquires voltage signals for N revolutions (N >100), and maintains... The data is stored for analysis. The specific process is shown in Figure 1, and the specific measurement steps are as follows:

a) The test rotational speed and water velocity, determined jointly by the equal load factor and 8.2b) and 8.2c), are matched to ensure the safe operation of the pump-jet propulsion system. To a certain specified speed (water speed) V and rotational speed n;

b) After the pump-jet propulsion model has been running stably for 5-10 minutes, the DC pressure component of the amplifier output can be balanced, and a certain... The time-domain signals of duct pulsating pressure and rotational speed at a specified speed are used to confirm whether the information is stable and whether the periodicity is obvious and reasonable.

c) After confirming that the pulsating pressure and speed signals are normal, measure the time-domain signals of the pulsating pressure and speed under a specified speed condition and save them. as a result;

11 Uncertainty Analysis of Experimental Measurement Results

11.1 Methods for Analysis of Uncertainty in Experimental Measurements The method for analyzing measurement uncertainty shall comply with the provisions of ISO /IEC Guide 98-3.2008, and the determination of measurement uncertainty using the GUM method shall be based on the following. The analysis steps are as follows, and the general analysis process is shown in Figure 2.

a) Define the measurement clearly;

b) Clearly define the measurement methods, conditions, standards, instruments, or systems used;

c) Establish a measurement model for the measurand and analyze the sources of uncertainty that have a significant impact on the measurement results;

d) Evaluate the standard uncertainty of each input quantity;

e) Calculate the combined standard uncertainty;

f) Determine the expanded uncertainty. Figure