Test bench for testing an engine and propeller assembly for ice accretion

Abstract

The invention relates to test benches for pieces of aviation equipment and can be used for testing an engine and propeller assembly (an engine with a propeller mounted thereto) for small unmanned aerial vehicles under icing conditions. A test bench for testing an engine and propeller assembly for ice accretion comprises a freezing chamber, a system for supplying power to and controlling the revolutions of the engine and propeller assembly undergoing testing, a system for monitoring the state of the engine and propeller assembly undergoing testing, meters for measuring the air temperature and humidity inside the freezing chamber, a two-phase nozzle for spraying water onto the engine and propeller assembly undergoing testing, and systems for supplying water and compressed air to the two-phase nozzle, wherein, in addition to a compressor with a tank, a pipeline, a filter and a compressed air pressure regulator, the system for supplying compressed air comprises an air dryer. The technical result of the invention is that of providing more accurate test results using a compact and energy efficient test bench.

Description

[0001] Propeller-motor group ice accretion test stand

[0002] Field of technology to which the invention relates

[0003] The invention relates to test benches for elements of aviation equipment and can be used for testing the propeller-motor group (motor with installed propeller) of small unmanned aerial vehicles in icing conditions.

[0004] State of the art

[0005] A rig for testing a propeller-engine group under icing conditions is known [1], containing an aero-refrigeration tube, inside of which hydraulic nozzles are installed that spray water in the direction of the tested propeller-engine group, located there in the tube and secured on a vibration table, as well as a device for controlling the speed of the propeller-engine group, a system for monitoring the state of the propeller-engine group and the climate inside the aero-refrigeration tube.

[0006] The disadvantage of this setup is that a source of compressed, cooled air is required to create an air flow in the refrigeration tube that moves the resulting droplets from the nozzles to the tested propeller-motor group, which leads to the setup being bulky and increased energy consumption.

[0007] A compact rig [2] is also known, consisting of a freezer chamber, a control and monitoring system for the tested propeller-motor group, temperature and air humidity meters inside the chamber, a two-phase nozzle spraying water onto the tested propeller-motor group, and systems for supplying water and compressed air to the two-phase nozzle, the latter consisting of a compressor and a pressure regulator. The tested propeller-motor group and the two-phase nozzle are secured in the freezer chamber inside a narrow transparent tube.

[0008] A disadvantage of this rig is the lack of moisture removal from the compressed air before it is fed to the two-phase nozzle, which leads to an uncontrolled increase in the water content (the mass of water in the form of droplets contained in a unit volume of air) in the resulting aerosol cloud. The increase in water content occurs due to condensation caused by a decrease in air temperature as a result of its throttling through the nozzle. Increased water content will lead to accelerated icing of the propeller-motor group, i.e., to an error in the test conditions. An error also occurs due to the placement of the propeller-motor group in a tunnel, since such a placement leads to an increase in its thrust by tens of percent [3]. During testing on this rig, a constant thrust of the propeller-motor group is not maintained, which leads to an increase in the water content of the air-water flow (w) due to icing of the propeller-motor group propeller and a decrease in the flow velocity (u) through it (w = G / u, where G is the water flow rate through the nozzle [4]).On the other hand, the water content of the air-water flow may decrease during testing due to changes in the water flow rate through the nozzle, a reduction in liquid supply due to gravity, or freezing of the nozzle. All of these factors, both individually and collectively, lead to low test accuracy.

[0009] The claimed invention eliminates the above mentioned disadvantages.

[0010] Disclosure of invention

[0011] The objective of the invention is to create a compact laboratory rig for testing the propeller-motor group of small unmanned aerial vehicles in icing conditions.

[0012] The technical result of the invention consists in increasing the accuracy of test results while maintaining the compactness and energy efficiency of the test bench.

[0013] The technical result is achieved due to the fact that the rig for testing the propeller-motor group for icing contains a freezer, a power supply system and a speed control system for the propeller-motor group being tested, a system for monitoring the condition of the propeller-motor group being tested, air temperature and humidity meters inside the freezer, a two-phase nozzle spraying water onto the propeller-motor group being tested, systems for supplying water and compressed air to the two-phase nozzle, wherein the system for supplying compressed air to the two-phase nozzle, in addition to a compressor with a receiver, a pipeline, a filter and a compressed air pressure regulator, contains an air dryer.

[0014] In addition, the distance between the plane of rotation of the propeller of the tested propeller-motor group and the nearest wall of the freezer is not less than one of its diameters.

[0015] In addition, the freezing chamber additionally contains a pipe installed between the nozzle and the tested propeller-motor group in such a way that the axis of the pipe coincides with the axis of rotation of the propeller-motor group propeller, and the equivalent diameter of the pipe is comparable to or greater than the diameter of the propeller-motor group propeller.

[0016] In addition, the air temperature and humidity meters are installed in the freezer compartment in such a way that the spray torch of the two-phase nozzle does not fall on them.

[0017] In addition, the system for monitoring the condition of the tested propeller-motor group contains a strain gauge, and the power supply and speed control system of the tested propeller-motor group contains a PID controller, which maintains a constant thrust of the propeller-motor group during the test.

[0018] In addition, the water supply system to the two-phase nozzle contains a pressurized water tank, a valve, a pipeline, and a flow meter. Furthermore, the compressed air supply system to the two-phase nozzle additionally contains a compressed air aftercooler installed between the compressor and the filter.

[0019] In addition, the two-phase nozzle has either a flat spray pattern or a full cone shape.

[0020] In addition, a heating element and a temperature sensor are installed on the two-phase nozzle.

[0021] Brief description of the drawings

[0022] Fig. 1 shows the claimed stand (side view);

[0023] Fig. 2 shows a diagram of the compressed air supply system to a two-phase nozzle;

[0024] Fig. 3 shows a fragment of the stand when a pipe is installed between the nozzle and the propeller-motor group (top view);

[0025] Fig. 4 shows the power supply and speed control system of the test group and the system for monitoring its condition.

[0026] The following elements are indicated by numbers on the figures:

[0027] 1 - tested propeller-motor group;

[0028] 2 - freezer;

[0029] 3- power supply system and speed control system for the tested propeller-motor group;

[0030] 4 - system for monitoring the condition of the tested propeller-motor group;

[0031] 5 - air temperature and humidity meters;

[0032] 6 - two-phase injector;

[0033] 7 - water supply system;

[0034] 8 - compressed air supply system;

[0035] 9 - compressor with receiver;

[0036] 10 - pipeline;

[0037] 11 - compressed air filter;

[0038] 12 - compressed air regulator;

[0039] 13 - compressed air dryer;

[0040] 14 - aftercooler;

[0041] 15 - pipe;

[0042] 16 - DC power supply;

[0043] 17 - electronic motor speed controller;

[0044] 18 - proportional-integral-differentiative (PID) controller;

[0045] z19 - strain gauge;

[0046] 20 - beam to which the tested propeller-motor group is attached.

[0047] Implementation of the invention

[0048] The test rig (Fig. 1) for testing the propeller-motor group (1) for icing contains a freezer (2), a power supply system and a system for controlling the speed of the propeller-motor group being tested (3), a system for monitoring the condition of the propeller-motor group being tested (4), air temperature and humidity meters (5) inside the freezer, a two-phase nozzle (6) spraying water onto the propeller-motor group being tested, and systems for supplying water (7) and compressed air (8) to the two-phase nozzle.

[0049] The water supply system (7) to the two-phase nozzle (6) may contain a tank with distilled or deionized water under pressure, a tap, a pipeline and a rotameter that sets the water flow through the two-phase nozzle (not shown in Fig. 1).

[0050] The compressed air supply system (8) to the two-phase nozzle (6) consists of a compressor with a receiver (9) (Fig. 2), a pipeline (10), a filter (11) and a pressure regulator (12) of compressed air, as well as an air dryer (13) installed between the filter (11) and the pressure regulator (12) of compressed air. The compressed air supply system may also contain an aftercooler (14) located in front of the filter (11), which allows removing some of the moisture from the compressed air using the filter (as a result of condensation in its porous element) and thereby reducing the load on the dryer. Depending on the investigated range of air temperatures during icing, the air dryer (13) can be of the refrigeration or adsorption type. The aftercooler (14) is made in the form of a radiator with passive or active cooling.

[0051] The movement and speed of the water-air flow are determined by the propeller of the test propeller-motor unit. A separate additional fan is not provided, allowing for a compact and energy-efficient setup. The distance between the plane of rotation of the test propeller-motor unit and the nearest wall of the freezer is at least one propeller diameter.

[0052] A two-phase nozzle can have either a flat spray pattern or a full cone shape, using nozzle nozzles. A flat spray pattern sprays water in a line onto a surface perpendicular to the spray axis, while a full cone spray pattern sprays water in a circle. Both patterns ensure uniform droplet coverage of the rotating propeller of the tested propeller-motor assembly.

[0053] A temperature sensor and a resistive heating element, powered through a proportional-integral-PC17RU2025 / 000185, can be glued to the body of the two-phase injector.

[0054] A differential (PID) controller (not shown in Fig. 1). Powering the heating element via a PID allows for automatic setting of the nozzle temperature and adjustment of the power output to the heating element as the freezer air temperature drops, thereby preventing freezing at very low temperatures.

[0055] In the freezing chamber (2), a pipe (15) (Fig. 3) can be installed between the tested propeller-motor group (1) and the two-phase nozzle (6) in such a way that the pipe axis coincides with the axis of rotation of the propeller-motor group propeller (Fig. 3). In this case, the diameter of the pipe (15) is comparable to or greater than the diameter of the propeller-motor group propeller (1). If the pipe diameter is comparable to the propeller diameter, or greater than the propeller diameter, then the coincidence of the pipe axis with the propeller rotation axis ensures uniform coverage of the propeller with droplets and, accordingly, its uniform icing.

[0056] The power supply and speed control system of the tested propeller-motor group (3 in Fig. 1), as shown in Fig. 4, consists of a DC power source (16) connected to an electronic speed controller (17), to which a pulse-width signal is supplied, setting the speed of rotation and coming, for example, from a microcontroller (not shown in Fig. 4). Also, the pulse-width signal can come from a PID controller (18), also built on a microcontroller.

[0057] The system for monitoring the condition of the tested propeller-motor group (4 in Fig. 1) may contain a strain gauge (19 in Fig. 4). The strain gauge is necessary in case of measuring the thrust of the propeller-motor group during the experiment or maintaining its constant value for simulating the hovering process of a rotary-wing aircraft. As a strain gauge (19) one can take a cantilever-type strain gauge, which, on one side, is attached to a fixed base, for example, to a fixed frame in a freezer (not shown in Figs. 1 and 4) or to the freezer itself, and on the other side - either directly to the propeller-motor group (Fig. 1) or to a beam (20 in Fig. 4), on which the propeller-motor group (1) is fixed. The beam is essentially a beam on which the propeller-motor group is fixed. The purpose of the beams is to separate the propeller groups in space to prevent collisions between the rotating propellers that create the necessary thrust for the quadcopter.The voltage from the bridge circuit of the strain gauge is connected to the analog-to-digital converter of the microcontroller (not shown in Fig. 4), which stores the measured values ​​in the computer memory or uses them for PID control of the engine speed (18 in Fig. 4).

[0058] Temperature and humidity meters (5 in Fig. 1) are mounted inside the freezer, for example, on a fixed frame (not shown in Fig. 1) or on the interior surface of the freezer, so that the spray from the two-phase nozzle does not fall on them, for example, next to or behind the nozzle. There may be at least two temperature and humidity meters: one for temperature measurements, the other for humidity, or they may be combined into a single device that periodically polls them, displays the readings on a display, and records them in internal memory for subsequent analysis.

[0059] The components of the rig and the tested propeller-motor unit are arranged within the freezing chamber by fastening them to each other in contact or to a fixed frame (not shown in Figs. 1, 3, 4). For example, the beam (20 in Fig. 4) of the propeller-motor unit (1) is in contact and connected to the strain gauge by, for example, a bolted connection. Similarly, the propeller-motor unit and the beam can be connected to each other, for example, by a screw connection.

[0060] The rig operates as follows. The required air temperature is set in the freezer chamber (2). The power supply and control system of the tested propeller-motor group (3) sets the required rotation speed or thrust, recorded by the condition monitoring system of the tested propeller-motor group (4). Compressed, dried air is first supplied to the two-phase nozzle (6), and then distilled or deionized water is supplied to the two-phase nozzle by the water supply system. The moment water is supplied to the two-phase nozzle is considered the beginning of the icing test. During the test, the air temperature and humidity in the freezer are recorded using air temperature and humidity meters (5), and the liquid flow rate through the two-phase nozzle is also recorded, set, for example, by a rotameter (not shown in Fig. 1).Based on measured air temperature and humidity, water flow through the two-phase nozzle (6), and the thrust of the tested propeller-motor unit, the water content of the air-water flow during testing is determined. The measured water content and temperature of the air-water flow determine the rate of ice formation on the propeller-motor unit blades.

[0061] Using a dehumidifier in the compressed air supply system to a two-phase nozzle removes moisture from the compressed air and prevents its condensation during air throttling through the nozzle. This eliminates errors in setting the water-air flow moisture content and the associated accelerated icing.

[0062] The formation of a water-air flow by rotating the propeller of the tested propeller-motor group and spraying water with a two-phase nozzle in the freezer chamber makes it possible to implement a compact and energy-efficient test rig.

[0063] Setting the distance between the propeller's plane of rotation and the nearest freezer wall to at least one propeller diameter eliminates the effect of a sharp increase in propeller thrust near the surface (ground effect [5]), which is uncharacteristic of free flight. The water content of the air-droplet mixture sucked in by the propeller is determined by the airflow velocity, which in turn is estimated through the propeller's thrust. Selecting this distance eliminates the influence of the ground effect and thereby accurately estimates the water content, which determines the rate of ice accumulation on the propeller blades, and further improves the accuracy of the test results.

[0064] The use of a pipe in a freezer installed between a two-phase nozzle and the tested propeller-motor group in such a way that the axis of the pipe coincides with the axis of rotation of the propeller-motor group propeller, and the equivalent diameter of the pipe is comparable to or greater than the diameter of the propeller-motor group propeller, makes it possible to eliminate the drift of the aerosol cloud and the change in the icing rate if the freezer is equipped with an air cooling system, and also to ensure uniform coverage of the propeller surface with supercooled droplets.

[0065] Installing the air temperature and humidity meters in the freezer compartment so that the spray from the two-phase nozzle does not fall on them eliminates errors in determining the air humidity and temperature in the chamber (one of the parameters that determine the rate of icing) due to the formation of ice on the sensors, which also further improves the accuracy of the test results.

[0066] Equipping the test propeller-motor unit's condition monitoring system with a strain gauge and the power supply and PID controller speed control system allows for maintaining constant propeller-motor unit thrust during testing. Constant propeller-motor unit thrust during icing allows for maintaining a constant water-air flow ratio (w) during testing due to the fact that the airflow velocity (u) generated by the propeller-motor unit is maintained constant (w = G / u, where G is the water flow rate through the nozzle).

[0067] The use of a pressurized water tank, a tap, a pipeline, and a rotameter in the water supply system for a two-phase nozzle allows for regulation and maintenance of a constant water flow through the nozzle and, accordingly, the water content during testing.

[0068] Installing an aftercooler between the compressor and the filter allows the compressed air, heated as a result of its compression by the compressor, to be cooled to room temperature, thereby further increasing the efficiency of moisture removal from the compressed air by the dryer and further improving the accuracy of the test results.

[0069] The use of a two-phase nozzle with a flat or full-cone spray torch allows for the rotating propeller of the propeller-motor group to be uniformly covered with water droplets, thereby bringing the test conditions closer to real ones.

[0070] Installing a heating element and temperature sensor on a two-phase nozzle prevents it from freezing during the experiment, preventing changes in water flow and the associated water content of the air-water mixture. Thus, the proposed technical solution allows for the creation of a compact, energy-efficient test rig with increased test accuracy.

[0071] Literature:

[0072] 1. Patent No. CN116176859A People's Republic of China, IPC G01M13 / 00, G01 N21 / 84. Propeller vibration icing monitoring system and monitoring method under simulated atmospheric environment: CN202310174851A: app. 02 / 23 / 2023: publ. 05 / 30 / 2023 And He Qiang; Li Anling; Yang Yunyun; Xiong Shenghua; Shi Binghong; Ren Shuaiang; Xu Zehua; Xu Yuan; Jia Yangyang. - 12 c.

[0073] 2. Modorskiy V. Ya., Kalyulin S. L., Sazhenkov N. A. Experimental setup for assessing the impact of icing and ice destruction on the vibration state of a model fan of a small-sized aircraft. Vestnik of the Moscow Aviation Institute. - 2023. - v. 30 - No. 4 - pp. 19-26.

[0074] 3. Küchemann D., Weber I. Aerodynamics of Aircraft Engines. Translation from English. Moscow, “Foreign Literature Publishing House”, 1956.

[0075] 4. Tenishev R.Kh. et al., Anti-icing systems of aircraft. Design principles and calculation methods, Moscow, "Mashinostroenie", 1967.

[0076] 5. Johnson W. Rotorcraft Aeromechanics, Cambridge University Press: Cambridge, UK, 2013.

Claims

CLAUSES OF THE INVENTION 1. A rig for testing a propeller-motor group for icing, characterized in that it contains a freezer chamber, a power supply system and a speed control system for the propeller-motor group being tested, a system for monitoring the condition of the propeller-motor group being tested, air temperature and humidity meters inside the freezer chamber, a two-phase nozzle spraying water onto the propeller-motor group being tested, systems for supplying water and compressed air to the two-phase nozzle, wherein the system for supplying compressed air to the two-phase nozzle, in addition to a compressor with a receiver, a pipeline, a filter and a compressed air pressure regulator, contains an air dryer.

2. The stand according to paragraph 1, characterized in that the distance between the plane of rotation of the propeller of the tested propeller-motor group and the nearest wall of the freezer chamber is not less than one of its diameters.

3. The stand according to paragraph 1, characterized in that the freezer chamber additionally contains a pipe installed between the nozzle and the tested propeller-motor group in such a way that the axis of the pipe coincides with the axis of rotation of the propeller-motor group propeller, and the equivalent diameter of the pipe is comparable to or greater than the diameter of the propeller-motor group propeller.

4. The stand according to paragraph 1, characterized in that the air temperature and humidity meters are installed in the freezer chamber in such a way that the spray torch of the two-phase nozzle does not fall on them.

5. The test rig according to item 1, characterized in that the system for monitoring the condition of the tested propeller-motor group contains a strain gauge, and the power supply and speed control system of the tested propeller-motor group contains a PID controller that maintains a constant thrust of the propeller-motor group during testing.

6. The stand according to item 1, characterized in that the system for supplying water to the two-phase nozzle contains a tank with pressurized water, a tap, a pipeline and a rotameter.

7. The stand according to item 1, characterized in that the system for supplying compressed air to the two-phase nozzle additionally contains a compressed air aftercooler installed between the compressor and the filter.

8. The stand according to item 1, characterized in that the two-phase nozzle has either a flat spray torch or a full cone shape.

9. The stand according to item 1, characterized in that a heating element and a temperature sensor are installed on the two-phase nozzle.

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