CN110763472A

CN110763472A - Engine test bed and test method thereof

Info

Publication number: CN110763472A
Application number: CN201911209835.7A
Authority: CN
Inventors: 李强; 王文彬; 康宏博
Original assignee: Beijing Aerospace Sanfa High Tech Co Ltd
Current assignee: Beijing Aerospace Sanfa High Tech Co Ltd
Priority date: 2019-12-02
Filing date: 2019-12-02
Publication date: 2020-02-07

Abstract

An engine test bed comprises an air inlet system, an engine thrust measuring rack, an exhaust pipeline, a silencing device and a simulation cabin; the engine thrust measuring rack is fixedly arranged in the simulation cabin, and the tested engine is arranged on the engine thrust measuring rack; the air inlet system is communicated with the tested engine, one end of the exhaust pipeline penetrates through the surface of the shell of the simulation cabin and is fixedly installed in the simulation cabin, and the other end of the exhaust pipeline is fixedly communicated with the silencing device. The air inlet system of the engine test bed has high adjusting speed, saves the adjusting time of the air inlet simulation of the engine of the test bed, reduces the test cost and avoids energy waste. Meanwhile, the engine thrust measuring rack realizes measurement of the engine thrust and has a simple structure. In addition, the silencing device reduces the using quantity of the silencing pieces on the premise of ensuring the silencing capacity, occupies small area, has wide application range and greatly reduces the cost.

Description

Engine test bed and test method thereof

Technical Field

The invention relates to the technical field of engine tests, in particular to an engine test bed and a test method thereof.

Background

The engine test and test technology is an important component of the solid propulsion technology, the aircraft engine needs to be subjected to a simulation test on the ground before test flight, a group of air inlet parameters including total air inlet pressure, air inlet flow rate, air inlet oxygen content, total air inlet temperature and oil supply quantity of the engine are called as air inlet state points during the engine test, and the performance and the parameters of the aircraft engine are recorded or the performance of the aircraft engine is checked after the set value and the stability are reached. With the gradual maturity of engines, the application of engines is gradually widened, on the basis, when the engine is used for engines of airplanes, particularly unmanned planes and engine ground tests, an engine air inlet system needs to simulate the air inlet state of the engine, the existing engine test bed technology has no mature technology for engine air inlet simulation, and meanwhile, an accurate theoretical judgment method is not available when the simulation state reaches a stable state, so that the test simulation effect is poor, the test period is long, the cost is high, and the resource waste condition is serious.

Meanwhile, the thrust measurement is an important parameter to be measured in engine tests and tests. To study engine thrust, numerous trial and error tests are required, which are not possible if all are put into flight tests. The main reasons are high flight test cost, long period, small information yield, risk and large manpower consumption. The engine ground test is to perform static test on the system according to specific conditions and environmental requirements on the ground to obtain various performance index information describing the system so as to solve the key problem in the engine thrust test process.

In addition, the noise sources polluting various workplaces and surrounding environments of the engine test bed mainly come from aerodynamic noise, and the noise sources only exist in the test bed when the engine test bed is tested, and the noise is generated to be more than 130dB (A) when high-pressure, high-speed and high-temperature compressed air and fuel gas flow in a metal or other enclosure structure or are exhausted to the atmosphere. Noise is unnecessary sound, the frequency of sound that can be heard by human ears is within 20HZ to 20000HZ, which is directly perceived by human beings, and noise outside this frequency is not perceived by human ears as a silent killer, and is also the object of noise control. At present, each country regulates noise to be controlled within different sound pressure levels according to different environments. According to the relevant regulations of the domestic environmental protection law, the noise sound pressure level of a newly built enterprise working for 8 hours every day is allowed to be 85dB (A), and the noise sound pressure level of the newly built enterprise working for 1 hour every day is allowed to be 94dB (A). For the engine test bed with acoustic power larger than 130dB (A), short action time and working places far away from towns and residential areas, the noise control aims to ensure that the noise of the working places of the test bed reaches the specified index and reduce the noise of the environment outside the test bed as far as possible.

For the method of silencing and reducing noise of the noise generated by the test bed, the prior art has not been provided with a mature and effective technical means, the applicant previously applied CN203910262U and proposed a silencer, which has a certain effect on silencing and reducing noise of the test bed, but the way of staggered arrangement of the thick components and the thin components of the silencer needs a larger floor area, on one hand, when the exhaust flow of the engine test bed is smaller, in order to ensure the silencing quality, a plurality of thick components and thin components (each layer of silencing component needs at least 2 thick components of the silencer and 2 thin components of the silencer and the other half thick components and half thin components of the silencer) still need to be established, resulting in a great increase in cost; on the other hand, when the floor area of the engine test bed, which allows the installation of the muffler device, is small and does not allow the thick sheet assembly and the thin sheet assembly of the muffler as described in this patent application to be provided for each layer in a staggered arrangement, the elimination of any one of the muffling sheets results in a reduction in the muffling ability.

Disclosure of Invention

The technical problem to be solved by the invention is as follows: the defects of the prior art are overcome, and the engine test bed and the test method thereof are provided.

The technical solution of the invention is as follows: an engine test bed comprises an air inlet system, an engine thrust measuring rack, an exhaust pipeline, a silencing device and a simulation cabin; the engine thrust measuring rack is fixedly arranged in the simulation cabin, and the tested engine is arranged on the engine thrust measuring rack; the air inlet system is communicated with the tested engine, one end of the exhaust pipeline penetrates through the surface of the shell of the simulation cabin and is fixedly installed in the simulation cabin, and the other end of the exhaust pipeline is fixedly communicated with the silencing device.

Compared with the prior art, the invention has the advantages that:

1. according to the engine test bed and the test method thereof, the air inlet system adopts the mode of firstly adjusting the total air inlet pressure and the oxygen content, then adjusting the total air inlet temperature, then finely adjusting the total air inlet pressure, supplying oil and igniting, the adjusting speed is high, the adjusting time of the engine air inlet simulation of the test bed is saved, the test cost is reduced, and the energy waste is avoided.

2. According to the engine test bed and the test method thereof, the air inlet system simulates the air inlet flow and the total air inlet pressure of the engine through the air inlet supply source of the engine, meanwhile, oxygen is supplemented for the air inlet of the engine through the oxygen supply source, the air inlet temperature of the engine is simulated through the temperature simulation unit, the real simulation of the air inlet of the engine is realized, and the simulation precision is high.

3. According to the engine test bed and the test method thereof, the air inlet system is provided with the alcohol supply source, alcohol is ignited by the igniter to generate heat, and the heat exchanges heat with the air inlet of the engine in the temperature simulation unit, so that the adjustment of the air inlet temperature of the engine is realized.

4. According to the engine test bed and the test method thereof, the air inlet system is provided with various valves, so that the flow and the pressure of related supply sources can be adjusted, and further the multi-state point simulation is realized.

5. According to the engine test bed and the test method thereof, the engine thrust measurement bench realizes measurement of the engine thrust and has a simple structure.

6. According to the engine test bed and the test method thereof, the engine thrust measuring rack skillfully hangs the movable rack on the fixed rack through the spring piece and is simple and easy to implement by assisting the force sensor to measure the thrust of the engine.

7. According to the engine test bed and the test method thereof, the engine thrust measuring rack is internally provided with the measuring section bracket to ensure that the measuring section for measuring the air inlet parameter of the tested engine is coaxial with the engine, so that the air inlet simulation precision of the engine is ensured, and the air inlet parameter measuring precision of the engine is improved.

8. According to the engine test bed and the test method thereof, the overall rigidity of the movable frame is higher in the engine thrust measurement rack, stress elements are reasonably distributed on the design in order to ensure the dynamic performance of the test frame, the principle of equal strength of the structure is adopted, the stress-free parts of materials are removed, and the like, so that the mass of the movable frame is reduced.

9. According to the engine test bed and the test method thereof, the horizontal base is arranged on the fixed frame in the engine thrust measuring rack, so that the bearing capacity of the whole fixed frame is improved.

10. According to the engine test bed and the test method thereof, the engine thrust measuring rack is provided with the locking state, so that when the engine is in an untested state or is installed before a test, the movable rack and the fixed rack are kept in a fixed state, the service life of the engine thrust measuring rack is prolonged, the situation that irreversible external force is applied to the spring piece or even the spring piece is damaged when the engine and related test pieces of the engine are installed in an own state (the locking state is not used) of the movable rack is avoided, and the precision of the engine thrust measuring rack is ensured.

11. According to the engine test bed and the test method thereof, the gantry engine mounting rack is adopted in the engine thrust measuring rack, the engine is suspended, the measurement precision of the engine thrust is improved, the positions of the front joint and the rear joint are adjustable, the application range of the engine mounting rack is greatly improved, and the problem that one engine is provided with one engine mounting rack in the prior art is solved.

12. In the engine thrust measuring bench, the standard force sensor is adopted to determine the error of the working force sensor, and the static calibration is carried out, so that a group of high-precision known simulated thrust is generated to determine the degree of the force measuring system.

13. According to the engine test stand and the test method thereof, the characteristic curve graphs of the standard force sensor and the working force sensor are drawn in the engine thrust measurement rack in a calibration mode, the force value output by the working force sensor accurately determines the true value of the force through the characteristic curve graphs, the calibration of the working force sensor in each test is avoided, the cost is low, and the efficiency is high.

13. The invention relates to an engine test bed and a test method thereof, wherein a silencing device creatively provides a thin and thick combined silencing sheet flat sheet, a thin silencing sheet and a thick silencing sheet are respectively arranged on the side of an airflow channel 2, the use number of the silencing sheets is reduced on the premise of ensuring the silencing capability (aiming at the prior art that each layer of silencing sheet assembly at least needs a thick sheet assembly of 2 silencers and a thin sheet assembly of 2 silencers and additionally adds a thick sheet assembly of a half silencer and a thin sheet assembly of a half silencer, each layer of silencing sheet assembly provided by the invention is equivalent to only needing a thick sheet assembly of 1 silencer and a thin sheet assembly of 1 silencer and additionally adds a thick sheet assembly of a half silencer and a thin sheet assembly of a half silencer), the occupied area is small (the invention is suitable for a large-flow test bed and is also suitable for a small-flow engine test bed), the application range is wide, meanwhile, the cost is greatly reduced.

14. According to the engine test bed and the test method thereof, the silencing device guides the gas entering the cylinder body of the variable-frequency diffuser through the cone-shaped variable-frequency diffuser guide cone, so that the gas entering the cylinder body of the variable-frequency diffuser is uniformly discharged from the plurality of variable-frequency diffuser air outlet holes, subsequent silencing is facilitated, and the silencing effect is improved.

15. According to the engine test bed and the test method thereof, the silencer is provided with the variable frequency diffuser, the variable frequency diffuser air outlet hole in the form of the through hole is formed in the surface of the variable frequency diffuser, the noise frequency is shifted to high frequency by air flow through the air outlet hole of the dry variable frequency diffuser, and the noise control difficulty is reduced by utilizing the principle that the high frequency is easier to be silenced than the low frequency.

16. According to the engine test bed and the test method thereof, the silencing device is provided with the flow guide sheet on the silencing sheet to guide the gas entering the gas flow channel, so that the gas flows uniformly, and the silencing effect is further improved.

Drawings

Fig. 1 is a schematic structural view of an engine test bed of the present invention.

Fig. 2 is a front view of the engine thrust measuring stand of the engine test bed of the present invention.

Fig. 3 is an enlarged view of a portion a in fig. 2.

Fig. 4 is an enlarged view of a portion B in fig. 2.

Fig. 5 is a top view of the engine thrust measuring rack structure of the engine test bed of the present invention.

Fig. 6 is an enlarged view of the portion C of fig. 5.

Fig. 7 is a schematic structural diagram of a measurement section bracket of an engine thrust measurement rack in the engine test bed of the present invention.

Fig. 8 is an enlarged view of a portion D in fig. 7.

Fig. 9 is an enlarged view of a portion E of fig. 7.

Fig. 10 is a front view of an engine mount of an engine thrust measuring stand according to the present invention.

Fig. 11 is a structural side view of an engine mount of an engine thrust measuring stand in the engine test bed of the present invention.

Fig. 12 is a schematic structural view of an engine mounting upper frame of an engine thrust measurement stand in the engine test bed of the present invention.

Fig. 13 is a schematic diagram illustrating the calibration of the force sensor of the engine thrust measuring stand in the engine test bed according to the present invention.

Fig. 14 is a partial configuration diagram of a temperature simulation unit of an intake system in the engine test bed of the present invention.

Fig. 15 is a schematic structural view of an exhaust pipe and a muffler in the engine test bed of the present invention.

Fig. 16 is a schematic structural view showing an internal structure of a muffler device of an engine test bed according to the present invention.

Fig. 17 is a schematic structural view of a 3-layer noise reduction sheet assembly in an embodiment of the noise reduction device in the engine test bed of the present invention.

Fig. 18 is a schematic structural view of a 1-layer noise damping sheet assembly of the noise damping device in the engine test bed of the present invention.

Fig. 19 is a schematic structural view of a half-thin sound-deadening sheet of the sound-deadening device in the engine test bed of the present invention.

Fig. 20 is a schematic structural view of a half-thickness silencing plate of the silencing device in the engine test bed of the present invention.

Fig. 21 is a schematic structural view of a thin and thick combined noise damping sheet of a noise damping device in an engine test bed according to the present invention.

Fig. 22 is a schematic structural view of a variable frequency diffuser in an engine test bed of the present invention, in one angular direction of a silencer of the silencer.

Fig. 23 is a schematic structural view of a variable frequency diffuser in another angular direction of a silencer of the silencer in the engine test bed of the present invention.

Fig. 24 is a schematic structural view of a variable frequency diffuser deflector cone in a variable frequency diffuser of a silencer in an engine test bed according to the present invention.

Detailed Description

In the description of the present invention, it is to be understood that the terms "central," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," "counterclockwise," "axial," "radial," "circumferential," and the like are used in the orientations and positional relationships indicated in the drawings for convenience in describing the invention and to simplify the description, and are not intended to indicate or imply that the referenced devices or elements must have a particular orientation, be constructed and operated in a particular orientation, and are therefore not to be considered limiting of the invention. Furthermore, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of the present invention, "a plurality" means two or more unless otherwise specified.

In the description of the present invention, it is to be noted that, unless otherwise explicitly specified or limited, the terms "mounted", "connected" and "abutted" are to be construed broadly, e.g., as being fixedly connected, detachably connected, or integrally connected; can be mechanically or electrically connected; they may be connected directly or indirectly through intervening media, or they may be interconnected between two elements. The specific meanings of the above terms in the present invention can be understood in specific cases to those skilled in the art.

The pressure, total pressure, static pressure, dynamic pressure, temperature, total temperature, static temperature and dynamic temperature related to the invention are the same as those of the prior application (application number: CN201811164303.1, the name of the invention is: an engine test bed) of the applicant, in addition, the air inlet system of the engine test bed related to the invention is provided with a temperature sensor and a pressure sensor in the inlet and the outlet of a first medium channel, the inlet and the outlet of a second medium channel, the inlet and the outlet of a measuring section and the measuring section in a second medium channel, and the temperature sensor and the pressure sensor are both arranged facing the airflow direction and are used for measuring the total pressure and the total temperature of the section of the sensor.

A test bed of an engine, such as an aerospace engine like a turbofan engine and a solid-impact engine, is particularly suitable for a test bed of a multi-state point simulation test like ground starting of the engine, wherein in the multi-state points of the engine, parameters of each state point comprise total intake pressure, intake air flow, intake oxygen component, total intake temperature and engine oil supply quantity. The engine test bed comprises an air inlet system, an engine thrust measuring bench, an exhaust pipeline 700, a silencing device 800 and a simulation cabin 900; the shape of the simulation cabin 900 is not limited, and may be a cuboid, an ellipsoid or the like; the engine thrust measuring rack is fixedly arranged in the simulation cabin 900, and the tested engine 1 is arranged on the engine thrust measuring rack; the intake system is communicated with the tested engine 1, one end of the exhaust pipeline 700 penetrates through the shell surface of the simulation cabin 900 and is fixedly installed inside the simulation cabin 900, and the other end of the exhaust pipeline 700 is fixedly communicated with the silencer 800.

Preferably, the other end of the exhaust duct 700 is fixedly communicated with a variable-frequency diffuser 820 of the silencer 800.

The intake system includes a supply source, a temperature simulation unit 60.

The supply sources include a fuel supply source 10, an oxygen supply source 20, an engine intake air supply source 30, and an alcohol supply source 40

The temperature simulation unit comprises a pipe body 61 and a shell 62, wherein the pipe body 61 is positioned inside the shell 62, a first medium channel is formed in the pipe body 61, and a second medium channel is formed in a space between the outer wall of the pipe body 61 and the inner wall of the shell 62; when the temperature simulation unit 60 works, a first medium circulates in the first medium channel, a second medium circulates in the second medium channel, the temperature of the first medium is higher than that of the second medium, the first medium and the second medium realize heat exchange through the pipe wall of the pipe body 61, and the outlet of the measurement section 401 is fixedly communicated with the air suction port of the tested engine 1. The specific structure and the specific connection mode of the temperature simulation unit 60 and the measurement section 401 are described in the prior application of the applicant (application number: CN201811164305.0, name of the invention: an engine test bed air intake system or application number: CN201811164303.1, name of the invention: an engine test bed).

The fuel oil supply source 10 is communicated with the tested engine 1 through a pipeline, the oxygen supply source 20 and the engine air inlet supply source 30 are respectively communicated with an inlet of a second medium channel through pipelines, an outlet of the second medium channel is communicated with an inlet of a measuring section 401 through a pipeline, and an outlet of the measuring section 401 is fixedly communicated with an air suction port of the tested engine 1 to provide simulated engine air inlet flow, total air inlet pressure and oxygen content for the tested engine 1; the alcohol supply source 40 is communicated with the inlet of the first medium channel through a pipeline after passing through the igniter, the outlet of the first medium channel is communicated with the outside, the igniter ignites alcohol to burn to generate heat, and the heat is exchanged with the second medium in the second medium channel in the temperature simulation unit 60 to adjust the temperature of the second medium in the second medium channel, so that the intake temperature simulation of the engine is realized.

An engine fuel supply flow regulating valve 51 is arranged on a pipeline for communicating the fuel supply source 10 with the tested engine 1, an oxygen supply flow regulating valve 53 is arranged on a pipeline for communicating the oxygen supply source 20 with the inlet of the second medium channel, an engine intake air supply pressure regulating valve 55 is arranged on a pipeline for communicating the engine intake air supply source 30 with the inlet of the second medium channel, and an alcohol supply flow regulating valve 56 is arranged on a pipeline for communicating the alcohol supply source 40 with the inlet of the first medium channel so as to realize parameter regulation of each supply source and meet the simulation of multi-state points.

Preferably, the intake system includes an engine fuel supply cutoff valve 52, an oxygen supply cutoff valve 54, and an alcohol supply cutoff valve 57, the engine fuel supply cutoff valve 52 being provided on a pipeline that communicates the fuel supply source 10 with the engine under test 1; the oxygen supply shutoff valve 54 is provided on a line that communicates the oxygen supply source 20 with the inlet of the second medium passage; the alcohol supply shut-off valve 57 is provided on a pipe line that communicates the alcohol supply source 40 with the inlet of the first medium passage. During the use of the intake system, the engine fuel supply shutoff valve 52 is opened before the engine fuel supply flow rate regulating valve 51 is opened, the oxygen supply shutoff valve 54 is opened before the oxygen supply flow rate regulating valve 53 is opened, and the alcohol supply shutoff valve 57 is opened before the alcohol supply flow rate regulating valve 56 is opened; the engine fuel supply shutoff valve 52 is closed after the engine fuel supply flow rate regulating valve 51 is closed, the oxygen supply shutoff valve 54 is closed after the oxygen supply flow rate regulating valve 53 is closed, and the alcohol supply shutoff valve 57 is closed after the alcohol supply flow rate regulating valve 56 is closed, so that the safety of the intake system in a non-experimental state is ensured.

The engine thrust measuring rack comprises a fixed rack 100, a movable rack 200 and a loading measuring device; the loading measuring device comprises a spring piece, a loading mechanism 330 and a working force sensor 350; the movable frame 200 is suspended on the fixed frame 100 through the spring plate, the loading mechanism 330 is fixedly mounted on the fixed frame 100, and two ends of the working force sensor 350 are respectively connected with the fixed frame 100 and the movable frame 200.

The fixed frame comprises a base 110, a front mounting seat 120, a loading mechanism mounting seat 130, a first fixed frame spring piece mounting seat 140, a fixed frame working force sensor mounting seat 150, a rear mounting seat 160 and a second fixed frame spring piece mounting seat 170; the base 110 is of a cuboid structure, the front mounting seat 120 and the rear mounting seat 160 are respectively and fixedly mounted at the front end and the rear end of the base 110 along the length direction of the base 110, the rear mounting seat 160 comprises a transverse plate and a vertical plate, and the transverse plate and the vertical plate form an L shape; the loading mechanism mounting seat 130 is fixedly mounted on the front mounting seat 120, the first fixed frame spring leaf mounting seat 140 includes a first right fixed frame spring leaf mounting seat 141 and a first left fixed frame spring leaf mounting seat 142, and the first right fixed frame spring leaf mounting seat 141 and the first left fixed frame spring leaf mounting seat 142 are fixedly mounted at the front end of the base 110 and are respectively located on two sides of the front mounting seat 120; the fixed frame working force sensor mounting seat 150 is fixedly mounted on the base 110 and is positioned on a central line along the length direction of the base 110; the second fixed frame spring piece mounting seat 170 includes a second right fixed frame spring piece mounting seat 171 and a second left fixed frame spring piece mounting seat 172, and the second right fixed frame spring piece mounting seat 171 and the second left fixed frame spring piece mounting seat 172 are fixedly mounted at the rear end of the base 110 and respectively located at two sides of the rear mounting seat 160.

The movable frame 200 comprises a movable frame body 210, a first movable frame spring piece mounting seat 220, a movable frame working force sensor mounting seat 230, a second movable frame spring piece mounting seat 240 and a movable frame standard force sensor mounting seat 250, wherein the movable frame body 210 comprises a right movable frame body 211, a left movable frame body 212 and a movable frame connecting plate 260, the right movable frame body 211 and the left movable frame body 212 are identical in structure, both of which are cuboid structures and are parallel to the base 110, the central line of the right movable frame body 211 and the left movable frame body 212 in the length direction is parallel to the central line of the base 110 in the length direction, the right movable frame body 211 and the left movable frame body 212 are symmetrically arranged relative to the central line of the base 110 in the length direction, the number of the movable frame connecting plates 260 is multiple, and the right movable frame body 211 and the left movable frame body 212 are fixedly connected by the plurality of the movable frame connecting plates 260; along the length direction of the movable frame body 210, a movable frame standard force sensor mounting seat 250 is fixedly mounted on the bottom surface of the front end of the movable frame body 210; the first moving frame spring piece mounting seat 220 comprises a first right moving frame spring piece mounting seat and a first left moving frame spring piece mounting seat, and the first right moving frame spring piece mounting seat and the first left moving frame spring piece mounting seat are respectively fixedly mounted on the bottom surfaces of the front ends of the right moving frame body 211 and the left moving frame body 212 and are respectively positioned on two sides of the moving frame standard force sensor mounting seat 250; the movable frame working force sensor mounting base 230 is fixedly mounted at the bottom of one movable frame connecting plate 260 of the movable frame body 210 and is located on a central line along the length direction of the movable frame body 210; the second moving frame spring piece mounting seat 240 comprises a second right moving frame spring piece mounting seat and a second left moving frame spring piece mounting seat, and the second right moving frame spring piece mounting seat and the second left moving frame spring piece mounting seat are fixedly mounted on the bottom surfaces of the rear ends of the right moving frame body 211 and the left moving frame body 212 respectively.

The loading measuring device comprises a first spring plate 310, a second spring plate 320, a loading mechanism 330, a standard force sensor 340 and a working force sensor 350; the first spring piece 310 comprises a first right spring piece 311 and a first left spring piece 312, two ends of the first right spring piece 311 are respectively and fixedly connected with a first right fixed frame spring piece mounting seat 141 and a first right movable frame spring piece mounting seat, and two ends of the first left spring piece 312 are respectively and fixedly connected with a first left fixed frame spring piece mounting seat 142 and a first left movable frame spring piece mounting seat; the second spring piece 320 comprises a second right spring piece 321 and a second left spring piece 322, two ends of the second right spring piece 321 are fixedly connected with the second right fixed frame spring piece mounting seat 171 and the second right movable frame spring piece mounting seat respectively, and two ends of the second left spring piece 322 are fixedly connected with the second left fixed frame spring piece mounting seat 172 and the second left movable frame spring piece mounting seat respectively; the loading mechanism 330 is fixedly mounted on a transverse plate of the front mounting seat 120, the standard force sensor 340 is fixedly mounted on a baffle plate at the front end of the movable frame body 210, and the loading mechanism 330 and the standard force sensor 340 are coaxially arranged and are parallel to the central line of the base 110 along the length direction; two ends of the working force sensor 350 are respectively and fixedly connected with the fixed frame working force sensor mounting seat 150 and the movable frame working force sensor mounting seat 230, and the working force sensor 350, the loading mechanism 330 and the standard force sensor 340 are coaxially arranged; the loading mechanism 330 comprises a servo motor, a motor power supply, a hydraulic loading device and a calibration oil cylinder, wherein the motor power supply is electrically connected with the servo motor, the servo motor is sequentially connected with the hydraulic loading device and the calibration oil cylinder, and a piston of the calibration oil cylinder is connected with a standard force sensor.

The engine thrust measuring rack comprises a measuring section bracket for supporting a measuring section, the measuring section bracket comprises a first measuring section bracket 410 and a second measuring section bracket 420 which are coaxially arranged, and the first measuring section bracket 410 and the second measuring section bracket 420 have the same structure and are both fixedly arranged on the top surface of the movable rack body 210; the measuring section bracket comprises a measuring section bracket 411, a measuring section bracket lower ring 412, a measuring section bracket upper ring 413, a measuring section bracket positioning mechanism 414 and a locking device 415; the bottom surface of the measurement section bracket 411 is fixedly connected with the top surface of the movable frame body 210, the measurement section bracket lower ring 412 and the measurement section bracket upper ring 413 are both of a semicircular structure, and the measurement section bracket lower ring 412 and the measurement section bracket upper ring 413 are connected to form a circle; the measuring section bracket lower ring 412 and the measuring section bracket 411 are integrally formed; the number of the measurement section bracket positioning mechanisms 414 is 3, the structures of the measurement section bracket positioning mechanisms are the same, and the measurement sections are used for positioning and measuring intake parameters of the tested engine 1; the 3 measuring section bracket positioning mechanisms 414 are uniformly distributed along the radial direction of a circle formed by connecting the measuring section bracket lower ring 412 and the measuring section bracket upper ring 413, wherein one measuring section bracket positioning mechanism 414 is arranged at the top of the measuring section bracket upper ring 413, and the rest 2 measuring section bracket positioning mechanisms 414 are arranged on the measuring section bracket lower ring 412; the measuring section bracket positioning mechanism 414 comprises a positioning mechanism nut 4141, a positioning mechanism locking nut 4142 and a positioning mechanism screw 4143, the positioning mechanism screw 4143 passes through the measuring section bracket lower ring 412 or the measuring section bracket upper ring 413, the positioning mechanism locking nut 4142 is sleeved on the positioning mechanism screw 4143, is arranged on the outer side of the measuring section bracket lower ring 412 or the measuring section bracket upper ring 413 and is abutted against the measuring section bracket lower ring 412 or the measuring section bracket upper ring 413 and is used for locking the positioning mechanism screw 4143, and the positioning mechanism nut 4141 is sleeved on the positioning mechanism screw 4143 and is abutted against the positioning mechanism locking nut 4142; the number of the locking devices 415 is 2, and the structures of the locking devices are the same, and the locking devices 415 are used for fixedly connecting the lower ring 412 of the measurement section bracket and the upper ring 413 of the measurement section bracket, 2 locking devices 415 are arranged at the connecting ends of the lower ring 412 of the measurement section bracket and the upper ring 413 of the measurement section bracket, the locking device 415 includes an upper locking plate 4151, a lower locking plate 4152, a locking bolt 4153 and a locking nut 4154, the upper locking plate 4151 is fixedly attached to the front end surface of the upper ring 413 of the measurement section bracket, the lower surface of the upper locking plate 4151 coincides with the lower surface of the upper ring 413 of the measurement section bracket, the lower locking plate 4152 is fixedly attached to the front end surface of the measuring section bracket lower ring 412, the upper surface of the lower lock plate 4152 coincides with the upper surface of the measuring section bracket lower ring 412, the locking bolt 4153 passes through the lower and upper locking plates 4152 and 4151 in sequence, the lock nut 4154 is engaged with the lock bolt 4153 and abuts against the upper lock plate 4151.

The engine thrust measuring rack comprises a locking device, the locking device comprises a fastening screw rod 510, a fastening baffle 520 and a fastening nut 530, the fastening screw rod 510 sequentially penetrates through a rear end baffle of the movable rack body 210, the fastening baffle 520, a vertical plate and a fastening nut 530 of the rear mounting seat 160, the fastening nut 530 is matched with the fastening screw rod 510, and the fastening baffle 520 and the fastening nut 530 are both abutted to the vertical plate of the rear mounting seat 160.

The engine thrust measuring rack comprises an engine mounting rack 600, wherein the engine mounting rack 600 comprises an engine mounting top rack 610, a left upright column 620 and a right upright column 630 which are identical in structure, a front joint 640, a rear joint 650 and a lifting lug 660; the bottom surfaces of the left upright post 620 and the right upright post 630 are detachably connected with the movable frame 200; the engine mounting top frame 610 is fixedly connected with the top surfaces of the left upright column 620 and the right upright column 630 to form a gantry type, the front joint 640 and the rear joint 650 are detachably mounted on the engine mounting top frame 610, and the lifting lug 660 is fixedly connected with the engine mounting top frame 610; the engine mounting top frame 610 comprises a front beam 611, a rear beam 612 and a longitudinal beam 613, wherein the front beam 611 and the rear beam 612 are arranged in parallel and are fixedly connected with the longitudinal beam 613, the rear beam 612 is fixedly connected with one end of the longitudinal beam 613, and the front beam 611, the rear beam 612 and the longitudinal beam 613 form a shape like the Chinese character 'tu'; the longitudinal beam 613 is provided with a mounting hole 614 for mounting a front joint 640 and a rear joint 650; the left upright post 620 comprises a front post 621, a rear post 622 and upright post connecting rods 623, wherein the front post 621 and the rear post 622 are arranged in parallel and are fixedly connected through the upright post connecting rods 623.

The engine thrust measurement rack comprises a force sensor calibration device, and the force sensor calibration device comprises an industrial personal computer, a display, a standard force sensor data acquisition device and a working force sensor data acquisition device; the industrial personal computer is respectively electrically connected with the display and the servo motor, the standard force sensor data acquisition device is respectively electrically connected with the standard force sensor and the industrial personal computer, and the working force sensor data acquisition device is respectively electrically connected with the working force sensor and the industrial personal computer.

The silencer 800 comprises a tower body 810, a variable-frequency diffuser 820 and a silencer assembly 830; a top cover 811 is arranged at the top end of the tower body 810, and a variable frequency diffuser mounting hole 812 for mounting the variable frequency diffuser 820 is formed in one side surface of the tower body 810; the variable-frequency diffuser 820 penetrates through the variable-frequency diffuser mounting hole 812 and then is horizontally and fixedly mounted in the tower body 810; the noise reduction plate assembly 830 is fixedly installed in the tower body 810, and preferably, the tower body is of a reinforced concrete structure.

The variable-frequency diffuser 820 comprises a variable-frequency diffuser cylinder 821 and a variable-frequency diffuser guide cone 823, wherein the variable-frequency diffuser cylinder 821 is a hollow circular cylinder, a plurality of variable-frequency diffuser air outlet holes 822 for discharging gas are formed in the surface of the cylinder, and the plurality of variable-frequency diffuser air outlet holes 822 are through holes penetrating through the circular cylinder; the variable frequency diffuser guide cone 823 is cone-shaped, the conical surface of the variable frequency diffuser guide cone 823 is arranged inside the circular cylinder, the diameter of the excircle at the bottom of the variable frequency diffuser guide cone 823 is the same as the inner diameter of the circular cylinder, the excircle at the bottom of the variable frequency diffuser guide cone 823 is fixedly connected with one end face of the circular cylinder, one end of the variable frequency diffuser cylinder 821 is closed, gas discharged from an engine test bench enters from the end face of one open end of the variable frequency diffuser cylinder 821, is guided by the variable frequency diffuser guide cone 823 and is discharged from a plurality of variable frequency diffuser gas outlet holes 822, and the gas entering the variable frequency diffuser cylinder 821 is guided by the variable frequency diffuser guide cone 823, so that the gas entering the variable frequency diffuser cylinder 821 is uniformly discharged from the plurality of variable frequency diffuser gas outlet holes 822 for subsequent silencing, the effectiveness of the sound attenuation is improved.

The silencing sheet assembly 830 comprises a lower layer silencing sheet assembly 8301, a middle layer silencing sheet assembly 8302 and an upper layer silencing sheet assembly 8303 which are arranged from bottom to top in sequence; each layer of silencing plate component comprises semi-thin silencing plates 831, semi-thick silencing plates 832 and thin and thick combined silencing plates 833 which are arranged at intervals, in each layer of silencing plate component, the semi-thin silencing plates 831 and the semi-thick silencing plates 832 are arranged at two ends and are fixedly connected with the front end face and the rear end face of the tower body 810, a plurality of thin and thick combined silencing plates 833 are arranged between the semi-thin silencing plates 831 and the semi-thick silencing plates 832 at intervals, and the adjacently arranged silencing plates form an air flow channel; the method of mounting each layer of sound attenuation panel assembly and the method of attachment to the tower are known in the art, in a manner substantially in accordance with the applicant's prior application (CN 201420057351.1).

On the same end side, the types of the silencing sheets of the adjacent 2 layers are different, so that the airflow channels formed by the adjacent silencing sheet assemblies are staggered, and the silencing capability of the silencing device is further improved, in a preferred embodiment of the application, in the lower layer silencing sheet assembly 8301 along the front-back direction of the silencing tower, the arrangement modes of the silencing sheets are half-thin silencing sheets 831, thin-thick combined silencing sheets 833 and half-thick silencing sheets 832, wherein the thick silencing sheet parts in the thin-thick combined silencing sheets 833 all face the half-thin silencing sheets 831; in the middle-layer silencing sheet assembly 8302, the arrangement modes of silencing sheets are a half-thick silencing sheet 832, a thin-thick combined silencing sheet 833 and a half-thin silencing sheet 831, wherein the thick silencing sheets in the thin-thick combined silencing sheet 833 face the half-thin silencing sheet 831; in the upper layer noise damping sheet assembly 8303, the noise damping sheets are arranged in a manner of a half-thin noise damping sheet 831, a thin-thick combined noise damping sheet 833 and a half-thick noise damping sheet 832, wherein the thick noise damping sheet portions in the thin-thick combined noise damping sheet 833 face the half-thin noise damping sheet 831.

The semi-thin silencing sheet 831 comprises a semi-thin silencing sheet flat sheet 8311 and 2 semi-thin silencing sheet flow guiding conical sheets 8312, the 2 semi-thin silencing sheet flow guiding conical sheets 8312 are fixedly connected with two ends of the semi-thin silencing sheet flat sheet 8311, and preferably, the 2 semi-thin silencing sheet flow guiding conical sheets 8312 and the semi-thin silencing sheet flat sheet 8311 are integrally formed; the surfaces of the semi-thin silencing sheet flat sheet 8311 and the semi-thin silencing sheet flow guiding conical sheet 8312 are both provided with a plurality of silencing sheet micropores 834, the plurality of silencing sheet micropores 834 are through holes penetrating through the surfaces of the semi-thin silencing sheet flat sheet 8311 and the semi-thin silencing sheet flow guiding conical sheet 8312, the structure of the semi-thin silencing sheet 831 is the prior art, the semi-thin silencing sheet is the semi-sheet structure of a sheet assembly in the prior application (application number: CN201420056663.0, invention name: sheet assembly for a silencer) of the applicant, and the semi-thin silencing sheet flow guiding conical sheet 8312 is arranged to realize gas flow guiding of an entering gas flow channel, so that gas flows uniformly, and the silencing effect is further improved.

The half-thick silencing sheet 832 comprises a half-thick silencing sheet flat sheet 8321 and 2 half-thick silencing sheet flow guiding conical sheets 8322, the 2 half-thick silencing sheet flow guiding conical sheets 8322 are fixedly connected with two ends of the half-thick silencing sheet flat sheet 8321, and preferably, the 2 half-thick silencing sheet flow guiding conical sheets 8322 and the half-thick silencing sheet flat sheet 8321 are integrally formed; the surfaces of the half-thick silencing plate flat sheet 8321 and the half-thick silencing plate flow guiding conical sheet 8322 are respectively provided with a plurality of silencing plate micro holes 834, and the plurality of silencing plate micro holes 834 are through holes penetrating through the surfaces of the half-thick silencing plate flat sheet 8321 and the half-thick silencing plate flow guiding conical sheet 8322; among them, the structure of the half-thick noise-canceling plate 832 is the prior art, which is the half-plate structure of the thin plate assembly in the prior application (application number: CN201420056662.6, title: thick plate assembly for muffler) of the applicant; the flow guide of the gas entering the gas flow channel is realized by arranging the half-thick silencing sheet flow guide conical sheet 8322, so that the gas flows uniformly, and the silencing effect is further improved.

The thin and thick combined silencing plate 833 is a combined plate formed by fixedly connecting and combining the horizontal surfaces of the semi-thin silencing plate 831 and the semi-thick silencing plate 832, in the combined thin and thick combined silencing plate 833, a thin and thick combined silencing plate flat plate 8331 forming the thin and thick combined silencing plate 833 is arranged in parallel by a semi-thin silencing plate flat plate 8311 and a semi-thick silencing plate flat plate 8321, and 2 thin and thick combined silencing plate flow guide conical plates 8332 forming the thin and thick combined silencing plate 833 are formed by the 2 semi-thin silencing plate flow guide conical plates 8312 and the 2 semi-thick silencing plate flow guide conical plates 8322; the flow guiding of the gas entering the gas flow channel is realized by arranging the thin and thick combined silencing piece flow guiding conical piece 8332, so that the gas flows uniformly, and the silencing effect is further improved.

The thickness of the semi-thin silencing sheet 831 is L1, the thickness of the semi-thick silencing sheet 832 is L2, and the thickness of the thin and thick combined silencing sheet 833 is L3, wherein L1 is more than L2 and less than L3, and L3 is equal to L1+ L2.

Preferably, the diameter of the sound damping sheet micro-holes 834 is 0.6mm-1mm, and more preferably, the diameter of the sound damping sheet micro-holes 834 is 0.8 mm.

Preferably, the diameter of the outlet 822 of the frequency diffuser is 40mm-80mm, and further preferably, the diameter of the outlet 822 of the frequency diffuser is 60mm,

preferably, the horizontal cross section in the tower body 810 is a square channel, and the wall thickness of the tower body 810 is 0.5m, and further preferably, the horizontal cross section in the tower body 810 is a square channel.

Preferably, the thickness L1 of the half-thin noise-damping sheet 831 is 80mm to 85mm, and more preferably, the thickness L1 of the half-thin noise-damping sheet 831 is 82 mm.

Preferably, the thickness L2 of the half-thickness noise-canceling plate 832 is 195mm to 205mm, and more preferably, the thickness L2 of the half-thickness noise-canceling plate 832 is 200 mm.

When the engine test bed is used for testing a tested engine, the method comprises the following steps:

s100), installing the tested engine 1 and measuring section

S110), sequentially enabling a measuring section for measuring engine air inlet parameters to pass through the first measuring section bracket 410 and the second measuring section bracket 420, and placing the measuring section in the first measuring section bracket 410 and the second measuring section bracket 420;

s120), mounting the front joint 640 and the rear joint 650 to the longitudinal beam 613 according to the suspension position of the engine 1 under test;

s130), mounting the engine mounting frame 600 on the movable frame body 210, and then mounting the tested engine 1 on the front joint 640 and the rear joint 650;

s140) adjusting the measuring section, connecting one end of the measuring section with the air inlet of the tested engine 1, adjusting a positioning mechanism screw 4143 in the measuring section bracket positioning mechanism 414, enabling the measuring section and the engine air inlet to be coaxial, and then sequentially rotating a positioning mechanism locking nut 4142 and a positioning mechanism nut 4141 in the measuring section bracket positioning mechanism 414.

S200), disassembling and locking device

The fastening nut 530 is loosened, the fastening screw 510 is pulled out from the vertical plate of the rear mounting seat 160, the fastening baffle 520 and the baffle at the rear end of the movable frame body 210 in sequence, and then the fastening baffle 520 is taken out.

S300), determining the error of the working force sensor

S310), the industrial personal computer controls the servo motor to start to drive the hydraulic loading device to work, the hydraulic loading device drives the calibration oil cylinder to work, a piston of the calibration oil cylinder drives the standard force sensor 340 to displace so as to drive the movable frame body 210 to displace, and force is applied to the working force sensor 350 in the displacement process of the movable frame body 210;

s320), the hydraulic loading device drives the calibration oil cylinder to work, and the loading force is unloaded to a zero value after the loading force is continuously applied to the standard force sensor 340 to a preset value; the standard force sensor data acquisition device and the working force sensor data acquisition device respectively acquire force values output by the standard force sensor 340 and the working force sensor 350 in the loading force applying and unloading processes and feed back the force values to the industrial personal computer, and the display displays the force values output by the standard force sensor 340 and the working force sensor 350 in the loading force applying and unloading processes, which are acquired by the standard force sensor data acquisition device and the working force sensor data acquisition device;

s330), drawing characteristic curve graphs of the standard force sensor 340 and the working force sensor 350 according to force values output by the standard force sensor 340 and the working force sensor 350 in the process of applying loading force and unloading loading force, wherein the force values are displayed by a display and acquired by the standard force sensor data acquisition device and the working force sensor data acquisition device; under the same loading force, the difference between the force value output by the working force sensor 350 acquired by the working force sensor data acquisition device and the force value output by the standard force sensor 340 acquired by the standard force sensor data acquisition device is the working force sensor error.

S400), simulating engine intake parameters (the specific simulation method is referred to the applicant prior application: application No.: CN201811164305.0, inventive name: an engine test bed air induction system or application number: CN201811164305.0, inventive name: an engine test bed air induction system or application number: CN201811164303.1, inventive name: an engine test bed).

S410), adjusting an engine intake air supply pressure adjusting valve and an oxygen supply flow adjusting valve according to the intake air total pressure and the oxygen content of the first simulation state point, so that the total pressure and the oxygen content of the second medium passing through the supersonic expansion section outlet of the measuring section are the same as the intake air total pressure and the oxygen content of the engine of the first simulation state point.

S420), adjusting an alcohol supply flow rate adjusting valve according to the total intake temperature of the first simulation state point, starting an igniter, igniting alcohol to combust the alcohol, exchanging heat between the combusted alcohol and a second medium in a first medium channel and a second medium in a second medium channel, and enabling the total temperature of the second medium passing through an outlet of the supersonic expansion section of the measuring section to be the same as the total intake temperature of the engine in the first simulation state point.

S430), adjusting an engine intake air supply pressure adjusting valve according to the intake total pressure of the first simulation state point, so that the total pressure of the second medium passing through the supersonic expansion section outlet of the measuring section is the same as the intake total pressure of the engine at the first simulation state point.

S440), gas exhausted from the exhaust pipeline 700 enters from the end face of the open end of the variable-frequency diffuser cylinder 821, is guided by a variable-frequency diffuser guide cone 823, and is exhausted from a plurality of variable-frequency diffuser air outlet holes 822, wherein the noise frequency of the gas is shifted to high frequency by the dry variable-frequency diffuser air outlet holes 822, and the noise control difficulty is reduced by utilizing the principle that the high frequency is easier to eliminate noise than the low frequency; the gas discharged from the outlet 822 of the variable frequency diffuser is discharged from the outlet at the top of the tower body 810 after being silenced and denoised by the staggered gas flow channel formed by 3 layers of silencer component assemblies.

S500), simulating test of first state point and measuring thrust of tested engine under the state point

And adjusting the engine fuel supply flow regulating valve according to the fuel demand of the first simulation state point of the engine, so that the fuel supplied by the fuel supply source is the same as the fuel demand of the first simulation state point of the engine, igniting the engine, performing an air intake simulation test of the first simulation state point, and displaying the force value output by the working force sensor 350, which is acquired by the working force sensor data acquisition device, by the display.

S600), simulation test of the Nth state point and measurement of thrust of the tested engine under the state point

Respectively adjusting an oxygen supply flow regulating valve, an engine air inlet supply pressure regulating valve, an alcohol supply flow regulating valve and an engine fuel supply flow regulating valve, so that the total pressure, the total temperature and the oxygen content of a second medium at the outlet of the supersonic expansion section of the measuring section are the same as the total intake pressure, the total temperature and the oxygen content of the engine at the Nth simulation state point, and the fuel supplied by a fuel supply source is the same as the fuel demand of the engine at the Nth simulation state point; wherein N is more than or equal to 2; starting an N state point air inlet simulation test of the engine to the state point air inlet simulation test and measuring the thrust measurement of the tested engine at the state point according to the method of the step S500.

S800), closing the air inlet system of the test bed

The engine is shut down and the engine fuel supply flow control valve, oxygen supply flow control valve, engine intake air supply pressure control valve and alcohol supply flow control valve are closed.

In the description herein, references to the description of the term "one embodiment," "some embodiments," "an illustrative embodiment," "an example," "a specific example," or "some examples" or the like mean that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the invention. In this specification, the schematic representations of the terms used above do not necessarily refer to the same embodiment or example. Furthermore, the particular features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.

While embodiments of the invention have been shown and described, it will be understood by those of ordinary skill in the art that: various changes, modifications, substitutions and alterations can be made to the embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the claims and their equivalents.

Claims

1. An engine test bed is characterized by comprising an air inlet system, an engine thrust measuring rack, an exhaust pipeline, a silencing device and a simulation cabin; the engine thrust measuring rack is fixedly arranged in the simulation cabin, and the tested engine is arranged on the engine thrust measuring rack; the air inlet system is communicated with the tested engine, one end of the exhaust pipeline penetrates through the surface of the shell of the simulation cabin and is fixedly installed in the simulation cabin, and the other end of the exhaust pipeline is fixedly communicated with the silencer.

2. The engine test stand of claim 1, wherein: the air inlet system comprises a supply source, a temperature simulation unit and a measurement section; the supply sources include a fuel supply source, an oxygen supply source, an engine intake air supply source, and an alcohol supply source.

3. The engine test stand of claim 1, wherein: the engine thrust measuring rack comprises a fixed rack, a movable rack and a loading measuring device; the loading measuring device comprises a spring piece, a loading mechanism and a working force sensor; the movable frame is hung on the fixed frame through the spring piece, the loading mechanism is fixedly installed on the fixed frame, and two ends of the working force sensor are respectively connected with the fixed frame and the movable frame.

4. The engine test stand of claim 3, wherein: the movable frame comprises a movable frame body, a first movable frame spring piece mounting seat, a movable frame working force sensor mounting seat, a second movable frame spring piece mounting seat and a movable frame standard force sensor mounting seat; the movable frame standard force sensor mounting seat is fixedly mounted on the bottom surface of the front end of the movable frame body along the length direction of the movable frame body; the first movable frame spring piece mounting seat comprises 2 fixed mounting seats which are fixedly mounted on the bottom surface of the front end of the movable frame body and are respectively positioned on two sides of the movable frame standard force sensor mounting seat; the movable frame working force sensor mounting seat is fixedly mounted at the bottom of the movable frame body and is positioned on a central line along the length direction of the movable frame body; the second movable frame spring piece mounting seat comprises 2 spring pieces which are respectively fixedly mounted on the bottom surface of the rear end of the movable frame body.

5. The engine test stand of claim 4, wherein:

the fixed frame comprises a base, a front mounting seat, a loading mechanism mounting seat, a first fixed frame spring piece mounting seat, a fixed frame working force sensor mounting seat, a rear mounting seat and a second fixed frame spring piece mounting seat; the base is of a cuboid structure, the front mounting seat and the rear mounting seat are fixedly mounted at the front end and the rear end of the base respectively along the length direction of the base, the rear mounting seat comprises a transverse plate and a vertical plate, and the transverse plate and the vertical plate form an L shape; the loading mechanism mounting seats are fixedly mounted on the front mounting seat, the number of the first fixing frame spring piece mounting seats is 2, and the first fixing frame spring piece mounting seats are fixedly mounted at the front end of the base and are respectively positioned on two sides of the front mounting seat; the fixed frame working force sensor mounting seat is fixedly arranged on the base and is positioned on a central line along the length direction of the base; the second fixed frame spring piece mounting seat comprises 2 spring pieces which are fixedly mounted at the rear end of the base and are respectively positioned on two sides of the rear mounting seat.

6. The engine test stand of claim 5, wherein: the loading measuring device comprises a first spring piece, a second spring piece, a loading mechanism, a standard force sensor and a working force sensor; the number of the first spring pieces is 2, each first spring piece is fixedly connected with a first fixed frame spring piece mounting seat and a first movable frame spring piece mounting seat, the number of the second spring pieces is 2, and two ends of each second spring piece are fixedly connected with a second fixed frame spring piece mounting seat and a second movable frame spring piece mounting seat respectively; the loading mechanism is fixedly arranged on a transverse plate of the front mounting seat, the standard force sensor is fixedly arranged on a baffle plate at the front end of the movable frame body, and the loading mechanism and the standard force sensor are coaxially arranged and are parallel to the central line of the base along the length direction; the two ends of the working force sensor are respectively and fixedly connected with the fixed frame working force sensor mounting seat and the movable frame working force sensor mounting seat, and the working force sensor, the loading mechanism and the standard force sensor are coaxially arranged.

7. The engine test bed noise reduction device of claim 1, comprising a tower, a variable frequency diffuser and a noise reduction fin assembly; the top end of the tower body is provided with a top cover, and one side surface of the tower body is provided with a mounting hole of a variable-frequency diffuser; the variable-frequency diffuser penetrates through the variable-frequency diffuser mounting hole and is horizontally and fixedly mounted in the tower body; the silencing sheet component is fixedly arranged in the tower body.

8. The engine test bed according to claim 7, wherein the variable-frequency diffuser comprises a variable-frequency diffuser cylinder and a variable-frequency diffuser diversion cone, the variable-frequency diffuser cylinder is a hollow circular cylinder, a plurality of variable-frequency diffuser air outlet holes are formed in the surface of the cylinder, and the variable-frequency diffuser air outlet holes are through holes penetrating through the circular cylinder; the frequency conversion diffuser flow guide cone is cone-shaped, the conical surface of the frequency conversion diffuser flow guide cone is arranged inside the circular cylinder, and the excircle of the bottom of the frequency conversion diffuser flow guide cone is fixedly connected with one end face of the circular cylinder.

9. The engine test bed according to claim 7, wherein the silencing sheet assembly comprises a lower silencing sheet assembly, a middle silencing sheet assembly and an upper silencing sheet assembly which are arranged in sequence from bottom to top.

10. A method of testing an engine under test using the engine test stand of any one of claims 1-9, comprising the steps of:

s100), installing the tested engine and measuring section

S110), sequentially enabling a measuring section for measuring air inlet parameters of the engine to pass through a first measuring section bracket and a second measuring section bracket, and placing the measuring section in the first measuring section bracket and the second measuring section bracket;

s120), mounting the front joint and the rear joint on an engine mounting top frame according to the suspension position of the tested engine;

s130), mounting the engine to be tested on the front joint and the rear joint after mounting the engine mounting frame on the movable frame body;

s140), adjusting the measuring section, namely, after one end of the measuring section is connected with an air inlet of the tested engine, adjusting a bracket of the measuring section to enable the measuring section and the air inlet of the engine to be coaxial and then positioning the measuring section;

s200), disassembling and locking device

Loosening the fastening nut, pulling out the fastening screw from the vertical plate of the rear mounting seat, fastening the baffle plate and the baffle plate at the rear end of the movable frame body in sequence, and taking out the fastening baffle plate;

s300), determining the error of the working force sensor

S310), the industrial personal computer controls the servo motor to start to drive the hydraulic loading device to work, the hydraulic loading device drives the calibration oil cylinder to work, a piston of the calibration oil cylinder drives the standard force sensor to displace so as to drive the movable frame body to displace, and force is applied to the working force sensor in the process that the movable frame body displaces;

s320), the hydraulic loading device drives the calibration oil cylinder to work, and after loading force is continuously applied to the standard force sensor to a preset value, the loading force is unloaded to a zero value; the standard force sensor data acquisition device and the working force sensor data acquisition device respectively acquire force values output by the standard force sensor and the working force sensor in the loading force applying and unloading processes and feed the force values back to the industrial personal computer, and the display displays the force values output by the standard force sensor and the working force sensor in the loading force applying and unloading processes, wherein the force values are acquired by the standard force sensor data acquisition device and the working force sensor data acquisition device;

s330), drawing characteristic curve graphs of the standard force sensor and the working force sensor according to force values output by the standard force sensor and the working force sensor in the loading force applying and unloading processes, wherein the standard force sensor and the working force sensor are displayed by a display and acquired by the standard force sensor data acquisition device and the working force sensor data acquisition device; under the same loading force, the difference between the force value output by the working force sensor acquired by the working force sensor data acquisition device and the force value output by the standard force sensor acquired by the standard force sensor data acquisition device is the working force sensor error;

s400), simulating engine air inlet parameters

S410), adjusting an engine intake air supply pressure adjusting valve and an oxygen supply flow adjusting valve according to the intake total pressure and the oxygen content of the simulated state point, so that the total pressure and the oxygen content of the second medium passing through the supersonic speed expansion section outlet of the measuring section are the same as the intake total pressure and the oxygen content of the engine of the simulated state point;

s420), adjusting an alcohol supply flow regulating valve according to the total intake temperature of the simulation state point, starting an igniter, igniting alcohol to combust the alcohol, exchanging heat between the combusted alcohol and a second medium of a second medium channel in a first medium channel, and enabling the total temperature of the second medium passing through an outlet of a supersonic expansion section of a measuring section to be the same as the total intake temperature of an engine in the simulation state point;

s430), adjusting an engine intake air supply pressure adjusting valve according to the intake total pressure of the simulation state point, so that the total pressure of the second medium passing through the supersonic expansion section outlet of the measuring section is the same as the intake total pressure of the engine at the simulation state point;

s440), gas discharged from the gas discharge pipeline enters from the end face of one open end of the cylinder of the variable-frequency diffuser, is guided by a flow guide cone of the variable-frequency diffuser, and is discharged from a plurality of gas outlet holes of the variable-frequency diffuser, and the gas discharged from the gas outlet holes of the variable-frequency diffuser is discharged from an outlet at the top of the tower body after being silenced and denoised by staggered gas flow channels formed by 3 layers of silencer component blocks;

s500), state point simulation test and measurement of thrust of tested engine under state point

Adjusting an engine fuel supply flow regulating valve according to the fuel demand of the engine simulation state point to ensure that the fuel supplied by a fuel supply source is the same as the fuel demand of the engine simulation state point, igniting the engine, carrying out an air intake simulation test of the simulation state point, and displaying the force value output by the working force sensor acquired by the working force sensor data acquisition device by a display;

Respectively adjusting an oxygen supply flow regulating valve, an engine air inlet supply pressure regulating valve, an alcohol supply flow regulating valve and an engine fuel supply flow regulating valve, so that the total pressure, the total temperature and the oxygen content of a second medium at the outlet of the supersonic expansion section of the measuring section are the same as the total intake pressure, the total temperature and the oxygen content of the engine at the Nth simulation state point, and the fuel supplied by a fuel supply source is the same as the fuel demand of the engine at the Nth simulation state point; wherein N is more than or equal to 2; starting an air inlet simulation test of the Nth state point of the engine to the air inlet simulation test of the state point and measuring the thrust measurement of the tested engine at the state point according to the method in the step S500;

s700), closing the air inlet system and the exhaust pipeline of the test bed

And (3) shutting off the fuel supply flow regulating valve, the oxygen supply flow regulating valve, the air inlet supply pressure regulating valve and the alcohol supply flow regulating valve of the engine after the engine is shut down, and shutting off the active air flow supply pressure regulating valve of the ejector.