CN106568397A - Determination method of aero-engine installation center surface - Google Patents

Abstract

The method for determining the installation center plane of an aero-engine provided by the invention utilizes the principle of equal water levels, adopts a transparent PVC transparent plastic U-shaped pipe, a horizontal laser line meter and a length measuring instrument to calibrate the measurement points of the aero-engine, and the four measurement points before and after the installation The deviation of the central plane P is ≤1mm, and the central plane of the aero-engine installation can be identified through 4 measuring points. The method of the invention is suitable for the factory inspection of the aero-engine, the review inspection of the aircraft assembly engine and the installation inspection of the aero-engine under the condition of outfield use, and has good engineering practical value.

Description

The Method of Determining the Mounting Center Plane of Aeroengine

technical field

The invention relates to the technology of installing an aero-engine on an aircraft, in particular to a method for determining an engine installation center plane as an installation reference in the aero-engine installation.

Background technique

The aero-engine is installed on the aircraft, and there are strict design requirements for the installation angle between the engine installation center plane (abbreviated as the center plane) and the assembly datum on the aircraft, so as to ensure the air flight design requirements of the aircraft. The installation center plane of aero-engine is identified by measuring points on the aero-engine casing in engineering practice. Existing part aero-engine is in manufacturing production process, and its measuring point has been processed in its components (casing at the outer circle place of installation joint measuring point, front measuring point and rear measuring point) process. In order to show the difference, the measuring point made by processing is called the original measuring point. According to the requirements of the design drawings, the accuracy of the original measuring point relative to the frame reference of the body can reach within ±0.5mm. When the engine is assembled, the compressor, the combustion chamber, and the casing of the turbine components are connected together by fasteners such as screws. Due to the gap between the screw holes and the screws, there is a gap between the original measuring point and the actual installation center plane P after the engine is assembled. Certain deviations. For a single-duct casing, the original measuring point will rotate around the central axis G of the engine rotor, and the two measuring points are on both sides of the installation center plane P and the distance from P is equal; In addition to the rotation of the axis G, there may still be a deviation ξ between the casing center Q ₂ ′ of the measuring point and the rotor central axis G, and the compound deviation does not rotate around G, nor does it necessarily maintain the same distance from P on both sides of P. The more the number of connected casings and the larger the outline size, the greater the deviation between the original measuring point of the engine and the installation center plane P may be. In some cases, the composite deviation may exceed the range allowed by the technical requirements of the aircraft installation. The technical status relationship of the measurement points of the aero-engine casing, the center plane P of the engine installation and other related elements are shown in Figures 1 and 2. In order to ensure that the aero-engine is assembled on the aircraft within the scope of the design requirements, the original measuring points must be calibrated to confirm whether the measuring points meet the requirements. When the original measurement point does not meet the requirements, the original measurement point mark should be corrected to obtain a new measurement point.

Contents of the invention

The purpose of the present invention is to provide a new method for determining the installation center plane of an aero-engine to ensure that each measuring point of the aero-engine meets the technical requirements for aircraft installation, so as to ensure that the aero-engine is assembled on the aircraft to meet the design requirements of the aircraft.

The method for determining the mounting center plane of an aero-engine provided by the present invention comprises the following process steps:

(1) Install the aero-engine on a stable support platform with both roll angle α and shaft inclination angle β less than 1°;

(2) Measure the height difference y between the measuring points E and F of the installation node: use a transparent U-shaped tube filled with tap water, so that the liquid level at one end of the water body in the U-shaped tube is on the outer circle P ₀ of the engine installation node measuring point The measuring point E or F of the U-shaped pipe is flush, and the height difference y between the liquid level at the other end of the water body in the U-shaped pipe and the measuring point F or E is measured;

(3) Calculate the engine roll angle α: Calculate the roll angle of the two measuring points according to the height difference y and the casing diameter φ ₀ of the section where the engine installation node is located Record the magnitude of α and the direction of deflection between α along the sailing direction and the horizontal plane S, if α is greater than 1°, readjust the support platform so that α is less than 1°;

(4) Calculate the height difference δ _{1 of} the new measuring point before the engine _: Calculate the engine front left, The height difference between the right new measuring point A ₁ and B ₁ is δ ₁ =(φ ₁ /φ ₀ )*y;

(5) Measure height difference q ₁ between former original measuring points and former original roll angle α ₁ : use the same method as step (2) to measure the distance between former original measuring points A′ ₁ and B′ ₁ on outer circle P ₁ of former measuring points height difference q ₁ , use the same method as step (3) to calculate the front original roll angle Record the magnitude of α ₁ and the direction of deflection between α ₁ and the horizontal plane S along the sailing direction;

(6) Determine the distance between the previous new measuring point A ₁ and the former original measuring point A′ ₁ : when α ₁ and α are on the same side of the horizontal plane, calculate A′ ₁ and A through |δ ₁ -q ₁ |/2 The distance between ₁ : when δ ₁ >q ₁ , the new measuring point A ₁ moves away from the horizontal plane S on the basis of the original measuring point A′ ₁ ; when δ ₁ <q ₁ , the new measuring point A ₁ is at the original measuring point A' ₁ basically moves towards the direction of the horizontal plane S; when δ ₁ =q ₁ , the new measuring point A ₁ is in the same position as the original measuring point A' ₁ and does not need to be moved; when α ₁ and α are on different sides of the horizontal plane, Calculate the distance between A′ ₁ and A ₁ by |δ ₁ +q ₁ |/2, the new measurement point A ₁ is on the other side of the horizontal plane S relative to the original measurement point A′ ₁ ;

(7) mark the front new measuring point A ₁ on the preceding measuring point casing;

(8) Same as steps (6) and (7), mark out the previous new measuring point B ₁ on the other side of the preceding measuring point casing;

(9) New measuring point A ₂ after determination: use the laser line projector to form a triangle ΔEA ₁ A″ ₁ and a triangle ΔEA ₂ A″ ₂ by installing the horizontal laser line W of the left measuring point E on the outer circle P ₀ of the node, where A ″ ₁ is the intersection point of the horizontal laser line W and the outer circle P ₁ of the previous measurement point, A″ ₂ is the intersection point of the horizontal laser line W and the outer circle P ₂ of the rear measurement point, and the two triangles are similar Measure the distance x ₁ between the new measurement point A ₁ and the horizontal laser line W (the axis inclination can be checked by x ₁ value, if β is greater than 1°, re-adjust the support platform), according to the similar triangle relationship according to the formula x ₂ = (L ₂ /L ₁ ) x ₁ to get x ₂ , determine the new measuring point A ₂ ;

(10) same as step (9) method, obtain rear new measuring point B ₂ ;

(11) The plane where the front new measuring points A ₁ and B ₁ and the rear new measuring points A ₂ and B ₂ are located is the engine installation center plane P.

In the method for determining the center plane of the aero-engine installation described above, for existing engine installation node measurement points E and F, the existing engine installation node measurement point baseline N ₀ can be used as a reference to calibrate the measurement points A ₁ , B ₁ , and A ₂ , B ₂ ; if there is no engine installation node measuring point E, F, the engine installation node baseline N should be used as the benchmark, the engine installation node measuring point E, F should be calibrated first, and then the measuring points A ₁ , B ₁ , A ₂ , _B2 .

In the method for determining the installation center plane of the above-mentioned aero-engine, for each measurement of the height difference of the measuring points of the same section, the water level of the U-shaped pipe is first aligned with the left measuring point, and the height difference between the right measuring point and the water level is read; Align the water level of the U-shaped pipe with the measuring point on the right, and read the height difference between the measuring point on the left and the water level; it is required that the error of each reading measurement value shall not be greater than 0.5mm; the total number of measurements shall not be less than 2 times, and the final result The average value shall prevail; if the error of a single measurement is greater than 0.5mm, consider replacing the U-shaped tube.

In the method for determining the installation center plane of the above-mentioned aero-engine, before using the U-shaped tube for measurement, it is necessary to remove the air bubbles in the water body in the U-shaped tube to ensure that the liquid level of the water in the U-shaped tube is stable; After the water level is stable, observe the water level at both ends, and the water level in the U-shaped pipe is required to be equal.

In the method for determining the installation center plane of the aero-engine, the U-shaped pipe is preferably a PVC transparent plastic pipe. Furthermore, a PVC transparent plastic pipe with an outer diameter of 4mm and a pipe wall thickness of 1mm is selected.

In the method for determining the installation center plane of the aero-engine, the laser line projector is preferably EK-155AP laser line projector.

The method for determining the mounting center plane of an aero-engine provided by the invention is mainly applicable to engines with non-single-duct or non-integral structure of inner and outer duct casings. For the case where the installation section is a single duct or the inner and outer ducts are integrally processed, on the main body case, the deviation between the original measuring point and the left and right installation nodes of the engine can be guaranteed to be within ±0.5mm. That is to say, the error of using the fixed hole position of the outer circular casing and the installation joint to replace the base line N ₀ of the engine installation node measurement point (that is, the measurement point reference K1 of the center plane of the aeroengine installation) is less than ±0.5mm.

The method for determining the installation center plane of the aero-engine provided by the present invention utilizes the principle of equal water levels, adopts transparent PVC transparent plastic U-shaped pipes and other measuring instruments to calibrate the measurement points of the aero-engine, and the deviation between the front and rear four measurement points and the installation center plane can be ≤1mm The installation center plane of the aero-engine can be identified through 4 measuring points. The method of the invention is applicable to the delivery inspection of the general assembly of the aero-engine, the review inspection of the aircraft assembly engine and the installation inspection of the aero-engine under the condition of using in the field.

The method for determining the installation center plane of an aero-engine provided by the present invention is applicable to the calibration of measuring points of the aero-engine installation center plane in a stable support state where the roll angle α and the shaft inclination angle β are both less than 1°.

Description of drawings

Figure 1 is a schematic diagram illustrating the technical status of the center plane of the aero-engine installation and its measuring points.

Figure 2 is a schematic diagram of the state of a certain type of aero-engine on the transfer vehicle.

Figure 3 is the height difference measurement of the installation center plane of a certain type of engine.

Figure 4 is a schematic diagram of the relationship between the new measuring point and the original measuring point in front of a certain type of engine.

Figure 5 is a schematic diagram of the relationship between the new measuring point and the original measuring point behind a certain type of engine.

Fig. 6 is a schematic diagram of the geometric relationship of each measurement point and the similar triangles of the laser projection line.

Figure 7 is a schematic diagram of the left measuring point of a certain type of engine.

The various symbols used in the method for determining the mounting center plane of the aero-engine provided in the present invention and the accompanying drawings are defined as follows:

P ₁ , P ₀ : respectively, the outer circle of the measuring point in front of the engine and the outer circle of the measuring point of the engine installation node. The center of the outer circle is on the central axis G of the engine rotor, the radius of the outer circle is the distance from the measuring point of each section to G, and the plane formed by the outer circle is perpendicular to the central axis G of the engine rotor.

P ₂ : The outer circle of the rear measuring point of the engine, the plane formed by the outer circle is perpendicular to the central axis G of the engine rotor, the center of the outer circle is at the center Q′ ₂ of the engine shell of the section of the rear measuring point, and the radius of the outer circle is the original measuring point of the section (A ' ₂ or B' ₂ ) to Q' ₂ distance.

A ₁ , B ₁ , E, F, A ₂ , B ₂ : A ₁ , B ₁ are the front left and right measurement points after engine calibration respectively, E and F are the left and right measurement points of the engine installation node respectively, A ₂ and B ₂ are the measured points on the rear left and right sides of the engine after calibration. Respectively referred to as the front new measuring point, the installation node measuring point and the rear new measuring point;

E ₀ , F ₀ : are respectively the left installation node of the engine and the right installation node of the engine;

A′ ₁ , B′ ₁ , A′ ₂ , B′ ₂ : A′ ₁ , B′ ₁ are the front left and right measuring points before engine calibration, respectively; A′ ₂ , B′ ₂ are the measurement points before engine calibration Back left and right measuring points. The above measuring points are the original measuring points, referred to as the former original measuring point and the rear original measuring point respectively.

N, N ₁ , N ₀ , N ₂ : N is the baseline of the engine installation node (the connection of the installation nodes on both sides), N ₁ is the baseline of the front measurement point of the engine (the connection of the new measurement points on the front two sides), and N ₀ is the engine installation Node measurement point baseline (connection of measurement points on both sides of the installation node); N ₂ is the baseline of engine rear measurement points (connection of new measurement points on both sides of the rear). The baselines are parallel to each other, wherein the baselines N ₁ , N ₀ , and N ₂ pass through the central axis G of the rotor of the aeroengine and the installation center plane P of the aeroengine.

N _S : the horizontal baseline of the engine installation node, the intersection line of the horizontal plane S and the outer circle P ₀ plane of the engine installation node measurement point.

Q ₁ , Q ₀ , Q ₂ , Q′ ₂ : Q ₁ is the outer circle center of the engine front measuring point, Q ₀ is the outer circle center of the engine installation node measuring point, Q ₂ is the outer circle P ₂ plane of the engine rear measuring point and the engine The intersection point of the center line G, Q′ ₂ is the center of the outer circle of the measuring point behind the engine;

φ ₁ , φ ₀ , φ ₂ : φ ₁ is the diameter of the outer circle P ₁ of the engine front measuring point, φ ₀ is the diameter of the outer circle P ₀ of the engine installation node measuring point, and φ ₂ is the diameter of the outer circle P ₂ of the engine rear measuring point;

L ₁ , L ₂ : L ₁ is the distance between the outer circle P ₀ of the engine installation node measuring point and the outer circle P ₁ of the engine front measuring point, L ₂ is the outer circle P ₀ of the engine installation node measuring point and the outer circle of the engine rear measuring point the distance between P2 _;

G: The central axis of the rotor of the aeroengine (referred to as the centerline), the straight line passing through the engine shaft.

P: The center plane of the aero-engine installation, the plane passing through the centerline G and the base line N ₀ of the engine installation node measuring points.

S _: The horizontal plane passing through the center Q0 of the outer circle of the measuring point of the engine installation node.

K ₁ , K ₂ : K ₁ is the design basis 1 of the engine installation center plane P established on the engine installation node measuring point baseline N ₀ ; K ₂ is the design basis 2 of the engine installation center plane P established on the engine rotor centerline G .

The distance between the center Q′ ₂ of the outer circle P ₂ of the engine rear measuring point and the center line G.

α: engine roll angle, the angle between the baseline N ₀ of the engine installation node measuring point and the engine horizontal plane S.

α ₁ : The original roll angle in front of the engine, the angle between the connecting line A′ ₁ B′ ₁ of the engine measuring points and the horizontal plane S of the engine.

β: Engine shaft inclination, the angle between the centerline G of the aeroengine rotor and the horizontal plane S.

detailed description

Embodiments are given below in conjunction with the accompanying drawings, and the present invention will be further described through the embodiments.

Adopt the method of the present invention to carry out aeroengine measuring point calibration, should consider the technical requirement of aircraft installation, according to GJB/J2739-1996 "General Regulations for the Compilation of National Defense Measuring Apparatus Class Chart" selected measuring instruments.

In the example of measuring point calibration of a certain type of engine given below, the reference conversion error, the system error of the measuring instrument and the indication error of the read measurement value are considered comprehensively, and the calibrated measuring point meets the technical requirements of the aircraft installation.

Example

The engine of this embodiment is a turbofan engine with double ducts, the outer circle P1 _of the front measuring point of the engine is a single ducted casing, and the outer circle P2 of the rear measuring point is a _double ducted casing, and its center _Q2 may deviate from the center Line G, assuming biased (shown in Figure 1 and Figure 5 along the vertical direction). According to the installation technical requirements of an aircraft, the following measuring instruments and equipment were selected to calibrate the measuring points of the center plane of an aero-engine.

Measuring instruments and equipment used:

1) U-shaped tube (material: transparent PVC transparent plastic tube, tube size: outer diameter 4mm, tube wall thickness 1mm, length 3m), filled with tap water;

2) EK-155AP laser line projector;

3) The computer prints a transparent tape with a ratio of 1:1 (attached to the U-shaped tube to measure the stable water level).

The overall steps are as follows:

1) In any stable support state of the engine, using the principle of equal water level, the height difference of the original measuring points A′ ₁ /A′ ₂ and B′ ₁ /B′ ₂ are respectively obtained by using equal water levels at both ends of the U-shaped tube, and the height differences of each measuring point are recorded Original mark (note: pay attention to the deflection direction of each measuring point when recording).

2) Measure and calculate the roll angle α (see Figure 1), transfer the roll angle to the outer circle P1 _of the front measuring point, and determine the positions _of the measuring points A1 and B1 _of the front center plane.

3) Using the principle of similar triangles, through the front new measuring point A ₁ /B ₁ and the dashed line E/F of the installation measuring point (actually E ₁ /F ₁ and E ₂ /F ₂ ), the measuring point A ₂ of the rear center plane is obtained /B ₂ . For aero-engines with a stable support whose roll angle and shaft tilt angle are both less than 1°, the influence of the roll angle on the measurement accuracy has been considered.

Specific program steps:

a) Fill the U-shaped tube with tap water to eliminate blisters in the water body in the tube. Align the two ends of the U-shaped tube. After the water level is stable, observe the water level at both ends. It is required that the water level in the tube is even.

b) Hoist the engine on a stable supporting trolley with a side inclination angle and a shaft inclination angle less than 1° (see Figure 2).

c) Measure the height difference y between the measuring points E and F on the left and right sides of the engine installation node, record its value and deflection direction (see Figure 3), according to the formula δ ₁ =(φ ₁ /φ ₀ )y and δ ₂ =(φ ₂ /φ ₀ )y calculates δ ₁ and δ ₂ .

d) Measure and record the height difference q ₁ of the former original measuring points (A' ₁ and B' ₁ ).

e) Measure and record the height difference q ₂ of the rear original measuring point (A' ₂ and B' ₂ ).

f) Determining the new measurement points A ₁ and B ₁ before: When the deflection direction of the original measurement point is consistent with the deflection direction of the installation node measurement point reference N ₀ , A ₁ A′ ₁ = |δ ₁ -q ₁ |/2, when When δ ₁ >q ₁ , the new measuring point A ₁ moves away from the horizontal plane S on the basis of the original measuring point A′ ₁ ; when δ ₁ <q ₁ , the new measuring point A ₁ moves closer to the original measuring point A′ ₁ Move in the S direction of the horizontal plane; when δ ₁ =q ₁ , the new measuring point A ₁ is in the same position as the original measuring point A' ₁ and does not need to be moved. When α ₁ and α are on different sides of the horizontal plane, the distance between A′ ₁ and A ₁ is calculated by |δ ₁ +q ₁ |/2, and the new measuring point A ₁ is on the horizontal plane S relative to the original measuring point A′ ₁ the other side of the

g) Mark the new front measuring point A ₁ on the front measuring point casing.

h) Same as steps (6) and (7), mark the new front measuring point B ₁ on the other side of the front measuring point casing.

i) Use the EK-155AP laser line thrower to install the node outer circle P ₀ left measuring point E (the center of the transport fulcrum of this type of engine has been installed with a bracket, and the node measuring point E is composed of two measuring points E ₁ and E ₂ ), Respectively intersect the outer circle P ₂ of the rear measurement point at two points, that is, the new measurement point A _2,1 and A _2,2 to form an adjustable interval (the new measurement point A _2,1 and A _2,2 pass through x ₂ =(L ₂ /L ₁ )·x ₁ is calculated, and its relationship is shown in Figure 6). Using the same method, get B _2,1 and B _2,2 to form the adjustable interval on the other side.

j) Take the midpoint of the interval A _2,1 and A _2,2 on the left as the initial position of the new measuring point on the rear left, and take the midpoint of the interval B _2,1 and B _2,2 on the right as the initial position of the new measuring point on the rear right The positions are clearly marked with a pencil.

k) The initial value of the height difference of the initial position of the new measuring point on both sides after marking with a U-shaped tube and a measuring pencil, and compare it with δ ₂ , where δ ₂ =(φ ₂ /φ ₀ )y. _The error between the initial value and δ2 is required to be greater than 0.5mm. If the requirement is not met, adjust the pencil mark in the adjustable range on both sides, and re-measure the height difference until the requirement is met.

l) When the initial position meets the requirements, change the pencil mark to a permanent mark (scratch mark for removing material) or semi-permanent mark (paint mark), and record the height difference of the new measuring point.

m) The plane determined by the previous new measuring points A ₁ , B ₁ , and the rear new measuring points A ₂ , B ₂ is the engine installation center plane P.

Precautions:

1) For each measurement of the height difference of the measuring points of the same section, first align the water level of the U-shaped pipe to the left measuring point, and read the height difference between the right measuring point and the water level; then align the water level of the U-shaped pipe to the right measuring point point, read the height difference between the left measuring point and the water level. It is required that the error of the measured value of each reading shall not be greater than 0.5mm. The total number of measurements shall not be less than 2 times, and the final result shall be based on the average value. If the error of a single measurement is greater than 0.5mm, consider replacing the U-shaped tube.

2) In order to improve the indication error of the measured value, the symbol "+" or "-" is used to indicate the deviation of the measured value after the selected graduation value (the interval of the graduation value is 0.5mm); "+" means greater than the graduation value, "-" means less than the division value. Use "+" to indicate that the measured value adds a deviation ≤ (0-0.25) mm on the basis of the scale value; use "-" to indicate that the measured value subtracts a deviation ≤ (0-0.25) mm on the basis of the scale value deviation. For example: "2+" indicates that the measured value is within the range of (2~2.25) mm, "2.5 ^- " indicates that the measured value is within the range of (2.25 ~ 2.5) mm, "2 ^- " indicates that the measured value is (1.75 ~ 2) mm within range.

Claims (8)

1. A method for determining the mounting center plane of an aero-engine is characterized in that it comprises the following process steps: (1) Install the aero-engine on a stable support platform with both roll angle α and shaft inclination angle β less than 1°; (2) Measure the height difference y between the measuring points E and F of the installation node: use a transparent U-shaped tube filled with tap water, so that the liquid level at one end of the water body in the U-shaped tube is on the outer circle P ₀ of the engine installation node measuring point The measuring point E or F of the U-shaped pipe is flush, and the height difference y between the liquid level at the other end of the water body in the U-shaped pipe and the measuring point F or E is measured; (3) Calculate the engine roll angle α: Calculate the roll angle of the two measuring points according to the height difference y and the casing diameter φ ₀ of the section where the engine installation node is located Record the magnitude of α and the direction of deflection between α along the sailing direction and the horizontal plane S, and if α is greater than 1°, re-adjust the support platform so that α is less than 1°; (4) Calculation of height difference δ ₁ of the new measuring point before the engine: According to the casing diameter φ ₁ of the section where the outer circle P ₁ of the front measuring point of the engine is located and the obtained height difference y between the measuring points of the installation node, calculate the front left side of the engine , the height difference between the new measuring points A ₁ and B ₁ on the right δ ₁ =(φ ₁ /φ ₀ )*y; (5) Measure height difference q ₁ between former original measuring points and former original roll angle α ₁ : use the same method as step (2) to measure the distance between former original measuring points A′ ₁ and B′ ₁ on outer circle P ₁ of former measuring points height difference q ₁ , use the same method as step (3) to calculate the front original roll angle Record the magnitude of α ₁ and the direction of deflection between α ₁ and the horizontal plane S along the sailing direction; (6) Determine the distance between the previous new measuring point A ₁ and the former original measuring point A′ ₁ : when α ₁ and α are on the same side of the horizontal plane, calculate A′ ₁ and A through |δ ₁ -q ₁ |/2 The distance between ₁ : when δ ₁ >q ₁ , the new measuring point A ₁ moves away from the horizontal plane S on the basis of the original measuring point A′ ₁ ; when δ ₁ <q ₁ , the new measuring point A ₁ is at the original measuring point A' ₁ basically moves towards the direction of the horizontal plane S; when δ ₁ =q ₁ , the new measuring point A ₁ is in the same position as the original measuring point A ₁ ′, and does not need to move; when α ₁ and α are on different sides of the horizontal plane, Calculate the distance between A′ ₁ and A ₁ by |δ ₁ +q ₁ |/2, the new measurement point A ₁ is on the other side of the horizontal plane S relative to the original measurement point A′ ₁ ; (7) mark the front new measuring point A ₁ on the preceding measuring point casing; (8) Same as steps (6) and (7), mark out the previous new measuring point B ₁ on the other side of the preceding measuring point casing; (9) New measuring point A ₂ after determination: use the laser line projector to form a triangle ΔEA ₁ A″ ₁ and a triangle ΔEA ₂ A″ ₂ by installing the horizontal laser line W of the left measuring point E on the outer circle P ₀ of the node, where A ″ ₁ is the intersection point of the horizontal laser line W and the outer circle P ₁ of the previous measurement point, A″ ₂ is the intersection point of the horizontal laser line W and the outer circle P ₂ of the rear measurement point, and the two triangles are similar Measure the distance x ₁ between the new measuring point A ₁ and the horizontal laser line W, obtain x ₂ according to the formula x ₂ =(L ₂ /L ₁ )·x ₁ according to the similar triangle relationship, and determine the new measuring point A ₂ ; and if the axis If the inclination β is greater than 1°, re-adjust the support platform; (10) same as step (9) method, obtain rear new measuring point B ₂ ; (11) The plane where the front new measuring points A ₁ and B ₁ and the rear new measuring points A ₂ and B ₂ are located is the engine installation center plane P. 2. The method for determining the installation center plane of an aero-engine according to claim 1 is characterized in that, for those without engine installation node measurement points E, F, the engine installation node baseline N should be used as a benchmark to first calibrate the engine installation node measurement points Points E and F, and then calibrate the measuring points A ₁ , B ₁ , A ₂ , and B ₂ . 3. The method for determining the installation center plane of an aero-engine according to claim 1 or 2, characterized in that, for each measurement of the height difference of the measuring points of the same section, the water level of the U-shaped pipe is first aligned with the measuring point on the left side, and the reading The height difference between the measuring point on the right and the water level; then align the water level of the U-shaped tube with the measuring point on the right, and read the height difference between the measuring point on the left and the water level; the error of the measured value for each reading is required to be no greater than 0.5mm ;The total number of measurements is not less than 2 times, and the final result is based on the average value; if the error of a single measurement value is greater than 0.5mm, it is necessary to consider replacing the U-shaped tube. 4. The method for determining the mounting center plane of an aero-engine according to claim 1 or 2, characterized in that, before using the U-shaped tube for measurement, the U-shaped tube is filled with tap water to an appropriate position to meet the measurement needs, and the U-shaped tube is placed Air bubbles in the water body are eliminated. 5. The method for determining the installation center plane of an aero-engine according to claim 1 or 2, characterized in that, before using the U-shaped tube to measure, the two ends of the U-shaped tube are aligned, and the water level at both ends is observed after the water level is stable, The water level is required to be level. 6. The method for determining the mounting center plane of an aero-engine according to claim 1 or 2, wherein the U-shaped pipe is a PVC transparent plastic pipe. 7. The method for determining the installation center plane of an aero-engine according to claim 6, characterized in that, the transparent PVC transparent plastic pipe used as the U-shaped pipe has an outer diameter of 4mm and a pipe wall thickness of 1mm. 8. The method for determining the mounting center plane of an aero-engine according to claim 1 or 2, wherein the laser line thrower is an EK-155AP laser line thrower.