A method for evaluating the cooling and lubrication effect of lubricating oil in intermediate bearings of aircraft engines

Abstract

The present invention belongs to the field of aircraft engine lubricating oil system design and discloses a method for evaluating the cooling and lubricating effect of the lubricating oil of an intermediate bearing of an aircraft engine. Through simulation analysis, several parameters, namely, the oil film coverage area on the surface of the bearing roller, the oil film coverage area on the surface of the bearing retainer, and the oil collection coefficient, are obtained. These parameters are respectively dimensionally processed and multiplied by a weight coefficient to obtain comprehensive analysis parameters that can be used to analyze the cooling and lubricating effect of the lubricating oil of the intermediate bearing, and the cooling and lubricating effect of the lubricating oil of the intermediate bearing is quantitatively analyzed. The method can quantitatively analyze the cooling and lubricating effect of the lubricating oil of the intermediate bearing at different operating speeds, and by considering the change in the relative position between the rotor roller and the oil delivery hole of the bearing inner ring, the comprehensive analysis parameters are made more accurate and comprehensive.

Description

Technical Field

[0001] The invention belongs to the field of aircraft engine lubricating oil system design, and in particular relates to a method for evaluating the cooling and lubricating effect of lubricating oil on an intermediate bearing of an aircraft engine. Background Art

[0002] Aircraft engines are complex rotating machines operating in high-temperature, high-pressure, and high-load environments, requiring various systems to work in concert. For economic reasons, weight reduction is consistently implemented throughout the design, manufacturing, and maintenance of aircraft engines. Support solutions with intermediate bearings are widely used because they reduce the number of load-bearing frames, thereby achieving the goal of weight reduction. However, the inner and outer rings of the intermediate bearings are connected to different rotors, so the motion of the rotors significantly affects the relative positional relationships between the various components in the bearing. Furthermore, due to the harsh operating environment of intermediate bearings and the extreme difficulty of installation and maintenance, the cooling and lubrication design of intermediate bearings is a significant technical challenge. Analyzing the cooling and lubrication effects of the bearings is a prerequisite for designing and optimizing the lubricating oil flow path.

[0003] The intermediate bearing consists of four parts: the inner ring, the outer ring, the roller and the cage. The inner ring has oil holes evenly distributed along the circumference, and the lubricating oil reaches the cage and the roller through the oil holes.

[0004] Since all parts of the bearing are clearance-fitted, its inner ring always has a certain amount of eccentricity and works to one side. During operation, the inner and outer rings of the intermediate bearing rotate at their respective speeds along with different rotors. At the same time, under the influence of the centrifugal force of the rotor, the roller on the side of the inner ring of the bearing is pressed to rotate. During the movement, the roller on the pressure side impacts the front surface of the retaining frame groove, driving the retaining frame to rotate. During the movement, the rotating retaining frame collides with the roller on the opposite side of the pressure side at the rear surface of the retaining frame groove, causing the roller on the opposite side of the pressure side to rotate accordingly. In the above process, the front and rear sides of the retaining frame groove and the roller surface of the intermediate bearing are all impacted. These are areas that are extremely prone to wear, so it is necessary to pay special attention to the lubrication effect of these surfaces.

[0005] At the same time, because aircraft engine rotors have a large axial span and relatively weak angular stiffness, they are prone to bending and deformation during operation. For dual-rotor aircraft engines, the mass stiffness distribution of the high- and low-pressure rotors differs significantly, resulting in significant differences in the motion and deformation of the two rotors during operation. The inner and outer rings of the intermediate bearing are fixed to different rotors, respectively, so the inner and outer rings of the intermediate bearing tilt relative to each other under the influence of the two rotors. At this point, the tilted inner and outer rings of the bearing can no longer maintain a concentric rotational relationship with the bearing retainer, causing the inner and outer rings to collide with the inner and outer surfaces of the retainer, respectively, resulting in wear. Therefore, attention should also be paid to the distribution of lubricating oil on the inner and outer surfaces of the retainer.

[0006] In summary, when analyzing the cooling and lubrication effect of the intermediate bearing lubricant, it is necessary to focus on the lubricant distribution on the roller surface, the inner surface of the cage, the outer surface of the cage, the front side of the cage groove, and the rear side of the cage groove.

[0007] In addition, from the simulation analysis and test results of bearing lubrication, there are many factors that affect the cooling and lubrication effect of the bearing, among which the more important ones are the operating speed of the bearing and the relative position relationship between the bearing roller and the oil delivery hole of the bearing inner ring. However, the existing analysis method of the cooling and lubrication effect of the intermediate bearing lubricant is difficult to take into account the influence of these two factors. Therefore, based on the simulation calculation results of the cooling and lubrication of the intermediate bearing, the present invention extracts relevant parameters such as the surface oil film coverage area of ​​each component of the intermediate bearing and the lubricant flow rate of each oil delivery hole, and establishes a comprehensive analysis parameter that can take into account the operating speed of the bearing and the relative position of the bearing roller and the oil delivery hole of the bearing inner ring. It is used to analyze the cooling and lubrication effect of the intermediate bearing lubricant, which is of great significance for improving the design and optimization of the lubricant flow path of the intermediate bearing of the aircraft engine. Summary of the Invention

[0008] To solve the above technical problems, the present invention provides a method for evaluating the cooling and lubrication effect of lubricating oil in the intermediate bearing of an aircraft engine to solve the problems in the prior art. The technical solution adopted by the present invention is:

[0009] A method for evaluating the cooling and lubricating effect of lubricating oil in an intermediate bearing of an aircraft engine comprises the following steps:

[0010] Step 1), based on a given intermediate bearing, calculate the surface area of ​​the bearing roller and the surface area of ​​the bearing cage;

[0011] Step 2) obtaining the oil film coverage area of ​​the bearing roller surface, the oil film coverage area of ​​the bearing cage surface, and the oil collection coefficient at a given speed through simulation calculation;

[0012] Step 3), calculating the oil film coverage rate of the bearing cage surface at a given speed by using the surface area of ​​the bearing cage and the oil film coverage area of ​​the bearing cage surface, and calculating the oil film coverage rate of the bearing roller surface at a given speed by using the surface area of ​​the bearing roller and the oil film coverage area of ​​the bearing roller surface;

[0013] Step 4) The oil collection coefficient, the oil film coverage rate of the bearing roller surface, and the oil film coverage rate of the bearing cage surface are weighted by a weight coefficient to obtain an evaluation parameter at a given speed;

[0014] Step 5) The evaluation parameters at different speeds are fitted into a comprehensive evaluation parameter curve, and the comprehensive evaluation parameter curve is compared with a set threshold value to determine whether the cooling and lubrication effect of the intermediate bearing lubricating oil meets the requirements.

[0015] The present invention has the following beneficial effects:

[0016] (1) The loads and failure modes that each component in the intermediate bearing may receive during operation are fully considered, and the cooling and lubrication effects of the bearing under various working conditions can be fully characterized, which has strong engineering applicability;

[0017] (2) The difference in oil film coverage area on the roller surface due to the relative position between the roller and the oil delivery hole of the inner ring of the bearing during operation is taken into account, making the evaluation results closer to engineering practice;

[0018] (3) Since the cooling and lubrication effect of the bearing is closely related to its operating speed, the method of the present invention can more conveniently obtain a comprehensive analysis parameter curve corresponding to the speed, which has important guiding significance for the design of the bearing lubricating oil flow path. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 This is a schematic diagram of the position of the intermediate bearing of a twin-rotor aircraft engine;

[0020] Figure 2 This is a schematic diagram of the structure of the intermediate bearing of an aircraft engine;

[0021] Figure 3 Schematic diagram of the intermediate bearing cage;

[0022] Figure 4 It is a schematic diagram of the rotation direction and the inward and outward directions of the intermediate bearing;

[0023] Figure 5 This is a schematic diagram showing the calculation of the relative position parameters between the bearing roller and the oil delivery hole of the bearing inner ring (the cage is omitted for clarity);

[0024] Figure 6 It is the curve of comprehensive evaluation parameter curve obtained through simulation as the speed changes. DETAILED DESCRIPTION

[0025] The following is a combination of the embodiments of the present invention Figures 1-6 , the technical solutions in the embodiments of the present invention are described clearly and completely. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments. Unless otherwise specified, the technical means used in the embodiments are conventional means well known to those skilled in the art.

[0026] A method for evaluating the cooling and lubricating effect of lubricating oil in an intermediate bearing of an aircraft engine comprises the following steps:

[0027] Step 1) Calculate the surface area of ​​the roller and cage based on the given intermediate bearing. Figures 1-4 The detailed structural relationship of the intermediate bearing is given. Its structural distribution is based on existing technology. The intermediate bearing includes at least a bearing outer ring, a bearing roller, a bearing cage, a bearing inner ring, and an oil delivery hole in the bearing inner ring. The calculation method for obtaining the surface area of ​​the bearing roller and the bearing cage is also based on existing technology. For example, the surface area of ​​the bearing roller and the bearing cage can be read in commercial finite element software.

[0028] Step 2) Use commercial CFD software to establish a three-dimensional fluid model for bearing lubrication. Simulate the distribution of lubricating oil after it enters the bearing through simulation calculations to determine the oil film coverage area on the bearing roller surface, the oil film coverage area on the bearing retainer surface, and the oil recovery coefficient at a given speed. Specifically, the oil recovery coefficient is defined as the ratio of the amount of lubricating oil that enters the bearing from the oil delivery hole in the bearing inner ring and reaches the roller and retainer per unit time to the total oil supply per unit time.

[0029] Step 3), calculating the oil film coverage rate of the bearing cage surface at a given speed by using the surface area of ​​the bearing cage and the oil film coverage area of ​​the bearing cage surface, and calculating the oil film coverage rate of the bearing roller surface at a given speed by using the surface area of ​​the bearing roller and the oil film coverage area of ​​the bearing roller surface;

[0030] Step 4) The oil collection coefficient, the oil film coverage rate of the bearing roller surface, and the oil film coverage rate of the bearing cage surface are weighted by a weight coefficient to obtain an evaluation parameter at a given speed;

[0031] In step 5), the evaluation parameters at different speeds are fitted into a comprehensive evaluation parameter curve, and the comprehensive evaluation parameter curve is compared with the set threshold value to determine whether the intermediate bearing lubricating oil cooling and lubrication effect meets the requirements; specifically, in step 5), the evaluation parameters at different speeds are obtained and the evaluation parameters at different speeds are fitted into a curve, which is the comprehensive evaluation parameter curve. The closer the value of the comprehensive evaluation parameter curve is to 1, the better the cooling and lubrication effect. The set threshold value may be determined according to different situations, for example, 0.9. When the comprehensive evaluation parameter curve is not less than 0.9, it is considered that the intermediate bearing lubricating oil cooling and lubrication effect meets the requirements. You can refer to Figure 6 , a graph of the fitted comprehensive evaluation parameter curve is given.

[0032] Compared to existing technologies, the present invention fully considers the loads and failure modes that each component in the intermediate bearing may receive during operation, can fully characterize the cooling and lubrication effects of the bearing under various operating conditions, and has strong engineering applicability. The present invention takes into account the differences in oil film coverage area on the roller surface due to the different relative positions between the bearing roller and the oil delivery hole of the inner ring of the bearing during operation, making the evaluation results closer to engineering practice. Because the cooling and lubrication effect of the bearing is closely related to its operating speed, the method of the present invention can more easily obtain a curve showing the changes in the comprehensive evaluation parameter curve with the speed, which has important guiding significance for the design of the bearing lubricating oil flow path.

[0033] Furthermore, in step 1), the surface area of ​​the bearing cage includes the area of ​​the outer surface of the cage, the area of ​​the inner surface of the cage, the area of ​​the front surface of the groove, and the area of ​​the rear surface of the groove, and the calculation formula is:

[0034] S c =S co +S ci +S cf +S cb

[0035] Among them, S c is the surface area of ​​the bearing cage, S co is the area of ​​the outer surface of the cage, S ci is the area of ​​the inner surface of the cage, S cf is the area of ​​the front surface of the groove, S cb is the area of ​​the rear surface of the groove.

[0036] Furthermore, in step 2), the following formula is used to calculate the oil recovery coefficient:

[0037]

[0038] Among them, η is the oil collection coefficient, L0 is the total oil supply, and L1 is the amount of lubricating oil that enters the bearing from the oil delivery hole on the inner ring and reaches the bearing roller and bearing cage. Figure 2 ,The three-dimensional fluid model of bearing lubrication was established using commercial CFD software, and the amount of lubricating oil at the outlet of the oil hole of the inner ring of the bearing was obtained.

[0039] Furthermore, in step 3), the oil film coverage of the bearing retainer surface includes the oil film coverage of the outer surface of the bearing retainer C co , Oil film coverage of the inner surface of the bearing cage C ci , Oil film coverage of the front surface of the groove C cf , Oil film coverage of the rear surface of the groove C cb , and the calculation formulas are as follows:

[0040]

[0041] Furthermore, in step 3), the calculation formula for the oil film coverage of the bearing retainer surface is:

[0042] C c =a1×C co +a2×C ci +a3×C cf +a4×C cb

[0043] Among them, C c is the oil film coverage of the bearing cage surface, a1, a2, a3, and a4 are weighting coefficients, and a1 + a2 + a3 + a4 = 1. For example, if the oil film coverage of the cage outer surface, the bearing cage inner surface, the groove front surface, and the groove rear surface are assumed to have the same contribution to the bearing cage surface oil film coverage, then a1 = a2 = a3 = a4 = 0.25 can be taken, and a1 + a2 + a3 + a4 = 1 is satisfied.

[0044] Furthermore, the calculation formula for the oil film coverage of the bearing roller surface is:

[0045]

[0046] Where W is the parameter of the relative position between the bearing roller and the oil delivery hole of the bearing inner ring, C r is the oil film coverage of the bearing roller surface, S r is the surface area of ​​the bearing roller, S ro It is the oil film coverage area of ​​the bearing roller surface.

[0047] Further, refer to Figure 5 , when calculating the parameter W of the relative position between the bearing roller and the oil delivery hole of the bearing inner ring, the following steps are used:

[0048] Step 3.1) Divide the distance between the oil holes of the inner rings of adjacent bearings into four equal parts. Starting from the position directly opposite the oil hole of the inner ring of the bearing, mark the points of equal division as P1, P2, P3, P4, and P5, for a total of five points.

[0049] Step 3.2) By simulation calculation, it is obtained that when a bearing roller is located at five positions P1, P2, P3, P4, and P5, the oil film coverage area S on the surface of the bearing roller is P1 、S P2 、S P3 、S P4 、S P5 ;

[0050] Step 3.3), for the oil film coverage area S obtained in step 3.2) P1 、S P2 、S P3 、S P4 、S P5 , using S obtained in step 3.2) P1 The dimensionless processing is performed to compare the relative size of the oil film coverage area of ​​the roller surface at different positions, and the dimensionless oil film coverage area C of the bearing roller surface is obtained. P1 、C P2 、C P3 、C P4 、C P5 , the calculation formula for the dimensionless roller surface oil film coverage area is:

[0051]

[0052] Step 3.4) is to calculate the dimensionless oil film coverage area C of the roller surface obtained in step 3.3) P1 、C P2 、C P3 、C P4 、C P5 , take the average value to get the parameter W that characterizes the relative position of the bearing roller and the oil delivery hole of the bearing inner ring. The calculation formula is:

[0053]

[0054] Furthermore, in step 4), the calculation formula of the evaluation parameter is:

[0055] E i =(A1×C r +A2×C c )×η

[0056] Among them, V i is a given speed, E i To evaluate the parameters, C ris the oil film coverage of the bearing roller surface, C c is the oil film coverage on the bearing cage surface, η is the oil collection coefficient, A1 and A2 are weighting coefficients, and A1 + A2 = 1. For example, if the oil film coverage on the roller surface and the oil film coverage on the bearing cage surface are assumed to have the same contribution to the bearing lubrication effect, then A1 = A2 = 0.5, and A1 + A2 = 1 can be satisfied.

[0057] The embodiments described above are merely descriptions of preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Without departing from the spirit of the present invention, various deformations, modifications, and substitutions made to the technical solutions of the present invention by ordinary technicians in this field should fall within the scope of protection determined by the claims of the present invention.

Claims

1. A method for evaluating the cooling and lubricating effect of lubricating oil in an intermediate bearing of an aircraft engine, characterized in that: The following steps are involved: Step 1), based on a given intermediate bearing, calculate the surface area of ​​the bearing roller and the surface area of ​​the bearing cage; Step 2) obtaining the oil film coverage area of ​​the bearing roller surface, the oil film coverage area of ​​the bearing cage surface, and the oil collection coefficient at a given speed through simulation calculation; Step 3), calculating the oil film coverage rate of the bearing cage surface at a given speed by using the surface area of ​​the bearing cage and the oil film coverage area of ​​the bearing cage surface, and calculating the oil film coverage rate of the bearing roller surface at a given speed by using the surface area of ​​the bearing roller and the oil film coverage area of ​​the bearing roller surface; Step 4) The oil collection coefficient, the oil film coverage rate of the bearing roller surface, and the oil film coverage rate of the bearing cage surface are weighted by a weight coefficient to obtain an evaluation parameter at a given speed; Step 5) fitting the evaluation parameters at different speeds into a comprehensive evaluation parameter curve, and comparing the comprehensive evaluation parameter curve with a set threshold to determine whether the intermediate bearing oil cooling and lubrication effect meets the requirements within the operating speed range; In step 2), the following formula is used to calculate the oil recovery coefficient: Where η is the oil collection coefficient, L0 is the total oil supply, and L1 is the amount of lubricating oil that enters the bearing from the oil delivery hole on the inner ring and reaches the bearing rollers and bearing cage. The calculation formula for the oil film coverage of the bearing roller surface is: Where W is the parameter of the relative position between the bearing roller and the oil delivery hole of the bearing inner ring, C r is the oil film coverage of the bearing roller surface, S r is the surface area of ​​the bearing roller, S ro is the oil film coverage area on the bearing roller surface; To calculate the parameter W for the relative position of the bearing roller and the oil delivery hole of the bearing inner ring, use the following steps: Step 3.1) Divide the distance between the oil holes of the inner rings of adjacent bearings into four equal parts. Starting from the position directly opposite the oil hole of the inner ring of the bearing, mark the points of equal division as P1, P2, P3, P4, and P5, for a total of five points. Step 3.2) By simulation calculation, it is obtained that when a bearing roller is located at five positions P1, P2, P3, P4, and P5, the oil film coverage area S on the surface of the bearing roller is P1 、S P2 、S P3 、S P4 、S P5 ; Step 3.3), for the oil film coverage area S obtained in step 3.2) P1 、S P2 、S P3 、S P4 、S P5 , using S obtained in step 3.2) P1 Perform dimensionless processing to obtain the dimensionless oil film coverage area C of the bearing roller surface P1 、C P2 、C P3 、C P4 、C P5 , the calculation formula for the dimensionless roller surface oil film coverage area is: Step 3.4) is to calculate the dimensionless oil film coverage area C of the roller surface obtained in step 3.3) P1 、C P2 、C P3 、C P4 、C P5 , take the average value to get the parameter W that characterizes the relative position of the bearing roller and the oil delivery hole of the bearing inner ring. The calculation formula is: In step 4), the calculation formula of the evaluation parameter is: AND i =(A1×C r +A2×C c )×η Among them, V i is a given speed, E i To evaluate the parameters, C r is the oil film coverage of the bearing roller surface, C c is the oil film coverage of the bearing cage surface, η is the oil collection coefficient, A1 and A2 are weight coefficients, and A1+A2=1.

2. The method for evaluating the cooling and lubricating effect of lubricating oil in an aircraft engine intermediate bearing according to claim 1, characterized in that: In step 1), the surface area of ​​the bearing cage includes the area of ​​the outer surface of the cage, the area of ​​the inner surface of the cage, the area of ​​the front surface of the groove, and the area of ​​the rear surface of the groove, and the calculation formula is: S c =S co +S ci +S cf +S cb Among them, S c is the surface area of ​​the bearing cage, S co is the area of ​​the outer surface of the cage, S ci is the area of ​​the inner surface of the cage, S cf is the area of ​​the front surface of the groove, S cb is the area of ​​the rear surface of the groove.

3. The method for evaluating the cooling and lubricating effect of lubricating oil in an aircraft engine intermediate bearing according to claim 2, characterized in that: In the step 3), the oil film coverage of the bearing cage surface includes the oil film coverage of the outer surface of the bearing cage C co , Oil film coverage of the inner surface of the bearing cage C ci , Oil film coverage of the front surface of the groove C cf , Oil film coverage of the rear surface of the groove C cb , and the calculation formulas are as follows:

4. The method for evaluating the cooling and lubricating effect of lubricating oil in an aircraft engine intermediate bearing according to claim 3, characterized in that: In step 3), the calculation formula for the oil film coverage of the bearing cage surface is: C c =a1×C co +a2×C ci +a3×C cf +a4×C cb Among them, C c is the oil film coverage of the bearing cage surface, a1, a2, a3, a4 are weight coefficients, and a1+a2+a3+a4=1.

5. The method for evaluating the cooling and lubricating effect of lubricating oil in an aircraft engine intermediate bearing according to claim 1, characterized in that: By obtaining evaluation parameters at different rotational speeds, the evaluation parameters at different rotational speeds are fitted into a curve, which is a comprehensive evaluation parameter curve.

6. The method for evaluating the cooling and lubricating effect of lubricating oil in an aircraft engine intermediate bearing according to claim 5, characterized in that: The closer the value of the comprehensive evaluation parameter curve is to 1, the better the cooling and lubrication effect is.

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