Design method of return oil gas suction and separation device of lubricating oil system of aero-engine

Abstract

The invention belongs to the technical field of aero-engine lubricating oil, and discloses a design method of an aero-engine lubricating oil system oil return oil-gas suction separation device, which comprises the following steps of: firstly, calculating the volume Q1 of lubricating oil in an oil-gas mixture, calculating the volume Q2 of air in the oil-gas mixture, and selecting the displacement of a liquid ring pump according to the volume of the air; calculating the pressure distribution of a liquid ring in the liquid ring pump along the radial direction; according to the selected liquid ring pump, determining the liquid ring width value of the liquid ring pump for maintaining the liquid ring seal to the minimum; calculating the positions of small oil discharge holes in the pump; calculating the sizes and the number of the small oil discharge holes in the pump, iterating the displacement of the liquid ring pump, and checking whether the pressure of an exhaust outlet of the liquid ring pump is proper or not; judging whether iteration continues calculation or not; and after iteration is completed, basic design calculation of the separation device is completed. The oil return pump and oil-gas separation integrated design requirement can be met, the oil-gas pumping function and the oil-gas separation function are achieved at the same time, compared with a traditional gear pump scheme, the higher inlet vacuum degree can be provided, the requirement for the higher rotating speed can be met, and the mass and size of an oil return system are effectively reduced.

Description

Technical Field

[0001] The invention belongs to the technical field of aircraft engine lubricating oil, and relates to a design method of an oil-gas separation device, and specifically to a design method of an oil-gas suction separation device for an aircraft engine lubricating oil system return oil. Background Art

[0002] The oil return system of aircraft engines usually includes an oil return pump, an oil-gas separator and other devices. Such products are usually completed by two independent functional components with a low degree of integration. In particular, the oil return pump usually has a low speed and is prone to wear during operation.

[0003] Traditional positive displacement pumps such as gear pumps usually have an operating speed below 12,000 rpm and a short service life. Oil-gas separation usually uses a centrifugal oil-gas separation device with a higher speed, and uses two devices to achieve the oil return system and oil-gas separation functions. Usually, the vacuum pumping capacity of the gear pump is weak, and the oil return system often fails to return oil smoothly. The oil-gas separator has a certain flow resistance, which affects the oil return system when the ventilation volume is large, resulting in a decrease in the performance of the oil return pump. Summary of the invention

[0004] In order to solve the above problems, the present invention proposes a design method for an oil return oil and gas suction and separation device of an aircraft engine lubricating oil system, which can meet the needs of the integrated design of the oil return pump and the oil and gas separation, and realize the oil and gas pumping function and the oil and gas separation function at the same time. Compared with the traditional gear pump solution, this structure can provide a higher inlet vacuum degree, adapt to higher speed requirements, and effectively reduce the mass and volume of the oil return system.

[0005] The technical solution of the present invention is as follows:

[0006] A design method for an oil-gas suction and separation device for an aircraft engine lubricating oil system includes the following steps:

[0007] S1: Calculate the lubricating oil volume Q1 in the oil-air mixture;

[0008] S2: Calculate the air volume Q2 in the oil-gas mixture;

[0009] S3: Select the displacement of the liquid ring pump according to the air volume;

[0010] S4: Calculate the pressure distribution of the liquid ring in the liquid ring pump along the radial direction;

[0011] S5: According to the selected liquid ring pump, determine the minimum liquid ring width value of the liquid ring pump for maintaining the liquid ring seal;

[0012] S6: Calculate the position of the oil discharge hole on the pump;

[0013] S7: Calculate the size and number of the oil discharge holes on the pump;

[0014] S8: Iterate the displacement of the liquid ring pump in step 3, check whether the exhaust outlet pressure of the liquid ring pump is appropriate, and determine whether to continue the calculation iteratively; when the iteration is completed, the basic design calculation of the separation device is completed.

[0015] Furthermore, in S1 and S2,

[0016]

[0017] Among them, the oil return volume demand of the oil return system is Q, unit: L / min, and the oil to gas volume ratio is m:t.

[0018] Furthermore, in S3, the displacement of the device is selected according to the gas flow rate, and the displacement formula is q=q(r), wherein Q2=q is selected during selection, and q(r) is determined according to the flow function of the vane pump.

[0019] Furthermore, in S4, the pressure values ​​at various locations of the liquid ring in the liquid ring pump are:

[0020] P R =P0-(P0-P1)F(x)

[0021] Where: P R is the pressure value at any point of the liquid ring, P0 is the pressure value at the minimum pressure of the liquid ring, P1 is the pressure value at the maximum pressure of the liquid ring, F(x) is the liquid ring pressure distribution function, and F(x) is obtained by empirical formula or CFD simulation.

[0022] Furthermore, in S5, the minimum liquid ring width of the liquid ring pump to maintain the liquid ring seal is:

[0023] e0=Kδ

[0024] Where K is the liquid ring thickness coefficient, and δ is the minimum gap between the liquid ring blade and the shell.

[0025] Furthermore, in S6, the minimum distance between the small hole and the pump axis is calculated first, and the relationship between flow rate and displacement is obtained:

[0026]

[0027] Arranged:

[0028] The distribution position and size of the small holes are controlled within r x In the range of (r-e0),

[0029] Among them, r is the vane pump diameter and h is the vane pump height.

[0030] Further, in S7, according to the small hole flow formula, the flow formula of the thin-walled small hole is selected for calculation, and the ratio of the thin-walled small hole length l to the small hole diameter d is

[0031] At this time, the small hole flow formula is:

[0032]

[0033] Where C is the cross-sectional shrinkage coefficient, C V is the velocity coefficient of the small hole, Δp is the pressure difference before and after the small hole;

[0034] Where Δp=P R -P c

[0035] P c is the small hole lubricating oil outlet pressure value,

[0036] q=nq0

[0037] n is the number of small holes, and q0 is the lubricating oil flow rate of a single small hole.

[0038] Furthermore, in S8, according to the position of the small hole, the minimum width value of the sealing liquid ring is determined, which is the maximum distance between the outer diameter of the small hole and the center of the impeller. The liquid ring pressure value here is obtained according to S4. The calculated liquid ring pressure value must be equal to P0, or the error with P0 is less than a certain value; otherwise, the displacement parameters are adjusted in S3 and the iterative calculation is performed again.

[0039] The beneficial effects of the present invention are as follows:

[0040] The return oil and gas suction and separation device designed in the present invention can meet the needs of the integrated design of the return oil pump and the oil and gas separation, and realize the oil and gas pumping function and the oil and gas separation function at the same time. Compared with the traditional gear pump solution, this structure can provide a higher inlet vacuum degree, adapt to higher speed requirements, and effectively reduce the mass and volume of the return oil system. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings required for describing the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other accompanying drawings can be obtained based on these accompanying drawings without paying creative work.

[0042] Figure 1 It is a schematic diagram of the design method principle of the present invention. DETAILED DESCRIPTION

[0043] This section is an embodiment of the present invention, which is used to explain and illustrate the technical solution of the present invention. In the absence of conflict, the embodiments of the present invention and the features in the embodiments can be combined with each other.

[0044] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside" and the like indicate directions or positional relationships based on the orientations or positional relationships in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or case referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention. In addition, the terms "first", "second", etc. are used for descriptive purposes only, and cannot be understood as indicating or implying relative importance or implying the number of technical features indicated. Thus, features defined as "first", "second", etc. may explicitly or implicitly include more of the features. In the description of the present invention, unless otherwise specified, "multiple" means two or more.

[0045] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected" and "connected" should be interpreted in a broad sense, for example, it can be a fixed connection, a detachable connection or an integrated connection; it can be a mechanical connection or a point connection; it can be a direct connection or an indirect connection through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood by specific circumstances.

[0046] Embodiment 1:

[0047] A design method for an oil-gas suction and separation device for an aircraft engine lubricating oil system includes the following steps:

[0048] S1: Calculate the lubricating oil volume Q1 in the oil-air mixture;

[0049] S2: Calculate the air volume Q2 in the oil-gas mixture;

[0050] S3: Select the displacement of the liquid ring pump according to the air volume;

[0051] S4: Calculate the pressure distribution of the liquid ring in the liquid ring pump along the radial direction;

[0052] S5: According to the selected liquid ring pump, determine the minimum liquid ring width value of the liquid ring pump for maintaining the liquid ring seal;

[0053] S6: Calculate the position of the oil discharge hole on the pump;

[0054] S7: Calculate the size and number of the oil discharge holes on the pump;

[0055] S8: Iterate the displacement of the liquid ring pump in step 3, check whether the exhaust outlet pressure of the liquid ring pump is appropriate, and determine whether to continue the calculation iteratively; when the iteration is completed, the basic design calculation of the separation device is completed.

[0056] In S1 and S2,

[0057]

[0058] Among them, the oil return volume demand of the oil return system is Q, unit: L / min, and the oil to gas volume ratio is m:t.

[0059] In S3, the displacement of the device is selected according to the gas flow rate, and the displacement formula is q=q(r), wherein Q2=q is selected during selection, and q(r) is determined according to the flow function of the vane pump.

[0060] In S4, the pressure values ​​at various locations of the liquid ring in the liquid ring pump are:

[0061] P R =P0-(P0-P1)F(x)

[0062] Where: P R is the pressure value at any point of the liquid ring, P0 is the pressure value at the minimum pressure of the liquid ring, P1 is the pressure value at the maximum pressure of the liquid ring, F(x) is the liquid ring pressure distribution function, and F(x) is obtained by empirical formula or CFD simulation.

[0063] In S5, the minimum liquid ring width of the liquid ring pump to maintain the liquid ring seal is:

[0064] e0=Kδ

[0065] Where K is the liquid ring thickness coefficient, and δ is the minimum gap between the liquid ring blade and the shell.

[0066] In S6, the minimum distance between the small hole and the pump axis is calculated first, and the relationship between flow rate and displacement is obtained:

[0067]

[0068] Arranged:

[0069] The distribution position and size of the small holes are controlled within r x In the range of (r-e0),

[0070] Among them, r is the vane pump diameter and h is the vane pump height.

[0071] In S7, according to the small hole flow formula, the flow formula of thin-walled small holes is selected for calculation. The ratio of the length l of the thin-walled small hole to the diameter d of the small hole is

[0072] At this time, the small hole flow formula is:

[0073]

[0074] Where C is the cross-sectional shrinkage coefficient, C V is the velocity coefficient of the small hole, Δp is the pressure difference before and after the small hole;

[0075] Where Δp=P R -P c

[0076] P c is the small hole lubricating oil outlet pressure value,

[0077] q=nq0

[0078] n is the number of small holes, and q0 is the lubricating oil flow rate of a single small hole.

[0079] In S8, the minimum width of the sealing liquid ring is determined according to the position of the small hole, which is the maximum distance between the outer diameter of the small hole and the center of the impeller. The liquid ring pressure value here is obtained according to S4. The calculated liquid ring pressure value must be equal to P0, or the error with P0 is less than a certain value; otherwise, the displacement parameters are adjusted in S3 and the iterative calculation is repeated.

[0080] Embodiment 2:

[0081] The principle of this method is to use a blade with vacuum pumping capability to draw back the oil-gas mixture from the engine lubricating oil system. While drawing back, the oil-gas mixture moves to the outer ring under the action of centrifugal force and merges into the liquid ring, while the air gathers and compresses on the inner side and is discharged through the outlet. A suitable oil drain hole is designed on the side of the liquid ring close to the axis to discharge the oil gathered in the liquid ring, thereby achieving the functions of oil-gas separation and oil withdrawal at the same time. The present invention provides a method for rationally designing the structure.

[0082] The oil return volume requirement of the oil return system is Q (unit: L / min), where the oil to gas volume ratio is m:t (dimensionless)

[0083] Step 1: Calculate the volume of oil required for oil return

[0084] Step 2: Calculate the volume of air in the return oil

[0085] Step 3: Select the displacement of the device according to the gas flow rate. The displacement formula is q = q (r)

[0086] When selecting, select Q2 = q, q (x) is determined according to the flow function of the vane pump (simulation or based on empirical formula)

[0087] Step 4: Calculate the pressure values ​​at various locations of the liquid ring in the liquid ring pump:

[0088] The pressure value of each part of the liquid ring in the liquid ring pump is: P R =P0-(P0-P1)F(x)

[0089] Where: P R is the pressure value at any point of the liquid ring, P0 is the pressure value at the minimum pressure of the liquid ring, P1 is the pressure value at the maximum pressure of the liquid ring, and F(x) is the liquid ring pressure distribution function (which can be obtained by empirical formula or by CFD simulation based on the characteristics of the liquid ring pump)

[0090] Step 5: According to the selected liquid ring pump, determine the minimum liquid ring width value of the liquid ring pump to maintain the liquid ring seal

[0091] e0=Kδ

[0092] Where K is the liquid ring thickness coefficient, which is selected empirically and usually has a value between 0.1 and 0.2, and δ is the minimum gap between the liquid ring blade and the shell.

[0093] Step 6: Calculate the location of the oil drain hole.

[0094] Calculate the minimum distance between the small hole and the pump axis

[0095] According to the relationship between flow rate and displacement,

[0096] Arranged:

[0097] Then the distribution position and size of the small holes need to be controlled within r x In the range of (r-e0),

[0098] Where r is the diameter of the vane pump, h is the height of the vane pump,

[0099] Step 7: Determine the size and number of lubricating oil holes.

[0100] According to the orifice flow rate;

[0101] According to the small hole flow formula (see "Mechanical Design Manual")

[0102] Select the flow formula of thin-walled small holes for calculation, the ratio of the hole length l of the thin-walled small hole to the hole diameter d

[0103] At this time, the small hole flow formula is: Where C is the cross-sectional shrinkage coefficient, C V is the velocity coefficient of the small hole, and Δp is the pressure difference before and after the small hole.

[0104] Where ΔP = P R -P c

[0105] Where P c It is the small hole lubricating oil outlet pressure value.

[0106] q=nq0

[0107] n is the number of small holes, q0 is the oil flow rate of a single small hole

[0108] Step 8: Determine the vane pump exhaust outlet pressure value.

[0109] According to the position of the small hole, determine the minimum width of the sealing liquid ring, which is the maximum distance between the outer diameter of the small hole and the center of the impeller. According to the formula P in 4 R =P0-(P0-P1)F(x) can tell the liquid ring pressure value at this time. The calculated liquid ring pressure value must be equal to P0, or the error with P0 is acceptable. Otherwise, adjust P0 in step 3 and re-calculate the design.

[0110] Step 9: When the calculated value of P0 is acceptable, complete the basic design calculation of the device.

[0111] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the field can easily think of various equivalent modifications or substitutions within the technical scope disclosed by the present invention, and these modifications or substitutions should all be covered within the protection scope of the present invention.

Claims

1. A design method for an oil-gas suction and separation device for an aircraft engine lubricating oil system, characterized in that: The following steps are involved: S1: Calculate the lubricating oil volume Q1 in the oil-air mixture; S2: Calculate the air volume Q2 in the oil-gas mixture; S3: Select the displacement of the liquid ring pump according to the air volume; S4: Calculate the pressure distribution of the liquid ring in the liquid ring pump along the radial direction; S5: According to the selected liquid ring pump, determine the minimum liquid ring width value of the liquid ring pump for maintaining the liquid ring seal; S6: Calculate the position of the oil discharge hole on the pump; S7: Calculate the size and number of the oil discharge holes on the pump; S8: Iterate the displacement of the liquid ring pump in step 3, check whether the exhaust outlet pressure of the liquid ring pump is appropriate, and determine whether to continue the calculation iteratively; when the iteration is completed, the basic design calculation of the separation device is completed.

2. The design method of an oil-gas suction and separation device for an aircraft engine lubricating oil system according to claim 1 is characterized in that: In S1 and S2, Among them, the oil return volume demand of the oil return system is Q, unit: L / min, and the oil to gas volume ratio is m:t.

3. The design method of an oil-gas suction separation device for an aircraft engine lubricating oil system according to claim 1 is characterized in that: In S3, the displacement of the device is selected according to the gas flow rate, and the displacement formula is q=q(r), wherein Q2=q is selected during selection, and q(r) is determined according to the flow function of the vane pump.

4. The design method of an oil-gas suction separation device for an aircraft engine lubricating oil system according to claim 1 is characterized in that: In S4, the pressure values ​​at various locations of the liquid ring in the liquid ring pump are: P R =P0-(P0-P1)F(x) Where: P R is the pressure value at any point of the liquid ring, P0 is the pressure value at the minimum pressure of the liquid ring, P1 is the pressure value at the maximum pressure of the liquid ring, F(x) is the liquid ring pressure distribution function, and F(x) is obtained by empirical formula or CFD simulation.

5. The design method of an oil-gas suction separation device for an aircraft engine lubricating oil system according to claim 1, characterized in that: In S5, the minimum liquid ring width of the liquid ring pump to maintain the liquid ring seal is: e0=Kδ Where K is the liquid ring thickness coefficient, and δ is the minimum gap between the liquid ring blade and the shell.

6. The design method of an oil-gas suction and separation device for an aircraft engine lubricating oil system according to claim 5 is characterized in that: In S6, the minimum distance between the small hole and the pump axis is calculated first, and the relationship between flow rate and displacement is obtained: Arranged: The distribution position and size of the small holes are controlled within r x In the range of (r-e0), Among them, r is the vane pump diameter and h is the vane pump height.

7. The design method of an oil-gas suction and separation device for an aircraft engine lubricating oil system according to claim 1, characterized in that: In S7, according to the small hole flow formula, the flow formula of thin-walled small holes is selected for calculation. The ratio of the length l of the thin-walled small hole to the diameter d of the small hole is At this time, the small hole flow formula is: Where C is the cross-sectional shrinkage coefficient, C V is the velocity coefficient of the small hole, Δp is the pressure difference before and after the small hole; Where Δp=P R -P c P c is the small hole lubricating oil outlet pressure value, q=nq0 n is the number of small holes, q0 is the lubricating oil flow rate of a single small hole, and the number of small holes n is calculated.

8. The design method of an oil-gas suction and separation device for an aircraft engine lubricating oil system according to claim 4 is characterized in that: In S8, the minimum width of the sealing liquid ring is determined according to the position of the small hole, which is the maximum distance between the outer diameter of the small hole and the center of the impeller. The liquid ring pressure value here is obtained according to S4. The calculated liquid ring pressure value must be equal to P0, or the error with P0 is less than a certain value; otherwise, the displacement is adjusted in S3 and the iterative calculation is repeated.

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