Method for calculating circulating oil volume of reciprocating piston compressor body lubrication system

Abstract

This invention provides a method for calculating and analyzing the circulating oil volume of a reciprocating piston compressor's lubrication system. This includes calculating the compressor bearing load, the theoretical bearing oil supply flow rate, the corrected bearing oil supply flow rate, and the circulating oil volume. It can accurately calculate the amount of oil required for complete lubrication of each bearing, providing crucial circulating oil flow rate parameters for lubrication system design. The accurate selection of these parameters directly affects the specifications of components such as the oil pump, oil filter, and oil cooler in the lubrication system. Precise calculations can effectively reduce the circulating oil volume of the lubrication system, allowing for the design of a reasonable oil supply system, thereby reducing the production and operating costs of the lubrication system and minimizing resource waste.

Description

Technical Field

[0001] This invention relates to the technical field of compressor lubrication systems, and specifically to a method for calculating and analyzing the circulating oil volume of a reciprocating piston compressor body lubrication system. Background Technology

[0002] The lubrication system is a crucial system for ensuring the normal operation of a reciprocating piston compressor. Good lubrication effectively reduces wear on friction pairs and lowers the operating temperature of components. The lubrication system of a reciprocating compressor mainly lubricates and cools various bearings, including the main bearings, crankshaft bearings, connecting rod bearings, and crosshead bearings. It generally employs a circulating lubrication system: the oil pump draws lubricating oil from the oil tank, which, after cooling and filtration, enters the main oil passage. It then enters the main bearings through the main oil port to begin lubricating them, followed by the crankshaft bearings through the oil port. The lubricating oil then flows to the connecting rod large and small end bearings, and finally returns to the oil tank through the crosshead slide, completing the cycle. The domestic guidebook for reciprocating piston compressor design, "Design of Piston Compressors," uses empirical estimations to calculate the circulating oil volume.

[0003]

[0004] In the formula, N represents the compressor shaft power (kW).

[0005] γ-Specific gravity of lubricating oil (kg / L);

[0006] c - Specific heat of lubricating oil;

[0007] η m - Compressor mechanical efficiency: 0.9–0.95;

[0008] Δt - Lubricating oil temperature rise (°C), taken as: 15~20°C;

[0009] The above formula does not fully evaluate the factors affecting the flow rate of lubricating oil, and the calculated circulating oil volume deviates greatly due to different coefficient selections.

[0010] The circulating oil volume of a reciprocating compressor's lubrication system primarily depends on the required lubrication volume of bearings such as the crankshaft and connecting rod. Key factors influencing the circulating oil volume include shaft diameter, bearing clearance, bearing load, oil supply pressure, rotational speed, and axial motion. Insufficient circulating oil leads to inadequate lubrication of the friction pairs, increased wear on components, a rapid temperature rise, and ultimately, bearing erosion, causing compressor failure and shutdown. Conversely, excessive circulating oil increases bearing end leakage, reducing bearing load capacity and wasting resources. Due to the complexity of bearing oil supply and the factors affecting bearing tribological properties, accurately calculating the circulating oil volume of the lubrication system is difficult. In engineering practice, designers often rely on experience and select large margins, resulting in the selected shaft pump and / or external oil pump supplying a much larger volume than theoretically required. This leads to energy loss in the system and increases the design, manufacturing, and operating costs of the lubrication system. Therefore, accurate analysis and calculation of the lubrication system's oil supply volume are essential. Summary of the Invention

[0011] The main objective of this invention is to provide a method for calculating and analyzing the circulating oil volume of a reciprocating piston compressor's lubrication system. When the calculation formula for the circulating oil volume of a reciprocating piston compressor's lubrication system has a large deviation, it leads to a larger overall size and energy consumption of the lubrication system, resulting in a certain degree of resource waste. Only by accurately calculating the circulating oil volume of the lubrication system and obtaining the actual oil supply required by each bearing can accurate data on oil flow rate be provided for the selection of oil pumps, oil filters, oil coolers, etc., in the lubrication system, thereby improving the accuracy and reliability of the design.

[0012] To solve the above-mentioned technical problems, the technical solution adopted by the present invention includes: calculating the compressor bearing load, calculating the theoretical oil supply flow rate of the bearing, calculating the corrected oil supply flow rate of the bearing, and calculating the circulating oil volume, with the following steps:

[0013] S1. Analyze and calculate the load characteristics of each bearing in the compressor;

[0014] S2. Calculate the theoretical oil supply of each bearing using theoretical formulas;

[0015] S3. Calculate the oil distribution of lubricating oil at the bearing end and the next branch using the equivalent distribution method, and correct the actual oil leakage at both ends of the bearing.

[0016] S4. Based on the principle of circulating lubrication, find the maximum theoretical oil supply of each bearing, and then take into account the correction of other bearings to obtain the sum of the actual oil leakage at both ends of the bearing. This gives the circulating oil volume of the compressor lubrication system. Finally, check whether each bearing meets the conditions for sufficient lubrication.

[0017] In the preferred scheme, the specific analysis and calculation steps for S1 are as follows:

[0018] A1. Based on the performance calculation sheet of the reciprocating compressor, obtain the curves of the load of each bearing of the compressor as a function of the crankshaft angle, and obtain the maximum load of each bearing.

[0019] A2. When analyzing and calculating the full lubricating oil flow rate of each bearing, the bearing load F is calculated using the maximum load.

[0020] A3. When it is difficult to obtain performance calculation sheets or the bearing load is unknown, the maximum rod load of the compressor can be directly selected as the load of each bearing for calculating the oil supply.

[0021] In the preferred embodiment, the lubricating oil entering the bearing forms a lubricating oil film that separates the sliding surfaces. The pressure formed in the lubricating oil film forces the lubricating oil to flow out from both ends of the bearing. The lubricating oil flow rate Q3 caused by the hydrodynamic pressure is a part of Q.

[0022]

[0023] ψ eff —The effective average relative clearance of the bearing;

[0024] ωh — equivalent angular velocity;

[0025] Flow coefficient.

[0026] In the preferred embodiment, the inlet pressure P causes excess lubricating oil to flow out from both ends of the bearing, and the lubricating oil flow rate generated by the inlet pressure is Q. p :

[0027]

[0028] ψ eff —The effective average relative clearance of the bearing;

[0029] η eff —Equivalent dynamic viscosity of lubricating oil;

[0030] Flow coefficient;

[0031] Theoretical lubricating oil flow rate of bearings in reciprocating piston compressors

[0032] Q = Q³ + Q p (4)

[0033] In the preferred embodiment, the reciprocating piston compressor uses a circulating oil circuit. Except for the lubrication point of the end crosshead bearing, each bearing is provided with an oil hole leading to the next lubrication point. Under the action of the oil supply pressure P and the sliding fluid dynamic pressure, the amount of lubricating oil Q entering the circumferential oil groove of the bearing will be divided into two parts. One part is discharged into the crankcase oil sump at both ends of the bearing, and the other part is transmitted to the next bearing through the oil hole and oil passage.

[0034] In the preferred scheme, the flow distribution from the main pipeline to each branch pipeline is related to the pressure resistance of each branch pipeline. The higher the pressure resistance, the smaller the flow distribution. For a pipeline, the pressure resistance is proportional to the fourth power of its diameter. The gap area between the bearing and the bushing can be equivalent to a diameter of d. Ψ The area of ​​the drain hole, i.e.:

[0035]

[0036] In the formula:

[0037] ψ — Relative average of bearings;

[0038] The flow rate Q of lubricating oil entering the bearing circumferential oil groove is partially discharged into the crankcase and partially enters the next oil hole, with a distribution coefficient χ:

[0039] make

[0040] In the formula:

[0041] d Ψ —Equivalent end vent diameter;

[0042] d o —Diameter of the oil hole;

[0043]

[0044] Q f —The actual amount of oil released from both ends of the bearing into the crankcase.

[0045] In the preferred scheme, find the maximum theoretical lubricating oil flow rate Q for each bearing. max Add the remaining oil Q that actually leaks from both ends of the bearing into the crankcase. f1 Q f2 ..., which is the oil supply Q of a certain column of the compressor. L :

[0046] Q L =Q max +Q f1 +Q f2 +... (8)

[0047] Verification analysis, let the oil supply to each bearing be Q. Ci, where i represents the bearing sequence on a certain column of the oil supply line;

[0048] Q C1 =Q L (9)

[0049] Q Gi =Q G(i-1) -Q f(i-1) (i>2) (10)

[0050] The oil supply Q to each bearing in this lubrication circuit Gi All can exceed their theoretical end discharge flow rate Q i (i.e. Q) Gi Q i This indicates that the bearing is adequately lubricated.

[0051] In the preferred embodiment, the oil supply Q of the other columns of the reciprocating compressor LN (N=1,2,3...) can all be calculated according to the above formula. Therefore, for a reciprocating compressor with n columns, the circulating oil volume of its lubrication system is the sum of the oil supply volume of each column.

[0052] Considering that the required lubricating oil flow at the crosshead slide of the compressor is relatively small, it is generally considered together with the safety margin, that is, the flow rate is increased by 20% based on the original calculated lubricating oil volume;

[0053] Therefore, for the circulating oil quantity Q of the lubrication system of an n-row reciprocating compressor z That is:

[0054] Q z =1.2*(Q) L1 +Q L2 +Q L3 +...). (11)

[0055] This invention provides a method for calculating and analyzing the circulating oil volume of a reciprocating piston compressor's lubrication system, with the following advantages:

[0056] 1. By fully considering the impact of factors such as the load, size, and oil supply pressure of each compressor bearing on the oil supply of each bearing, the accuracy of the calculation of the circulating oil volume of the lubrication system is improved.

[0057] 2. The area of ​​the gap between the bearing and the bushing on both sides is equivalent to a diameter d. Ψ The area of ​​the end drain hole is given. Based on the bearing oil supply, the flow distribution of the equivalent end drain hole and oil hole is proportional to the fourth power of its diameter. The actual end drain flow rate of the bearing leaking from the equivalent end drain hole is calculated.

[0058] 3. It can effectively ensure that all bearings of the compressor can meet the conditions of full lubrication under various operating conditions, and avoid bearing failures caused by insufficient lubrication.

[0059] 4. The circulating oil volume of the lubrication system calculated by this method is more accurate than that of the original design, which can reduce the circulating oil volume, thereby reducing the energy consumption of the lubrication system and saving production costs. Attached Figure Description

[0060] The present invention will be further described below with reference to the accompanying drawings and embodiments:

[0061] Figure 1 This is a schematic diagram of the circulating oil volume of the compressor lubrication system of the present invention;

[0062] Figure 2 This is a schematic diagram of the flow distribution between the bearing equivalent end drain hole and the oil hole in this invention; Detailed Implementation

[0063] Example 1

[0064] like Figures 1-2 As shown, the calculation and analysis method for the circulating oil volume of the reciprocating piston compressor body lubrication system, and the calculation of compressor bearing load are as follows:

[0065] Based on the performance calculation report of the reciprocating compressor, the load variation curves of each bearing in a certain series of crankshaft main bearings, connecting rod big end bearings, and connecting rod small end bearings as a function of crankshaft rotation angle are obtained, and the maximum load of each bearing is identified. In subsequent calculations, if a bearing can meet the sufficient lubrication condition under maximum load, then the same bearing can also meet the sufficient lubrication condition under other loads below maximum load. Therefore, when analyzing and calculating the full lubricating oil flow rate of each bearing, the bearing load F can be directly selected as the maximum load for calculation.

[0066] In the preferred scheme, since the bearing load has a relatively small impact on the final oil supply, when it is difficult to obtain the performance calculation sheet or the bearing load is unknown, the maximum rod load of the compressor can be directly selected as the load of each bearing for calculating the oil supply, and the result will be slightly larger.

[0067] Calculate the theoretical lubricating oil flow rate Q of the bearing:

[0068] The lubricating oil entering the bearing forms a lubricating oil film that separates the sliding surfaces. The pressure formed in the lubricating oil film forces the lubricating oil to flow out from both ends of the bearing. The lubricating oil flow rate Q3 caused by the hydrodynamic pressure is a part of Q.

[0069]

[0070] ψ eff —The effective average relative clearance of the bearing;

[0071] ωh — equivalent angular velocity;

[0072] The flow coefficient (dimensionless) is given in GB / T 21466.2.

[0073] After passing through the minimum gap, some of the lubricating oil will enter the pressureless gap along the circumference. However, due to the increased load and the small lubrication gap, this outflow of lubricating oil is negligible.

[0074] The inlet pressure P causes excess lubricating oil to flow out from both ends of the bearing. The lubricating oil flow rate generated by the inlet pressure is Q. p

[0075]

[0076] ψ eff —The effective average relative clearance of the bearing;

[0077] η eff —Equivalent dynamic viscosity of lubricating oil;

[0078] The flow coefficient (dimensionless) is given in GB / T 21466.2.

[0079] Theoretical lubricating oil flow rate Q of bearings in a reciprocating piston compressor

[0080] Q = Q³ + Q p (4)

[0081] Therefore, it is only necessary to find the bearing parameters of the main bearing, connecting rod big end bearing, and connecting rod small end bearing from the compressor design parameters, such as bearing diameter D, width-to-diameter ratio B / D, eccentricity ε, etc. The coefficient value is based on the effective average relative clearance ψ of the bearing. eff Substituting into the above expression, we can obtain the theoretical lubricating oil flow rate Q of each bearing in the reciprocating compressor.

[0082] Calculation of actual oil leakage at both ends of the bearing:

[0083] Reciprocating piston compressors use a circulating oil circuit. Therefore, except for the lubrication point of the final crosshead bearing, each bearing has an oil hole leading to the next lubrication point. Under the action of the oil supply pressure P and the fluid dynamic pressure, the amount of lubricating oil Q entering the circumferential oil groove of the bearing will be divided into two parts. One part will drain into the crankcase oil sump at both ends of the bearing, while the remaining part will be transmitted to the next bearing through the oil holes and oil passages. The flow distribution from the main pipeline to each branch pipeline is related to the pressure resistance of each branch pipeline. The higher the pressure resistance, the smaller the flow distribution. For pipelines, the pressure resistance is proportional to the fourth power of its diameter. For ease of comparison, the gap area between the bearing and the bearing bush can be equivalent to a diameter d. Ψ The area of ​​the drain hole, i.e.

[0084]

[0085] In the formula:

[0086] ψ — Relative average of bearings;

[0087] The flow rate Q of lubricating oil entering the bearing circumferential oil groove is partially discharged into the crankcase and partially enters the next oil hole, with a distribution coefficient of χ.

[0088] make

[0089] In the formula:

[0090] d Ψ —Equivalent end vent diameter;

[0091] d o —Diameter of the oil hole;

[0092]

[0093] Q f —The actual amount of oil released from both ends of the bearing into the crankcase.

[0094] Calculation of circulating oil volume in lubrication system:

[0095] Because a circulating lubrication system is used, the lubricating oil first enters the main bearing, then lubricates the crankshaft bearing, then flows to the connecting rod large and small end bearings, and finally flows back to the oil tank through the crosshead slide. Therefore, it is only necessary to find the maximum theoretical lubricating oil flow rate Q for each bearing. max Add the remaining oil Q that actually leaks from both ends of the bearing into the crankcase. f1 Q f2 ..., which is the oil supply Q of a certain column of the compressor. L :

[0096] Q L =Q max +Q f1 +Q f2 +... (8)

[0097] Verification analysis, let the oil supply to each bearing be Q. Gi , where i represents the bearing sequence on a certain column of the oil supply line.

[0098] Q G1 =Q L (9)

[0099] Q Gi =Q G(i-1) -Q f(i-1) (i>2) (10)

[0100] The oil supply Q to each bearing in this lubrication circuit Gi All can exceed their theoretical end discharge flow rate Q i (i.e. Q) Gi Q i This indicates that the bearing is adequately lubricated.

[0101] Oil supply Q of other columns of the reciprocating compressor LN (N=1,2,3...) can all be calculated using the above formula. Therefore, for a reciprocating compressor with n rows, the circulating oil volume of its lubrication system is the sum of the oil supply volumes of each row. Considering that the required lubricating oil flow at the compressor's crosshead sliding section is relatively small, it is generally considered together with a safety margin, i.e., 20% of the flow rate is added to the original calculated lubricating oil volume. Therefore, the circulating oil volume Q of the lubrication system for an n-row reciprocating compressor is... z That is:

[0102] Q z =1.2*(Q) L1 +Q L2 +Q L3 +...). (11)

[0103] Example 2

[0104] Based on the analytical method provided by the above invention, and in conjunction with the embodiments, the following steps are taken to calculate the circulating oil volume of a lubrication system for a symmetrically balanced reciprocating compressor:

[0105] Step 1: Compressor bearing load calculation:

[0106] Based on the performance calculation of the reciprocating compressor, the relationship between the load of each bearing and the crankshaft rotation angle is obtained, and the maximum load of each bearing is selected as follows.

[0107]

[0108] Step 2: Calculation of theoretical oil supply flow rate for bearings:

[0109] Based on the bearing's maximum load F, bearing diameter D, width-to-diameter ratio B / D, eccentricity ε, and effective average relative clearance ψ... eff Substituting into the above expressions (1) to (4), the theoretical end discharge flow rate Q of each bearing of the reciprocating compressor can be obtained.

[0110]

[0111] Step 3: Calculation of actual oil leakage at both ends of the bearing:

[0112] The results calculated using formulas (1) to (7) are shown in the table below:

[0113]

[0114] Step 4: Calculation of circulating oil volume in the lubrication system:

[0115] As shown in the second step, the theoretical oil supply flow rate of the connecting rod big end bearing in this compressor is the largest, i.e., Q. max =Q2 = 17.57 L / min. Therefore, the theoretical oil supply flow rate of the connecting rod big end bearing is selected and included in the total oil supply. For the crankshaft main bearing and the connecting rod small end bearing, only the actual oil leakage at both ends of the bearing needs to be included, which are Q2 and Q2 respectively. f1 = 4.56 L / min, Q f3 =1.03L / min. Therefore, according to formula (8), the total oil supply to all bearings in the first column is:

[0116] Q A =Q max +Q f1 +Q f3 =23.16L / min

[0117] Verification and analysis: In this lubrication circulation loop, the amount of oil entering the crankshaft main bearing is Q. G1 =Q L The amount of oil Q entering the connecting rod big end bearing G2 =Q L -Q f1 The amount of oil entering the small end bearing of the connecting rod is Q. G3 =Q G2 -Q f2 The condition for a bearing to be fully lubricated is Q. Ci Q i The lubrication results for each bearing are shown in the table below:

[0118]

[0119]

[0120] Since the compressor has a symmetrical balanced structure with two rows, the oil supply of the second row is equal to that of the first row. According to formula (9), the circulating oil volume of the lubrication system of the two-row reciprocating compressor is...

[0121] Q z =1.2*(Q) L1 +Q L2 = 55.58 L / min

[0122] The original design for the circulating oil volume of the lubrication system of this two-stage reciprocating compressor was 87 L / min. After precise calculation using the method of this invention, the volume is reduced to 55.58 L / min, a 36% reduction compared to the original design. With the reduction in circulating oil volume, the specifications of the corresponding oil pump, oil cooler, oil filter, etc., in the lubrication system can be appropriately reduced. Therefore, this method can reduce the overall operating energy consumption of the lubrication system and save production costs.

[0123] The above embodiments are merely preferred technical solutions of the present invention and should not be considered as limitations on the present invention. The scope of protection of the present invention should be limited to the technical solutions described in the claims, including equivalent substitutions of the technical features described in the claims. That is, equivalent substitutions and improvements within this scope are also within the scope of protection of the present invention.

Claims

1. A method for calculating and analyzing the circulating oil volume of the lubrication system of a reciprocating piston compressor, characterized by: The steps are as follows: S1, analyzing and calculating the load characteristics of each bearing of the compressor; S2, calculating the theoretical oil supply of each bearing by using a theoretical formula; S3, analyzing and calculating the oil distribution of the lubricating oil at the bearing shell end leakage and the next branch by using an equivalent distribution method, and correcting the actual leakage at both ends of the bearing; S4, according to the principle of circulating lubrication, finding the maximum value of the theoretical oil supply in each bearing, and then adding the corrected actual leakage at both ends of the bearing to obtain the circulating oil amount of the compressor lubrication system, and finally checking whether each bearing meets the sufficient lubrication condition; D is the bearing diameter. The specific analysis and calculation steps of S1 are as follows: A1, according to the performance calculation book of the reciprocating compressor, obtaining the bearing load curve of the compressor with the crankshaft rotation angle, and obtaining the maximum load of each bearing; A2, in the analysis and calculation of the full lubrication oil flow of each bearing, the bearing load F is selected as the maximum load for calculation; A3, in the case where the performance calculation book cannot be obtained or the bearing load cannot be known, the maximum rod load of the compressor can be directly selected as the load of each bearing for oil supply calculation. The lubricating oil amount of the bearing circumferential oil groove of the reciprocating piston compressor The lubricating oil entering the bearing forms a lubricating oil film separating the sliding surfaces, the pressure built up in the lubricating oil film forcing the lubricating oil to flow out of the bearing at both ends, the lubricating oil flow being caused by the hydrodynamic pressure The amount of lubricating oil for the circumferential oil groove of the bearing A part of: （2）； - the effective average relative gap of the bearing; - equivalent angular velocity; is the dimensionless flow coefficient; In the formula:

2. The method of claim 1, wherein the method further comprises: determining a volume of oil in the oil sump; and determining a volume of oil in the oil reservoir. In the formula: Considering that the lubricating oil flow required at the crosshead slide of the compressor is relatively small, it is generally considered together with the safety margin, that is, 20% flow is added on the basis of the original calculation of the lubricating oil amount; ​ ​ 3. The method of claim 1, wherein the method further comprises: determining a volume of oil in the oil sump; and determining a volume of oil in the oil reservoir. The oil feed pressure p causes excess lubricating oil to flow out of the bearing at both ends, and the flow rate of lubricating oil generated by the oil feed pressure is : （3）； - the effective average relative gap of the bearing; - the kinematic viscosity of the lubricating oil; is the dimensionless flow coefficient; ​ + （4）。 4. The method of claim 1, wherein the method further comprises: determining a volume of oil in the oil sump; and determining a volume of oil in the oil reservoir. Reciprocating piston compressor adopts circulating oil path, in addition to the end crosshead bush lubrication point, each bearing is provided with oil hole to the next lubrication point, under the action of oil supply oil pressure p and sliding fluid dynamic pressure, the amount of lubricating oil entering the bearing circumferential oil groove Will be divided into two parts, one part bearing both ends to the crankcase oil pool, another part through the oil hole and oil channel transmission to the next bearing.

5. The method of claim 4, wherein the method further comprises: determining a volume of oil in the oil sump; and determining a volume of oil in the oil reservoir. The flow distribution from the main pipe to each branch pipe is related to the pressure resistance of each branch pipe, and the greater the pressure resistance, the smaller the flow distribution. For a pipe, the pressure resistance is directly proportional to the fourth power of its diameter. The gap area between the bearing and the bearing bush on both sides is equivalent to the oil leakage hole area with a diameter of , that is: （5）； ​ - bearing relative clearance; The amount of lubricating oil entering the bearing circumferential oil groove , part of which is discharged to the crankcase, and part of which enters the next oil hole, and their distribution coefficients are : Let (6); ​ - equivalent end orifice diameter; - oil hole diameter; （7）； - the amount of oil actually vented from both ends of the bearing to the crankcase.

6. The method of claim 1, wherein the method further comprises: determining a volume of oil in the oil sump; and determining a volume of oil in the oil reservoir. Find the maximum theoretical oil flow for each bearing Add the rest of the oil actually bled from both ends of the bearing to the crankcase This is the oil supply for a certain row of the compressor : （8）； The check analysis is that the oil supply to each bearing is , the bearing sequence on a certain column of oil supply lines; （9）； （10）； wherein ; The amount of oil entering each bearing on the column lubrication circuit All are greater than their theoretical end leakage Indicating that the bearings are fully lubricated.

7. The method of claim 6, wherein the method further comprises: determining a volume of oil in the oil sump; and determining a volume of oil in the oil reservoir. Oil supply amount of other rows of reciprocating compressor , N = 1, 2, 3... can be calculated according to the above formula, so for the number of rows of N reciprocating compressor, the circulating oil amount of its lubrication system is the sum of the oil supply amount of each row; ​ Therefore, for the N-column reciprocating compressor lubrication system, the circulating oil volume That is: （11）。

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