CN116517822B - Compressor state monitoring platform and leakage fault diagnosis method - Google Patents
Compressor state monitoring platform and leakage fault diagnosis method Download PDFInfo
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- 238000000034 method Methods 0.000 title claims abstract description 56
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- 239000007789 gas Substances 0.000 description 16
- VNWKTOKETHGBQD-UHFFFAOYSA-N methane Chemical compound C VNWKTOKETHGBQD-UHFFFAOYSA-N 0.000 description 6
- 238000007789 sealing Methods 0.000 description 4
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
- F04B—POSITIVE-DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS
- F04B51/00—Testing machines, pumps, or pumping installations
Abstract
The invention provides a compressor state monitoring platform and a leakage fault diagnosis method, wherein the monitoring platform comprises a compressor, a pressure sensor and data acquisition equipment, the compressor comprises a cylinder and a flywheel, and a power indicating hole for measuring the pressure in the cylinder and a pressure guiding hole for measuring the pressure in a valve cavity are formed in the cylinder; the pressure sensor is arranged at the power indicating hole and the pressure guiding hole; the flywheel is connected with a motor, one side of the flywheel is provided with a proximity switch, and the dead point position is marked by the proximity switch; the data acquisition equipment is electrically connected with the pressure sensors and the proximity switch, and the data acquisition equipment is used for acquiring a first pressure signal and a dead point signal. Compared with the prior art, the method has the advantages that relevant pressure signal data are collected rapidly and accurately through the built monitoring platform, and accurate leakage data can be obtained through a calculation mode in a diagnosis method and used for timely and accurately judging the leakage fault condition of the compressor.
Description
Technical Field
The invention relates to the technical field of compressors, in particular to a compressor state monitoring platform and a fault diagnosis method.
Background
The reciprocating compressor is a universal machine widely applied to the national economy fields such as refrigeration air conditioner, aerodynamic force, petrochemical industry, natural gas industry and the like. The reciprocating motion and the rotary motion are included, the excitation sources are numerous, the fault diagnosis difficulty of the compressor is high, and the precision is low. Leakage failure is the most common failure of reciprocating compressors, many of which initially manifest themselves as leakage. Leakage refers to the failure of gas flowing into or out of the cylinder through a leakage channel under the action of pressure difference when sealing is needed to be maintained, which leads to the reduction of the air inflow of the reciprocating compressor, the rise of the exhaust temperature, the damage of an accelerating air valve and serious influence on the efficiency and the reliability of the compressor.
Although the prior method can identify whether leakage exists, a standard database for comparison is established, or a large number of normal samples are collected to train a pattern recognition model. Because of various compressor types and various operation conditions, the actual implementation difficulty of collecting a large number of normal samples, establishing a standard database or collecting training samples is high; in addition, the existing diagnosis method has high difficulty in acquiring data samples, cannot give out measurement of fault severity, cannot accurately make maintenance measures, and can provide data support for maintenance according to conditions.
Disclosure of Invention
In view of the above drawbacks of the prior art, an object of the present invention is to provide a compressor status monitoring platform and a method for diagnosing leakage faults, which are used for solving the problems that the collection difficulty of sample data in the prior art is high and the leakage faults of a compressor cannot be accurately monitored.
To achieve the above and other related objects, the present invention provides a compressor status monitoring platform, comprising:
the compressor comprises a cylinder and a flywheel, wherein a power indicating hole for measuring the pressure in the cylinder and a pressure guiding hole for measuring the pressure in the valve cavity are formed in the cylinder, and the number of the power indicating hole and the pressure guiding hole is multiple;
the pressure sensors are respectively arranged at the power indicating hole and the pressure guiding hole and are used for acquiring pressure signals;
the flywheel is connected with a motor, one side of the flywheel is provided with a proximity switch, and the dead point position is marked by the proximity switch;
the data acquisition equipment is electrically connected with the pressure sensors and the proximity switch, and the data acquisition equipment is used for acquiring a first pressure signal and a dead point signal.
Optionally, the indicator hole and the pressure guiding hole are both formed in the cylinder body of the cylinder, the indicator hole is located at two axial ends of the cylinder body of the cylinder, and the pressure guiding hole is located at a valve nest of the cylinder body of the cylinder.
Optionally, a groove is formed on a side portion of the flywheel, and when the proximity switch corresponds to the groove in the rotation process of the flywheel, the distance between the flywheel and the proximity switch is increased, and the position is recorded as a point signal.
Optionally, the data acquisition device is configured with a signal acquisition capability of not less than 16 channels, the a/D conversion accuracy of each channel is not less than 16 bits, and the sampling rate of a single channel is not less than 10kS/s.
Correspondingly, the invention also provides a method for diagnosing the leakage fault of the compressor, which comprises the following steps:
acquiring a dynamic first pressure signal and a dynamic dead point signal in the working process of a compressor through the compressor state monitoring platform;
intercepting the first pressure signal in one working cycle according to the dead point signal, and converting the first pressure signal changing with time into a second pressure signal changing with the cylinder volume in the compressor;
according to the describedThe second pressure signal calculates the average value of the pressure of the air inlet valve cavity in one working periodAverage value of the exhaust valve chamber pressure>
Taking the cylinder volume V in the compressor as an abscissa and the pressure p as an ordinate, the average inlet pressureExhaust pressure->With in-cylinder pressure p c Drawing the two images in the same image to obtain an indicator diagram with average inlet pressure and exhaust pressure lines;
finding out the section where the intersection points of the average intake pressure line, the exhaust pressure line and the indicator diagram exist, and calculating the cylinder volume V at the intersection points by adopting an interpolation method n1 ，V n2 ，V n3 ，V n4 Calculating the actual inhaled gas volume DeltaV of the air inlet state of the cylinder 1 ＝V n2 -V n1 Actual exhaust gas volume DeltaV for cylinder exhaust state n ＝V n3 -V n4 ；
Calculate mass flow rate q into cylinder m1 And mass flow q of the exhaust cylinder m2 Define α as the mass flow ratio of the exiting cylinder to the entering cylinder, i.eLeakage ratio Δα= |1- α|.
Optionally, intercepting the first pressure signal in a working cycle according to the dead point signal comprises:
the first pressure signal over time is (t, p) c ，p s ，p d U), t is time, p c Is in-cylinder pressure, p s For inlet valve cavity pressure, p d And U is the voltage signal of the dead point position and is the pressure of the exhaust valve cavity.
Optionally, converting the first pressure signal over time to a second pressure signal over cylinder volume in the compressor, comprising:
the dead point signal U always maintains a high level or a low level, t 1 The occurrence of low level or high level at any time indicates that the piston of the cylinder is positioned at the top dead center signal, a working period is formed between the two low level or high level signals, and the next low level signal is arranged at t 2 Time t 1 To t 2 The data between the moments is the operation data of one period, let t 1 The moment corresponds to 0 DEG crank angle, t 2 The moment corresponds to 360 DEG crank angle, and the middle moment t i Corresponding angle theta i The interpolation method is calculated by the following formula:
the crank angle and the cylinder volume have corresponding relation and different angles theta i The cylinder volume is:
wherein A is the area swept by the cylinder piston, S is the stroke of the compressor, and alpha is the relative clearance; lambda is the crank to connecting rod ratio in the compressor;
said first pressure signal, which varies with time, is converted by the above into a second pressure signal, which varies with the cylinder volume in the compressor.
Optionally, find out the existence interval of the intersection points of the average intake pressure line, the exhaust pressure line and the indicator diagram, and calculate the cylinder volume V at the intersection point by interpolation n1 ，V n2 ，V n3 ，V n4 Calculating the actual inhaled gas volume DeltaV of the air inlet state of the cylinder 1 ＝V n2 -V n1 Actual exhaust gas volume DeltaV for cylinder exhaust state 2 ＝V n3 -V n4 Comprising:
(V i ，p i ) The cylinder volume and the pressure corresponding to each point of the indicator diagram are defined by the following conditions:the existence interval [ (V) of the intersection point of the average air inlet pressure line and the indicator diagram can be obtained i ，p i )，(V i+1 ，p i+1 )]Linear interpolation is used, according to:deriving cylinder volume V at the intersection n1 The method comprises the following steps: ,similarly calculate V n2 ，V n3 ，V n4 Solving for V n3 ，V n4 In the time equation +.>Should be substituted with->
Optionally, the mass flow q into the cylinder is calculated m1 And mass flow q of the exhaust cylinder m2 Define α as the mass flow ratio of the exiting cylinder to the entering cylinder, i.eThe leak ratio Δα= |1- α| includes:
from the state equation p=ρr g T, deriving the medium density ρ of the intake and exhaust state 1 ，ρ 2 Further, the mass flow q entering the compressor cylinder is obtained m1 And mass flow rate q of discharge compressor cylinder m2 ：
Wherein R is g Is a gas constant; t (T) s Is the temperature of the intake air; t (T) d Is the exhaust temperature.
Optionally, the mass flow q into the cylinder is calculated m1 And mass flow q of the exhaust cylinder m2 Define α as the mass flow ratio of the exiting cylinder to the entering cylinder, i.eThe leak ratio Δα= |1- α| after calculating the leak ratio, includes:
diagnosing leakage faults by taking alpha as a characteristic parameter, quantifying fault degrees by taking delta alpha as a characteristic index, setting threshold values A and B, and ensuring normal state when A is less than or equal to alpha and less than or equal to B; when α < a, there is a leakage fault; when α > B, there is a leak-in fault.
According to the technical means, the pressure signal is acquired through the pressure sensor at the pressure guiding hole and the power indicating hole by monitoring the platform acquisition point, so that the signal data of the compressor can be acquired rapidly and accurately, and the problem that the diagnosis standard database is difficult to establish due to different compressor types and variable working conditions in the existing method by taking the conservation of mass as the diagnosis basis is solved. In the diagnosis method, based on the principle of mass conservation, dynamic pressure signals and dead point signals are collected, an indicator diagram with average inlet and outlet pressure lines is obtained, the intersection point of the inlet and outlet pressure lines and the indicator diagram is found through an interpolation method, the volume of the sucked gas in the actual inlet state and the volume of the discharged gas in the actual outlet state are calculated, then the density of the gas in the inlet and outlet states is derived through a state equation, the mass flow of the actual sucked cylinder and the mass flow of the discharged cylinder are obtained, the ratio of the mass flow of the discharged cylinder and the mass flow of the sucked cylinder is taken as characteristic parameters to diagnose leakage faults, the absolute value of the difference value of the mass flow ratio and 1 is taken as characteristic index to quantify the leakage fault degree, the accurate quantification of the leakage faults is realized, and data support is provided for regular maintenance. Compared with the prior art, the method has the advantages that relevant pressure signal data are collected rapidly and accurately through the built monitoring platform, and accurate leakage data can be obtained through a calculation mode in a diagnosis method and used for timely and accurately judging the leakage fault condition of the compressor.
Drawings
FIG. 1 is a schematic diagram of a monitoring point arrangement of a compressor status monitoring platform according to an embodiment of the present invention (where cp is the dynamic pressure in the cylinder, sp is the pressure in the air intake valve cavity, dp is the pressure in the air exhaust valve cavity, and k is the key phase);
FIG. 2 shows a cross-sectional view of a cylinder block in a compressor condition monitoring platform according to an embodiment of the present invention;
FIG. 3 illustrates a side view of a cylinder in a compressor condition monitoring platform according to an embodiment of the present invention;
FIG. 4 is a schematic diagram showing a structure of a center signal test in a compressor status monitoring platform according to an embodiment of the present invention;
FIG. 5 is a flow chart of the original signals collected in a compressor status monitoring platform according to an embodiment of the present invention;
FIG. 6 is a schematic diagram of a monitoring system collected in a compressor status monitoring platform according to an embodiment of the present invention;
FIG. 7 is a flow chart illustrating a method of diagnosing a leakage fault of a compressor according to an embodiment of the present invention;
FIG. 8 is a diagram showing an exemplary original signal of a method for diagnosing a leakage failure of a compressor according to an exemplary embodiment of the present invention;
FIG. 9 is a diagram showing the average intake pressure line and the exhaust pressure line in a method for diagnosing a leakage failure of a compressor according to an embodiment of the present invention.
Description of the reference numerals
The device comprises a cylinder 10, a cylinder body 11, a power indicating hole 12, a pressure guiding hole 13, a flywheel 20, a groove 21, a proximity switch 22, a motor 23 and a data acquisition device 30.
Detailed Description
Other advantages and effects of the present invention will become apparent to those skilled in the art from the following disclosure, which describes the embodiments of the present invention with reference to specific examples. The invention may be practiced or carried out in other embodiments that depart from the specific details, and the details of the present description may be modified or varied from the spirit and scope of the present invention.
Further advantages and effects of the present invention will become readily apparent to those skilled in the art from the disclosure herein, by referring to the accompanying drawings and the preferred embodiments. The invention may be practiced or carried out in other embodiments that depart from the specific details, and the details of the present description may be modified or varied from the spirit and scope of the present invention. It should be understood that the preferred embodiments are presented by way of illustration only and not by way of limitation.
It should be noted that the illustrations provided in the following embodiments merely illustrate the basic concept of the present invention by way of illustration, and only the components related to the present invention are shown in the drawings and are not drawn according to the number, shape and size of the components in actual implementation, and the form, number and proportion of the components in actual implementation may be arbitrarily changed, and the layout of the components may be more complicated.
In the following description, numerous details are set forth in order to provide a more thorough explanation of embodiments of the present invention, it will be apparent, however, to one skilled in the art that embodiments of the present invention may be practiced without these specific details, in other embodiments, well-known structures and devices are shown in block diagram form, rather than in detail, in order to avoid obscuring the embodiments of the present invention.
Fig. 1 is a compressor state monitoring platform according to an exemplary embodiment of the present application, where the monitoring platform includes a compressor, the compressor includes a cylinder 10 and a flywheel 20, a power indicating hole 12 for measuring the pressure in a cylinder 11 and a pressure guiding hole 13 for measuring the pressure in a valve cavity are machined on the cylinder 10, and the power indicating hole 12 and the pressure guiding hole 13 are multiple;
a plurality of pressure sensors respectively installed at the power indicating hole 12 and the pressure guiding hole 13, wherein the pressure sensors are used for acquiring pressure signals;
the flywheel 20 is connected with a motor 23, one side of the flywheel 20 is provided with a proximity switch 22, and the dead point position is marked by the proximity switch 22;
the data acquisition equipment 30, the data acquisition equipment 30 with a plurality of pressure sensor, proximity switch 22 electricity federation, the data acquisition equipment 30 is used for acquireing first pressure signal and dead center signal.
In some embodiments, the power indicating hole 12 and the pressure guiding hole 13 are both formed on the body 11 of the cylinder 10, the power indicating hole 12 is located at two axial ends of the body 11 of the cylinder 10, and the pressure guiding hole 13 is located at a valve socket of the body 11 of the cylinder 10. For example, as shown in fig. 2, the power indicating holes 12 are opened at both axial ends of the cylinder 11; as shown in fig. 3, the pressure guiding hole 13 is formed at the valve nest of the cylinder body, so that the problem of inconvenient assembly and disassembly caused by the fact that the valve cavity pressure guiding hole 13 is arranged on the valve cover in the prior art can be avoided.
In some embodiments, the side of the flywheel 20 is provided with a groove 21, and when the proximity switch 22 corresponds to the groove 21 during rotation of the flywheel 20, the distance between the flywheel 20 and the proximity switch 22 increases, and this position records a point signal. For example, as shown in fig. 4, the target plane is set by cutting the groove 21 on the flywheel 20, and the state of the proximity switch 22 is excited to change by changing the distance between the groove 21 on the flywheel 20 and the proximity switch 22, so that a dead point signal is output, thereby replacing the scheme of connecting the target plane to the flywheel 20 by threads in the prior art, and avoiding the potential danger of falling off and flying out of the target plane when the flywheel 20 of the compressor rotates at a high speed.
In some embodiments, the data acquisition device 30 is configured with no less than 16 channel signal acquisition capabilities, with an A/D conversion accuracy of no less than 16 bits per channel, and a sampling rate of no less than 10kS/s for a single channel.
It should be noted that, in the monitoring platform of the present embodiment, besides optimization of the cylinder 10, improvement of the flywheel 20, arrangement of the monitoring points, and configuration of the data acquisition device 30, a data acquisition system, an analysis software design of a proposed core algorithm, and communication between the monitoring system and a self-contained control system (such as a PLC system) of the unit can be configured, so as to facilitate calculation of data signals in a subsequent leakage fault diagnosis method.
In a specific embodiment, the invention is implemented by using a D-type air-cooled two-stage piston type natural gas compressor, the rated rotation speed is 740r/min, the stroke is 130mm, the center distance of connecting rods is 400mm, the diameters of the primary cylinder 10 and the secondary cylinder 10 are 175mm and 125mm respectively, and the clearance volumes are 0.15 and 0.19 respectively.
The structure of the compressor cylinder 10 is optimized, a power indicating hole 12 for measuring the pressure in the cylinder is formed in the cylinder 10 body, as shown in fig. 2, and a valve cavity pressure leading hole 13 is formed at a valve cavity of the cylinder body 11, as shown in fig. 3. Because the piston position and the crank angle have a one-to-one correspondence, the flywheel 20 is additionally provided with the proximity switch 22 for marking the dead point position, and the working principle of the proximity switch 22 is that when the distance between the proximity switch and a target exceeds (or is smaller than) a design value, a circuit is connected or disconnected, so that an abrupt voltage value is generated, and a high level or a low level is output. The invention adopts the form of the groove 21 to realize the distance change; the jigger brings the piston to a top dead center position, where the target plane is set at the appropriate position (lower or both sides) of the flywheel 20. In this embodiment, a groove 21 for marking the top dead center position is machined below the flywheel 20, and a proximity switch 22 is installed at a position opposite to the groove 21, as shown in fig. 4, so that the distance between the proximity switch 22 and the outer circumferential surface of the flywheel 20 is 5mm (specific numerical values are different according to different models of the proximity switch 22). In the working process of the compressor, when the position outside the groove 21 on the outer circle surface of the rotary flywheel 20 is opposite to the proximity switch 22, the distance between the surface and the proximity switch 22 is 5mm, and is smaller than the action value 6mm of the proximity switch 22 (the specific numerical value is different according to the different types of the proximity switch 22), the circuit is in a communication state, and the proximity switch 22 outputs high level 7.6V (the specific numerical value is different according to the different types of the proximity switch 22); when the groove 21 is opposite to the proximity switch 22, the distance between the proximity switch 22 and the groove bottom plane exceeds 6mm (the specific numerical value is different according to the different types of the proximity switch 22), the circuit is in an off state, and low level 0V is output, so that the piston is positioned at the top dead center.
The state monitoring system of the D-type compressor unit of the embodiment is provided with 12 paths of dynamic pressure sensors and 1 path of proximity switches 22, and is used for acquiring dynamic pressures in the cylinder 10 and the valve cavity and positions of pistons at all moments in the working process of the compressor, and the arrangement of monitoring points is shown in figure 1. In consideration of the late-stage expansibility, a data acquisition device 30 having a signal acquisition capability of not less than 16 channels is configured, the A/D conversion accuracy of each channel is not lower than 16 bits, and the sampling rate of a single channel is not lower than 10kS/s. The dynamic changes of the pressure and the voltage of the proximity switch 22 are picked up by the sensor and converted into corresponding analog signals to be output, the signals are converted into digital signals through the data acquisition system and stored in a computer hard disk for subsequent analysis, and the detailed data acquisition flow is shown in fig. 5. The structure of the actually built monitoring system is schematically shown in fig. 6, the system consists of a field part and a central control room part, data are transmitted through an Ethernet, and the field device comprises a sensor and a data acquisition system, wherein the data acquisition system is arranged in an explosion-proof control cabinet beside a unit so as to meet the requirement of a natural gas environment on explosion prevention.
Fig. 7 is a flowchart illustrating a method for diagnosing a leakage fault of a compressor according to an exemplary embodiment of the present application, where the method may use the compressor status monitoring platform shown in fig. 1 to obtain required signal data, and it should be understood that the method may also be used on other compressors and be specifically performed in the environment by other detecting devices, and the present embodiment is not limited to the implementation environment and devices to which the method is applicable.
As shown in fig. 7, in an exemplary embodiment, a method for diagnosing a leakage fault of a compressor includes at least steps one to six, which are described in detail as follows:
step one, acquiring a dynamic first pressure signal and a dynamic dead point signal in the working process of a compressor through any one of the compressor state monitoring platforms;
step two, intercepting the first pressure signal in one working cycle according to the dead point signal, and converting the first pressure signal changing along with time into a second pressure signal changing along with the volume of the cylinder 10 in the compressor;
in this embodiment, the first pressure signal over time is (t, p) c ，p s ，p d U), t is time, p c For the pressure in the cylinder 10, p s For inlet valve cavity pressure, p d And U is the voltage signal of the dead point position and is the pressure of the exhaust valve cavity.
The dead point signal U always maintains a high level or a low level, t 1 The occurrence of a low level or a high level at a moment represents that the piston of the cylinder 10 is positioned at the top dead center signal, a working period is formed between the two low level or high level signals, and the next low level signal is arranged to be present at t 2 Time t 1 To t 2 The data between the moments is the operation data of one period, let t 1 The moment corresponds to 0 DEG crank angle, t 2 The moment corresponds to 360 DEG crank angle, and the middle moment t i Corresponding angle theta i The interpolation method is calculated by the following formula:
the crank angle and the volume of the cylinder 10 have a corresponding relationship, and the different angles theta i The cylinder 10 has a volume of:
wherein A is the area swept by the piston of the cylinder 10, S is the stroke of the compressor, and alpha is the relative clearance; lambda is the crank to connecting rod ratio in the compressor;
said first pressure signal, which varies with time by the above formula, is converted into a second pressure signal, which varies with the volume of the cylinder 10 in the compressor.
In a specific embodiment, the initial compressor operates under variable frequency conditions of 373r/min, 0.5MPaG for air intake pressure, 4.7MPaG for exhaust pressure and 22.8 ℃ for air intake temperature, and the original operation data of the secondary cylinder 10 is shown in fig. 8, and the interval between two dead point signals is a working period; intercepting 382.06s to 382.22s based on the dead point signalAnalyzing the data; corresponding time t of 0 degree crank angle 1 Corresponding to time t of 360 ° crank angle = 382.06 2 = 382.22. Intermediate time t i Corresponding angle theta i The linear interpolation is calculated by the following formula:
different angles of rotation theta i The cylinder 10 has the following volume:
step three, calculating the average value of the pressure of the air inlet valve cavity in one working period according to the second pressure signalAverage value of the exhaust valve chamber pressure>
In a specific embodiment, the average value of the pressure signal in the valve cavity is:
taking the volume V of the cylinder 10 in the compressor as an abscissa and the pressure p as an ordinate, and taking the average inlet pressureExhaust pressure->With the pressure p in the cylinder 10 c Drawing the two images in the same image to obtain an indicator diagram with average inlet pressure and exhaust pressure lines;
in a specific embodiment, the average intake and exhaust pressures and the pressure change in the cylinder 10 are plotted in the same graph with the volume V in the cylinder 10 as the abscissa and the pressure p as the ordinate, so as to obtain an indicator diagram with intake and exhaust pressure lines, see fig. 9.
Step five, finding out the section where the intersection points of the average intake pressure line, the exhaust pressure line and the indicator diagram exist, and calculating the volume V of the cylinder 10 at the intersection point by adopting an interpolation method n1 ，V n2 ，V n3 ，V n4 The actual intake gas volume DeltaV of the intake state of the cylinder 10 is calculated 1 ＝V n2 -V n1 Actual exhaust gas volume Δv in the exhaust state of the cylinder 10 2 ＝V n3 -V n4 ；
In the course of the implementation, (V) i ，p i ) For the volume and pressure of the cylinder 10 corresponding to each point of the indicator diagram, the following conditions are adopted:the existence interval [ (V) of the intersection point of the average air inlet pressure line and the indicator diagram can be obtained i ，p i )，(V i+1 ，p i+1 )]Linear interpolation is used, according to: />Deriving cylinder 10 volume V at the intersection n1 The method comprises the following steps: ,/>Similarly calculate V n2 ，V n3 ，V n4 Solving for V n3 ，V n4 In the time equation +.>Should be substituted with->
In a specific embodiment, the conditions are:
(p i -1.675)(p i+1 -1.675)≤0
finding out the intersection point V of the average intake pressure line and the indicator diagram n1 Presence interval [ (0.832,1.671), (0.824,1.692)]。
The linear interpolation method is adopted, and the method comprises the following steps:
determination of cylinder volume V at intersection n1 ＝0.830L。
Similarly available, V n2 ＝1.880L，V n3 ＝0.917L，V n4 ＝0.452L。
Intake state actual intake gas volume DeltaV 1 ：
ΔV 1 ＝V n2 -V n1 ＝1.880-0.830＝1.050L
Exhaust state actual exhaust gas volume DeltaV 2 ：
ΔV 2 ＝V n3 -V n4 ＝0.917-0.452＝0.465L
Step six, calculating the mass flow rate entering the cylinder 10 m1 And mass flow q out of cylinder 10 m2 Define α as the mass flow ratio of the exiting cylinder 10 to the entering cylinder 10, i.eLeakage ratio Δα= |1- α|.
In an actual implementation, the equation of state p=ρr g T, deriving the medium density ρ of the intake and exhaust state 1 ，ρ 2 Further, the mass flow q into the compressor cylinder 10 is determined m1 And mass flow q exiting compressor cylinder 10 m2 ：
Wherein R is g Is a gas constant; t (T) s K is the air inlet temperature; t (T) d Is the exhaust temperature, K, T s And T d The data is obtained by reading the monitoring data of a control system (such as a PLC control system) of the compressor unit.
Finally, diagnosing leakage faults by taking alpha as a characteristic parameter, quantifying fault degrees by taking delta alpha as a characteristic index, setting threshold values A and B, and ensuring that the state is normal when A is less than or equal to alpha and less than or equal to B; when alpha < A, leakage faults exist, such as leakage of a suction valve (including valve plate fracture, notch, sealing surface fracture and the like); when alpha > B, leakage-in faults exist, such as leakage of the exhaust valve (including valve plate fracture, notch, sealing surface damage and the like). The threshold A, B can be dynamically adjusted according to the allowable value of a specific project. The characteristic index delta alpha represents the proportion of the leaked gas quantity, and can directly reflect the leakage quantity.
In a specific embodiment, the equation of state p=ρr g T, deriving the medium density ρ of the intake and exhaust state 1 ＝11.25kg/m 3 ，ρ 2 ＝25.06kg/m 3 Wherein, the temperature T of air inlet and air outlet s ＝295.8K、T d =376-1K is monitored by the PLC control system of the unit itself.
Mass flow q into compressor cylinder 10 m1 ：
q m1 ＝ρ 1 ΔV 1 ＝11.25×1.050/1000＝0.0117kg
Mass flow q exiting compressor cylinder 10 m2 ：
q m2 ＝ρ 2 ΔV 2 ＝25.06×0.465/1000＝0.0118kg
Mass flow ratio of exhaust cylinder 10 to intake cylinder 10Leak ratio Δα= |1-1.009|=0.009. Taking actual factors and errors into consideration, the allowable leakage amount of the unit is 5%, namely, the threshold value A=0.95 and the threshold value B=1.05, which indicates that the secondary cover side cylinder 10 has no leakage fault at this time and is in a normal state.
By the diagnosis method in the invention, after 7536 hours of operation of the unit, alpha=1.37 and delta alpha=0.37 can be obtained by monitoring data, which indicates that leakage faults of the exhaust valve exist at the moment, and the leakage gas quantity proportion is 37%. The inspection of the disassembled compressor shows that the exhaust valve has serious faults, the sealing fails, the valve plate breaks, and the calculation result is consistent with the actual situation.
It should be noted that, the compressor status monitoring platform provided in the above embodiment and the method for diagnosing a leakage fault of a compressor provided in the above embodiment belong to the same concept, and the specific manner in which each module and unit perform operations has been described in detail in the method embodiment, which is not repeated herein. In practical application, the monitoring platform provided in the above embodiment may distribute the functions to different functional modules according to needs, that is, the internal structure of the device is divided into different functional modules to complete all or part of the functions described above, which is not limited herein.
The above embodiments are merely illustrative of the principles of the present invention and its effectiveness, and are not intended to limit the invention. Modifications and variations may be made to the above-described embodiments by those skilled in the art without departing from the spirit and scope of the invention. Accordingly, it is intended that all equivalent modifications and variations of the invention be covered by the claims, which are within the ordinary skill of the art, be within the spirit and scope of the present disclosure.
Claims (9)
1. A method of diagnosing a leakage failure of a compressor, comprising:
acquiring a dynamic first pressure signal and a dynamic dead point signal in the working process of a compressor through a compressor state monitoring platform;
intercepting the first pressure signal in one working cycle according to the dead point signal, and converting the first pressure signal changing with time into a second pressure signal changing with the cylinder volume in the compressor;
calculating the average value of the pressure of the air inlet valve cavity in one working period according to the second pressure signalAverage value of the exhaust valve chamber pressure>
Taking the cylinder volume V in the compressor as an abscissa and the pressure p as an ordinate, the average inlet pressureExhaust pressure->With in-cylinder pressure p c Drawing the two images in the same image to obtain an indicator diagram with average inlet pressure and exhaust pressure lines;
finding out the section where the intersection points of the average intake pressure line, the exhaust pressure line and the indicator diagram exist, and calculating the cylinder volume V at the intersection points by adopting an interpolation method n1 ，V n2 ，V n3 ，V n4 Calculating the actual inhaled gas volume DeltaV of the air inlet state of the cylinder 1 ＝V n2 -V n1 Actual exhaust gas volume DeltaV for cylinder exhaust state 2 ＝V n3 -V n4 ；
Calculate mass flow rate q into cylinder m1 And mass flow q of the exhaust cylinder m2 Define α as the mass flow ratio of the exiting cylinder to the entering cylinder, i.eLeakage ratio Δa= |1- α|;
the compressor state monitoring platform comprises a compressor, a plurality of pressure sensors and data acquisition equipment, wherein the compressor comprises a cylinder and a flywheel, a power indicating hole for measuring the pressure in the cylinder and a pressure guiding hole for measuring the pressure of a valve cavity are formed in the cylinder, and the power indicating hole and the pressure guiding hole are multiple; the pressure sensors are respectively arranged at the power indicating hole and the pressure guiding hole and are used for acquiring pressure signals; the flywheel is connected with a motor, one side of the flywheel is provided with a proximity switch, and the dead point position is marked by the proximity switch; the data acquisition equipment is electrically connected with the pressure sensors and the proximity switch, and the data acquisition equipment is used for acquiring a first pressure signal and a dead point signal.
2. The method for diagnosing a leakage failure of a compressor according to claim 1, wherein: the power indicating holes and the pressure guiding holes are formed in the cylinder body of the cylinder, the power indicating holes are formed in two axial ends of the cylinder body of the cylinder, and the pressure guiding holes are formed in the valve nest of the cylinder body of the cylinder.
3. The method for diagnosing a leakage failure of a compressor according to claim 2, wherein: and a groove is formed in the side part of the flywheel, and when the proximity switch corresponds to the groove in the rotation process of the flywheel, the distance between the flywheel and the proximity switch is increased, and the position is recorded with a point signal.
4. A method for diagnosing a leakage failure of a compressor according to any one of claims 1 to 3, wherein: the data acquisition equipment is configured with signal acquisition capacity of not less than 16 channels, the A/D conversion precision of each channel is not lower than 16 bits, and the sampling rate of a single channel is not lower than 10kS/s.
5. The method for diagnosing a leakage failure of a compressor according to claim 4, wherein: intercepting the first pressure signal in one working cycle according to the dead center signal, wherein the method comprises the following steps:
the first pressure signal over time is (t, p) c ，p s ，p d U), t is time, p c Is in-cylinder pressure, p s For inlet valve cavity pressure, p d And U is the voltage signal of the dead point position and is the pressure of the exhaust valve cavity.
6. The method for diagnosing a leakage failure of a compressor according to claim 5, wherein: converting said first pressure signal over time into a second pressure signal that varies with cylinder volume in the compressor, comprising:
the dead point signal U always maintains a high level or a low level, t 1 The occurrence of low level or high level at any time indicates that the piston of the cylinder is positioned at the top dead center signal, a working period is formed between the two low level or high level signals, and the next low level signal is arranged at t 2 Time t 1 To t 2 The data between the moments is the operation data of one period, let t 1 The moment corresponds to 0 DEG crank angle, t 2 The moment corresponds to 360 DEG crank angle, and the middle moment t i Corresponding angle theta i The interpolation method is calculated by the following formula:
the crank angle and the cylinder volume have corresponding relation and different angles theta i The cylinder volume is:
wherein A is the area swept by the cylinder piston, S is the stroke of the compressor, and alpha is the relative clearance; lambda is the crank to connecting rod ratio in the compressor;
said first pressure signal, which varies with time, is converted by the above into a second pressure signal, which varies with the cylinder volume in the compressor.
7. The method for diagnosing a leakage failure of a compressor according to claim 6, wherein: finding out the section where the intersection points of the average intake pressure line, the exhaust pressure line and the indicator diagram exist, and calculating the cylinder volume V at the intersection points by adopting an interpolation method n1 ，V n2 ，V n3 ，V n4 Calculating the actual inhaled gas volume DeltaV of the air inlet state of the cylinder 1 ＝V n2 -V n1 Actual exhaust gas volume DeltaV for cylinder exhaust state 2 ＝V n3 -V n4 Comprising:
(V i ，p i ) The cylinder volume and the pressure corresponding to each point of the indicator diagram are defined by the following conditions:the existence interval [ (V) of the intersection point of the average air inlet pressure line and the indicator diagram can be obtained i ，p i )，(V i+1 ，p i+1 )]Linear interpolation is used, according to:deriving cylinder volume V at the intersection n1 The method comprises the following steps: ,similarly calculate V n2 ，V n3 ，V n4 Solving for V na ，V n4 In the time equation +.>Should be substituted with->
8. The method for diagnosing a leakage failure of a compressor according to claim 7, wherein: calculate mass flow rate q into cylinder m1 And mass flow q of the exhaust cylinder m2 Definition a is the mass flow ratio of the exhaust cylinder to the intake cylinder, i.eThe leak ratio Δα= |1- α| includes:
from the state equation p=ρr g T, deriving the medium density ρ of the intake and exhaust state 1 ，ρ 2 And then the mass flow rate of the air entering the compressor cylinder is obtainedq m1 And mass flow rate q of discharge compressor cylinder m2 ：
Wherein R is g Is a gas constant; t (T) s Is the temperature of the intake air; t (T) d Is the exhaust temperature.
9. The method for diagnosing a leakage failure of a compressor as set forth in claim 8, wherein: calculate mass flow rate q into cylinder m1 And mass flow q of the exhaust cylinder m2 Define α as the mass flow ratio of the exiting cylinder to the entering cylinder, i.eThe leak ratio Δα= |1- α| after calculating the leak ratio, includes:
diagnosing leakage faults by taking alpha as a characteristic parameter, quantifying fault degrees by taking delta alpha as a characteristic index, setting threshold values A and B, and ensuring normal state when A is less than or equal to alpha and less than or equal to B; when alpha is less than A, leakage faults exist; when α > B, there is a leak-in fault.
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