CN115468716A - A labyrinth compressor sealing performance test device and test method - Google Patents

Abstract

The invention relates to the technical field of compressors, in particular to a labyrinth compressor sealing performance testing device which can conveniently realize testing of labyrinth throttling and gas leakage and comprises a crankcase transmission box and a cylinder, wherein a crankshaft is arranged in the crankcase transmission box and is connected with one end of a piston rod through a connecting rod transmission mechanism, a piston positioned in a piston cavity in the cylinder is arranged on the piston rod, the upper end of the piston cavity is communicated with an air inlet channel and an air outlet channel, a packing box matched with the piston rod is arranged in the cylinder, packing is arranged in the packing box, the outer surface of the piston and the inner wall of the piston cavity are in a tooth shape, a gap is reserved between the outer surface of the piston and the inner wall of the piston cavity, the lower end of the piston cavity is communicated with a leaked gas measuring cavity, a flow sensor is arranged in the measuring cavity, a pressure sensor is arranged on the side wall of the piston, a pressure release valve and a pressure gauge are also arranged in the measuring cavity, and meanwhile, the invention also provides a corresponding testing method.

Description

A labyrinth compressor sealing performance test device and test method

technical field

The invention relates to the technical field of compressors, in particular to a labyrinth compressor sealing performance test device and test method.

Background technique

Labyrinth compressor refers to a new type of compressor that adopts non-contact labyrinth sealing technology between the piston and cylinder wall, piston rod and packing. The sealing structure of the labyrinth piston compressor is non-contact, the piston and packing are sealed by the labyrinth, and the working cycle is suction, compression and exhaust. Because it is a labyrinth non-contact seal, in actual use, it is inevitable that a small amount of gas will pass through the gap between the piston and the cylinder wall. It is necessary to test the labyrinth throttling and gas leakage during the reciprocating motion. Sealing performance, improved compression efficiency, and reduced energy consumption provide design basis and data verification, which cannot be easily tested with existing test devices.

Contents of the invention

In order to solve the problem that the sealing performance of the labyrinth piston cannot be monitored conveniently at the piston of the existing labyrinth compressor, the present invention provides a test device for the sealing performance of the labyrinth compressor, which can conveniently realize the test of labyrinth throttling and gas leakage. The invention also provides a corresponding test method.

Its technical scheme is as follows; a labyrinth compressor sealing performance test device, which includes a crankcase transmission case and a cylinder, a crankshaft is arranged in the crankcase transmission case, and the crankshaft is connected to one end of the piston rod through a connecting rod transmission mechanism, so The piston rod is installed with a piston located in the piston cavity of the cylinder, the upper end of the piston cavity communicates with the intake channel and the exhaust channel, and the cylinder is provided with a stuffing box that cooperates with the piston rod. Filling is arranged in the box, the outer surface of the piston and the inner wall of the piston chamber are tooth-shaped and there is a gap between the two. It is characterized in that the lower end of the piston chamber is connected to the leakage gas measurement chamber, and the measurement chamber There is a flow sensor, a pressure sensor is installed on the side wall of the piston, and a pressure relief valve and a pressure gauge are also installed in the measuring chamber.

It is further characterized in that the stuffing box includes an upper stuffing box and a lower stuffing box located at both ends of the piston, and the stuffing is floatingly arranged in the stuffing box;

The piston rod is provided with a platform stage, the lower end of the piston is against the step surface of the platform stage, and the upper end is fixed by a lock nut installed on the piston rod;

The outer wall of the piston is covered with a casing, and the outer surface of the casing and the inner wall of the piston cavity are toothed in different sizes;

The piston includes a middle shaft sleeve, the end of the middle shaft sleeve is connected to the middle of the disc body, the end of the disc body is connected to the ring body, and there is an empty space between the middle shaft sleeve and the ring body, and the middle shaft The sleeve, disc body and ring body are integrated structure;

The shell is fixed to the ring body by screws, and the side wall of the ring body and the labyrinth tooth bottom of the side wall of the shell are provided with mounting holes for pressure sensors.

其中，

K＝b/c，R为气体常数、T₀为活塞高压侧气体温度，P₀为测量活塞高压侧压力的、P_N为迷宫第N齿处的压力；

其中ε为活塞进排气压比；n为压缩机转速；S为压缩机行程，ψ、θ和γ为拟合参数，h为径向间隙与间隙宽度c一致，D为活塞直径，ν_u为吸气以前的气体声速。A test method for sealing performance of a labyrinth compressor, which is characterized by measuring the gap length b, gap width c, and annular labyrinth gap cross-sectional area A between the piston and the inner wall of the piston chamber, measuring the tooth spacing B on the piston, and measuring the The pressure P ₀ of the high pressure side and the pressure P _N at the Nth tooth of the labyrinth, send the above measured values to the data acquisition system, and the system calculates the above parameter values. The leakage of the labyrinth seal is:

in,

K=b/c, R is the gas constant, T ₀ is the gas temperature at the high-pressure side of the piston, P ₀ is the pressure at the high-pressure side of the piston, and P _N is the pressure at the Nth tooth of the labyrinth;

Where ε is the piston inlet and exhaust pressure ratio; n is the compressor speed; S is the compressor stroke, ψ, θ and γ are the fitting parameters, h is the radial gap consistent with the gap width c, D is the piston diameter, ν _u is the sound velocity of the gas before inhalation.

After adopting the present invention, when the labyrinth compressor is working, the gas on the compressed side of the piston tends to leak to the non-compressed side, and when a small amount of compressed gas leaks to the gap between the piston and the inner wall of the piston cavity, each labyrinth tooth cavity will form a throttling cavity , the pressure of the gas gradually decays through multiple throttling chambers until it is equal to the pressure on the non-compressed side. A pressure sensor is installed on the piston to detect the pressure value of the labyrinth throttling chamber and test the effect of the labyrinth throttling; A very small amount of the compressed gas may enter the measurement chamber, and the gas leakage flow rate can be detected by the flow sensor to know the leakage amount within a certain period of time, and the gas leakage test is conveniently realized.

Description of drawings

Fig. 1 is a structural representation of the present invention;

Fig. 2 is a schematic diagram of the piston structure;

Fig. 3 is an enlarged schematic view of the piston and the inner wall of the piston cavity.

detailed description

See Fig. 1, Fig. 2, shown in Fig. 3, a kind of sealing performance test device of labyrinth compressor, it comprises crankcase transmission box 1 and cylinder 2, and crankshaft transmission box 1 is provided with crankshaft 3, and crankshaft 3 passes through connecting rod transmission mechanism 4 Connect one end of the piston rod 5, the piston rod 5 is equipped with a piston 7 located in the piston chamber 6 in the cylinder 2, one end of the piston chamber 6 communicates with the intake passage 8 and the exhaust passage 9, and the cylinder 2 is provided with a The stuffing box, the stuffing box includes an upper stuffing box 10 and a lower stuffing box 11 located at both ends of the piston, the stuffing 12 is floatingly arranged in the stuffing box, the other end of the piston chamber 6 is connected to the measuring chamber 13, and the measuring chamber 13 is equipped with a flow sensor 14 and a pressure relief valve. valve 15.

Two pressure sensors 16 arranged axially staggered are installed on the side wall of the piston 7 . Since there is a pressure difference between the two ends of the piston, the measurement is performed by the two pressure sensors 16 .

Located at the other end of the piston rod 5, a casing 17 is installed on the cylinder 2, and a displacement sensor 18 is installed on the inner wall of the casing 17, which can detect the radial displacement of the piston rod 5 and understand the swinging situation of the piston.

The piston rod 5 is provided with a platform stage, and one end of the piston is against the step surface of the platform stage, and the other end is fixed by a lock nut 19 installed on the piston rod 5 .

The outer wall of the piston 7 is covered with a casing 20. The outer surface of the casing 20 and the inner wall of the piston chamber 6 are toothed in different sizes and there is a gap between the two. When a small amount of compressed gas leaks to the gap between the piston and the inner wall of the piston chamber, each The labyrinth tooth cavity will form a throttling cavity. Under a certain small gap, a very small part of the medium flows from the high-pressure side to the low-pressure side through each throttling point. When passing through each node, the gas converts pressure energy into kinetic energy. When After the gas enters the alveolar, due to the sudden expansion of the volume, the gas velocity drops rapidly (nearly zero), part of its kinetic energy is converted into heat energy, and the other part is converted into eddy current energy. After continuous and uniform throttling and the repeated action of the cogged vortex chamber, the pressure of the leaked gas is reduced to the pressure of the low pressure side to meet the airtightness requirements.

The piston 7 includes a middle shaft sleeve 7-1 for keying with the piston rod 5. The end of the middle shaft sleeve 7-1 is connected to the middle of the disc body 7-2, and the end of the disc body 7-2 is connected to the ring body 7-3. There is an empty space between the shaft sleeve 7-1 and the ring body 7-3, which plays a role in reducing weight. The middle shaft sleeve 7-1, the disk body 7-2, and the ring body 7-3 are integrally structured.

The casing 20 is fixed to the ring body by screws 21, which is convenient for installation and replacement. A pressure sensor installation hole 22 is provided on the side wall of the ring body 7-3 and the side wall of the casing 20.

The outer casing 20 can be replaced. On the one hand, when the outer casing 20 is severely worn, only the outer casing 20 needs to be replaced, and the internal piston body can continue to be used to reduce costs. On the other hand, when conducting tests, the outer casing 20 with different tooth shapes can be replaced Contrast experiments also reduced costs. Regulating valves and buffer devices are also provided on the exhaust side.

其中，

K＝b/c，R为气体常数、T₀为活塞高压侧气体温度，P₀为测量活塞高压侧压力的、P_N为迷宫第N齿处的压力；

其中ε为活塞进排气压比；n为压缩机转速；S为压缩机行程，ψ、θ和γ为拟合参数，h为径向间隙与间隙宽度c一致，D为活塞直径，ν_u为吸气以前的气体声速。A test method for sealing performance of a labyrinth compressor, which is characterized by measuring the gap length b, gap width c, and annular labyrinth gap cross-sectional area A between the piston and the inner wall of the piston chamber, measuring the tooth spacing B on the piston, and measuring the The pressure P ₀ of the high pressure side and the pressure P _N at the Nth tooth of the labyrinth, send the above measured values to the data acquisition system, and the system calculates the above parameter values. The leakage of the labyrinth seal is:

in,

K=b/c, R is the gas constant, T ₀ is the gas temperature at the high-pressure side of the piston, P ₀ is the pressure at the high-pressure side of the piston, and P _N is the pressure at the Nth tooth of the labyrinth;

Where ε is the piston inlet and exhaust pressure ratio; n is the compressor speed; S is the compressor stroke, ψ, θ and γ are the fitting parameters, h is the radial gap consistent with the gap width c, D is the piston diameter, ν _u is the sound velocity of the gas before inhalation.

The specific experimental process is given below:

Test Compressor Data Sheet

compressor speed 400～600r/min How to use cylinder volume Cover side single acting Piston diameter 250mm Piston stroke 90mm Import (exit) port Cp/Cv value 1.33 test medium Air import T=29℃; P=0.10133MPa(A) Export T≤150℃; P≤0.6MPa(A)

Carrying out the three-factor and three-level orthogonal test on the test device can effectively reduce the number of tests without reducing the test accuracy. The test plan arrangement is shown in Table 2.

Table 2 Labyrinth seal orthogonal test scheme

The test data is collected by the data acquisition system and calibrated and transformed with LabVIEW software. According to the test result data, Statistic software is used to fit the formula parameters to obtain

Substituting the above formula into the leakage calculation formula can calculate the corresponding leakage, and then compare the leakage with the actual value measured by the flow sensor. There will be a slight deviation between the two values, because the measurement of the flow sensor will also have errors. Therefore, if the calculated leakage and the actual measured value are within the agreed range, it can be determined that the two are consistent. According to the calculated leakage, the leakage at the piston can be understood, and the factors that affect the leakage can be understood according to the formula. , the main influences on the leakage are as follows:

1. Maze shape

The geometry and size of the labyrinth seal cavity have a great influence on the effect of the labyrinth seal. It directly affects the strength of the vortex formed in the cavity, that is, it affects the degree of kinetic energy converted into heat energy in the cavity. Two important geometric parameters of the cavity are the cavity depth and the cavity width, and the ratio of the two, that is, the aspect ratio, has an optimal value.

The tooth shape of the labyrinth seal is an important parameter affecting the structure of the labyrinth. The common tooth shapes mainly include: rectangular teeth, trapezoidal teeth, triangular teeth, etc. Considering the processing conditions and experience, the labyrinth compressor generally adopts isosceles trapezoidal teeth to form an equilateral triangle labyrinth cavity.

2. Gap width

The gap width between the sealing pairs has a great influence on the performance of the labyrinth seal. Theoretically, in order to reduce the leakage, the gap width of the labyrinth should be as small as possible, but in practice, too small gap width is disadvantageous. If the inertial force is unbalanced when the machine is running, the piston will deflect. At this time, if the gap width is too small, it will cause contact wear between the piston and the cylinder, which will not only lose the sealing effect, but also damage the parts; in addition, due to the material performance of the seal Differences (such as aluminum piston matching cast iron cylinder, graphite filler matching steel piston rod), if the expansion is too large, the original gap will be filled and severe friction will occur with the wall surface, which will lead to aggravated vibration and increased temperature, which will cause the seal and the wall surface to be affected. Severe damage may even cause the failure of the whole machine. Therefore, on the premise that the level of processing and assembly, operating conditions and economy allow, the gap width can be appropriately increased. In general, in order to obtain the best clearance, the labyrinth compressor has to complete a "run-in" process. By slowly increasing the compression ratio so that the piston gradually heats up and expands, the running-in process causes the cylinder wall and the end of the piston labyrinth to come into contact, thus creating an optimal clearance.

3. Number of teeth in the labyrinth

From the theory of energy dissipation in the labyrinth cavity, the longer the sealing length, the better the sealing effect will be. However, in practice, the length of the sealing pair is limited by many conditions. The length design must be based on the stable performance of the whole machine and economic performance. good basis. Literature [2] pointed out that there is an optimal number of teeth under the condition of a given sealing length, so that the leakage is the smallest.

4. Compressor speed

The speed is an extremely important performance parameter of the labyrinth compressor, and its improper selection will bring some unfavorable factors to the labyrinth compressor. On the basis of ensuring the reliability and high efficiency of the compressor, increasing the speed can not only reduce the volume and weight of the machine, thereby saving processing costs and materials, but also significantly improve the performance of the labyrinth seal. The higher the speed, the smaller the leakage.

According to the requirements of leakage, each parameter can be adjusted to obtain the standard leakage, which can provide data reference for unit design.

Claims (7)

1. The utility model provides a labyrinth compressor sealing performance test device, its includes crankcase transmission case and cylinder, be provided with the bent axle in the crankshaft transmission case, the bent axle passes through connecting rod drive mechanism and connects piston rod one end, install on the piston rod and be located the piston in the cylinder piston chamber, piston chamber upper end intercommunication inlet channel and exhaust passage, be provided with in the cylinder with piston rod complex gland packing, be provided with the filler in the gland packing, the piston surface with piston intracavity wall leaves the clearance for profile of tooth and between the two, its characterized in that, piston chamber lower extreme end intercommunication leakage gas measurement chamber, measure the chamber and install flow sensor, install pressure sensor on the piston lateral wall, measure the chamber and still install relief valve and manometer.

2. The labyrinth compressor sealing performance test device as claimed in claim 1, wherein the stuffing box comprises an upper stuffing box and a lower stuffing box which are arranged at two ends of the piston, and the stuffing is arranged in the stuffing box in a floating manner.

3. The labyrinth compressor sealing performance test device as claimed in claim 1, wherein the piston rod is provided with a stage, the lower end of the piston abuts against a step surface of the stage, and the upper end of the piston is fixed by a lock nut mounted on the piston rod.

4. The labyrinth compressor sealing performance test device as claimed in claim 1, wherein the outer wall of the piston is sleeved with a housing, and the outer surface of the housing and the inner wall of the piston cavity are in tooth shapes with different sizes.

5. The labyrinth compressor sealing performance test device as claimed in claim 1, wherein the piston includes a middle shaft sleeve, the middle shaft sleeve is connected to the middle of the disk body, the disk body is connected to the ring body, a vacant area is formed between the middle shaft sleeve and the ring body, and the middle shaft sleeve, the disk body and the ring body are of an integrated structure.

6. The labyrinth compressor sealing performance test device as claimed in claim 5, wherein the casing is fixed to the ring body through screws, and pressure sensor mounting holes are formed in the side wall of the ring body and the labyrinth tooth bottoms of the side wall of the casing.

7. The labyrinth compressor sealing performance test method is characterized by measuring the gap length B, the gap width c and the annular labyrinth gap cross-sectional area A between a piston and the inner wall of a piston cavity, measuring the tooth space B on the piston and measuring the pressure P of the high-pressure side of the piston ₀ Pressure P at the Nth tooth of the labyrinth _N And sending the measured value to a data acquisition system, calculating the parameter value by the system, and calculating the leakage amount of the labyrinth seal:

wherein,

k = b/c, R is the gas constant, T ₀ Is the gas temperature, P, on the high-pressure side of the piston ₀ For measuring the high-side pressure of the piston, P _N The pressure at the Nth tooth of the labyrinth;

wherein epsilon is the air intake-exhaust pressure ratio of the piston; n is the rotation speed of the compressor; s is the compressor stroke, psi, theta and gamma are fitting parameters, h is the radial clearance is consistent with the clearance width c, D is the piston diameter, v _u The velocity of the gas prior to inspiration.

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