Magnetic suspension compressor outlet pressure adjusting system and method

Abstract

The invention relates to the technical field of mechanical equipment, in particular to a magnetic levitation compressor outlet pressure adjusting system and method.The magnetic levitation compressor outlet pressure adjusting system comprises an outlet pressure sensor, a controller, an axial magnetic levitation bearing and an axial displacement sensor, the outlet pressure sensor is arranged at an outlet of a compressor, and the controller is connected with the outlet pressure sensor; the clearance between the impeller blade tip and the impeller housing is indirectly adjusted by adjusting the clearance of the axial magnetic suspension bearing in the magnetic suspension compressor, so that the purpose of adjusting the outlet pressure of the compressor is achieved, and the purpose of adjusting the outlet pressure of the compressor can be achieved only through the bearing part of the compressor and a corresponding control program. According to the compressor, valves or mechanical parts and speed regulation devices do not need to be additionally arranged, the structural complexity and the machining and purchasing cost are reduced, and the technical problems that in the prior art, when pressure regulation is conducted on the compressor, the structure is complex, and the equipment cost or the control difficulty is increased are solved.

Description

Technical Field

[0001] The present invention relates to the technical field of mechanical equipment, and in particular to a system and method for regulating the outlet pressure of a magnetic suspension compressor. Background Art

[0002] Compressors are important mechanical equipment in pharmaceutical and petrochemical production. In many process links of petroleum, chemical and pharmaceutical production, compressors are required to provide stable outlet pressure, that is, the compressors are required to perform equal pressure regulation. Traditional compressor pressure regulation methods include compressor outlet throttling, compressor inlet throttling, proportional regulation, the use of rotatable inlet guide vane adjustment and the method of changing the compressor speed for adjustment.

[0003] However, when the above method is used to adjust the pressure of the compressor, there are problems such as complex structure, increased equipment cost or control difficulty. Summary of the invention

[0004] The purpose of the present invention is to provide a magnetic levitation compressor outlet pressure regulation system and method, aiming to solve the technical problems in the prior art of pressure regulation of the compressor, such as complex structure, increased equipment cost or control difficulty.

[0005] To achieve the above-mentioned object, the present invention adopts a magnetic suspension compressor outlet pressure regulating system, comprising an outlet pressure sensor, a controller, an axial magnetic bearing and an axial displacement sensor, wherein the outlet pressure sensor is arranged at the outlet of the compressor, the controller is connected to the outlet pressure sensor, the axial magnetic bearing is connected to the controller, and the axial displacement sensor is also connected to the controller;

[0006] The controller is used to collect data from the outlet pressure sensor and compare it with the set pressure;

[0007] The controller is also used to control the axial magnetic bearing.

[0008] The present invention also provides a method for regulating the outlet pressure of a magnetic levitation compressor, which is applied to the outlet pressure regulating system of the magnetic levitation compressor as described above, and comprises the following steps:

[0009] Step 1, the controller collects data from the outlet pressure sensor and compares it with the set pressure;

[0010] Step 2: If the result of the comparison in step 1 is that the data of the outlet pressure sensor is greater than the set pressure value, the controller obtains the value of the axial displacement that needs to be adjusted according to the inverse operation of formula 1, and outputs a driving current signal to the axial magnetic bearing. The controller adjusts the magnitude of the axial bearing control force by adjusting the current output to the axial bearing coil, thereby adjusting the position of the rotor shaft;

[0011] Step three, the controller collects the value of the axial displacement sensor to calculate whether the displacement adjustment value is the calculated value according to the formula in step two, thereby completing the adjustment of the outlet pressure of the magnetic levitation compressor.

[0012] Wherein, formula 1 in step 2 is:

[0013]

[0014] Among them, after the adjustment is completed in step three, due to the idealized setting of formula 1, it is necessary to further control the size of the outlet pressure through the PID control algorithm, so as to finally achieve the purpose of constant pressure gas supply or pressure regulation according to process requirements.

[0015] The outlet pressure regulating system and method of the magnetic suspension compressor of the present invention can be known from the structure of the magnetic suspension compressor that the position of the drive shaft can be adjusted in the axial direction by controlling the magnitude of the control force of the axial magnetic suspension bearing. Since the impeller of the magnetic suspension turbine compressor is directly mounted on the drive shaft, the change of the position of the drive shaft drives the change of the impeller position, so that the gap between the impeller blade tip and the impeller cover is changed.

[0016] Therefore, the present application achieves the purpose of adjusting the outlet pressure of the compressor by adjusting the gap of the axial magnetic bearing in the magnetic levitation compressor to indirectly adjust the gap between the impeller tip and the impeller cover. The advantage of the present invention is that it can be completed only by the bearing components of the compressor itself and the corresponding control program, without the need for additional valves or mechanical components and speed control devices, thereby reducing the structural complexity and processing and procurement costs, and solving the technical problems in the prior art of complex structure, increased equipment cost or control difficulty when adjusting the pressure of the compressor. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0018] Figure 1 It is a structural schematic diagram of the outlet pressure regulating system of the magnetic suspension compressor of the present invention.

[0019] Figure 2 It is a principle block diagram of the outlet pressure regulating system of the magnetic suspension compressor of the present invention.

[0020] 1- outlet pressure sensor, 2- controller, 3- axial magnetic bearing, 4- axial displacement sensor. DETAILED DESCRIPTION

[0021] Embodiments of the present invention are described in detail below, examples of which are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are intended to be used to explain the present invention, and should not be construed as limiting the present invention.

[0022] See also Figure 1 and Figure 2 , Figure 1 is a structural schematic diagram of the outlet pressure regulating system of the magnetic suspension compressor of the present invention, Figure 2 It is a principle block diagram of the outlet pressure regulating system of the magnetic levitation compressor of the present invention. The present invention provides an outlet pressure regulating system and method of the magnetic levitation compressor: comprising an outlet pressure sensor 1, a controller 2, an axial magnetic bearing 3 and an axial displacement sensor 4, wherein the outlet pressure sensor 1 is arranged at the outlet of the compressor, the controller 2 is connected to the outlet pressure sensor 1, the axial magnetic bearing 3 is connected to the controller 2, and the axial displacement sensor 4 is also connected to the controller 2;

[0023] The controller 2 is used to collect data from the outlet pressure sensor 1 and compare it with the set pressure;

[0024] The controller 2 is also used to control the axial magnetic bearing 3 .

[0025] In this embodiment, it can be seen from the structure of the magnetic suspension compressor that the position of the drive shaft can be adjusted in the axial direction by controlling the magnitude of the axial magnetic suspension bearing control force. Since the impeller of the magnetic suspension turbine compressor is directly mounted on the drive shaft, the change in the position of the drive shaft drives the change in the position of the impeller, so that the gap between the impeller blade tip and the impeller casing is changed;

[0026] Therefore, the present application achieves the purpose of adjusting the outlet pressure of the compressor by indirectly adjusting the gap between the impeller blade tip and the impeller cover by adjusting the gap of the axial magnetic bearing 3 in the magnetic levitation compressor. The advantage of the present invention is that it can be accomplished only by the bearing components of the compressor itself and the corresponding control program, without the need for additional valves or mechanical components and speed control devices, thereby reducing the structural complexity and processing and procurement costs.

[0027] The present invention also provides a method for regulating the outlet pressure of a magnetic levitation compressor, which is applied to the outlet pressure regulating system of the magnetic levitation compressor as described above, and comprises the following steps:

[0028] Step 1: According to the centrifugal compressor principle and experiments, the effect of the gap between the impeller and the impeller casing of a single-stage centrifugal compressor on the compression work of the compressor is shown in Formula 1:

[0029]

[0030] Where: W0 is the compression work when the gap between the impeller and the impeller casing is 0; c1 is the gap between the impeller and the casing; W1 is the theoretical compression work after the gap increases to c1; h0 is the height of the compressor impeller blade;

[0031] Step 2: According to the compressor principle and Bernoulli equation, the increase in both dynamic pressure and static pressure of the compressed gas is due to the increase in flow velocity when the fluid flows through the impeller. If the pressure increase coefficient is set to λ1, the following mathematical model formula 2 can be established:

[0032]

[0033] Where: P2 is the pressure after supercharging; P1 is the inlet pressure; ρ is the gas density; δ is the impeller speed;

[0034] Step 3: The compression process of the compressor is a variable process with loss and heat exchange with the outside world. The compression work W of the variable process P Formula 3:

[0035]

[0036] Step 4: Combining equations 2 and 3, we can get the compression work as equation 4:

[0037]

[0038] Step 5: Set the tip clearance to increase d c becomes c2, and the theoretical compression work becomes W2. Combining equation 1, we can get equation 5:

[0039]

[0040] Where: a is the correction coefficient obtained by experiment;

[0041] Step 6: According to formula 4, when the tip clearance changes, the compression work W2 is formula 6:

[0042]

[0043] Step 7: Since the temperature does not change much after the tip clearance changes, T1 = T2 by default. Combining equations 4, 5, and 6, we can get equation 7:

[0044]

[0045] Step 8, the controller 2 collects data from the outlet pressure sensor 1 and compares it with the set pressure;

[0046] Step nine, if the result of the comparison in step eight is that the data of the outlet pressure sensor 1 is greater than the set pressure value, the controller 2 obtains the value of the axial displacement that needs to be adjusted according to the inverse operation of the formula in step seven, and outputs a driving current signal to the axial magnetic bearing 3. The controller 2 adjusts the magnitude of the axial bearing control force by adjusting the current output to the axial bearing coil, thereby adjusting the position of the rotor shaft;

[0047] Step 10, the controller 2 collects the value of the axial displacement sensor 4 to calculate whether the displacement adjustment value is the calculated value according to the formula in step 2;

[0048] Step 11. After the adjustment is completed, the outlet pressure is further controlled by the PID control algorithm, ultimately achieving the purpose of constant pressure gas supply or pressure regulation according to process requirements.

[0049] In the present invention, through Formula 7, the change of the boost coefficient when the blade tip clearance C changes can be obtained, and then the change of the compressor outlet pressure after the blade tip clearance changes can be obtained. According to Formula 7, if the compressor outlet pressure needs to be adjusted, it is sufficient to adjust the value of the blade tip clearance C within the adjustment range.

[0050] In practical applications, the above mathematical model has idealized settings, so a PID control algorithm is added to the control system so that the outlet pressure can be adjusted more accurately.

[0051] What is disclosed above is only a preferred embodiment of the present invention, and it certainly cannot be used to limit the scope of rights of the present invention. Ordinary technicians in this field can understand that all or part of the processes of the above embodiment and equivalent changes made according to the claims of the present invention still fall within the scope of the invention.

Claims

1. A magnetic levitation compressor outlet pressure regulating system, characterized in that: It includes an outlet pressure sensor, a controller, an axial magnetic bearing and an axial displacement sensor, wherein the outlet pressure sensor is arranged at the outlet of the compressor, the controller is connected to the outlet pressure sensor, the axial magnetic bearing is connected to the controller, and the axial displacement sensor is also connected to the controller; The controller is used to collect data from the outlet pressure sensor and compare it with the set pressure; The controller is also used to control the axial magnetic bearing.

2. A method for regulating the outlet pressure of a magnetic levitation compressor, applied to the outlet pressure regulating system of the magnetic levitation compressor as claimed in claim 1, characterized in that: The steps include: Step 1, the controller collects data from the outlet pressure sensor and compares it with the set pressure; Step 2: If the result of the comparison in step 1 is that the data of the outlet pressure sensor is greater than the set pressure value, the controller obtains the value of the axial displacement that needs to be adjusted according to the inverse operation of formula 1, and outputs a driving current signal to the axial magnetic bearing. The controller adjusts the magnitude of the axial bearing control force by adjusting the current output to the axial bearing coil, thereby adjusting the position of the rotor shaft; Step three, the controller collects the value of the axial displacement sensor to calculate whether the displacement adjustment value is the calculated value according to the formula in step two, thereby completing the adjustment of the outlet pressure of the magnetic levitation compressor.

3. The method for regulating the outlet pressure of a magnetic levitation compressor according to claim 2, characterized in that: Formula 1 in step 2 is:

4. The method for regulating the outlet pressure of a magnetic levitation compressor according to claim 3, characterized in that: After the adjustment is completed in step three, the outlet pressure is controlled by the PID control algorithm based on formula 1.

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