CN113266558A

CN113266558A - Load signal linearization processing method for stepless air volume adjustment of compressor

Info

Publication number: CN113266558A
Application number: CN202110613702.7A
Authority: CN
Inventors: 李泉泉; 常海城
Original assignee: Wuxi Kangzi Compressor Fittings And Systems Co ltd
Current assignee: Wuxi Kangzi Compressor Fittings And Systems Co ltd
Priority date: 2021-06-02
Filing date: 2021-06-02
Publication date: 2021-08-17

Abstract

The invention discloses a Control signal linearization processing method of a stepless air quantity regulating system, wherein an Out value of the operation of a reciprocating compressor is given through a PIC controller, and an executor of the stepless air quantity regulating system receives a Control value of the operation; each Out value has a crank angle corresponding directly to

(ii) a Each Control value has a directly corresponding piston stroke S; based on the piston stroke S and

the proportional relationship of (1) is the exhaust gas quantity and

are in direct proportion, and the corresponding relation between the Out value and the Control value is established according to the direct proportion relationAnd calibrating an Out value and establishing an interval linear relation between the Out value and a Control value corresponding to the Out value. The control signal linearization processing method improves the actual control effect of the stepless air quantity regulating system on the compressor, so that the deviation of the actual control value and the theoretical value is in a reasonable range. Meanwhile, the capacity improvement of the stepless air volume adjusting system on adjusting precision and response speed is realized, and the reciprocating compressor air displacement adjusting system has great advantages in adjusting the air displacement of the reciprocating compressor.

Description

Load signal linearization processing method for stepless air volume adjustment of compressor

Technical Field

The invention relates to the field of control methods of engine systems, in particular to a control signal linearization processing method of a stepless air quantity regulating system.

Background

Petrochemical and chemical high-power reciprocating compressors are equipped with valve-controlled gas quantity stepless regulation systems, energy conservation is realized and the control performance of a process system is improved by adopting the basic principle of delayed closing of an air inlet valve, the basic principle is accepted by more and more using units, but how to match the specific characteristics of a specific compressor in actual use, particularly the fitting of load percentage and specific exhaust gas quantity, is still a continuously-explored subject.

At present, the quantity of gas quantity stepless regulating systems of domestic large reciprocating compressor units is increased more and more, and the regulating principle is that an air inlet valve is forcibly opened in a partial stroke of a compression stroke to realize gas backflow, and only the gas quantity which is actually needed is compressed. The P-V (pressure-volume) indicator diagram of a reciprocating compressor is a curve reflecting the variation of the gas pressure in the cylinder when the piston is at different positions in one working cycle (360 degrees of crankshaft rotation), and is also called as a gas diagram. A series of analysis and calculation can be carried out on the working process of the compressor according to the P-V diagram, and for the gas quantity stepless regulation system, the indicated power of the compressed gas can be calculated according to the area of the P-V diagram. As shown in figure 3, under the action of the stepless air quantity regulating system, the C-C '-D' stage of the compression stroke is not used for compressing air, and the compressor indication power is saved as can be seen visually from the P-V indicator diagram.

Generally, a reciprocating compressor is designed according to a specific operation condition required by a process, but in an actual operation, the operation condition is difficult to be completely unchanged, that is, the compressor is actually operated under a variable working condition. The variable working condition of the compressor means that other parameters can be correspondingly changed when only one of the operating conditions of the compressor, namely the air inlet pressure, the air inlet temperature, the air outlet pressure or the air displacement of each stage is changed, so that the original coordination and balance relationship among the stages of the compressor is destroyed until a new coordination and balance relationship is established again. For a single-stage compression reciprocating compressor, the parameters involved in the coordination balance relationship are relatively small, and the time required for reestablishment is short. For a multi-stage compression reciprocating compressor, the gas is introduced into several cylinder strokes, compressed in sequence and then introduced into an inter-stage cooler for cooling before entering the next stage of compression. In practice, it is sought to cool the gas during compression, i.e. the compression is divided into a plurality of stages, and after each stage of compression, the gas is cooled and then further compressed, so as to improve the efficiency and reduce the power consumption.

The reflux regulation mode of the existing compressor unit is that the opening of a reflux valve is automatically calculated by a PID (proportion integration differentiation) controller according to the pressure set values of inlets and outlets of all stages, but when the working condition is changed, the ratio of the opening of the reflux valve to the reflux air quantity is also changed, so that when the inlet pressure fluctuates frequently, the pressure and the temperature of all stages of the compressor fluctuate for a long time. According to the data records of inlet pressure and flow in a period of time, a newly-added compressor air quantity stepless regulation system (DidroCOM) automatically controls PID parameters to optimize, so that the change of inlet pressure can be quickly responded, and the time for reaching new balance is shortened.

After the DidroCOM automatic control system is used on the compressor unit, the required air quantity is automatically calculated through the PIC controller, and high adjusting precision and high response speed are achieved. However, when the displacement of the reciprocating compressor is adjusted, the compressor load percentage calculated by the PIC is found to have a certain deviation from the actual displacement percentage, and the analysis is carried out because the stroke division of the compressor piston by the displacement stepless adjusting system is the average division measured according to the time of 0-360 degrees of the crank angle, and the stroke of the piston is actually non-time-uniform.

Disclosure of Invention

The invention aims to: the control signal linearization processing method for the stepless air volume regulating system solves the problem of establishing the linear relation between the PIC control signal and the receiving feedback of the stepless air volume regulating system.

The technical scheme of the invention is as follows: the steps of finding the corresponding relation between the Out value output by the PIC controller and the Control value received by the air quantity regulating system actuator are as follows:

1) the crank starting and stopping angles of all stages in the 100% air quantity state are determined according to the parameters (mainly air inlet/outlet pressure/clearance volume) of the compressor, and the initial value of the crank angle theta is obtained through the starting and stopping angles.

2) During the exhaust process, the stroke of the piston is proportional to sin (theta) every 1 DEG of the crankshaft, so the whole exhaust amount is proportional to

Thus, a corresponding relation curve between the Out value output by the PIC controller and the Control value received by the air quantity regulating system actuator is obtained.

3) In consideration of the equipment limitation of practical use occasions, the method calibrates the Out value output by the PIC controller according to class levels, each calibration point corresponds to a Control value, and a broken line is used for replacing a curve to convert the nonlinear relation into an interval linear relation.

The invention has the advantages that:

1. the actual control effect of the stepless air quantity adjusting system on the compressor is improved, and the deviation of the actual control value and the theoretical value is in a reasonable range.

2. Meanwhile, the capacity improvement of the stepless air volume adjusting system on adjusting precision and response speed is realized, and the reciprocating compressor air displacement adjusting system has great advantages in adjusting the air displacement of the reciprocating compressor.

Drawings

The invention is further described with reference to the following figures and examples:

FIG. 1 is a graph showing a relationship between an Out value outputted from a PIC controller and a Control value received by an actuator of a gas-amount stepless regulation system;

FIG. 2 is a diagram of four stages of operation of the reciprocating compressor;

FIG. 3 is a P-V indicator diagram with stepless regulation of gas amount;

Detailed Description

Example (b):

during the operation of the reciprocating compressor controlled by the stepless air flow regulating system, the compressor is changed in work by adding a certain load, such as increasing the oil injection amount, and the stepless air flow regulating system can obtain a corresponding feedback signal, such as the air displacement. In the process, different air displacement corresponds to different crank angles, namely, each crank angle has an air displacement adjusting value. A load value is output through an electric control unit, namely a PIC controller, and the load value can control the included angle of the crank, so that different exhaust volumes are controlled. Therefore, the load value output by the PIC controller and the feedback value obtained by the gas quantity stepless regulation system can be represented in a well-designed display system, and corresponding changes can be visually represented only through the linear relation between the load value and the feedback value.

In the actual process, the stroke division of the compressor piston by the air quantity stepless regulation system is an average division according to the time measurement of 0-360 degrees of the crank angle, and the stroke of the piston is actually non-time-uniform.

The crank-link ratio is the crankshaft length r/link length L.

The displacement is equal to the piston stroke S × the piston area.

Specifically, the Out value output by the PIC controller can correspond to 0-100 average equal parts of a partial rotation angle, the CONTROL value received by the air quantity stepless regulating system actuator can correspond to 0-100 average equal parts of a partial stroke, and the relationship between the Out value and the CONTROL value is nonlinear.

Therefore, the corresponding relationship between the Out value output by the PIC controller and the Control value received by the air quantity regulating system actuator can be obtained by the following steps:

firstly, the crank starting and stopping angles of each stage in the 100% air quantity state are determined according to the parameters (mainly the air inlet/outlet pressure/clearance volume) of the compressor, and the initial value of the crank angle theta is obtained through the starting and stopping angles, as shown in fig. 2.

Second, in the exhaust process, the stroke of the piston is proportional to sin (theta) every 1 DEG of the crankshaft, so the whole exhaust amount is proportional to

Thus, the corresponding relation between the Out value output by the PIC controller and the Control value received by the air quantity regulating system actuator is obtained, and the visual representation mode can be represented by establishing a coordinate system and drawing a corresponding relation curve, as shown in FIG. 1.

Thirdly, considering the equipment limitation of the actual use occasion, the method calibrates the Out value output by the PIC controller according to the class level of 0-10-20-30-40-50-60-70-80-90-100, each calibration point corresponds to a Control value, and uses a broken line to replace a curve to convert the nonlinear relation into the interval linear relation.

The specific calibrated class level is determined according to an Out value output by the PIC controller, and can be based on a specific point value, such as 200cc fuel injection quantity, or an interval range, such as the current quantity of 4-6 mA analog quantity.

A preferred embodiment is chosen for illustration:

table 1 shows the correspondence between the Out value output by the PIC controller and the Control value obtained by the stepless air volume adjusting system receiver according to the Control signal linearization processing method of the reciprocating compressor stepless air volume adjusting system:

table 1: interval linear table of OUT value and Control value

After the interval linearization processing is adopted, the coincidence degree of the Out value input on the operation chamber DCS and the on-site actual exhaust gas volume is greatly improved. The following table 2 is a corresponding relationship between the Out value output by the PIC controller and the actual gas amount:

NO	PIC output value	Actual gas quantity value Nm3/hr	Actual output load
				1	0％	0	0％
2	10％	4840	11％
				3	20％	9240	21％
4	30％	14080	32％
				5	40％	18480	42％
6	50％	21560	49％
				7	60％	25520	58％
8	70％	29920	68％
				9	80％	35200	80％
10	90％	39160	89％
				11	100％	43120	98％

Table 2: OUT value and actual gas quantity corresponding table

From a comparison of the above data, it is evident that: the actual control effect of the DidroCOM stepless air quantity regulating system after linearization on the actual compressor is basically consistent with the theoretical analysis, and the deviation is within a reasonable range. The DidroCOM stepless air quantity adjusting system realizes higher adjusting precision and higher response speed, and has good advantages in adjusting the specific displacement of the reciprocating compressor.

The system at this moment is completely in accordance with the prediction after long-time operation, the unit is stable in operation, all parameter indexes are normal, and the process index is improved to a certain extent compared with that before the system is not used. The load of the current unit is basically maintained between 70% and 80% according to the process requirements, the return valve of the hydrogen outlet is completely closed, the matching amount of hydrogen is accurate, and convenience and guarantee are brought to the smooth operation of the whole set of device. The measured values of the relationship between the compressor load and the compressor current are shown in table 3.

Parameter(s)	100% load of system	80% load of the system
			Amount of hydrogen refluxed (Nm3/h)	9000	0
Current value (A)	250	200
			Power (KW)	4400	3450

TABLE 3 relationship table of load and power consumption

According to the data analysis, the load of the unit can be adjusted at will according to the process requirement after the unit uses the DidroCOM gas quantity stepless regulation system after linear processing, the load is calculated according to the current 80% running load, the backflow of hydrogen can be effectively reduced by about 9000Nm3/h, and the current is reduced from 250A to 200A. Calculating according to 8000 hours of annual operation, and saving the electric quantity by about 760 ten thousand KW.h; the current electric charge is 0.6 yuan/KW.h.

The foregoing embodiments are merely illustrative of the principles and utilities of the present invention and are not intended to limit the invention. Any person skilled in the art can modify or change the above-mentioned embodiments without departing from the spirit and scope of the present invention. Accordingly, it is intended that all equivalent modifications or changes which can be made by those skilled in the art without departing from the spirit and technical concepts disclosed herein be covered by the appended claims.

Claims

1. A linear processing method for Control signals of a stepless air quantity regulating system is characterized in that an Out value of reciprocating compressor operation is given through a PIC controller, and an actuator of the air quantity stepless regulating system receives an operation Control value; the method is characterized in that: each Out value has a directly corresponding crank included angle theta; each Control value has a directly corresponding piston stroke S; based on the proportional relation between the piston stroke S and sin (theta) in the exhaust process, the exhaust amount is equal to

The Out value and the Control value are in direct proportion, the corresponding relation between the Out value and the Control value is established according to the direct proportion relation, the Out value is calibrated, and the interval linear relation between the Control value and the corresponding Out value is established.

2. The control signal linearization processing method of the stepless air volume regulating system as claimed in claim 1, wherein: based on the corresponding relationship between the Out value and the Control value, the given quantity of the Out value is calibrated in class level, and the Out value of each class level corresponds to the corresponding Control value.

3. The control signal linearization processing method of the stepless air volume regulating system as claimed in claim 2, wherein: and establishing a rectangular coordinate system according to the Control value and the calibrated Out value, and sequentially connecting corresponding points of the Out value and the corresponding Control value by using a broken line.

4. The control signal linearization processing method of the stepless air volume regulating system as claimed in claim 1 or 2, characterized in that: the initial value determination method of the crank angle theta comprises the following steps: and determining the starting and stopping angles of the included angle of the crank of the reciprocating compressor at each stage under the state of 100% air quantity according to the parameters of the compressor.

5. The control signal linearization processing method of the stepless air volume regulating system as claimed in claim 4, wherein: the compressor parameters are intake pressure, exhaust pressure and clearance volume.

6. The control signal linearization processing method of the stepless air volume regulating system as claimed in claim 4, wherein:

the proportional relation between the piston stroke S and sin (theta) is expressed as:

the crank-link ratio is the crankshaft length r/link length L.