Compressor pressure setting for performance adjustment The compressor manufacturer provides a reference value for the exhaust pressure in the “Technical Parameter Summary Tableâ€. The user should indirectly reflect the intake pressure value according to the exhaust pressure operating value (common). The air pressure is set to ensure control of the inlet guide vanes. After artificial adjustment of the working conditions, the intake pressure value should be reset.
The schematic diagram of the compressor anti-surge control when the anti-surge control is implemented is as shown. If the user re-values ​​the exhaust pressure and intake pressure, it should be based on the analysis. The middle shadow portion is the work area, which is composed of line1, line2, and line3.
Determined by the exhaust pressure/intake pressure, the exhaust pressure (control bypass valve) is generally set to 1105% to 111% of the design value; the set value of the intake pressure (control bypass valve) determines whether the safety zone is Composed of line3.
Line2 is the minimum opening (absolute) of the inlet guide vanes, determined by the flow adjustment range, ie the starting position.
Line3 is a surge protection line. Under the current control method, it is generally not desirable for the working area to be controlled by line3. Therefore, if the conditions permit, the intake pressure setting value is increased, that is, the line1 is lowered; if the condition is not allowed, the exhaust pressure operating value should be increased to the inlet guide. The minimum opening (relative) limit of the leaf requires the following: Q>Q minimum opening (Pd≤Pd')Q>a(Pd-Pd')+Q minimum opening (Pd>Pd') where: Pd' It is the exhaust pressure corresponding to the intersection of line2 and line3 (the inlet state is the lowest state at this time); Q is the gas flow rate; a is the Q corresponding to the intersection of Q-line2 and line3 corresponding to the intersection of line1 and line3)/(intersection of line1 and line3) Corresponding Pd-line2, line3 corresponding to Pd).
The inlet guide vanes are separately controlled. If the air supply capacity of the air separation unit is not balanced with the air supply volume of the compressor, the intake pressure will fluctuate. Through the inlet guide vane control, the compressor air supply is changed to achieve the purpose of balancing the intake pressure. When the intake pressure drops, the air supply capacity of the air separation unit is smaller than the air supply volume of the compressor, the inlet guide vane is closed, and the air supply volume of the compressor is decreased to achieve the balance air volume; if the air supply capacity of the air separation unit is much smaller than the air supply volume of the compressor, the inlet The guide vane has been closed to a minimum. At this time, the bypass valve is opened, and the bypass air volume is added to supplement the air supply capacity of the air separation device to achieve a balanced air volume; if the bypass amount is insufficient to supplement the air supply capacity of the air separation device, the interlocking parking is performed.
When the intake pressure rises, the air supply capacity of the air separation unit is greater than the air supply volume of the compressor, the inlet guide vanes are opened, the air supply volume of the compressor is increased, and the balance air volume is achieved; the air supply capacity of the air separation unit is much larger than the air supply volume of the compressor, and the inlet guide The leaf has been opened to the maximum, the inlet guide vane is out of control, and only the air supply of the air separation unit is artificially adjusted; or an alarm is provided to remind the person to adjust the air supply capacity of the air separation unit.
Assume that the inlet pressure design value is 12 kPa, the inlet pressure is less than 10 kPa, then the inlet guide vanes are controlled; if the intake pressure is less than 6 kPa, the bypass valve is controlled; if the exhaust pressure set value is higher than the actual value of the exhaust pressure (ie, the inlet The guide vane is controlled separately), the bypass valve is separated from the exhaust pressure control. At this time, the inlet guide vane and the bypass valve have the following five states: (1) When Pj>10 kPa, the inlet guide vanes are fully open, and the bypass valve is fully closed. (2) When Pj ≈ 10 kPa, the inlet guide vanes are controlled, the bypass valve is fully closed; (3) when 6 kPa The bypass valve control diagram assumes that the bypass valve is controlled separately, that is, the inlet guide vane does not operate, then Pj ≠10 kPa, there are the following four states: (1) When Pj > 10 kPa, the exhaust pressure control bypass valve; user The required gas volume decreases, the exhaust pressure rises, the bypass valve opens, the compressor air supply increases, and the pressure ratio (Pd/Pj) decreases. The following three conditions occur: If the intake pressure rises, the exhaust pressure rises, equal to or Below the set value; the intake pressure rises and the exhaust pressure rises above the set value. This condition is determined by the performance curve, which often occurs during medium exhaust pressure, causing logic errors. Only artificially reduce the supply of air separation equipment. The gas volume reaches or falls below the set value; the intake pressure does not change or the intake pressure drops, and the exhaust pressure drops below the set value. (2) when 6kPa The inlet vane and the bypass valve simultaneously control the inlet guide vane and the bypass valve to be simultaneously controlled, at which time the intake pressure is constant. When the user needs to change the air volume, the air supply capacity of the air separation equipment will not self-adjust, and only the air supply capacity of the air separation equipment is artificially changed. The compressor can only self-adjust by the intake pressure and the air supply capacity of the air separation unit. The exhaust pressure is determined by the performance curve (as shown). When the inlet guide vane and the bypass valve are simultaneously controlled, the exhaust pressure performance curve (a), the bypass amount (Q3-Q1) is greater than the constant pressure increase of the open guide vane (Q2-Q1), when the vane and the bypass valve are opened The exhaust pressure drops. In (b), the bypass amount (Q3-Q1) is smaller than the constant pressure increase amount (Q2-Q1) of the open guide vane. When the guide vane and the bypass valve are opened, the exhaust pressure rises and the logic is incorrect. Therefore, it can be concluded that the exhaust pressure drop can be achieved when the exhaust pressure set value is greater than a certain value. Improvements in Control (1) Improvement of Uncontrolled Flow When the surge line (line3) controls the minimum value of the inlet guide vane, the inlet guide vanes are controlled by the exhaust pressure to achieve performance adjustment. Through the intake pressure (because the intake pressure has an effect on line3), the pressure ratio (Pd/Pj) controls the bypass valve; the pressure ratio controls the vent valve to achieve anti-surge control. (2) Improvement of control flow The compressor performance curve is used to achieve complete control.
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