Patent ID: 11953006
Assignee: TYCO FIRE & SECURITY GMBH
Field: Engines, pumps, turbines (Mechanical engineering)
Classification: CPC F | IPC F

Claim 9:
10. A control method for operating a screw compressor, comprising:
a) setting a working frequency parameter (F) and a working internal volume ratio parameter (Vi) of the screw compressor based on a target load, wherein the working frequency parameter (F) corresponds to a predetermined working suction capacity (R);
b) determining whether the working frequency parameter (F) is lower than a working frequency threshold (Ft), wherein the working frequency threshold (Ft) corresponds to a threshold suction capacity (Rt); and
c) adjusting a position of a spool valve based on the working frequency parameter al and the working internal volume ratio parameter wherein:
c1) when the working frequency parameter (F) is not lower than the working frequency threshold (Ft),
(i) the working frequency parameter (F) is set as a working frequency of the screw compressor to adjust a speed of a screw rotor of the screw compressor and to adjust a suction capacity of the screw compressor toward the predetermined working suction capacity (R), and a displacement (L1) of the spool valve moving to an internal volume ratio adjusting position corresponding to the working internal volume ratio parameter is determined based on the set working internal volume ratio parameter (Vi), and
(ii) the spool valve is moved to the internal volume ratio adjusting position based on the displacement (L1), and, when the spool valve is in the internal volume ratio adjusting position, a spool valve head end of the spool valve is located at an outer side of a suction head end of the screw rotor of the screw compressor or is aligned with the suction head end, such that the spool valve shields a section of the screw rotor extending from the suction head end to an exhaust tail end of the screw rotor, and

c2) when the working frequency parameter (F) is lower than the working frequency threshold (Ft),
(i) the working frequency threshold (Ft) is set as the working frequency of the screw compressor to adjust the speed of the screw rotor, and a displacement (L2) of the spool valve moving to a suction capacity adjusting position corresponding to the predetermined working suction capacity (R) is determined based on the working internal volume ratio parameter (Vi), and
(ii) the spool valve is moved to the suction capacity adjusting position based on the displacement (L2), and, when the spool valve is in the suction capacity adjusting position, the spool valve head end is located at an inner side of the suction head end of the screw rotor, and a suction capacity adjusting distance (D2) is formed between the spool valve head end and the suction head end, such that the threshold suction capacity (Rt) corresponding to the working frequency threshold (Ft) is adjusted to the predetermined working suction capacity (R).