| 摘要 |
A pressure-type flow rate control apparatus controls the flow rate of fluid passing through an orifice to a target flow rate. The flow rate of a compressible fluid under non-critical conditions (sub-sonic) passing through the orifice is calculated by: <?in-line-formulae description="In-line Formulae" end="lead"?>Qc=KP<SUB>2</SUB><SUP>m</SUP>(P<SUB>1</SUB>-P<SUB>2</SUB>)<SUP>n</SUP><?in-line-formulae description="In-line Formulae" end="tail"?> so that the flow rate can be controlled to the target flow rate with high precision and speed. Also provided is an improved pressure-type flow rate control apparatus in which a pressure ratio P<SUB>2</SUB>/P<SUB>1</SUB>=r, obtained from an upstream pressure P<SUB>1 </SUB>and a downstream pressure P<SUB>2 </SUB>is constantly compared with a critical value r, and under critical conditions (r<=R<SUB>c</SUB>), the flow rate is calculated by: <?in-line-formulae description="In-line Formulae" end="lead"?>Qc=KP<SUB>1</SUB>.<?in-line-formulae description="In-line Formulae" end="tail"?> Under non-critical conditions (r>r<SUB>c</SUB>), the flow rate is calculated by Qc=KP<SUB>2</SUB><SUP>m</SUP>(P<SUB>1</SUB>-P<SUB>2</SUB>)<SUP>n</SUP>.
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