EQUIPMENT FOR MEASURING GAS FLOW RATE

摘要

A flow rate measuring element is provided in a sub-passage passing a part of fluid (gas) to be measured. A leak hole (through hole) for discharging intruded and deposited liquid is made through the wall body of the sub-passage. A protrusion for generating a dynamic pressure in an opening is provided in the vicinity of an opening face of the leak hole on the outer wall side of the sub-passage. Alternatively, a protrusion is provided on the inner wall of the sub-passage and downstream of the leak hole. The former protrusion generates a dynamic pressure depending on the current velocity of gas flowing on the outer wall face of the sub-passage and the latter protrusion reduces pressure by generating a separation flow area on the inner wall of the sub-passage (in the vicinity of the leak hole). Since the pressure difference is substantially equalized between the openings of the leak hole on the inner wall side and on the outer wall side of the sub-passage, outflow of gas from the leak hole is reduced. Measurement error of flow rate is reduced by suppressing variation in the flow rate distribution in the sub-passage when the leak hole is clogged and not clogged with a liquid drop or a liquid film. As an alternative means, a structural means for preventing formation of a liquid film or a liquid drop at the opening due to surface tension is provided in the vicinity of opening of the leak hole on the outer wall side of the sub-channel.