Equipment for measuring gas flow rate

Abstract

The flow detecting elements are provided at the sub-passage for making the part of fluid to be measured (gas) flow. The wall of the sub-passage contains a leak hole (through hole) to drain a liquid having entered and accumulated inside the sub-passage. A protrusion for generating a dynamic pressure on the opening is arranged close to the opening of the leak hole on the external surface of the sub-passage. Alternatively, a protrusion located upstream from the leak hole is formed on the inner wall surface of the sub-passage. The former protrusion generates a dynamic pressure in response to the flow velocity of the gas flowing along the external surface of the sub-passage. The latter protrusion produces a separation flow area for separating the flow from the internal surface of the sub-passage (close to the leak hole), whereby the pressure of the separation floe area is reduced. This configuration provides almost the same pressure differences on the openings of the internal and external surfaces of the sub-passage, thereby reducing the amount of gas leaked from the leak hole. This reduces changes in the distribution flow velocity in the sub-passage between the cases where the leak hole is blocked and where not blocked, and minimizes flow measurement errors. Further, to prevent a liquid film or drop from being formed on the opening by surface tension, structural means is provided close to the opening of the leak hole on the external surface of the sub-passage.