| 摘要 |
This invention relates to the novel method for stabilizing the pressure sensed by the downstream-facing port of a pitot tube type flowmeter over a broad flow range, thereby providing a stable and repeatable flow coefficient. The invention comprises localizing the areas of boundary layer separation across deflecting surfaces located upstream of said port by sharply contouring the edges thereof and directing the flowing stream thereacross, and preventing reattachment of said boundary layer by positioning and contouring the surfaces containing said port downstream of said sharply contoured edges so as to continuously lie within the wake of the fluid flowing around the latter over a broad range of flow rates. The invention also encompasses the improved averaging pitot-type flowmeter characterized by flow deflecting means having sharply contoured edges on both sides thereof effective to fix the location at which boundary layer separation occurs over a broad range of laminar and turbulent flow conditions, an upstream-facing impact surface shaped to direct the flowing fluid across said sharply contoured edges, and a downstream-facing surface containing a port for sensing downstream pressure so contoured and positioned relative to said sharply contoured edges as to cooperate therewith in preventing reattachment of the boundary layer under varying flow conditions. |
