本标准仅适用于单相气体和气体混合物的稳定流动，且仅适用于bellmouth入口流量计，在该流量计中，流量在整个测量段内保持亚音速，且流量稳定，仅随时间缓慢变化。本节还介绍了校准装置的程序，以便在得出一致结论和已知不确定度极限的情况下进行应用。Bellmouth入口流量计只能在给定装置的测试范围内使用，或者如果可以容忍额外的不确定性，则只能在外推可靠的范围内使用。 本标准概述了bellmouth入口流量计的一般几何结构和使用方法，以确定流经装置的气体或气体混合物的质量或体积流量。它还提供了计算流量及其相关不确定性的必要信息。喇叭口入口流量计是一种提供流量调节和流量测量的装置，其入口位于或定位在大型蓄水池或供应源中。储液罐可以是外部环境、室内或增压条件，具体取决于应用。bellmouth入口流量计也被称为气室、零β比喷嘴、borda管等。 典型的几何结构包括一个收敛的入口和一个恒定的喉部面积。该流量计是一种压差型装置，可通过喇叭口恒定面积喉部中单个指定轴向位置处的总压和静压之间的压差来确定流量。主要特点:基本原理和用途广泛用于燃气轮机发动机的航空航天试验设施，用于流量调节和流量测量。提供了入口火炬设计和测量注意事项。非强制性附录，用于推导计算。 提供了仪器方法的仪器选项，并讨论了其对计算和校准的影响。还提供了总压力、静压和总温度测量值，以及它们在校准和使用中的一致性。校准和不确定度讨论了在速度、体积和质量流量中为计算的空气流量开发NIST可追踪结果的各种方法。本文概述了边界层的生长和校准结果的其他影响因素。计算流体动力学（CFD）分析被认为对校准结果有重大影响。 还提供了开发不确定性声明（数据质量）的方法概述，以及确定的实际步骤。适用于能源、汽车和航空航天等行业的气体流量测量设备的工程师和其他用户。

This standard applies only to the steady flow of single-phase gasses and gas mixtures and applies only to bellmouth inlet flowmeters in which the flow remains subsonic throughout the measuring section and the flow is steady of varies only slowly with time. It also addresses procedures by which calibration of the device can be made to allow for application with consistent conclusions and with known limits of uncertainty.Bellmouth inlet flowmeters should be used only within the limits for which a given unit is tested, or if additional uncertainty can be tolerated, over a range within which extrapolation is reliable.This Standard outlines the general geometry and method of use of bellmouth inlet flowmeters to determine the mass or volumetric flow rate of the gas or gas mixture flowing through the device. It also gives necessary information for calculating the flow rate and its associated uncertainty.A bellmouth inlet flowmeter is a device that provides flow conditioning and flow measurement whose inlet is located or positioned in a large reservoir or supply source. The reservoir can be outside ambient, room or plenum conditions depending on the application. The bellmouth inlet flowmeter is also referred to as an airbell, nozzle with zero beta ratio, borda tube, etc. Typically geometry consists of a convergent inlet followed by a constant throat area. This flowmeter is a differential pressure type device that allows determination of the flow rate from the differential pressure between the total pressure and static pressure at a single specified axial location in the constant area throat of the bellmouth.Key Features:Fundamentals and usageUsed extensively in aerospace test facilities for gas turbine engines for flow conditioning and flow measurement. Inlet flare design and measurement considerations are provided.Non-mandatory appendix provided for the development of calculation with derivation.InstrumentationOptions for instrumentation methods are provided and the impact on calculation and calibration are discussed. Also provided are total pressure, static pressure, and total temperature measurements and how they must be consistent in calibration and use.Calibration and uncertaintyVarious methods for developing NIST traceable results for calculated air flow rate in velocity, volumetric and mass flowrates are discussed. Overview of boundary layer growth and other contributors to calibration results are considered.Computational fluid dynamics (CFD) analysis is mentioned as significant impact to calibration result.Also provided is an overview of the approach for developing uncertainty statement (data quality) with practical steps for determination.Intended for engineers and other users of gas-flow measurement devices in such industries as energy, automotive and aerospace.