Method and apparatus to determine flow rate with the introduction of ambient air

摘要

A method of determining a rate of flow of a first gas in a pipe includes placing a flow-restricting device in the pipe such that the device and/or the pipe define a first channel section and a second channel section. The second channel section is disposed downstream from the first channel section. The first channel section has a first cross-sectional area. The second channel section having a second cross-sectional area less than the first cross-sectional area. A source of a second gas is provided in fluid communication with the second channel section. A low pressure in the second channel section is caused by an increased flow velocity and creates a flow of the second gas into the second channel section. A rate of a flow of the second gas into said second channel section is measured. A mathematical relationship between the rate of the flow of the second gas into the second channel section and the rate of flow of the first gas in the pipe is ascertained. The rate of flow of the first gas in the pipe is calculated based at least partially upon the rate of flow of the second gas into the second channel section and the ascertained mathematical relationship.