Heishichiro Takahama

On Measurement of Gas Flow by Means of a By-pass Method

In order to measure the time-rate and the integrated amount of gas flow, the present authors tried to combine the by-pass method with the ordinary orifice or nozzle method. They put a standard nozzle in the main flow in order to measure the time-rate of the main flow and tapped two holes, one in front of and the other behind the nozzle, respectively, and then connected these holes to a gasmeter of small capacity by tubes so that minute part of the main flow gas might flow along this by-pass. They throttled the by-pass flow by either orifices or nozzles both at its entrance and exit. The following conclusions from our experiments with such sort of apparatuses have been obtained : 1. Total amount of a large quantity of gas flow can be read from the volume scale of the gasmeter installed in such a by-pass. So far as discharge-coefficient of the gasmeter is constant, the voluminal ratio between these main and by-pass flow is constant over a wide range of main flow velocity, with negligibly small error. 2. The by-pass flow does not affect discharge-coefficient of the main flow nozzle. 3. An apparatus fitted for a given gas flow may be laid out with great accuracy. 4. The method may be applied satisfactorily to gas flow under any pressure either heigher or lower than the atmospheric pressure. As the method let no gas into atmosphere, it may be used even for poisonous or inflamable gas.