To provide a mixed gas supply system capable of obtaining mixed gas in a stable mixing ratio while ensuring desired mixing accuracy regardless of fluctuations in pressure.
This system is constituted of gas introducing passages 3, 4 introducing raw material gases 1a, 1b into a mixer 2, flow rate adjusting devices 51, 52 adjusting the introducing amts. of the raw material gases 1a, 1b into the mixer 2 constant, a pressure leveling valve 14 controlling and holding the pressures on the inlet side of the flow rate adjusting devices 51, 52 to the same pressure and a gas supply passage supplying the mixed gas 1 obtained in the mixer 2 to a mixed gas using part 8. In this case, this system is operated under either one of a condition wherein the pressure ratio of the pressures on the outlet side of the flow ratio adjusting devices 51, 52 to the pressures on the inlet side thereof is a critical pressure ratio or less and the gas flow velocity in each of the flow rate adjusting devices becomes sonic velocity, a condition wherein the above mentioned pressure ratio is a predetermined pressure ratio or less and the gas flow velocity in each of the flow rate adjusting devices becomes sonic velocity or sub-sonic velocity and a condition wherein the above- mentioned pressure ratio is the predetermined pressure ratio or less and the gas flow velocity in each of the flow rate adjusting devices does not reach sonic velocity.
KUBO MITSUSHI
YAMAZAKI NORIO
MIMURO KIMIATSU
GAS MITSUKUSU KOGYO KK