Mixture ratio regulation for two gaseous fluids - uses predetermined calibrated orifices to produce constant ratio independent of flow

摘要

The mixture ratio of two gaseous fluids such as air and propane is regulated using pre-determined calibrated orifices so that the ratio is almost constant and independent of flow even when the flow is much lower than normal. Two gaseous fluids (F1, F2) flow through conduits (12, 14) with step valves (30, 32) and are terminated by calibrated orifices (16, 18) feeding into a mixture chamber (20) whose output (22) supplies operating equipment. Secondary circuits comprise conduits (34, 36) terminated by calibrated orifices (38, 40) feeding into the mixture chamber. A spur (28) controls (26) the pressure of fluid (FL) in the conduits (14, 36) at the fluid pressure in the other fluid conduit (34). A flowmeter (46) closes the step valves when flow falls below a particular value.