Abstract: It is critical for the measurement accuracy of flow rate in the liquid rocket engine test. Different from the flow rate measurement at normal temperature, there are many special characters in flow rate measurement for cryogenic propellant. The principle and scheme of the calibration for cryogenic flow rate in weighting method are introduced. The formulas of ullage flow rate in inflow and outflow conditions are deducted. In the discussion of thermal stratification of ullage, the heat and mass transfer mechanisms in cryogenic tank are considered. In the end, it draws a conclusion that inflow weighting method leads to higher accuracy to calibrate the cryogenic flow meter, because of the better stability of ullage flow rate in the inflow method.

Key words: Dynamic weighting, Cryogenics, Inflow method, Ullage temperature, Influence analysis