GB1008392A - Turbine meters - Google Patents

Abstract

1,008,392. Rotary meters. ROCKWELL MANUFACTURING CO. Feb. 18, 1964, No. 6795/64. Heading F1F. To improve the accuracy of rotary flow meters metering fluids of high viscosity, e.g., crude oils, having a bladed metering rotor 30, Fig. 1, rotated by the flowing fluid and connected to a register 22, the meter includes a free-spinning rotor 34 fitted upstream of the rotor 30 having blades 46, the blade angle of which is approximately equal and opposite to the blade angle of the blades of the bladed metering rotor 30, so that the rotors rotate at about the same speed in opposite directions. The axial spacing between the rotors is made short enough so that the tangential component of fluid exit velocity from the free rotor is not significantly reduced by fluid friction in the spacing and long enough so that the disturbance upstream of the metering rotor created by the counter rotating free rotor is small when its reaches the metering rotor. Experimentally a suitable spacing is found to be at least twice the chord length of the blades of the free rotor. Torque resisting rotation of the rotors is made up of three parts, (a) that due to mechanical friction of the rotors in the bearings which are of sapphire to reduce this to a minimum value, (b) that due to the turbulance of the flowing fluid, and (c) that due to the viscosity of the flowing fluid With fluids of high viscosity, resisting torque due to (c) may be large in magnitude and although its magnitude may not be reduced, the fitting of a free counter rotating roter in front of the metering roter substantially cancels out its effect on the metering roter. For small flows and on starting, it is shown mathematically that the driving torque on the meter is practically doubled with the addition of the free roter in front of the metering roter. Specification 917,140 is referred to.