Skewed velocity profile effect on turbine flowmeter performance

Abstract

Turbine flowmeters (TFMs) are mechanical flow metering devices and are being used extensively in various industries to measure the flowrate of a wide variety of fluids. The TFMs are known for their excellent repeatability, higher accuracy, wide operating range, high shock capability, low pressure loss and wide temperature and pressure limits. The performance characteristics of TFMs depend greatly on the upstream flow condition, the fluid properties and the geometrical parameters of the rotor. Hence, a systematic study has been carried out to establish the effect of a skewed velocity profile on the lower limit of the linear range, usable range, meter factor and pressure drop across the meter. Alteration of the velocity profile has been achieved by providing a gate valve about four pipe diameters upstream of the meter. From the result, it can be seen that the average meter factor does not change for a slightly skewed velocity profile but increases drastically for a highly skewed velocity profile. To overcome the skewed velocity profile effect, three types of flow straightener have been provided upstream of the rotor. It is found that a ten-bladed flat plate straightener is most effective in killing the skewness in the upstream velocity profile and keeping the variation in meter factor within ±1.25 per cent of the standard values.