Prof. Y. Pistun, Assoc. Prof. F. Matiko, Assoc. Prof. R. Fedoryshyn
IMPROVEMENT OF ACCURACY OF NATURAL GAS METERING BY MEANS OF HOUSEHOLD GAS METERS

The paper deals with the new technique for calibration of the household gas meters according to the working conditions in order to reduce the error caused by non-conversion of gas volume to base conditions. To apply this technique the studies of gas pressure and temperature variations in household gas meters during a year were carried out, the ratio of gas volumes consumed by household consumers during the cold and warm seasons of the year is defined. Based on the studies the average annual gas temperature and pressure weighed by the consumed gas volumes are defined. Based on the weighed values of gas temperature and pressure the nominal values of gas temperature and pressure are defined in order to convert the readings of the gas meters to these nominal values. Application of the developed technique provides reduction of unaccounted volume of gas and reduction of unbalances in gas distributing companies.

Lixu, Su Yanxun, Cui Lishui, Hu Heming, Wangjie
ESTABLISHMENT OF A NEW HYDROCARBON FLOW STANDARD FACILITY AT NIM

A new oil flow standard device is built with dual-standard by National Institute of Metrology(NIM). The two types of standards are installed in the device, namely, new-type auto-load electronic scale and standard volumetric tube. Working medium: transformer oil, with a kinematic viscosity of 21 mm²/s; flow range: (1.2 ~ 120) m³/h; the extended uncertainty of the oil flow meter with double standards: U_rel ≤ 0.05% (k = 2); the extended uncertainty for mass method: U_rel = 0.04%; the extended uncertainty for volumetric tube U_rel = 0.03%. The repeatability is less than 0.02%. The large-caliber standard comparison group uses turbine flowmeter as the master meter and ultrasonic flowmeter as the auxiliary monitoring meter; in the small-caliber group, only Coriolis mass flowmeter is exclusively used as comparison standard. According to the test results of two types of flowmeter, the measurement uncertainty and repeatability are less than 0.05% and 0.02%, respectively. In order to raise the uncertainty of mass method, researchers specially design auto-load calibration system for electronic scale and a new-type rotary Diverter.

J Kutin, G Bobovnik, I Bajsić
DYNAMIC TEMPERATURE EFFECTS IN A CLEARANCE-SEALED PISTON PROVER FOR GAS FLOW MEASUREMENTS

This paper deals with the dynamic temperature effects in a high-speed, clearance-sealed realization of a piston prover. A dynamic mathematical model was built to study the temperature variations and to estimate their influence on the flow measurements. The mathematical model is formulated on the basis of lumped-element models of the piston and the gas cavity. The energy balance for the gas cavity includes the convective heat exchange with the surroundings. One of the potential effects results from the temperature differences betwen the inlet gas flow and the cylinder wall. In addition, the piston prover's operation generates dynamic temperature variations which are mainly related to the pressure change due to the flow redirection and to the pressure oscillations due to the piston's resonance effects.

J. Sundström, M. J. Cervantes
EVALUATION OF THE VOLUMETRIC METHOD WITH APPLICATION TO LOW HEAD HYDRAULIC MACHINES

The present work presents an evaluation of a flow measuring method known as the volumetric method. The method consists in running a turbine at a constant load during an extended period of time which depends upon the reservoir geometry. The flow rate through the turbine is determined from the volume change in the reservoir(s) by measuring the water level change. Through a pilot study in a full scale machine it is shown that the method reproduces reasonable results. The measured flow rate deviates by less than 3% from the value reported in the hydropower plant. The accuracy of the reported flow rate and the one measured in here is however difficult to determine and left unconsidered in this work. For future studies of the method it is recommended to more thoroughly investigate how accurately the rate of change of water level along with the reservoir area can be determined.

I. Gryshanova, P. Pogrebniy
INVESTIGATION OF OPTIMAL CHORD TOPOLOGY FOR MULTIPATH ULTRASONIC FLOW METERS IN DISTORTED FLOWS

In this study a theoretical investigation of performance of multipath ultrasonic flow meters under distorted flow profiles is proposed. The velocity distribution depends on the pipe configuration, which will produce an asymmetric flow profile and as a result will affect the accuracy of measurement. So, we discover how to minimize the effect of distorted flows on measuring process of ultrasonic flow meters due to number of chords and their arrangement. In order to evaluate the performance of the multipath ultrasonic flow meters the measurement error is determined for various asymmetric flow profiles with different chord configurations. As a part of the work it was obtained strategy that can reduce the error associated with different flow disturbances. Using CFD analysis interesting conclusions have been derived. These conclusions can be applied to specific individual situations and a significant reduction in error can be achieved.