Optimization of Gas Dynamical Subsystem of Transducers for
Measurement of Gas Flow Temperature
Vasyl Fedynets , Ihor Vasylkivskyi, Yaroslav Yusyk
Lviv Polytechnic National University, 12, S. Bandery str., Lviv, 79013, Ukraine
Received: November 11, 2016. Revised: December 12, 2016. Accepted: December 26, 2016
© 2016, Fedynets V., Vasylkivskyi I., Yusyk Ya. Published by Lviv Polytechnic National University
Abstract
The main types of errors which occur while measuring the temperature of gas flows, including flows of fuels, are determined by the conditions of thermal balance at the interaction of the sensor of the temperature transducer (TT) with the gas flow via convection, radiation and conduction. The limited TT capacity to track flow temperature variation should also be taken into consideration. For high gas flow speeds (over 50 m/s), another type of error (the so-called speed error) arises from the transformation of part of kinetic energy of the flow into thermal energy. A comprehensive analytical study of the combined influence of all the major factors on the total error of gas flow temperature measurement with a particular TT is actually impracticable, since some relationships describing the character of influence of this or that factor can be obtained only by experiment. Therefore, in practice, each error type is analysed separately, assuming that no other types of error occur, and the total error of measurement is regarded as superposition of separate error types. For convenience of analysis, TT is represented as a combination of separate units, each with its own components of the error. TT for gas flow temperature measurements appears as three units, such as gas dynamic, thermal and electrical, connected in series. The gas dynamic subsystem transforms the thermodynamic temperature T(τ) of the gas flow at the TT input into the deceleration temperature ТПТ(τ) at the temperature sensor input and is characterized by the speed error. The defining characteristic of the gas dynamic subsystem is the TT recovery factor, which is why the paper discusses the methods and means of ensuring the constancy of the recovery factor.
Keywords: gas flow; measurement; heat exchange; temperature; temperature transducer.
References – 15.