SU645038A1 - Non-stationary temperature-determining method - Google Patents

Description

The invention relates to a technique for measuring temperature and can be used in the study of unsteady aerodynamic gas flows.

Methods are known for measuring the unsteady gas temperature by detecting temperatures and rates of temperature change of two thermal sensors at a certain point in time.

In such a determination of temperature, it is necessary to know the constants of thermal inertia of thermal receivers. The dependence of these constants on temperature leads to a considerable measurement error in a wide range of temperature variations.

There is also known a method for determining non-stationary temperature by registering the reading of the thermal sensor and the first derivatives of these readings at two consecutive points in time 2.

The known method has insufficient accuracy under unsteady conditions, due to the influence of the inertia of the sensor.

The purpose of the invention is to improve the measurement accuracy.

To achieve this goal, an additional thermal sensor records the readings and first derivatives of these readings, and the temperature is determined by the formula

T

T-2 ,, + T, t (Ti ,, t} - T2, t (T-i., T (Г1, -1-д /; Т, () - (72, (+ ir / 7 2, ()

 Tk.t, Tk ,,, Гй ,, Tk, t + M - respectively, the readings and the first derivatives of the readings of the first and second temperature sensors at k, 2.

Temperatures of thermal sensors obey the following relations:

Tr, f-Ti ,, fTi, (1)

.t - Tz.t, 1 T-2, t; (2)

TT, 1 + M - T2, ..t + M + (3)

Tr, + D (-, -J-Af, (+ D Tz, t + M, (4)

where 7r ,. - gas temperature at time points;

 and / + Д, T, t, Т-2,1, Г1, (+ dl Т Тч, - the temperature of the first and second temperature sensors, respectively, at time t

and t + M;

.t, .t,., 1: 2, + d (are the constants of thermal inertia of thermal sensors at times ttit + t.

For two close points in time

we can assume that, .t + M and: 2 ,, + Л (,

then, solving the system of equations (1) - (4), we obtain the formula for determining the gas temperature

J. TZ.I + M- T, t + (T, t- -M:}, t (,,

- - T, t (T2, .t: T2,)

- {T2, t + M: T2, t)

The proposed method makes it possible to eliminate the influence of the thermal inertia constant of the thermal receiver on the accuracy of determining the temperature, and the shorter the time interval A, the higher the accuracy of temperature measurement.

Claims (2)

1. USSR author's certificate No. 399741, cl. G 01 K 7/02, 1971. 2. Authors certificate of USSR L 174398, cl. G 01 K 7/00, 1963.