Measurement of temperature of molten zone at the directional crystallization of blades of the gas-turbine engine
The review article is devoted to detailed analysis of known methods and ways for measuring the temperature parameters in the area of directional solidification of the melt of the rotor blades of gas-turbine engines. The analysis of existing methods of temperature control such as contactless methods...
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Інститут металофізики ім. Г.В. Курдюмова НАН України
2017
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irk-123456789-1332392018-05-22T03:03:52Z Measurement of temperature of molten zone at the directional crystallization of blades of the gas-turbine engine Markin, M.O. Markina, O.M. Kushchovyi, S.M. The review article is devoted to detailed analysis of known methods and ways for measuring the temperature parameters in the area of directional solidification of the melt of the rotor blades of gas-turbine engines. The analysis of existing methods of temperature control such as contactless methods and contact ones is made. As found, in further progress and development of devices and methods of temperature analysis, priority belongs to pyrometry. Relied on the advantages and disadvantages of existing methods, it is determined that the solution of this problem is possible with use of spectral and imaging pyrometry. Обзорная статья посвящена основательному анализу известных методов и способов измерения температурных параметров в зоне расплава при направленной кристаллизации рабочих лопаток роторов газотурбинных двигателей. Проведён анализ существующих методов контроля температуры как контактных, так и бесконтактных. Установлено, что в дальнейшем прогрессе и развитии приборов и способов анализа температуры приоритет принадлежит пирометрии. Опираясь на недостатки и преимущества существующих методов, определено, что решение поставленной проблемы возможно за счёт использования спектральной и телевизионной пирометрии. Оглядову статтю присвячено ґрунтовній аналізі відомих метод і способів міряння температурних параметрів у зоні розтопу за спрямованої кристалізації робочих лопаток роторів газотурбінних двигунів. Проведено аналізу наявних метод контролю температури як контактних, так і безконтактних. Встановлено, що у подальшому проґресі та розвитку приладів і способів аналізи температури пріоритет належить пірометрії. Спираючись на недоліки та переваги наявних метод, визначено, що розв’язання поставленої проблеми можливе з допомогою використання спектральної та телевізійної пірометрії. 2017 Article Measurement of temperature of molten zone at the directional crystallization of blades of the gas-turbine engine / M.O. Markin, O.M. Markina, S.M. Kushchovyi // Успехи физики металлов. — 2017. — Т. 18, № 2. — С. 141-154. — Бібліогр.: 21 назв. — англ. 1608-1021 PACS: 07.20.-n, 07.20.Ka, 42.79.-e, 44.05.+e, 81.30.Fb, 81.40.Tv, 81.70.Fy DOI: https://doi.org/10.15407/ufm.18.02.141 http://dspace.nbuv.gov.ua/handle/123456789/133239 en Успехи физики металлов Інститут металофізики ім. Г.В. Курдюмова НАН України |
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The review article is devoted to detailed analysis of known methods and ways for measuring the temperature parameters in the area of directional solidification of the melt of the rotor blades of gas-turbine engines. The analysis of existing methods of temperature control such as contactless methods and contact ones is made. As found, in further progress and development of devices and methods of temperature analysis, priority belongs to pyrometry. Relied on the advantages and disadvantages of existing methods, it is determined that the solution of this problem is possible with use of spectral and imaging pyrometry. |
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Article |
| author |
Markin, M.O. Markina, O.M. Kushchovyi, S.M. |
| spellingShingle |
Markin, M.O. Markina, O.M. Kushchovyi, S.M. Measurement of temperature of molten zone at the directional crystallization of blades of the gas-turbine engine Успехи физики металлов |
| author_facet |
Markin, M.O. Markina, O.M. Kushchovyi, S.M. |
| author_sort |
Markin, M.O. |
| title |
Measurement of temperature of molten zone at the directional crystallization of blades of the gas-turbine engine |
| title_short |
Measurement of temperature of molten zone at the directional crystallization of blades of the gas-turbine engine |
| title_full |
Measurement of temperature of molten zone at the directional crystallization of blades of the gas-turbine engine |
| title_fullStr |
Measurement of temperature of molten zone at the directional crystallization of blades of the gas-turbine engine |
| title_full_unstemmed |
Measurement of temperature of molten zone at the directional crystallization of blades of the gas-turbine engine |
| title_sort |
measurement of temperature of molten zone at the directional crystallization of blades of the gas-turbine engine |
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Інститут металофізики ім. Г.В. Курдюмова НАН України |
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2017 |
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http://dspace.nbuv.gov.ua/handle/123456789/133239 |
| citation_txt |
Measurement of temperature of molten zone at the directional crystallization of blades of the gas-turbine engine / M.O. Markin, O.M. Markina, S.M. Kushchovyi // Успехи физики металлов. — 2017. — Т. 18, № 2. — С. 141-154. — Бібліогр.: 21 назв. — англ. |
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141
PACS numbers: 07.20.-n, 07.20.Ka, 42.79.-e, 44.05.+e, 81.30.Fb, 81.40.Tv, 81.70.Fy
Measurement of Temperature of Molten Zone at the Directional
Crystallization of Blades of the Gas-Turbine Engine
M. O. Markin, O. M. Markina, and S. M. Kushchovyi
National Technical University of Ukraine
‘Igor Sikorsky Kyiv Polytechnic Institute’,
37 Peremogy Ave.,
UA-03056 Kyiv, Ukraine
The review article is devoted to detailed analysis of known methods and
ways for measuring the temperature parameters in the area of directional
solidification of the melt of the rotor blades of gas-turbine engines. The
analysis of existing methods of temperature control such as contactless
methods and contact ones is made. As found, in further progress and de-
velopment of devices and methods of temperature analysis, priority be-
longs to pyrometry. Relied on the advantages and disadvantages of exist-
ing methods, it is determined that the solution of this problem is possible
with use of spectral and imaging pyrometry.
Оглядову статтю присвячено ґрунтовній аналізі відомих метод і спосо-
бів міряння температурних параметрів у зоні розтопу за спрямованої
кристалізації робочих лопаток роторів газотурбінних двигунів. Прове-
дено аналізу наявних метод контролю температури як контактних, так
і безконтактних. Встановлено, що у подальшому проґресі та розвитку
приладів і способів аналізи температури пріоритет належить піромет-
рії. Спираючись на недоліки та переваги наявних метод, визначено, що
розв’язання поставленої проблеми можливе з допомогою використання
спектральної та телевізійної пірометрії.
Обзорная статья посвящена основательному анализу известных методов
и способов измерения температурных параметров в зоне расплава при
направленной кристаллизации рабочих лопаток роторов газотурбинных
двигателей. Проведён анализ существующих методов контроля темпе-
ратуры как контактных, так и бесконтактных. Установлено, что в
дальнейшем прогрессе и развитии приборов и способов анализа темпе-
ратуры приоритет принадлежит пирометрии. Опираясь на недостатки и
преимущества существующих методов, определено, что решение по-
ставленной проблемы возможно за счёт использования спектральной и
телевизионной пирометрии.
Успехи физ. мет. / Usp. Fiz. Met. 2017, т. 18, сс. 141–154
DOI: https://doi.org/10.15407/ufm.18.02.141
Îòòèñêè äîñòóïíû íåïîñðåäñòâåííî îò èçäàòåëÿ
Ôîòîêîïèðîâàíèå ðàçðåøåíî òîëüêî
â ñîîòâåòñòâèè ñ ëèöåíçèåé
2017 ÈÌÔ (Èíñòèòóò ìåòàëëîôèçèêè
èì. Ã. Â. Êóðäþìîâà ÍÀÍ Óêðàèíû)
Íàïå÷àòàíî â Óêðàèíå.
https://doi.org/10.15407/ufm.18.02.141
142 M. O. MARKIN, O. M. MARKINA, and S. M. KUSHCHOVYI
Keywords: temperature measurements, molten zone, directional solidifica-
tion, spectral pyrometry, imaging pyrometry, bispectrum pyrometry.
Ключові слова: вимірювання температури, зона розплаву, направлена
кристалізація, спектральна пірометрія, телевізійна пірометрія, біспек-
тральна пірометрія.
Ключевые слова: измерение температуры, зона расплава, направленная
кристаллизация, спектральная пирометрия, телевизионная пиромет-
рия, биспектральная пирометрия.
(Received March 13, 2017; final version — April 03, 2017)
1. INTRODUCTION
Almost every scientific research or manufacturing process requires
measurement and measurement data, so there is no doubt that
without the development of methods and tools for measuring the
progress of science and technology is impossible.
Temperature measurements, in particular, are very important in
terms of further progress of research and development of priority
sectors of metallurgical industry, mechanical engineering (aerospace
and automotive), and in tool building and electrical engineering.
One of the most important processes in these areas is directional
solidification method that is used for production of monocrystalline
structure. For instance, the rotor blades of gas turbine engines (GTE).
Directional solidification (DS) is widely used for deep cleaning of
various organic and inorganic substances from impurities [1]. The
main goal of the DS process is a growing monocrystals of various
substances. There are technological options based on DS that exer-
cise directed heat removal from the border of phase transition that
is in turn directed movement of crystallization front along the sam-
ple (see Fig. 1) [2]. This movement (usually with a constant speed)
is carried out forcibly by gradually moving the heating and cooling
zones [1].
High level of operational properties of materials manufactured by
directional solidification are largely based on microstructure fea-
tures formed during the directional solidification, homogeneity,
high dispersion, and orientation along the direction of heat.
Currently, the directional solidification process is widely used for
the rotor blades of gas turbine engines with directed and monocrys-
talline structure. The choice of process parameters to ensure the
required quality of castings, castings depends on the geometry and
design of the installed thermal units [3].
Turbine blades (Fig. 2) are among the most complex and impor-
tant details of GTE. They operate at high temperatures and pres-
TEMPERATURE OF MOLTEN ZONE AT THE CRYSTALLIZATION OF BLADES 143
sures. The reliability of turbine blades depends on resources and ef-
ficiency of turbine engine operation. Reliability of blades, in turn, is
determined by the quality of their production, namely macro and mi-
crostructure, geometry of the casting and its thermal properties [4].
Given the growing competition in the global market of aviation
instrumentation, which makes high demands to improve reliability,
Fig. 1. Moving zones of phase transition [2].
Fig. 2. Working gas-turbine engine (GTE) blade.
144 M. O. MARKIN, O. M. MARKINA, and S. M. KUSHCHOVYI
working capacity and efficiency of GTE, developers and producers
are facing the task of increasing the guaranteed lifespan of GTE,
increased engine power while reduced total mass.
It is known that the resource efficiency of engines defined by the
turbines capabilities (installation with the rotational movement of
the working body—rotor), and especially the most loaded part of
it—blades. Stiffness of temperature and power conditions leads to
the development of structures and the use of monocrystalline blades
structure (compared to the blade, which has polycrystalline struc-
ture, the monocrystalline blade strength and heat resistance is 9
times higher, and resistances to oxidation and corrosion—3.5 times
[5]). Therefore, there is a problem detailed study of the directional
solidification of GTE blades, its automation and computerization,
requiring the use of special measuring techniques (SMT) for meas-
urement, control and management of major process parameters such
as temperature field and the velocity of the crystallization front.
Therefore, the goal of this work consists in extended and thor-
ough analysis of the known methods and ways to measure the tem-
perature settings in melting zone at DS of rotor blades of GTE.
2. TEMPERATURE MEASUREMENT METHODS
There are two main classes of temperature measuring instruments:
contact and contactless. [6]. The first one means thermometry based
on contact with the object in which to determine the temperature,
and the second one means widely known pyrometry—the process of
measuring the surface temperature of hot bodies using the informa-
tion contained in the radiation [7].
Contact measurement tools rely on direct contact of measurement
tools with the object, resulting, in the ideal case, to thermodynamic
equilibrium of transducer and the object. Currently, there are about
a hundred thermometry methods, however only a small part of them
are widely used. Effects of different devices for determining the
temperature (thermometer) are based on the temperatures. Tradi-
tional means of measurement are liquid thermometers, thermocou-
ples and others [8].
In contact thermometry, temperature is always measured by its
own temperature, which, in under a number of conditions, accu-
rately matches the temperature of the object being studied in con-
tact. Contact thermometers are common in the temperature range
from cryogenic to 1000–1500 K. In many cases, they do not provide
the required performance in measurements, spatial resolution and
speed of measurement; also, they are not suitable at high tempera-
tures. In addition, this class of measurements possesses disadvan-
tages as follows: the object is distorting temperature field while in-
TEMPERATURE OF MOLTEN ZONE AT THE CRYSTALLIZATION OF BLADES 145
serting the sensor; temperature transducer’s temperature is always
different from the true temperature of the object; the upper limit
of temperature measurement is limited by the properties of the ma-
terials of which sensors are made [9].
In addition, a number of important problems associated with
measuring the temperatures off the reach (zone melting, directional
solidification) and moving objects (Metiz of aluminium, extrusion
of profiles) cannot be settled by contact method. Also, contact tem-
perature measurement is sometimes quite expensive. This applies in
particular in the steel smelting process, where temperature of mol-
ten metal is usually determined by the thermocouple, which is ex-
pensive and after immersion in the molten metal thermocouples are
no longer suitable for use, as their sensor immediately breaks down.
Thus, contact tools do not meet the set requirements for tempera-
ture measurement of molten zones of GTE blades during directional
solidification.
The combination of these deficiencies thermometry necessitated
the emergence in the late XIX and early XX century contactless
temperature measurement. Around the same time, there are two ba-
sic methods for determining the non-contact temperature, namely
radiation pyrometry, which is based on the Stefan–Boltzmann law
[5] and spectral pyrometry, based on the Wien’s value [5]. Later
there was emerged another method of contactless temperature
measurement, called TV pyrometry (TP) [10]. The TP method is
based on the analysis of energy characteristics of monochromatic
radiation. We know that today non-contact measurement methods
have gained the biggest development and widespread adoption; this
is considered in works [11–14]. These methods are based on regis-
tration of own thermal radiation of object. Object temperature is
measured by the radiation characteristics described by Planck [15],
which establishes a general link between the spectral density of ra-
diation, wavelength and temperature radiator. Given the rapid de-
velopment components (photodetectors, optics, microprocessors,
etc.), pyrometry is gaining scale and importance.
Let us consider further the conduct and analysis of contactless
pyrometry methods in the context of the task to control tempera-
ture parameters of the DS GTE blades.
2.1. Radiation Pyrometry
Radiation pyrometry method uses dependence of energetic bright-
ness of radiation in a limited wavelength range on object’s tempera-
ture. In other words, the brightness of radiation of an object de-
pends on its temperature. Accordingly, by measuring the brightness
of the radiation, we can measure (with some accuracy) the tempera-
146 M. O. MARKIN, O. M. MARKINA, and S. M. KUSHCHOVYI
ture of the object. Thus, the key element of radiation pyrometer is
detector that converts radiant energy that passed through him to
another physical quantity, often in current or voltage. Receiver is
complemented with optical system that collects the radiation from
the object in a defined angle. Electronic circuits and power systems
convert and display the measurement result [16].
2.2. Spectral Pyrometry
The method of spectral pyrometry (SP) is based on the fact that, in
the thermal radiation of optical spectra, there are many areas,
which have similarities with Planck spectrum. It means that the
studied objects are grey emitters in these spectral intervals. To find
the interval and determine the temperature of the radiator, you
have to register a wide range of continuous radiation [17].
In other words, the method of determining the temperature is
based on the relative brightness measurements in a wide range of
radiation of object that has its emissivity. The difference of the RP
is not only in the usage of a large number of wavelengths (photo-
sensitive line containing from 500 to 3600 pixels), but also compul-
sory testing of registered spectrum and blackbody spectrum.
2.3. Imaging Pyrometry
General method of using imaging measurement tools (IMT) is based
on forming an image, converting it into digital code and using algo-
rithms that provide the required accuracy of measurement of rele-
vant parameters.
One of the most dynamic areas of modern pyrometry is pyrome-
try of radiation or imaging pyrometry, which is defined as a combi-
nation of high-temperature measurement methods, built on the de-
pendence of the surface temperature of the body and the energy
characteristics of its own radiation.
At present, the main driving force of scientific development of
television measuring device (TMD) is television information and
measuring system (TIMS), which is a combination of optical and
electronic means by which information about the structure, proper-
ties and condition of object in its radiation is converted into an
electrical signal. Figure 3 shows a physical model of the informa-
tion signal in the imaging information and measuring system.
TIMS actually marked a new level of measurement technologies,
and potentially they are most relevant to the requirements of mod-
ern geometric measurement, dynamic and amplitude parameters of
many objects and processes [18].
TEMPERATURE OF MOLTEN ZONE AT THE CRYSTALLIZATION OF BLADES 147
2.4. Physical Basis of Spectral Pyrometry
The SP is based [15] on the fact that the ratio of brightness of L
blackbody radiation at two wavelengths uniquely identifies the
temperature T (Fig. 4). The method consists in measuring and com-
paring the brightness of radiation at two wavelengths (1 and 2).
The number of unknowns is always greater than the number of
measured values. To find the real temperature of the body, it is
necessary that the number of measured values is equal to the num-
ber of unknowns.
The number of unknowns can be reduced if you know the ratio of
two factors:
1 1
2 2
( )
( )
, (1)
Fig. 3. Physical model of the information signal in television pyrometry (TP).
Fig. 4. The brightness of radiation for different temperatures of black-
body: 1000 K (1), 1500 K (2), and 2000 K (3). The ratio of the brightness
L1/L2 at two wavelengths (1 0.9 m and 2 1.3 m) decreases mono-
tonically with increasing temperature.
148 M. O. MARKIN, O. M. MARKINA, and S. M. KUSHCHOVYI
where 1 and 2 are coefficients of emissivity of appropriate wave-
lengths 1 and 2 (in micrometres), respectively.
We can always relate unknown coefficients at these wavelengths.
The introduction of additional conditions provides a system of two
algebraic equations with two unknowns (Т and ) and real T. For
example, there is the usual condition,
1 2
k , (2)
where k is a considered known value.
The relation between the spectral (Tc) and real (T) temperatures
of the object during registration of radiation in Wien’s areas is
given by expression
1
1 1 2
2 2 2 1
1 1
ln
c
T
T C
, (3)
where C2 14.388 m.
The procedure of determining the temperature with spectral py-
rometry method consists of brightness L1 and L2 measurement at
two wavelengths, doing ratio correction L1/L2 using calculated or
measured ratio 1/2 and measuring temperature for the Planck’s
function with the same value Z (L21)/(L11), which determines the
ratio of brightness blackbody radiation at these wavelengths.
Figure 5 shows the temperature dependence of the object’s tem-
perature on the value of Z on wavelengths 1 530 nm and 1 650
nm, if C2/(T) 1 then
Fig. 5. Temperature dependence of the ratio of the actual brightness (with
the emissivity of the two wavelengths) Z L21/L12: 1—Planck’s model,
2—Wien’s model.
TEMPERATURE OF MOLTEN ZONE AT THE CRYSTALLIZATION OF BLADES 149
2 1 1 2
2
2 1
( )
ln ( )
T C
Z
(4)
At not very high temperatures, result obtained through Wien’s
approximation (curve 2) coincides with the result of calculation us-
ing the exact Planck’s formula (curve 1).
When you use the exact formula of Planck, the desired spectral
temperature can’t be expressed explicitly, as in the Wien’s formula,
and calculating the temperature is performed by selection of the T
value, substitution of which leads to best match the right (calcu-
lated) and left parts (measured experimentally):
5
2 12 1 1
1 2 2 2 2
exp 1
exp 1
C TL
L C T
. (5)
If the ratio 1/2 is unknown, the desired spectral temperature
can have significant difference from actual temperature.
2.5. Problems of Spectral Pyrometry
The problems of spectral pyrometry (SP) are considered in Ref.
[10]. There are two main problems up to date. Those are relative
expensiveness (compared with radiation pyrometer) and influence of
the emissivity on the results of temperature measurement.
Pyrometer of spectral ratio (PSR) is structurally much more
complicated than radiation one, and has a greater number of ele-
ments and it is harder to calibrate it. Availability of additional de-
vices and nodes increases the amount of work of the manufacturer,
so spectral ratio pyrometers are more expensive in comparison with
radiation pyrometers.
Emissivity of measured objects affects the measurement results.
Specifically, the PSR measurement result depends not only on the
size of radiating ability or on changes from object to object, but
more from the spectral dependence f().
Figure 6 shows the spectral dependence of the emissivity of for
five types of metal: Fe, Ni, Cu, Ag, and Co [19]. They characterize
most of metals and their alloys. From Figure 6, we can conclude
that all dependences have roughly the same type of dependence:
with increasing wavelength, spectral emissivity decreases. This
leads to the fact that long-wave signal receiver PSR appears low
compared with shortwave one. That is why PSR results are often
overestimated by 10%.
Calculating of the magnitude of error because of lowering of is
possible only if receiver bandwidth is very narrow and is not bigger
150 M. O. MARKIN, O. M. MARKINA, and S. M. KUSHCHOVYI
than 10–12 nm [9].
However, recently the majority of PSR uses two-layer photodiode
structure, the upper layer of which has a maximum sensitivity in
the short-wave spectrum, the bottom—in the long-wave. Strips of
spectral sensitivity of the receivers make hundreds of nanometres,
which eliminates the error due to instability of . Also, informa-
tion about of most materials that need to be measured in the in-
dustry, is extremely limited or non-existent [19]. That is why the
issue of correction of indications of PSR during measuring the
temperature of objects with radiating ability, depending on the
wavelength, had not been resolved. For a long time, users had to
deal with this, as in many cases it is important not only precise
knowledge of the measured temperature as following its repeatabil-
ity in the process.
However, these problems are not critical and fundamental for
solving this problem. So, the SP method can be used to measure
temperature parameters in the melting area during directional crys-
tallization (DC) of rotor blades of GTE, because the SP gives suffi-
cient understanding of the thermodynamic temperature, and the
measurement results do not depend on the coefficient of emissivity.
Note that the result of the PSR measurement depends not only on
emissivity values of its ability, but also changes from object to ob-
ject, and also depends on the spectral dependence f().
Another method one can use to solve the problem on measuring
the temperature of the molten zone at the directional solidification
of GTE blades is bispectrum pyrometry [20].
2.6. Physical Basis of Multispectral Pyrometry
The circuit in Fig. 3 suggests algorithm to create a mathematical
Fig. 6. Dependence of emissivity for Fe, Ni, Cu, Ag, and Co metals on the
wavelength .
TEMPERATURE OF MOLTEN ZONE AT THE CRYSTALLIZATION OF BLADES 151
model of formatting the information signal in multispectral py-
rometry.
Power spectral luminosity of body at the temperature T [21],
1 2
5
, exp
C C
M T
T
, (6)
then spectral illumination of matrix [12],
2
( ) ,
4
C O
D
E M T
f
, (7)
where D/f is an aperture length, C() is a spectral transmittance
environment, O() is a spectral transmittance of the optical system.
So, the signal at the output TP:
2
1 2
5
, exp
4
C O
C CD
A T K
f T
; (8)
here, K is a conversion factor of charge-coupled device (CCD-matrix).
This model is correct for temperature measurement, if system
parameters remain unchanged during the measurement.
The resulting signal is expressed in units of voltage, current or
digital code will be used to analyse the surface temperature of an
object of control using methods monospectral and multispectral py-
rometry methods.
It is known that the multispectral pyrometry method is based on
equality of the spectral luminosity relation of real body and abso-
lute black body (ABB),
0 11
2 0 2
( , )( , )
( , ) ( , )
c
c
M TM T
M T M T
; (9)
М(1,T) and М(2,T)—spectral luminosity body wavelengths 1 and
2, М0(1,Tс) and М0(2,Tс)—spectral luminosity ABB wavelengths
1 and 2 with temperature Тс.
Further, les us determine the value of the surface temperature of
an object of control using the following ratio:
1 0 1 0 1
2 0 2 0 2
( ) ( , ) ( , )
( ) ( , ) ( , )
c
c
M T M T
M T M T
, (10)
where (1), (2) are coefficients of emissivity of wavelengths 1, 2.
Combination of Planck’s formula [21] and Eq. (10) results to
1 1
1 2 2 1 2 1 2
ln ( ) ( ) ( ) ( )
c
T T C . (11)
152 M. O. MARKIN, O. M. MARKINA, and S. M. KUSHCHOVYI
Analysing the formula (11), we have that, for (1) (2), value
T equals to value Tc, in other cases the true surface temperature of
an object of control can be both higher or lower than temperature of
spectral ratio. Indeed, if 2 1, then the sign of difference T Tc
is determined by ratio between (1) and (2). If (1) (2), then
T Tc, and if (1) (2), T Tc.
Using the concept of equivalent wavelength (EW), that is a sym-
bol of a wavelength ex of monochromatic radiation, under which
the output device forms the same signal as under the real radiation,
it allows us to rewrite formula (11) in a form
1
2
2
( )
ln
( )1 1
ex
c
T T C
, (12)
where
1 2
1 2
ex
. (13)
Thus, as we see from dependence (12), multispectral pyrometry is
also one of the methods that may solve the problem of measuring
temperature parameters in the area of melting at the DC of rotor
blades of GTE.
3. CONCLUSIONS
Reviewing and analysing the known methods and ways of measur-
ing the temperature parameters in the area of melting at the DC of
rotor blades of GTE, we found that further progress and develop-
ment of instruments for analysing temperature pyrometry gets a
higher priorities.
After analysing the main ways of pyrometry development, we
highlighted a number of problems whose solution will bring many
benefits in the use of non-contact measurement tools. One of the
most important is elimination of the effect on the result of meas-
urement of the spectral dependence f() and other factors, that
affect the accuracy of temperature measurement of PSR. As a solu-
tion to this problem, we suggested to calculate the optimal number
of the wavelengths that should be measured.
We found that the task of measuring the temperature parameters
in the area of melting at the DC of rotor blades of GTE could be
solved by using as spectral ratio as a way of control. It should be
noted that spectral pyrometry ratio is quite expensive, compared to
the radiation one.
TEMPERATURE OF MOLTEN ZONE AT THE CRYSTALLIZATION OF BLADES 153
We also found that measuring the temperature parameters in the
area of melting at the DC of rotor blades of GTE could be imple-
mented with imaging pyrometry. At the same time, a significant
number of issues of imaging pyrometry that are important in theo-
retical and practical aspects have not received adequate coverage. In
particular, the scientific and technical literature has no systematic
data about hardware of multispectral imaging pyrometry, reliably
results of their use in scientific or technological practice.
We made a conclusion about the need for further study of spec-
tral and imaging pyrometry as a means of measuring the tempera-
ture in the area of melting during directional solidification, as both
methods can solve the problem.
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