FR2749884A1 - METHOD FOR CONTROLLING A TURBOJETACTOR - Google Patents

Abstract

Method for regulating a turbojet comprising a high pressure compressor, a combustion chamber and a high pressure turbine, in which the rotor fins of the high pressure turbine are cooled by means of cooling air from the high pressure compressor. The temperature of the rotor fins (Tmetal) of the high pressure turbine is measured to prevent overheating. According to the invention, a relative temperature (Trel) at the inlet of the rotor is determined from measured values of the outlet temperature of the compressor (T3), of the temperature of the rotor fins (Tmetal) and of a value (etaK) of the cooling efficiency of the rotor fins. This representative value is used to regulate the motor so that there is no overheating.

Description

The present invention relates to a method for

  regulation of a turbojet comprising a high pressure compressor, a combustion chamber and a high turbine

  pressure of which the rotor blades of the high-pressure turbine

  are cooled by cooling air supplied by the high pressure compressor, the temperature of the engine fins being measured to prevent overheating. In a turbojet, the power of the turbine depends directly on the outlet temperature of the combustion chamber which must not exceed a maximum value, otherwise there is a risk of overheating of the turbine parts

  and in particular the input guide ring. The weather

  Exhaust temperature of the combustion chamber can not be

  to measure directly, also in practice we measure a temperature

  erosion in the turbine area. For this purpose, thermoelements or pyrometric measuring devices arranged upstream or downstream of the low pressure turbine are used.

  directly measure the temperature of the fins of the tur-

  high pressure or low pressure turbine.

  For a pyrometric measurement, it is essential to use

  the average temperature of the rotor blade metal at a representative radius of the turbine. In the case

  of an engine in which the blades of the turbine are

  cooled by the cooling air coming from the outlet of the high-pressure compressor, the temperature does not depend solely on the temperature of the main flow gas but

  also the temperature of the cooling air.

  As the cooling air of the high pressure turbine

  comes from the output of the high-pressure compressor, its temperature

  ture depends directly on the operating point of the com-

  presser. In the case of different air and power measurements of the high-pressure shaft, for a constant temperature of combustion chamber outlet, the point of

  operation of the high-pressure compressor and the temperature

  cooling air change while the temperature of

  relative height with respect to the rotor of the high pressure turbine remains constant. Because the air temperature

  of cooling changes with the air intakes and

  the temperature of the metal changes as well. An adjustment according to a predetermined metal temperature as

  this is usually done nowadays for turbo-jet engines.

  the combustion chamber outlet temperature changes with the intake of air and power. This can lead to overheating

  static parts of the turbine and in particular of the

  guideway in the case of a strong air intake

and power.

  The object of the present invention is to provide a method for regulating a turbojet engine enabling the combustion chamber outlet temperature to be adjusted to a constant temperature, independently of the air intake and the temperature of the combustion chamber.

  power, without measuring the quantities of air and power.

  For this purpose, the invention relates to a method of the type defined above, characterized in that: - a representative relative temperature at the rotor inlet (Trel) is determined from the measurement values of

  the outlet temperature of the compressor and the temperature

  rotor blades and a YK value of

  cooling and the relative temperature (Trel) is used to regulate the

  reactor, so that there is no overheating.

  An essential advantage of the process according to the invention

  tion is that the static parts of the high pressure turbine

  are protected against exceeding the temperature without the need for measuring the quantities of air and

power take-off.

  According to a development of the invention, from the temperature relative to the rotor inlet, it is determined,

  by means of an empirical correlation, a temperature of

  combustion chamber or an absolute rotor inlet temperature and the engine is regulated so that

  the combustion chamber outlet temperature or the temperature

  rotor inlet temperatures do not exceed a pre-determined

  completed. This has the advantage that with the combustion chamber outlet temperature or the rotor inlet temperature, there is an absolute temperature value which must not exceed a predetermined temperature, or a maximum value, to avoid damage. caused to the turbine by

overheating.

  According to another embodiment of the invention,

  measures the temperature of the rotor blades by means of a py-

  radiation meter and the value of the temperature is used.

  of the fins measured by the pyrometer to determine the

  representative relative temperature.

  According to another characteristic of the invention, the value of the cooling efficiency is taken as constant.

  According to another embodiment of the invention

  the value of the cooling efficiency is determined

  based on the engine operating parameters.

  This has the advantage that the value of the temperature

  present on the rotor inlet and, if applicable, the values delivered from that of the outlet temperature of the combustion chamber, or the inlet temperature of the rotor can be determined with even more

  precision and which makes it possible to increase the power of

without risk of overheating.

  According to another development of the invention, the

  combustion chamber outlet temperature or temperature

  Absolute input of the rotor is obtained from the

  temperature relative to the rotor inlet by means of a relative

  which includes the speed of rotation of the

as a variable.

  In this case, the absolute temperature can be

  the rotor input from the relative rotor input temperature by means of the function: T41 / Trel = f (NH / T411 / 2 1 / 2- NH / T41 being the corrected rotation speed NH, the

high pressure turbine.

  According to the invention, the temperature is measured directly.

  output temperature of the high pressure compressor.

  According to another characteristic of the invention, the outlet temperature of the high-pressure compressor is established from operating parameters of the engine. According to another characteristic of the invention, the outlet temperature of the high-pressure compressor is used directly to determine the relative temperature

at the rotor inlet.

  Finally, according to another characteristic of the invention, in order to determine the temperature relative to the rotor inlet, a value obtained from the outlet temperature of the high-pressure compressor and other operating parameters of the engine which serve for the temperature of the cooling air in the area

rotor blades.

  An exemplary embodiment of the invention will be

written using the single figure.

  The figure shows very schematically, a reaction

  to describe the exemplary embodiment of the method according to the invention. As shown in the figure, the reactor to be regulated,

  according to the method of the invention, comprises a chamber of

  bustion 2, a high-pressure compressor 1 connected upstream to the combustion chamber 2 and a high-pressure turbine 4 connected downstream to the combustion chamber 2 rotated by the gas flow supplied by the combustion chamber 2 and

  driving the high pressure compressor 1 by a shaft 6.

  Part of the airflow leaving the high pressure compressor

  sion 1 bypasses the combustion chamber 2 to cool

  the rotor blades of the high-pressure turbine 4. A

  low pressure presser, not shown, can be mounted downstream of the high pressure compressor 1, likewise, a low pressure turbine, not shown, can be mounted downstream of

the high pressure turbine 4.

  The air, at a temperature T1 and a pressure P1 sucked by the reactor, is compressed by the high compressor

  pressure 1 and is delivered at a temperature T3 and a pressure of

  P3. The main part of the air delivered by the com-

  1 high pressure press enters the combustion chamber 2 to be burned with the fuel supplied. At the outlet of the combustion chamber 2, the gas flow has a combustion chamber outlet temperature T4 and a pressure P4. A

  part of the cooling air is mixed with the main flow

  in the inlet guide ring 3 of the high-pressure turbine 4. The temperature then drops from T4 to T41 and

  the pressure of P4 to P41. The flow of gas, entering the tur-

  4, is then at the temperature T41 and at the pressure P41. The part of the compressed air delivered by the

  high pressure compressor 1 bypassing the chamber

  bustion 2 for the cooling of the rotor blades of the

  high pressure turbine 4, leaves the high pressure compressor

  sion 1 also at temperature T3 and reaches the fins

  of the rotor in the form of cooling air at room temperature.

  TK. The temperature of the gas flow can be described by a representative, representative temperature at the entrance of the Trel rotor. Between this relative temperature Trel, the temperature of the cooling air TK and the temperature of the metal

  Tmetal measured at the metal of the rotor blades, we have a relationship

  given by the cooling efficiency of the

  Tes: Trel-Tmetal (1 Trel - Tk) The temperature of the Tmetal rotor blades can be measured by means of a pyrometer 5. As the temperature of the cooling air

  TK is closely coupled with the outlet temperature of the

  pressure T3, the previous formula can be solved according to the relative temperature Trel at the rotor inlet: Tmetal - Ik T3 Trel 1 (2) Thus, one can determine the relative temperature Trel at the rotor inlet from the values of the measures of

  compressor outlet temperature T3 and the temperature

  Tmetai rotor blades and the% K value for the cooling efficiency of the rotor blades. This value of the relative temperature Trel is that used for

  regulate the motor so as to avoid overheating the tur-

  high pressure 4 and more particularly of the crown

input guide 3 fixed.

  From the relative temperature Trel to

  the rotor inlet, it is possible to obtain, by means of a correlation

  empirical example, the outlet temperature of the chamber of

  T4 combustion or the inlet temperature of the rotor T41 in re-

  close relationship with it. To avoid overheating parts 3 and 4 of the high pressure turbine, the engine is

  adjusted so that the outlet temperature of the chamber

  Combustion point T4 or the inlet temperature of the rotor T41 does not exceed a predetermined value, or a maximum value.

  The cooling efficiency% K is approximately

  a constant. Following a more precise observation, it turned out that lK depends only slightly on Reynold's number. The temperature profile, radial, of the gas flow

  leaving the combustion chamber 2 can influence local-

  the cooling efficiency lK. In addition, there is a relationship between the outlet pressure P3 and the temperature of

  T3 output of the high pressure compressor 1.

  There is a close relationship between the relative inlet temperature of the Trel rotor and the absolute temperature

  input of rotor T41. As can be shown, by

  continuity (constant air system) in the turbine, the ratio of the absolute inlet temperature of rotor T41 and

  the relative representative temperature Trel depends exclusively

  1/2 of the corrected rotation speed NH / T41 1 NH being the speed of rotation of the high pressure turbine: T41 / Trel = f (NH / T4 1/2) (3) This function can be for example put under

  table form and be used for the regulation of the

  tor. Thus, the inlet temperature of the rotor T41 can be

  determined according to the speed of rotation of the tur-

  bine NH and the relative temperature Tre1 representative. The latter can itself be calculated from the

  Tmetal temperature of rotor blades measured by the disc

  the pyrometer, the compressor outlet temperature T3 and the cooling efficiency% K of the

  rotor fins, as shown previously.

  The combustion chamber outlet temperature T4 can be easily determined from the inlet temperature of the rotor T41 by means of a multiplication by a

constant factor.

  According to the process of the invention, instead of a limit value for the temperature Tmetal fins

  of the turbine measured by a pyrometric measuring device

  that a motor value is used for the regulation of the engine

  mite of the outlet temperature of the combustion chamber T4 or the inlet temperature of the rotor T41. Thus, the parts of the turbine, in particular the static parts 3

  can be guaranteed against the high temperatures that

  appear in conventional regulation by the measures

  large quantities of air and significant power.

  The measurement of the amount of air and the power is not necessary.

Claims (10)

R E V E N D I C A T IONS   1) A method of regulating a turbojet comprising a high pressure compressor, a combustion chamber and a   high-pressure turbine, including the turbine rotor blades   high pressure are cooled by cooling air supplied by the high-pressure compressor, the   rotor blade temperature of the high pressure turbine   is measured to prevent overheating, characterized in that a representative relative temperature at the rotor input (Trel) is determined from the measured values of   the outlet temperature of the compressor and the temperature   rotor blades and a value (1K) of the efficiency   cooling and the relative temperature (Trel) is used to regulate the   reactor, so that there is no overheating.   2) Method according to claim 1, characterized in that   from a relative temperature (Trel) at the entrance of the rock   tor, a combustion chamber outlet temperature (T4) is determined by an empirical correlation and the engine is regulated so that the outlet temperature of the combustion chamber   combustion (T4) does not exceed a predetermined value.   3) Process according to claim 1, characterized in that an absolute rotor inlet temperature (T) is determined from the relative temperature at the rotor inlet (Trel) by means of a correlation. the engine so that the rotor inlet temperature (T41) does not   does not exceed a predetermined value.   4) Method according to one of claims 1, 2 or 3,   characterized in that the temperature of the rotor blades is measured by means of a radiation pyrometer and the value thus measured is used with the pyrometer of the temperature of the fins of the rotor.   rotor (Tmetal) to determine the relative temperature repre- sentative (Trel) -    Method according to one of claims 1 to 4,   characterized in that the value of the cooling efficiency (1K) is considered like a constant.   6) Method according to one of claims 1 to 4,   characterized in that the value of the cooling efficiency (11K) is determined as a function of the operating parameters of the motor.   7) Method according to one of claims 2 to 6,   characterized in that the combustion chamber outlet temperature (T4) or the rotor inlet absolute temperature (T41) is determined by means of a functional relationship in which the velocity   of motor rotation is the variable.   8) Process according to claim 7, characterized in that the absolute inlet temperature of the rotor (T41) is determined from the relative temperature at the rotor inlet (Trel) by means of the functional relationship: T41 / Trel = f (NH / T41 1/2)   NH / T411 / 2 being the corrected rotation speed NH of tur- high pressure.   Method according to one of claims 1 to 8,   characterized in that the outlet temperature of the high pressure compressor (T3) is measured directly.    Method according to one of claims 1 to 8,   characterized in that the high pressure compressor outlet temperature (T3)   is determined from parameters of use of the tor.   11) Method according to one of claims 1 to 10,   characterized in that the outlet temperature of the high pressure compressor (T3) is used directly to determine the temperature of the   operation at the rotor inlet (Trel) -   12) Method according to one of claims 1 to 10,   characterized in that for determining the temperature relative to the rotor inlet   (Trel) we use a value obtained from the temperature   output of the high-pressure compressor (T3) and other engine operating parameters for the cooling air temperature in the area of the rotor blades of the high pressure turbine.   13) Method according to one of claims 1 to 12,   characterized in that the high pressure compressor, the combustion chamber and the   high-pressure turbine are part of a gas turbine with several trees.