RU2258923C1 - Method of diagnosing gas turbine engines at steady and non-steady states of operation - Google Patents

Abstract

FIELD: measurement engineering.

SUBSTANCE: method can be used for diagnosing technical condition of gas turbine engine during production, test and exploitation. Electro-static aerial is mounted behind cut of nozzle outside engine and its reactive gas-dynamic jet for registering pulsation of electric field generated by charged particles (electrons, ions, microscopic particles) which attend in moving jet. Dispersion σ_j is calculated from set of N points of registered signal during period of inspection in preset time period within preset time interval. Characteristic frequencies are determined in spectrum of registered signal and calculated dispersion of σ_j is compared with preset and determined in advance, reference value of σ^*. If σ_j exceeds the bounds of preset range and there are frequencies in spectrum range being different reference ones, the failure is supposed to take place.

EFFECT: increased efficiency of diagnostics; reduced time for diagnostics.

3 dwg

Description

The invention relates to the field of measuring equipment and is intended to improve the efficiency and efficiency of diagnostics of the technical condition of gas turbine engines in the process of their production, testing and operation.

In recent years, unconventional methods for diagnosing gas turbine engines have been widely developed. Such methods include the method of non-contact diagnosis of the state of gas turbine engines. The method is based on the registration of charged particles (electrons, ions, microparticles) in aircraft engine jets. These particles are formed in the combustion chamber during the combustion of the air-fuel mixture, during erosion and destruction of engine elements, or enter the engine from the outside. Charged particles create an unsteady electrostatic field in the space surrounding the gas-dynamic motor jet, which is detected by special probe antennas. Based on the received signals, it is possible to obtain information about the processes occurring in the engine, to identify and predict the anomalies present in it. This increases the safety of operation of aircraft, reduces the cost of its maintenance and ensures the speed of decision-making.

There is a known method of registering engine malfunctions, patent US 5552711 from 09/03/1996, based on the analysis of the frequencies of electromagnetic radiation of various types of ions in the engine jet, which arise both when the air-fuel mixture burns in the combustion chamber and when (and combustion) occurs in the flow part a gas turbine engine of metal particles formed by erosion or destruction of engine elements.

The disadvantage of this technical solution is that this method is quite complicated and difficult to apply in practice because of the need to accurately determine the radiation frequency of the detected ions of various types, to identify differences between ions that occur when the engine malfunctions from ions that appear in the engine stream as a result of processes occurring in serviceable engine. An additional complication is the need to take into account the influence of the earth's magnetic field on the measurement results.

The closest technical solution to the claimed and adopted as a prototype is the method of electrostatic diagnostics described in patent US 4607337 from 08/19/1986 and in the article Couch R.P. Detecting abnormal turbine engine deterioration using electrostatic method, AIAA Paper No. 1473, 1978, which describe methods of installing electrostatic probes for detecting charged particles and algorithms for processing the information received. In the process of operation, signals from three probes installed in the engine flow part are recorded and analyzed, and based on the established criteria, a conclusion is made about the presence and type of deviations from the normal operation of the diagnosed engine.

The disadvantages of these methods are: the need for special preparation of the engine to install three probes inside it; the need for a fairly complex analysis according to more than 10 criteria, the values of which may depend on the particular engine being diagnosed; the lack of spectral analysis, which allows you to determine the malfunction of the engine by the characteristic gas-dynamic or motor frequencies of the recorded signal. All this complicates the decision on the health or malfunction of the engine.

The technical task of the proposed method is to increase the efficiency and efficiency of diagnosis of the technical condition of gas turbine engines during their testing and operation.

The technical result is achieved by the fact that behind the nozzle exit, outside the engine and outside its jet gas-dynamic jet, an electrostatic antenna is installed to detect pulsations of the electric field created by charged particles (electrons, ions, microparticles) present in the jet. Engine health monitoring is carried out by conducting a statistical analysis of the registered signal, the variance σ _{j is} calculated from a sample of N points of the registered signal during the monitoring time T, after a specified period of time τ _p , at a given time interval τ, the characteristic frequencies in the spectrum of the registered signal are determined, and the calculated variance σ _j with a predetermined, predetermined, reference value σ *. When the value of σ _{j is} outside the specified range and the frequency spectrum is different from the reference ones, the engine operation parameters are monitored (n _VD or t _T *) and a “Failure” signal is generated when their limit values are reached.

Figure 1 presents a diagram of an electrostatic antenna for detecting charged particles in aircraft engine jets.

Figure 2 presents a typical time scan of the recorded signal.

Figure 3 presents the algorithm for diagnosing a gas turbine engine in steady unforced modes.

The electrostatic antenna shown in Fig. 1 consists of a sensing element - a metal rod 7, surrounded by a metal cylindrical screen 2 with a slot providing an antenna viewing angle of 90 °. The sensitive element and the screen are fixed in insulators and mounted in a platform 3, also made of insulating material. A standard connector 4 of type СР-50 is inserted into platform 3 for connecting a preamplifier or equipment for recording, recording and processing signals, as well as docking a metal case 5 for directly attaching the antenna to standard airfield devices. Fixation of the antenna in the place of attachment is provided by means of a locking screw 6.

A typical time scan of a signal recorded using an electrostatic antenna is shown in FIG. 2. This signal is analyzed using the algorithm shown in FIG. 3.

The implementation of the proposed method for the diagnosis of gas turbine engines in steady and unsteady operating modes is as follows.

1. Choose the time T control, for example, the duration of the ground race T = 20 minutes

2. For control, establish the duration of any steady state for a predetermined time τ _p = 1 min.

3. Enter the reference dispersion characteristic of the recorded signal (σ _n = f (n _VD ) or σ _f = f (t _T *) and assign the tolerance to the signal variance σ *. Introduce the characteristics σ _n = f (n _VD ) or σ _f = f (t _T *) and the purpose of σ * must be preceded by tests of the engine.

4. Measure the low-frequency parameters α _RUD , n _VD , t _T *.

5. At the end of the steady state, in a section of duration τ = 1 s, N = 2048 signal points are processed to calculate the current dispersion value using the formula,

where f _i is the signal level, i = 1 ... N.

6. Compare the obtained value of the parameters σ _j ≤σ *.

7. If the condition is met, then the standby mode for τ _p = 1 min follows.

8. If the condition is not met, then without delay, two control variance values σ _{j + 1} ≤σ * are satisfied; σ _{j + 2} ≤σ *.

9. In case of failure to fulfill two control conditions, the engine operating mode is monitored by parameters n _VD , t _T ^* .

и в дальнейшем производят корректировку параметра σ* к новым n_ВД (t_T ^*) и возврат к режиму ожидания.10. In the absence of limit values n _nd and t _T ^* , the condition is checked

and subsequently, the parameter σ * is adjusted to the new n _VD (t _T ^* ) and returns to the standby mode.

11. If the parameter values according to claim 9 reach the specified limit levels, then the mode is reduced and a malfunction is detected,

where n _VD is the rotational speed of the high pressure rotor;

t _T ^* is the gas temperature behind the turbine;

α _ores - angle of rotation of the engine control lever;

T is the control time;

τ _p - the duration of the steady state;

τ is the signal recording time;

σ _n , σ _f - reference values of the dispersion of the signal of a working engine;

σ * is the maximum permissible signal dispersion value;

N is the number of points by which the dispersion is calculated;

F _i - signal level at the i-th point;

σ _j is the current value of the signal dispersion;

n _{VD pre} , t * _Tpred , α _{ores max} - the maximum values of the rotational speed of the high pressure rotor, gas temperature behind the turbine and the angle of rotation of the engine control lever.

In this case, the characteristic frequencies ω in the spectrum of the recorded signal according to the power spectrum of this signal. The frequencies are compared with the characteristic frequencies σ * for a given engine operating mode, and the appearance of frequencies other than the reference ones in the signal spectrum indicates a malfunction in the engine.

The introduction of a signal from the antenna when detecting the limiting levels n of the _VD or ω * (the "Limit vibrations" parameter can be added) allows the σ * parameter to detect malfunctions associated with erosion, destruction of engine structural elements, and deterioration of combustion in the main combustion chamber.

The behavior of the signal associated with an increase to a maximum level and a subsequent decrease in its amplitude in transient modes should not be considered an anomalous mode. In the process of pick-up, studies have shown that there is a fairly quick adjustment of the time base and the spectrum of the electric signal. In contrast to the change in gas-dynamic parameters over time Δt, which occurs monotonously, the change in the signal is nonmonotonic and is characterized by the presence of sharp maxima. It should be noted that a constant increase in the signal level to the maximum value occurs when dosing the excess fuel consumption in the main combustion chamber by the automatic pickup of the automatic engine control system.

The introduction of a limit signal along with the appearance of a signal with levels n _VD = n _{VD pre} or t _T ^* = t ^* _{T pre} increases the reliability of the detection of malfunctions and the effectiveness of monitoring the technical condition of gas turbine engines, since the presence of limit parameters n _{VD pre} and t ^* _{T pre} can It can also be caused by other factors, for example, changes in environmental conditions, for example, high air temperature at the engine inlet, gusts of wind, errors or ACS failures, and the appearance of the “Ultimate Vibrations” signal can result from failures of the measurement equipment Vibration rhenium.

When diagnosing gas turbine engines under steady-state conditions, it is necessary to correctly select the time sections for monitoring and take into account when analyzing σ * the peculiarity of the signal change at transient engine operating modes when calculating the parameters σ _{j + 1} and σ _{j + 2} .

The proposed method for non-contact diagnostics of gas turbine engines at regular steady and unsteady modes of its operation allows, when used, to reduce operating costs and time for diagnostics both during pre-flight and inter-flight preparation of the engine, provides high accuracy of registration of charged particles in aircraft jet engines, thereby increasing the safety of its flight operation.

Claims (1)

A method for diagnosing gas turbine engines in steady and unsteady operating modes, which consists in registering an electrical signal from a jet gas-dynamic jet of an engine using an electrostatic antenna and, based on the results of statistical signal processing, diagnose an engine malfunction, characterized in that the electrostatic antenna is installed outside the cut of the engine nozzle outside its jet gas-dynamic jet, the pulsations of the electric field created by the electrons are recorded, ons and charged microparticles present in the propulsion jet, determine the magnitude of the dispersion of the recorded signal according to the formula

where σ is the signal dispersion value; F _i - signal level at the i-th point; N is the number of points by which the dispersion is calculated, career frequencies are determined in the power spectrum of the registered antenna signal, the calculated dispersion σ is compared with a given reference value σ *, and if the calculated dispersion exceeds its reference value and the appearance of frequencies other than the reference ones in the power spectrum, they judge the presence of a malfunction in the engine.

Images