Vibration Diagnostics

Our company has a long-term experience in the vibration diagnostics of a gas turbine engine technical condition. Significant progress has been made in our works carried out for the MMZ Chernyshev, JSC Gazturboservice, JSC TyumenMotor. The last work satisfied all requirements for the vibration diagnostics system architecture. The architecture is irrespective to the hardware basis of the system.

Test cell System

The test cell systems operate in control and acceptance tests and for engine in-field maintenance. The system data acquisition and processing may be presented as the following six main levels:

Collection of the signals from sensors that control the engine operation, amplification, filtering, analog signals transmission signal conversion into a digital format;
Primary online data processing. The received signals are sampled in the time domain, recorded in the database (DB), compressed, archived and translated from the time domain into the frequency one. Data also can be obtained from a computer model;
The technical condition monitoring. The obtained values of the engine process parameters are compared with the expected or limit values that determine the permissible or emergency values. The obtained estimates can be used for the on-line technical condition diagnostics;
Special diagnostic algorithms application that describe the real technical condition of certain parts, assemblies or the engine as a whole. The specific feature is determined with the indication and ranking, parametric and vibration passports of the engine are formed. The repair technological processes perfection are assessed;
The engine assemblies, components and parts technical condition forecast is made. At this level, an assessment of how the defect will develop and the equipment residual life can be obtained;
The interface level enables the operator to visualize and record information of all types and levels. The system an answers the question why the diagnosis or prediction is made.

Each data processing level is directly linked to the previous one. Higher levels use information from the lower ones. For example, at the monitoring level the spectral characteristics of vibration signals are used to quickly assess the current state. The parameters that determine the engine processes are used to diagnose the state in trend analysis. The current state of the engine is used for prediction of the possible defect development, etc.

The facility systems exchange data with each other. The parametric control and diagnostics system receives data from the ACS. The ACS receives additional data from the vibration monitoring and diagnostics system.

The main types of technology used at various levels of data processing are the following. In OSA/CBM standard terminology, the technology can be represented by the following matrix.

Vibration Passport

One more result of the DYNAMICS R4 computer simulation is the addition to the engine vibration passports which differs from the standard representation.

The engine vibration passport is usually determined as a set of temporary realizations from vibration sensors, as well as their representation in the frequency domain, i.e. in the form of engine vibration spectrum in a certain frequency range obtained in several steady state or transient modes.

It is formed during the engines control test by measurement of the vibrations in steady and transient engine operation modes. The unsteady modes include all transient modes and run-out of the rotors after idling. The vibration passport contains information obtained for each sensor during the test process.

The vibration passport works that we carry out are the following:

Preparation and analysis of the DYNAMICS R4 engine model.
Formation of the vibration passport constant part based on the calculated results in DYNAMICS R4.
Formation of the test program to determine the vibration passport variable part.
Preparation of the structure and programming of the database to record the results.
Tests according to the established program and data collection.
Received signals processing and analysis in the time and frequency domains.
Selection of vibration parameters for monitoring the technical condition of the engine.
Determination of the selected parameters limit values to be included in the vibration passport of the engine.
Preparation of algorithms for recognition of defective situations in the case of deviations of vibration characteristics from the vibration passport ones.
And others.

All these works actually precede the creation of software tools for recognition the technical condition of a particular engine for introduction into the monitoring and forecast systems that use the vibration diagnostic algorithms.