Our company carries out complex optimization studies at all machine life stages from design to in-field operation for the vibration mitigation and stability improvement. Our 20 years cooperation with the leading GT companies and dozens of R&D investigations allow their engineers deeper understanding of the product performance and solutions of practical problems.
Most problems are solved by application of the DYNAMICS R4 S/W system. The earlier S/W versions were used mostly for the critical speeds, forced oscillation and system stability limit calculations. Besides the current S/W version solves the production problems. In particular, determines the dynamic coefficients of influence (DKV), solves the issues of balancing flexible rotors, prepares programs for modal tests, solves the issues of technical condition diagnostics, etc.
Below we show the tasks solved by application of the DYNAMICS R4 software when carrying out certain R&D, for example is taken a turbojet engine.
The work subject may be formulated as “Simulation of the engine vibration characteristics, the turbomachine dynamic system study and optimization by means of the computer simulation methods, vibrational state and stability improvement.” Other task definitions may be formulated by the Customer.
Tasks To Be Solved in The Process of R&D
1. Creation of a model in the environment of the DYNAMICS R4 software system with the possibility of its use at the main stages of the life cycle – design, development, operation, including combat conditions and high overloads. The task is to bring the model closer to the real GTE system. Validation of the model using FEM programs, data from experimental studies and tests.
- Our experience shows that it takes at least 5-6 months to create a sufficiently detailed dynamic model of a modern engine. At the same time, model tuning largely depends on the specific task and may require additional time.
- It is important to note that the architecture of the model must have properties that make it easy to introduce any changes into it, as well as conveniently analyze the results. In the DYNAMICS R4 software system, special attention is paid to this problem. The model is built from assemblies, submodels, subsystems. Algorithms for carrying out variant calculations have been developed.
- In the dynamic system of the engine, there are a large number of units with non-linear characteristics that can significantly affect the overall dynamics of the engine (hydrodynamic dampers, rolling bearings, plain bearings, flange connections, etc.). For example, the stiffness of hydrodynamic dampers of bearing assemblies can vary several times depending onon eccentricity ratio and other operating conditions. It is very important to correctly assess the operating conditions of dampers in the engine system and their damping characteristics. With this in mind, the problem must be solved in a nonlinear approach, or to build quasi-linear models that take into account the change in parameters by modes.
2. Study of the influence of technological factors, manufacturing conditions (shape deviations), assembly conditions (tightening of bolted joints, support misalignment and misalignment of shafts), temperature factors on the general vibration state of the engine. Definition of “weak” structural elements. Determination of the initial imbalances of the rotors.
- To successfully solve problems of unbalance behavior, as well as balancing problems, it is necessary to determine the distribution of initial and assembly imbalances (based on drawing documentation), assign installation locations and values of balancing weights. The last task should be solved based on the results of the calculation of the forms of forced oscillations of the rotors, obtained by modeling in DYNAMICS R4.
- To solve particular problems related to the validation of mathematical models built in DYNAMICS R4 during modal testing, it is required to create technological models of parts and assemblies.
- Temperatures affect almost all stiffness and damping characteristics of the engine. Neglect of this factor leads to significant modeling errors.
- Shafts misalignments and rotor support misalignments can load flange connections, couplings, support units with additional dynamic forces.
3. Carrying out complex computational studies of the model under conditions of bench tests from various sources of excitation. Issuing recommendations for optimizing the structural elements of the engine, improving the method of balancing the engine rotors, determining the durability of the bearings of the support units using various unique methods that have been adopted by the Russian engine community.
- GTE casings are flexible structures that affect the overall dynamics of the engine. The engine mount makes their properties anisotropic. Failure to take this factor into account leads to errors in the results.
- The properties of the motor piping largely depend on the dynamic properties of the motor housing. The results obtained can be used in solving problems of kinematic excitation of pipelines and units, determining stresses in them.
- For ground-based vehicles, the dynamics of the structure largely depends on the properties of the engine mount, under-engine frame, and concrete base. All the functionality to account for these elements exists in DYNAMICS R4.
4. Problems of forced oscillations as a result of polyharmonic, impact, kinematic excitation, synchronous and non-synchronous excitation of rotors, contact of rotors with the stator, contact of shafts, transient processes in engine operating modes, as well as during aircraft evolutions with large overloads.
- All these processes largely determine the stress state of units and parts, as well as their durability. Problems can be solved only in a non-stationary approach.
- Study of the influence of kinematic (seismic excitation) excitation from the side on the behavior of the engine.
5. Study of self-oscillatory processes from various sources of excitation (sliding bearings, hydrodynamic dampers, dry friction dampers, labyrinth seals, aerodynamic forces in the blade rims of impellers, splined bushings, etc.)
- Self-oscillatory processes leading to increased vibrations, to the destruction of engine components, are often not diagnosed during tests, although they participate in the general vibrational behavior. The task of diagnosing and eliminating the sources of their occurrence is in many ways a priority task for the designer.
6. Study of torsional vibrations of the engine rotors and detuning from excitation frequencies. Calculation and analysis of the vibration characteristics of the CCU and gearboxes.
- As a result of the calculation, the natural frequencies of the structure, the loads in the bearings, the dynamic stresses in the gear pairs are determined (taking into account gaps, meshing errors). Problems of forced torsional vibrations of engines, vibrations of turbogenerators, etc. are being solved.
7. Analysis of dynamic loads in rotor bearings. Study of the effect of dynamic loads on their durability.
- Calculation of bearing life (ball and roller bearings) according to unique methods created in the company and accepted for use by the Russian motor community. Algorithms for calculating equivalent loads and durability are built into the DYNAMICS R4 software package.
8. Diagnostics through simulation is an actively developing area in our company.
- Analysis of signals received in measuring equipment during bench tests, determination of critical frequencies using amplitude-phase analysis, determination of natural frequencies of turbomachines, etc.
- Creation of algorithms for recognizing possible faults using both vibration signals obtained on the bench and using simulation results in the DYNAMICS R4 software system.
GTE-110 gas turbine power plant Project
Purpose of Work
Reduction of vibrational activity of the GTE-110 engine.
Tasks To Be Solved To Achieve The Goal
Creation of a model of the dynamic system GTE-110 power plant. Validation of GTE-110 model. Analysis of the dynamic system of the GTE-110 engine as part of power plant. Development of recommendations for reducing the vibration activity of the GTE-110 engine and improving vibration stability.
