Solutions

DYNAMICS R4 is the software set developed especially for design, analysis and troubleshooting in various rotating machinery. The research objects are gas-turbine engines, power plants, compressors, starters, turbo-expanders, turbo-driven pump plants, gear systems, etc. It can be also used for development of simulation based diagnostic algorithms.

DYNAMICS R4 is a software set to be used in the new machine design, to determine the possible causes of deterioration or the in-field failures, as well as to simulate the dynamic properties and further creation of vibration diagnostic algorithms.

The problem of partial or rough contact of a rotor with a stator also can be solved in the DYNAMICS R4 for almost any version of a rotating machine. The task is important, both for aircraft engines and for industrial units. Rubbing in a high power turbine unit can lead to catastrophic destruction of the entire power plant.

Based in the forty-year experience in rotor dynamics, the Alfa-Tranzit Ltd. company carries out engineering works under orders of various turbomachinery companies. Using Dynamics R4 the company specialists simulate the subjects of inquiry, carry out their analysis and find particular problem solutions.

The solution presents the problems related to the use of the active magnetic bearings in rapidly rotated rotors. The dynamic analysis results of the rotor supported by active magnetic bearings are given. The possibility to control the rotor system changing the magnetic bearing stiffness and damping is considered. The rotor system behavior during the rotor dropdown on backup bearings and the following runout are investigated.

DYNAMICS R4 was used for simulation of the balancing bench supplied by Diamech Co. and operating by Gasturboservice Co., Ltd. This bench was simulated modeled as a 3-D system. The calculations were carried out in two versions – without the rotor and with the rotor, set in its tooling.

The T53 engine drives the Orenda Aerospace Corporation 1.2MW power generator. This plant specific feature is its rotors contra-rotation. This work is a part of the performance and life enhancement of the T53 engine industrial application project. The simulation model provides the computer study of vibration response related to the rotors sliding changes and the frequency spectrum for direct and reverse precessions. As far as the rotors rotations are of opposite directions the rotors unbalances consequently excite the resonance vibrations corresponding to frequencies of the both rotors.

Oil whirl is a common problem with journal bearings used in machines equipped with pressure lubrication sleeve bearings systems operating at high speeds. If the shaft is moved off center due to load, eccentricity, or imbalance, then the clearance on one side of the bearing will be greater than that on the other side.
As the lubricant rotates at less than 50% of shaft speed, it must squeeze through the smallest clearance where the shaft is closest to the bearing. The average speed of the lubricant increases inside the gap and slows down when it leaves the gap. Such a speed up and slow down process creates turbulence on both sides of the gap, and a vortex develops in the high-pressure lubricant zone.

Laboratory test facility was created for the dynamics analysis of rotor with anisotropic (pendulum) supports (1975 Leontiev M.K.). Rotor system is simulated as uniaxial. The Dynamics R4 software allows creation of a complete 3D rotor model with all elements of the laboratory facility, calculating natural and critical frequencies, frequency response and precession orbits display.

The compressor test facility modification was supported by simulation of rotor structure. The rotor was modeled with the program Dynamics R4. This model includes the following units: Tested compressor, transmission shafts, intermediate support, additional support, мultiplier gearbox.

It is a calculation example of the power generator on 5 elliptical Journal bearings. Rotation speed is 3600 rpm. Initial model of the generator was built on beams, inertial elements and journal bearings which are modeled by flexible links. Using Xlpocket and XLTltpad nonsymmetrical stiffness and damping matrixes for all journal bearings (USA, Rotating Machinery Technology, Inc.) were calculated. Frequencies, mode shapes at 3600 rpm and stability maps was obtained. Critical speeds were calculated.

The goal of this work is the computer simulation of multiplier dynamic response which is used in the compressor facility assembly. Research was performed in the linear and nonlinear approaches. Calculations in linear and nonlinear assumptions were carried out to determine natural frequencies and mode shapes of combined bending-torsional vibrations. Calculations at nonlinear transient statement allow determination of the multiplier stability.

Multilevel model of two shafts gas turbine engine AL55 for study – training aircraft was created. Calculations of coaxial rotors were separately performed in two modifications: with case and without case. Frequencies and mode shapes, natural frequencies map, critical speeds were obtained. It is shown that taking into account a case changes the critical speeds spectrums.

This work is a part of the T53 engine industrial application project. The simulating model in this stage provides computational studies of vibration response of the T53 engine incorporated in the Orenda Aerospace Corporation 1.2 MW power generator. The multilevel model includes three sub-systems (sub-models) – core engine rotor (GP rotor), power turbine rotor (PT rotor) and case with mounting. Each sub-system includes a few smaller sub-systems. The model incorporates data of the engine layout, assembly and part drawings, used materials performance, etc. Accuracy of the model was checked by matching the model mass and inertial data and by comparison of calculated critical speeds with the available test data. It is worth mentioning that the earlier analysis investigated the engine aero version differing from the industrial one by the engine support structures and the front compressor support. Due to this difference the calculation results were not absolutely equal to the test data but the main performance of the sub-systems were in a good correspondence.

The work is determination of main resonant modes of the rotor drive train system ”GT25000 Power turbine – BRUSH generator” regarding all oscillation modes – bending, torsion and longitudinal ones. The following was done to accomplish this task:

• the rotor system model buildup;
• geometric and mass identification of the rotor system;
• calculation of natural frequencies and mode shapes;
• calculation of critical speeds and the corresponding mode shapes;
• calculation of forced oscillation under the influence of distributed unbalance system.

Modeling was carried out in the Dynamics R4.5 program system by the company Alfa-Tranzit Co., Ltd on the basis of the data provided by Magellan Aerospace.