Bladed Wheel Research Articles

Dry Friction Interblade Damping by 3D FEM Modelling of Bladed Disk: HPC Calculations Compared with Experiment

Interblade contacts and damping evaluation of the turbine bladed wheel with prestressed dry friction contacts are solved by the 3D finite element method with the surface‐to‐surface dry friction contact model. This makes it possible to model the space relative motions of contact pairs that occur during blade vibrations. To experimentally validate the model, a physical model of the bladed wheel with tie‐boss couplings was built and tested. HPC computation with a proposed strategy was used to lower the computational time of the nonlinear solution of the wheel resonant attenuation used for damping estimation. Comparison of experimental and numerical results of damping estimation yields a very good agreement.

Acoustic Identification of Turbocharger Impeller Mistuning—A New Tool for Low Emission Engine Development

At present, exhaust gas turbochargers not only form the basis for the economical operation of petrol, diesel or gas engines of all power categories, but also have an irreplaceable role on reducing their emissions. In order to reduce emissions from internal combustion engines, various systems are being developed, all of which have a turbocharger as an important component. Demands on turbocharger system durability and reliability keep growing, which requires the application of increasingly advanced computational and experimental methods at the development beginning of these systems. The design of turbochargers starts with a mathematical description of their rotationally cyclic impellers. However, mistuning, i.e., a slight individual blade property deviation from the intended design parameters, leads to a disturbance of the rotational cyclic symmetry. This article deals with the effects of manufacturing-related deviations on the structural dynamic behaviour of real turbine rotors. As opposed to methods exploiting expensive scanning vibrometers for experimental modal analysis or time-consuming accurate measurement of the geometry of individual blades using 3D optical scanners. A suitable microphone and a finite element rotor wheel model are the basis of this new method. After comparing the described acoustic approach with the laser vibrometer procedure, the results seemed to be practically identical. In comparison with the laser technique the unquestionable added value of this new method is the fact that it brings a significant reduction in the financial requirements for laboratory equipment. Another important benefit is that the measuring process of bladed wheel mistuning is significantly less time-consuming.

Laboratory Tip-Timing Optical Measurement System of Rotating Blade Vibrations

The multipoint optical system, based on fast optical elements, for precise laboratory measurements of vibration of turbine blades under rotation was proposed in the IT AS CR. The optical system registers time passages of the blades. The paper describes optical sensor, test setup with measuring and excitation systems, results of numerical simulations and the first experimental results on the bladed wheel under rotation.

Interaction force between magnetic field and ferromagnetic target: analytical, numerical and experimental study

In this study, an analytical model and a finite element (FE) model were developed in order to study the force produced by a permanent magnet on a ferromagnetic target. The study was aimed at estimating the magnetic action in order to design an excitation device for vibration tests. The dynamic analysis of rotating structures as compressors’ bladed wheels requires a solicitation that reflects the operational conditions. If the component is made of ferromagnetic material, it is possible to use magnetic fields for the excitation. The present paper reports the interaction between planar parallel surfaces, first studied analytically and numerically, and the results were compared with experimental results. Then the interaction between sloping surfaces was analyzed, allowing an analytical boundary loss model to be developed. Finally, the FE model was improved to study the interaction between double curvature surfaces. A comparison with experimental results measured on an actual bladed wheel was performed.

Analytical investigation of the SAFE diagram for bladed wheels, numerical and experimental validation

Compressor and turbine bladed wheels interact with the fluid distributed by the stator vanes. They are subject to vibration and fatigue loading, especially when resonance conditions are excited. Avoiding resonance is fundamental when designing bladed wheels. The Campbell diagram approach is too conservative since bladed wheels show many close frequency natural modes, thus it is almost impossible to avoid frequency matching. Singh׳s Advanced Frequency Evaluation (SAFE) diagram, or interference diagram, also introduces shape matching in addition to the frequency, for resonance prediction, therefore many frequency matching cases can be identified as non-critical and thus tolerated. The present paper explains and demonstrates the SAFE diagram by introducing an analytical expression to identify bladed wheel resonance conditions. The mode shape matching with a harmonic component is investigated by means of specific examples. Symmetry properties of the matching distribution of harmonic indices and mode shapes are also introduced and demonstrated. Finally, a bladed wheel analysis is used for validation, both in FE simulations and experiments.

The Maximum of the Theoretically Possible Exploitation of Wind by Means of a Wind Motor

Considering the current shortage of coal, the exploitation of the energy of wind has generated considerable interest. For this reason, it is the ambition of the engineer to convert this energy into a usable form with the highest possible efficiency. Furthermore there arises the problem that for wind motors, the efficiency term is not as explicitly defined as it is for most other machines. Since the energy which is available in the wind is in reality infinitely big; in essence, it therefore depends on the size of the wind motor how much of this energy is converted. To obtain a reasonable measure for the efficiency, an energy parameter for input power must be introduced, which is proportional to the size of the motor (proportional to the area of the bladed wheel). We can consider for example the windmill as the inverse of a propeller by imagining that the wind wheel is moved through stagnant air at a speed corresponding to the wind velocity v in the axial direction, which has the same effect as the air blowing with this velocity against the wheel. With this concept of operation, it is implicity clear that this introduced energy is the same energy that is necessary for the axial movement of the wheel. If the wind pushes in an axial direction on the wheel with a force P, then the energy per second has the value P ⋅ v, and if the useful power ouput of the wheel at the shaft has the value L, thus this yields the efficiency.

High revolution chemical motor with biocatalytic reaction

A chemical motor was constructed by a catalase immobilized tube-pump and a micro turbine system was developed and demonstrated. The catalase tube-pump produced an active pressure of oxygen vapor at the tube-inside by applying hydrogen peroxide to the tube-outside as chemical energy, resulting in the oxygen gas flux. The micro bladed wheel of the artificial turbine was revolved by the oxygen flux from the tube-pump, thus the rotational velocity was correlated with the H2O2 concentration. The potential applications of the chemical motor will allow to develop some intelligent biomimetic machines.

Questions on the Crookes Tube Experiment of Rotating a Bladed Wheel

Questions on the Crookes Tube Experiment of Rotating a Bladed Wheel

Computer Aided Analysis of Turbine Blade Vibration Test Data

A pilot system has been developed which automatically scans and evaluates experimental vibration data obtained from a test rig replica of a bladed wheel of a turbine in service. High vibration amplitude signals are selected for further analysis. This data is converted into digital form using an analogue to digital converter and is processed in a digital computer suitably programmed for harmonic analysis. The results are plotted on a Campbell Diagram using an on-line digital X-Y plotter which gives a visual record of the most salient information from the tests in a readily interpreted form. The paper describes the equipment used, the method of converting the analogue-type signals to digital form, analyses the accuracy of the conversion method, and gives the reasons for undertaking such vibration analysis.