Reducing Blade Force Response in a Radial Turbine by Means of Jet Injection

2019 ◽  
Author(s):  
Stephan Netzhammer ◽  
Damian M. Vogt ◽  
Stephan Kraetschmer ◽  
Johannes Leweux ◽  
Jennifer Blackburne
Keyword(s):  
Vibration Amplitude ◽  
Jet Injection ◽  
Blade Vibration ◽  
Vibration Displacement ◽  
Safe Level ◽  
Air Jet ◽  
Turbine Housing ◽  
Generalized Force ◽  
Blade Failure ◽  
Positive Results

Abstract Radial turbines consisting of a spiral volute inlet casing, such as those found in turbochargers, are subject to excitations caused by the inlet flow. In the absence of inlet guide vanes, the asymmetries from the volute are accentuated and lead to Low Engine Order (LEO) excitations. These excitations can be particularly troublesome as they are likely to resonate with the first bending mode (M1) at high rotational speeds, causing large vibration displacement amplitudes which will result in High Cycle Fatigue (HCF). It is therefore imperative to ensure these vibration amplitudes are low enough to make certain blade failure will not occur. This paper deals with the possibility of actively influencing the excitation pressure pattern on the blades such that the amplitude and phase of the forcing is affected. This active influence is through the use of an air jet injection at the tip of the turbine blade and has the potential to substantially reduce the blade vibrations caused by the LEO excitations. This theory of using air jets to alter the blade vibration amplitude is investigated in this paper both experimentally, using standard turbine housing equipped with a rotatable device with a single jet nozzle, and numerically, using Computation Fluid Dynamics (CFD) software ANSYS CFX. The tests yielded positive results indicating that a single air injection was able to significantly decrease, as well as increase, the blade vibration amplitude. At certain jet injection locations, decreases in blade vibration amplitude of 70% were measured which was backed up by numerical results. To numerically calculate these differences in the vibration amplitude, the generalized force approach was used successfully. The positive results obtained from this study show real potential for this method to become a useful tool in keeping blade vibration to a safe level and avoiding failures in turbomachines.

Aerodynamic Excitation Analysis of Radial Turbine Blades due to Unsteady Flow From Vaneless Turbine Housings

2017 ◽  
Author(s):  
Stephan Netzhammer ◽  
Damian M. Vogt ◽  
Stephan Kraetschmer ◽  
Johannes Leweux ◽  
Andreas Koengeter
Keyword(s):  
Test Data ◽  
Turbine Blades ◽  
Resonant Excitation ◽  
Design Parameters ◽  
Blade Vibration ◽  
Baseline Design ◽  
Housing Design ◽  
Radial Turbine ◽  
Turbine Housing ◽  
Generalized Force

Turbocharger turbine blades are subjected to resonant excitation that can lead to High Cycle Fatigue (HCF). In vaneless turbines the excitation primarily stems from asymmetries in the turbine housing such as the volute and the tongue. Given the nature of such asymmetries, the excitation is of a Low Engine Order (LEO) type. The present study deals with the effect of radial turbine housing design on LEO resonant excitation of turbine blades. The study focuses on two geometrical key design parameters of a twin-scroll turbine housing for a radial turbine which is the rotor-tongue distance and the circumferential angle between both tongues. The generalized force approach is used to identify the critical blade surface regions in order to understand the excitation mechanism of each specific design and to assess the differences of design variants with respect to the baseline design. The presented approach is highly practicable, because it is less expensive than full FSI-simulations. This approach is validated on tip timing test data from full-scale experiments. Correlation to test data shows that the presented approach is capable of capturing the relative trends reliably and hence can efficiently be employed in an industrial design process such as to minimize blade vibration amplitudes. It is shown that a reduction of blade vibration amplitudes by a factor of 10 could be achieved.

Experimental Study of Blade Vibration in Centrifugal Compressors

2011 ◽  
Author(s):  
Andrew H. Lerche ◽  
J. Jeffrey Moore ◽  
Timothy C. Allison
Keyword(s):  
High Cycle Fatigue ◽  
Axial Flow ◽  
Modal Testing ◽  
Mode Shapes ◽  
Cyclic Symmetry ◽  
Centrifugal Compressors ◽  
Compressor Blades ◽  
Blade Vibration ◽  
Phase Cancellation ◽  
Blade Failure

Blade vibration in turbomachinery is a common problem that can lead to blade failure by high cycle fatigue. Although much research has been performed on axial flow turbomachinery, little has been published for radial flow machines such as centrifugal compressors and radial inflow turbines. This work develops a test rig that measures the resonant vibration of centrifugal compressor blades. The blade vibrations are caused by the wakes coming from the inlet guide vanes. These vibrations are measured using blade mounted strain gauges during a rotating test. The total damping of the blade response from the rotating test is compared to the damping from the modal testing performed on the impeller. The mode shapes of the response and possible effects of mistuning are also discussed. The results show that mistuning can affect the phase cancellation which one would expect to see on a system with perfect cyclic symmetry.

New Step to Improve the Accuracy of Blade Synchronous Vibration Parameters Identification Based on Combination of GARIV and LM Algorithm

2017 ◽  
Author(s):  
Weimin Wang ◽  
Sanqun Ren ◽  
Shan Huang ◽  
Qihang Li ◽  
Kang Chen
Keyword(s):  
Experimental Study ◽  
Parameters Identification ◽  
Least Square ◽  
Experimental Result ◽  
Blade Vibration ◽  
Vibration Displacement ◽  
Campbell Diagram ◽  
Identification Method ◽  
Blade Tip ◽  
Vibration Parameters

Generally, turbine blade vibration can be divided into asynchronous vibration and synchronous vibration. Comparing to parameters identification of asynchronous vibration, that of the synchronous vibration is more difficult and needs more sensors. The applicability of the synchronous identification method is more stringent than that of asynchronous identification method. A new method is presented to identify the blade synchronous vibration parameters based on the blade tip-timing (BTT) method and previous achievements in this region. Here, the parameters, such as the frequency of harmonic resonance center, blade vibration amplitude and the initial phase, are obtained by the nonlinear least square fitting algorithm based on relationships between the rotation speed and the blade tip displacement. We call this way as sweep frequency fitting (SFF) method. As the blade is operated at a constant speed that is near the frequency of resonance center, the blade vibration displacement can be obtained by the sensors at different positions, so the blade synchronous vibration Engine Order (EO) can be obtained by the global autoregressive with instrumental variables (GARIV) method. Furthermore the Campbell diagram of blade synchronous vibration can be plotted by the parameters obtained by GARIV method and SFF method. In the experimental study, the parameter identification of blade synchronous vibration is completed and the Campbell diagram of blade vibration is accurately plotted under the excitation of six magnets. Meanwhile, the experimental study and analysis on the harmonic vibration of blade with different numbers of excitation are carried out. The relative deviation of the dynamic frequency of blade between the experimental result and simulation result is less than 1%.

scholarly journals The methodology for measuring the vibration amplitude of the blade of the aircraft engine compressor in the fatigue test

Mechanik ◽  
2018 ◽  
Vol 91 (3) ◽  
pp. 230-232
Author(s):  
Leszek Bielenda ◽  
Wojciech Obrocki ◽  
Maciej Masłyk ◽  
Jan Sieniawski
Keyword(s):  
Fatigue Test ◽  
Eddy Current ◽  
Vibration Amplitude ◽  
Aircraft Engine ◽  
Fatigue Tests ◽  
Compressor Blade ◽  
Additional Test ◽  
Blade Vibration ◽  
Comparison Research ◽  
Engine Compressor

Results of comparison research of various sensors types used in the fatigue tests for aircraft engine compressor blade vibration amplitude measurement were analysed. Sensors under tests: inductive, capacitive, eddy-current, laser and vibration. Presented were sensors characteristics and their faults. Additional test stand instrumentation was designed and performed, including mounting bracket.

scholarly journals Mistuning Effects on the Nonlinear Friction Saturation of Flutter Vibration Amplitude

2020 ◽  
Author(s):  
Carlos Martel ◽  
Salvador Rodríguez
Keyword(s):  
Vibration Amplitude ◽  
Gas Flow ◽  
Travelling Waves ◽  
Computational Cost ◽  
Travelling Wave ◽  
Nonlinear Friction ◽  
Blade Vibration ◽  
Bladed Disk ◽  
Spring System ◽  
Mass Spring

Abstract The blade vibration level of an aerodynamically unstable rotor is a quantity of crucial importance to correctly estimate the blade fatigue life. This amplitude is the result of the balance between the energy pumped into the blades by the gas flow, and the nonlinear dissipation at the blade-disk contact interfaces. In a tuned configuration, the blade displacements can be described as a travelling wave consisting of one fundamental nodal diameter and frequency and its higher harmonics, and the problem can be reduced to the computation of a time periodic solution in just one sector. This simplification is no longer valid for a mistuned bladed disk. The resulting nonlinear vibration of the mistuned system is a combination of several travelling waves with different number of nodal diameters, coupled through mistuning. In this case, the complete bladed disk has to be considered, which requires an extremely high computational cost, and, for this reason, reduced order models (ROM) are required to analyze this situation. In this work, we use a 3 DOF/sector mass-spring system to describe the nonlinear friction saturation of the flutter vibration amplitude of a realistic mistuned bladed disk. The convergence of the solution of the mass-spring system is still quite slow because of the presence of many unstable modes with very similar growth rates. In order to speed-up the simulations a simpler asymptotic ROM is derived from the mass-spring model, which allows for much faster integration times. The simulations of the asymptotic ROM are compared with the measurements obtained in the European project FUTURE, where an aerodynamically unstable LPT rotor was tested with different intentional mistuning patterns.

scholarly journals Pressure Pulsation Signal Analysis for Centrifugal Compressor Blade Crack Determination

2014 ◽  
Vol 2014 ◽  
pp. 1-15 ◽  
Author(s):  
Hongkun Li ◽  
Xuefeng Zhang ◽  
Xiaowen Zhang ◽  
Shuhua Yang ◽  
Fujian Xu
Keyword(s):  
Centrifugal Compressor ◽  
Early Warning ◽  
Signal Analysis ◽  
Pressure Pulsation ◽  
Process Analysis ◽  
Dynamic Strain ◽  
Blade Vibration ◽  
Mode Decomposition ◽  
Blade Failure ◽  
Blade Crack

Blade is a key piece of component for centrifugal compressor. But blade crack could usually occur as blade suffers from the effect of centrifugal forces, gas pressure, friction force, and so on. It could lead to blade failure and centrifugal compressor closing down. Therefore, it is important for blade crack early warning. It is difficult to determine blade crack as the information is weak. In this research, a pressure pulsation (PP) sensor installed in vicinity to the crack area is used to determine blade crack according to blade vibration transfer process analysis. As it cannot show the blade crack information clearly, signal analysis and empirical mode decomposition (EMD) are investigated for feature extraction and early warning. Firstly, signal filter is carried on PP signal around blade passing frequency (BPF) based on working process analysis. Then, envelope analysis is carried on to filter the BPF. In the end, EMD is carried on to determine the characteristic frequency (CF) for blade crack. Dynamic strain sensor is installed on the blade to determine the crack CF. Simulation and experimental investigation are carried on to verify the effectiveness of this method. The results show that this method can be helpful for blade crack classification for centrifugal compressors.

Frequency Distribution of Blades in Turboengines and Vibration Characteristics of Mistuned Blades

1985 ◽  
Author(s):  
Ming-Fu Liao ◽  
Da-Kuan Shen
Keyword(s):  
Probability Distribution ◽  
Frequency Distribution ◽  
Gaussian Distribution ◽  
Vibration Amplitude ◽  
Vibration Characteristics ◽  
Frequency Difference ◽  
Blade Vibration ◽  
One Stage

In this paper, the probability distribution of blade frequencies is given as a Gaussian distribution approximately. The computations for comparing and simulating the effects of blade mistune on blade-disk vibration are made, which show that in general cases, blade mistune will cause the blade vibration amplitude to increase 20–30%. If the frequency difference of the blades on one stage is within ± 2%, the effect of mistune on the blade vibration will not be obvious. It is suggested that the blades can be divided into groups for mounting them and the frequency difference in each group not exceeds a certain range, for example, ± 2%.

Prediction of transient vibration response of dual-rotor-blade-casing system with blade off

2019 ◽  
Vol 233 (14) ◽  
pp. 5164-5176 ◽  
Author(s):  
Nanfei Wang ◽  
Chao Liu ◽  
Dongxiang Jiang
Keyword(s):  
Transient Response ◽  
Rotor Blade ◽  
Vibration Amplitude ◽  
Impact Load ◽  
Transient Vibration ◽  
Vibration Displacement ◽  
Highly Nonlinear ◽  
Aero Engine ◽  
Fan Blade ◽  
The Impact

Fan blade off occurring in a running rotor of the turbofan engine dual-rotor system will cause a sudden unbalance and inertia asymmetry, which results in large impact load and consequently induces the rubbing between blade and casing. In order to reveal the transient dynamic response characteristics of actual aero-engine when fan blade off event occurs, the dynamic model of dual-rotor-blade-casing system is developed, in which the distribution characteristics of the stiffness and mass, the load transfer, and the coupling effects of dual-rotor and casing are included. Considering several excitations caused by blade off, the physical process and mechanical characteristics of the fan blade off event are described qualitatively. Considering that only the casing acceleration signal can be used for condition monitoring in actual aero-engine, the transient response including rotor vibration displacement and casing vibration acceleration during the instantaneous status are obtained. Due to the time-varying and highly nonlinear characteristics of vibration responses, frequency slice wavelet transform is employed to isolate the vibration signal features. The results show that the impact load induced by the sudden imbalance causes significant increase of vibration amplitude. The rubbing action between blade and rotor will impose constraint effects on the rotor, which decreases the transient vibration amplitude. The inertia asymmetry has a big impact on the transient response. The vibration characteristics of casing acceleration under blade off are similar to those of rotor displacement, while casing acceleration response attenuates to stable value faster and is more sensitive to high-frequency components of vibration.

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