scholarly journals Tip Clearance Influence on Aerodynamic Damping Maps

2017 ◽  
Author(s):  
Mateus Augusto Malta Teixeira ◽  
Robert E. Kielb
Keyword(s):  
Tip Clearance ◽  
Aerodynamic Damping

Effects of Tip Clearance on Aerodynamic Damping in a Linear Turbine Cascade

2008 ◽  
Vol 24 (1) ◽  
pp. 26-33 ◽  
Author(s):  
Xiuquan Huang ◽  
Li He ◽  
David L. Bell
Keyword(s):  
Tip Clearance ◽  
Turbine Cascade ◽  
Aerodynamic Damping

Influence of the Tip Clearance on a Compressor Blade Aerodynamic Damping

2017 ◽  
Vol 33 (1) ◽  
pp. 227-233 ◽  
Author(s):  
Fanny M. Besem ◽  
Robert E. Kielb
Keyword(s):  
Compressor Blade ◽  
Tip Clearance ◽  
Aerodynamic Damping

Effect of Tip Clearance on the Aeroelastic Stability of a Wide-Chord Fan Rotor

2020 ◽  
Vol 142 (9) ◽  
Author(s):  
Xu Dong ◽  
Yingjie Zhang ◽  
Ziqing Zhang ◽  
Xingen Lu ◽  
Yanfeng Zhang
Keyword(s):  
High Speed ◽  
Pressure Ratio ◽  
Tip Clearance ◽  
Influence Coefficient ◽  
Pressure Amplitude ◽  
Aeroelastic Stability ◽  
Local Flow ◽  
Blade Loading ◽  
Unsteady Pressure ◽  
Aerodynamic Damping

Abstract This research presents a series of simulations that investigate the effects of tip clearance on the aeroelastic stability of a wide-chord high-speed transonic fan rotor. The results show that the stall margin and the total pressure ratio decreases as the tip clearance increases. The effect of tip clearance on the blade loading can extend to 30% span. The phase of the influence coefficient without tip clearance is different from that with clearance, which causes the most unstable aerodynamic damping to shift in the nodal diameter. As the clearance increases from 0.25 mm to 2 mm, the damping decreases. The nonmonotonic behavior found by other researchers was not observed in this study. We conclude that the tip clearance affects the aeroelastic stability in two ways. The first is to change the blade loading so that the amplitude of the unsteady pressure increases or decreases, while the phase hardly changes, resulting in changes in aerodynamic damping. The second is to change the local flow so that the unsteady pressure amplitude and the phase change locally.

Analysis Method of NSV and Influence of Tip Clearance Flow Instabilities on NSV in an Axial Transonic Compressor Rotor

2021 ◽  
pp. 1-80
Author(s):  
Le Han ◽  
Dasheng Wei ◽  
Yanrong Wang ◽  
Xianghua Jiang ◽  
Xiaojie Zhang
Keyword(s):  
Maximum Amplitude ◽  
Tip Clearance ◽  
Modal Shape ◽  
Blade Vibration ◽  
Tip Clearance Flow ◽  
Unsteady Pressure ◽  
Aerodynamic Damping ◽  
Transonic Compressor ◽  
Clearance Flow ◽  
Negative Damping

Abstract The relationship between tip clearance flow (TCF) and blade vibration in locked-in region is numerically investigated on a transonic rotor. The numerical method is verified by citing references. The phase of TCF changes with the operating condition. A separation method of the unsteady pressure caused by TCF and blade vibration is developed. The unsteady pressure during NSV is separated into the TCF and vibration components under 1B and 8th modes. The unsteady pressure of TCF is similar with that of rigid blade. The unsteady pressure of blade vibration is larger at part span, and its distribution depends on the modal shape and vibrating amplitude. The unsteady pressure of TCF and blade vibration determine the aerodynamic damping in locked-in region. The aerodynamic damping of TCF changes with the TCF phase. TCF provides positive damping at some phases and negative damping at other phases. The aerodynamic work of TCF and blade vibration increases linearly and at the rate of square with the vibrating amplitude, respectively. TCF is dominant in the initial stage of vibration. With the vibrating amplitude increasing, the aerodynamic work of vibration catches up gradually. NSV occurs when TCF provides negative damping and the unsteady pressure of vibration provides positive damping. If the work of vibration is negative, vibration will be enlarged until failure. The maximum amplitude of NSV canbe obtained by calculating the balance of work. For the 8th mode, the limit amplitude under 0ND is 0.0926%C corresponding to vibration stress of 60MPa.

scholarly journals Influence of the Tip Clearance on the Aeroelastic Characteristics of a Last Stage Steam Turbine

2019 ◽  
Vol 9 (6) ◽  
pp. 1213
Author(s):  
Tianrui Sun ◽  
Anping Hou ◽  
Mingming Zhang ◽  
Paul Petrie-Repar
Keyword(s):  
Steam Turbine ◽  
Tip Clearance ◽  
Test Case ◽  
Steam Turbines ◽  
Aeroelastic Stability ◽  
Tip Leakage Vortex ◽  
Tip Leakage ◽  
Aerodynamic Damping ◽  
Last Stage ◽  
Gap Height

In this paper, the tip clearance effects on the aeroelastic stability of a last-stage steam turbine model are investigated. Most of the unsteady aerodynamic work contributing to flutter of the long blades of the last-stage of a steam turbine is done near the tip of the blade. The flow in this region is transonic and sensitive to geometric parameters such as the tip clearance height. The KTH Steam Turbine Flutter Test Case was chosen as the test case, which is an open geometry with similar parameters to modern free-standing last-stage steam turbines. The energy method based on 3D URANS simulation was applied to investigate the flutter characteristics of the rotor blade with five tip gap height varying from 0–5% of the chord length. The numerical results show that the global aerodynamic damping for the least stable inter-blade phase angle (IBPA) increases with the tip gap height. Three physical mechanisms are found to cause this phenomenon. The primary cause of the variation in total aerodynamic damping is the interaction between tip clearance vortex and the trailing edge shock from the adjacent blade. Another mechanism is the acceleration of the flow near the aft side of the suction surface in the tip region due to the well-developed tip leakage vortex when the tip clearance height is greater than 2.5% of chord. This causes a stabilizing effect at the least stable IBPA. The third mechanism is the oscillation of the tip leakage vortex due to the blade vibration. This has a negative influence on the aeroelastic stability.

Aeroelastic Stability of Axial Compressor Blades Under Different Operating Conditions

2020 ◽  
Author(s):  
Mingchang Fang ◽  
Yanrong Wang
Keyword(s):  
Axial Compressor ◽  
Operating Conditions ◽  
Tip Clearance ◽  
Aeroelastic Stability ◽  
Compressor Blades ◽  
Aerodynamic Damping ◽  
Reduced Frequency ◽  
Modal Component ◽  
Stall Flutter ◽  
Operating Points

Abstract Flutter is one of the important issues in turbomachinery analysis. There are four common types of flutter, including sub/transonic stall flutter, choke flutter, supersonic stall flutter, and supersonic non-stall flutter. Flutter may occur under many different operating conditions. Therefore, it is important to study the aeroelastic stability of blades when the compressor operates under different conditions. Based on the energy method proposed by Carta [1], this paper studied the aeroelastic stability of the second-stage rotor blade of an axial compressor under different operating conditions. It is found that the aerodynamic damping of the blade under the near-stall operating point of the compressor is negative. Three typical operating points are selected to study the differences in flutter mechanism between different operating conditions. The 90% span section is selected as the reference section to analyze the variation of the aerodynamic work at different operating points. The influence of reduced frequency, modal component, and tip clearance on aerodynamic damping are analyzed under three operating points.

Self-Excited Blade Vibration Experimentally Investigated in Transonic Compressors: Rotating Instabilities and Flutter

2016 ◽  
Vol 138 (4) ◽  
Author(s):  
F. Holzinger ◽  
F. Wartzek ◽  
M. Jüngst ◽  
H.-P. Schiffer ◽  
S. Leichtfuss
Keyword(s):  
Stability Limit ◽  
Tip Clearance ◽  
Blade Vibration ◽  
Casing Treatment ◽  
Operating Range ◽  
Aerodynamic Damping ◽  
Torsion Mode ◽  
Experimental Campaign ◽  
Excited Vibration ◽  
Design Speed

This paper investigates the vibrations that occurred on the blisk rotor of a 1.5-stage transonic research compressor designed for aerodynamic performance validation and tested in various configurations at Technische Universität Darmstadt. During the experimental test campaign, self-excited blade vibrations were found near the aerodynamic stability limit of the compressor. The vibration was identified as flutter of the first torsion mode and occurred at design speed as well as in the part-speed region. Numerical investigations of the flutter event at design speed confirmed negative aerodynamic damping for the first torsion mode, but showed a strong dependency of aerodynamic damping on blade tip clearance (BTC). In order to experimentally validate the relation between BTC and aerodynamic damping, the compressor tests were repeated with enlarged BTC for which stability of the torsion mode was predicted. During this second experimental campaign, strong vibrations of a different mode limited compressor operation. An investigation of this second type of vibration found rotating instabilities to be the source of the vibration. The rotating instabilities first occur as an aerodynamic phenomenon and then develop into self-excited vibration of critical amplitude. In a third experimental campaign, the same compressor was tested with reference BTC and a nonaxisymmetric casing treatment (NASCT). Performance evaluation of this configuration repeatedly showed a significant gain in operating range and pressure ratio. The gain in operating range means that the casing treatment successfully suppresses the previously encountered flutter onset. The aeroelastic potential of the NASCT is validated by means of the unsteady compressor data. By giving a description of all of the above configurations and the corresponding vibratory behavior, this paper contains a comprehensive summary of the different types of blade vibration encountered with a single transonic compressor rotor. By investigating the mechanisms behind the vibrations, this paper contributes to the understanding of flow-induced blade vibration. It also gives evidence to the dominant role of the tip clearance vortex in the fluid–structure-interaction of tip critical transonic compressors. The aeroelastic evaluation of the NASCT is beneficial for the design of next generation casing treatments for vibration control.

Self-Excited Blade Vibration Experimentally Investigated in Transonic Compressors: Rotating Instabilities and Flutter

2015 ◽  
Author(s):  
F. Holzinger ◽  
F. Wartzek ◽  
M. Jüngst ◽  
H.-P. Schiffer ◽  
S. Leichtfuß
Keyword(s):  
Tip Clearance ◽  
Blade Vibration ◽  
Casing Treatment ◽  
Operating Range ◽  
Aerodynamic Damping ◽  
Torsion Mode ◽  
Experimental Campaign ◽  
Blade Tip ◽  
Design Speed ◽  
Blade Tip Clearance

This paper investigates the vibrations that occurred on the blisk rotor of a 1.5-stage transonic research compressor designed for aerodynamic performance validation and tested in various configurations at Technische Universität Darmstadt. During the experimental test campaign self-excited blade vibrations were found near the aerodynamic stability limit of the compressor. The vibration was identified as flutter of the first torsion mode and occurred at design speed as well as in the part-speed region. Numerical investigations of the flutter event at design speed confirmed negative aerodynamic damping for the first torsion mode, but showed a strong dependency of aerodynamic damping on blade tip clearance. In order to experimentally validate the relation between blade tip clearance and aerodynamic damping, the compressor tests were repeated with enlarged blade tip clearance for which stability of the torsion mode was predicted. During this second experimental campaign, strong vibrations of a different mode limited compressor operation. An investigation of this second type of vibration found rotating instabilities to be the source of the vibration. The rotating instabilities first occur as an aerodynamic phenomenon and then develop into self-excited vibration of critical amplitude. In a third experimental campaign, the same compressor was tested with reference blade tip clearance and a non-axisymmetric casing treatment. Performance evaluation of this configuration repeatedly showed a significant gain in operating range and pressure ratio. The gain in operating range means that the casing treatment successfully suppresses the previously encountered flutter onset. The aeroelastic potential of the non-axisymmetric casing treatment is validated by means of the unsteady compressor data. By giving a description of all of above configurations and the corresponding vibratory behavior, this paper contains a comprehensive summary of the different types of blade vibration encountered with a single transonic compressor rotor. By investigating the mechanisms behind the vibrations, this paper contributes to the understanding of flow induced blade vibration. It also gives evidence to the dominant role of the tip clearance vortex in the fluid-structure-interaction of tip critical transonic compressors. The aeroelastic evaluation of the non-axisymmetric casing treatment is beneficial for the design of next generation casing treatments for vibration control.

Investigation of Forced Response Sensitivity of Low Pressure Compressor With Respect to Variation in Tip Clearance Size

2015 ◽  
Vol 137 (9) ◽  
Author(s):  
Majid Mesbah ◽  
Jean-François Thomas ◽  
François Thirifay ◽  
A. Naert ◽  
S. Hiernaux
Keyword(s):  
Low Pressure ◽  
Forced Response ◽  
Tip Clearance ◽  
Response Sensitivity ◽  
Aerodynamic Damping ◽  
Load Distributions ◽  
Engine Order ◽  
Different Types ◽  
Steady Load ◽  
Pressure Compressor

This study aims to numerically investigate the sensitivity of the forced response with respect to the variation of the tip clearance setting of a low pressure compressor BluM™(monoblock bladed drum) when it is subjected to low engine order excitations. Two different types of blades are employed in the upstream row in order to generate the low engine order excitations. The forced response as well as the aerodynamic damping is numerically estimated using the TWIN approach. The experiments are conducted to measure the forced response for the nominal tip gap to validate the numerical results. Further, simulations are performed for a range of tip clearances. The variation of the steady load distributions due to the changes of the tip clearance are analyzed and presented. The aerodynamic damping and the forced response are calculated and compared for different tip clearances. It is observed that aerodynamic damping increases significantly with tip gap, whereas the excitation forces are reduced. As consequence of these two evolutions, the forced response decreases drastically for larger tip clearance.

Sign in / Sign up

Export Citation Format

Share Document