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

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

Rig Testing of the Operability of a Transonic Compressor Blade of an Industrial Gas Turbine

2019 ◽  
Author(s):  
Hyunsu Kang ◽  
Sungjong Ahn ◽  
Kyusic Hwang ◽  
Justin Bock ◽  
Jeongseek Kang ◽  
...  
Keyword(s):  
Gas Turbine ◽  
Gas Turbines ◽  
Large Scale ◽  
Load Condition ◽  
Compressor Blade ◽  
Guide Vanes ◽  
Aerodynamic Damping ◽  
Transonic Compressor ◽  
Full Speed ◽  
Industrial Gas Turbine

Abstract This paper describes the flow and vibrations measured in a 1.5-stage transonic research compressor tested at the Notre Dame Turbomachinery Laboratory. The compressor is a sub-scale version of a large-scale industrial gas turbine. The experiment measured the compressor performance and investigated the operability issues of stall and flow-induced blade vibrations due to buffet and flutter. The buffet was investigated at full-speed with fully-closed inlet guide vanes; the full-speed, no-load condition of gas turbines used for power generation. The flutter was investigated at part-speed conditions with partially closed guide vanes; the part-power condition where stall flutter typically occurs for aero-engines. At both of these conditions the blades operate with high incidence and moderate velocity, which can result in flow-induced vibrations. Aero-elastic simulations were performed to predict the flutter boundary. The flutter analysis predicted positive aerodynamic damping near the operating line, and a decrease in aerodynamic damping as the stall boundary was approached. No flutter was observed in the stable operating range of the compressor. The experimental campaign used blade tip timing to measure the vibrations and unsteady pressure transducers above the compressor blade. These two types of data were correlated to better understand the drivers of vibration. The paper describes the behavior of the aerodynamic drivers of buffet and flutter and the resulting vibration.

scholarly journals Mounting Troubles

2011 ◽  
Vol 133 (03) ◽  
pp. 46-49
Author(s):  
Lee S. Langston
Keyword(s):  
Fuel Consumption ◽  
Compressor Blade ◽  
Tip Clearance ◽  
Jet Engines ◽  
Successful Resolution ◽  
Blade Tip ◽  
Leading Edges ◽  
The 1960S ◽  
Blade Tip Clearance

This article analyzes the problems encountered in developing the first jumbo jet, the Boeing 747. In the 1960s, the jumbo jet—a wide-body aircraft with two aisles and up to 10 seats per row—was the logical next step in the progression of the airliner. For the Pratt & Whitney JT9D, which was causing the 747 trouble, the engine skin casing was both bending and ovalizing—exhibiting non-circular distortion—under thrust loading that could be as high as 43,500 pounds on takeoff. The ovalizing distortion resulted in turbine and compressor blade rubbing against the interior of the engine case and necessitated power-robbing increases in blade tip clearance gaps. The result was a serious reduction in thrust, and increased fuel consumption as much as 7 percent above guaranteed rates. Boeing chose to mount the JT9D engines well forward of the 747 wing leading edges. The successful resolution of ovalization problems encountered in mounting the JT9D to the first Boeing 747s has provided guidance for future installations of large fan commercial jet engines.

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.

Jet Engine Compressor Blade Refurbishment by Application of the Advanced Re-Contouring Process

2003 ◽  
Author(s):  
Herwart T. Hoenen ◽  
Karsten Ellenberger
Keyword(s):  
High Pressure ◽  
Flow Behavior ◽  
Leading Edge ◽  
Compressor Blade ◽  
Tip Clearance ◽  
Jet Propulsion ◽  
High Pressure Compressor ◽  
Leading Edges ◽  
Pressure Compressor ◽  
Edge Contours

In modern jet propulsion Systems the core engine has an essential influence on the total engine performance. Especially the high pressure compressor plays an important role in this scheme. Substantial factors here are losses due to tip clearance effects and aerodynamic airfoil quality. During flight Operation the airfoils are subject to wear and tear on the leading edge. These effects cause a shortening of the chord length and the leading edge profiles become deformed. This results in a deterioration of the engine efficiency performance level and a reduced stall margin. The paper deals with the re-contouring of the leading edges of compressor airfoils. Lufthansa Technik AG in cooperation with the Institute of Jet Propulsion and Turbomachinery (RWTH Aachen University) developed a new method for the profile definition for the blade refurbishment. The common procedure of smoothing out the leading edges manually on a wheel grinding machine can not provide a defined contour nor a reproducible result of the overhaul process. In order to achieve optimized flow conditions in the compressor blade rows, suitable leading edge contours have to be defined for the worn airfoils. In an iterative process the flow behavior of these redesigned profiles is checked by numerical flow simulations and the shape of the profiles is improved. The following machining of the new defined leading edge contours is achieved on a grinding station handled by an appropriately programmed robot. Within this Advanced Re-contouring Process (ARP) the worn blades are precision-measured and then provided with an aerodynamically optimized leading edge profile numerically newly developed under computer control. The application of this process enhances the performance and lowers the fuel consumption while prolonging the blades’ service life by 25%. The performance achievable with ARP has been confirmed both through a long term analysis and by a back-to-back comparison test on the engine test stand. For this purpose the stages 3 through 14 of a CF6-50 high pressure compressor were on the one hand fitted with conventionally overhauled blades and on the other with ARP-optimized blades of the same basic geometry. By installing the optimized blades the EGT margin could be increased by 3° to 4° C. This results in an prolongation of the on-wing time by more than 1000 hours.

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.

Application of Aeroelastic Methods in Compressor Cascade Configurations Using Commercial Code Coupling

2008 ◽  
Author(s):  
Sven Schrape ◽  
Jens Nipkau ◽  
Arnold Ku¨hhorn ◽  
Bernd Beirow
Keyword(s):  
Compressor Blade ◽  
Two Dimensional ◽  
Compressor Cascade ◽  
Aerodynamic Damping ◽  
High Pressure Compressor ◽  
Commercial Code ◽  
Bending Mode ◽  
Blade Vibrations ◽  
Coupling Approach ◽  
Pressure Compressor

This paper presents the results of fluid structure coupled simulations of compressor blade vibrations of two compressor cascade configurations in order to determine aeroelastic parameters such as aerodynamic damping and the corresponding frequency shift. Therefore a partitioned code coupling approach was employed in order to couple the FE-code ABAQUS with the CFD-code FLUENT via MpCCI (Mesh based Code Coupling Interface) developed by Fraunhofer SCAI. The code coupling is used to compute the unsteady, two-dimensional, inviscid and viscid flow around a NACA 3506 airfoil for blade vibrations in a torsional modeshape. This first example is used to validate the results against results from literature. Further on the unsteady, two-dimensional, viscid flow around a research high-pressure compressor airfoil is computed for a bending mode. The results of those computations are implemented into a simplified, structural blisk model approximating the air flow influence by a mechanical model.

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
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