Optical Determination of Rotating Fan Blade Deflections

1977 ◽  
Vol 99 (2) ◽  
pp. 204-209 ◽  
Author(s):  
H. Stargardter
Keyword(s):  
Mode Shape ◽  
Shape Description ◽  
Compressor Blades ◽  
Blade Vibration ◽  
Reflected Light ◽  
Flutter Analysis ◽  
Optical Determination ◽  
Fan Blade ◽  
A New Technique

Measurement of flutter motion for rotating fan and compressor blades is necessary to verify mode shape analysis and assure an accurate description of the deflection and twist distribution required for stability prediction. The static deflection of blades caused by centrifugal and gas loads also needs to be measured to improve the accuracy of performance analysis. This paper presents a new technique for making these measurements with small blade-mounted mirrors that reflect laser light once per revolution. For steady operation, in the absence of blade vibration, each mirror reflects a light beam to project a repeating spot on a display screen, once for every revolution of the rotor. However, when the blades are fluttering the reflected light moves from its stationary position and during successive revolutions describes the blade motion as a lissajous pattern. Vibration amplitude, phase, and frequency are discussed and related to analysis. Limits in accuracy and the importance of precise mode shape description for flutter analysis are presented.

Excited Blade Vibration for Aeroelastic Investigations of a Rotating Blisk Using Piezo-Electric Macro Fiber Composites

2013 ◽  
Author(s):  
Joachim Belz ◽  
Markus May ◽  
Jan Siemann ◽  
Joerg R. Seume ◽  
Christian Voigt ◽  
...  
Keyword(s):  
High Voltage ◽  
Mode Shape ◽  
Liquid Metals ◽  
Fiber Composites ◽  
Operating Conditions ◽  
Test Facility ◽  
Experimental Investigations ◽  
Compressor Blades ◽  
Blade Vibration ◽  
Fan Blade

Experimental investigations of the aerodynamic damping of compressor blades are usually performed by forcing the blades externally to a motion that is similar to a given mode shape and inter-blade phase angle (IBPA) while measuring the motion-induced unsteady pressure distribution. Evaluating this to an aerodynamic work entry from the fluid to the blade, at least a local contribution to the flutter (in-)stability can be determined. Test rigs are usually non-rotating linear or rotating annular cascade wind tunnels. In the latter case, besides measuring in and transmitting data out of the rotating system, the excitation of the blades themselves is still a challenge. In the present case a blisk rotor with realistic fan blade geometries and flow conditions was investigated aeroelastically. For the excitation of the 1st bending (1F) mode shape of the blading a sector of five blades was chosen. In this sector the natural vibration of the blading, represented by constant vibration amplitudes and a given IBPA should be simulated. Therefore the blades were equipped with Macro Fiber Composites (MFC). These foils of piezoelectric material expand and contract due to the applied high voltage. A control system was developed to adjust the amplitude and the IBPA of the blade vibration. For the transmission of the high voltage, a separate data transmission system on the base of liquid metals was chosen. The blade vibration was measured by strain gauges and additionally monitored by a specific rig system. The aeroelastic investigations were carried out in the compressor test facility M2VP of the DLR Institute of Propulsion Technology in Cologne. During the measurement, the MFCs were able to excite the blades to a certain extent. The paper will present the technique to excite the blades of a compressor blisk by means of MFCs as well as achieved vibration amplitudes and limitations under engine-like operating conditions.

Influence of Intake on Fan Blade Flutter

2015 ◽  
Vol 137 (8) ◽  
Author(s):  
Mehdi Vahdati ◽  
Nigel Smith ◽  
Fanzhou Zhao
Keyword(s):  
Correct Prediction ◽  
Blade Vibration ◽  
Reflected Waves ◽  
Reflection Model ◽  
Flutter Analysis ◽  
Flutter Boundary ◽  
Blade Flutter ◽  
Computational Fluid Dynamics Cfd ◽  
Fan Blade ◽  
Insight Into

The main aim of this paper is to study the influence of upstream reflections on flutter of a fan blade. To achieve this goal, flutter analysis of a complete fan assembly with an intake duct and the downstream outlet guide vanes (OGVs) (whole low pressure (LP) domain) is undertaken using a validated computational fluid dynamics (CFD) model. The computed results show good correlation with measured data. Due to space constraints, only upstream (intake) reflections are analyzed in this paper. It will be shown that the correct prediction of flutter boundary for a fan blade requires modeling of the intake and different intakes would produce different flutter boundaries for the same fan blade. However, the “blade only” and intake damping are independent and the total damping can be obtained from the sum of the two contributions. In order to gain further insight into the physics of the problem, the pressure waves created by blade vibration are split into an upstream and a downstream traveling wave in the intake. The splitting of the pressure wave allows one to establish a relationship between the phase and amplitude of the reflected waves and flutter stability of the blade. By using this approach, a simple reflection model can be used to model the intake effects.

Influence of Intake on Fan Blade Flutter

2014 ◽  
Author(s):  
Mehdi Vahdati ◽  
Nigel Smith ◽  
Fanzhou Zhao
Keyword(s):  
Correct Prediction ◽  
Pressure Waves ◽  
Blade Vibration ◽  
Reflected Waves ◽  
Reflection Model ◽  
Flutter Analysis ◽  
Flutter Boundary ◽  
Blade Flutter ◽  
Fan Blade ◽  
Insight Into

The main aim of this paper is to study the influence of upstream reflections on flutter of a fan blade. To achieve this goal, flutter analysis of a complete fan assembly with an intake duct and the downstream OGVs (whole LP domain) is undertaken using a validated CFD model. The computed results show good correlation with measured data. Due to space constraints, only upstream (intake) reflections are analyzed in this paper. It will be shown that the correct prediction of flutter boundary for a fan blade requires modeling of the intake and different intakes would produce different flutter boundaries for the same fan blade. However, the ‘blade only’ and intake damping are independent and the total damping can be obtained from the sum of the two contributions. In order to gain further insight into the physics of the problem, the pressure waves created by blade vibration are split into an upstream and a downstream traveling wave in the intake. The splitting of the pressure wave allows one to establish a relationship between the phase and amplitude of the reflected waves and flutter stability of the blade. By using this approach, a simple reflection model can be used to model the intake effects.

A Technique for the Laboratory Determination of Recirculation in Single Needle Dialysis

1993 ◽  
Vol 16 (2) ◽  
pp. 63-70 ◽  
Author(s):  
N.A. Hoenich ◽  
P.T. Smirthwaite ◽  
C. Woffindin ◽  
P. Lancaster ◽  
T.H. Frost ◽  
...  
Keyword(s):  
Experimental Data ◽  
Flow Rate ◽  
Experimental Results ◽  
New Technique ◽  
Treatment Efficiency ◽  
Single Lumen ◽  
Theoretical Predictions ◽  
Lumen Catheter ◽  
A New Technique

Recirculation is an important factor in single needle dialysis and, if high, can compromise treatment efficiency. To provide information regarding recirculation characteristics of access devices used in single needle dialysis, we have developed a new technique to characterise recirculation and have used this to measure the recirculation of a Terumo 15G fistula needle and a VasCath SC2300 single lumen catheter. The experimentally obtained results agreed well with those established clinically (8.5 ± 2.4% and 18.4 ± 3.4%). The experimental results have also demonstrated a dependence on access type, pump speeds and fistula flow rate. A comparison of experimental data with theoretical predictions showed that the latter exceeded those measured with the largest contribution being due to the experimental fistula.

Sign in / Sign up

Export Citation Format

Share Document