• Title/Summary/Keyword: Blade loading

Search Result 160, Processing Time 0.021 seconds

Flutter Analysis of Annular Cascades in Counter Rotation

  • Nishino, R.;Namba, M.
    • Proceedings of the Korean Society of Propulsion Engineers Conference
    • /
    • 2004.03a
    • /
    • pp.813-824
    • /
    • 2004
  • The paper studies the effect of neighboring blade rows on flutter characteristics of cascading blades. For this purpose the computation program to calculate the unsteady blade loading based on the un-steady lifting surface theory for contra-rotating annular cascades was formulated and coded. Then a computation program to solve the coupled bending-torsion flutter equation for the contra-rotating annular cascades was also developed. Some results of the flutter analysis are presented. The presence of the neighboring blade row gives rise to significant change in the critical flutter condition when the main acoustic duct mode is of cut-on state.

  • PDF

A numerical study on the correlation between the evolution of propeller trailing vortex wake and skew of propellers

  • Wang, Lian-Zhou;Guo, Chun-Yu;Su, Yu-Min;Wu, Tie-Cheng
    • International Journal of Naval Architecture and Ocean Engineering
    • /
    • v.10 no.2
    • /
    • pp.212-224
    • /
    • 2018
  • The characteristics of the relationship between the evolution of propeller trailing vortex wake and skew angle are numerically examined based on four different five-blade David Taylor Model Basin (DTMB) model propellers with different skew angles. Numerical simulations are based on Reynolds-averaged Naviere-Stokes (RANS) equations combined with SST $k-{\omega}$ turbulence model. Results show that the contraction of propeller trailing vortex wake can be restrained by increasing skew angle and loading conditions, and root vortices fade away when the propeller skew angle increases. With the increase of the propeller's skew angle, the deformation of the hub vortex and destabilization of the tip vortices are weakening gradually because the blade-to-blade interaction becomes weaker. The transition trailing vortex wake from stability to instability is restrained when the skew increases. Furthermore, analyses of tip vortice trajectories show that the increasing skew can reduce the difference in trailing vortex wake contraction under different loading conditions.

Influence of failed blade-pitch-control system to FOWT by aero-elastic-control-floater-mooring coupled dynamic analysis

  • Bae, Yoon Hyeok;Kim, Moo-Hyun
    • Ocean Systems Engineering
    • /
    • v.3 no.4
    • /
    • pp.295-307
    • /
    • 2013
  • More FOWTs (floating offshore wind turbines) will be installed as relevant regulations and technological hurdles are removed in the coming years. In the present study, a numerical prediction tool has been developed for the fully coupled dynamic analysis of FOWTs in time domain including aero-loading, tower elasticity, blade-rotor dynamics and control, mooring dynamics, and platform motions so that the influence of rotor-control dynamics on the hull-mooring performance and vice versa can be assessed. The developed coupled analysis program is applied to Hywind spar design with 5 MW turbine. In case of spar-type floaters, the control strategy significantly influences the hull and mooring dynamics. If one of the control systems fails, the entire dynamic responses of FOWT can be significantly different. Therefore, it is important to maintain various control systems in a good operational condition. In this regard, the effects of failed blade pitch control system on FOWT performance including structural and dynamic responses of blades, tower, and floater are systematically investigated. Through this study, it is seen that the failure of one of the blade pitch control system can induce significant dynamic loadings on the other blades and the entire FOWT system. The developed technology and numerical tool are readily applicable to any types of floating wind farms in any combinations of irregular waves, dynamic winds, and steady currents.

Effect of Blade Leading Edge Sweep on the Performance of a High Pressure Centrifugal Compressor Impeller

  • Wang, Hongliang;Xi, Guang
    • Proceedings of the Korean Society of Propulsion Engineers Conference
    • /
    • 2008.03a
    • /
    • pp.823-827
    • /
    • 2008
  • The effects of blade leading edge sweep on both the aerodynamic performance and the structure stress of a high pressure centrifugal compressor impeller are numerically investigated. Changes in the flow structure occur as a result of the effect of leading edge sweep on the loading distribution in the tip region. The flow separation is avoided by introducing a sweep of the main blade leading edge and the strength of shock is reduced at the same time. Backswept of the leading edge is found to be beneficial to the impeller performance improving. On the other hand, the structural analysis indicated that high rotating speed of the impeller will cause substantial high bending stresses and radial deflections of the blade. Studies have shown that it is possible to control the stress distribution along the tip and root of the blade by slight adjustments to the sweep angle of the leading edge. These adjustments may be used to design the impeller with lower blade root stress distribution without aerodynamics performance penalty.

  • PDF

Design Program of Low Noise Centrifugal Fans (저소음 원심형 홴의 설계 프로그램)

  • 박준철;손정민;김기황;이승배
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
    • /
    • 2001.11a
    • /
    • pp.529-535
    • /
    • 2001
  • A centrifugal fan design code was developed and packaged together with iDesignFan/sup TM/ as new models. This code generate centrifugal forward curved and backward curved bladed impeller optimally. It also predicts the aerodynamic performance and the overall sound pressure level of the rotating fan by assuming steady blade loading. The overall sound pressure level is used as an input parameter from the third loop of the designing process to acquire the most silent fan for the given aerodynamic performance parameters. With this kind of inverse design concept used in the code, the period of designing a fan is significantly shortened. A centrifugal fan design code, developed in this study and included in iDesignFan/sup TM/, predicts the aerodynamic performance such as design flow rate and static pressure. The aerodynamic performance in the design and off-design conditions is calculated by using the mean line analysis. For the steady loading calculation, the lift force distribution in a blade is used.

  • PDF

DESCRIPTIONS OF ATTACK ANGLE AND IDEAL LIFT COEFFICIENT FOR VARIOUS AIRFOIL PROFILES IN WIND TURBINE BLADE

  • JAEGWI GO
    • Journal of the Korean Society for Industrial and Applied Mathematics
    • /
    • v.27 no.1
    • /
    • pp.75-86
    • /
    • 2023
  • The angle of attack is highly sensitive to pitch point in the airfoil shape and the decline of pitch point value induces smaller angle of attack, which implies that airfoil profile possessing closer pitch point to the airfoil tip reacts more sensitively to upcoming wind. The method of conformal transformation functions is employed for airfoil profiles and airfoil surfaces are expressed with a trigonometric series form. Attack angle and ideal lift coefficient distributions are investigated for various airfoil profiles in wind turbine blade regarding conformal transformation and pitch point. The conformed angle function representing the surface angle of airfoil shape generates various attack angle distributions depending on the choice of surface angle function. Moreover, ideal attack angle and ideal lift coefficient are susceptible to the choice of airfoil profiles and uniform loading area. High ideal attack angle signifies high pliability to upcoming wind, and high ideal lift coefficient involves high possibility to generate larger electric energy. According to results obtained pitch point, airfoil shape, uniform loading area, and the conformed airfoil surface angle function are crucial factors in the determination of angle of attack.

Experimental Investigation of Blade-To-Blade Pressure Distribution in Contra-Rotating Axial Flow Pump

  • Cao, Linlin;Watanabe, Satoshi;Honda, Hironori;Yoshimura, Hiroaki;Furukawa, Akinori
    • International Journal of Fluid Machinery and Systems
    • /
    • v.7 no.4
    • /
    • pp.130-141
    • /
    • 2014
  • As a high specific speed pump, the contra-rotating axial flow pump with two rotors rotating reversely has been proved with higher hydraulic and cavitation performance, while in our previous researches, the potential interaction between two blade rows was distinctly observed for our prototype rotors designed with equal rotational speed for both front and rear rotors. Based on the theoretical and experimental evidences, a rotational speed optimization methodology was proposed and applied in the design of a new combination of contra-rotating rotors, primarily in expectation of the optimized blade pressure distributions as well as pertinently improved hydraulic performances including cavitation performance. In the present study, given one stationary and two rotating frames in the contra-rotating rotors case, a pressure measurement concept taking account of the revolutions of both front and rear rotors simultaneously was adopted. The casing wall pressure data sampled in time domain was successfully transferred into space domain, by which the ensemble averaged blade-to-blade pressure distributions at the blade tip of two contra-rotating rotors under different operation conditions were studied. It could be seen that the rotor pair with the optimized rotational speed combination as well as work division, shows more reasonable blade-to-blade pressure distribution and well weakened potential interaction. Moreover, combining the loading curves estimated by the measured casing wall pressure, the cavitation performance of the rotor pairs with new rotational speed combination were proved to be superior to those of the prototype pairs.

Computational Analysis of 3-Dimensional Viscous Flow within Centrifugal Compressors (원심압축기 내부유동의 점성 3차원 해석)

  • Park, Mu-Ryong;Choe, Beom-Seok;Yun, Ui-Su
    • 연구논문집
    • /
    • s.24
    • /
    • pp.107-117
    • /
    • 1994
  • In aerodynamic design of centrifugal compressors, impellers are designed through preliminary design and blade profile generation. In order to find out faults of the initially designed impellers, the detailed informations about internal flow phenomena such as pressure distribution, flow separation, blade loading, etc are essential. These informations can be acquired with flow measurements or computational flow analyses. In this study, we calculated 3-D viscous flow in 4 back-swept impellers which were designed in our laboratory, and analyzed the flow characteristics which influence the performance of impellers.

  • PDF

Experiment of single screw piles under inclined cyclic pulling loading

  • Dong, Tian Wen;Zheng, Ying Ren
    • Geomechanics and Engineering
    • /
    • v.8 no.6
    • /
    • pp.801-810
    • /
    • 2015
  • The ultimate pullout capacity under inclined dynamic loading is an important measure of the destruction degree of vertical screw piles (anchors) under dynamic actions. Based on the static and dynamic tests on two kinds of model screw piles, the ultimate bearing capacity was researched considering different distance-width ratio of blade (D/W) and preloading ratio. The results compared well with other experimental data available in the literature. This research reveals that D/W might determine the failure model of the piles (anchors), for example D/W = 3.14 or 5; a critical dynamic-static loading ratio (DSLR) existed in the experiments. The critical DSLR was reached under the conditions of 40%~60% preloading (D/W = 3.14) or 20%~40% preloading (D/W = 5), respectively.

Radiation Characteristics of Noise Generated by Steady Loading on Rotating Blade (회전익 표면의 정상하중에 의한 소음의 방사특성)

  • Jeon, Wonju;Lee, Duck-Joo
    • Journal of the Korean Society for Aeronautical & Space Sciences
    • /
    • v.36 no.4
    • /
    • pp.307-314
    • /
    • 2008
  • Loading noise generated by steady aerodynamic force exerted on the rotating body surface is theoretically analyzed and its radiation characteristics is examined as a fundamental research of helicopter rotor noise. For simplicity, the force exerted on each blade is not distributed but concentrated at one point and the noise is evaluated by using Lowson' exact formula with a discussion of the physical meaning of each term in the formula. For a single point force rotating with various angular frequencies, we investigated the radiation characteristics and theoretically explained the physical behavior at near and far-field. By investigating the amplitude of acoustic pressure with various distances, we observed the different decreasing ratio at near- and far-field with the discussion of the effect of acceleration of angular frequency. Finally, the phenomenon that the noise level is reduced everywhere as the number of blade increases is explained with the suggestion of a noise reduction idea, the limitations of this study, and the future research topics.