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Copyright of Journal of Architecture & Civil Engineering is the property of Chang'an Daxue Zazhishe and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The aerodynamic performance of blade affects the vibration characteristics and stable operation of turbomachinery closely. The aerodynamic performance of turbine stage can be improved by using swept blade. In this paper, the Reynoldsaveraged Navier-Stokes method and the renormalized group k-ε turbulence mode were adopted to investigate the unsteady flow characteristics and excitation force of swept blade stage. According to the results, for the swept blade, the fluid of boundary layer shifts in radial direction due to the influence of geometric construction. It is observed that there is similar wake development for several kinds of stators, and the wake has a notable effect on the boundary layer of the rotor blades. When compared with straight blade, pressure fluctuation of forward-swept blade is decreased while the pressure fluctuation of backward-swept blade is increased. The axial and tangential fundamental frequency excitation force factors of 15° forward-swept blade are 0.139 and 0.052, respectively, which are the least, and all excitation force factors are in the normal range. The excitation factor of the forward-swept blade is decreased compared with straight blade, and the decreasing percentage is closely related to the swept angle. As for backward-swept blades, the situation is the other way around. Additionally, the change of axial excitation factor is more obvious. So the vibration reduction performance of forward-swept blade is better. [ABSTRACT FROM AUTHOR]

Full 3-D unsteady numerical investigation on an axial air turbine in 50% partial admission is conducted. The partial admission turbines are under different unsteady loading and unloading process, as well as flow parameters, respectively. The loss coefficient and static pressure distributions at the key position are presented in detail to analyze the non-uniformity originated from partial admission. The results show that the non-uniformity decreases along flow direction and the efficiency of control stage also decreases but with the uniformity improved downstream of the rotors with increasing admitting numbers in equal partial admission degree. The reasons for efficiency decreasing are reasonably explained with windage and sector end losses presented by static entropy distributions. The periodic changes of unsteady forces in amplitude and direction are also compared and transformed in the frequency domain by fast Fourer transform method. The largest circumferential exciting force factor which is remarkably larger than the corresponding axial exciting force factor decreases by 13.2% with the increase of admitting arc number. Compared with the common distribution of two symmetric admitting arcs, the maximum exciting force factor of triangle admitting arc distribution drops 11.3% with the mere efficiency decrease of 1.32%. The multiple admitting arc turbines are more conducive to be applied to submarines which concerns more about exciting force other than efficiency. Efficiency and unsteady forces are both worth being taken into consideration in the practical applications. [ABSTRACT FROM AUTHOR]

The phenomenon of resonance is described at the upper bracket of the hydroelectric generating unit at the Nizhnekamskaya HPP. The nature of exciting forces that lead to unacceptable oscillations in the support element of a hydroelectric generating unit structure is examined. [ABSTRACT FROM AUTHOR]

Copyright of Oil Drilling & Production Technology / Shiyou Zuancai Gongyi is the property of Shiyou Zuancai Gongyi Bianjibu and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

A theoretical and numerical investigation has been carried out to understand the exciting force generation mechanism of the pump jet propeller (PJP) with evenly spaced and unevenly spaced rotor blades (ESB and UESB), which operates behind a standard submarine model. Firstly, the exciting force of ESB was studied by the Reynolds-averaged Navier–Stokes (RANS) method. Numerical methods were validated by calibration model tests and independent studies. The results show that the two main components exist in exciting force of the rotor: symmetric (f = a BPF, a is a natural number) and asymmetric (f ≠ a BPF) exciting forces, and the formation mechanisms of these exciting forces are explained by the interference theory. Then, the exciting force equations of UESB were derived, and the optimal modulation amplitude (S) of UESB was obtained as 4.6°. The numerical results have validated the theoretical prediction that the exciting force of the UESB is reduced by 12.6% at blade passing frequency (BPF). Finally, an optimization process for UESB based on theoretical prediction and numerical simulation was proposed, in which the efficiency of optimization was improved when the theoretical method was introduced. The research is beneficial for comprehensive understanding of the exciting force of PJP and practical engineering design of noise-reduced PJPs. • Explanation for the formation mechanism of asymmetric exciting force. • Investigation on the exciting force characteristics of unevenly spaced blades. • A theory-based accelerating optimization method for unevenly spaced blades. [ABSTRACT FROM AUTHOR]

The basic theory on the structural transfer path analysis of noise is presented and the measurement method of excitation force is analyzed in detail. With the tire/road noise of a vehicle as example, a transfer path analysis model is built and a structural transfer path test is carried out. Meanwhile the resultant interior noises at target points are calculated with a result well agreeing with test data. By calculating coupled excitation force and sound/vibration transfer function, it is found that the top three transfer paths having greatest contributions on interior noise are those going through the connecting points of right / left rear axles and left shock absorber with vehicle body. With the modification of rear axle structure, the issue of tire/road noise of the vehicle is successfully resolved. [ABSTRACT FROM AUTHOR]

Two coaxial vertical cylinders-one is a riding hollow cylinder and the other a solid cylinder of greater radius at some distance above an impermeable horizontal bottom, were considered. This problem of diffraction by these two cylinders, which were considered as idealization of a buoy and a circular plate, can be considered as a wave energy device. The wave energy that is created and transferred by this device can be appropriately used in many applications in lieu of conventional energy. Method of separation of variables was used to obtain the analytical expressions for the diffracted potentials in four clearly identified regions. By applying the appropriate matching conditions along the three virtual boundaries between the regions, a system of linear equations was obtained, which was solved for the unknown coefficients. The potentials allowed us to obtain the exciting forces acting on both cylinders. Sets of exciting forces were obtained for different radii of the cylinders and for different gaps between the cylinders. It was observed that changes in radius and the gap had significant effect on the forces. It was found that mostly the exciting forces were significant only at lower frequencies. The exciting forces almost vanished at higher frequencies. The problem was also investigated for the base case of no plate arrangement, i.e., the case having only the floating cylinder tethered to the sea-bed. Comparison of forces for both arrangements was carried out. In order to take care of the radiation of the cylinders due to surge motion, the corresponding added mass and the damping coefficients for both cylinders were also computed. All the results were depicted graphically and compared with available results. [ABSTRACT FROM AUTHOR]

The working frequency selection of the ZK30525 vibrating screen was studied using ANSYS. Integrating the dynamic performance simulation analysis of the vibrating screen structure, the variation laws of beams' vibration displacements changing with different exciting frequencies were researched. These beams include six beams, with one discharging beam and one in-material beam. Results indicate that vibration displacements in the middle of these beams increase with the augmentation of exciting frequency. When exciting frequency exceeds a certain value, there exists a flat change region for vibration displacement. According to vibrator characteristics, the vibrating screen's working frequency should be selected in the flat change region, and be far away from modal frequencies. The study provides theoretical guidance for the reasonable working frequency selection of the large-scale vibrating screen. [ABSTRACT FROM AUTHOR]

The use of biaxial four-shaft vibration generators set in motion in pairs by two electric motors is substantiated for vibroseismic sources. The scheme of the generator is proposed. [ABSTRACT FROM AUTHOR]

This work mainly analyzes the variation laws of exciting force, pulsating pressure, velocity distribution and hydrodynamic parameters of PJP at different tip clearances (δ =0.5 mm, δ = 1 mm, δ = 2 mm) and different oblique flow angle (0°, 10°, 20°). In this study, the turbulence model SST k - ω and Reynolds-Stokes equations (RANSE) method have been adopted. The fully structured grid and full channel model have been adopted. And the grid independence of three different tip clearances was verified. In this study, the variation laws of exciting force, pressure coefficient and the hydrodynamic coefficients differences have been studied at the different tip clearances and different oblique flow angle. And the time-domain data of the pulsating pressure of PJP with cavitation conditions or without cavitation conditions was presented, and then which was converted to frequency domain data by fast Fourier transform (FFT). The results show that the torque balance performance of the PJP is broken in oblique flow. The tip clearances have a little effect than the oblique flow angle. The maximum efficiency loss is 19.17% at high oblique angle. The bearing force had a certain phase difference in different tip clearance, the phase shift to the right as the tip clearances increases. At the small advance J = 1.18, the efficiency with cavitation is greater than non-cavitation condition in oblique flow. In addition, the velocity distribution and the water vapor phase volume fraction of rotor outlet in different oblique flow angles and different tip clearances have been investigated. • The variation laws of bearing force, pressure coefficient and the hydrodynamic coefficients have been represented at different oblique angle and different tip clearances. • Give the comparison of the pulsating pressure and hydrodynamic coefficients differences with non-cavitation or cavitation condition. • The water vapor phase volume fraction at different conditions were discussed. [ABSTRACT FROM AUTHOR]