Papers by Keyword: Contraction Ratio

Abstract: In the present paper, the incipient cavitations number was analyzed by theoretical considerations. By using simulation methods, it could be regarded that the incipient cavitations number was mainly dominated by the contraction ratio of the orifice plate. The less the contraction ratio of the orifice plate is, the larger is the incipient cavitations number. The effects of orifice plate’ thickness on the incipient cavitations number was not obviously and could be neglected. When Reynolds number is more than 10⁵, Reynolds number has little impact on the incipient cavitations number.

Abstract: Numerical simulation technology has been widely used to study the energy dissipation problem of hydroelectric engineering construction which combined flaring gate pier with stepped spillway. The main parameter of flaring gate pier is contraction ratio. This paper numerically simulated the length of aerated cavity and negative pressure of steps for stepped spillway combined with symmetrical Y-shape flaring gate pier which with the contraction ratio respectively of 0.4, 0.7 and 0.445. The RNG turbulence model ,VOF model of water vapor two-phase and iterative solution of geometry reconstruction format for unsteady flow has been applied to generate free surface. Velocity and pressure coupling method using PISO algorithm, with unsteady flow algorithm approaches stable solution of steady flow. And range from the upstream reservoir to downstream stilling basin. Comparatively analyze the experimental and simulation results of aeration cavity length, the two are basically in good agreement, and the maximum error is 10%. Therefore, the numerical simulation has a certain rationality and reliability. Simulation results show that aeration cavity length increased with the contraction ratio decreases, while the maximum negative pressure decreased, and more extensive distribution of negative pressure in stepped spillway.

Abstract: In order to study the aerated cavity length and negative pressure on stepped spillway which combined with Y-shape asymmetric flaring gate pier body type, this paper applied RNG turbulence model,VOF model of water vapor two-phase, iterative solution of geometry reconstruction format of unsteady flow to generate free surface. Numerically simulated the length of aerated cavity and negative pressure of stepped spillway which combined with asymmetrical Y-shape flaring gate pier that with the contraction ratio respectively of 598, 0.497 and 0.445, the range from the upstream reservoir to downstream stilling basin. And compared the simulation results with experimental results, found that the aerated cavity length on steps basically consistent with the measured cavity length, the maximum error is 9.7%. The simulation results shows that the aeration cavity length on steps increases with asymmetric flaring gate pier contraction ratio decreases, and the aerated cavity length of lateral side with smaller contraction angle is larger 4 to 5 times than lateral side with larger contraction angle.

Abstract: The contraction ratio of lower bucket is an important parameter of the series jet characteristics of the allotypic hybridtype flip bucket (AHFB). Due to the effect of contraction in lower bucket and diffused in upper bucket, the jet flows cross and impact in the space domain. Systematic hydraulic model tests were developed to describe the rule of water-diversion and pressure distributions. This paper presents the variation of jet trajectory length and the local scour of this combined bucket. Based on these, the variation laws and estimation equations for hydraulic characteristics with different contraction ratio are proposed.

Abstract: A novel radial telescopic tire building drum is proposed to meet the radial tire production requirements. After the discussion of the mechanical structure and transmission principle of this mechanism, the kinematics equations together with the formulas of contraction ratio and pressure angle are established. In order to optimize the characteristics of force-transfer, when taking the interference condition into consideration, a kinematics design method of this novel radial telescopic building drum is proposed, which can obtain the minimal value of mechanism maximum pressure angle and satisfy the demand of contraction ratio. The most important feature of this building drum is that the external shell is driven by the internal shell. Designer can derivative more design schemes by applying this transmission principle.

Abstract: The fluidic muscle cylinder consists of an air bellows tube, flanges and lock nuts. Its features are softness of material and motion, simplicity of structure, low production cost and high power efficiency. Recently, unlike the pneumatic cylinder, the fluidic muscle cylinder without air leakage, stick slip, friction or seals was developed as a new concept actuator. It has characteristics such as light weight, low price, high response, durable design, long life, high power and high contraction. In this study, we carried out finite element modeling and analysis on the main design variables such as contraction ratio and force, and diameter increment of the fluidic muscle cylinder. On the basis of finite element analysis, the prototype fluidic muscle cylinder was fabricated and tested. Finally, we compared the test results with the finite element analysis.