Analysis of inlet flow passage conditions and their influence on the performance of an axial-flow pump

The inlet flow conditions will directly affect impeller performance, which is of great concern to pump designers. In this study, based on two axial-flow pump devices, the influence of the evaluation criteria of inlet flow conditions and numerical grid scales on the accuracy of the simulation are investigated, the correctness of the numerical simulation are verified by experiments. The axial velocity distribution uniformity, axial velocity weighted average angle and hydraulic loss are calculated with three grid scales commonly used in engineering. The applicability of three turbulence models in engineering is verified. The influence of the uniformity of the axial velocity distribution on the impeller is quantitatively explored by installing a group of vortex generators. The results show that the simulation errors of the common formula of the axial velocity distribution uniformity for the elbow inlet passage and front-shaft tubular inlet passage are 16.3% and 14.6%, respectively; the modified formula limited the computational error to 0.2%, which reduced the axial velocity distribution uniformity dependence on the grid. The quantitative relationship between inlet flow conditions and pump performance was established, as the impeller efficiency decreased linearly with decreasing axial velocity distribution uniformity.

Experimental Investigation of propeller Wake Velocity Field for the Major Factors Affecting Propeller Wake Wash

The propeller jet from a ship has a significant component directed upwards towards the free surface of the water, which can be used for ice management. This paper describes a comprehensive laboratory experiment where the influences of operational factors affecting a propeller wake velocity field were investigated. The experiment was done on a steady wake field to investigate the characteristics of the axial velocity of the fluid in the wake and the corresponding variability downstream of the propeller. The axial velocities and the variability recorded were time-averaged. Propeller rotational speed was found to be the most significant factor, followed by propeller inclination. The experimental results also provide some idea about the change of the patterns of the mean axial velocity distribution against the factors considered for the test throughout the effective wake field, as well as the relationships to predict the axial velocity for known factors.

Effect of Twisted Slice on Fluid Dynamics Performances of Fluid Media in Cracking Furnace Tube

Employing air at normal temperature and pressure as fluid media, the effect of twisted slice on fluid dynamics performances of fluid in cracking furnace tube was studied. The experimental results showed that boundary layer in cracking furnace tube fixed with twisted slice became thin, which leaded to the increase of heat transfer coefficient. So heat transfer was enhanced. Axial velocity distribution in central area of the tube fixed with twisted slice was smoother than that of circular tube, while velocity grad in near wall area was greater. Pressure drop increased in the tube fixed with twisted slice, whereas pressure distribution was even along axial length of the tube, in agreement with the pressure distribution in circular tube.

WALL COMPLIANCE EFFECT ON THE FLOW OF COMPRESSIBLE NON-NEWTONIAN FLUID

The peristaltic flow of Jeffrey fluid in a microchannel with compliant wall has been investigated. The rheological effects and compressibility of the fluid are given proper attention. Perturbation approach has been employed when the ratio of the wave amplitude to the radius of the pore is small. Expressions of perturbation function, mean axial velocity distribution, mean velocity at the boundaries and critical values are derived. The variations of various interesting parameters are shown and examined very carefully.

Investigations of Unsteady Flow Field Characters in Axial Flow Pump Based on Numerical Simulation

Investigations of the unsteady flow field characters in a axial-flow pump at different conditions are presented in the paper. The numerical simulation of the unsteady flow field is performed with FLUENT codes based on RNG k-ε model and SIMPLEC arithmetic. Numerical results show that the strong-coupling evolutions of static pressure and axial velocity distribution between rotor and stator in multi-conditions are periodic with the rotation of rotor. The interaction of stationary and rotating pressure field leads to periodic flow field distortions and induces pressure fluctuation. It is found that the maximum pressure amplitude of blade passing frequency occurs in the rotor inlet zone, but it deceases very fast backward to the stator. The dominant frequency at monitoring points located at rotor inlet, outlet and stator outlet, corresponds to the blade passage frequency. The axial velocity distortion resulting from the modulation of the interacting stationary and rotating flow field is affected by the blade numbers and thickness of both rotor and stator. The axial velocity has different distributions at different conditions, and the phase of it changes cyclically. However, the axial velocity distribution at stator outlet is also mainly affected by the stator blade numbers, but its phase does not change cyclically.

Axial Velocity Distribution at the Efflux of a Stationary Unconfined Ship’s Propeller Jet

This paper is aimed at presenting an up-to-date investigation of the hydrodynamics of the jet (wake) of a stationary, unconfined ship’s propeller. The velocity field of a ship’s propeller jet is of particular interest for the researchers investigating the jet induced damage on a seabed as documented in previous studies. This paper discusses the time-averaged velocity field at the efflux, which is the immediate exit of the downstream propeller jet. The propeller jet is a rotating flow, which has axial, tangential and radial components of velocity. The axial component of velocity is the main contributor to the total velocity magnitude. Researchers are more interested in the axial velocity field within the ship’s propeller jet, due to the large contribution made by the axial velocity to the jet. The axial velocities at the efflux plane were obtained using joint experimental and numerical approaches. The results confirmed the two-peaked ridges axial velocity profile and disagreed with the 0.707Dp contraction suggested by Blaauw & van de Kaa (1978), Verhey (1983) and Robakiewicz (1987) at efflux of a ship’s propeller jet.