Dynamic responses of elastic marine propellers in non-uniform flows

This paper focuses on the development of a three-dimensional panel method in time and frequency domains combined with the finite element method for analyzing the hydroelastic responses of rotating marine propellers in the wake of ships. A fully non-penetration boundary condition imposed on the deformed blade surface is conducted, in which the corrections of both the incoming flow velocities and the normal vectors imposed on the deformed and undeformed blade surface are taken into account. The added-mass and -damping matrices due to strongly coupled fluid-structure interaction are considered. Results of the present method are compared with experimental data available in the literature. It is observed that the fully non-penetration boundary condition applied on the deformed blade surface should be imposed to predict the unsteady performance of elastic propellers, which is due to the change of the added damping predicted by considering different non-penetration boundary conditions.

Effects of inlet guide vane and blade pitch angles on the performance of a submersible axial-flow pump

This study investigates the effects of inlet guide vane (IGV) and blade pitch angles on the steady and unsteady performance of a submersible axial-flow pump. To analyze the interaction between the IGVs and the rotor blades, both steady and unsteady three-dimensional Reynolds-averaged Navier-Stokes equations were used with shear stress transport turbulence closure. Hexahedral meshes were used in the computational domain. The numerical results for performance curves showed good agreement with experimental data. The results showed that the steady and unsteady performance characteristics were dependent on both the IGV and blade pitch angles. Adjusting these angles affected the total pressure rise and thus caused variation in the efficiency in overload conditions. But adjusting these angles affected the unsteady pressure fluctuations in partial-load conditions. Detailed flow analyses were performed to find the root-cause of these phenomena.

TURBODYNA: Centrifugal/Centripetal Turbomachinery Dynamic Simulator and Its Application on a Mixed Flow Turbine

One-dimensional (1D) modeling is crucial for turbomachinery unsteady performance prediction and system response assessment. The purpose of the paper is to describe a newly developed 1D modeling (turbomachinery dynamic simulator (TURBODYNA)) for turbomachinery. Different from classic 1D modeling, in TURBODYNA, rotor has been meshed and its unsteadiness due to flow field timescale is considered. Instead of direct using of performances maps, source terms are added in Euler equation set to simulate the rotor. By comparing 1D modeling with three-dimensional (3D) computational fluid dynamics (CFD) results, it shows that rotor unsteadiness is indispensable for a better prediction. In addition, different variables response to pulse differently. In the rotor, mass flow is close to quasi-steady while entropy is significantly unsteady. TURBODYNA can capture these features correctly and provide an accurate prediction on pressure wave transportation.

Investigation of Unsteady Performance Characteristics of a Submersible Axial-Flow Pump for Different IGV and Blade Pitch Angles

This paper presents a study of the effects of blade pitch angle and inlet guide vane (IGV) angle on the performance of a submersible axial-flow pump. To analyze the interaction effects between the IGVs and the rotor blades, both steady and unsteady three-dimensional Reynolds-averaged Navier-Stokes equations with shear stress transport turbulence model were solved. Hexahedral meshes were used in the computational domain and a grid-dependency test was performed to obtain an optimal number of grid nodes. The performance curves obtained by numerical simulation showed good agreement with experimental data. The results show that the fluctuation of hydraulic efficiency and head coefficient increased significantly under overload conditions as the IGV setting angle increased. Additionally, both the steady and unsteady performance characteristics were shown to be quite dependent on the combination of IGV angle and blade pitch angle, because the relative velocity at leading edge played an important role in the performance under overload conditions.

TURBODYNA: Centrifugal/Centripetal Turbomachinery Dynamic Simulator and its Application on a Mixed Flow Turbine

1D modelling is crucial for turbomachinery unsteady performance prediction and system response assessment. The purpose of the paper is to describe a newly developed 1D modelling (TURBODYNA) for turbomachinery. Different from classic 1D modelling, in TURBODYNA, rotor has been meshed and its unsteadiness due to flow field time scale is considered. Instead of direct using of performances maps, source terms are added in Euler equation set to simulate the rotor. By comparing 1D modelling with 3D CFD results, It shows that rotor unsteadiness is indispensable for a better prediction. In addition, different variables response to pulse differently. In the rotor, mass flow is close to quasi-steady while entropy is significantly unsteady. TURBODYNA can capture these features correctly and provide an accurate prediction on pressure wave transportation.

Analysis on the effect of variable guide vane numbers on the performance of pump as turbine

To study the effects of different guide vane numbers on the unsteady performance of pump as turbine based on the Navier–Stokes equation and standard k-epsilon turbulence model, computation fluid dynamics technology was used to simulate the flow field in pump as turbine. The turbulent kinetic energy, unsteady radial forces, and power losses were also clarified. The results show that for turbines with a guide vane, the distribution of turbulent kinetic energy is more uniform than before, and the radial force vector distribution is more symmetrical within four quadrants. The time-domain distribution of radial force is more periodic, the number of fluctuation periods is equal to the guide vane numbers, and the dominant frequency of the radial force is equal to the blade frequency. For different guide vane numbers, the effects on the unsteady performance of pump as turbine are different. When the guide vane number is equal to 9, the distribution of turbulence kinetic energy is optimal. In addition, at an optimal flow rate, both the time domains of the radial force and the power losses of the impeller are minimal, so to the geometric parameters of the hydraulic turbine are definite, the optimal guide vane number exists.