Small wind turbines – A unique segment of the wind power market

Ejectors used in refrigeration systems as entrainment and compression components or expanders, alone or in combination with other equipment devices, have gained renewed interest from the scientific community as a means of low temperature heat recovery and more efficient energy use. This paper summarizes the main findings and trends, in the area of heat-driven ejectors and ejector-based machines, using low boiling point working fluids, which were reported in the literature for a number of promising applications. An overall view of such systems is provided by discussing the ejector physics principles, as well as a review of the main developments in ejectors over the last few years. Recent achievements on thermally activated ejectors for single-phase compressible fluids are the main focus in this part of the review. Aspects related to their design, operation, theoretical and experimental approaches employed, analysis of the complex interacting phenomena taking place within the device, and performance are highlighted. Conventional and improved ejector refrigeration cycles are discussed. Some cycles of interest employing ejectors alone or boosted combinations are presented and their potential applications are indicated.

https://www.mdpi.com/2411-5134/4/1/16/pdf

Current Advances in Ejector Modeling, Experimentation and Applications for Refrigeration and Heat Pumps. Part 1: Single-Phase Ejectors

A novel small scale efficient wind turbine for power generation

A new type of horizontal axis wind turbine adopting the Archimedes spiral blade is introduced for urban-use. Based on the angular momentum conservation law, the design formula for the blade was derived using a variety of shape factors. The aerodynamic characteristics and performance of the designed Archimedes wind turbine were examined using computational fluid dynamics (CFD) simulations. The CFD simulations showed that the new type of wind turbine produced a power coefficient (Cp) of approximately 0.25, which is relatively high compared to other types of urban-usage wind turbines. To validate the CFD results, experimental studies were carried out using a scaled-down model. The instantaneous velocity fields were measured using the two-dimensional particle image velocimetry (PIV) method in the near field of the blade. The PIV measurements revealed the presence of dominant vortical structures downstream the hub and near the blade tip. The interaction between the wake flow at the rotor downstream and the induced velocity due to the tip vortices were strongly affected by the wind speed and resulting rotational speed of the blade. The mean velocity profiles were compared with those predicted by the steady state and unsteady state CFD simulations. The unsteady CFD simulation agreed better with those of the PIV experiments than the steady state CFD simulations.

Experimental and Numerical Study of the Aerodynamic Characteristics of an Archimedes Spiral Wind Turbine Blade

CFD simulation of two-phase ejector performance influenced by different operation conditions

A water-driven annular type ejector loop is designed and constructed for air absorption. Fabricated ejector unit is horizontally installed in the loop, and annular water jet at the throat entrained atmospheric air through the circular pipe placed at the center of the ejector. The tested range of water flow rate is 160 L/min to 320 L/min and volumetric flow rate of water and air and local pressure are quantitatively measured using LabVIEW signal express program. For the quantitative measurement of bubble velocity, cinematic PIV technique using a high speed camera is adapted. In post processing, each bubble is used as seeding particles and ensemble averaged bubble velocity field at vertical plane of the ejector system is finally acquired. In the range of experiment, the bubble size distribution at downstream of the ejector seems to be quite uniform so that the flow can be classified as a homogeneous bubbly flow. In case of low range of water flow rate, the transition from bubbly flow to stratified flow occurs at the atmospheric outlet condition. As a comparative study, a numerical simulation on the same ejector shape is performed to understand the more detail hydrodynamic characteristics in the annular type ejector system. Homogeneous bubbly flow regime is used as default two-phase flow regime, and void fraction at the vertical plane of the ejector system is qualitatively compared with that of experiment. In volume flow rate comparison, numerical prediction agrees well with that of experiment where the homogeneous bubbly flow is maintained.

http://www.j-mst.org/On_line/admin/files/17-J2012-00441_2773-2781_2782백_.doc.pdf

An experimental and numerical study on hydrodynamic characteristics of horizontal annular type water-air ejector

This paper describes a new design of small-scale horizontal wind blade, called spiral wind turbine blade. Theoretical and numerical approaches on the prediction of aerodynamic performance of the blade have been conducted. A theoretical equation is successfully derived using the angular momentum equation to predict aerodynamic characteristics according to the design shape parameters of spiral blade. To be compared with the theoretical value, a numerical simulation using ANSYS CFX v12.1 is performed on the same design with the theoretical one. Large scale tip vortex is captured and graphically presented in this paper. The TSR- diagram shows a typical parabolic relation in which the maximum efficiency of the blade approximately 25% exists at TSR

https://www.koreascience.or.kr:443/article/JAKO201223352964075.pdf

A study on design and aerodynamic characteristics of a spiral-type wind turbine blade

Development of a dual optical fiber probe for the hydrodynamic investigation of a horizontal annular drive gas/liquid ejector

To investigate the aerodynamic characteristics of an Archimedes spiral wind turbine for urban-usage, both experimental and numerical studies were carried out. The Archimedes spiral blade was designed to produce wind power using drag and lift forces on the blade together. Instantaneous velocity fields were measured by two-dimensional PIV method in the near field of the blade. Mean velocity profiles were compared to those predicted by the steady state and unsteady state CFD simulation. It was found that the interaction between the wake flow at the rotor downstream and the induced velocity due to the tip vortices were strongly affected by the wind speed and resulting rotational speed of the blade. PIV measurements revealed the presence of dominant vertical structures at downstream the hub and near the blade tip. Unsteady CFD simulation results agreed well with those of PIV experiments than the steady state analysis. The power coefficient (Cp) obtained by CFD simulation demonstrated that the new type of wind turbine produced about 0.25, relatively high value compared to other types of urban-usage wind turbine.Copyright © 2013 by ASME

Yoon Kee Kim

Papers

Experimental and Numerical Study of the Aerodynamic Characteristics of an Archimedes Spiral Wind Turbine Blade

An experimental and numerical study on hydrodynamic characteristics of horizontal annular type water-air ejector

A study on design and aerodynamic characteristics of a spiral-type wind turbine blade

Development of a dual optical fiber probe for the hydrodynamic investigation of a horizontal annular drive gas/liquid ejector

Aerodynamic Characteristics of Horizontal Axis Wind Turbine With Archimedes Spiral Blade