A Simple Method for Predicting Drag Characteristics of the Wells Turbine

The drag characteristics of the Wells turbine are difficult to be accurately predicted because of the influences of many variables. Detailed analyses about the effects of these variables on the drag characteristics educe that the most sensifive parameters to the drag characteristics are the turbine solidity of the turbine and incidence angle of airflow. In this paper, an experimental research is conducted on the pressure drop across the flat- plate rotor which is used to simulate the Wells turbine. After nondimensionalization and fitting of the experimental data, a common experiential formula is obtained. Compared with the experimental data from literature, the computational results are satisfactory. Thus, this report provides a simple and convenient method for predicting the drag characteristics of the Wells turbine and optimizing the match design between an oscillating water column and a chamber.

Experiment of drag characteristics of a novel variable geometry flame-holder

A novel variable geometry flame-holder(VGF) based on V-gutter was presented.The structural characteristics of the flame holder were introduced.Experimental study on drag characteristics of the VGF on un-burning and burning states was conducted in a rectangular combustion test rig.The influence of the change of gutter trailing edge width w on pressure recovery in different operating conditions was analyzed emphatically.Furthermore,drag characteristics in different trailing edge width variation modes were discussed.Results show that:(1) Narrowing w can observably raise the total pressure recovery σ but the highest σ is not obtained at minimum w.(2) The relationship of drag coefficient ψ and w in the un-burning conditions can be well expressed in a form of exponential equation(w/d>0.4).(3) Drag characteristics are not sensitive to the variation modes and speeds of w.(4) In the burning condition,σ decreases with the increasing of w basically and the course can be divided into three stages.The results and experimental data presented in this paper would enhance the phenomenological understanding of this type of VGF,and would contribute to the next experimental study and numerical calculus of this novel VGF.

A Review of Methods Based on Nanofluids and Biomimetic Structures for the Optimization of Heat Transfer in Electronic Devices

Nowadays,the utilization rate of electronic products is increasing while showing no obvious sign of reaching a limit.To solve the associated“internal heat generation problem”,scientists have proposed two methods or strategies.The first approach consists of replacing the heat exchange medium with a nanofluid.However,the high surface energy of the nanoparticles makes them prone to accumulate along the heat transfer surface.The second method follows a different approach.It tries to modify the surface structure of the electronic components in order to reduce the fluid-dynamic drag and improve the rate of heat exchange.This article reviews these effects considering different types of nanofluid and different shapes,sizes,and arrangements of“biomimetic grooves”.The idea to use these two methods in a combined fashion(to improve heat transfer and reduce flow resistance at the same time)is also developed and discussed critically to a certain extent.

Realization of non HF air plasma cutting power source based on a complexisolated inverter

On the basis of analyzing and testing of common inverting circuits, a new type inverter, which has a special inverting circuit called complex isolated, has been put forward. In turn, an applicable air plasma cutting machine has also been put into use. Testing results show that this kind inverter has lots of properties as high reliability, high efficiency, good EMC(electromagnetic compatibility) and easy operating. The complex isolated inverting circuit can be considered as a quite valuable reference for the research of high power welding inverter.