Experimental Study And Prototype Development Of An Archimedes Screw Generator

Archimedes screw has a long history of application in the process of human civilization,and from agricultural pumps of ancient Egypt to transport material or transplant heart in the modern Archimedes screw has been improved and played an important role in many fields.At the end of the 20 th century,it got a new life in the field of micro-hydropower,European people firstly developed Archimedes screw generator getting the inspiration from Archimedes screw pump.It is efficient,eco-friendly,applicable for low head,and can create many ecological and economic benefits,so it has been used in the occasion of low head in Europe and causes a new research boom overseas,but in China there are not relevant researches or application reports.Archimedes screw generator is a new equipment of developing distributed energy,it can not only supply power for remote mountainous areas,agricultural equipment,water treatment equipment in city,but also recovery surplus energy of the reservoir and hydropower station.China has countless low-head resources,and the government strongly support the development of distributed energy,so if the new hydropower equipment can be applied in China widely,it will not only be conducive to realize the objective of energy conservation,but also promote ecological civilization of the hydropower industry.This paper introduces the experimental study and prototype development of the hydroelectric power equipment,the main contents and results are as follows:1.The structure and main parameters of the equipment are introduced,and compared with the traditional micro-turbine,the main advantages and disadvantages of the device are described.And the current models of its efficiency are summarized:the Nagel model only considers the effect of the gap leakage on the efficiency,it is approximately accurate when the submerged depth is full;The Muller model simplifies the screw,the results show that the efficiency is related with gap leakage,geometric parameters and submerged depth;And the Murray model not only takes into account the geometrical parameters of the screw,but also introduces the submerged depth and speed,so it is a more comprehensive efficiency model.2.A low-head hydraulic experimental bench is built,and the screw and waterwheel are tested respectively.The results of the study shows:(1)The rotational speed of the two turbines is inversely proportional to the torque,and the speed range of the screw is wider than that of the waterwheel,but thetorque range of the screw is more narrow.(2)The power of the two turbines increases firstly and then decreases with the speed,In a certain speed range the power of the screw maintains the maximum,which is greater than the power of the waterwheel.So as long as an appropriate speed can be selected,the screw will have a higher power generation.(3)The efficiency of the screw increases firstly and then decreases with the speed,in a certain speed range the efficiency maintains a high level.And in wide speed zone the efficiency of the screw is greater than that of the waterwheel.3.A simplified model of the screw is established,then the parts of the prototype are selected and designed.And the key technical issues solved are as follows:(1)The water lubricated bearing which is easy for installation,disassembly and maintenance is designed,the structure of sealing device is eliminated to ensure the effect of water lubrication,and at the same time it does not cause water pollution;For the material of the sleeve and bearing,stainless steel and bronze which are wear-resistant and corrosion-resistant are selected,and they are suitable for the occasion with water and low speed.(2)With the special design of the bearing structure to solve the problem of processing accuracy which is due to the big size of the welding pieces,ensure that the screw and the outer cylinder are concentricity.And by the structural design to solve the problems of the processing and assembly of the prototype.(3)The main components such as screw,gearbox,generator,outer cylinder and bracket body are integrated to complete the structural design of prototype,and ensure to meet the processing requirements at the same time,thus reducing the amount of civil construction.4.Considering the applicability and simplicity of manufacturing the prototype,the selection plan of initial material needed for processing is given,and the processing technology of the parts such as the screw,the bracket,the bearing seat and the gland is introduced as well as the installation process and appearance maintenance of the prototype.The blades of the screw are difficult to produce,this paper describes a feasible method of stretching and welding.The manufacture of the prototype laids a good foundation for the following demonstration application.