Product design innovation based on the functional characteristics of the eight-masted windmill

To catch and research the functional characteristics of the eight-masted vertical windmill and its automatic readjustment of sail angle in the Lixia River area of northern Jiangsu Province, to permit this intangible cultural heritage a new practical meaning in modern tourism through the innovative design of the sail structure of the eight-masted windmill, and to come up with a portable folding windmill product suitable for outdoor sports enthusiasts. Firstly, we spell out the history of the eight-masted windmill and its “trotting horse lamp” structure through literature research and draw the working principle of the eight-masted windmill in operation, and combine the eight-masted windmill with power generation device by converting wind energy into electricity. The design direction was to design a lightweight, breeze start, and stable power output windmill generator; secondly, the sketch of the windmill main shaft structure and scheme were selected, and the integrated form of the fan blade and the mast was selected as the sketch scheme; finally, the model experiment of the prototype of the folding scheme was conducted, and the absolute pressure difference between blades was analyzed by hydrodynamics to determine that the windmill can be used to generate electricity. After verifying its feasibility, the portable folding generator was modeled in 3D by MCAD, and make a physical model of the generator was made in a reduced scale of 1:2.5. Through the innovative design of the eight-masted windmill, it is made to serve the production life of modern society.


Introduction
China is quite rich in wind power resources and there have been precedents for large-scale utilization of wind power, among which the use of vertical axis windmills in river, lake, and sea areas cannot be ignored.For thousands of years from ancient times to the present, the use of wind power has gone through several stages of development, from the initial use of wind power to drive ships forward, to the vertical axis windmills (vertical axis windmills) that people began to use popularly for irrigation in the Song Dynasty, entering the golden age of applying windmills.However, the development of wind energy technology was slow, and the application for vertical axis windmills was mainly concentrated in areas with rich wind resources such as rivers, lakes, and seas in China [1] .The eight-masted windmill is a kind of vertical axis windmill that is now almost extinct but was once used on a large scale, mainly in the Jiangnan area and is now protected and studied as an intangible cultural heritage in Yancheng City.To study the structural principles of the eight-mast windmill components connection and sail adjustment, and apply them to modern production life through its innovative design.In addition, the eight-masted windmill, an ancient machine with Chinese cultural heritage, is empowered by modern methods based on 3D modeling and computational fluid dynamics, as well as by innovative design for the applicable population.The study brings the eight-masted windmill into the public eye and combines the advantages of the eight-masted windmill with the production life of modern society to design a portable power generation device that meets the needs of outdoor sports enthusiasts, giving new life to the traditional craft of making the eight-masted windmill, which is about to be lost, and providing a reference for the innovation of other ancient machines.

History of the eight-masted windmill
The windmill is both a witness of China's historical changes and the essence of Chinese folk cultural heritage.Among the many types of windmills, the most noteworthy is the eight-masted vertical windmill, a unique Chinese irrigation tool for agricultural production that was widely used during the Han and Tang dynasties [2] (Fig. 1).Before the advent of electric pumping tools, farmers in the past could only channel water to their fields by wind or human power, which the eight-masted vertical windmill played the role of providing power [3] .In case of heavy flooding, the slotted barrel of the windmill was moved to the field, which also served to drain the water in addition to carrying water for irrigation, showing the usefulness of the eight-masted windmill in the period of farming civilization [4] .Its production method is mainly manual, and the production method and process are complicated, requiring high experience and technology of the craftsman, which is one of the reasons for the loss of this wisdom.The core process of the eight-mast windmill is attractive because of its structural peculiarities and the windmill automatically adjusts the direction of the sails with the wind direction in the process of operation, etc. [5] , which is different from other windmill principles, and it is necessary to find suitable application scenarios after how to use its structural peculiarities and through innovative design.

Analysis of the structure of the eight-masted windmill
The eight-masted windmill is made of wood such as a mulberry tree, and is shaped like a "trotting horse lamp".The wind wheel is a square octagonal structure, and eight sails of the same size are mounted on the columns of the square octagonal structure.According to mechanical research, the upper part of the wind wheel is large and the lower part is small, which enhances the capturing power of the wind, and the vertical axis at its center can run with the wind.When the wind acts on the wind wheel, the sail will drive the wind wheel together and the vertical shaft will also run with it.There is a gear at the lower end of the vertical shaft, which meshes with the gear on the horizontal shaft, and the power is transferred to the horizontal shaft, which drives the working machinery (keel waterwheel) to run continuously to achieve the purpose of lifting water.The most informative aspect of the eight-masted windmill is the sail adjustment principle and the sail adjustment device, which cleverly controls the angle of each sail through the rope so that when the sail is on the downwind side, the sail has the largest possible wind area and thus has more driving force (Fig. 2).In the upwind environment, the wind area of the sails is as small as possible, or even zero, so that the wind resistance torque is reduced, thus increasing the operating efficiency of the eight-masted windmill.Secondly, another core structure of it is a low-speed clutch, i.e., a large shaft driving a small shaft [6] .

Windsurfing
Limit ropes

Windmill Stand
No force

Force applied
Windmill turning counterclockwise Fig. 2 Principle of sail adjustment of vertical axis windmill

Innovative design of the eight-mast windmill concept
The structure of the eight mast windmill is distinctive and has outstanding advantages, similar to the structure of the now widely used vertical axis wind turbine.Vertical axis wind turbines can be divided into resistance type and lift type according to the working principle, among which Savonius is a lift type wind turbine.In addition, with the rapid development of camping economy, the demand for portable generators from outdoor sports enthusiasts is increasing.Combining the above two points, the eight-mast windmill is combined with the power generation device for innovative design.

Design Direction Determination
The direction of the concept development was determined as portable generator design, therefore, the concept was determined based on the concept fusion method, integrating the excellent products and important concepts related to folding, and the basic concept of "eight mast windmill + Savonius type + folding" was derived as the design direction.Due to the simplicity of the O-Wind single rotating axis design and the absence of wind direction requirements, it requires less maintenance than conventional wind turbines.By combining the advantages of the eight-mast windmill, i.e., the variable-direction fan blade, with the O-Wind's feature of absorbing the universal wind direction, and by giving it a folding feature, the design concept of a portable generator that can be used under specific conditions was achieved.At the same time, the process of concept development was influenced by the hierarchy of design methods, and the basic function and form of the product was summarized in a declarative sentence (Point of view) in the early stage, i.e., a portable foldable eight-mast single-axis wind turbine generator designed to capture wind energy(Table 1).Table 1.

Schematic diagram of concept selection and integration
Since the referenced O-Wind and Savonius-type S-generators have very significant resistance to chaotic winds that rotate the fan blades in one direction, and since the wind type "valley wind" in mountainous areas also has chaotic wind characteristics [7] , this fusion concept is a reasonable solution for this particular need.

Group
Eight

Determination of design objectives
There are three main points in the design of this portable generator product: • Lightweight: it needs to meet the requirements of lightweight in terms of size setting and material selection, and to meet the size that can be easily carried after folding (using a folded umbrella as a reference).
• Breeze start: the design of the windmill product requires a large starting torque, low starting wind speed ,and relatively low peak speed.
• Provide stable power output: the electronic devices supplied by the product are mainly cell phones, tablets ,and other low-power devices, which need to have stable output power, and the design charging voltage is 5-10V and current is 1-3A.

Sketching of the windmill product
Sketching and optimization are carried out to simplify the structure, and the design is carried out by adding a spring-retractable structure and a rotating shaft structure.At the same time it has the feature of no disassembly and is designed as a fan mast in one form, while the rotating base and energy device are made into one, and a battery is added, so it can be used as a rechargeable battery when there is a mobile demand (Fig. 3).It can be seen that the folding structure is special, it is folded by the way of triangle to three sides constraint, this structure can limit the blade support rod length at the same time, if the longest side of the triangle and the axial side is determined and the horizontal support axis length is variable, to make the axial side and the horizontal side reach a right angle relationship, then the length of the horizontal axis will be compressed, if the horizontal axis material is elastic material and in the presence of pressure on both sides If the material of the horizontal shaft is elastic and the pressure on both sides is such that the center of the shaft can be shifted to the horizontal normal of its side to bend the whole structure, thus forming an "S-shape", then the necessary condition for the generator to rotate in one direction will be achieved.The four elastic cords will also be constrained so that the whole blade will form an inward shape, allowing for better wind energy capture.

Product structure and function determination
The product blade is pressed by two layers of DuPont paper, for one side of the upper and lower two triangular blade of each three sides are left along the side of the normal 5mm space to make the rope along the edge from the inside of the blade through and respectively fixed on both sides, for the middle of the blade is left for the width of 3cm long 50cm elastic sheet through the space, elastic sheet tail fixed in the middle of the three ring axis difference of 120 °self-locking structure, the top is placed in the blade The top is placed inside the blade.When it is necessary to fold, the sliding sleeve fixed with the elastic sheet and the self-locking structure of the support arm is moved axially to realize the folding of the fan blade (Fig. 4).

Fig. 4 Folding solution display
The volume before and after folding is very different, which meets the need for portability in the folded case, and when unfolded, it can have enough wind area to generate enough torque to drive the motor to generate electricity.It is possible to make the mechanical structure as simple as possible, only through the three rotating shafts and the ring buckle ,and the elastic sheet to ensure the functionality of the structure; it is possible to fit the Savonius-type (hereafter referred to as S-type) wind turbine better, by restraining the elastic sheet with a longer length on both sides and bending it to fit the structure of the S-type wind turbine while ensuring the volume after folding [8] (Fig. 5).By adjusting the position of the fixing rope, it is fixed to the thin mast bar.At the same time, the upper and lower hooks are positioned at 180°to the centerline of the main shaft, so that the mast can be bent at a specific position.Compared to the fixed structure S-generator, the rectangular structure of the wind surface on the side has been optimized into two triangular pieces (Fig. 6).Although the wind area is about 50% smaller, the size of the improved structure is significantly smaller than the normal S-generator when it is folded, and the length is also reduced to achieve the design goal of easy portability.

Product hydrodynamic simulation
Through the fan blade mast integrated morphological sketch scheme and the force-constrained folding scheme are determined, the next product computational hydrodynamic simulation is carried out, the purpose is to verify the effectiveness of blade rotation.Firstly, the experimental model of the blade is built by Solidworks, and secondly, the model is exported and processed by ANSYS Fluent, the fluid domain is divided, and then the fluid simulation is solved by dividing the mesh (Fig. 7).2), Simulation of computational fluid dynamics is then performed(Fig.8).Through the computational fluid dynamics (CFD) simulation results from the model absolute pressure clouds can be observed that the right side of the blade is larger than the pressure of the left side of the blade, that is, the pressure difference, so this blade structure can drive the windmill rotation (Fig. 9).

Product 3D modeling
The product modeling was carried out using MCAD software and rendered after completion(Fig.10).The rendering was done through Blender and different materials were given to each part of the model to achieve a complete design expression (Fig. 11).The next product material selection, according to one of the requirements of easy portability for the material weight requirements very strict, while the generator needs to have a certain weight to keep it stable in operation, therefore, for the middle spindle material is selected as carbon fiber round tube.The side support elastic sheet is made of manganese steel sheet, because, in this design condition, it needs to meet good toughness and plasticity, and it is not a part to be displayed outside, so it does not need to be painted.The more special material is the windward side of the sail, made of DuPont paper Tyvek, which has good protection, chemical resistance ,and water protection, making it the windward material of choice for working in extreme conditions, while its lightweight, compared to ordinary cloth, is only a fraction of the weight of cloth [9] .It is also soft and highly resilient, making it ideal for sail-making materials.

Fig. 12 Physical model of the product
By 3D printing to present the model form, a 1:2.5 scale down model is made, and the associated internal parts are assembled to obtain the physical model of the product (Fig. 12).
In the process of APP design, the special characteristics of outdoor sports enthusiasts were fully considered, so the APP provides an online community for these special people to communicate [10] .There are three functions in the function page of the APP, the first one is "Environment", which can display the current environmental status, such as temperature, humidity and so on.The second is "Battery", as the original design of the product is to use the product to generate and recharge power when the user stays in a fixed area, this function can see the battery charging and power generation status.The third is the ability to help users plan their travel routes, while allowing them to see what other outdoor enthusiasts (with the user allowing the app to collect personal data) are doing in the area, as well as popular hiking routes, so that they can have a better hiking experience (Fig. 13).Fig. 13 APP system interface design

Conclusion and Prospect
We have discussed how to use the special structural characteristics of the eight-mast windmill to innovate and design products that are meaningful to the current social production life, namely, combining the eight-mast windmill with the power generation device as the design target and making design innovation.At the design level, the advantages and structure of the eight mast windmill are combined with its space-saving structure to make it portable and lightweight to meet the growing demand for mobile portable generators.The basic form and functions were finalized through sketching and scattering, and the structure and functions that best fit the characteristics of the eight-mast windmill were derived.Functional simulations were performed in modeling, using MCAD software.After finalizing the basic structure design, the interface design of the windmill supporting APP was optimized for user experience to enhance the brand image.Then, through the research and selection of product materials and processing technology, it was determined to use carbon fiber and magnesium-aluminum alloy as the folding skeleton and Dupont paper as the fan blade.The mechanical characteristics of the eight-masted windmill are meaningful for the design and application of folding small generators, and give new life to the eight-masted windmill, an ancient Chinese traditional machine that almost disappeared.

Fig. 3
Fig. 3 Windmill product sketch scheme a.Model put away state b.Model force unfolding c.Model top view Fig. 5 Folding scheme prototype a. Overall meshing of the model b.Internal meshing of the model Fig. 7 Meshing of the model Regarding the ANSYS Fluent physical model, boundary conditions, and other solution parameters settings (Table

Fig. 9
Fig. 9 Absolute pressure cloud of the blade

Table 2 .
Fluent solution parameters settings