книги / Innovative power engineering

The advantages of such systems are operating at relatively low winds and lack of infrasound, which have a negative impact on the natural environment [8, 9]. Wind rotates the rotor of the wind turbine, which in turn rotates the generator shaft, thereby converts the wind energy into electrical energy.

The need of inhibition. Wind power flow is a cubic dependence on the velocity, i.e. in excess of the rated wind speed of twice the power flow will increase by eight times. The world practice of using wind turbines is known that at high wind speeds (20…30 m/s) can be destroyed windwheel or overheating of the generator [10]. To prevent such a failure it is necessary to establish the elements for adjusting the rotor speed. One embodiment of such an element can be a device controlling the rotational speed of the rotor based on the frictional rubbing. Fig. 2 shows a diagram of the braking device.

Fig. 2 Braking device design: a – cams in the fixed mode; b – cams in the operation mode

Friction braking device. When the rotor jaws will be moved from the center to the periphery by centrifugal force, stretching the spring. As soon as the rotor speed reaches a rated value, the centrifugal force is sufficiently large in magnitude so that the cams press against the walls of the tower. As a result, the contact surfaces of the cams with the inner wall of the mast frictional rubbing occurs due to which, and braking will occur. The higher the speed of the rotor, the greater the

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centrifugal force presses the cams to the walls, and the greater the braking force of friction. If the rotor speed decreases, the centrifugal force decreases and the jaws under the influence of the spring returns to its original position braking ceases.

The centrifugal force F c cams presses against the inner surface of the mast. This prevents the force F sp, at which the spring pulls back the cams to the center. Tangency between the cams and the wall of the mast is possible provided:

where Fsp – spring tensile force, Fc – centrifugal force, m – mass of the cam, r – distance from the center of gravity from the axis of rotation of the cam, ’ – angular velocity of rotation of the rotor. The formula to determine the required spring force for a given angular velocity ’0, to which the rotor shaft rotates freely.

To implement the braking needed to pass cams could more torque than the one which has the rotor. Transmit the required torque can cams at an angular velocity 1, which is determined from the condition [11]:

where K – factor of safety (1,5…2); T – torque transmitted by cams; f – coefficient of friction; z – number of cams; D – internal diameter of the mast; ’1 – angular speed at which the braking process occurs; ’0 – angular speed at which the rotor shaft rotates freely. In the range between ’1 and ’0 stalled cams and brake rotor shaft.

The spring force in this case is [11]:

sp l3

where E – modulus of elasticity of the spring material; J – moment of inertia axial coil springs; x – deflection; l – length of one turn.

Efficiency is calculated by the pressure pad [p] on the friction surface.

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where S – area of the contact surface. From the area of the contact surface will also depend on the design and longevity. The greater the area of contact with the walls of the cam mast will be more uniform wear of the friction surfaces. However, for the smooth operation of the braking system requires that the cams are slipping and jamming occurred. The best option would braking device comprising three friction cam because combination of their mass, affecting the degree of tension springs, and surface area that affects the durability and performance, will be practical.

Because Mast is a fixed element of the design, instead of transmitting the torque of the rotor braking will occur, thus will provide automatic speed control. When the friction brake, a significant amount of heat. However, since brake drum is a steel mast and inhibition occurs only in windy conditions, the overheating can be avoided.

The advantages of the friction braking may include ease of manufacture, compared with the system controlling the angle of attack of blades. Minimum of moving elements are hidden from the precipitation, which increases the reliability, light weight of the rotating part.

Another important advantage of this device is that in a strong wind, when normally inhibit the generation of energy and wind wheel stops, the wind turbine continues to operate at the rated speed.

Conclusions. Friction braking device ensures safe operation of wind turbines, while delivering high reliability, and the cost of such an element will be quite small. Also represented braking device has a large resource of work and high maintainability.

References

1.$/& *-F F G : &@ '(5 G' /&'( ;; 0$% ( & (5 G : &'( & G'$:&5– > = < * C– 2. – 28–30.

2.Solomin E.V. Joint scientific research of Russian and German

^Z_X`V_^V^_`cX`XˆdvgXX`Xcbk;;0$% ( & (5G : &'(&G'$:&5– > = < * C. – 10. – 82–88.

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3. World Wind Energy Association // Japanese regions transition to 100 % renewable energy. – URL: // http://www.wwindea.org/home/index.php.

4.o 4 +'&, * o 4 +'&, /$.F G : &'( F6/6$6 & I(' 6 1 6 ( 7 / - + 8@& : (4 & &5 13Œ. 7($( 6 &8 ' 8 H . (2&&; “ G'$:&@ ' 8 7$& &'& &&. – >, 2011. –

5.$/& -F * K$. L D , &@ '& 3 & & 7 &- /+Π( G : &@ '&, + ( ' ;; 0$% ( & (5 G : &'(

&G'$:&5– > = < * C– 1. – 36–41.

6.$/& -F 7 ' & 6 & 7$%4 ( &5 /($6, G :- &@ '&, + ( ' (: 7 /6n$/ ' /7$' ;; > ,( &4(2&5

&G$' &I&'(2&5$% ' : , 458 (– >., 2011. – F67 7. – 12–15.

7.( CO . H . (2&5* > 9 ” Ox O; J C J

5 8 + ( '& &'($% 8 %B (Œ &5 ; • F m (, * -F $/& [& .]. – C J ; J– 4(5$ C C J– 7+3$ C C C * oB$ – C

8.$/& -F 1 6 / .$:&& (4 (3 '& &'($%–

6, G : &@ '&, + ( ' ;; 0$% ( & (5 G : &'( & G'$:&5– > = < * C– 1. – 18–28.

9.Solomin E.V. Development and optimizing of vertical axis wind

Vfcv_`X^;;0$% ( & (5G : &'(&G'$:&5– > =< *C–

1. – 29–39.

10.9& 7&@ &' ( >, >( %5 0 * $/& -F 3 (- 4 ( & G :&& G : &@ '&, + ( '(, ;; 0$% ( & (5 G : &'( & G'$:&5– > = < * C– 1. – 93–97.

11.0 + % F 7 ( @ &' ' +' (-/(n& &$5: O = D 2 / 7 . . .-. Y ' 8. – 8- &4. * 7 (3 & . 7 – >.: >(n& &, 2001. – 316 .

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THE DESIGN AND PRODUCTION OF VENTILATION WINDOWS BASED ON IONIC WIND AND ELECTROSTATIC PRECIPITATION

Sun Chen1, Liu Tianhao2

1Thermal Engine and Power Engineering, School of Energy Science and Engineering, Harbin Institute of Technology, China 2Electrical Engineering, Honors School, Harbin Institute of Technology, China

In order to introduce clean and fresh air for indoor in the haze weather, we made an air cleaning window based on Ionic Wind and Electrostatic Precipitation method. It uses multi-line net-Ionic Wind as the power of ventilation, increasing air velocity and introducing air into the room; uses dual-zone wire-plate type of Electrostatic Precipitator, removing of particles, killing bacteria and viruses. We use the TSI Aerosol Monitor and Thermal Anemometer to measure the performance of the equipment. Experimental results show that the self-developed air cleaning window is suitable for the haze weather with a wide range of dust, and the efficiency can reach more than 92 %; Wind speed can reach 1.24 m/s in vent steady uniform flow, and ventilation 203m3/h, to meet the needs of indoor ventilation. Compared to the prior art, this equipment can greatly improve air quality indoors under the haze weather.

Keywords: ionic wind; electrostatic precipitation; room ventilation; indoor air quality; hazy weather.

Haze attacked China in recent years, which has caused big damage to people’s health[1, 2]. People always spend more time indoors than outdoors, we should pay more attention to indoor air quality. Air purifiers are the normal choice when people face the bad air. But the air purifiers in the market cannot work with the window open, which lead us to live in a closed environment. With the time goes on, the air in a closed room could be clean but not fresh. People wouldn’t feel very well, either.

In order to prevent the particles from entering into our room and provide fresh new air for our room, we should remove them in the ventilation process, and our solution is to create a new purifier which can be installed with the windows through the wall, just like a “mask” of a house. This new device could reach two goals: remove the particles at one time, induce a continuous gas flow in the ventilation process.

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There are two ways of the particle removing: mechanical filter and ESP (electrostatic precipitation)[3, 4]. The mechanical filter has a big wind resistance to the gas which would cause a big cost of energy if we use it in the ventilation process. And we must exchange the filter quite often because its life is only about one year or two. It is said that the effective filter is a bit expensive. The ESP has a good efficiency to the small particles and small pressure lost to the gas flow[5]. So this way is better to choose. But common ESP are usually too big to be installed with the window. We must improve the structure and change the dimension of the device until it is suitable for a window.

The average wind velocity outside is often below 2.3 m/s, due to that there isn’t enough ventilation power for a normal room to get enough fresh air. So we should provide extra power to complete the ventilation process. There are also two ways to provide the gas power: fan and ionic wind generator[6, 7]. Now most air purifiers consist of a mechanical fan. But the fan cost a big energy consumption and a big noise. Also the fan is too big, in a word, it is not very environmentally friendly to be installed in the room. The ionic wind is a new technology to generate the wind, an ionic wind is a gaseous fluid flow

momentum with the neutral particles resulting in net motion. The ionic wind can help remove the dust and it cost a low energy consumption[8, 9]. The structure of a ionic generator is quite thin, the last but not the least, the ionic wind generator can work in silence to provide a gas flow of about 1 m/s.

Based on the analysis above, we raised up the whole scheme: Based on the ESP and the ionic wind, we design a new purifier which can be installed with the window by improving the structure of the ESP and choosing the appropriate parameters of the ionic generator. This device could remove the small particles during the ventilation process and provide enough fresh and clean air for our room.

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1.Principle of the novel air purification

1.1.The scheme of air purification window

The scheme of this device is shown in the Fig. 1. This device consists of the gauze, the electrostatic precipitator, the ionic wind generator and the ozone filter. The gauze could remove the big particles, the small particles could be collected by the electrostatic precipitator, the air flow is driven by the ionic wind produced by the ionic generator on the back, and the ozone filter could catalyze the decomposition of the ozone.

When the air outside is bad, we turn on the switch, the device starts working. The dirty air is driven by the ionic wind, going through the removal part without big particles with the help of the gauze. In the high voltage electrical field of the removal part, the small particles could be charged during the corona discharge, the bacteria would also be killed in the corona process. What’s more, the CH3OH could also be changed to CO2 and H2O.The small particles soon would be collected by the iron plate. Unfortunately, some extra ozone would be generated also, at the last part, the ozone filter based on the !-Al2O3 could catalyze the decomposition of the ozone. Finally, the fresh and clean air could be sent to our room.

Fig. 1.1. The schematic diagram of the decomposition of the device

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1.2. Analyze of the key technology

Providing ventilation power with the help of the ionic wind

An ionic wind is a gaseous fluid flow generated when charged particles (ions) are accelerated through a medium of neutral particles. The ions collide and exchange momentum with the neutral particles resulting in net motion. The structure of the ionic wind generator including wire-to-net and needle-to-net. The wire-to-net structure could provide more area wind in the same volume. So we choose this structure to be a part of our device.

Remove the small particles with the help of ESP

There is a positive corona discharge near a corona wire in the electrostatic precipitator. The small particles could be easily charged in this area. The particles would be collected by the mental plates (the negative electrode) driven by the electrical force in the high voltage electrical field. The structure of the ESP could be classified into two types: transverse plate and vertical plate structure. The vertical plate structure has little wind resistance to the gas flow which is good for ventilation. It is suitable for indoors air purification.

There are a lot of ways of increasing the efficiency of the ESP: Lower the wind velocity, Enlarge the length of the collection plate, Raise the approaching velocity. The ventilation couldn’t be very well if we lower the wind velocity, the volume of the device would be bigger if we choose the second way, so we choose the last way to improving the efficiency of the ESP. We finally choose the double-district- structure as our structure of the ESP, it consists of two district: Charging district and collecting district. The collecting district was made of some mental plates which is parallel to the gas flow. This structure could provide a higher electrical intensity compared with other structure, thus the approaching velocity then turned high, so does the efficiency of the removal.

In a word, our device is made by improving the wire to plate structure. It is shown as Fig. 1.2.

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a

ESP self-ventilating technology

We produced the air with the power source from the ESP, we complete two jobs: ventilation and purification with just one device. We finish the cost saving by this way. There are a lot of other advantages of this combination: the ESP has little wind resistance to the air flow which is good for ventilation, the ionic wind can help charge and remove the small particles. The two technology formed a good combination to raise the efficiency and the ventilation volume.

The way to make corona wire straight

The diameter of the mental wire we used is just 0.3 mm. It can be buckled easily. It is as shown in Fig. 3. It is hard to make it straight with the mechanical way. With the help of some books, we learned that we could let the wire be charged with the electricity in about 12V DC. The wire would turn hot to be easy to be straight. When the wire turned not that hot, it will keep being straight (shown in Fig. 1.3).

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The position accuracy of the corona wire has a big influence to the device. We use PCB plate to fix the corona wire by welding.

2. Theoretical design of the device

Our device is a purification window, and the major part of our product is the ESP part and the Ionic wind part. The thickness of our device is an important parameter. We should have a good design to make sure that the voltage of the ESP part and the Ionic Wind part is equal, at the same time we should make sure the efficiency is reliable and lower the thickness of our device.

2.1. Parameter design

Air flow rate

The air flow rate is an important parameter of the indoor air purification device. According to the national indoor air quality standard GB/T18883-2002(China). The flow rate would be above 30 m3/(h·person). We make a consumption: a room 3 persons, the device works 15h a day. So the total result could be calculated equals 2160 m3. The flow rate is 144 m3/h.

The removal efficiency

The efficiency of the ESP has a positive relation with the energy we put in[10]. So the efficiency depends on what we need. According to

the research, the PM2.5 is the major pollution in the haze weather, according to the environment air quality standard (China) GB30952012, the average mass concentration of the PM2.5 in a day is below 35wg/m3, In 2013, the average mass concentration in a day of the PM2.5 in the highly polluted city Beijing is 646wg/m3, so we should make sure that the removal rate of the device is above 94.58%, we choose the number of 95 %.

The wind velocity

According to the text above, we know that the air flow rate is 144 m3/h, according to the formula Q = V×S, the velocity of the air

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