The use of airlifts in wind turbines. Scheme, description

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The use of airlifts in wind turbines. Encyclopedia of radio electronics and electrical engineering

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Encyclopedia of radio electronics and electrical engineering / Alternative energy sources

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If you plan to use a wind turbine (wind turbine) to lift water, then an airlift can be used as a pump. It is a device that uses compressed air to transport water. Its advantages include the absence of moving parts, the ability to pump out unclarified water, self-regulation when the water level and air supply volume change, reliability and safety in operation. It can be used to lift water from wells, wells and flowing sources.

With a relatively low efficiency of the airlift itself (0,2-0,4), the overall efficiency of the installation is much higher than when using a wind turbine with an electric generator and an uninterruptible power supply.

The design of the pump wind turbine is simple. It consists of repeller, mast, transmission, compressor and airlift. To increase the compressor speed, a V-belt drive with an appropriate gear ratio can be used. For the construction of a small pumping wind turbine, a compressor from a ZIL car or similar is suitable.

Having selected a suitable compressor, an overdrive and a repeller are calculated for its parameters. The performance of the compressor will determine the performance of the airlift. The pressure developed by the compressor will depend on the depth of immersion of the airlift nozzle. To reduce the overdrive gear ratio to 2-3, it is desirable to use a rotary-type repeller with a diameter of up to 1 m. At a wind speed of about 6 m/s, the compressor speed will be about 450 rpm. The corresponding torque is achieved by the height of the repeller rotor. The device of the airlift itself is explained in Fig.1.

Compressed air from compressor 1 is supplied through pipe 2 to nozzle 3 located below the water level. The nozzle holes break the air flow into separate bubbles, which rush up the riser pipe 4. The lighter water-air mixture in pipe 4 is displaced by a column of liquid into the air separator tank 6. When air is continuously supplied to the nozzle 3, the water-air mixture is supplied upwards and water flows to the nozzle along supply pipeline 5. In the air separator 6, the water-air mixture is poured out of the end of the riser pipe 4, and the air enclosed in it escapes into the atmosphere. The immersion depth of the nozzle and the concentration of air in the air-water mixture determine the height of the airlift.

Nomograms for calculating the airlift are shown in Fig.2.

Let's assume that we want to raise water from the well with the help of a compressor with a capacity of V=0,33 m3/min to a height of Hg=7,5 m, while the possible depth of immersion of the nozzle Npf=5 m in our case.

The geometric lift height is calculated from the expression:

H=Ng+Npf=12,5 m.

The value of the relative immersion of the nozzle is determined from the ratio:

αpf=Npf/H=5/12,5=0,4.

It is desirable that this value be in the range of 0,3 ... 0,8.

The pressure that the compressor must develop, taking into account losses in the pipeline, is calculated by the formula:

Pk = (0,11...0,12)Npf = (0,11...0,12)5 = = 0,55...0,6 (kgf/cm2).

According to the nomogram in Fig. 2, a for αpf=0,4 and Npf=5 m, the specific air consumption α=4 is found. Airlift flow Q (m3/h), based on the compressor capacity V (m3/min), is calculated by the formula:

Q=60V/α=60⋅0,33/4=5 м3/ч.

According to the nomogram in Fig. 2b for αpf=0,4 and Q=5 m3/h, the required diameter of the lifting pipe d=50 mm is determined.

The economical speed of the mixture in the riser does not exceed 6...10 m/s. When the mixture moves upward, its speed increases due to the expansion of air bubbles, so the riser pipe at the top has a larger diameter. The transition point from one diameter to another is determined by calculating the velocity along the length of the pipe. With a delivery height of up to 60 m, the transition of the lifting pipe to a larger diameter, as a rule, is not provided.

The nozzle can be made as follows. In the riser pipe, in the place where the nozzle is equipped, five rows of holes are drilled in a checkerboard pattern with a D2 ... 3 mm drill with a step between holes and rows of 15 ... 20 mm. Above and below the holes, two flanges are welded onto the riser pipe. The nozzle area is closed with a piece of large-diameter pipe and scalded along the flanges. A fitting or tube for air supply is welded into the upper flange.

Below the nozzle in the form of an inlet pipe, 0,3 ... 0,6 m of the riser pipe is left.

To prevent oil from entering the water, an oil separator must be installed on the air line after the compressor. It is desirable to paint the airlift, for example, with epoxy glue diluted with a solvent.

Authors: D.A. Duyunov, A.V. Pizhankov

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