EA036765B1 - Water aeration system for hydraulic turbines - Google Patents

Abstract

The invention relates to a water aeration system for hydraulic turbines integrable with hydraulic turbine draft tube cones to increase the dissolved oxygen level of water discharged from hydro power plants. Water aeration system for hydraulic turbines according to the invention is a system comprising a water aerating device that aerates via perforated plates, which replicate, together with a support grid, the internal geometry of the original draft tube cone of the turbine, by means of orifices calibrated to the void fraction required to aerate the flow in the turbine. The air injection in the turbine is based on the turbine pressure level and the deficiency in dissolved oxygen level in the water, readings of which actuate the aeration process control module, minimising the energy consumption required for aeration, either activating natural aeration, with no associated power consumption, or forced aeration fed by compressed air.

Description

The present invention relates to an aeration system for use on hydraulic turbines incorporated into a draft tube cone to increase the dissolved oxygen (DOL) content of the water leaving the hydraulic turbine.

It is well known that hydroelectric power plants (HPPs) directly or indirectly affect the flora, fauna and even the microclimate in their places of residence. However, hydroelectric power plants are the main source of renewable energy, obtained by an environmentally friendly method, since, when properly used, the generated energy does not pollute the environment. To preserve the sustainable properties of hydropower, appropriate measures must be taken to limit the environmental impact of power plants. One of the main concerns of environmental authorities is the quality of water discharged through turbines into rivers, especially when the DOL (Dissolved Oxygen Content) is low, which can have a negative impact on the environment and even endanger the life of aquatic organisms. Hydroelectric power plants are the main source of clean energy, while operators and manufacturers of hydraulic equipment consider the environmental impact of turbine operation and take measures to mitigate their impact. The main goal is the quality of the discharged water in relation to the DOL. The application of environmentally sound standards in all countries is essential for the development of hydraulic engineering. For the sustainable development of hydropower plants, the deterioration of the ecological state of waterways is unacceptable. The high-level dam's intake is located in the deepest layer of the reservoir, at a depth where the DOL is minimal. When water flows through the turbine, the DOL drops again due to the pressure drop.

The main goal of the European Water Policy is to achieve a good status for all soil and ground waters in the EU countries and related territories, as well as to achieve a good ecological potential for substantially modified and artificial waters.

Low DOL in rivers is a pollution factor. In some cases, the DOL is reduced to 0-2 mg / L, given that the minimum DOL required for the existence of aquatic life is approximately 6 mg / L. It is emphasized that this value varies depending on the temperature and / or the prevailing climate of the HPP, organic matter in reservoirs, the depth of water intake (the lower the water intake, the lower the DOL), the type and mode of operation of the HPP, the pressure level in the turbine (especially for Francis turbines, operating at partial load). Low DOL occurs when the following conditions are met:

the depth of the reservoir is more than 15 m;

the volume of the reservoir is more than 6-10 ⁷ m ³ ;

the generated power is more than 10 MW;

the rate of water exchange in the reservoir is more than 10 days.

There are several solutions to be implemented during retrofitting of hydraulic turbines in order to increase DOL in the river downstream of the HPP. The usual methods for increasing DOL are carefully selected from the following:

water intakes, dams, weirs, pumps, diffusers, compressors;

deflectors on impeller housings and suction tubes (for example, removable deflectors installed in turbines create low pressure areas and direct air to channels downstream of the hydroelectric power plant).

These methods have been used at hydropower plants with varying degrees of success in achieving aeration. Vortex aeration is considered the most cost effective technology to improve DOL. However, aeration, which improves water quality downstream, is still ignored in most existing hydropower plants.

Since 1950, the main energy suppliers and manufacturers of hydroelectric equipment in Europe and the United States have dealt with the environmental aspects of hydroelectricity. Two types of aeration systems were tested at the Tims-Ford dam [Harshharger et al., 1995] with the aim of achieving a DOL of 6 mg / l: one with air injection through a turbine and one with oxygen injection through porous rubber pipes into a 250 m long pressure water conduit and 6.7 m in diameter. Air blowers injected air either under the impeller or under the suction pipe. The auxiliary system was designed to be used when DOL could only be achieved with blowers. For DOL upstream, a maximum of 1 mg / L, when both aeration systems were in operation, DOL reached 5.2 mg / L, and if only the air system was in operation, DOL increased to 4.2 mg / L. Both systems were tested for 52 weeks with varying flow rates of water, air and oxygen, and measurements were taken to monitor the increase in DOL and turbine efficiency. In each case, the data showed a slight decrease in turbine efficiency of about 1%, but the target DOL (6 mg / L) was not achieved.

First, at the Bull Shoals power plant, USA [Harshbarger et al., 1999] equipped with Francis turbines, deflectors have been installed on the impeller since 1991. The baffles were positioned to optimize pressure relief to maintain a minimum DOL of 4 mg / L downstream. Second, at Table Rock, a deflector ring was installed at the periphery of the impeller, and the diameter of the existing holes was increased from 2.5 to 3.75 cm. In addition, the vacuum bursting system was modified to accommodate more air. In the first case, the DOL increased by 2-3 mg / L when one turbine was operating and by 1-2 mg / L when all turbines were operating. Also, the power generated by the station decreased by

1.3-3%. In the second case, DOL increased by 2.5-3 mg / L during the operation of one unit and by 2-2.5 mg / L during the operation of both units.

Studies and measurements of the effect of aeration on turbine power and mechanical properties were performed at the Deer Creek reservoir (Wahl et al., 1994) to provide data for the design of a permanent aeration system. In the summer months, the DOL in the waste water from the HPP decreased to 0-2 mg / l, which negatively affected the life of aquatic organisms in the range of 3-5 km. The new aeration system aims to increase the DOL to 3.5 mg / l. Air was injected into the suction pipe through the existing passages (vacuum breaker and twin turbine nozzles) using two compressors, so that the air was mixed with the turbine water, thus increasing the DOL.

For an air flow less than or equal to 4% (φ <4%) of the turbine water flow, the aeration efficiency increased by about 10% with each additional percentage of the air flow. With open guide vanes in the 55 to 77% range, it was found that the reduction in energy efficiency due to aeration was 0.5% for φ = 1%. In the end, the existing aeration system was closed due to the high maintenance costs of electrical equipment. However, it was concluded that each of the alternatives would give better results by introducing relatively high flow air into the turbine under various operating conditions.

Other studies [March et al., 1992] aimed to provide up to 6 mg / L DOL in downstream water, minimizing the impact of aeration on energy efficiency and hydropower capacity. A number of alternatives have been tested, including air injection through an impeller or modified deflector, trailing edges of turbine blades, a coaxial diffuser, an exhaust ring, a suction tube, or a combination of the above.

The Tennessee Valley Administration proposed a modernization program in which several turbines were replaced or improved to address the DOL problem downstream of the plant. A hydraulic and environmental performance analysis was performed to select the most suitable turbine aeration system for the specific site. Self-ventilated turbines (SVT) were first introduced at the Norris Dam along with three main types of aeration: central, distributed and peripheral aeration (at the outlet of the turbine impeller blades). Measurements were made to assess the environmental impact and energy performance. Each option (whether used alone or in combination with others) has been tested over a wide range of turbine operating conditions. For one group, an increase in DOL to 5.5 mg / L was achieved using all aeration options. In this case, the amount of air entering the turbine was more than twice that of the original turbine equipped with deflectors on the impeller. Depending on the operating conditions and the aeration option, energy efficiency decreased from 0 to 4%. The efficiency of self-ventilated turbines is analyzed and compared in the literature [Rohland, 2010], where the main aeration parameters are given: turbine geometry, air volume, air injection location [Papillon et al., 2002], [Sullivan & Bennett, 2006], etc. In these studies, the size and distribution of air bubbles are not particularly considered, although they are mentioned. Research and search continues to mathematically model SVT streams Each method has different characteristics and affects the size and distribution of bubbles flowing through the suction tubes under different operating conditions [Perkinsin et al., 2013], [His et al., 2006].

Research on aeration systems for waste water from turbines continues, given their importance for ecosystems [Bunea et al., 2010 and 2014] and water quality standards. Hydroelectric operators are trying to achieve the optimal relationship between measures to improve water quality and energy efficiency.

Other well-known patented technical solutions:

EP 2873851 A1, in which aeration is carried out by deflectors / hydraulic wings located on the turbine impeller blades;

US 6854958 B2, in which aeration is carried out through a special chamber located around the impeller belt in the stationary part of the turbine. Air inlet is provided through several parts of the turbine: at the inlet of the impeller, between the guide vane and the impeller, and at the outlet of the impeller between the impeller belt and the cone of the suction pipe through slots located around the circumference of the impeller;

US 6247893 B3, in which aeration is provided by means of impeller blades on the outside of the guide. This solution is suitable for Francis and Kaplan turbines;

US 941628 A, in which an adjustable circular groove is made at the outlet of the impeller in the upper part of the suction pipe. The injection is carried out through the slot.

US 5823740 A, in which a mixture of air and water is injected upstream and downstream of the turbine impeller. Water is drawn in from the high pressure side through impeller channels or labyrinths, and air is injected into mixing chambers located in fixed parts around the belt or impeller cover;

- 2 036765

US 5780935 A, in which the impeller is located and elongated so that its edge crosses the free surface of the water, and thus mixing with atmospheric air.

The disadvantages of the known solutions are as follows.

All of these patents relate to the aeration of water flowing through hydraulic turbines. The aeration methods and their implementation differ from the solution proposed in this document. All patented aeration methods involve modification of impellers or parts in close proximity to it, and do not involve the injection of calibrated small bubbles. While most of the techniques presented are not related to equipment integrity, their application to existing turbines will involve major changes to existing designs and therefore can only be used in new machines or those that are subject to major repairs. An advantage of the proposed technique is that it can be implemented during normal maintenance periods, including the integration of the aeration device into the turbine suction cone. The total cost of installing the new aeration device is clearly less than other patented methods, and the aeration itself can be performed without energy consumption when the pressure inside the suction cone is below atmospheric, otherwise forced aeration is initiated.

Known solutions for aeration of waste water are focused on the amount of introduced air and do not take into account the surface area of the air-water phase interface and the contact time between phases. The efficiency of aeration at a hydroelectric power station is usually expressed in the fraction of voids (equation 1):

In general, to increase the DOL by 1 mg / L, an amount of air is required that is 1% of the volume of water. Conversely, to limit the reduction in energy efficiency, the air flow should not exceed 3-5% of the turbine water flow (Equation 2):

1ph _{= <3} _ _50/0) ( ₂ )

Qivater where Q _air and Q _water are air flow and water flow, respectively.

However, the introduction of air into the hydraulic circuit of the turbine reduces the efficiency of the turbine. Limiting the amount of injected air means that this may not be enough to achieve the desired DOL, especially when the initial DOL in the water is <2-3 mg / l. This is an important issue for manufacturers and operators of hydraulic turbines, as the injection of additional air into the turbine circuit reduces efficiency; therefore, air injection parameters (method, injection site, quantity, etc.) are important in balancing turbine efficiency with environmental factors.

Another disadvantage of most known aeration methods is that they change the design of the equipment, which leads to a change in flow characteristics and, therefore, a decrease in efficiency, even when the aeration system is not in use.

Another disadvantage of the known aeration methods is the high amount of energy required for injection.

Another disadvantage of the patented aeration methods is the need to modify the impellers or distributors: complex operations on existing turbines, accompanied by high costs for new or refurbished turbines.

A technical advantage of the present invention is to provide an aeration system that increases the DOL of the turbine discharge water, which requires natural aeration (NA) when the suction cone pressure is below atmospheric, or forced aeration (FA) provided by compressors when the suction cone pressure is higher or equal to atmospheric pressure. Air injection from the device into the turbine hydraulic circuit is carried out through perforated plates, which, together with the support grid, duplicate the internal geometry of the original draft tube cone. The holes are characterized by a diameter of 0.2 to 5 mm and are spaced at the same distance in steps of 3 to 7 diameters to avoid coalescence of bubbles depending on the fraction of voids in the flow. The injection is dependent on the downstream pressure of the impeller and insufficient water DOL and is triggered by the control module. The goal is to minimize energy consumption for aeration by choosing between NA or FA.

The water aeration system for hydraulic turbines according to the present invention overcomes the aforementioned drawback as follows: in order to increase the DOL of water downstream of the turbine, the water aeration device duplicates the flow in the cone of the suction pipe. It consists of an air chamber with an inner wall formed by perforated plates, which are fixed to a support grid and completely or partially enclose the inner wall. Thus, the flow in the suction pipe does not change due to disturbances, and the hydraulic characteristics of the turbine are preserved after the installation of the aeration device: the use of NA or FA depends on the operating mode of the turbine.

- 3 036765

The advantages of the present invention are as follows.

The injected air is dispersed in the form of small bubbles to increase the surface area and air-water contact time. To increase aeration, other parameters are also taken into account: the distribution of the size of air bubbles in the water, the pressure gradient in the cone of the suction pipe, the pressure drop across the aeration device, the operating mode of the turbine, insufficient DOL value in the water.

An increase in DOL in the water used by the hydroelectric power station may be required to meet the water quality standards set by European / global environmental regulations. To achieve the largest possible interphase contact area, the air in the turbine is dissipated through small holes in the wall of the turbine exhaust pipe. The distance between the holes and their number are determined so that the amount of injected air is in accordance with equation (2) and the requirements of the HPP operators. The contact time is increased, and small air bubbles are moved by the flow of water compared to air pockets, which tend to exit the hydraulic circuit in a shorter time.

The aeration device according to the present invention corresponds to the existing internal geometry of the cones of the turbine suction tubes, where it is implemented, with air being introduced without pressure.

The system can be used with both new and existing turbines, as it requires the installation of an aeration device in the turbine exhaust cone, which can be done during the turbine maintenance period. The compressed air connection and the aeration control module are easily attached to the aeration unit.

The system minimizes the impact on turbine performance, and when the system is not in use, the turbine performance is not affected, while other known aeration systems substantially reduce turbine efficiency, as shown in the prior art.

Another parameter that has been considered is the energy consumption associated with injection to maintain the overall performance of the HPP. Accordingly, the air injection method and the use of fine bubbles minimize the impact on flow patterns depending on the injected air flow rate (controlled by valves and pneumatic system).

The system can use NA without the additional power consumption associated with FA.

The following describes an example of a water aeration system for hydraulic turbines according to the present invention, shown with reference to FIG. 1-12, on which:

in fig. 1 shows a water aeration system for hydraulic turbines in section A-A;

in fig. 2 shows an isometric view of section A-A;

in fig. 3 shows a three-dimensional view of a water aeration system for hydraulic turbines according to the present invention;

in fig. 4 is a top view of a water aeration system for hydraulic turbines according to the present invention;

in fig. 5 is a bottom view of a water aeration system for hydraulic turbines according to the present invention;

in fig. 6 shows an air chamber and an atmospheric air inlet pipe in section F-F;

in fig. 7 shows the appearance of the air box and the location of the air inlet valves for NA and FA;

in fig. 8 shows a view of a perforated plate;

in fig. 8a is a fragmentary view A according to FIG. 8;

in fig. 8b shows a three-dimensional view of a perforated plate;

in fig. 9 shows a water aeration system;

in fig. 10 is a schematic illustration of a pneumatic connection assembly for supplying compressed air to a water aeration system;

in fig. 11 shows a demo model;

in fig. 12 shows photographs of the injection area of the water aeration device for the operation of the Turbine at Qwater relative = 57.1% and φ = 1%;

in fig. 12a shows the perforated plates before air injection;

in fig. 12b shows the perforated plates at the start of air injection;

in fig. 12c shows the perforated plates during air injection;

in fig. 13 shows the variation in efficiency of a turbine generator as a function of the void fraction provided by injection through a water aeration system for hydraulic turbines according to the present invention for various partial load (B-F) modes.

According to the present invention, a water aeration system for hydraulic turbines is built into the cone of the suction pipe, precisely following the internal geometry of the suction pipe.

The water aeration system comprises a water aeration device equipped with valves for supplying air at atmospheric pressure for NA;

complete pneumatic connection for compressed air supply for FA;

- 4 036765 automatic control module for the aeration process.

The water aeration device according to the present invention consists of an air chamber (AC) with an inner wall formed by perforated plates 1 through which air is injected, which are mounted on a support grid 2 and completely or partially cover the inner wall, which is in contact with the water discharged from the turbine. Perforated plates 1 are made of stainless steel and perforated with holes with a diameter of 0.2-5 mm, which are located at a distance of 3-5 diameters from each other, taking into account the fact that the proportion of voids φ <35%. The air chamber AC is also delimited by an upper wall 3, a lower wall 4 and an outer wall 5, on which air inlet pipes 6 for NA are arranged at an equal distance from each other. The inlet pipes are equipped with valves 7 to control the air flow passing at atmospheric pressure. The other air injection pipes 8 are equidistant from and alternating with the air inlet pipes 6 through which the FA flows to control the air flow using a pneumatic connection assembly for supplying compressed air. The AC air chamber also contains a drain plug 9 for draining the water entering from the turbine hydraulic circuit into the air chamber due to pressure fluctuations at an unstable flow rate. On the air inlet pipes 6, flat flanges 10 are located externally, which engage with the valve flanges 11. The connections of the flat flange 10, flange 11 of the valve and gasket 12 are fixed using bolts 13 with a hex head, a hex nut 14, washer A 15 and washer R 16 Grover. The air injection pipe 8 is equipped with an adapter 17, which is connected to the compressed air supply system. The air chamber AC continues with an upper section 18 and a lower section 19, which are connected to the cone of the turbine suction pipe, on which the water aeration device is installed by means of an upper flange 20 and a lower flange 21, as well as nuts and bolts not shown.

The aeration system operates according to two parameters: the relative pressure level in the suction pipe cone upstream of the air injection section and the DOL value downstream. Thus, the aeration device uses a pressure tap (not shown) and a measuring transducer that measures the pressure on the wall of the suction pipe cone upstream of the aeration device, and downstream of the turbine outlet, a DOL sensor (not shown) is also located. ...

The automatic control module for the aeration system operates as follows: it activates NA if the pressure in the suction cone is below atmospheric pressure and FA if the pressure is greater than or equal to atmospheric pressure. It contains a programmable controller (PC) that receives data from a pressure transmitter of the aeration device, an atmospheric pressure transmitter and a downstream DOL transmitter, and initiates the closing or opening (partial or full) of the air valve, and controls the air flow. which is supplied by the compressor.

To minimize the energy required for oxygenation, the following parameters are required for PC programming:

DOL start limit / end limit;

turbine water flow from the turbine control system;

total air intake area;

pressure drop across perforated plates;

maximum / minimum void fraction limits, hysteresis and maximum aspect ratio.

In addition, the following parameters are monitored (average values for the period of operation): turbine water flow from the HPP control system;

injection air flow.

The program calculates the air flow rate to be taken from the atmosphere at NA using relation (3)

Irj __ s, J I Pa ~ P curbing I, | PaSt ~ P curbing I / ->.

Chmg ^- ^ tca I „„ „, at Patr Patm Pturbine

If the calculated air flow is insufficient to obtain a void fraction within the limits given in equation (2), the valves are closed and the required air flow is supplied by the compressed air supply at FA

Data can be transferred by radio, GPRS / 3G or cable.

The pneumatic connection assembly for the supply of compressed air, which is controlled by the FA, is shown in Fig.10 and contains BV1, BV2 - air cut-off valves, BV3 - drain valve, PR1 - pressure filter regulator, F1 - rotameter, R1, R2, R3, R4 - connections aeration sections, D1 - distributor, TP1 - pressure measuring transducer.

The system can be controlled manually or automatically. In manual mode, parameters are entered and the system operates accordingly. In automatic mode, the aeration system according to the present invention works only if the DOL in the downstream water is below 6 mg / cm ² , the value according to the water quality standard. The system will automatically turn on or off according to the specified cree

- 5 036 765 terium.

Based on the results obtained in the pilot plant, Setup for the study of biphasic, rotational, with adverse pressure gradient, OSIM patent application no. A / 00704/29 09 2015, invention A water aeration system for hydraulic turbines was developed to introduce air into a hydraulic turbine through holes with optimized diameters and geometry to achieve maximum oxygen transfer with minimum energy consumption.

A water aeration system for hydraulic turbines according to the present invention was installed on a Francis turbine at a hydroelectric power station, and the parameters shown in FIG. 13. A slight decrease in the efficiency of the turbine (loss of efficiency up to 2% with a maximum void fraction of 5% adopted by the operator of the HPP) was noted compared to the efficiency when using solutions from the prior art (characterized by a decrease in efficiency to 4%). Moreover, under certain conditions of operation with a partial load of the turbine, the efficiency increased (up to 1.4%). Air injections have also been tested with void ratios greater than 5%, but no significant changes were observed in the efficiency curves, as is the case with the known solutions.

Operating modes of the turbine in which it was tested

List of sources used

Bunea F., Ciocan G.D., Bucur D.M., Dunca G., 2014, Aeration solution of water used by hydraulic turbines to respect the environmental policies, Electrical and Power Engineering, 2014 International Conference and Exposition on, publisher IEEE, p. 1015-1020, DOI: 10.1109 / ICEPE.2014.6970062, ISSN 978-14799-5849-8.

Bunea F., Ciocan G.D., Oprina G., Baran G., 2010, Hydropower impact on water quality, Environmental Engineering and Management Journal, v. 9, No. 11, p. 1459-1464, ISSN 1582-9596.

Harshbarger E.D., Mobley M.H., Brock W.G., 1995, Aeration of hydroturbine discharges at Tims Ford Dam, San Francisco; ASCE, 9 p., Waterpower '95 - Proc. of the Conf. on Hydropower, San Francisco, 1, 11-19.

Harshbarger E.D., Herrold B., Robbins G., Carter J., 1999, Turbine venting for dissolved oxygen improvements at Bull Shoals, Norfork and Table Rock Dams, Waterpower '99 - Hydro's Future: Technology, Markets, and Policy.

March P. A., Brice, T. A., Mobley, M. H, Cybularz, J. M., 1992, Turbines for solving the DO dilemma, Hydro Review; 11 (1), U.S., 30-36, ISSN 0884-0385.

Rohland K.M., Foust J.M., Lewis G.D., Sigmon J.C., 2010, Aerating Turbines for Duke Energy's New Bridgewater Powerhouse, Hydro Review, 29, No.3, p. 58-64.

Perkinsin A., Dixon D., Dham R., Fous J., 2013, Development Status of the Alden Fish-Friendly Turbine, March, Hydro Review - the Magazine of the North American Hydroelectric Industry, p. 46-55.

Sale M.J., Cada G.F., Dauble D.D., 2006, Historical Perspective on the US Department of Energy's Hydropower Program, Proceeding of Hydro Vision International, HCI Publication, Kansas City.

Sullivan A., Bennet K., 2006, Retrofit Aeration System (RAS) for Francis Turbine, Final Report, Ameren UE and MEC Water Resources Inc., contract FC36-02ID14408, US.

Wahl T.L. and Young, D., 1995, Dissolved oxygen enhancement on the Provo River, Waterpower '95, Proc, Int. Conf. on Hydropower, ASCE, San Francisco.

Wahl T.L., 1994, Aerating Powerplant Flows to Improve Water Quality, Currents - Transferring Information on Water Technology and Environmental Research, Research and Laboratory Services Division, Bureau of Reclamation.

Wahl T.L., Miller, J. and Young, D., 1994, Testing turbine aeration for dissolved oxygen enhancement, Fundamentals and Advancements in Hydraulic Measurements and Experimentation, ASCE Symp., New York.

Patents:

Bunea F., Ciocan G.D., Test bench for study of rotational biphasic flow study with adverse pressure gradient, (in romanian: Stand pentru studiul curgerilor bifazice, rotationale, cu gradient advers de presiune),

- 6 036765

Patent application registration, OSIM no. A / 00704 / 09.29.2015.

Cybularz J.M., Fisher R.K., Franke G.F., Grubb R.G., Dissolved gas augmentation with mixing chambers,

Patent No. 5823740, US 005823740 A.

Cybularz J.M., Steele R.D., Scott I.E., Fisher R.K., Draft tube peripheral plenum, Patent No. 5941682,

US 005941682 A.

Kao D.T., Iowa A., Hydropowered turbine system, Patent No. 5780935, US 005780935 A.

Beywem J.R., Fisher R.K., Grubb R.G., Hydraulic turbine for enhancing the level of dissolved gas in water, Patent No. US 6247893, US 006247893 B1,

Desy N., Hydraulic turbine with enhanced dissolved oxygen, Patent No. US 6854958 B2, US 006854958 B2.

Claims (3)

CLAIM 1. A water aeration system for hydraulic turbines, increasing the content of dissolved oxygen (DOL) in the water supplied to the hydraulic turbine, containing a built-in water aeration device corresponding to the internal geometry of the turbine exhaust pipe cone, and the system includes an air chamber (AC) with inner walls, formed from perforated plates (1) attached to the support grid (2) in such a way that they completely or partially cover the inner wall when in contact with water, while (AC) contains an upper wall (3), a lower wall (4) and an outer a wall (5), at which the pipes (6) for air inlet for natural aeration (NA) are located at an equal distance from each other, and the pipes are equipped with valves (7) for regulating the air flow rate; pipes (8) for injection of forced aeration air (FA) into the water flowing through the turbine hydraulic circuit; drain valve (9), provided for the discharge of water entering from the hydraulic circuit of the turbine into the air chamber (AC); and an upper section (18) equipped with a transmitter and a lower section (19), wherein (AC) is attached to the cone of the suction pipe by means of upper (20) and lower flanges (21). 2. A water aeration system for hydraulic turbines according to claim 1, characterized in that the perforated plates (1), which together with the support grid (2) duplicate the internal geometry of the original cone of the suction pipe, contain calibrated holes with a diameter of 0.2-5 mm, located at the same distance from each other, equal to 3-7 diameters, in order to avoid the coalescence of bubbles in the turbine flow, depending on the fraction of voids allowed at the flow rate from the turbine. 3. Water aeration system for hydraulic turbines according to claim 1, characterized in that it is activated by a control module with automatic control of the aeration process to minimize the energy consumed during control (NA) by actuating the valve (7) and (FA) for by using compressed air depending on the pressure differences between the turbine suction pipe and atmospheric pressure, as well as on (DOL) downstream of the turbine.