WO2016068812A1

WO2016068812A1 - By-pass for controlled water potential conversion in a limited space

Info

Publication number: WO2016068812A1
Application number: PCT/SI2014/000066
Authority: WO
Inventors: Janez GALE; Primož BREJC
Original assignee: Zel-En D.O.O.
Priority date: 2014-10-30
Filing date: 2014-11-12
Publication date: 2016-05-06
Also published as: SI24884A

Abstract

The subject of the invention is by-pass for controlled water potential conversion in a limited space which ensures safe and stable operation of high-pressure hydroelectric power plants with supply piping and solves the technical problems arising during a sudden shutdown of the hydroelectric power plant due to blackout or other causes for sudden shutdown. The inlet (1) connects the water turbine (1) at the point of spiral casing to the valve (2), which is opened and closed by the valve drive (3) comprising the oil servomotor (11) and water servomotor (12). The water servomotor (12) forces the valve to open. The oil servomotor (11) holds the valve (2) in the closed position. In the event of oil pressure drop in the oil servomotor (11) as a result of blackout or failure of the hydraulic power unit, the water servomotor (12) opens the valve (2) for safety reasons. During the shutdown of the water turbine (10), the valve synchronisation with the turbine guide vanes (4) through the valve drive (3) enables the opening of the valve (2), whereby the total water flow through the water turbine (10) and valve (2) remains the same during the closing of the guide blades. When the shutdown of the water turbine (10) is completed, the valve (2) slowly closes, causing only small pressure changes in the pipeline, or the by-pass for controlled water potential conversion in a limited space switches into continuous operation. The chamber (8) converts kinetic energy into potential energy. The conversion of energy takes place in a closed, limited and controlled space, filled with water.

Description

BY-PASS FOR CONTROLLED WATER POTENTIAL CONVERSION IN A LIMITED

SPACE

DESCRIPTION OF INVENTION

Field of Technology

Water turbines; turbine trip; hydraulic shock; cavitation; erosion of river bed; valve synchronisation with guide vanes; dissipation chamber; orifice.

Technical Problem

Water turbine trip results in partial runaway and high-pressure water hammer, which could damage individual parts of the water turbine and supply pipeline. One of the modern safety solutions is that water is suddenly redirected past the water turbine; however, due to the large amount of energy released, a sudden discharge of water flow presents a danger to the environment, any water activities and people, and, in particular, it may damage or erode the river banks or uncontrollably change the shape of the river bed. Uncontrolled discharge or abrupt stop of water flow causes loading, damage, vibrations and noise in the turbine installation. In addition, free (non-)operation of water turbine, which is adapted to electricity consumption, endangers the river ecosystem and biological minimum in the river.

State of the Art

Water turbines are always designed in such a manner that they can take over the loads resulting from trips. For this purpose, turbines and other supporting systems are appropriately (over)dimensioned, and a number of safety components, such as a surge tank, a high-pressure pipeline, air valves etc. are included. By-pass for controlled water potential conversion in a limited space is a modern safety solution that replaces several other systems and at the same time expands the applicability and acceptability of water turbine in the natural environment. Several related solutions which include individual components of the suggested by-pass are known; however, none of the solutions known to date solve the problem of energy dissipation in such a comprehensive, efficient, compact, controlled and economical way. The advantage of the suggested by-pass is the selection and appropriate connection of various components into a single optimal system that enables very flexible operation and is easy to maintain and construct, and is beneficial for investments.

Description of new invention

The subject of the invention is by-pass for controlled water potential conversion in a limited space which ensures safe and stable operation of high-pressure hydroelectric power plants with supply piping and solves the technical problems arising during a sudden shutdown of the hydroelectric power plant due to blackout or other causes for sudden shutdown.

The main technical problems arising from turbine trip are:

loading of bearings and slipping of runner blades as a result of increased turbine speed or turbine overspeed;

- Water hummer travelling upstream in the pipeline, which can damage the pipeline, resulting from the abrupt stop of water flow, when the guide blades are closed;

- ensuring a biological minimum of the river flow as a result of interrupted flow of water to the river.

The subject of the invention solves the technical problems with a comprehensive solution which includes the synchronisation of the outlet valve with turbine guide blades, multifunctional operation and controlled water potential conversion in a limited space with reduced vibrations and noise.

The technical solution of the invention is the layout of components and their connection in such a way that the system can be easily adapted to various input pressure and flow parameters, while at the same time ensuring a compact structure which is easy to construct and maintain. The subject of the invention may be used for a short period during a sudden shutdown of hydroelectric power plant or for a longer period to adjust/ensure the required river flow. Turbine high-pressure by-pass for controlled water potential conversion in a limited space is the hydroelectric power plant's safety system, w hich replaces the traditional and established safety components, systems and measures (surge tank, pressure pipeline, design based on turbine etc.). It functions by redirecting the water flow into the by-pass for controlled water potential conversion in a limited space through the special valve 2 when the emergency shutdown of the water turbine 10 is activated. The water flow coming through this by-pass retains all the kinetic energy, which is then transformed into potential energy in a special limited space (dissipation chamber 8) in a controlled manner. Turbine high-pressure by-pass for controlled conversion of kinetic energy in a limited space is used to mitigate transients (water hammer) when the turbine is shut down immediately/suddenly.

The invention solves the problems of proper selection of components in an integrated way. By-pass for controlled water potential conversion in a limited space is composed of several components which are dimensionally adapted with respect to the inlet parameters (drop, flow rate, required speed for start-up and shutdown) and turbine arrangement (horizontal, vertical).

The first component is the inlet 1 or supply piping that connects the water turbine 10 at the point of spiral casing to the valve 2. The valve 2 is dimensioned and designed in such a manner that it prevents losses during the operation of the water turbine 10 and that during the operation of by-pass for controlled water potential conversion in a limited space, the path of water from the water turbine 10 to the valve 2 is as short as possible (compact construction).

The valve 2 ensures that:

the water flow which ' runs through the water turbine 10 is collected in full, at any time and instantly, from zero flow to full flow;

- the impact of increased pressured during a sudden shutdown of hydroelectric power plant is reduced;

sealing is provided during non-operation;

constant flow during operation is maintained;

long-term operation without cavitation is secured; and

loading and flow change during operation. The valve 2 is designed and constructed in such a manner that it controls cavitation and erosion, while its operation is unconditional.

The valve 2 is opened and closed by the valve drive 3 comprising the oil servomotor 11 and water servomotor 12. The water servomotor 12 is directly linked with the water pressure in the pipeline in front of the water turbine 10 and forces the valve to open. The oil servomotor 11 holds the valve 2 in the closed position and operates in the opposite direction of the water servomotor 12. In the event of oil pressure drop in the oil servomotor 11 as a result of blackout or failure of the hydraulic power unit, the water servomotor 12 opens the valve 2 for safety reasons.

Valve synchronisation with turbine guide vanes 4 is essential for the correct functioning of the invention. During the shutdown of the water turbine 10, the valve synchronisation with the turbine guide vanes 4 through the valve drive 3 enables the opening of the valve 2, whereby the total water flow through the water turbine 10 and valve 2 remains the same during the closing of the guide vanes. When the shutdown of the water turbine 10 is completed, the valve 2 slowly closes, causing only small pressure changes in the pipeline, or the by-pass for controlled water potential conversion in a limited space switches into continuous operation. During the start-up of the water turbine 10, the valve 2 closes synchronous with the opening of guide vanes of the water turbine 10, and the procedure is reversed.

As a result of high pressures in front of the valve 2, the flow rates in the valve are extremely high, which causes local pressure drops and the associated cavitation. By adding air with the dispenser 5 at the point of local pressure drop behind the valve 2, the pressure is increased if necessary. Air bubbles have the effect of a spring, thus preventing further local pressure drops that could result in cavitation. Air is added through the natural draft dispenser 5 which supplies air around the flow perimeter. The quantity of air depends on the pressure or vacuum in the piping, and it can also be limited.

The connection 6 is a short piping that connects the dispenser 5 to the orifice 7. The shape of connection 6 depends on the installation and orientation of the complete inventions, the type of water turbine 10 and, in particular, the chamber 8. Thus, the connection 6 may represent the straight section of the piping or adjusting elbow.

The orifice 7 is a component of great importance and performs the following functions:

it increases the pressure behind the valve 2 and consequently prevents cavitation in the valve 2:

it prepares a symmetric, concentrated and directed flow at the inlet to the chamber 8.

The orifice 7 is installed at the inlet to the chamber 8 in such a manner that its outlet flows directly to the chamber 8. The shape of the orifice 7 depends on the inlet parameters.

The chamber 8 is also an important component of the invention and is used to convert kinetic energy into potential energy (hydraulic jump) through turbulence. Its special feature is that the conversion of energy takes place in a closed, limited and controlled space, filled with water. The size of the chamber is defined in detail for each individual case, since the conversion of energy takes place in the volume of water, which must be large enough to ensure that the inlet flow from the orifice 7 does not touch the walls. Inlet flow could cause vibrations, erosion and damage to the material on the walls. The amount of converted kinetic energy in the chamber 8 is such that the flow rate at the outlet 9 does not damage the river bed. All the turbulence caused by the conversion of kinetic into potential energy is also converted in the chamber 8.

The outlet 9 is the connection between the outlet of the chamber 8 and the river or, depending on the construction, it can also connect the chamber 9 to the existing lower channel which connects the turbine suctions pipe with the river. The outlet 9 is designed in such a manner that the slow flow coming from the chamber 8 is evacuated into the river by the shortest route.

The essence of the invention is further explained below with the description of the embodiment and attached figure, whereby the figure is part of this patent application and shows the following: Figure 1 shows an inlet 1 , a valve 2, a valve drive 3, valve synchronisation with turbine guide vanes 4, a dispenser 5, a connection 6, an orifice 7, a chamber 8, an outlet 9, a water turbine 10, an oil servomotor 11 and a water servomotor 12.

The by-pass for controlled water potential conversion in a limited space is composed of several components which are dimensionally adapted with respect to the inlet parameters and turbine arrangement.

The first component is the inlet 1 that connects the water turbine 10 at the point of spiral casing to the valve 2. The valve 2 is dimensioned and constructed in such a manner that the path of water from the water turbine 10 to the valve 2 is as short as possible and that it controls cavitation and erosion, while its operation is unconditional.

During the shutdown of the water turbine 10, the valve synchronisation with the turbine guide vanes 4 through the valve drive 3 enables the opening of the valve 2, whereby the total water flow through the water turbine 10 and valve 2 remains the same during the closing of the guide vanes. When the shutdown of the water turbine 10 is completed, the valve 2 slowly closes, causing only small pressure changes in the pipeline, or the by-pass for controlled water potential conversion in a limited space switches into continuous operation. During the start-up of the water turbine 10, the valve 2 closes synchronous with the opening of guide vanes of the water turbine 10, and the procedure is reversed.

By adding air with the dispenser 5 at the point of local pressure drop behind the valve 2, the pressure is increased, which prevents excessive pressure drops and the associated cavitation. Air is added through the natural draft dispenser 5 which supplies air around the flow perimeter. The quantity of air depends on the pressure or vacuum in the piping.

The connection 6 is a short straight section of the piping that connects the dispenser 5 to the orifice 7. The orifice 7 is installed at the inlet to the chamber 8 in such a manner that its outlet flows directly to the chamber 8.

The chamber 8 converts kinetic energy into potential energy through turbulence. The amount of converted kinetic energy in the chamber 8 is such that the flow rate at the outlet 9 does not damage the river bed. The outlet 9 is the connection between the outlet of the chamber 8 and the river.

It is self-evident that the above described invention can be also used in other particular form not changing the substance of the invention.

Claims

PATENT CLAIMS

1. The by-pass for controlled water potential conversion in a limited space characterized in that it comprises an inlet (1), a valve (2), a valve drive (3), valve synchronisation with turbine guide blades (4), a dispenser (5), a connection (6), an orifice (7), a chamber (8), an outlet (9), whereby the outlet valve (2) is synchronised with guide blades of the water turbine (10).

2. The invention according to claim 1 characterized in that the valve (2) is opened by the valve drive (3) comprising the oil servomotor (11) and water servomotor (12).

3. The invention according to any claims 1 to 2 characterized in that the water servomotor (12) is directly linked with the water pressure in the pipeline in front of the water turbine (10) and forces the valve (2) to open.

4. The invention according to any claims 1 to 3 characterized in that the oil servomotor (11) holds the valve (2) in the closed position and operates in the opposite direction of the water servomotor (12).

5. The invention according to any claims 1 to 4 characterized in that in the event of oil pressure drop in the oil servomotor (11) as a result of blackout or failure of the hydraulic power unit, the water servomotor (12) opens the valve (2) for safety reasons.

6. The invention according to any claims 1 to 5 characterized in that the water flow is redirected into the by-pass for controlled water potential conversion in a limited space through the valve (2) when the emergency shutdown of the water turbine (10) is activated.

7. The invention according to any claims 1 to 6 characterized in that during the shutdown of the water turbine (10), the valve synchronisation with the turbine guide vanes (4) through the valve drive (3) enables the opening of the valve (2), whereby the total water flow through the water turbine (10) and valve (2) remains the same during the closing of the guide vanes.

8. The invention according to any claims 1 to 7 characterized in that when the shutdown of the water turbine (10) is completed, the valve (2) slowly closes, causing only small pressure changes in the pipeline.

9. The invention according to any claims 1 to 7 characterized in that when the shutdown of the water turbine (10) is completed, the valve (2) ensures a continuous operation of the bypass for controlled water potential conversion in a limited space.

10. The invention according to any claims 1 to 9 characterized in that air is added with the natural draft dispenser (5) at the point of local pressure drop behind the valve (2) to prevent cavitation.

11. The invention according to any claims 1 to 10 characterized in that the conversion of energy takes place in the chamber (8), i.e. in a limited and controlled space, filled with water.

12. The invention according to any claims 1 to 11 characterized in that the orifice (7) is installed between the connection (6) and the chamber (8), which increases the pressure behind the valve (2) and consequently prevents cavitation in the valve (2).

13. The invention according to any claims 1 to 12 characterized in that the orifice (7) is installed between the connection (6) and the chamber (8), which prepares a symmetric, concentrated and directed flow at the inlet to the chamber (8).

14. The invention according to any claims 1 to 13 characterized in that the orifice (7) is installed at the inlet to the chamber (8) in such a manner that its outlet flows directly to the chamber (8).