WO2003027494A1

WO2003027494A1 - Method and guiding device for increasing a water turbine's efficiency

Info

Publication number: WO2003027494A1
Application number: PCT/NO2002/000348
Authority: WO
Inventors: Jan Tunli
Original assignee: Jan Tunli
Priority date: 2001-09-28
Filing date: 2002-09-30
Publication date: 2003-04-03
Also published as: NO20014742D0; NO20014742L; NO318983B1

Abstract

The invention describes a method and unit that brings water into a centripetal motion in order to establish centrifugal force components. The unit consists of guide walls (4) with an increasing rotation round the unit's axis in order to provide the centripetal motion with a progressively smaller cross sectional area in the longitudinal direction. Between the guide walls are located outer walls, which are at an angle, thus causing the reaction forces against the walls from the centrifugal force to be angled downstream. This centripetal chamber is connected at the rear end to a turbine designed to utilise the reaction forces from the centrifugal force and the kinetic energy in the moment of inertia. The turbine is designed so as to angle a mass flow emerging from the axis of rotation in the centripetal chamber back in the longitudinal direction through the turbine's blades.

Description

05-12-2002

Method and guiding device for increasing a water turbine's efficiency

Introduction

The invention relates to a method and guiding device for increasing a water turbine's efficiency, for example in hydropower production. By bringing a mass flow of water into a centripetal rotational motion through a unit, centrifugal moments of force can be directed in the direction of flow of the unit's special design. The centrifugal force's reaction component in the direction of flow provides a power boost, which increases the angular velocity in the water's moment of inertia about the axis of rotation. The kinetic energy in the rotation and the stored potential energy from the centrifugal force can be utilised for power production.

The unit may be placed on riverbeds, the bottom of channels and tunnels, in underwater areas with a large tidal range and in ocean currents.

The production unit consists of two interconnected parts in addition to the outer hull. The front part of the unit has hollow chambers for water through- flow. This is without rotating parts. At the rear end the unit will be connected to a turbine. In the following text the front unit will be described as a centripetal chamber or chamber.

The design of the centripetal chamber The centripetal chamber has an inlet 2 in front for intake of the flow of water and an outlet 7 at the back for discharge of the water (see Fig. 2).

In its longitudinal direction the chamber will have guide walls 4, which are twisted at a gradually increasing angle per unit of length from inlet to outlet in a gradually decreasing rotational circumference and cross section through the chamber.

The outer wall 8 in the chamber between the guide walls together with the guide walls 4 will form channels for the through-flow of water.

The outer walls 8 spiral round the chamber in the longitudinal direction together with the guide walls 4 in a progressively decreasing radius and cross section in each channel for the flow of water.

The outer walls 10 in the channels are specially designed, with the angle of the outer walls in the longitudinal direction giving a greater rotational 05-12-2002

circumference at the guide wall in the outlet direction (see Fig. 4). The special design of the outer walls 10 will be like an inverted funnel with the largest opening facing the direction of flow. The angle of the outer walls 10 will give a moment of force in the direction of flow of the constantly rising pressure against the outer walls due to the centrifugal force. The design will help to counteract the dynamic resistance in the chamber.

Mode of operation

On deployment in a river or ocean current, the pressure and the kinetic energy in the mass flow will drive a flow of water through the unit. Guide walls with a gradually increasing angle will give an increasing rotational motion to the mass flow. In addition, a gradually decreasing cross sectional area will give an increasing velocity to the mass flow.

With an angled surface, the progressively greater centrifugal moment of force against the outer walls provides a resultant force in the direction of flow that will increase the angular velocity and the moment of inertia in the rotation as well as counteracting the dynamic resistance. At the outlet of the chamber the mass flow will have the greatest mass velocity, the smallest radius and the greatest angular velocity.

The kinetic energy in the rotation together with the pressure against the outer walls constitute the usable energy, which at the outlet is converted to kinetic energy in a direction of motion that will be in an extension of the path of rotation and distributed round the circumference of the outlet.

Centrifugal/centripetal forces have been used for some time in turbine design in order to provide higher efficiency. The novel feature of this method is that the same forces are also utilised in the transmission and before the power transmission occurs in the turbine.

The turbine's design and mode of operation

The mass flow will be introduced into a radial flow turbine (see Fig. 5) at the rear end of the chamber 5 (see Figure 1). The radial flow turbine is specially designed so that the mass flow will be angled from an almost perpendicular movement out from the axis of rotation back to a movement in the longitudinal direction. This change in motion occurs in a 3-dimensional 05-12-2002

plane. An outwardly directed movement is angled longitudinally in order to give a transversal reaction force through the turbine's blades.

With a rounded outer wall 21, the turbine will turn the mass flow in the longitudinal direction while the mass flow passes through the turbine's blades 22.

This motion will exert a new centrifugal moment of force in the unit that reinforces the pressure on the turbine's blades. The reaction forces created in the turbine are transferred either mechanically or hydraulically to a water- cooled generator. At the outlet of the turbine, the water flow will be returned to the river's normal water velocity, and the turbine's underside 24 together with the surrounding hull's outlet side 6 (see Fig. 1) are designed in such a manner that the flow of water obtains a progressively larger cross sectional area for the outlet flow, resulting in reduced flow velocity. The shape 12 of the outer hull should also provide a negative pressure behind the unit that reduces the resistance on the outlet side for the flow of water.

Location for power production

For commercial use, the chamber together with turbine and generator, enclosed by the hull, will form an independent power production unit when placed on riverbeds, the bottom of channels and tunnels, in underwater areas with a large tidal range and in ocean currents.

The underside of the hull may be equipped with reinforced attachment points for securing to the base in the riverbed or fixed with wires to a securing point on the riverbed in front of the production unit. Choice of material

The material in the chamber and casing may be of plastic, metal or other suitable materials or combinations thereof.

Background

The inventor has carried out extensive searches and has not found any similar structure in the field of hydropower where centripetal/centrifugal forces are utilised in this manner. In some turbines the centrifugal force is used as a 05-12-2002

power-enhancing moment of force. Centrifuges and some types of fans and pumps as well as particle research are just a few examples of how centrifugal force is utilised, but the method is different from that described herein.

The only literature the inventor has found in his research where this type of technology is intended for use in power production was produced by Viktor Schauberger (1885-1958).

Eli Afnes, the Institute of Geology, University of Oslo, has written an essay on Schauberger's work, and this can be found on http://www.geofysikk.uio.no/~eli/mnvit/essav.html

The principle of his research was to pass media such as water or air through spiral-shaped pipes of a specific material and with a special oviform cross section.

The structures for which Schauberger has left descriptions are therefore of a different type of design and mode of operation than the principles covered by this invention.

Renewable energy source and minimal encroachment on nature

We have two main types of power stations; a power station with reservoir and a run-of-river power station. In both types potential energy will be converted to kinetic energy, and both types of power station are based on a difference in water height on the inside and outside of a turbine in order to provide power production.

With traditional methods for hydropower production, the relatively low flow of water in rivers is generally not usable on a large scale for economic and technological reasons as well as environmental considerations. Traditional hydropower production is based on pressure and head and involves large installations with comprehensive structures and buildings, frequently resulting in a substantial encroachment on nature.

The production unit described herein can be compared more with the power production from modern windmills. The production units are relatively small and may be located in groups of several units in order to provide an efficient and collective transmission of power lines to the electric network in general. 05-12-2002

The method utilises a renewable energy source, and in the current debate in society on global warming and international climate agreements for limiting the fossil fuel pollution, the introduction of new technology in hydropower production as described herein could be of vital importance for the environment as well as having a major industrial potential. Compared to other types of power production based on renewable energy sources, there will also be significant advantages with this technology described herein.

The power potential in a river with a relatively steady supply of water will be correspondingly stable for power production. The units are placed on riverbeds and in ocean currents, and do not require any greater intrusion on nature than a fixture point on the bottom. The units will not be visible in the environment since they are located on the riverbed.

The units on the bottom will probably have very little effect on the environment in which they are located since the units will have the same total through-flow in the unit as otherwise in the river. They do not entail any damming of the river.

The units may be completely or partly assembled on land, and transported by boat or helicopter to the deployment site without the need for expensive and permanent encroachment on the natural surroundings in the form of construction roads.

All things considered, there will be many positive environmental factors with few negative consequences.

Power principle and output

The power principle can be illustrated by a shot-putter, who has to throw a ball as far as possible. The ball weighs 7.26 kg, which together with the shot- putter's body weight gives the kinetic output, which in turn together with the strength in the throwing arm and body in a right-angled movement gives a pressure that constitutes the impulsive force.

The principle of traditional hydropower production is the same, where weight and pressure are the important elements based on Newton's 2. law: F = m -g.

A good shot-putter can throw the ball 20 metres, but by equipping the same ball with an aid in the form of a metre of wire, a hammer thrower will throw 05-12-2002

the same ball 80 metres (the weight of the ball is the same in the two athletic events.)

Even though the physiological conditions are relatively similar for the top athletes in the two events, with relatively equal strength and weight, the substantial difference in the lengths of throw achieved must therefore be explained by the physical principles employed.

A hammer thrower uses a completely different power principle to a shot- putter and achieves a far higher energy potential, which in turn is documented by much longer length of throw for the hammer. The same power principle employed in hammer throwing is also utilised in the method described herein. The physical conditions that form the basis for exploiting the centrifugal forces are based on known physical formulae for centripetal force:

F=mv² /r. (Force = mass * velocity to the second power/radius) The centrifugal force is the oppositely directed imaginary force component for the centripetal force.

On the basis of the formula it can be seen that an increase in the velocity of the flow of water gives a quadratic increase in the force, in addition to which the magnitude of the centripetal force is dependent on the smallest possible radius of rotation. The mass flow of the river or the ocean current gives the mass that is required in the formula, and based on the mass flow the centripetal chamber is designed to satisfy three conditions for efficient power production:

1) It is important to achieve the greatest possible mass velocity that gives the greatest output with a quadratic increase in the potential.

2) The smallest possible radius of rotation will give the greatest output potential.

3) The dynamic losses with power components in the direction of flow must be reduced as much as possible. In the design of the chamber, the three units in the formula for centripetal force; mass, velocity and outlet radius, are given the conditions that should result in the greatest possible effect. 05-12-2002

The first condition for achieving a centripetal output is a certain mass velocity of the flow of water. This condition is achieved through a gradual narrowing of the cross section in the chamber. Mass velocity is defined in physics as transport of mass per time unit and has the dimension kg/s. The continuity equation indicates that the volume of the mass passing the cross section at the inlet to the chamber must be the same at the outlet since the water is not compressible.

The continuity equation can be written in the form:

A1*V1 = A2*V2 where Al is the area at the cross section at the inlet and A2 is the area at the cross section at the outlet.

VI is velocity of the mass current at the inlet and V2 the equivalent at the outlet.

The condition demonstrates that a narrowing of the cross section will mean that the velocity of the flow of water must be increased by means of a reduced cross section to enable the same volume amount per time unit to pass through.

This is implemented by means of so-called Venturi tubes in measurement technology for velocity measurement of fluid flows in pipes. In principle the Venturi tube consists of a short biconical tube that is incorporated in the pipeline concerned. By means of calculations with the equation, the static pressure difference that is created on account of the velocity difference in the water between the inlet and the narrowest part of the Venturi tube will give the volume flow in the pipe. The technique for increasing the mass flow is therefore known and well-established.

The design of the chamber employs the same principles in order to obtain an increase in the velocity of the mass flow, with the chamber giving a progressively smaller cross section in the flow direction and a gradual acceleration of the water velocity. The mass volume per time unit will be the same for all cross sections of the chamber and the same mass volume as at the inlet of the chamber. 05-12-2002

The design of the chamber will give progressively greater mass velocity through the progressively smaller cross sections in the chamber compared with the river's basic velocity.

In order to establish a substantial centripetal moment, the conditions for achieving this will be attained with greater velocity for the same mass volume per time unit.

The next condition for creating a centripetal moment is to obtain a rotational motion in the water. The rotational motion is obtained by means of the guide walls in the chamber. The guide walls are angled gradually and logarithmically per unit of length in such a manner that the flow of water achieves the greatest possible rotational velocity at the chamber's smallest cross section, i.e. at the chamber outlet.

The third condition is the most important since the dynamic losses are considerable with a rotation of the water against an angled surface such as, e.g., in a funnel.

If the outer wall is flat, the force components will consist of a centripetal force and its counterforce, the centrifugal force, which will be perpendicular to the kinetic energy in the flow of water, thereby cancelling each other out. The force components will therefore not deduct from or add to the kinetic energy if the outer wall is flat.

With a conical funnel shape, the centripetal force will create a pressure against an angled surface that gives force components against the direction of flow. The water will climb up the funnel wall during the rotation, in turn regulating and reducing the mass flow with pressure loss until a stability level is achieved between the forces. The result will be an extremely limited mass transport with a small force potential.

The shape and angle of the outer walls will therefore be of the greatest importance for the dynamic resistance in the chamber since it is precisely this progressively increasing pressure on the outer walls that is desirable in the unit.

The centripetal chamber exploits this with outer walls that are angled with the direction of flow while the radius is simultaneously reduced. This is achieved with a special geometric shape. Each guide channel consists of 2 υs-iz-zuυz

guide walls and the outer wall between the guide walls with the largest opening in the axis line facing the outlet with a longitudinal attachment for the outer wall recessed in the guide wall in the inlet direction. This angle can be viewed as an inverted funnel and provide a positive force component in the direction of flow.

The centrifugal force has several force components by means of a force against the outer walls. One of the force components will be directed towards the direction of flow since the chamber will have a progressively smaller radius of rotation downstream than upstream. This negative radius angle in the flow line will give a force component against the direction of flow, but with a corresponding angle in the outer wall the forces will be balanced. With a larger angle in the outer wall the force component will be positive in the direction of flow.

The difference from traditional hydropower An important calculation formula is Bernoulli's equation for calculation of energy in the form of pressure, height difference and motion in flowing fluids. This equation forms the basis for calculations where the height difference is the most important element in the equation in the field of traditional hydropower. With Bernoulli's equation one can calculate the kinetic force and the pressure sum of the amounts of energy possessed by the water at the inlet to the chamber that impel the water through the chamber.

On consideration of the flow of fluid in the longitudinal direction through the chamber with Bernoulli's equation, there will be a progressive decrease in potential energy as a result of an increase in the velocity in the longitudinal direction. This can be calculated by Bernoulli's equation, which establishes that the sum of the amounts of energy must be constant and the same with different cross sections of a flow channel. With higher velocity in the volume flow, the kinetic energy will increase at the cost of the potential energy since the total energy is constant.

The chamber does not utilise the potential and kinetic energy in the longitudinal direction directly as in a traditional hydropower station. On the contrary, the chamber is designed to provide the least possible flow loss through the chamber in order to obtain the best possible velocity in the water 05-12-2002

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through-flow and thereby the greatest possible angular velocity in the rotational motion. A rotating moment of inertia with a stored potential energy from the centrifugal force represents the energy potential and not the energy conditions in Bernoulli's equation, which is linear in the longitudinal direction through the chamber.

The shape of the chamber gives the centrifugal force an increasing force component since the acceleration increases due to the fact that the speed constantly changes direction at each point in the circuit. The acceleration increases constantly through the chamber and is represented by a = v²/r where r is the radius of rotation.

The mass flow at the outlet will have a kinetic energy component in the rotational path and a potential energy perpendicular to the rotational axis of the mass flow and in magnitude will be proportional to the centrifugal force at the chamber outlet. After passing through the turbine, the water will be discharged into a flow chamber that will have a negative pressure on account of the profile of the hull round the centripetal chamber.

This will reduce the pressure resistance for the flow of water at the outlet.

Power loss Power loss in the chamber will mainly occur on account of an increasing friction between water and the outer and guide walls in addition to power loss on account of turbulent water flow. These losses are proportional to the square of the velocity of the mass flow.

There will also be dynamic losses due to the progressively smaller cross section in the chamber in addition to losses due to the angle of the water direction.

In addition to this, static losses such as shape resistance, losses in transitions and turbines will also apply.

The design of the chamber aims to reduce these losses as far as possible. A long chamber will give a smaller angular rotation per unit of length and less dynamic resistance in the chamber. 05-12-2002

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The outer walls in the channel's course between the guide walls are designed with an oppositely angled surface that is positively directed towards the outlet in the axis line in order to give a positive force component downstream. The chamber's external dimension, the chamber's narrowing in the longitudinal direction and the partitions' angular increase per unit of length are calculated on the basis of the water flow's initial velocity, available water level and position in order to give the greatest possible centripetal motion of the water through the chamber. Output

The efficiency available will be dependent on dynamic and static losses in the chamber, losses in the turbine and losses in power transfer to the generator.

Assuming that the following data apply to the unit: Size of the inlet: 3 x 3 metres = 9m²

Size of the outlet: radius = 0.47m => 0.67 m

Ratio inlet/outlet: 1 : 13

River's velocity: 1 m/s

Mass volume per sec: 9000 kg/s Outlet angle: 45° the centrifugal force has a very large moment of force. The above data result in the unit rotating 9 tons of water at a rate of 13 m/s with a radius of 0.47 m at the outlet of the chamber. The moment of force will be:

F = m - v²/r = 9000 - 13² /0.47 = 3.2 MN The theoretical output in the unit will be:

P = m ^■ v³/r = 9000 ^■ 13³ /0.47 = 42 MW

Parts of this output can be utilised to give a greater angular velocity, larger moment of inertia and an increasing kinetic energy by means of angled resultant forces in the direction of flow. 05-12-2002

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The greatest energy potential will be the stored potential energy in the centrifugal force implemented in the turbine.

Just as the windmill has the ability to exploit the kinetic energy in the wind in a mill principle, the turbine will be subject to Betz law, which calculates the usable energy viewed in relation to velocity of the mass flow at the turbine inlet and outlet.

The law looks at the relationship between the distributed transport of mass through a specific area that is occupied by a turbine compared to unimpeded passage.

Unimpeded passage: P₀ = (p/2)-V_] ³-A

Ratio in the relationship: (P/P₀) = (1/2) (1- (v₂/v,)²) (1 + (v₂/v,))

In a plot P/P₀ as a function between v₂/v₁ will give the following graph:

P/P„

We can see that the function gives a maximum for v₂N_x = 1/3, and the maximum power, which can be utilised is 0.59 or 16/27 of the total energy potential.

The graph demonstrates that the whole power potential cannot be utilised since a part of the power will have to be used to move the water out of the turbine before new usable power can be created.

In addition there will be dynamic and static power losses, but even with efficiency as low as 20 - 30%, usable power can be substantial. 05-12-2002

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The various components in the unit require no new development of materials. The electrical components that have to be located under water are already developed for underwater mill projects in ocean currents. The unit can easily be placed in serial production. Besides the production of pure and renewable energy, the units will also provide substantial environmental benefits since the units are placed on riverbeds or on the seabed and are therefore not visible in the landscape. Nor do the units require any land area, expensive construction roads or large constructional encroachments in nature.

Claims

05-12-200214CLAIMS

1. A guiding device for increasing the output of a water turbine, where the flow of water is guided through a guiding device and subsequently into a turbine mounted on the outlet of the guiding device, characterised in that the guiding device comprises guide walls (4), which together with outer walls (11) between the guide walls form guide channels (18) with an elongated spiral shape.

2. A guiding device according to claim 1, characterised in that the inlet (2) of the guiding device has a large cross sectional area that gradually decreases in the longitudinal direction towards the outlet (7).

3. A guiding device according to claims 1-2, characterised in that the guide walls (4) and thereby the channels (16) are twisted at a gradually increasing angle to the flow of water through the unit.

4. A guiding device according to claims 1-3, characterised in that the outer walls (10) at each point along the flow line in each channel (18) are angled with a larger opening (11) along the longitudinal axis from the inlet (2) towards the outlet (7).

5. A guiding device according to claims 1 -4, characterised in that the turbine is designed with an angled inlet (23) directed towards the turbine's axis of rotation, which develops into a rounding in the outer wall (21) and inner wall, and where blades (22) are attached, and which is gradually rounded at an oblique angle in the longitudinal direction.

6. A guiding device according to claims 1-5, characterised in that the turbine comprises a hemisphere (24) located in the circular transverse area between the turbine's outlet.

7. A method for increasing the output of a water turbine, where the flow of water is guided through a guiding device to the turbine, characterised in that the flow of water is set in rotation and attains an increase in velocity when it passes through the guide apparatus.

8. A method according to claim 7, characterised in that the water is set in rotation and obtains an increase in velocity by passing through channels in the guiding device that have an 05-12-2002

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elongated spiral shape and a gradually decreasing cross section towards the guiding device's outlet.