Rotary expansible chamber devices – Interengaging rotating members – Like rotary members
Patent
1994-05-25
1995-11-21
Bertsch, Richard A.
Rotary expansible chamber devices
Interengaging rotating members
Like rotary members
F01C 124
Patent
active
054681324
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
This invention relates to water turbines and is more particularly, but not exclusively, concerned with water turbines which are capable of providing a reasonable power output under a low head of water.
BACKGROUND OF THE INVENTION
There are a number of applications in which it would be advantageous to be able to harness power, for hydroelectric power generation for example, from a flow of water having only a low head. A typical application is one in which power is to be generated by means of the water flow of a small river or stream where the head of water available is limited by the lie of the land and the necessity to limit civil engineering works on the basis of cost and/or environmental considerations. The use of conventional water turbines in such applications is for the most ruled out by the requirement for such turbines of high heads of water to obtain the necessary turbine speeds for economical generation of power. Other arrangements utilizing flapping gates, displaced floats and the like are ruled out because they are bulky and work with an intermittent action. Hydraulic rams are used extensively for raising water to provide a higher head, and a ram/turbine combination might be considered to provide a possible solution to this problem, although the size of ram required for the sort of flows envisaged in most applications would rule such an arrangement out in many circumstances.
It is an object of the invention to provide a new form of water turbine which is particularly suitable for use with a low head of water.
SUMMARY OF THE INVENTION
According to the present invention there is provided a water turbine comprising a turbine chamber, inlet and outlet ports opening into the chamber for the passage of inlet and outlet water flows, and rotors arranged within the chamber with their axes of rotation parallel so as to be rotatable by the inlet water flow, each of the rotors having two or more substantially equiangularly distributed lobes and the arrangement being such that adjacent rotors rotate in opposite directions with their lobes in mesh with one another, characterised in that the overall throughflow cross-section of the inlet port or ports is less than the overall throughflow cross-section of the outlet port or ports so as to ensure that the velocity of inlet water flow is high in relation to the velocity of outlet water flow.
Such a turbine is capable of operating efficiently with a low head of water, and is additionally of simple construction and therefore inexpensive to produce. It can be made to have only a small number of wearing parts and thus has a long service life. It is also capable of handling comparatively large volumes of water without becoming too bulky.
Advantageously the or each inlet port incorporates a flow splitter for accelerating the inlet water flow and directing the inlet water flow in the form of jets which impinge on the rotors in the required directions. Such a jetting action results in high turbine efficiency.
It is also advantageous for the rotors to define therebetween a space for taking up water trapped between the meshing lobes such that the volume of the space does not decrease during rotation of the rotors. To this end each lobe may be cut away at its trailing edge in order to provide the space for taking up trapped water. Preferably the rotors have cycloidal lobes, although in certain cases the lobes may have a form based on involute geometry. Furthermore each lobe of each rotor may comprise a radially inner part having an edge which extends along a radius of the rotor and a radially outer part having a convexly curved edge.
Furthermore the chamber preferably has curved internal wall portions which lie closely adjacent to portions of the circular areas swept out by rotation of the rotors so that the tips of the lobes of the rotor which is adjacent to each wall portion almost contact the wall portion in the course of rotation.
In most applications each rotor has a length appreciably greater than its diameter, and each of the inlet and o
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Snell Leonard Stanley
Snell Michael James
Bertsch Richard A.
Freay Charles G.
Snell (Hydro Design) Consultancy Limited
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