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Gorlov helical turbine
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The Gorlov helical turbine (GHT), evolved from the Darrieus turbine design by altering it to have helical blades/foils. The GHT is a water turbine, however its design is similar to some air turbines presently on the market, such as the Turby wind turbine and the Quietrevolution wind turbine. It was patented on July 3, 2001. Its inventor, Professor Alexander M. Gorlov of the Northeastern University.
term "foil" is used to describe the shape of the blade cross-section at a given point, with no distinction for the type of fluid, (thus referring to either a "airfoil" or "hydrofoil").
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Encyclopedia
The Gorlov helical turbine (GHT), evolved from the Darrieus turbine design by altering it to have helical blades/foils. The GHT is a water turbine, however its design is similar to some air turbines presently on the market, such as the Turby wind turbine and the Quietrevolution wind turbine. It was patented on July 3, 2001. Its inventor, Professor Alexander M. Gorlov of the Northeastern University.
Fluid Performance
The term "foil" is used to describe the shape of the blade cross-section at a given point, with no distinction for the type of fluid, (thus referring to either a "airfoil" or "hydrofoil"). In the helical design, the blades curve around the axis, which has the effect of evenly distributing the foil sections throughout the rotation cycle, so there is always a foil section at every possible angle of attack. In this way, the sum of the lift and drag forces on each blade do not change abruptly with rotation angle. The turbine generates a smoother torque curve, so there is much less vibration and noise than in the Darrieus design. It also minimizes peak stresses in the structure and materials, and facilitates self-starting of the turbine. In testing environments the GHT has been observed to have up to 35% efficiency in energy capture. (It should be noted, however, that the result for only one speed was ever made public. The claimed 35% efficiency has not been independently confirmed, nor have results been published in peer-reviewed journals.)
Turbine axis-orientation
The main difference between the Gorlov helical turbine and conventional turbines is the orientation of the axis in relation to current flow. The GHT is a vertical-axis turbine which means the axis is positioned perpendicular to current flow, whereas traditional turbines are horizontal-axis turbines which means the axis is positioned parallel to the flow of the current. Fluid flows, such as wind, will naturally change direction, however they will still remain parallel to the ground. So in all vertical-axis turbines, the flow remains perpendicular to the axis, regardless of the flow direction, and the turbines always rotate in the same direction. This is one of the main advantages of vertical-axis turbines.
Airfoil / Hydrofoil
The GHT operates under a lift-based concept (see airfoil). The foil sections on the GHT are symmetrical, both top-to-bottom and also from the leading-to-trailing edge. The GHT can actually spin equally well in either direction. The GHT works under the same principle as the Darrieus turbine; that is, it relies upon the movement of the foils in order to change the apparent direction of the flow relative to the foils, and thus change the (apparent) "angle of attack" of the foil.
Environmental issues
A GHT is suitable for low-head micro hydro installations, when construction of a dam is undesirable. The GHT is an example of damless hydro technology. The technology may potentially offer cost and environmental benefits over dam-based micro-hydro systems.
Some advantages of damless hydro are that it eliminates the potential for failure of a dam, which improves public safety. It also eliminates the initial cost of dam engineering, construction and maintenance, reduces the environmental and ecological complications, and potentially simplifies the regulatory issues put into law specifically to mitigate the problems with dams.
In general, a major ecological issue with hydropower installations is their actual and perceived risk to aquatic life. It is claimed that a GHT spins slowly enough that fish can see it soon enough to swim around it.From preliminary tests in 2001, it was claimed that if a fish swims between the slowly moving turbine blades, the fish will not be harmed. Also it would be difficult for a fish to become lodged or stuck in the turbine, because the open spaces between the blades are larger than even the largest fish living in a small river. A fish also would not be tumbled around in a vortex, because the GHT does not create a lot of turbulence, so small objects would be harmlessly swept through with the current.
See also
Method for maintaining flotation using a helical turbine assembly
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