Abstract: A variable marine jet propulsion system incorporates a motor, a variable-pitch propeller pump in a spherical housing, a variable housing and a variable inlet duct, and a microcontroller. The pump, the nozzle and the inlet are controlled by the microcontroller, which is programmed to control the pump as a continuously variable power transmission for maintaining efficient motor operation, the nozzle for maintaining efficient pump operation, and the inlet for maintaining efficient recovery of the total dynamic head of the incoming water. The spherical pump housing maintains close fits to the propeller vane tips for more efficient operation at all pitches, including zero and reverse pitches. Zero pitch results in no effective pumping action, effectively a true neutral in fluid power transmission. Reverse pitch in combination with the large variable nozzle provides reverse flow and consequently reverse thrust, which eliminates the need for the “backing bucket”.

Abstract: An improved inlet duct for a marine jet propulsion system is disclosed designed to allow the overall system to operate more efficiently. The inlet duct includes a hydraulically efficient inlet tunnel with a forward entrance opening integrally formed on the bottom of the hull of the watercraft, and a rear exit opening formed inside the hull of the watercraft adjacent to the pump. The inlet tunnel is longitudinally aligned and gently curves upward inside said hull following streamlines of generation and has cross-sectional area that progressively increases from the fore to the aft positions therein. Disposed over the front entrance opening of the inlet tunnel is an articulating structure designed to adjust its size according to the difference in hydraulic conditions that exist inside the inlet tunnel and the outside of the hull so that the velocity of the incoming water matches the velocity of the watercraft in the body of water.

Abstract: An improved discharge nozzle and method for operating a marine jet propulsion system are disclosed designed to allow the pump to operate more efficiently. The discharge nozzle includes an outer nozzle structure mounted immediately downstream of the pump diffuser vanes which progressively reduces in diameter towards its rear exit opening. A needle is mounted within the diffuser hub and travels in axial alignment within the outer nozzle structure to adjust the effective opening of the discharge nozzle according to a pump affinity relationship, so that the pump is always operating at the most efficient head and flow for its current shaft RPM, regardless of boat speed or pressure recovery in the inlet duct.

Abstract: An improved water jet propulsion system for a jet propelled watercraft is disclosed designed to operate more efficiently. The improved propulsion system includes an adjustable water inlet duct, a larger pump, and an adjustable discharge nozzle. The inlet duct includes a hydraulically efficient inlet tunnel with an adjustable entrance opening which adjust in size according to the velocity of the water-craft in the body of water and the flow of water through the system. Using the inlet tunnel and the adjustable grate structure, the total dynamic head of the incoming water may be recovered at the pump. The pump is larger than typical pumps used on jet propulsion systems so that a greater flow of water at low head pressure may be delivered to the adjustable discharge nozzle. The adjustable feature on the discharge nozzle enables the flow through the system to be adjusted so that the hydraulic conditions on the pump are maintained at all boat speeds and all shaft rpm.

Abstract: An enhanced method and apparatus for driving an immersed flashing light system used for enhancing algae growth is disclosed. The flashing light system includes a plurality of light source elements that are arranged to illuminate the algae. The light source elements are electrically connected to form ".eta." banks of light source elements. Power is supplied to each bank of light sources in a predetermined sequence at regular intervals to substantially evenly supply each bank of light source elements with a series of power pulses while maintaining a substantially continuous load on the power supply. The power pulses are substantially half cycles of a square wave.

Abstract: An anaerobic digester for digesting animal manure and other biologically degradable material contains support media for enhancing the contact between the microbes in the digesting mass and the available nutrients. The digester includes a novel fluid circulation and distribution system. The distribution system prevents build up of heavy material in the bottom of the digester and prevents agglomeration of light material at the top of the digester. The digesting fluid travels over a floating weir into an intake and impeller assembly. The impeller drives the fluid through a conduit located adjacent the floor of the digester. Nozzles in the conduit project the fluid downwardly toward the floor thus causing a sweeping action on the floor. Fluid then flows upwardly past the support media. Risers are provided at the ends of the conduit, which terminate in nozzles at the surface of the digesting liquid.