A system and method for measuring a speed of an engine are provided. The engine has a positive displacement pump drivingly connected to a rotor shaft thereof, the pump having an inlet for receiving a fluid supply and an outlet for outputting pressurized fluid. A sensor signal is received from a pressure sensing device provided at an inlet of the pump, the sensor signal comprising a series of periodic oscillations. A frequency of the oscillations is determined, the frequency proportional to a rotational speed of the rotor shaft. The speed of the engine is then determined from the frequency of the oscillations and the speed of the engine as determined is output for controlling operation of the engine.

Provided are an impeller and a centrifugal pump that can be simplified in structure and reduced in weight and cost, and that can be integrally molded by a mold or the like. In a centrifugal pump including a housing having an inlet, an outlet and an impeller chamber, an impeller is disposed in the impeller chamber and is rotationally driven by a driving shaft. The impeller includes: a shaft part connected to the driving shaft to rotate about an axis line extending toward the inlet; blades protruding radially outward from an outer periphery of the shaft part; and an annular shroud plate continuous with the blades so as to cover a tip side area of the blades in order to be disposed adjacent to an inner wall of the housing on the inlet side.

Provided are an impeller and a centrifugal pump that can be simplified in structure and reduced in weight and cost, and that can be integrally molded by a mold or the like. In a centrifugal pump including a housing having an inlet, an outlet and an impeller chamber, an impeller is disposed in the impeller chamber and is rotationally driven by a driving shaft. The impeller includes: a shaft part connected to the driving shaft to rotate about an axis line extending toward the inlet; blades protruding radially outward from an outer periphery of the shaft part; and an annular shroud plate continuous with the blades so as to cover a tip side area of the blades in order to be disposed adjacent to an inner wall of the housing on the inlet side.

A system and method for measuring a speed of an engine are provided. The engine has a positive displacement pump drivingly connected to a rotor shaft thereof, the pump having an inlet for receiving a fluid supply and an outlet for outputting pressurized fluid. A sensor signal is received from a pressure sensing device provided at an inlet of the pump, the sensor signal comprising a series of periodic oscillations. A frequency of the oscillations is determined, the frequency proportional to a rotational speed of the rotor shaft. The speed of the engine is then determined from the frequency of the oscillations and the speed of the engine as determined is output for controlling operation of the engine.

An energy-recovery system has an energy-recovery turbine to receive a flow of water from a water line to which the turbine is connected and to generate electric power from the flow of water while also regulating water pressure in the water line. The system also includes a pressure-regulating valve (PRV) connected in parallel with the turbine to regulate the water pressure in the water line only when the turbine is inoperative. The system includes a spiral water-flow adapter having a water inlet for connecting to an upstream portion of the water line and a water outlet for connecting to a downstream portion of the water line, the spiral water-flow adapter directing the flow of water from the water inlet into the turbine and then to the water outlet.