| 摘要 |
A pressure pulse generator, or "pulser," and methods for operation are described. The pulser is constructed of a stator and rotor mounted within a housing, each being configured with a central hub and one or more radially extending lobes. An equal number of ports are spaced between the lobes. The lobes of the rotor are cross-sectionally tapered in the streamwise direction. The rotor and stator are maintained within the housing in a coaxial spaced relation from each other. The axial distance between the rotor and stator may be selectively varied by a linear actuator. In a preferred embodiment, the linear actuator comprises a conventional solenoid assembly which is operably associated with the rotor to move it axially within the housing with respect to the stator between a first position, wherein the distance between the rotor and stator is reduced, and a second position, wherein the distance between the rotor and stator is increased. The linear actuator is energized in response to signals from an encoder. Movement of the rotor to its first position causes the pulser to move into a stable closed condition wherein the ports of the stator are blocked by the lobes of the rotor. Movement of the rotor to its second position causes the pulser to be moved into a stable open position wherein the ports of the stator are not blocked by the rotor's lobes. The opening and closing occurs with a snap action between its stable open and stable closed positions, causing discrete pulses to be generated within the mud column. The pulser assembly is capable of generating different types of telemetry signals including non-return to zero
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