31 results about "Advance ratio" patented technology

Disclosed is a tissue removal device having an outer tube with a resection window and an inner tube disposed within the outer tube. The inner tube is slidable and rotatable relative to the outer tube so that the distal end of the inner tube moves back and forth across the resection window to sever tissue extending therethrough. The inner tube may be driven to rotate at a speed of at least about 1100 rpm, to axially translate at a rate of at least about 1.5 cps, and with an advance ratio of no more than about 0.25. The drive system for controlling axial reciprocation and rotation of the inner tube may be totally mechanical.

A method for equalizing rolling moments at high advance ratios is disclosed including impelling an aircraft in a forward direction at an airspeed by means of a thrust source and rotating a rotor of the aircraft at an angular velocity with respect to the airspeed effective to cause a positive total lift on each blade due to air flow over the blades in the retreating direction when the blade is moving in the retreating direction. The rotor includes an even number of blades placed at equal angular intervals around the rotor hub. One or both of cyclic pitch and rotor angle of attack are adjusted such that a rolling moment of the retreating blade due to reverse air flow is between 0.3 and 0.7 times a rolling moment on the advancing blade due to lift.

A method for equalizing rolling moments at high advance ratios is disclosed including impelling an aircraft in a forward direction at an airspeed by means of a thrust source and rotating a rotor of the aircraft at an angular velocity with respect to the airspeed effective to cause a positive total lift on each blade due to air flow over the blades in the retreating direction when the blade is moving in the retreating direction. The rotor includes an even number of blades placed at equal angular intervals around the rotor hub. One or both of cyclic pitch and rotor angle of attack are adjusted such that a rolling moment of the retreating blade due to reverse air flow is between 0.3 and 0.7 times a rolling moment on the advancing blade due to lift.

The invention provides a data correction method of a high-altitude propeller wind tunnel test for influence of Reynolds number. The data correction method comprises the following steps: according to the similarity criterion of an advance ratio and a tip Mach number, experimental parameters of the high-altitude propeller scale model wind tunnel test are determined; the wind tunnel test of the propeller scale model is carried out; a tension coefficient experimental value C<T,exp> and a power coefficient experimental value C<P,exp> are measured; the tension coefficient experimental value and thepower coefficient experimental value are corrected; and a corrected propeller propulsion efficiency is calculated according to a propeller propulsion efficiency formula. The invention takes into account the difference between the Reynolds number experimental value under the condition of the equal advance ratio and the equal tip Mach number and the Reynolds number under the real working condition of the high-altitude propeller; more accurate aerodynamic performance experimental data such as the high-altitude propeller tension coefficient, the power coefficient and the propulsion efficiency is obtained by using the proposed correction method; so reliable basic data is provided for designing a propulsion system and an energy system of a high-altitude low-dynamic aircraft.

The invention relates to the technical field of pneumatic elasticity tests, and particularly to a rotation flutter simulation device capable of performing test research on key parameters of rotation flutter. The rotation flutter simulation device comprises a hanging rack beam, a short cabin beam, a pitching bearing support, a yaw bearing support, a pitching bearing cover plate, a yaw bearing cover plate, a paddle rotating shaft, a paddle, a paddle wheel hub, a pitching rotating shaft, a wheel hub hood, a yaw spring piece, a pitching spring piece, a pitching spring clip, a cushion block, a yaw spring support and a pitching balancing weight block, can simulate rotation of a propeller and gyroscopic effect per se, also can research change of yaw and pitching rigidity of an engine system, pivot point change and influence from advance ratio to rotation flutter and can realize research on multiple key variable parameters on one set of model. Therefore, model processing and testing costs are saved.

The invention discloses a coaxial and co-directional propeller with variable phase difference. Two propellers with coincident rotating shafts are arranged forward and backward along the thrust direction of the propeller, including a front propeller, a propeller rotating shaft, a sliding sleeve and a rear propeller. Similarly, there is a certain phase difference between the rear propeller and the front propeller to ensure that it is far away from the wake helix of the front propeller. During actual operation, if the change of the forward ratio causes the wake helix to approach the rear propeller, the rear propeller will adjust the phase difference between it and the front propeller through the forward and backward movement of the sleeve, so that it can still be outside the wake region of the front propeller. . The present invention thus reduces the adverse aerodynamic disturbance and aerodynamic noise of the coaxial propeller system.