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 of operating a rotor aircraft involves measuring an airspeed of the aircraft and a rotational speed of the rotor. A controller determines a Mu of the rotor based on the airspeed of the aircraft and the rotational speed of the rotor. The controller varies the collective pitch of the rotor blades in relationship to the Mu, from an inertia powered jump takeoff, through high speed high advance ratio flight, through a low speed landing approach, to a zero or short roll flare landing. In addition as the rotor is unloaded and the rotor slows down, the controller maintains a minimum rotor RPM with the use of a tilting mast.

A rotor aircraft has a tilting hub for cyclic control operated by either a tilting spindle or swash plate mounted to the upper end of the drive shaft. A spinner housing with two separate half portions encloses the hub. The blades of the rotor have root portions that are integrally joined to the separate half portions. During a collective pitch change, the half portions rotate relative to each other, but at advance ratios greater than about 0.7, when the collective can be held constant, the spinner half portions can be in perfect alignment. Concentric control sleeves surround the drive shaft for changing collective pitch as well as cyclic pitch.

The invention discloses a propulsion device of an underwater robot. The propulsion device comprises a balance part, propellers and a driving mechanism for regulating an advance direction of the propellers; the balance part is used for keeping the propulsion device balanced; and an underwater robot includes the propulsion device and a control system for controlling the propulsion device to enable directional movement of the underwater robot, and the control system is electrically connected with the propulsion device. According to the propulsion device of the underwater robot, the propellers andthe driving mechanism are arranged, and the main function of the driving mechanism is to adjust the advance direction of the propellers; and by changing the advance direction of the propellers, morefreedom of movement of the propulsion device can be achieved, thereby achieving more freedom of movement of the underwater robot. According to the underwater robot, the propulsion device and the control system are arranged, and more freedom of movement of the underwater robot can be realized through the cooperative action of the control system and the propulsion device, thereby achieving a more complete perspective of the underwater robot monitoring.

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 discloses a ducted propeller equivalent advance ratio working condition calculation method. According to the method, fitting is conducted on the relation of the tension coefficient under a certain angle of attack of an open propeller and the advance ratio through an equation; the ducted tension factor q and the outlet area ratio sigma are determined; a thin cylindrical ducted propeller calculation formula is adopted for the ducted tension factor q; the open propeller tension T1 is obtained by inputting the rotating speed and the current advance ratio, the initial V1 is worked out through the formula (please see the formula in specification), and the equivalent incoming flow speed V0 is calculated through the formula (please see the formula in specification); the equivalent advance ratio lambada n is obtained through the equivalent incoming flow V0 and the current rotating speed; judgment and convergence are conducted. The method is simple, easy to implement and free of tests or massive fluid mechanics calculation and has larger operation efficiency and convenience.

The invention discloses a large-advance-ratio rotor blade reverse flow velocity active control trailing edge winglet device which comprises a main rotor and a reverse arc winglet arranged at the trailing edge of the main rotor, a transmission device is arranged in the main rotor, and the transmission device is used for driving the reverse arc winglet to do sinusoidal oscillation motion; the transmission device comprises a motor, an eccentric wheel, a reciprocating sliding block and a transmission gear set, the motor drives the eccentric wheel to rotate so as to drive the reciprocating sliding block to do linear reciprocating motion, a rack is arranged at the end, away from the eccentric wheel, of the reciprocating sliding block and meshed with the transmission gear set, a small wing gear meshed with the transmission gear set is arranged in the reverse arc small wing, and the rack drives the transmission gear set to rotate so as to drive the small wing gear to rotate. The reverse arc winglet does sinusoidal oscillation motion on the rear edge of the main rotor, the rear edge is reversely folded through curved surface deformation, the wing type rear edge can be more tightly aligned with oncoming airflow, and therefore the reverse flow aerodynamic problem is greatly solved, and the reverse flow velocity is controlled.

The invention discloses a cruise propeller matching optimization method suitable for a piston power unmanned aerial vehicle. The method comprises the following steps of: introducing a required thrust matching coefficient CR by taking thrust required for aircraft cruise as an entry point and utilizing a thrust coefficient and a forward ratio so as to eliminate coupling characteristics of a propeller speed and an engine speed, and establishing a corresponding relation between the engine speed and propeller efficiency; the minimum unit thrust fuel consumption (SFC) serves as a design target, matching working points of an engine and a propeller are selected, the optimal engine rotating speeds corresponding to different air doors of the engine are set, the minimum cruising fuel consumption is achieved on the premise that the cruising thrust requirement is met, and an aircraft can obtain the optimal endurance performance. The selection process of the matching working points of the engine and the propeller is greatly simplified, and the matching working efficiency of the propeller engine of the piston propeller power unmanned aerial vehicle is remarkably improved; and a design basis can be provided for a wind tunnel test of a complete machine with a propeller, engine control logic rotating speed setting and the like, and finally, the flight endurance performance of the aircraft is optimized and improved.

The invention belongs to the helicopter rotor design and theoretical modeling technology, discloses a calculation method for improving the balancing convergence of a rotor with a large forward ratio,wherein the method adopts a successive approximation method and a residual monitoring method to improve a rotor balancing calculation method, and is different from a traditional balancing iterative calculation method. According to the calculation method for improving the balancing convergence of the rotor with the large forward ratio, encryption division is carried out on forward ratio parameters,a successive approximation method is used for calculating and monitoring residual error changes in an iterative loop in real time, the calculation capacity of rotor trim is effectively expanded, thetrim solving precision is guaranteed, and the divergence problem in trimming iteration is effectively avoided in a large-advance-ratio state.

The invention discloses a coaxial homodromous propeller with variable phase difference. Two propellers with coincident rotating shafts are arranged front and back in the thrust direction of the propellers and comprise front propellers, propeller rotating shafts, sliding sleeves and rear propellers. The two propellers rotate in the same direction. A certain phase difference exists between the rear propeller and the front propeller to ensure that the rear propeller is far away from the wake flow spiral surface of the front propeller. In the actual operation process, if the wake flow helicoid approaches the rear propeller due to the change of the forward ratio, the rear propeller adjusts the phase difference formed between the rear propeller and the front propeller through the forward and backward movement of the sleeve, so that the rear propeller can still be located outside the wake flow area of the front propeller. According to the invention, adverse aerodynamic interference and aerodynamic noise of a coaxial propeller system are reduced.