Papers by Author: Hai Jun Xu

Abstract: Undulate fin is the main propelling organ of MPF mode fish, which could produce propelling wave continually and controllabily while swimming, and this propelling mode has characteristics of high efficiency and low disturbance to fluid field. In this paper, biological structure of “Nilotic Ghost” fish’s long flexible fin(Undulate Fin) is studied with physiological anatomizing and X-ray perspectiving means. Then motion characteristics of the undulate fin are revealed with pictures from fish’s swimming video. Under the bionical conclusions, a hydraulic-driven bionic joint for undulating thruster is designed, including a pair of restoration springs. At last some calculating simulation and testing experiments are carried out, so as to analyze and verify this bionic joint’s characteristics. Results show that, bionic joint driven by hydraulic system could immitate the flexible movements of natural rib in undulate fin, which are described as position restoration, changing of swaying range as well as frequency.

Abstract: Twin-rotor piston engine is exceedingly compact, and several times more power dense than conventional IC engines. It is necessary to analyze the transmission characteristics of the special geared linkage mechanism which is used for the power transmission equipment of the engine. Transmission angle is mainly adopted in order to obtain the transmission characteristics. Firstly, the force transmission behavior of one end of the output component is derived through the force analysis of the planet gear. Secondly, the torque transmission angle is proposed based on the multi-point force situation. Lastly, the torque transmission angle is depicted and analyzed in detail through the equivalent composite force graphical method. The result shows that the geared linkage mechanism will not produce counteractive torque to the rotation direction and has no dead point.

Abstract: The contact characteristics of spherical gear and ring-rack are researched in this paper. First, the tooth profile surface equation of spherical gear is established on the basis of the transmission theory of spherical gears. After that, the profile surface equation of ring-rack is established. Then, kinematics of the transmission of spherical gear and ring-rack is researched, the appreciate coordinates are established, and the profile surfaces of spherical gear and ring-rack are described in the same coordinate. Then, the contact analysis is conducted between spherical gear and ring-rack, and the contact point and ellipse parameters are acquired, as well as the rules of their evolvements. The conclusions above are benefit to further research on the transmission of spherical gear and ring-rack.

Abstract: Motions of natural creatures appear flexible and rhythmical characteristics. The bionic undulating propeller imitates undulating motion of a fish’s flexible long fin, and its propelling efficiencies are affected by bionic units’ characteristics. In order to improve the flexibilities of both structure and bionic motion, the paper designed a bionic undulating propeller driven by hydraulic system, and then carried out some modeling work on the rotatable direction valve. At last, some experiments are brought forward on a prototype of bionic undulating propeller. In the experiments, rotatable-direction-valve could control fluid flowing through all the oil orifices periodically and in sequence, so as to drive the bionic units swinging rhythmically. Under the control of rotatable-direction-valve, the prototype gains flexible starting and stopping processes, as well as self-resume character of bionic undulating wave, which are coincident to nature fish. The results show that application of hydraulic system in bionic undulating propeller is feasible, and theoretic model of rotatable direction valve is correct.