Double horse-head pumping unit, being one of the most classical mechanical equipment, has high efficiency and good balance ability during the oil extraction owing to its horse-head structure connecting with the rod by the steel wire rope. But its characteristic of energy consumption reduction is limited because of the motor torque fluctuation and negative torque appearing while the pumping unit is working in the upstroke and downstroke. The compound balance design is applied to the double horse-head pumping unit by the crank balance and walking beam balance, which is completed by the equal energy principle during the up and down circulation of the oil suction unit. The finite element model of the whole equipment is built, and the simulation analysis is completed by the software ADAMS, under the conditions of the compound balance and that of the crank balance. The output torque of the crank, the forces from the back horse-head rope, and the connection pin are calculated. From the viewpoint of system design to compare with the traditional crank balance pumping unit, the compound balance design can reduce the torque fluctuation greatly, decrease the forces of steel wire rope connecting with the back horse-head, and get rid of the structure problems from the traditional pumping unit. The stress test of the double horse-head pumping unit designed by the compound balance method is completed in the oilfields. It has proved the correctness and reasonability of the compound balance design. The methodology of the compound balance design is helpful in improving the work efficiency and reliability and bringing about better abilities of energy consumption reduction for the pumping unit during its work circulation.

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OpenFOAM is a free, open-source software package that can be used for the solutions of computational fluid dynamics and simulation of various fluid flow processes. Nevertheless, OpenFOAM still lacks default settings and a large number of different numerical schemes and turbulent models should be validated. In this paper, the unsteady flow around a cylinder (Re=3900) is calculated by the large eddy simulation of OpenFOAM. The predictions include the drag and lift coefficient, the pressure distribution around the cylinder, the velocity distribution and Reynolds stress distribution in the wake region, as well as the prediction of the recirculation length and separation angle. Thanks to several simulations, these five subgrid-scale (SGS) models are compared and studied: The Smagorinsky SGS model, wall adaptive local eddy visibility SGS model, dynamic SGS model with Lagrangian averaging, dynamic one equation eddy visibility model, one equation eddy visibility model. The numerical results are verified with the published experimental data.

Some special compact mechanical transmissions with multi-load are required in robot joints, artillery systems, agricultural machinery and multirole shaft-driving devices, but the existing products of mechanical transmissions cannot meet the demand of modern industry, and need some new transmission structure or solution. To this end a novel worm gear named the planar enveloping internal-meshing worm drive is proposed for applications requiring multi-load transmission for the first time. Its meshing functions, including the induced normal curvature, lubrication angle, and relative entrainment velocity, are developed on basis of gear meshing theory. Furthermore, the meshing zone for the worm tooth is analyzed through tooth contact analysis in order to determine the optimal mother plane dip angle b. Moreover, the tooth profile of the worm wheel is optimized and the worm parameters obtained through tooth contact analysis is verified. Finally, the worm gear is manufactured by using the 3D-printing technology to measure the correction for the theory investigation. The presented worm drive exhibits ideal meshing performance, with minor contact stress and high lubrication. This gear set is expected to find applications in such systems as robot joints, artillery systems, and multi-roller shaft-driving devices.

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