The production of coalbed methane (CBM) wells varies greatly in the Qinshui Basin, North China. Analyzing the primary factors controlling the CBM well productivity is essential to improve their development efficiency. Based on the geological conditions and production data of CBM wells in the Zheng zhuang area, the principal component analysis (PCA) method was used to classify the drainage types and screen the key factors influencing the production of gas and water. The drainage types of the CBM wells in the study area can be divided into four categories. The gas production shows an increasing trend with the increase of the comprehensive score of the PCA. The key controlling factors of productivity for CBM wells can be summarized by the gas-bearing property, permeability, groundwater fluid potential, and burial depth. The impact of burial depth on CBM well productivity is manifested in its control of gas content and permeability. The groundwater flows to a low fluid potential area, which leads to a high water production and a small pressure drop. The gas production shows a positive correlation with post-fracturing permeability. The gas content is a key factor for controlling the critical desorption pressure, critical gas production pressure, and pressure drop at the gas breakthrough point. High gas content is a prerequisite for the high productivity of CBM wells.

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In this study, an arc-shaped suction slot was designed for a pneumatic compact spinning system with a lattice apron. A model was built via mechanical analysis of a fibrous strand in an arc-shaped suction slot to calculate additional twists inserted during condensing. The equations can be solved by using the Runge–Kutta method. The simulation results showed that negative pressure and frictional coefficient of the lattice apron and the fibrous strand have significant effects on additional twists of the strand in an arc-shaped slot. The curvature radius of the arc slot has some influence on the additional twists, while that of the condensing surface has no obvious effect on the additional twists. The radius of the strand may significantly influence the additional twists, but the radius of the strand itself is affected by various other factors. Spinning tests were carried out based on the model design. These results verified the additional twist model of the arc-shaped suction slot.

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The hydro-mechanical continuously variable transmission (HMCVT) is a new type transmission device, which consists of a mechanical transmission (MT) combined in parallel with a hydrostatic transmission (HST) featuring a pair of hydraulic units. The HMCVT has a continuously variable shifting ratio by the combination of HST and MT and achieves high efficiency by MT. The bench test is the important part in the research and development of HMCVT. By the bench test, these works can be carried out, such as the performance testing, the property matching of vehicle transmission, the determination of control method. In this paper, the test-bed and its control system of HMCVT assembled in DFH1302R tracked tractor are presented. The engine model and vehicle's running resistance model are established. The control principles of simulative system of engine and running resistance are studied. The communication principles of distributed control system are also discussed: the slaver computers control the throttle of engine and the eddy current dynamometer; the master computer exchanges information with the slaver computers by serial communication; the master computer collects all signals by data bus; the human-computer interaction is carried out with the virtual instrument software. The experiment results show that control test system of the HMCVT test-bed can satisfy and fulfill the test demand of the HMCVT prototype.