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Your search keyword '"Feng, Renjun"' showing total 11 results
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11 results on '"Feng, Renjun"'

5. Comparative study on permeability enhancement effect of separate-layer fracturing and multi-layers comprehensive fracturing in coal seam group

Author

FENG Renjun

Subjects
coal seam group, seam permeability improvement, separate-layer hydraulic fracturing, fracturing influence range, gas drainage, gas content, Mining engineering. Metallurgy, TN1-997
Abstract

In this paper, a gas roadway with multiple coal seams in southwest China is taken as the test site, and the separate-layer hydraulic fracturing and multilayers comprehensive hydraulic fracturing are carried out. This paper analyzes the whole process of coal seam fracturing development, discusses the influence of water injection volume in coal seam on subsequent drilling construction, and obtains the distribution law of gas content and water content of coal seam after fracturing, and the gas drainage effect. And the fracturing influence ranges of the two fracturing methods are obtained. The results show that the hydraulic fracturing in coal seam composes of five stages: stress accumulation, fracture initiation, fracture propagation, multiple fracture initiation and propagation, and fracture propagation completion. Compared with the multilayers comprehensive hydraulic fracturing, the average pressure of separate-layer hydraulic fracturing is slightly higher, but the total water injection volume is significantly less. The gas content and water content of coal seam after separate-layer hydraulic fracturing are lower and higher than those of comprehensive fracturing technology, respectively; and the initial gas drainage concentration of coal seam is also higher. In addition, the average gas drainage concentration of single hole and drilling field are 54.1% and 43%, increased by 14.9% and 9% compared with comprehensive fracturing technology. And the effective fracturing influence radius of separate-layer fracturing and multilayers comprehensive fracturing reaches about 50 m and 40 m, respectively. This indicates that the separate-layer hydraulic fracturing technology can significantly improve the effective influence range and effect of seam permeability improvement in coal seam group. Moreover, the separate-layer hydraulic fracturing technology can reduce the water injection volume in coal seam, decreasing the bad phenomena in the subsequent drilling construction of gas drainage borehole, such as sticking drilling.

Published
2021
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11. High-Precision State of Charge Estimation of Urban-Road-Condition Lithium-Ion Batteries Based on Optimized High-Order Term Compensation-Adaptive Extended Kalman Filtering

Author

Feng, Renjun, Wang, Shunli, Yu, Chunmei, Zhou, Heng, and Fernandez, Carlos

Abstract

It is significant to improve the accuracy of estimating the state of charge (SOC) of lithium-ion batteries under different working conditions on urban roads. In this study, an improved second-order polarized equivalent circuit (SO-PEC) modeling method is proposed. Accuracy test using segmented parallel exponential fitting parameter identification method. Online parameter identification using recursive least squares with variable forgetting factors(VFFRLS). An optimized higher-order term compensation-adaptive extended Kalman filter (HTC-AEKF) is proposed in the process of estimating SOC. The algorithm incorporates a noise-adaptive algorithm that introduces noise covariance into the recursive process in real-time to reduce the impact of process noise and observation noise on the accuracy of SOC estimation. Multiple iterations are performed for some of the processes in the extended Kalman filter(EKF) to compensate for the accuracy impact of missing higher-order terms in the linearization process. Model validation results show over 98% accuracy. The results after comparing with the EKF algorithm show a 4.1% improvement in SOC estimation accuracy under Hybrid Pulse Power Characterization(HPPC) working conditions. 2.7% improvement in accuracy in Dynamic Stress Test(DST) working conditions. 2.1% improvement in Beijing Bus Dynamic Stress Test(BBDST) working conditions. The superiority of the algorithm is demonstrated.

Published
2023
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