Rate of penetration has been considered as an important factor in the entire drilling industry, which can largely determine the overall costs of drilling a well. This paper proposed a novel real-time prediction of rate of penetration by combining the Attention-based Bidirectional-Long Short-Term Memory and Long Short-Term Memory (Att-Bi-LSTM-LSTM). Eight parameters, which are total vertical depth, weight on bit, revolutions per minute, mud flow rate, density, viscosity, drill-bit outer-diameter, lithology, and rate of penetration, are adopted as datasets. The drilling speed of the well is trained and validated through the drilling data while a sliding window is introduced for the real-time update. In addition, the presented prediction model is compared with other traditional prediction methods. Finally, the prospect of field application and further study is discussed and suggested. The results indicate that the proposed model shows good accuracy and robustness. Moreover, compared with the traditional methods, the model exhibits good superiority with smaller absolute and relative errors. For field applications, the model proposed in this paper attempts to provide a solution to the prediction of real-time rate of penetration. The results are expected to provide guidance for the further study on the increase of drilling speed and reduction of well costs. ... Read more

High temperature superconducting (HTS) generators are being considered for large offshore direct-drive (DD) wind turbines as they are expected to be lightweight and compact. However, short circuit torques of an HTS generator with integral-slot distributed windings (ISDWs) are too high for wind turbine constructions, mainly due to the large magnetic air gap. Fractional-slot concentrated windings (FSCWs) can be considered to address this issue since their high leakage inductance can limit short circuit currents and torques. Unlike ISDWs, FSCWs produce great contents of space harmonics that induce excessive losses in rotor components. Multi-layer and stator-shifting windings have been proposed to effectively reduce such losses. Based on a conventional 12-slot 10-pole configuration, this paper evaluates the effects of multi-layer and stator-shifting FSCWs on torque production and loss reduction in a 10 MW DD HTS generator. The examined losses include eddy current losses in the rotor shields and AC losses in the HTS field winding. This paper also checks if these FSCW schemes maintain the advantage of achieving a low short circuit torque. The results show that a 6-phase stator-shifting winding is the best choice for applying FSCWs to HTS generators. ... Read more