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As a new kind of propellant binder, energetic thermoplastic elastomer (ETPE) can improve propellant recyclability and environmentally friendly disposal. The rheological behavior of the ETPE binder can be beneficial to identify suitable and safe conditions for processing ETPE propellants. In this paper, ETPE/nitrocellulose (NC) blends with different mass ratios of NC to ETPE were prepared by the physical mixing method. The heat of explosion and the morphological, thermal, mechanical and rheological properties of the resulting blends were studied systematically. It was found that the heat of explosion of ETPE/NC blends increased with increasing NC content. SEM images showed that the NC domains in the blends changed from tiny pieces to fibers with increasing NC mass ratio, which indicates phase separation in the blends. The tensile mechanical properties of the blends had a peak value when the NC content was 10 wt%, and then increased with the increasing addition of NC. The thermal behavior made clear that the ETPE and NC were partially miscible. Rheological studies on dynamic strain sweep and frequency sweep demonstrated that the content of NC in the blends had a monotonic effect on their rheological properties at 130 ∘ C. Rheological studies also showed that the rheology of the blends is dependent on temperature. The Cole − Cole and Han plots confirmed phase separation in the blends.

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In this article, a novel five-phase fractional-slot concentrated winding (FSCW) with 20-slot/22-pole is presented. It benefits not only the advantages of conventional FSCW but also weak space harmonics of magnetomotive force (MMF). The winding allows eliminating the first sub-order harmonic. The new layout of the winding topology is obtained by a combination of stator shift technique of the winding in the slots with a special coupling of the windings (star-pentagon), using winding function theory. The high performances of the new winding layout are validated using the finite element method (FEM). Compared to the conventional winding, the winding factor and the total harmonic distortion (THD) of MMF are improved by 1.3% and 2.2%, respectively. With the same injection of current density, the average output torque is increased by 1% and the torque ripple is decreased by 60%. The eddy current losses in the permanent magnets (PMs) at rated speed (600 r/min) and 2100 r/min speed are improved by 67% and 56%, respectively. Index Terms-5-phase permanent magnet (PM) machine, finite element analysis, low-harmonic contents.

Bu‐NENA (N‐butyl‐N‐nitratoethyl nitramine) base propellants have versatile qualities, such as, higher energy, reduced sensitivity, and enhanced mechanical properties. The evaporation of Bu‐NENA, which takes place in the propellant grains in the course of time, can reduce the physical properties of the propellants, weaken the propellant grains, cause the propellants to crack at stress‐concentrated points, and finally result in unfavorable increases or fluctuations of the burning rate and poor performance of the rocket motor. In this study, the evaporation of Bu‐NENA from a double base propellant was investigated using isothermal thermogravimetry. The results showed that the entire process of Bu‐NENA evaporation complied with the power law of evaporation rate with time. The values of kinetic parameters of Bu‐NENA evaporation were calculated: Evap=67.68 kJ mol−1 and Avap=1.57×105 s−1. In comparison, the values of NG (nitroglycerin) evaporation were determined: Evap=69.68 kJ mol−1 and Avap=1.33×106 s−1. The value of the activation energy of Bu‐NENA evaporation was close to that of NG, but the pre‐exponential factors differed by an order of magnitude. The evaporation of Bu‐NENA followed zero‐order kinetics at the early stage, and the enthalpy of Bu‐NENA evaporation was calculated to be 69.75 kJ mol−1 according to Langmuir and Clausius‐Clapeyron equations.

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