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Based on the inspirations that slickwater volume fracturing can produce and communicate microfractures, acid fracturing is applied to carbonate rocks by using composite osmotic acid with large disp...

Interior permanent-magnet synchronous machines (IPMSMs) have the advantages of high efficiency, high power density and outstanding flux-weakening ability, which make them widely adopted in electric vehicles (EVs). Conventional IPMSMs using rare-earth permanent magnet (PM) materials face the problems of instable price and irreversible demagnetization under extreme operating conditions. To overcome these shortcomings, a V-shape combined pole IPMSM (VCP-IPMSM) is proposed, in which NdFeB PMs at the outer ends of V-shape pole are replaced by ferrite PMs. The improvement of the magnetic-pole scheme on air-gap flux density is analyzed, and the influences of the magnetic-pole geometries on electromagnetic performance are investigated. The thermal circuit model of VCP-IPMSM is established, and the demagnetization characteristics of the machine at different temperatures are analyzed, by which the thermal and demagnetization constraints of magnetic pole are obtained. The genetic algorithm based on response surface models is applied to optimize the magnetic-pole cost and electromagnetic torque simultaneously. Accordingly, with thermal and demagnetization constraints integrated with the optimization method, an optimum scheme is obtained. In comparison with the conventional IPMSM with single-material pole, the proposed VCP-IPMSM is proved to be able to promote the air-gap flux density quality, improve the anti-demagnetization ability at high temperature, and decrease the rare-earth PM consumption with the output torque remaining unchanged.

Reduced chemical mechanisms with a small size and good performance are very important for the simulation of advanced combustion engines. In the present study, a new reduction method of detailed che...

Herein, a zwitterionic Gemini VES (named VES-C) with double ultra-long hydrophobic tails was designed and synthesized which aimed to construct WLM net-structures in high-salinity aqueous solution. Due to the carboxylic group on the spacer, it exhibits partial carboxyl betaine properties and performs well in high salinity environment. Molecular dynamic simulation was carried out and RDF curves were analyzed to predict and explain the mechanism of salinity tolerance of VES-C. Compared with cationic Gemini VESs, a series of experiments were conducted by varying salinity, including surface tension, DLS, 1H NMR and fluorescent probe, to explain the salt-tolerance mechanism of VES-C. The salinity cloudy point of VES-C surpasses 10 wt%, exhibiting superior salt-tolerance to those cationic Gemini VESs. Trough viscosity measurement, oscillatory measurement and microstructure observation, it proves that VES-C molecules can construct WLM netlike structures within the salinity range from 3 wt% to 10 wt% (optimal salinity: 4 wt%), thus VES-C can be applied as the clean thickener to prepared seawater or brine based fracturing fluid by constructing WLM netlike structure in high salinity aqueous environment, which leaves the preparation of clean fracturing fluid independent of freshwater resources.

The radical polymerization of acrylamide, acryloylmorpholine, acrylate or 2-acrylamide-2-methyl propane-sulfonate in water initiated with ammonium persulfate or 2,2′-azobis(2-methylpropionamide)dihydrochloride was carried out to produce copolymer for enhanced oil recovery (EOR). The structure of the acrylamide copolymer was determined by infrared (IR) and 1H-NMR. Influence of synthesis condition on viscosities of products was studied. As a kind of potential displacement agent the salt tolerance temperature resistance and displacement performance of copolymer were also investigated in this paper. The introduction of ACMO and AMPS improves the thermostability of copolymer. The ability of the AM/AANa/ACMO/AMPS copolymer to reduce permeability is higher than HPAM. The tertiary recovery of the former is also higher than that of the latter whether in homogeneous or heterogeneous condition.

Well defined core–shell microspheres were prepared by surface-initiated atom transfer radical polymerization with pre-crosslinked polyacrylamide as the core and non-crosslinked polyacrylamide as the shell. The obtained microspheres have diameters less than 1 μm with a few tens of nanometers shell thickness. The polymerization kinetics, number-average molecular weight and dispersity were investigated. The materials were characterized with infrared spectroscopy (IR), nuclear magnetic resonance (1H-NMR) spectroscopy, thermogravimetric analysis (TGA), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The viscosity and swelling property of materials were also investigated. The incremental oil recovery obtained with these microspheres is higher than that with polyacrylamide under the same conditions.