In the gas pipeline, the gas⁃solid two⁃phase flow causes erosion and wear on the inner wall of the pipeline, and the erosion wear in the tapered tube is particularly serious. Using the knowledge of computational fluid dynamics, the model was established by CFD simulation software, the fluid⁃solid two⁃way coupling equation was used, and standard k⁃ε model and discrete⁃phase model (DPM) were used for analysis. Investigating the influence of inlet flow velocity, solid particle size and particle mass flow rate on the wear and tear of reducing pipe, and predicting the location of the tapered tube where erosion wear is likely to occur and the optimum flow rate of natural gas. The results show that the inlet flow rate increased from 5 m/s to 25 m/s, the maximum erosion rate of the tapered tube increased first, then decreased and then increased. When the inlet flow rate is 15 m/s, the erosion rate reached the minimum, which is 1.76×10-6 kg/（m2•s）. The particle size increases from 0.5 mm to 4.5 mm, and the maximum erosion rate increases from 4.23×10-6 kg/（m2•s）to 7.56×10-6 kg/（m2•s）, and then gradually decreases to 2.68×10-6 kg/（m2•s）. The particle mass flow rate increases from 0.1 kg/s to 0.6 kg/s, when the inlet flow rate is 15 m/s, the maximum erosion rate increases from 1.76×10-6 kg/（m2•s） to 1.00×10-5 kg/（m2•s）. The erosion wear area is mainly located on the lower wall surface of the tapered tube throat, the lower wall of the tapered tube segment from the 2D region of the throat and the upper wall of the tapered tube segment outside the 2D region, and the erosion wear area of the upper wall surface is approximated by "U" type symmetrical distribution. During gas transfer, the optimum inlet flow rate of gas through the reducing pipeline should be 15 m/s. In order to prevent erosion and wear, it should also be noted that the particle size should not be too small, and the mass flow rate should be controlled within a reasonable range.

A betaine amphoteric surfactant was synthesized as a selfdirecting agent by oleic acid, 3-dimethylaminopropylamine(PDA) and sodium chloroacetate as the raw materials through a two-step reaction of condensation and quaternization. The effects of catalyst, raw material ratio, reaction temperature, reaction time and other factors on the conversion of oleic acid were investigated, and the optimum process conditions were determined. The synthetic product and the optimum additives form a clean self-diverting acid system which is uniformly stable, has a low viscosity of fresh acid and is easy to pump. When the mass fraction of HCl in the system drops to 3%, the viscosity of the system reaches 219 mPa·s. The acid system breaks when it encounters crude oil. The viscosity of the gel-breaking fluid is 3 mPa·s. There is no residue and it is easy to discharge back. The field application results show that the system has good steering effect and the effect of increasing production after putting into production is obvious.

 

When the crystal field exists, the mixed spin Ising model in nearest neighbor interaction with Fe4N structure was studied within the mean field theory. The theoretic expressions of magnetization and free energy in the nearest neighbor interaction system were deduced. The influences of the nearest interactions and the crystal field on the magnetic properties were mainly explored. The ground-state phase diagram and magnetization curves in finite temperature were obtained. Abundant phase transition characters were observed in the system: reentrantant phenomena, and second-order phase transitions. It is found that second-order phase transitions are general phenomena, and second-order phase transitions must exist in the system when DA/|J1| and DB/|J1| get the adequate large values. On the boundary lines of D1 to O1and D2 to O1、O2 reentrantant phenomena may occur.

Using the mean-field theory, numerical calculation expressions for the internal energy and specific heat were obtained, within the BC model considering the transverse high spin S=2 ferromagnetic system. The thermodynamic properties were investigated mainly nearby the phase transition points of the system, especially nearby the first-order phase transition points. The longitudinal crystal field dependence of the thermodynamic properties in the system was explored. It is found in the system that there is latent heat of phase transition only in very small crystal field range and the corresponding specific heat decrease suddenly, namely the first-order phase transition appears when the transverse field remains the same value. Then with the increase of crystal field, there is no hidden heat of phase transition in the system, the internal energy changes continuously and the corresponding specific heat suddenly decreases, namely the second-order phase transition appears. When the first order-order phase transition appears specific heat increases suddenly and when the second-order phase transition appears specific heat decreases suddenly. With the decrease of crystal field the internal energy increases and the specific heat decreases within the second-order phase transition range. The internal energy and the specific heat vary complexly within the first-order phase transition range.