深部地热流体温度场中稳态静水压力研究

通过流体空间势压、热动力压分析,认为流体空间存在等高等压、等势压面及流体循环。在天津市区地下,蓟县雾迷山组储层厚度大于2000m,流体循环条件好。研究表明,地热流体是通过储层下部由北向南径流的;HX-09以西存在地质-水热屏障,受其影响,流体溶解性总固体(TDS)西部比东部高,以东不存在地质-水热屏障,是流体向南径流的主要通道;使用势压分析数据处理方法,能够使圈出的势压降落漏斗与集中地热开采区分布一致(2700m深势压等值线图),这些可为地热监测数据处理、资源预测等提供方法和理论依据。

海水抽水蓄能电站地下厂房通风热压的回归计算式研究

为了简化水电站地下厂房自然通风模拟计算过程,本文详细分析了影响自然通风热压动力的各个因素,并选出通风量、主厂房散热量、室外空气温度为最主要的三个影响因素,进一步地,采用多元二次回归正交组合设计方法与自然通风网络计算方法,建立了计算热压的回归拟合关系式。并以大万山海水抽水蓄能电站为例,计算了其在不同因素水平下的热压值,并总结出了满足显著性要求的数学拟合关系式。结果表明,主厂房散热量与室外空气温度的交互作用项、以及室外温度的平方项对热压计算的影响作用可以忽略,利用建立的热压拟合关系式,当已知三个影响因素的取值情况时,能够较为准确地计算出热压的情况。

MATHEMATICAL MODEL OF ~4He QUANTUM INTERFEROMETER GYROSCOPE

The mathematical model of 4He quantum interferometer gyroscope is presented. The model includes the driven equation, the current equation and the position equation. Therefore, it can sufficiently describe the gyro- scope system. The driven equation shows the thermally driven gyroscope can work for a long time but the pres- sure driven one cannot. From the current equation, the superfluid currents passing through the weak link contain the AC currents which show the rotation flux, and other currents caused by drive. As shown in the position equa- tion, the displacement of diaphragm is the only detectable parameter in the gyroscope system. The model is tested by the simulations based on experimental parameters, and can be used to research performance of the gyroscope and analyse the gyroscope error.

Hot deformation behavior of Al-Zn-Mg-Cu-Zr aluminum alloys during compression at elevated temperature

The hot compression tests of Al-Zn-Mg-Cu-Zr aluminum alloys （7056 alloy and 7150 alloy） were performed in a temperature range from 300 to 450 °C and at strain rate range from 0.01 to 10 s-1. The results show that the true stress-true strain curves exhibit a peak stress at a critical strain, then the flow stresses decrease monotonically until high strains, showing a dynamic flow softening. The peak stresses depend on the temperature compensated strain rate, which can be represented by the Zener-Hollomon parameter Z in the hyperbolic-sine equation with hot deformation activation energy of 244.64 kJ/mol for 7056 alloy and 229.75 kJ/mol for 7150 alloy, respectively, while the peak stresses for the former are lower than those for the latter under the similar compression condition. The deformed microstructures consist of a great amount of precipitates within subgrains in the elongated grains at high Z value and exhibit well formed subgrains in the recrystallized grains at low Z value. The smaller subgrains and greater density of fine precipitates in 7150 alloy are responsible for the high peak stresses because of the substructural strengthening and precipitating hardening compared with 7056 alloy.

NUMERICAL PREDICTION OF AIRCRAFT HYDRAULIC SYSTEM BASED ON THERMAL DYNAMIC ANALYSIS

A mathematical model of principal elements of the aircraft hydraulic system is presented based on the heat transfer theory. The dynamic heat transfer process of the hydraulic oil and the pump shells within an aircraft hydraulic system are analyzed by the difference method. A kind of means for the prediction to variational trends of the aircraft hydraulic system temperature is provided during operation. The numerical prediction and simulation under the operational conditions are presented for ground trial running and the decelerated operation in flight. Computational results show that there is a good coincidence between the experimental data and the numerical predictions.

Flow behavior and microstructure evolution of 6A82 aluminium alloy with high copper content during hot compression deformation at elevated temperatures

The flow behavior and microstructure evolution of 6A82 aluminum alloy (Al?Mg?Si?Cu) with high copper content were studied on a Gleeble?1500 system by isothermal hot compression test in the temperature range from 320 to 530 °C and the strain rate range from 0.001 to 10 s?1. The results reveal that the flow stress of the alloy exhibits a continuous flow softening behavior at low temperatures of 320?390 °C, whereas it reaches steady state at high temperatures (≥460°C), which are influenced greatly by the Zener?Hollomon parameter (Z) in the hyperbolic sine with the hot deformation activation energy of 325.12 kJ/mol. Microstructure characterizations show that prominent dynamic recrystallization and coarsening of dynamic precipitation may be responsible for the continuous flow softening behavior. Due to deformation heating at high strain rates (≥1 s?1), dynamic recrystallization is more prominent in the specimen deformed at 530 °C and 10 s?1 than in the specimen deformed at 460 °C and 0.1 s?1 even though they have very close lnZ values.

Microstructures and mechanical properties of Mg-Ce-Zn-Zr wrought alloy

Microstructures and mechanical properties of （Mg-2.0%Ce-0.7%Zn-0.7%Zr） alloy were studied. The results of scanning electron microscopy show that Mg12Ce phase mainly distributes at the grain boundaries. The fine (Mg12Ce) phase can apparently elevate recrystallization temperature by preventing the grain boundary migration. No dynamic recrystallization occurs during the hot-extrusion. The mechanical properties of as extruded specimens are （σb=278.5 MPa,） δ=12.0%, while those of the specimens annealed at 250 ℃ for 100 h are σb=（272.6 MPa,） δ=（11.3%,） which indicate that the alloy has good mechanical properties at room temperature.

Microstructure and mechanical properties of Al-6Zn-2.5Mg-1.8Cu alloy prepared by squeeze casting and solid hot extrusion

Al-6Zn-2.5Mg-1.8Cu alloy ingots were prepared by squeeze casting under different specific pressures,and the fresh ingot with best mechanical properties was solid hot extruded.With the increase of the specific pressure from 0 to 250 MPa,the dendrites became round and small.Because the applied pressure increased the solid solubility of alloying elements,the number of MgZn2 phases decreased.When the specific pressure increased from 250 MPa to 350 MPa,the grain size increased.After solid hot extrusion,the a（Al） grains were refined obviously and the MgZn2 phases were uniformly dispersed in the microstructure.After solid hot extrusion,the ultimate tensile strength was 605.67 MPa and the elongation was 8.1%,which were improved about 32.22%and15.71%,respectively,compared with those of the metal mold casting alloy.The fracture modes of the billet prepared by the metal mold casting and by squeeze casting were intergranular and quasi-cleavage fractures,respectively,whereas,that of the solid hot extrusion was mainly dimple fracture.The refined crystalline strengthening was the main reason to improve the strength and elongation of alloy.

Microstructure and mechanical properties of as-cast and extruded biomedical Mg-Zn-Y-Zr-Ca alloy at different temperatures

A type of biomedical magnesium alloy Mg-3Zn-1Y-0.6Zr-0.5Ca was cast and extruded at three extrusion temperatures of 270, 300 and 330 °C. The microstructure and mechanical properties of the cast and extruded alloys, tailored at different extrusion parameters, were investigated using tensile tests, optical microscopy, scanning electron microscopy, energy dispersive spectroscopy, X-ray diffractometry, transmission electron microscopy and electron backscattered diffraction. Optimum comprehensive mechanical properties are achieved in the alloy extruded at 270 °C, the ultimate tensile strength and the elongation reach 315 MPa and 26%, respectively, which is deemed to be associated with the grain refinement, weak basal texture and second phases strengthening. After hot extrusion, extensive dynamic recrystallization is found in the Mg-3Zn-1Y-0.6Zr-0.5Ca alloy. Continuous Mg3YZn6 phase bands are gradually broken into discontinuous chain-like or dot-like structures, and the grains distribute more uniformly. The as-extruded Mg-3Zn-1Y-0.6Zr-0.5Ca alloy exhibits a weak texture with (0001) basal planes parallel to the extrusion direction.

Configuration Consideration for Expander in Transcritical Carbon Dioxide Two-Stage Compression Cycle

To investigate the configuration consideration of expander in transcritical carbon dioxide two-stage compression cycle, the best place in the cycle should be searched for to reinvest the recovery work so as to improve the system efficiency. The expander and the compressor are connected to the same shaft and integrated into one unit, with the latter being driven by the former, thus the transfer loss and leakage loss can be decreased greatly. In these systems, the expander can be either connected with the first stage compressor (shortened as DCDL cycle) or the second stage compressor (shortened as DCDH cycle), but the two configuration ways can get different performances. By setting up theoretical model for two kinds of expander configuration ways in the transcritical carbon dioxide two-stage compression cycle, the first and the second laws of thermodynamics are used to analyze the coefficient of performance, exergy efficiency, inter-stage pressure, discharge temperature and exergy losses of each component for the two cycles. From the model results, the performance of DCDH cycle is better than that of DCDL cycle. The analysis results are indispensable to providing a theoretical basis for practical design and operating.

Flow stress behavior of Al-Cu-Li-Zr alloy containing Sc during hot compression deformation

The flow stress behavior of Al-3.5Cu-1.5Li-0.25(Sc+Zr) alloy during hot compression deformation was studied by isothermal compression test using Gleeble-1500 thermal-mechanical simulator. Compression tests were preformed in the temperature range of 653-773 K and in the strain rate range of 0.001-10 s-1 up to a true plastic strain of 0.7. The results indicate that the flow stress of the alloy increases with increasing strain rate at a given temperature,and decreases with increasing temperature at a given imposed strain rate. The relationship between the flow stress and the strain rate and the temperature was derived by analyzing the experimental data. The flow stress is in a hyperbolic sine relationship with the strain rate,and in an Arrhenius relationship with the temperature,which imply that the process of plastic deformation at an elevated temperature for this material is thermally activated. The flow stress of the alloy during the elevated temperature deformation can be represented by a Zener-Hollomon parameter with the inclusion of the Arrhenius term. The values of n,α and A in the analytical expressions of flow stress σ are fitted to be 5.62,0.019 MPa-1 and 1.51×1016 s-1,respectively. The hot deformation activation energy is 240.85 kJ/mol.

Shock resistance of supercharged boilers through integration with ship structure

The non-linear finite element software ABAQUS was used to simulate the dynamic response of a marine supercharged boiler when subjected to impact loading. Shock resistance was analyzed by the time-domain simulation method. After exhaustive simulations,the effect of air pressure induced by different working conditions on the shock response of a supercharged boiler was reviewed,leading to conclusions about the variability of structural response with different loading parameters. In order to simulate the real impulsive environments of supercharged boilers,the integration of equipment and ship structure was then primarily used to analyze shock response. These distinctly different equipment shock test methods,run under equivalent work conditions,were compared and the causes of discrepancy were analyzed. The main purpose of this paper is to present references for the anti-shock design of marine supercharged boilers.

Mechanical properties of Mg-Gd-Zr alloy by Nd addition combined with hot extrusion

The effect of Nd addition on the microstructure and mechanical properties of as-extruded Mg-9Gd-0.5Zr(wt.%) alloy was investigated. The Mg-9Gd-0.5Zr and Mg-9Gd-2Nd-0.5Zr alloys were extruded at 673 K. The elongated non-dynamic recrystallized(un-DRXed) grains disappear after adding Nd, and uniformly distributed dynamic recrystallized grains with a grain size of 1.68 μm were obtained in the alloy. In addition, numerous nano-Mg5(Gd,Nd)particles were found to precipitate dynamically in the Mg-9Gd-2Nd-0.5Zr alloy, which gave rise to the dynamic recrystallization process via providing nucleation energy through hindering the release of deformation energy and promoting an increase in the strength through the Orowan strengthening mechanism. Moreover, the dynamically recrystallized(DRXed) grains have a weak texture, which plays a significant role in improving the ductility. Therefore,the Nd addition favors the improvement of strength and elongation for the as-extruded Mg-9Gd-0.5Zr alloy,simultaneously.

Simulated Equations of State of MgSiO3 Perovskite

The equation of state of MgSiO3 perovskite under high pressure and high temperature is simulated using the molecular dynamics method. It was found that the molecular dynamics simulation is very successful in accurately reproducing the measured molar volumes of MgSiO3 perovskite over a wide range of temperatures and pressures. The simulated equation of state of MgSiO3 perovskite matched experimental data at up to 140GPa at 300K, as well as the fitting data of others and results from the first-principles simulation based on the local density approximation. The simulated equations of state of MgSiO3 perovskite at higher temperatures and higher pressures also correspond to the other calculations. In addition, the volume compression data of MgSiO3 perovskite is simulated up to 120 GPa at 300, 900, 2000 and 3000 K, respectively.

Effect of Si and Ti on dynamic recrystallization of high-performance Cu-15Ni-8Sn alloy during hot deformation

Effect of Si and Ti on dynamic recrystallization(DRX)of Cu-15Ni-8 Sn alloy was studied using hot compression tests over deformation temperature range of 750-950℃and strain rate range of 0.001-10 s^-1.The results show that the dynamic recrystallization behavior during hot deformation is significantly affected by the trace elements of Si and Ti.The addition of Si and Ti promotes the formation of Ni16Si7Ti6 particles during hot deformation,which promotes the nucleation of dynamic recrystallization by accelerating the transition from low-angle boundaries(LABs)to high-angle boundaries(HABs).Ni16Si7Ti6 particles further inhibit the growth of recrystallized grains through the pinning effect.Based on the dynamic recrystallization behavior,a processing map of the alloy is built up to obtain the optimal processing parameters.Guided by the processing map,a hot-extruded Cu-15 Ni-8Sn alloy with a fine-grained microstructure is obtained,which shows excellent elongation of 30%and ultimate tensile strength of 910 MPa.

Microstructural evolution,flow stress and constitutive modeling of Al−1.88Mg−0.18Sc−0.084Er alloy during hot compression

To explore the hot compression behavior and microstructural evolution,fine-grained Al−1.88Mg−0.18Sc−0.084Er(wt.%)aluminum alloy wires were fabricated with Castex(continuous casting−extrusion)and ECAP-Conform,and their hot compression behavior was investigated at temperatures of 673−793 K and strain rates of 0.001−10 s−1;the microstructures were characterized by optical microscope,X-ray diffractometer,transmission electron microscope,and electron backscattered diffractometer,and the flow stresses were obtained by thermal compression simulator.Microstructural evolution and flow curves reveal that dynamic recovery is the dominant softening mechanism.Continuous dynamic recrystallization followed by dynamic grain growth takes place at a temperature of 773 K and a strain rate of 0.001 s−1;the yielding drop phenomenon was discovered.Hyperbolic sine constitutive equation incorporating dislocation variables was presented,and a power law constitutive equation was established.The stress exponent is 3.262,and the activation energy for deformation is 154.465 kJ/mol,indicating that dislocation viscous glide is the dominant deformation mechanism.

CFD Analysis of Flow Characteristics of Corrugated Louvered Fins at Low Reynolds

A 2-D laminar flow model was established for CFD analysis of air-flow between louvered fins. Two louvered fins are studied based on commercial software FLUENT. Air-flow pressure drop characteristics are derived on the calculation of Reynolds number from 75.3 to 600. The numerical results are in good agreement with the experimental data when Reynolds is lower.

Characterizing pressure fluctuation into single-loop oscillating heat pipe

The pressure characteristics inside single loop oscillating heat pipe （OHP） having 4.5 mm inner diameter copper tube with the loop height of 440 mm were addressed. Distilled water was used as working fluid inside the OHP with different filling ratios of 40%, 60% and 80% of total inside volume. Experimental results show that the thermal characteristics are significantly inter-related with pressure fluctuations as well as pressure frequency. And the pressure frequency also depends upon the evaporator temperature that is maintained in the range of 60-96 ℃. Piezoresistive absolute pressure sensor （Model-Kistler 4045A5） was used to take data. The investigation shows that the filling ratio of 60% gives the highest inside pressure magnitude at maximum number of pressure frequency at any of set evaporator temperature and the lowest heat flow resistance is achieved at 60% filling ratio.

ANALYSES OF ERRORS IN MEDIUM-TERM NUMERICAL FORECAST PRODUCTS FOR THE SUBTROPICAL HIGH 1998

By statistic and dynamic analyses, we have come to the following conclusions: (1) The ECMWF medium-term numerical forecast can forecast medium-term activity of subtropical high, and the accuracy rate of forecast cannot have large improvement by translational corrections. (2) The important cause for the ECMWF medium-term numerical forecast to have errors in 1998 is that the astronomical tide is not included in the model. (3) Two indexes are found from which it can be judged that ECMWF medium-term numerical forecast will have errors if the astronomical tide is ignored in the model : ① When the 54.7?line under the moon of the nodical month astronomical singularities coincides with the trough-line of the subtropical jet flow from 50癊 to 150癊 on the 500 hPa level at 2000 L.T. of the same day, and is approximately vertical (α>60? with the isotherm, then the day 0 2 days after the appearance of the nodical month astronomical singularities is defined as the initial day. Then in three successive days after the initial day, ECMWF medium-term numerical forecast of the northern latitude of the 588 line at 120 癊 will have continuous errors as large as two latitudes (7/9). Otherwise, it won’t have continuous errors (13/13). ② Otherwise, if the 54.7 ?line is in the range of a low pressure between two high pressures, then there is a dispersive error on the day of the nodical month astronomical singularities (5/7). There is not any error (6/6) otherwise.

The Cold Vortex Circulation over Northeastern China and Regional Rainstorm Events

In this study,regional rainstorm events (RREs) in northeastern China associated with the activity of the Northeastern China Cold Vortex (NCCV) were investigated on a medium-range time scale.The RREs occurring in northeastern China could be categorized into three groups according to the distribution of heavy rainfall.The largest cluster is characterized by the rainstorm events that occur on the northwestern side of the Changbai Mountains along a southwest-northeast axis.These events occur most frequently during the post-meiyu period.The authors place particular emphasis on the RREs that belong to the largest cluster and are closely associated with the activity of the NCCV.These RREs were preconditioned by the transportation of substantial amounts of water vapor to which the anomalous western Pacific subtropical high (WPSH) contributed.The attendant anomalous WPSH was primarily driven by the anomalous transient eddy feedback forcing the nearby East Asian jet.The development of the NCCV circulation was concurrent with the RREs and acted as their primary causative factor.A perspective based on low-frequency dynamics indicates that Rossby wave packets emanated from the blocking-type circulation over northeastern Asia led to the development of the NCCV activity.