纠偏轨道设计的初始装置角允许值计算

在实钻过程中,纠偏轨道的设计参数必须满足一定的约束条件,才能设计出满足施工要求的纠偏轨道。以中靶约束为条件,建立了纠偏轨道设计参数的几何模型,推导出了单圆弧纠偏轨道设计参数的计算公式,给出了初始装置角允许取值范围上、下界限值的计算方法。通过算例验证了该算法的合理性和正确性,可将所有满足设计约束条件的初始装置角和井眼曲率绘制成设计参数允许取值范围图。当初始装置角和井眼曲率取值于该图的设计参数允许取值范围内,能够保证待钻设计轨迹满足井身参数的要求。本文的数学推理过程可进一步推广到定向井的圆形或椭圆形靶的情况,只需将圆弧平面与靶窗平面的交线扫过的范围修改成该交线与圆形或椭圆形靶的切点之间的范围。软件开发及其在实钻井眼轨迹监控中的应用表明,设计参数允许取值范围图可减少纠偏轨道设计的盲目性,提高设计质量。     

碎屑岩粒度分析中的子体参数拟合新方法

粒度分析方法在石油地质研究中,特别是储层沉积相研究中,有很广泛的用途。其中,粒度子体分离问题需要求解一个约束最小值问题,但是拟合目标函数具有函数值和导数矩阵不易计算、函数值多峰的特点,常规数值优化算法不易奏效。使用序贯数论网格优化算法(RSNTO)研究了粒度混合正态分布子体参数求解问题,考察了不同范数定义的拟合函数形式对子体参数求解的影响程度。以某油田铁5井深度储层S1+2样品粒度实验数据为算例,进行了数值试验。数值试验结果表明,RSNTO算法可以很好地解决子体参数拟合问题;并且,使用一致范数代替欧氏范数定义拟合目标函数,数值试验结果显示,前者的拟合效果在粒度中间值范围内更好一些,计算出来的累计百分含量曲线与实测点更贴近。     

绳套型水位流量关系曲线拟合模型的进一步优化

针对现有拟合定线方法存在过分依赖图表、模型参数求解繁杂及电算整编不便等问题,以稳定流的计算公式为基础,通过数学推演获得了可直接拟合河道受洪水涨落影响情况下的非恒定渐变流的水位流量关系方程式.实例应用结果表明,该方法能较好地拟合相应观测断面的水位流量关系,具有较好的拟合替代精度.     

压气机特性的系数拟合法

本文提出了一种压气机特性的拟合方法,以利于燃机变工况性能计算。利用压气机特性曲线的形状相近性及各曲线位置和形状随转速渐进变化的规律,以先后两步一元拟合过程来构成特性参数(如压比或效率),以其它二特性参数(如转速和流量)表示的代数多项式,从而确立了特性参数之间的函数关系,使变工况计算得以简化和提高精度。方法实用,精度较高。本文还分析了拟合过程中若干应注意的问题。     

基于多输出LSSVM的压气机特性的拟合和预测研究

采用最小二乘支持向量机进行了压气机特性拟合和预测研究,利用遗传算法对向量机的核参数和惩罚参数进行优化,提高建模精度,分析了已知特性数据的拟合精度,并对已知转速特性线上的未知数据、已知转速特性线之间的未知转速特性线、已知转速特性线之外的未知转速特性线进行预测,将预测结果与BP神经网络预测结果进行对比,表明最小二乘支持向量机法具有更高的预测精度,可满足工程仿真需求。     

基于网格变形的涡轮盘挡板结构形状优化方法

为了实现涡轮盘挡板结构的形状优化,需要对其形状进行参数化描述和设计,而传统的基于几何模型的参数化方法需要在优化过程中重复生成网格模型,不仅耗时而且难以保证网格质量,难以满足形状优化设计要求。因此,提出了一种基于网格变形技术的挡板结构形状优化方法。首先,建立了一种基于少量控制点驱动的网格变形技术,该技术在不改变CAD模型的情况下,通过控制点移动单元节点产生新的有限元模型;然后,以控制点位移作为设计变量,采用网格变形技术驱动挡板结构形状改变,高效地实现结构形状优化设计;最后,开展了航空发动机涡轮盘挡板结构形状优化设计,验证了所提出方法的有效性。数值结果表明,所提出的方法能够有效避免优化过程中的网格重剖分,提高了结构形状优化效率,获得了满足配合间隙要求的低应力涡轮盘挡板结构设计方案。     

弹性和柔性地基上动力人工边界及地震动输入方法

为完善粘弹性边界在弹性地基地震动输入中的应用,并实现柔性地基的地震动输入,系统研究了弹性和柔性地基上动力人工边界及其地震动输入方法,对均质弹性地基,分析了弹簧刚度系数不同取值方法、网格尺寸和模型截断边界范围的影响,在将底边界和侧边界均设置为粘弹性边界时,现行弹簧刚度系数的不同取值方法均可行,网格尺寸应小于波长的1/20,截断边界范围不需考虑上部结构尺寸;对规则水平成层柔性地基,底边界可设置为粘弹性边界,当侧边界设置为截断自由边界时截断边界宽度应不小于地基高度的15倍,当侧边界设置为粘弹性边界时截断边界宽度应不小于地基高度的2倍。对不规则成层柔性地基,底边界可设置为粘性边界,侧边界可设置为截断自由边界,其宽度应不小于地基高度的10倍。分析表明,这些动力人工边界的设置方法可将最大相对误差控制在5%左右,满足实际工程的精度要求。     

液滴表面张力修正系数与蒸汽膨胀速率和进口参数的相关性研究

蒸汽自发凝结过程具有明显的非平衡特性,对凝结过程的预测存在困难。基于非平衡凝结模型,采用表面张力修正系数来修正液滴表面张力,并对Laval喷管及平面叶栅内蒸汽自发凝结流动进行多工况数值模拟。分析了表面张力修正系数对蒸汽凝结流动模拟精度的影响,着重讨论表面张力修正系数的最佳取值与蒸汽膨胀速率、进口参数的相关性,并研究其随进口参数的变化规律。结果表明:相同工况下,表面张力修正系数最佳取值对蒸汽膨胀速率变化不敏感,与进口总温相关性不显著,而与进口总压呈显著正相关;基于数值计算结果,通过拟合出的表面张力修正系数最佳取值与进口总压的三次关系曲线,可在进口总压为1.5×10~4～9.8×10~4 Pa范围内确定表面张力修正系数最佳取值范围,为汽轮机低压级湿蒸汽流动数值模拟提供依据。     

汽轮机高中压排汽腔室参数化设计方法研究

高中压排汽腔室结构复杂,但影响流动损失的结构较少,可简化成轴对称的腔室形式。基于参数化建模,使用拉丁超立方抽样方法生成样本库,然后采用CFD方法计算所有样本点的气动性能,最后结合响应面分析方法拟合出了流动损失随各参数的变化规律。结果表明:采用三阶多项式拟合效果较好,标准差为0.071,拟合度相关系数为0.85;根据响应面拟合的多项式,可快速准确地评估出腔室的性能,省去了CFD仿真等繁琐步骤;同时基于该多项式,根据参数取值范围,也可快速优化腔室结构。研究成果可为汽轮机高中压腔室快速化设计提供参考。     

太阳电池直流模型的计算机仿真

太阳电池特性由材料、设计和工艺决定，太阳电池直流模型则可描述其电特性。现有的测试方法不能直接测出模型参数，但容易获得太阳电池片实测Ｉ—Ｖ数据，采用最小二乘法拟合出模型参数，就可以建立模型参数与制造工艺的直观联系。本文对提高模型拟合的速度及精度的实现方法进行讨论，在计算机上实现快速拟合。     

Performance assessment of some ice TES systems

In this paper, a performance assessment of four main types of ice storage techniques for space cooling purposes, namely ice slurry systems, ice-on-coil systems (both internal and external melt), and encapsulated ice systems is conducted. A detailed analysis, coupled with a case study based on the literature data, follows. The ice making techniques are compared on the basis of energy and exergy performance criteria including charging, discharging and storage efficiencies, which make up the ice storage and retrieval process. Losses due to heat leakage and irreversibilities from entropy generation are included. A vapor-compression refrigeration cycle with R134a as the working fluid provides the cooling load, while the analysis is performed in both a full storage and partial storage process, with comparisons between these two. In the case of full storage, the energy efficiencies associated with the charging and discharging processes are well over 98% in all cases, while the exergy efficiencies ranged from 46% to 76% for the charging cycle and 18% to 24% for the discharging cycle. For the partial storage systems, all energy and exergy efficiencies were slightly less than that for full storage, due to the increasing effect wall heat leakage has on the decreased storage volume and load. The results show that energy analyses alone do not provide much useful insight into system behavior, since the vast majority of losses in all processes are a result of entropy generation which results from system irreversibilities.     

Effect of co-cultivation of Chlamydomonas reinhardtii with Azotobacter chroococcum on hydrogen production

Chlamydomonas reinhardtii cc124 and Azotobacter chroococcum bacteria were co-cultured with a series of volume ratios and under a variety of light densities to determine the optimal culture conditions and to investigate the mechanism by which co-cultivation improves H₂ yield. The results demonstrated that the optimal culture conditions for the highest H₂ production of the combined system were a 1:40 vol ratio of bacterial cultures to algal cultures under 200 μE m^?2 s^?1. Under these conditions, the maximal H₂ yield was 255 μmol mg^?1 Chl, which was approximately 15.9-fold of the control. The reasons for the improvement in H₂ yield included decreased O₂ content, enhanced algal growth, and increased H₂ase activity and starch content of the combined system.     

Aerodynamic performance effects of leading-edge geometry in gas-turbine blades

The purpose of this paper is to illustrate the advantages of the direct surface-curvature distribution blade-design method, originally proposed by Korakianitis, for the leading-edge design of turbine blades, and by extension for other types of airfoil shapes. The leading edge shape is critical in the blade design process, and it is quite difficult to completely control with inverse, semi-inverse or other direct-design methods. The blade-design method is briefly reviewed, and then the effort is concentrated on smoothly blending the leading edge shape (circle or ellipse, etc.) with the main part of the blade surface, in a manner that avoids leading-edge flow-disturbance and flow-separation regions. Specifically in the leading edge region we return to the second-order (parabolic) construction line coupled with a revised smoothing equation between the leading-edge shape and the main part of the blade. The Hodson–Dominy blade has been used as an example to show the ability of this blade-design method to remove leading-edge separation bubbles in gas turbine blades and other airfoil shapes that have very sharp changes in curvature near the leading edge. An additional gas turbine blade example has been used to illustrate the ability of this method to design leading edge shapes that avoid leading-edge separation bubbles at off-design conditions. This gas turbine blade example has inlet flow angle 0°, outlet flow angle −64.3°, and tangential lift coefficient 1.045, in a region of parameters where the leading edge shape is critical for the overall blade performance. Computed results at incidences of −10°,   −5°,   +5°,   +10° are used to illustrate the complete removal of leading edge flow-disturbance regions, thus minimizing the possibility of leading-edge separation bubbles, while concurrently minimizing the stagnation pressure drop from inlet to outlet. These results using two difficult example cases of leading edge geometries illustrate the superiority and utility of this blade-design method when compared with other direct or inverse blade-design methods.     

Natural-gas fueled spark-ignition (SI) and compression-ignition (CI) engine performance and emissions

Natural gas is a fossil fuel that has been used and investigated extensively for use in spark-ignition (SI) and compression-ignition (CI) engines. Compared with conventional gasoline engines, SI engines using natural gas can run at higher compression ratios, thus producing higher thermal efficiencies but also increased nitrogen oxide (NO_x) emissions, while producing lower emissions of carbon dioxide (CO₂), unburned hydrocarbons (HC) and carbon monoxide (CO). These engines also produce relatively less power than gasoline-fueled engines because of the convergence of one or more of three factors: a reduction in volumetric efficiency due to natural-gas injection in the intake manifold; the lower stoichiometric fuel/air ratio of natural gas compared to gasoline; and the lower equivalence ratio at which these engines may be run in order to reduce NO_x emissions. High NO_x emissions, especially at high loads, reduce with exhaust gas recirculation (EGR). However, EGR rates above a maximum value result in misfire and erratic engine operation. Hydrogen gas addition increases this EGR threshold significantly. In addition, hydrogen increases the flame speed of the natural gas-hydrogen mixture. Power levels can be increased with supercharging or turbocharging and intercooling. Natural gas is used to power CI engines via the dual-fuel mode, where a high-cetane fuel is injected along with the natural gas in order to provide a source of ignition for the charge. Thermal efficiency levels compared with normal diesel-fueled CI-engine operation are generally maintained with dual-fuel operation, and smoke levels are reduced significantly. At the same time, lower NO_x and CO₂ emissions, as well as higher HC and CO emissions compared with normal CI-engine operation at low and intermediate loads are recorded. These trends are caused by the low charge temperature and increased ignition delay, resulting in low combustion temperatures. Another factor is insufficient penetration and distribution of the pilot fuel in the charge, resulting in a lack of ignition centers. EGR admission at low and intermediate loads increases combustion temperatures, lowering unburned HC and CO emissions. Larger pilot fuel quantities at these load levels and hydrogen gas addition can also help increase combustion efficiency. Power output is lower at certain conditions than diesel-fueled engines, for reasons similar to those affecting power output of SI engines. In both cases the power output can be maintained with direct injection. Overall, natural gas can be used in both engine types; however further refinement and optimization of engines and fuel-injection systems is needed.     

Exergetic evaluation of 5 biowastes-to-biofuels routes via gasification

This paper presents the exergy analysis results for the production of several biofuels, i.e., SNG (synthetic natural gas), methanol, Fischer–Tropsch fuels, hydrogen, as well as heat and electricity, from several biowastes generated in the Dutch province of Friesland, selected as one of the typical European regions. Biowastes have been classified in 5 virtual streams according to their ultimate and proximate analysis. All production chains have been modeled in Aspen Plus in order to analyze their technical performance. The common steps for all the production chains are: pre-treatment, gasification, gas cleaning, water–gas-shift reactions, catalytic reactors, final gas separation and upgrading. Optionally a gas turbine and steam turbines are used to produce heat and electricity from unconverted gas and heat removal, respectively. The results show that, in terms of mass conversion, methanol production seems to be the most efficient process for all the biowastes. SNG synthesis is preferred when exergetic efficiency is the objective parameter, but hydrogen process is more efficient when the performance is analyzed by means of the 1st Law of Thermodynamics. The main exergy losses account for the gasification section, except in the electricity and heat production chain, where the combined cycle is less efficient.     

Hydrogen production by steam-gasification of carbonaceous materials using concentrated solar energy – V. Reactor modeling,optimization, and scale-up

A chemical reactor for the steam-gasification of carbonaceous particles (e.g. coal, coke) is considered for using concentrated solar radiation as the energy source of high-temperature process heat. A two-phase reactor model that couples radiative, convective, and conductive heat transfer to the chemical kinetics is applied to optimize the reactor geometrical configuration and operational parameters (feedstock's initial particle size, feeding rates, and solar power input) for maximum reaction extent and solar-to-chemical energy conversion efficiency of a 5 kW prototype reactor and its scale-up to 300 kW. For the 300 kW reactor, complete reaction extent is predicted for an initial feedstock particle size up to 35 μm at residence times of less than 10 s and peak temperatures of 1818 K, yielding high-quality syngas with a calorific content that has been solar-upgraded by 19% over that of the petcoke gasified.     

液压系统常见的故障诊断及处理

任何工程机械式液压设备使用时出现故障是不可避免的。但是怎样确定故障的原因及找到好的解决方法,这是使用者最关心的问题。讲述了液压系统常见的故障及其排除方法。     

汽轮机数字电液调节系统挂闸异常的技术完善

分析了200MW汽轮机数字电液调节系统在运行中存在的挂闸异常问题,采取了相应的技术处理措施,且运行实践效果良好。     

新型高压共轨ECU升压模块的数字化开发与优化

为了提高喷油器电磁阀的响应速率,提出了一种基于CPLD(复杂可编程逻辑器件)应用于高压共轨ECU的数字升压模块。鉴于该升压电路结构参数多,其升压电压的恢复响应要求高等特征,基于Pspice建立了升压电路的仿真模型,研究了不同电路参数下升压模块的输出特性,全面优化了该升压模块的性能。结果显示,该升压模块的最大转换效率可以达90%以上。在柴油发动机上对ECU的试验表明,升压电压最大波动不超过10%,其恢复时间仅为1.3ms,功率管最大温升仅为41℃,满足整机运行范围内ECU的需求。     

Trace metal chemistry and silicification of microorganisms in geothermal sinter, Taupo Volcanic Zone, New Zealand

As part of a pilot study investigating the role of microorganisms in the immobilisation of As, Sb, B, Tl and Hg, the inorganic geochemistry of seven different active sinter deposits and their contact fluids were characterised. A comprehensive series of sequential extractions for a suite of trace elements was carried out on siliceous sinter and a mixed silica-carbonate sinter. The extractions showed whether metals were loosely exchangeable or bound to carbonate, oxide, organic or crystalline fractions. Hyperthermophilic microbial communities associated with sinters deposited from high temperature (92–94°C) fluids at a variety of geothermal sources were investigated using SEM. The rapidity and style of silicification of the hyperthermophiles can be correlated with the dissolved silica content of the fluid. Although high concentrations of Hg and Tl were found associated with the organic fraction of the sinters, there was no evidence to suggest that any of the heavy metals were associated preferentially with the hyperthermophiles at the high temperature (92–94°C) ends of the terrestrial thermal spring ecosystems studied.