2125型柴油机球铁连杆的试验

本文通过2125型柴油机球铁连杆的静态应力试验和装机耐久试验,分析了在生产中采用这种连杆的可能性,并就连杆小头孔与活塞销的配合间隙对连杆小头应力分布的影响进行了初步探讨。     

基于随机边界元法的连杆可靠性分析

在确定性边界元数值方法的基础上,通过采用非统计逼近的处理方法建立了基于一阶二次矩法的二维弹性随机边界元数值方法的基本方程和可靠度分析公式,进一步运用开发的相应软件分析了内燃机连杆小头的应力数字特征量,并与采用蒙特卡洛随机模拟方法对连杆小头得到的随机应力数字特征量进行了比较,验证了本提出的方法的可靠性。在此基础上,对连杆小头疲劳强度可靠度进行了计算,结果表明本提出的方法不仅用于复杂结构的可靠度进     

基于多体动力学和有限元分析的汽油机连杆疲劳强度计算

基于AVL公司的Excite Power Unit软件进行连杆的多体动力学计算,得到连杆小头在发动机一个循环下的一维受力曲线,然后采用Abaqus软件进行连杆的有限元分析,得到连杆的三维应力分布,最后利用MSC.Fatigue软件导入多体动力学计算结果和有限元应力分布结果进行疲劳安全系数计算,得到疲劳安全系数的分布,从而为发动机连杆的优化设计建立基础。     

某柴油机连杆小头结构参数优化

针对某柴油机连杆小头结构,借助试验设计(DOE)技术,以接触面最大接触压力和支撑圆角最大压应力为评价指标,以衬套应力分布为约束条件,开展连杆小头关键特征参数优化分析,获得最优参数组合。实例分析表明:小头支撑厚度和支撑圆角半径是影响连杆小头运动副变形协调的主要因素。后续通过优化前后结构的EHD仿真及试验对比结果表明:最优参数结构可明显降低边缘接触压力,且接触应力分布更均匀。     

基于多体动力学的连杆强度分析

连杆作为发动机最重要的零部件之一,工作过程中受急剧变化的动载荷影响,容易发生断裂失效,必须具有较高的强度和可靠性。采用多体动力学仿真进行边界条件求解,确定连杆的最大压载荷和最大拉载荷,在此基础上进行静强度计算得到三个工况下的应力分布,计算出危险截面的安全系数。分析结果表明连杆在4000 r/min时承受载荷最大,在此工况下应力集中截面为连杆小头与杆身过渡处、连杆大头与杆身过渡处、油孔及小头孔内部下半部分,最大应力值为641Mpa,在材料许用应力范围内。几个危险截面中安全系数最小为1.34,设计安全,并具有一定的强度储备。     

连杆小头油孔对连杆疲劳寿命影响的研究

采用有限元方法对两种不同方案的连杆小头油孔 (单油孔方案和双油孔方案 )进行了分析。通过对其主要考查部位的应力、连杆大头、小头轴孔的纵、横向变形进行对比研究 ,并根据疲劳累积损伤原理对连杆各方案进行疲劳强度校核 ,发现双油孔连杆方案在变形和应力方面都有较好的改善。此外 ,还对双油孔连杆方案的两油孔夹角采用不同的角度 (5 0°和 6 0°)做了有限元分析对比 ,结果表明两油孔夹角为 6 0°时 ,油孔的位置恰好能避开连杆小头的高应力区。建议若条件允许 ,连杆小头最好采用双油孔方案 ,且油孔夹角取 6 0°左右为宜。     

配合间隙对连杆疲劳强度的影响

针对某型号连杆,利用应力测试方法,测量了不同活塞销与小头孔配合间隙下的应力。分析了不同间隙对小头过渡圆角处应力的影响程度,对连杆疲劳试验方法改进及结果评估提供参考。     

基于ABAQUS的连杆有限元分析

建立了发动机连杆机构的三维模型,使用ABAQUS软件对连杆模型进行有限元分析,得到了连杆在最大拉伸、最大压缩两种极限工况下的连杆的三维应力分布,确定了连杆工作的危险部位,最后使用疲劳软件进行疲劳分析,为连杆设计开发提供参考。     

创新型连杆结构对比分析

分别建立沿小头孔轴线杆身断面的传统连杆及垂直小头孔轴线杆身断面的新型连杆实体模型,运用ANSYS软件对传统连杆及新型连杆进行有限元静力分析。讨论了两种结构形式在结构强度和刚度上的差异,为连杆的创新型设计提供理论参考。     

带衬套的连杆小头整体边界元应力的分析

本文介绍了边界元法及其对不同材料的组合体和不同厚度的物体的分域处理过程和计算实例,然后应用该法对带衬套的内燃机连杆小头整体进行应力分析,并与按通常不带衬套的计算结果进行了比较。最后对连杆小头设计中的某些问题进行了讨论。     

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.     

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.     

Contents in Volume 23,2014

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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.     

Wind power for pumping: The development of the ITP windpump

Water pumping has been one of the main applications for wind power in the past and despite the spread of mains-electric pumps, more than a million windpumps remain in regular use. This paper reviews the general technical and economic requirements for pumping water using wind energy and by way of example gives an overview of the development of the new ITP wind-pump. It then considers the future prospects for this kind of technology.     

Methods of creating solar-reflective nonwhite surfaces and their application to residential roofing materials

We describe methods for creating solar-reflective nonwhite surfaces and their application to a wide variety of residential roofing materials, including metal, clay tile, concrete tile, wood, and asphalt shingle. Reflectance in the near-infrared (NIR) spectrum (0.7–2.5 μm) is maximized by coloring a topcoat with pigments that weakly absorb and (optionally) strongly backscatter NIR radiation, and by adding an NIR-reflective basecoat (e.g., one colored with titanium dioxide rutile white) if both the topcoat and the substrate weakly reflect NIR radiation. Coated steel and glazed clay-tile roofing products achieved NIR reflectances of up to 0.50 and 0.75, respectively, using only cool topcoats. Gray-cement concrete tiles achieved NIR reflectances as high as 0.60 with coatings colored by NIR-scattering pigments. Such tiles could attain NIR reflectances of up to 0.85 by overlaying a white basecoat with a topcoat colored by NIR-transparent organic pigments. Granule-surfaced asphalt shingles achieved NIR reflectances as high as 0.45 when the granules were covered with a white basecoat and a cool color topcoat.     

Thermal decay of an initially hot isothermal water body with application to thermal energy storage

The thermal decay of an initially hot isothermal water body contained in a tank was studied. Analytical solutions (including a group-theoretic solution) were obtained for the one-dimensional heat conduction equation with heat loss from the sides of the tank. The convective heat transfer coefficient was assumed not to be constant over the surface of the tank but to vary with space and time. A very good agreement was obtained between the group-theoretic solution and a numerical solution using the Crank-Nicholson finite difference scheme. The analytical results are discussed in terms of the underlying physical mechanisms.     

Ash-forming elements in four Scandinavian wood species. Part 1: Summer harvest

Woody biomass in Finland and Sweden comprises mainly four wood species: spruce, pine, birch and aspen. To study the ash, which may cause problems for the combustion device, one tree of each species were cut down and prepared for comparisons with fuel samples. Well-defined samples of wood, bark and foliage were analyzed on 11 ash-forming elements: Si, Al, Fe, Ca, Mg, Mn, Na, K, P, S and Cl. The ash content in the wood tissues (0.2–0.7%) was low compared to the ash content in the bark tissues (1.9–6.4%) and the foliage (2.4–7.7%). The woods’ content of ash-forming elements was consequently low; the highest contents were of Ca (410–1340 ppm) and K (200–1310), followed by Mg (70–290), Mn (15–240) and P (0–350). Present in the wood was also Si (50–190), S (50–200) and Cl (30–110). The bark tissues showed much higher element contents; Ca (4800–19,100 ppm) and K (1600–6400) were the dominating elements, followed by Mg (210–2400), P (210–1200), Mn (110–1100) and S (310–750), but the Cl contents (40–330) were only moderately higher in the bark than in the wood. The young foliage (shoots and deciduous leaves) had the highest K (7100–25,000 ppm), P (1600–5300) and S (1100–2600) contents of all tissues, while the shoots of spruce had the highest Cl contents (820–1360) and its needles the highest Si content (5000–11,300). This paper presented a new approach in fuel characterization: the method excludes the presence of impurities, and focus on different categories of plant tissues. This made it possible to discuss the contents of ash element in a wide spectrum of fuel-types, which are of large importance for the energy production in Finland and Sweden.