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1.
连杆大头-曲柄销接触的三维有限元素法计算   总被引:11,自引:1,他引:10  
对常柴股份有限公司的ZS1110型柴油机连杆大头与曲柄销的接触问题作了三维有限元求解计算,并对轴-孔接触的实际接触边界、接触力作了研究。将计算得到的接触力作为曲柄销的力边界条件对曲轴结构强度进行分析,并与常规曲柄销力边界条件下的曲轴有限元计算结果进行了对比。  相似文献   

2.
本文利用ANSYS软件以4V-105柴油机中的连杆组件和曲柄销组成的连杆系统作为研究对象进行有限元分析,得到在压缩工况下和拉伸工况下柴油机连杆的等效应力和总位移分布云图,并通过和不同的连杆系统模型进行对比研究,得出此系统应力和位移相比其他系统小,从而为连杆组件的结构轻量化设计提供更大的优化空间。  相似文献   

3.
柴油机曲轴强度的三维有限元分析   总被引:6,自引:1,他引:5  
在I-DEAS9.0中,采用整体装配体模型,合理应用接触方法,精确模拟曲轴和机体、连杆和曲柄销之间的相互作用,对某大功率柴油机曲轴进行有限元分析。计算结果表明装配体模型具有较好的工程实用价值,为曲轴强度分析提供了新思路。  相似文献   

4.
建立了连杆组件完整的三维模型,包括模拟的活塞销及曲柄销来模拟连杆的大小头受力边界条件.通过施加接触来模拟各零件间的接触状态,通过设置接触之间的偏移量来模拟零件间的过盈及间隙量进行仿真分析.对连杆的受力进行试验测试,经与计算结果的对比表明:连杆仿真计算的边界条件及方法是合理的,仿真结果可信.最后,对连杆的疲劳安全特性进行了仿真计算及校核,结果证明连杆在工作过程中是安全的.  相似文献   

5.
柴油机连杆的大端孔径尺寸直接影响连杆瓦与曲柄销之间的油膜厚度。为分析三段式连杆的装配顺序对连杆大端孔孔径尺寸及大端孔变形程度的影响,本研究通过受力仿真分析和实测试验对比分析的方法,确定不同装配顺序下大端孔孔径尺寸的变化,分析连杆装配过程中的受力变形情况,确定了导致连杆大端孔径变化的根本原因为连杆受力变形后定位销与销孔的间隙差异,同时总结出有利于提高产品质量的三段式连杆装配方法。  相似文献   

6.
在考虑曲轴主轴颈、曲柄臂和连杆轴颈的变形以及重力对臂距差影响的基础上,利用有限元分析工具,改进了传统的利用测量臂距差调整曲轴中心轴线的方法。该方法利用ANSYS软件对每个曲拐进行静力分析,从而建立主轴颈偏移量和臂距差之间关系,得到了臂距差关于轴颈偏移量的解析表达式,与传统的经验公式相比较,计算更加方便、快捷和精确。  相似文献   

7.
连杆小头—活塞销接触的三维有限元素法计算   总被引:1,自引:0,他引:1  
陆威仑 《内燃机学报》1989,7(3):237-244
由于连杆孔—活塞销接触边界及载荷分布形式的不易确定,给连杆的有限元计算带来了困难。通常平面问题处理法假设的余弦或均布载荷常与实际不符,而平面接触解法则把销—活塞销孔与销—连杆孔接触的空间问题简化到了一个平面内,唯有三维接触解法才是最合理的。应用广泛的“SAP5”程序没有求解一般接触问题的自然功能。本文介绍了作者应用该程序求解柴油机连杆—活塞销三维接触问题的处理法,为三维未定边界接触问题的求解提出了一种行之有效的途径,并扩大了SAP5程序的应用范围。应用这种做法对E390柴油机连杆—活塞销三维接触作了计算。对销—孔接触的实际状态,接触边界、接触力等问题进行了研究。与运用“平面弹性接触有限元程序”计算的结果比较,两者接触状态相近。采用平面接触模型时在销直接作用区应力计算有较大误差。  相似文献   

8.
在发动机运行的过程中,连杆衬套受到活塞销交变载荷以及连杆自身的惯性力的作用.由于连杆小头和衬套的材料特性不同,其接触面上在承受相同的接触压力时会产生不同程度的变形,导致两接触体在接触面上相互错动,引起微动磨损,还会引起微动疲劳,这会导致连杆衬套过盈量不足,从而会对发动机造成严重的破坏.本文结合某型柴油机连杆小头和衬套的实际工况,利用接触力学理论和有限元方法,以分析衬套微动特性为目的对其接触过程进行数值有限元模拟分析.  相似文献   

9.
环氧树脂做成的单拐和双拐曲轴模型上有自由扭转和约束扭转负荷,在曲柄销上有径向力和切向力,在主轴颈上有轴向力、径向力和切向力偶。多数情况是用应力冻结方法固定变形,这比用直接加载更能详细和精确地进行测量。对于一个基本曲拐,在56个试验中,研究了曲柄臂形状变化的影响、主轴颈和曲柄销扭转角、曲柄臂开度以及主轴颈的倾斜度和位移。英国内燃机研究协会预测扭转变形的试验方法表明是可靠的。径向面弯曲变形可以用应变能计算方法来预测。  相似文献   

10.
连杆螺栓预紧力对连杆盖和连杆体的接合状态影响较大,为了保证有较好的接触压力,对连杆组件进行有限元数值分析。利用接触算法,重点分析从28~60kN范围内的13种不同的螺栓预紧力对连杆接触面、轴瓦接触面等的平均应力、应变值的变化情况。综合考虑各种情况,最终确定一个合适的螺栓预紧力,为设计人员提供了理论依据。  相似文献   

11.
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.  相似文献   

12.
正1 ABSTRACT To reduce the effect of global warming on our climate,the levels of CO2emissions should be reduced.One way to do this is to increase the efficiency of electricity production from fossil fuels.This will in turn reduce the amount of CO2emissions for a given power output.Using US practice for efficiency calculations,then a move from a typical US plant running at 37%efficiency to a 760℃/38.5 MPa(1 400/5 580 psi)plant running at 48%efficiency would reduce CO2emissions by 170kg/MW.hr or 25%.  相似文献   

13.
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 (NOx) 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 NOx emissions. High NOx 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 NOx 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.  相似文献   

14.
Performance assessment of some ice TES systems   总被引:1,自引:0,他引:1  
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.  相似文献   

15.
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.  相似文献   

16.
The thermal decomposition of limestone has been selected as a model reaction for developing and testing an atmospheric open solar reactor. The reactor consists of a cyclone gas/particle separator which has been modified to let the concentrated solar energy enter through a windowless aperture. The reacting particles are directly exposed to the solar irradiation. Experimentation with a 60 kW reactor prototype was conducted at PSI's 90m2 parabolic solar concentrator, in a continuous mode of operation. A counter-current flow heat exchanger was employed to preheat the reactants. Eighty five percent degree of calcination was obtained for cement raw material and 15% of the solar input was converted into chemical energy (enthalpy).The technical feasibility of the solar thermal decomposition of limestone was experimentally demonstrated. The use of solar energy as a source for high-temperature process heat offers the potential of reducing significantly the CO2 emissions from lime producing plants. Such a solar thermochemical process can find application in sunny rural areas for avoiding deforestation.  相似文献   

17.
18.
Hydrogen was produced from primary sewage biosolids via mesophilic anaerobic fermentation in a continuously fed bioreactor. Prior to fermentation the sewage biosolids were heated to 70 °C for 1 h to inactivate methanogens and during fermentation a cellulose degrading enzyme was added to improve substrate availability. Hydraulic retention times (HRT) of 18, 24, 36 and 48 h were evaluated for the duration of hydrogen production. Without sparging a hydraulic retention time of 24 h resulted in the longest period of hydrogen production (3 days), during which a hydrogen yield of 21.9 L H2 kg−1 VS added to the bioreactor was achieved. Methods of preventing the decline of hydrogen production during continuous fermentation were evaluated. Of the techniques evaluated using nitrogen gas to sparge the bioreactor contents proved to be more effective than flushing just the headspace of the bioreactor. Sparging at 0.06 L L min−1 successfully prevented a decline in hydrogen production and resulted in a yield of 27.0  L H2 kg−1 VS added, over a period of greater than 12 days or 12 HRT. The use of sparging also delayed the build up of acetic acid in the bioreactor, suggesting that it serves to inhibit homoacetogenesis and thus maintain hydrogen production.  相似文献   

19.
The physical aspects of the activation energy, in higher and high temperatures, of the metal creep process were examined. The research results of creep-rupture in a uniaxial stress state and the criterion of creep-rupture in biaxial stress states, at two temperatures, are then presented. For these studies creep-rupture, taking case iron as an example the energy and pseudoenergy activation was determined. For complex stress states the criterion of creep-rupture was taken to be Sdobyrev's, i.e. σred = σ1 β + (1 − β)σi, where: σ1-maximal principal stress, σi-stress intensity, β-material constant (at variable temperature β = β(T)). The methods of assessment of the material ageing grade are given in percentages of ageing of new material in the following mechanical properties: 1) creep strength in uniaxial stress state, 2) activation energy in uniaxial stress state, 3) criterion creep strength in complex stress states, 4) activation pseudoenergy in complex stress states. The methods 1) and 3) are the relatively simplest because they result from experimental investigations only at nominal temperature of the structure work, however, for methods 2) and 4) it is necessary to perform the experimental investigations at least at two temperatures.  相似文献   

20.
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.  相似文献   

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