特殊背压下高增压柴油机增压器匹配性能研究

基于GT-power搭建了某高增压柴油机一维仿真模型,并通过试验数据对模型进行标定。利用该模型计算分析了柴油机在不同排气背压下的性能,利用计算结果配合试验,分析了排气背压高且波动范围大工况下的压气机和涡轮的匹配。研究表明:背压升高会导致柴油机性能恶化,通过增压器的合理匹配可以实现高排气背压柴油机功率的恢复,稳态工况下可以恢复至59.8%,背压波动工况可以恢复至66%;高排气背压工况应提高压气机低压比区域的效率和流量,并适当控制高压比区域的压比;涡轮喷嘴环流通面积对性能影响较大,过大或过小均不利于功率恢复,通过选择合适的涡轮,可使功率恢复提升10.9%;柴油机性能参数随排气背压波动做规律波动,但存在一定的延迟,波动的幅值与该性能参数的迟滞时间负相关。     

涡轮增压器压气机性能优化设计与研究

从叶轮、扩压器、叶轮与压壳间隙3个方面对压气机性能进行了优化设计、计算与试验研究,结果表明,径斜流式叶轮压气机较径流式叶轮压气机效率更高,弧形出口扩压器压气机较平行直面出口压气机压比和效率更高,减少压气机叶轮与压壳间隙可改善压气机性能,同时减小增压器叶轮与压壳间隙和涡轮与涡轮壳间隙,可以改善增压器与发动机的匹配性能。     

小排量赛车发动机涡轮增压匹配计算及性能预测

遵照大学生方程式汽车大赛的有关规则,以某款0.6L汽油发动机为原型,经理论计算对涡轮增压器进行了选型.并应用GT-Power软件建立了发动机一维仿真模型,增加了进气限制器、涡轮增压器、中冷器和排气泄压阀等部分,进行了发动机和涡轮增压器的匹配计算与性能预测,结果表明二者匹配良好、达到了性能目标.此外,还针对规则要求加装了进气限制器,分析了该进气限制器对涡轮增压发动机的影响.最后,通过发动机台架试验获得发动机外特性曲线,验证了增压器与发动机匹配良好,仿真结果与台架试验结果基本相符.     

涡轮增压器热力学模型与柴油机动态仿真

建立了一种基于热力学定律的离心式压气机动态模型,该模型仅使用压气机的基本结构参数而不需要试验图谱。压气机模型与涡轮模型一起构成涡轮增压器动态模型,并与柴油机模型进行了联合匹配仿真。研究结果表明:该模型准确可信,扩大了压气机模型的工作范围,可有效改善柴油机模型在低负荷、低转速时的动态性能。模型计算速度快,实时性好,可用于柴油机性能优化、控制系统开发等多个领域。     

两区模型离心压气机性能预测方法研究

为获得有效的压气机性能预测方法,基于车用涡轮增压器压气机性能试验数据,重点研究了两区模型离心压气机性能预测及标定方法.研究结果表明:该预测方法仔细考虑了压气机内部扩散和损失过程,综合考虑逆压梯度黏性流动过程影响,标定方法简单实用,能方便地应用于工程设计;该性能预测方法也能有效预测涡轮增压器离心压气机流量特性及喘振、堵塞边界特性,能够反映出压气机的全工况性能;与试验结果相比,预测压比与试验压比差值小于3 %,预测绝热效率差值小于5 %,在高转速跨音速工况下预测喘振堵塞流量差值小于0.06.     

涡轮增压柴油机仿真模型修正方法及试验比较研究

基于AVL BOOST仿真软件,针对一台4缸涡轮增压柴油机进行建模,在原仿真模型的基础上着重考虑了涡轮增压器传热效应的影响。计算结果与发动机试验数据的比较分析表明:经过修正的发动机仿真模型在保证发动机扭矩、功率等主要性能参数不变的基础上,计算得到的涡轮及压气机进出口温差与原模型相比误差大幅度减小;同时修正后的仿真模型与原模型相比,新鲜空气的质量流量、涡轮膨胀比、压气机压比均无明显变化,表明修正后的模型并无改变涡轮增压器的工作点位置,仅修正了由于传热所导致的压气机出口和涡轮进口的温度变化,以及涡轮增压器的效率变化。     

16V396TE54船用电站柴油机优化匹配及试验研究

建立了16V396TE54柴油机仿真模型,针对该机型大排气背压和大进气阻力的使用工况,开展涡轮增压器和压缩比的优化匹配仿真分析,并进行了实机性能试验,二者结果相吻合,优化匹配后的柴油机各性能参数在要求的范围之内,能够满足在大排气背压和大进气阻力工况下使用的要求。     

车用涡轮增压器瞬态响应性评估与测试

基于车用涡轮增压器瞬态响应的影响因素，提出独立于内燃机的车用涡轮增压器瞬态响应评估指标D_x。通过数值模拟和试验的方法研究在不同终了转速下D_x随不同初始压比的变化以及转子转动惯量、涡轮效率和压气机效率对D_x影响。研究结果表明：试验结果与仿真结果吻合较好，证明该测试方法可用于涡轮增压器的瞬态性能测试以及增压器瞬态性能的影响因素研究。使用误差传播理论对试验测得的瞬态响应评估参数D_x值进行系统误差估计，试验测得的系统不确定度为1.35%。     

FSC赛车小型发动机涡轮增压匹配优化与性能预测

通过涡轮增压来提高FSC赛车的比功率。根据目标功率对涡轮增压器进行选型计算。通过GT-Power软件仿真对FSC赛车用450mL发动机进行了涡轮增压匹配分析。通过GT-Power数值模拟对涡轮增压器压气机尺寸进行优化,以提高增压器的综合效率和响应速度。匹配分析与仿真结果表明,对增压器压气机尺寸进行优化能够有效地改善从市场上挑选的增压器与FSC小型发动机匹配效果。通过匹配增压器并进行优化,赛车的比功率增加了44%。     

涡轮增压器轴向力分析与止推轴承承载力评估

为研究涡轮增压器止推轴承评估及选用方法,利用数值模拟建立某型号涡轮增压器的有限元模型,使用NUMECA软件对涡轮增压器轴向力进行分析,将轴向力结果输入DyRoBeS,计算止推轴承不同油楔面下的油膜厚度,选择承载能力满足要求的止推轴承,并进行压气机性能试验。结果表明:压比的仿真计算与试验结果基本一致,在低速工况下重合性较好,高速工况下最大误差小于1%;效率的仿真计算结果较试验略低,误差范围为0.5%-2.0%,但仿真与试验的总体趋势一致,在小流量范围内误差更小。该方法能够在增压器初步配试阶段较精确地选择止推轴承,提高整机可靠性。     

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.     

NEXT GENERATION ENGINEERED MATERIALS FOR ULTRA SUPERCRITICAL STEAM TURBINES

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%.     

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.     

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.     

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.     

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.     

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.     

Assessment methods of material ageing using Sdobyrev''s creep rupture model

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. σ_red = σ₁ β + (1 − β)σ_i, where: σ₁-maximal principal stress, σ_i-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.     

Production of hydrogen from sewage biosolids in a continuously fed bioreactor: Effect of hydraulic retention time and sparging

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.     

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。