汽油机燃用E10含水乙醇/汽油的试验研究

在高原地区开展了燃用含水乙醇/汽油混合燃料的试验研究。在汽油机上进行了纯汽油与掺比为10%含水乙醇(95%浓度)/汽油混合燃料的动力性、经济性和排放性能的对比试验。试验结果表明,E10混合燃料的稳定性良好;燃用E10含水乙醇/汽油混合燃料后,能保持发动机的原机动力性;在较低转速内,有效燃油消耗率有一定的上升,随着转速和负荷的提高,有效燃油消耗率的上升状况得到较好的改善;当量燃油消耗率明显低于原机水平;有效热效率得到不同程度的提高;怠速工况的CH和CO的排放有所改善。     

汽油机燃用E10含水乙醇/汽油的试验研究

在高原地区开展了燃用含水乙醇／汽油混合燃料的试验研究。在汽油机上进行了纯汽油与掺比为10％含水乙醇（95％浓度）／汽油混合燃料的动力性、经济性和排放性能的对比试验。试验结果表明，E10混合燃料的稳定性良好；燃用E10含水乙醇／汽油混合燃料后，能保持发动机的原机动力性；在较低转速内，有效燃油消耗率有一定的上升，随着转速和负荷的提高，有效燃油消耗率的上升状况得到较好的改善；当量燃油消耗率明显低于原机水平；有效热效率得到不同程度的提高；怠速工况的CH和CO的排放有所改善。     

不同含氧调合汽油燃料的整车及排放性能试验研究

将甲醇、乙醇、正丁醇和2,5-二甲基呋喃(DMF)分别与市售编号为92号汽油按照体积比为1∶9的比例混合,连同纯汽油组成M10、E10、B10、F10、G100 5种燃料,在一辆缸内直喷(GDI)乘用车上研究不同燃料对整车性能的影响。试验结果表明,在新欧洲驾驶循环(NEDC)下,丁醇混合燃料的百公里体积油耗和去除热值影响的当量油耗均是被测5种燃料中最低的,其余3种含氧燃料掺混后的百公里体积油耗和当量油耗均高于纯汽油燃料;除M10的CO排放比汽油低外,含氧汽油的CO和THC排放均高于汽油;掺混3种醇类燃料均能够降低NO_x排放,F10的NO_x排放与纯汽油相当;4种含氧汽油大幅降低了颗粒物质量和数量排放。向汽油中添加含氧燃料能够降低汽车在中高车速稳定运行时的油耗和排放,但添加含氧燃料后的汽油比纯汽油更加不适应低车速和起动工况。在动力性方面,4种含氧汽油均缩短了汽车的加速时间。     

不同掺氢比的HCNG燃料对天然气发动机怠速性能影响研究

为了研究在天然气中掺入不同体积比氢气对发动机怠速性能的影响,针对一台6缸天然气发动机开展了不同体积掺氢比的氢气/天然气混合燃料(HCNG)的怠速性能试验研究.试验证实掺氢后热效率提高,要达到相同的怠速转速可减少怠速旁通阀开度;在怠速情况下,掺氢使CH4、CO、NMHC排放下降,Nox排放上升,可通过点火提前角推迟来有效降低怠速Nox排放;在天然气中掺入适量氢气后有利于改善发动机怠速燃烧,从而增加怠速稳定性.在怠速条件下,掺氢后CO、CH4排放随转速升高先减小后增加;怠速转速升高,怠速稳定性变好.在天然气中掺入适量氢气后,发动机热效率提高,经济性改善.     

E10含水乙醇汽油对汽油机性能及排放的影响研究

采用自主研发的"复方两性乳化剂"进行了E10含水乙醇汽油(体积比为90%的90#汽油+10%的含水乙醇)稳定性研究。研究结果表明:乳化剂能有效改善含水乙醇汽油的稳定性,加入强化剂和防冻剂、提高乙醇浓度能够有效改善乳化含水乙醇汽油的低温稳定性。针对汽油机进行了燃用E10含水乙醇汽油混合燃料与原机的性能对比试验研究。试验结果表明:在未对汽油机作任何调整的情况下,燃用E10含水乙醇汽油混合燃料的动力性略低于原机。在经济性方面,燃油消耗率比原机有所上升,以热值计的当量燃油消耗率比原机有所改善。在尾气排放方面,燃用E10含水乙醇汽油时,CO排放在整个负荷范围内基本比原机低,CO排放得到改善;HC排放在整个负荷范围内都得到了改善,改善效果可达9%左右;NOx排放在低负荷时有所改善,随着负荷增加NOx排放变化不大。在怠速工况,CO、HC和NOx排放均获得改善。尾气排放产物在催化器中的转化效率与发动机工况有关。     

甲醇-汽油混合燃料对汽油机性能影响的试验研究

在一台多点电喷汽油机上,开展了燃用不同掺混比的甲醇-汽油混合燃料时发动机的经济性、排放特性研究。结果表明:电喷汽油机燃用低掺混比甲醇-汽油(小于30%)时,随着甲醇掺混比的增加,经济性有所改善,有效热效率明显提高;CO的排放有明显改善,中低负荷时HC排放有所改善,高负荷时HC排放增加,NOx排放相当,而怠速工况时,排放特性变差。     

电喷汽油机燃用丁醇-汽油混合燃料超细颗粒排放特性

对某未做任何结构调整的电控进气道多点喷射汽油机燃用国-Ⅳ汽油和纯丁醇,以及丁醇体积比分别为10%、15%、20%、50%、85%的汽油-丁醇混合燃料的超细颗粒排放特性进行了试验研究。研究结果表明:外特性及负荷特性下,与纯汽油相比,随所燃用的丁醇-汽油混合燃料中丁醇含量的升高,该机的超细颗粒物排放的总数量浓度和总质量浓度均有所增加,且在接近最大扭矩转速和试验转速的高负荷时最明显;超细颗粒物排数量增加主要是由其中的核模态颗粒排放数量增加引起的。     

电喷汽油机燃用丁醇-汽油混合燃料的非常规排放特性

对某电控进气道多点喷射汽油机燃用国-Ⅳ汽油、纯丁醇、丁醇体积混合比分别为10%、15%、20%、50%、85%的丁醇-汽油混合燃料的非常规排放特性进行了试验研究,试验时未对发动机进行任何改动。研究结果表明:发动机燃用丁醇-汽油混合燃料的动力性、SO2排放和温室气体排放降低,燃油消耗率和醛类排放增加,其降低或增加幅度随混合燃料中丁醇体积混合比的增加而增大。当丁醇体积比低于20%时发动机的醇类排放降低,当混合比例超过20%时发动机的醇类排放增大。在汽油中加入丁醇可以有效的降低燃油中的硫含量,降低发动机的硫氧化物和温室气体排放。     

汽油醇混合燃料发动机冷起动排放特性研究

随着国Ⅲ及以上排放法规的实施,对发动机冷起动过程排放的控制显得越来越重要.在一台3缸进气道喷射汽油机上开展了不同环境温度下醇类汽油混合燃料对冷机起动及其后怠速暖机过程排放特性的研究.研究中设计了一种新颖的排放采样系统,测量了冷起动和暖机过程的HC和CO排放.甲醇汽油与乙醇汽油混合燃料排放对比发现:甲醇汽油具有更加优良的冷起动排放性能.分别在环境温度为5℃、15℃和25℃时进行了甲醇汽油对冷机起动及怠速暖机过程排放特性影响的研究.研究表明:在相同的环境温度下,HC和CO排放随着试验燃油中甲醇添加比例的增加明显降低;甲醇汽油对发动机冷机起动及暖机阶段HC和CO排放的改善在温度较低时表现的更为明显,环境温度为5℃,发动机燃用M30时,HC排放可降低40%,CO可降低70%.     

EGR氛围下异丁醇和乙醇对直喷汽油机燃烧和排放的影响

在一台1.8,L直列4缸涡轮增压直喷汽油机上,分别燃用汽油、异丁醇占混合燃料的体积分数为20%(IB 20)、40%(IB 40)、乙醇体积分数为20%(E 20)和40%(E 40),保持转速和转矩不变、过量空气系数为1,在不同EGR率下分析异丁醇和乙醇汽油的燃烧和排放特性.结果表明:异丁醇和乙醇都会使火焰发展期延长;乙醇可以促进EGR氛围下的火焰传播,但会导致燃烧温度升高,有效热效率下降;异丁醇能够降低燃烧温度,提高有效热效率.部分负荷时,废气再循环(EGR)结合异丁醇可以实现更低的燃油消耗.异丁醇和乙醇均能降低THC和颗粒物数量浓度排放,但乙醇会使CO和NO_x排放增加.异丁醇可以在EGR的基础上进一步降低NO_x排放,降低颗粒物数量浓度排放的效果也优于乙醇,排放控制方面比乙醇更有优势.     

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.     

Contents in Volume 23,2014

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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.     

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%.     

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.     

Controls on the Karaha–Telaga Bodas geothermal reservoir,Indonesia

Karaha–Telaga Bodas is a partially vapor-dominated, fracture-controlled geothermal system located adjacent to Galunggung Volcano in western Java, Indonesia. The geothermal system consists of: (1) a caprock, ranging from several hundred to 1600 m in thickness, and characterized by a steep, conductive temperature gradient and low permeability; (2) an underlying vapor-dominated zone that extends below sea level; and (3) a deep liquid-dominated zone with measured temperatures up to 353 °C. Heat is provided by a tabular granodiorite stock encountered at about 3 km depth. A structural analysis of the geothermal system shows that the effective base of the reservoir is controlled either by the boundary between brittle and ductile deformational regimes or by the closure and collapse of fractures within volcanic rocks located above the brittle/ductile transition. The base of the caprock is determined by the distribution of initially low-permeability lithologies above the reservoir; the extent of pervasive clay alteration that has significantly reduced primary rock permeabilities; the distribution of secondary minerals deposited by descending waters; and, locally, by a downward change from a strike-slip to an extensional stress regime. Fluid-producing zones are controlled by both matrix and fracture permeabilities. High matrix permeabilities are associated with lacustrine, pyroclastic, and epiclastic deposits. Productive fractures are those showing the greatest tendency to slip and dilate under the present-day stress conditions. Although the reservoir appears to be in pressure communication across its length, fluid, and gas chemistries vary laterally, suggesting the presence of isolated convection cells.     

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.