共查询到20条相似文献，搜索用时 15 毫秒
1.
A basic thermodynamic cycle for the production of mechanical power from materials that may be made to contract forcibly and reversibly is described. The cycle differs from existing mechanical power cycles which generally employ expanding fluid as working substances. A "contraction turbine" operating on this cycle has been devised, which has collagen fiber as its working substance and salt solution as fuel and produces mechanical work directly from chemical free energy. Direct conversion of chemical to mechanical energy is routinely effected in muscle but not in usual man-made engines. 相似文献
2.
Thermal barrier coatings for gas-turbine engine applications 总被引：6，自引：0，他引：6
Hundreds of different types of coatings are used to protect a variety of structural engineering materials from corrosion, wear, and erosion, and to provide lubrication and thermal insulation. Of all these, thermal barrier coatings (TBCs) have the most complex structure and must operate in the most demanding high-temperature environment of aircraft and industrial gas-turbine engines. TBCs, which comprise metal and ceramic multilayers, insulate turbine and combustor engine components from the hot gas stream, and improve the durability and energy efficiency of these engines. Improvements in TBCs will require a better understanding of the complex changes in their structure and properties that occur under operating conditions that lead to their failure. The structure, properties, and failure mechanisms of TBCs are herein reviewed, together with a discussion of current limitations and future opportunities. 相似文献
3.
A review of research on low heat rejection engines, on cooperative efforts in the United States and abroad to incorporate ceramics in intermittent combustion engines, and on the use of ceramics in these engines is presented. The reduction of heat loss from the combustion chamber of diesel engines improves fuel efficiency only 3 or 4 percent. Some other gains may be possible from a smaller cooling system, recovery of exhaust energy, and improvements in aerodynamics. It is judged that designs of low heat rejection engines will have the greatest initial impact on armored combat vehicles. Organization, coordination, planning, and cooperation on R&D for the use of ceramics in intermittent combustion engines appear to be greater abroad than in the United States. 相似文献
4.
杨张利 《西南大学学报(自然科学版)》2018,40(8):172-176
针对车用燃气发动机空燃比难于实时精确控制,探讨了一种最优空燃比融合控制策略.首先分析了燃烧室的控制论特性,研究了优化的控制策略,基于HSIC动静态特性与误差特征识别模型,构造了基于HSIC控制算法.在Matlab环境下,分别采用基于仿人智能融合控制与Smith最优PID控制的算法作了仿真对比研究,系统响应验证了融合控制算法优于Smith最优PID控制策略.仿真结果表明,采用融合控制算法实现对燃气发动机的最优空燃比控制是合理与可取的. 相似文献
5.
Miller BI 《Science (New York, N.Y.)》1967,157(3795):1389-1399
Tropical cyclones derive their energy from the release of latent heat of condensation; they have been compared to simple heat engines (6), although they are not very efficient ones since only about 3 percent or less of the heat released within the cyclone is converted into kinetic energy. Tropical cyclones are warm-core, direct circulations in the sense that ascent takes place at warmer temperatures than does descent, thus converting heat energy into potential energy and potential energy to kinetic energy. 相似文献
6.
The solar thermal energy stored in hydroelectric reservoir thermoclines is very large and greatly exceeds the gravitational hydroenergy of the surface water, even after limitations arising from the second law of thermodynamics have been taken into account. Greatly enhanced power production can be obtained at present hydroelectric facilities if heat engines are adapted to exploit this large thermal energy resource. 相似文献
7.
Materials and processing innovations that have been incorporated into the manufacture of critical components for high-performance aircraft gas turbine engines are described. The materials of interest are the nickel- and cobalt-base superalloys for turbine and burner sections of the engine, and titanium alloys and composites for compressor and fan sections of the engine. Advanced processing methods considered include directional solidification, hot isostatic pressing, superplastic foring, directional recrystallization, and diffusion brazing. Future trends in gas turbine technology are discussed in terms of materials availability, substitution, and further advances in air-cooled hardware. 相似文献
8.
Fundamental investigations of the chemical and physical properties of metal beta-diketonate complexes have revealed unusual volatility, as well as solvolytic and thermal stability and solubility in organic solvents. Certain general rules describing the volatility of metal beta-diketonates on the basis of ligand shell character and metal ion size have arisen from extensive gas chromatographic and vapor pressure studies. Several practical applications of volatile beta-diketonates teke advantage of their special properties. In ultratrace metal analysis by gas chromatography, use of these chelates has allowed the detection of smaller amounts of certain metals than can be detected by any other analytic method. Certain rare earth beta-diketonates have been found useful as antiknock additives in gasoline and as catalysts for the removal of carbonaceous deposits from the combustion chambers of internal combustion engines. 相似文献
9.
湿式气缸套穴蚀机理分析及预防措施 总被引：1，自引：0，他引：1
发动机是机车的“心脏”,气缸套又是决定发动机寿命的重要零件。本文针对湿式气缸套出现穴蚀这一缺陷进行描述,并对穴蚀产生的过程进行了力学分析,找出其影响因素,提出了对湿式气缸套来说预防穴蚀产生的几条措施,目的为延长气缸套的使用寿命,即延长发动机的使用寿命。 相似文献
10.
复杂技术创新是发展中国家进行产业结构升级的一个重要努力方向，也是我国实施自主创新战略的重要方面。高度不确定性是复杂技术创新的主要特征，如何从创新模式及组织形式等方面减少创新过程的不确定性，成为复杂技术创新管理的关键所在。复杂技术创新过程中需要多种知识和技能并且需要创造新知识，创新主体对知识资源的获取成为复杂技术创新不确定性的主要来源。自组织网络能够有效降低这种不确定性，从而促进复杂技术创新。 相似文献
11.
为了解内燃机气缸盖气门处的漏气现象,对气缸盖的残余应力进行了实验研究。对不同热处理工艺进行时效处理的气缸盖分别采用切割法和钻孔法测定其残余应力,得到了如下的初步结果: 1.充分时效热处理可以大大降低残余应力; 2.即使是充分时效热处理,也不足以防止由于气门附近的不均匀变形而产生的畸变。这种畸变是导致漏气的主要原因。 因此,为解决漏气问题,除了应改进热处理时效工艺外,还需从气缸盖结构和铸造工艺上进一步探讨研究。 相似文献
12.
Koziol K Vilatela J Moisala A Motta M Cunniff P Sennett M Windle A 《Science (New York, N.Y.)》2007,318(5858):1892-1895
With their impressive individual properties, carbon nanotubes should form high-performance fibers. We explored the roles of nanotube length and structure, fiber density, and nanotube orientation in achieving optimum mechanical properties. We found that carbon nanotube fiber, spun directly and continuously from gas phase as an aerogel, combines high strength and high stiffness (axial elastic modulus), with an energy to breakage (toughness) considerably greater than that of any commercial high-strength fiber. Different levels of carbon nanotube orientation, fiber density, and mechanical properties can be achieved by drawing the aerogel at various winding rates. The mechanical data obtained demonstrate the considerable potential of carbon nanotube assemblies in the quest for maximal mechanical performance. The statistical aspects of the mechanical data reveal the deleterious effect of defects and indicate strategies for future work. 相似文献
13.
A review of advances for aircraft engine structural materials and processes is presented. Improved materials, such as superalloys, and the processes for making turbine disks and blades have had a major impact on the capability of modern gas turbine engines. New structural materials, notably composites and intermetallic materials, are emerging that will eventually further enhance engine performance, reduce engine weight, and thereby enable new aircraft systems. In the future, successful aerospace manufacturers will combine product design and materials excellence with improved manufacturing methods to increase production efficiency, enhance product quality, and decrease the engine development cycle time. 相似文献
14.
Burrows DN Romano P Falcone A Kobayashi S Zhang B Moretti A O'brien PT Goad MR Campana S Page KL Angelini L Barthelmy S Beardmore AP Capalbi M Chincarini G Cummings J Cusumano G Fox D Giommi P Hill JE Kennea JA Krimm H Mangano V Marshall F Mészáros P Morris DC Nousek JA Osborne JP Pagani C Perri M Tagliaferri G Wells AA Woosley S Gehrels N 《Science (New York, N.Y.)》2005,309(5742):1833-1835
Gamma-ray burst (GRB) afterglows have provided important clues to the nature of these massive explosive events, providing direct information on the nearby environment and indirect information on the central engine that powers the burst. We report the discovery of two bright x-ray flares in GRB afterglows, including a giant flare comparable in total energy to the burst itself, each peaking minutes after the burst. These strong, rapid x-ray flares imply that the central engines of the bursts have long periods of activity, with strong internal shocks continuing for hundreds of seconds after the gamma-ray emission has ended. 相似文献
15.
扫气压力对船用天然气/柴油双燃料发动机燃烧排放的影响 总被引：2，自引：0，他引：2
为研究扫气压力对缸内直喷船用双燃料发动机燃烧排放特性的影响规律,在通过试验数据对模型验证的基础上,采用有限容积法进行燃烧过程方程组的离散,同时采用半隐式法进行多变量耦合数值求解,分别就船用天然气/柴油双燃料发动机不同扫气压力对发动机缸内压力、缸内温度、缸内湍流和排放产物的影响进行了数值计算。结果表明:扫气压力的提高可导致缸内最大爆压增大,缸内最高温度与缸内湍流动能峰值降低;同时NO和CH~4排放量均随扫气压力的提高呈下降趋势;扫气压力每提高0.25 bar,缸内最大爆压平均升高5%,而缸内最高温度平均降低2.5%,缸内湍流动能峰值平均降低6.9%,NO排放量减少7.8%,CH~4排放量减少10.9%,扫气压力对CH~4排放的影响比对NO排放的影响更明显。研究表明,船用天然气/柴油双燃料发动机在运行过程中,应在发动机热负荷允许的范围内,尽可能采用高的扫气压力,以降低未燃CH~4和NO的排放,从而提升发动机的动力性和经济性。 相似文献
16.
We compare the energy efficiency of hybrid and fuel cell vehicles as well as conventional internal combustion engines. Our analysis indicates that fuel cell vehicles using hydrogen from fossil fuels offer no significant energy efficiency advantage over hybrid vehicles operating in an urban drive cycle. We conclude that priority should be placed on hybrid vehicles by industry and government. 相似文献
17.
用曲轴箱增压改善单缸四冲程柴油机性能的研究 总被引：2，自引：1，他引：2
在X195柴油机空气滤清器,进气管和曲轴箱之间增设单向阀片,利用活塞工作反面来泵气,把进入进气管道的新鲜空气与漏入曲轴箱内的气体一齐压入气缸,以达到增压,降低油耗,减少排放污染的目的。 相似文献
18.
Sachdev S 《Science (New York, N.Y.)》2000,288(5465):475-480
Small changes in an external parameter can often lead to dramatic qualitative changes in the lowest energy quantum mechanical ground state of a correlated electron system. In anisotropic crystals, such as the high-temperature superconductors where electron motion occurs primarily on a two-dimensional square lattice, the quantum critical point between two such lowest energy states has nontrivial emergent excitations that control the physics over a significant portion of the phase diagram. Nonzero temperature dynamic properties near quantum critical points are described, using simple theoretical models. Possible quantum phases and transitions in the two-dimensional electron gas on a square lattice are discussed. 相似文献
19.
本文探讨了搜索引擎的基本工作原理，并举例对中文搜索引擎诸如百度、雅虎等作了简介。 相似文献
20.
高原地区大气稀薄,空气压力相对较低,会影响发动机的过量空气系数和充量系数,同时,沼气相对天然气可燃成分甲烷含量低,会造成发动机功率下降。针对西北高原地区的特点,文章分析了几种柴油天然气双燃料发动机改装方案,对发动机供气系统、供油系统等进行设计研究,研究了一种能适用于该地区的、成本较低的柴油沼气双燃料发动机,提出了一种氢气高压直喷系统,可提高该发动机的动力性和对各种工况的强适应性,节省开发时间,降低成本。 相似文献