Part Load Performance Characteristics of a Low-Heat Rejection Diesel Engine Fueled with Biodiesel

This experimental study focused on improving performance characteristics of a low-heat rejection (LHR) diesel engine operating with biodiesel fuel. To ensure LHR conditions, the cylinder head and valves of the test engine were coated with a Y2O3-ZrO2 (yttria-stabilized zirconia) layer of 0.35?mm thickness over a NiCrAl bond coat of 0.15?mm thickness. The fuel used in the engine tests was produced from sunflower oil with transesterification methods. The engine test results showed that brake-specific fuel consumption (BSFC) and brake thermal efficiency were improved with biodiesel usage and thermal barrier coating (TBC) application. Further, exhaust gas temperature was decreased with use of biodiesel, while it was increased with TBC application.     

基于建构主义理论《搜索引擎》教学设计

以<搜索引擎>为例,研究了计算机教学中运用建构主义理论的设计原则,更为行之有效地开展教学工作,提高学生的学习积极性、生动性和创新能力的培养,从而达到良好的教学效果.     

Dynamic Loads in the Fan Containment Structure of a Turbofan Engine

In accordance with the FAA certification requirements, all modern commercial turbofan engines must successfully demonstrate its ability to withstand a fan blade-out (FBO) event through actual test. Possibility of losing a rotating fan blade from a running engine is a flight safety consideration, which must be addressed during the design phase of the engine. A typical fan blade-out event involves very complex nonlinear transient dynamics with large deflection of the release blade and rigid body rotation of the trailing blade as well as progressive failure and fragmentation of various components. Due to the nature of the impact type loading, the solution to the problem should also address dependence of the material behavior such as yield strength as a function of strain rates. In short, the transient dynamic analysis of a fan blade-out event highlights the complexity of the numerical technique, which includes all the nonlinearities of structural dynamics: plastic behavior of the materials, large displacements, and contact interaction between structural elements. In this paper, we present the results of a LS-DYNA simulation of a FBO event on a full-engine analytical model, which covers both the primary as well as secondary damages.     

Investigation of Extreme-Pressure and Antiwear Properties of Antimony Thioantimonate

Detailed studies including synthesis, characterization and evaluation of antimony thioantimonate, SbSbS₁, have been carried out. The amorphorus complex chalcogenide was prepared by a solution precipitation method. As a solid-lubricant additive in various greases, this material exhibits superior extreme-pressure and antiwear properties as demonstrated by the Four-Ball weld points and load-wear indexes on both AISI-52100 and AISI-440C steels. Antimony thioantimonate appears to be compatible with all the base greases investigated including a silicone grease in which very few additives show good response.     

Ignition control of methane fueled homogeneous charge compression ignition engines using additives

Homogeneous charge compression ignition is a new combustion technology that may develop as an alternative to diesel engines with high efficiency and low NO_x and particulate matter emissions. In this paper, the effect of additives such as dimethyl ether (DME), formaldehyde (CH₂O) and hydrogen peroxide (H₂O₂) for the control of ignition in natural-gas HCCI engines have been investigated numerically by adopting a single-zone zero-dimensional model. The chemical kinetic mechanism incorporated the GRI-3.0 mechanism that considers 53 species and 325 reactions together with the DME reaction scheme consisting of 79 species and 351 reactions. To simulate HCCI engine cycles, a variable volume computation has been performed by including a piston motion into the SENKIN code at a fixed equivalence ratio of 0.3 and initial mixture pressure of 1.5 bar. It was found that an additive-free mixture did not ignite for the intake temperature of 400 K. A mixture containing a small quantity of additives at the same temperature was ignited. For a fixed quantity of additive, it was found that H₂O₂ addition was effective in advancing the ignition timing as compared to the other two additives. It was found that the percentage of additives required to achieve a near TDC ignition timing increases linearly with the increase in the engine speed while decreases with the increase in the equivalence ratio with the superiority of H₂O₂. Furthermore, the addition of even 7% by volume of H₂O₂ could ignite a mixture at an intake temperature of 350 K, while at least the fractions of 12.5% and 35% by volume were needed for DME and CH₂O, respectively. It was also found that the mass fraction of NO with CH₂O addition was less than that with H₂O₂ addition. At the same time, however, a near TDC ignition timing resulted in a similar amount of NO for both additives. Overall, the enhanced reactivity of CH₄ in the presence of small amounts of additives could be used in HCCI engines fueled with methane to alleviate the high intake temperature requirements.     

一种新结构的油耗自动测量系统

本文介绍一种新结构的油耗自动测量系统,它用重量法测量,但摒除了传统的天平装置,而采用无任何机械运动机构的变送装置。文章提出了该测量系统的理论依据和具体结构原理,并介绍了一个实用测量系统,分析了精度、分辨率,论证了该系统在柴油机油耗测试中的应用价值。     

研究柴油机传热的表面温度法

本文介绍了一种柴油机燃烧室瞬态传热的实验研究方法——表面温度法。通过实测柴油机燃烧室表面的瞬态温度与平均热流,较准确地确定柴油机燃烧室局部表面的瞬态热流。文中从理论和实测两个方面分析了作者研制的表面瞬态温度传感器——薄膜热电偶的动态特性,介绍了柴油机燃烧室表面瞬态温度与传热的研究工作。     

内燃机振动信号的混沌分形特性研究

运用分形及混沌理论对实测的内燃机各种振动信号进行了分析,计算了信号的Lyapnov指数及关维数。结果表明,缺盖振动混沌与确定性共存,而缸套,机身振动则为混沌振动,信号的关联维数可作为气阀机构诊断的一个诊断特征量。     

一台高强化柴油机排气噪声有源控制实验研究

柴油机噪声使操作人员工作环境恶化,长期还危害操作人员的身体健康。排气噪声对柴油机整机噪声贡献很大,本文设计了一套自适应有源噪声控制（Adaptive Active Noise Control）系统用于控制排气噪声,实验结果表明该系统效果良好。     

气缸套—活塞环摩擦副材料匹配的研究

作者对国产中小型柴油机缸套一活塞环摩擦副常用的典型材料,进行交替配对组成九种摩擦副,在一定的速度及滴油润滑条件下,以法向载荷及摩擦时间为参变量,考察它们的摩擦磨损性能。试验结果表明,合适的材料组配可以大大提高摩擦副的耐磨性能;摩擦系数随载荷而变化;在一定的载荷作用下,由于材料的塑性变形及石墨的润滑作用可使摩擦系数降低;摩擦系数与磨损量之间不能建立对应的函数关系;在合适的金相组织范围内较硬材质有较高耐磨性;活塞环材质硬度比缸套材质硬度较高时(本试验为40HB)摩擦副的磨损量最小;摩损系数也随载荷而变化。