540kW柴油发电机组噪声治理

柴油发电机组近年来广泛应用于高层综合办公楼和公用建筑作为备用供电的设备,它产生的噪声干扰应作治理.对540kW柴油发电机组的噪声频谱特性、综合治理的要求、治理方法、设计计算以及达到的实际效果作了介绍,可供参考.     

基于小波理论的复杂机械振动信号降噪分析

基于小波理论,针对典型旋转往复式机械——汽车发动机振动信号进行了降噪分析研究,提出了适合这类振动信号降噪的分析方法,并通过对实验数据的分析验证了该方法的正确性和有效性.该研究为对汽车发动机振动信号进行降噪处理,进而对其实施故障诊断提供了可靠的保障.     

Spectroscopic and chemical-kinetic analysis of the phases of HCCI autoignition and combustion for single- and two-stage ignition fuels

The temporal phases of autoignition and combustion in an HCCI engine have been investigated in both an all-metal engine and a matching optical engine. Gasoline, a primary reference fuel mixture (PRF80), and several representative real-fuel constituents were examined. Only PRF80, which is a two-stage ignition fuel, exhibited a “cool-flame” low-temperature heat-release (LTHR) phase. For all fuels, slow exothermic reactions occurring at intermediate temperatures raised the charge temperature to the hot-ignition point. In addition to the amount of LTHR, differences in this intermediate-temperature heat-release (ITHR) phase affect the fuel ignition quality. Chemiluminescence images of iso-octane show a weak and uniform light emission during this phase. This is followed by the main high-temperature heat-release (HTHR) phase. Finally, a “burnout” phase was observed, with very weak uniform emission and near-zero heat-release rate (HRR). To better understand these combustion phases, chemiluminescence spectroscopy and chemical-kinetic analysis were applied for the single-stage ignition fuel, iso-octane, and the two-stage fuel, PRF80. For both fuels, the spectrum obtained during the ITHR phase was dominated by formaldehyde chemiluminescence. This was similar to the LTHR spectrum of PRF80, but the emission intensity and the temperature were much higher, indicating differences between the ITHR and LTHR phases. Chemical-kinetic modeling clarified the differences and similarities between the LTHR and ITHR phases and the cause of the enhanced ITHR with PRF80. The HTHR spectra for both fuels were dominated by a broad CO continuum with some contribution from bands of HCO, CH, and OH. The modeling showed that the CO+O→CO₂+hν reaction responsible for the CO continuum emission tracks the HTHR well, explaining the strong correlation observed experimentally between the total chemiluminescence and HRR during the HTHR phase. It also showed that the CO continuum does not contribute to the ITHR and LTHR chemiluminescence. Bands of H₂O and O₂ in the red and IR regions were also detected during the HTHR, which the data indicated were most likely due to thermal excitation. The very weak light emission in the “burnout” phase also appeared to be thermal emission from H₂O and O₂.     

发动机飞轮转速的传递函数分析

就如何分析曲轴的扭振对飞轮瞬时转速的影响进行了探讨。提出了采用各缸转矩到飞轮转速的传递函数分析新方法,并对各缸传递函数的分布特点进行了研究。在曲轴角度域及其频率域内建立了离散的弹性曲轴模型,利用该模型与刚性曲轴模型的飞轮输出响应对比,研究了发动机各缸不均匀与扭振对飞轮转速波动的相互关系。结果表明：扭振在高速工况下的影响较大,且当各缸工作不均匀程度较大时,其影响相对较小。     

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。     

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.     

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.     

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。     

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.     

椭圆—幂函数组合凸轮动力学优化设计

本文以椭圆幂函数凸轮型线建立动力学优化设计的数学模型。在设计中将整个配气机构简化成单质点振动模型,用龙格—库塔法求解数值。为了节省机时,选用一种新的优化方法——浮动正交网格法进行优化处理。这种方法也可用于其它凸轮型线的设计。