Liquid penetration length of heptamethylnonane and trimethylpentane under unsteady in-cylinder conditions

While strategies employing early or late direct-injection of fuel can improve emissions, they also can lead to impingement of liquid-phase fuel on the piston and/or cylinder wall due to low in-cylinder temperatures and densities during the injection event. Previous work has shown that liquid-phase fuel films formed in this way can lead to pronounced degradations in efficiency and emissions. To avoid these problems, a quantitative understanding of fuel-property effects on the liquid penetration length is needed, and this understanding must include conditions where in-cylinder thermodynamic conditions and the injection rate vary with time. This work reports liquid penetration lengths measured in an optical engine under such time-varying conditions. Diagnostics included laser light scattering for measurement of the liquid length and conventional pressure-data acquisition for heat-release analysis. Unsteady liquid penetration was characterized for different injection timings, injection pressures, intake-manifold pressures, and fuel volatilities to gain an understanding of the relative importance of these factors. Fuel volatility was studied by using two fuels, 2,2,4,4,6,8,8-heptamethylnonane (HMN) and 2,2,4-trimethylpentane (TMP), which have very different volatility characteristics. Measured liquid lengths changed as in-cylinder conditions changed, with increasing temperature and density during the compression stroke causing a decrease in liquid length, and decreasing temperature and density during the expansion stroke causing an increase in liquid length. Intake-manifold pressure and fuel volatility were found to be primary factors governing liquid length. Heat loss from the charge gas to the engine and local charge cooling due to fuel vaporization were found to have a secondary influence on liquid length. Injection pressure was found to have little effect.     

在PCB中集成光数据流的制造

介绍了在PCB中采用埋入光互连波导形成集成光数据流的技术。     

Observed emotional involvement and overinvolvement in families of patients with bipolar disorder.

Many studies have examined the construct validity of the criticism component of expressed emotion, but little work has been done on clarifying the emotional overinvolvement (EOI) construct. In a sample of 115 recently episodic patients with bipolar disorder, the authors of the present study examined the construct validity of an observational coding system for both appropriate and inappropriate emotional involvement that permitted separate ratings for relatives' intrusiveness, self-sacrificing behaviors, and distress related to the patient's well-being. Findings support the measure's reliability and convergent validity and are moderately supportive of the measure's discriminant validity. Results also suggest that Camberwell Family Interview (C. E. Vaughn & J. P. Leff, 1976) EOI ratings do not discriminate among the different dimensions of the emotional involvement construct (or their appropriateness or inappropriateness) as revealed in laboratory-based interactions. The findings suggest that clinicians working with such families might consider differentiating among the various ways in which family members are involved with the patient and helping them learn to judge under what circumstances such involvement is appropriate and inappropriate. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

压力室结构对断油阶段空化及气体倒流的影响

断油阶段的空化现象对喷油间隔期的流场有重要影响,空化引起的高温燃气倒流会造成孔内结焦,进而影响缸内射流雾化.基于可视化试验和流体体积(VOF)方法两相三组分多相流求解器,对柴油喷嘴断油阶段的流动过程进行试验和模拟,分析3种不同压力室壁面曲率结构的喷嘴对断油阶段空化及气体倒流的影响.结果表明:在断油阶段喷孔和压力室依次发生空化现象,其中压力室内空化量较大,并呈现为涡空化和带状空化两种形态,壁面曲率小的狭直结构以带状空化为主;压力室结构较为狭直的喷嘴空化体积变大,但其低压持续时间延长使柴油流出量变小,最终导致倒流气体量下降;在发生涡空化时,速度梯度张量第二不变量Q与涡空化体积呈正相关,涡核区域越小则流场中磨擦耗散越少,越易于压力室内空化的形成.     

Identification of dominant oscillation mode using complex singular value decomposition method

In the bulk power system, most of the operating processes involve variations in both time and space. Therefore, characterization of low frequency oscillation from the aspects of temporal and spatial has great theoretical and practical significance. In this paper, complex-singular value decomposition (C-SVD) method is presented to explore the temporal evolution and spatial distribution of the dominant oscillation mode in the ensemble measurement matrix. Firstly, each variable in the ensemble matrix is separated into the trending component and the fluctuating component. The trending component is extracted by the band-pass filter or the moving average detrend method according to different conditions meanwhile the fluctuating component is extended to complex function form by Hilbert Transform. Then, the most energetic proper orthogonal mode (POM) and its temporal dynamic characteristic as well as spatial energy distribution relation are analyzed by C-SVD. Next, the energy contribution factor (ECF) is used to indicate the energy contribution degree of each node and the energy oscillation interface (EOI) is employed to identify the oscillation boundary. Finally, the validity and feasibility of proposed method are tested by the synthetic signal and actual measured data from Wide Area Measurement System (WAMS) in Chinese Northeast 500 kV transmission network.     

Optimization of a heavy-duty compression-ignition engine fueled with diesel and gasoline-like fuels

Optimal injection strategies for a heavy-duty compression-ignition engine fueled with diesel and gasoline-like fuels (#91 gasoline and E10) and operated under mid- and high-load conditions are investigated. A state-of-the-art engine CFD tool with detailed fuel chemistry was used to evaluate the engine performance and pollutant emissions. The CFD tools feature a recently developed efficient chemistry solver that allowed the optimization tasks to be completed in practical computer times. A Non-dominated Sorting Genetic Algorithm II (NSGA II) was coupled with the CFD tool to seek optimal combinations of injection system variables to achieve clean and efficient combustion. The optimization study identified several key parameters that influence engine performance. It was found that the fuel volatility and reactivity both play important roles at the mid-load condition, while the high-load condition is less sensitive to the fuel reactivity. However, high volatility fuels, such as gasoline and E10, were found to be beneficial to fuel economy at high-load. The study indicates that with an optimized injection system gasoline-like fuels are promising for heavy-duty CI engines due to their lower NOx and soot emissions and higher fuel economy compared to conventional diesel fuels. However, the high in-cylinder gas pressure rise rate associated with Partially Premixed Combustion of gasoline-like fuels can become problematic at high-load and the low-load operating limit is also a challenge. Potential solutions are discussed based on the present optimization results.