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排序方式: 共有262条查询结果,搜索用时 0 毫秒
1.
减阻水溶液槽道湍流特性POD分析 总被引:1,自引:0,他引:1
为进一步分析减阻水溶液湍流减阻机理,对质量分数为30×10-6十六烷基三甲基氯化铵(CTAC)水溶液槽道湍流减阻流动进行了实验研究,并基于本征正交分解方法研究减阻水溶液流动中减阻剂对流动结构的影响.结果表明:CTAC水溶液流动在不同雷诺数(15×104、25×104和35×104)下分别具有651%、700%和330%减阻效果;基于本征正交分解方法分析湍流脉动速度场,发现CTAC添加剂能够抑制湍流猝发过程中的低速流体的上喷及高速流体的下扫,即在一定程度上抑制了相干结构的发生及其发展过程,最终导致湍流减阻. 相似文献
2.
Large eddy simulation(LES)is used to calculate the in-cylinder turbulent flow field in a direct injection spark ignition(DISI)engine.The computations are carried out for three different maximum valve lifts(MVL)and throughout 100 consecutive engine cycles.The simulated results as well as corresponding particle image velocimetry(PIV)measurement database are analyzed by the proper orthogonal decomposition(POD)method.Through a new developed POD quadruple decomposition the instantaneous in-cylinder flow fields are decomposed into four parts,named mean field,coherent field,transition field and turbulent field,respectively.Then the in-cylinder turbulent flow characteristics and cycle-to-cycle variations(CCV)are studied separately upon the four part flow fields.Results indicate that each part exhibits its specific characteristics and has close connection with others.The mean part contains more than 50%of the total kinetic energy and the energy cascade phenomenon occurs among the four part fields;the coherent field part possesses the highest CCV level which dominates CCV of the bulk flow.In addition,it is observed that a change in MVL affects significantly the in-cylinder flow behavior including CCV,especially for the coherent part.Furthermore,the POD analysis demonstrates that at least 25 sample cycles for the mean velocity and 50 sample cycles for the RMS velocity are necessary for obtaining converged and correct results in CCV. 相似文献
3.
研究了外源NO和脱落酸(ABA)对杨树气孔运动和SOD、POD活性的影响。结果表明:NO和ABA均可诱导杨树叶片气孔关闭,且NO有加强ABA诱导气孔关闭的作用。NO清除剂(C—PTIO)能显抑制NO和ABA对气孔关闭的诱导效应。不同浓度硝普钠(SNP)和ABA处理杨树离体叶片,SOD活性变化不明显,POD活性受到显抑制。粗酶液的体外实验结果表明,不同浓度SNP对POD活性的抑制呈明显的浓度及时间效应;而ABA对POD活性则几乎没有影响。说明在ABA调控气孔运动的过程中需要NO的参与,由此推测ABA对杨树叶片气孔运动的调节与NO对POD的抑制有关。 相似文献
4.
为了分析船体形状对吊舱推进器的影响,研究了船后伴流中吊舱推进器的水动力性能.船后伴流用计算流体力学方法进行分析,吊舱推进器的水动力性能用面元法研究,吊舱和螺旋桨的相互影响用迭代方法求解,用蒙瑞诺解析公式计算螺旋桨和吊舱之间的诱导速度,结合船尾伴流的计算结果分析船尾伴流中吊舱推进器的水动力性能,并对船后不同位置吊舱推进器的水动力性能进行了比较.研究认为,船尾伴流会降低吊舱推进器的效率,吊舱推进器距离船体越远,效率越高. 相似文献
5.
Luciano J. Quitão-Teixeira Ingrid Aguiló-Aguayo Afonso M. Ramos Olga Martín-Belloso 《Food and Bioprocess Technology》2008,1(4):364-373
The effects of high-intensity pulsed electric fields (HIPEF) on oxidative enzymes and color of fresh carrot juice were studied.
A response surface methodology (RSM) was used to evaluate the effect of pulse polarity (mono or bipolar mode), pulse width
(from 1 to 7 μs), and pulse frequency (from 50 to 250 Hz) on color and peroxidase (POD) inactivation of carrot juice treated
by HIPEF. The total treatment time and the electric field strength were set at 1,000 μs and 35 kV/cm, respectively, at a temperature
below 35°C. The physicochemical characteristics of carrot juice were measured. There was a linear relationship between electrical
conductivity and temperature of the carrot juice. The results showed that HIPEF-treated carrot juice at 35 kV/cm for 1,000 μs
applying 6 μs pulse width at 200 Hz in bipolar mode led to 73.0% inactivation of POD. The color coordinates did not change
significantly. Therefore, HIPEF was effective in POD inactivation and carrot juice color preservation. 相似文献
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This paper presents the performance evaluation of power oscillation damping controller based on firefly algorithm (FA) parameter tuning. The power system stabilizer (PSS), unified power flow controller (UPFC), and static synchronous series compensator (SSSC) are tuned with FA by minimizing integral time multiplied by absolute error (ITAE) as an objective function. An integrated multi-stage linear quadratic regulator – power oscillation damping UPFC/SSSC has been proposed with precise tuning of control parameters which results in overall states' oscillation damping as compared to other classical methods. It has been observed that the proposed control structure damps the oscillations adequately and is modular in design methodology. The sample power system comprising six areas has been considered to demonstrate the effectiveness of the concept. The software has been developed based on the proposed work by the authors and the MATLAB code has been generated in R2009b version. The states' inter-relation which has been shown with eigenvalues reflects a better regulation and the step response is also validated. 相似文献
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10.
介绍了PLC和触摸屏(POD)的特点,以及触摸屏与PLC组成的步进电机控制系统的构成与功能.重点阐述触摸屏界面设计、PLC控制电机和PLC高速计数功能. 相似文献