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811.
借助CFD软件Star-CD,将基于β函数的概率密度函数方法应用于描述LPG发动机缸内不同区域的温度来模拟NOx的生成,同时考虑了缸内湍流场中组份和温度场的脉动。给出了在火花点火的燃烧方式下,LPG发动机在不同曲轴转角下缸内NOx的时空分布。计算和试验结果吻合良好。与其它PDF方法相比更趋理性,为研究和改善发动机的排放提供了参考。 相似文献
812.
[Objectives]Aiming at the current situation in which it is difficult to efficiently evaluate protection probability through traditional lightning rod evaluation methods, an efficient numerical evaluation algorithm is developed on the basis of an electrogeometric model (EGM) and attractive volume to realize the efficient calculation of lightning protection probability at any point in space.[Methods]This method first determines the attractive volume boundary of the lightning rod and protection object according to the interception process of the upward and downward leaders. The collection surface and exposure arc of the lightning stroke distance are then calculated, enabling the attractive risk and interception effect of the lightning rod to be quantified. Finally, the attraction and interception characteristics of the lightning rod are integrated to establish a numerical evaluation model of protection probability. To verify the accuracy of this method, the general rule of lightning rod protection probability is analyzed and the results compared with the existing analysis method.[Result]The evaluation results of this method show good agreement with those of classical leader progression model (LPM) theory.[Conclusions] The method proposed herein has a high degree of quantification and can realize the efficient calculation of lightning protection probability at any point in space, which can provide useful references for lightning protection design work. © 2023 Authors. All rights reserved. 相似文献
813.
轨道交通在发展过程中出现大量的超长线路,各省市在规划建设中也存在着诸多问题.通过对现有文献进行梳理,总结影响线路长度的主要因素,包括城市规划与城市形态、客流效益、经济效益和社会效益、时间和速度目标值、系统制式与运营组织及线路直达性等,确定超长线路的长度范围;在此基础上,统计国内城市轨道交通超长线路,对其特点进行分析;针... 相似文献
814.
水利行业在新阶段追求高质量发展的必要条件之一是加强水利建设工程施工安全管理。通过对近年来上海水利建设工程施工突出安全问题的统计及分析,从行业监督管理角度进行深入思考和总结,以期能够为水利工程施工安全监督管理提供思路启发。 相似文献
815.
A long-term fatigue assessment method based on EWP concept is proposed. ‘Equivalent wave probability (EWP)’ is the fictitious (HS, Tm)'s joint probability distribution function (JPDF), for which the frequency distribution of the stress variance R2, f(R2), calculated by spectral fatigue assessment agrees with the observed one. By choosing probability function p(R2) to fit f(R2), the R2's statistical model (R2SM) which represents the relation between the EWP parameters and R2's population parameters is developed, and the Bayesian inference, which can estimate the EWP parameters from the measured R2 data is developed. The EWP at the reference position (RP) can be determined by Bayesian inference from the measured R2 through the R2SM at RP. To accurately estimate the measured f(R2) at the target position (TP) from the EWP at RP, an R2SM correction factor at TP, denoted by αTP, is introduced in the process of assimilating R2SM. The resulting R2SM, which has been assimilated by Bayesian inference using measured data, is referred to as data-assimilated R2SM (DAR2SM). The fatigue assessment using EWP at RP as the input of DAR2SM at TP is called Bayes-EWP-DAR2SM analysis. The validity of Bayes-EWP-DAR2SM analysis is verified by using the long-term (about four years) multi(12)-position hull monitoring (HM) data of an 8,600TEU container ship. The fatigue damages estimated by Bayes-EWP-DAR2SM based solely on the stress history of a single sensor are in agreement with measurements with sufficient accuracy, independent of the chosen data assimilation period. This demonstrates that the multi-position fatigue assessment solely through HM at one RP based on EWP concept is realized. 相似文献
816.