The design of new Satellite Launch Vehicle （SLV） is of interest, especially when a combination of Solid and Liquid Propulsion is included. Proposed is a conceptual design and optimization technique for multistage Lo...The design of new Satellite Launch Vehicle （SLV） is of interest, especially when a combination of Solid and Liquid Propulsion is included. Proposed is a conceptual design and optimization technique for multistage Low Earth Orbit （LEO） bound SLV comprising of solid and liquid stages with the use of Genetic Algorithm （GA） as global optimizer. Convergence of GA is improved by introducing initial population based on the Design of Experiments （DOE） Technique. Latin Hypercube Sampling （LHS）-DOE is used for its good space filling properties. LHS is a stratified random procedure that provides an efficient way of sampling variables from their multivariate distributions. In SLV design minimum Gross Lift offWeight （GLOW） concept is traditionally being sought. Since the development costs tend to vary as a function of GLOW, this minimum GLOW is considered as a minimum development cost concept. The design approach is meaningful to initial design sizing purpose for its computational efficiency gives a quick insight into the vehicle performance prior to detailed design.展开更多
Monte Carlo(MC)法在目前边坡可靠度分析中是一种相对精确的方法,应用广泛,受问题限制的影响较小,适应性很强,其误差仅与标准差和样本容量有关。但其精度受随机抽样的可靠性和模拟次数制约,收敛速度慢,影响了实际使用。在极限平衡方法...Monte Carlo(MC)法在目前边坡可靠度分析中是一种相对精确的方法,应用广泛,受问题限制的影响较小,适应性很强,其误差仅与标准差和样本容量有关。但其精度受随机抽样的可靠性和模拟次数制约,收敛速度慢,影响了实际使用。在极限平衡方法的基础上,用拉丁超立方抽样(Latin hypercube sampling,LHS)方法代替MC法的随机抽样,考虑边坡参数的变异性和相关性进行边坡可靠度分析。讨论了LHS法、MC法中可靠指标的各种计算方法,建议以破坏概率、安全系数均值和标准差作为评价指标。算例显示LHS法较MC法效率上有很大改善:较少的抽样样本就能反映参数的概率分布,可靠度分析收敛快,不需要大量的模拟,因此,值得在边坡可靠度分析中推广应用。也将工程上常用的均匀设计和正交设计用于边坡可靠度分析,结果表明,正交设计结果和中心点法比较接近,而均匀设计得到的结果则是不可靠的。展开更多
现有概率最优潮流计算侧重于概率计算方法的设计和改进,难以从本质上提高概率最优潮流的计算效率。为此,以交直流新能源电网为研究对象,考虑风电、光伏发电的不确定性,建立交直流互联新能源电网概率最优潮流模型。首先,提出一种改进凸...现有概率最优潮流计算侧重于概率计算方法的设计和改进,难以从本质上提高概率最优潮流的计算效率。为此,以交直流新能源电网为研究对象,考虑风电、光伏发电的不确定性,建立交直流互联新能源电网概率最优潮流模型。首先,提出一种改进凸松弛技术处理非线性非凸潮流方法,将其转化为凸规划形式下的概率最优潮流模型;其次,利用Nataf变换处理非正态分布随机变量间的相关性,进而采用结合拉丁超立方采样技术的蒙特卡罗模拟法(monte carlo simulation,MCS)进行求解以降低MCS的计算量;最后,通过改进的IEEE 39节点、118节点以及500节点系统验证所提方法的有效性。展开更多
文摘The design of new Satellite Launch Vehicle （SLV） is of interest, especially when a combination of Solid and Liquid Propulsion is included. Proposed is a conceptual design and optimization technique for multistage Low Earth Orbit （LEO） bound SLV comprising of solid and liquid stages with the use of Genetic Algorithm （GA） as global optimizer. Convergence of GA is improved by introducing initial population based on the Design of Experiments （DOE） Technique. Latin Hypercube Sampling （LHS）-DOE is used for its good space filling properties. LHS is a stratified random procedure that provides an efficient way of sampling variables from their multivariate distributions. In SLV design minimum Gross Lift offWeight （GLOW） concept is traditionally being sought. Since the development costs tend to vary as a function of GLOW, this minimum GLOW is considered as a minimum development cost concept. The design approach is meaningful to initial design sizing purpose for its computational efficiency gives a quick insight into the vehicle performance prior to detailed design.
文摘为了改善柴油机燃烧室内燃油喷雾撞壁和混合气形成情况,提出一种直喷式柴油机多点分布式导向台燃烧室。将这种新燃烧室结构参数化,对7个设计变量进行多参数协同优化。以一台230 mm缸径的中速船用柴油机为基础模拟缸内工作过程,采用拉丁超立方取样的方法从设计空间得到600个样本点,根据模拟结果分析各设计参数对发动机性能的影响,根据不同的优化目标得到3种新燃烧室结构。仿真结果表明:在75%负荷工况下与原机ω型燃烧室相比,Ⅰ型燃烧室的指示油耗率(indicated specific fuel consumption,ISFC)降低1.83%,烟粒(soot)排放量降低86.83%;Ⅱ型燃烧室的ISFC降低0.97%,NO_(x)排放量降低7.44%,soot排放量降低68.26%;Ⅲ型燃烧室的INO_(x)和soot排放量分别降低10.52%和58.08%,ISFC基本不变。
文摘现有概率最优潮流计算侧重于概率计算方法的设计和改进,难以从本质上提高概率最优潮流的计算效率。为此,以交直流新能源电网为研究对象,考虑风电、光伏发电的不确定性,建立交直流互联新能源电网概率最优潮流模型。首先,提出一种改进凸松弛技术处理非线性非凸潮流方法,将其转化为凸规划形式下的概率最优潮流模型;其次,利用Nataf变换处理非正态分布随机变量间的相关性,进而采用结合拉丁超立方采样技术的蒙特卡罗模拟法(monte carlo simulation,MCS)进行求解以降低MCS的计算量;最后,通过改进的IEEE 39节点、118节点以及500节点系统验证所提方法的有效性。
