基于合作博弈的电力市场模式下售电商购电策略模型

伴随电力改革的进一步深化,售电侧市场得以逐渐放开,售电商的出现打破了原有输配售一体化的经营模式,售电商作为主要经济主体将在售电侧市场展开竞争。对电力交易差价合约进行了解释,根据差价合约理论对电力市场模式下发电商的发电价格和生产行为进行了分析;对差价合约下的售电商购电策略进行了探讨,采用情景分析法对售电商之间存在的联盟与非联盟2种情景进行了模拟分析,探讨了售电商合作情景形成联盟时,各售电商的利益变动情况;利用夏普利值法构建了售电商联盟合作利益均衡模型,对联盟内各售电商利益分配情况进行了分析。     

低含气率气液两相流涡街特性研究

气液两相涡街现象广泛存在于生产实际中,由于相间作用,研究变得较为复杂。通过数值模拟和实流试验,对水平管低含气率情况下气相对两相涡街的影响进行研究。建立三维计算流体力学（Computational fluid dynamics, CFD）仿真模型,采用VOF多相流模型和RNG k-e 湍流模型,模拟气液两相钝体绕流。仿真与试验结果在定量频率上具有良好的一致性。结合仿真与试验结果,从近尾迹流场与涡拓扑、斯特劳哈尔数两方面,对不同含气率两相涡街特性进行对比研究。结果表明,在稳定涡街范围内,随着气相含率增大,对涡街起重要作用的滞止区长度增大,导致斯特劳哈尔数线性减小;同时,涡街周期性和信号质量变差,涡街能量降低,这是由于涡中心吸入密度小、速度大的气泡,造成涡的旋转能量降低,进而影响涡街的稳定性。     

伯努利效应引起滑阀阀芯径向力的研究

运用CFD软件Fluent对液压滑阀内部流场进行可视化分析,详细研究了阀芯受径向压力分布情况和影响因素。计算发现,径向压力分布与阀口开度、入口流量、环割槽深径比、进出口油道的轴交角都有密切的关系。阀口开度越大,径向压力波动越小;入口流量越大,环割槽深径比越小,径向压力波动越大;与进出口轴交角为0°和90°相比,进出口轴交角为180°时x=0截面的径向压力分布更平稳。同时,通过伯努利效应对入口中心截面处阀芯周向压力分布及阀芯轴向分段建立压力方程,通过理论分析验证了仿真模型和结果的可靠性。最后分析了径向力不平衡产生的卡紧力及径向稳态液动力的分布及其影响因素。     

Large-scale fire suppression modeling of corrugated cardboard boxes on wood pallets in rack-storage configurations

In this study, the fire growth and suppression models in FireFOAM were validated for rack-storage commodities consisting of two solid fuels, namely corrugated cardboard boxes and hardwood pallets, which are referred to as Class 2 commodity. Validation experiments included two fire-growth and two fire-suppression configurations with different rack-storage array heights (3 and 5 tiers). In the suppression study, standard-response upright ceiling sprinklers (K-factor of 160 lpm/bar^1/2) were used. The time-resolved chemical heat release rates obtained from the experiments were used to validate the fire growth model. The observed sprinkler activations and fire-spread patterns were used to validate the suppression model. This study identified that lateral flame spread is primarily enabled by flames impinging on the commodity's bottom surfaces. This study also showed that obstructions, such as wood pallets, can significantly impede convective and radiative heat transfer to the underside of the commodity, reducing the lateral flame spread rate. Fire-suppression modeling revealed that both surface water transport and lateral flame spread rates are important when predicting fire-suppression behavior. Therefore, as the rack-storage array height increases, so does the water transport time, which results in the fire becoming more difficult to control. Likewise, as the lateral spread rate increases, e.g., as occurs in the absence of wood pallets, fire-suppression also becomes more difficult.     

基于CFD的车辆进气系统流场仿真与分析

针对传统发动机辅助系统中进气系统的设计多采用经验公式,结果不够准确这一问题,提出了基于计算流体动力学(computational fluid dynamics,CFD)的设计方法.通过建立进气系统的三维模型并进行网格划分,选择RNG(renormalization-group)湍流模型建立气相的数学模型,定义适当的边界条件,利用Fluent软件对进气系统气相流动规律进行数值模拟.在充分考虑空气滤清器滤网的影响,将滤网结构设为多孔介质区域的基础上,对比分析3种设计方案内部流场的速度矢量分布和压力分布,以进气阻力为评判准则,确定进气阻力最小的方案2为最佳设计方案.这种方法对进气系统的设计提供了实用的参考.     

径向动压气体轴承承载能力的CFD分析

为改进计算精度和提高计算效率,采用CFD软件Fluent对径向动压气体轴承承载能力进行分析.使用软件Solidworks建立径向动压气体轴承三维物理建模;从可压缩流体润滑方程及连续性方程出发,得到等温条件下动压润滑雷诺方程的基本形式,运用有限差分法计算径向动压轴承的压力分布及承载力等特性;采用Fluent进行有限元仿真...     

Investigating the effect of crevice flow on internal combustion engines using a new simple crevice model implemented in a CFD code

A theoretical investigation is conducted to examine the way the crevice regions affect the mean cylinder pressure, the in-cylinder temperature, and the velocity field of internal combustion engines running at motoring conditions. For the calculation of the wall heat flux, a wall heat transfer formulation developed by the authors is used, while for the simulation of the crevices and the blow-by a newly developed simplified simulation model is presented herein. These sub-models are incorporated into an in-house Computational Fluid Dynamics (CFD) code. The main advantage of the new crevice model is that it can be applied in cases where no detailed information of the ring-pack configuration is available, which is important as this information is rarely known or may have been altered during the engine’s life. Thus, an adequate estimation of the blow-by effect on the cylinder pressure can be drawn. To validate the new model, the measured in-cylinder pressure traces of a diesel engine, located at the authors’ laboratory, running under motoring conditions at four engine speeds were used as reference, together with measured velocity profiles and turbulence data of a motored spark-ignition engine. Comparing the predicted and measured cylinder pressure traces of the diesel engine for all cases examined, it is observed that by incorporating the new crevice sub-model into the in-house CFD code, significant improvements on the predictive accuracy of the model is obtained. The calculated cylinder pressure traces almost coincide with the measured ones, thus avoiding the use of any calibration constants as would have been the case with the crevice effect omitted. Concerning the radial and swirl velocity profiles and the turbulent kinetic energy measured in the spark-ignition engine, the validation process revealed that the developed crevice model has a minor influence on the aforementioned parameters. The theoretical study has been extended by investigating in the same spark-ignition engine, during the induction and compression strokes, the way crevice flow affects the thermodynamic properties of the air trapped in the cylinder.     

Optimization design of slotted fin by numerical simulation coupled with genetic algorithm

Using a novel method that couples genetic algorithm (GA) with numerical simulation, the geometric configuration for a two-dimensional slotted fin has been optimized in this paper. The objective of optimization is to maximize the heat transfer capacity of slotted fin, and minimize the pressure drop penalty of fluid flow through the fin. The key of this method is the fitness function of GA, which were (j/j₀)/(f/f₀) and j/j₀. In this complex multiparameter problem, the numerical simulation is a crucial step to calculate the Colburn factor j and friction factor f. The results showed that for two-dimensional slotted fin considered, the j factor is increased by 229.22%, the f factor is increased by 196.30%, and the j/f ratio was increased by 11.11% at Re = 500 based on optimal integrated performance (j/j₀)/(f/f₀); the j factor is increased by 479.08% at Re = 500 based on optimal heat exchange capacity j/j₀. The feasibility of optimal designs was verified by the field synergy principle.     

基于CFD流场模拟的反应釜结构设计

反应釜是制药化工产品生产的主要设备之一,常以搅拌的形式出现。本文研究了搅拌器相关设计参数对反应釜内流场的影响,并以此为依据改进反应釜结构。首先通过工程设计方法得到小型制药搅拌釜的初始设计方案,利用CFD技术对搅拌釜内的流场进行数值模拟研究,所得结果与文献中的结果基本一致。然后调整反应釜搅拌器的安装高度与搅拌转速等设计参数,与初始设计方案进行模拟结果对比分析,根据混合效果与驱动输入功率等设计要求,修改设计参数得到更优的设计方案。     

陶瓷干法造粒过程温度场对造粒效果的研究

针对陶瓷干法造粒机造粒过程温度场对造粒效果的影响,结合实验与数值模拟对比分析造粒过程温度场对造粒效果的影响.基于CFD方法建立模拟造粒过程温度场的数学模型,模拟造粒过程中温度场随时间变化情况,并实验测得造粒室温度值、造粒成品率随时间变化情况.仿真结果与实验数据对比表明:当造粒时间为7 min时,仿真结果显示造粒室内的温度值都低于80℃,实验测得颗粒成品率占整体颗粒质量的56％;当造粒时间为9 min时,仿真结果显示造粒室内温度值高于80 ℃的区域占造粒体积3％,实验测得颗粒成品率占整体颗粒质量的72％;当造粒时间为11 min时,仿真结果显示造粒室内温度值高于80℃的区域占造粒体积21％,实验测得颗粒成品率占整体颗粒质量的61％.仿真结果与实验数据对比分析说明:当造粒室内温度值高于80℃时,将在一定程度上降低造粒的成品率.