燃油烟管蒸汽锅炉热力设计优化数学模型的研究

为了优化燃油烟管锅炉热力设计,根据热力设备优化理论。分析确定了优化的独立变量和相关变量,以及目标函数。结合热力设计过程。对目标函数的中间变量进行了求解,并确定了优化的约束条件,建立了完整的优化数学模型。此外,编制了计算机求解程序,并对一个典型燃油烟管锅炉进行了优化,优化结果表明,该优化模型和求解程序是有效和实用的。     

Theoretical analysis of the dynamic interactions of vapor compression heat pumps

A detailed mathematical model of vapor compression heat pumps is described. Model derivations of the various heat pump components are given. The component models include the condenser, evaporator, accumulator, expansion device, and compressor. Details of the modeling techniques are presented, as is the solution methodology. Preliminary simulation results are also illustrated. The model developed predicts the spatial values of temperature and enthalpy as functions of time for the two heat exchangers. The temperatures and enthalpies in the accumulator, compressor and expansion device are modeled in lumped-parameter fashion. Pressure responses are determined by using continuity satisfying models for both the condenser and evaporator. The discussion of the solution methodology describes the combined implicit/explicit integration formulation that is used to solve the governing equations. The summary provides a list of future work anticipated in the area of dynamic heat pump modeling.     

水库群余留统计迭代法数学模型的建立

本文给出了余留统计造代算法(RBSI)数学模型的层次结构、目标、约束条件以及关联模型的详细推导过程,从而建立了RBSI算法完整的数学模型体系,为在计算机上用软件实现这种算法奠定了基础。     

直喷式柴油机喷雾碰壁燃烧过程的计算机模拟

本文以实验和计算机模拟的结果为基础,略去壁面区域复杂的传热、传质及蒸发等物理过程,在汽态喷雾的假设下,建立了以模拟直喷式柴油机喷雾碰壁燃烧过程的燃烧率、NO形成过程为目的数学模型.通过计算结果与实验的比较证明,在汽态假设下,合适的构造子模型可以对该燃烧过程做出模拟.     

Development,theoretical analysis and performance evaluation of shelf type solar driers

A brief summary of solar driers is given. A simple shelf type drier is described and test results are outlined.The mathematical model of the multi-shelf type drier is developed and its solution using a digital computer is compared with test results to verify the mathematical formulation. Theoretical values of temperatures and drying rates are presented. Extension of the analysis for the refinement of the shelf type driers is discussed.     

A MULTILEVEL BOUNDARY-ELEMENT METHOD FOR TWO-DIMENSIONAL STEADY HEAT DIFFUSION

A fast, accurate, and efficient multilevel boundary-element method (MLBEM) is developed to solve general boundary-value problems arising in computational mechanics. Here we concentrate on problems of two-dimensional steady potential flow and present a fast, direct boundary-element formulation. This novel method extends the pioneering work of Brandt and Lubrecht on multilevel multi-integration (MLMI) in several important ways to address problems with mixed boundary conditions. We utilize bi-conjugate gradient methods (BCGMs) and implement the MLMI approach for fast matrix and matrix transpose multiplication for every iteration loop. After introducing a C-cycle multigrid algorithm, we find that the number of iterations for the bi-conjugate gradient methods is independent of the boundary-element mesh discretization for a broad range of steady-state heat diffusion problems. Here, for a model problem in an L-shaped domain, we demonstrate that the computational complexity of the proposed method approaches the desired goal of N ln N, where N is the number of degrees of freedom. For this problem, we show that the MLBEM algorithm reduces computer run times by a factor of 6,295, whereas the memory requirements are reduced 432 times compared to conventional boundary-element methods, while preserving the accuracy of the numerical solution. Furthermore, the method can be extended in a straightforward manner to the solution of many problems in science and engineering that result in very large sets of matrix equations when the associated integral equations are discretized.     

Analysis of a current-regulated brushless DC drive

Current-regulated brushless DC machines are used in a wide variety of applications including robotics, actuators, electric vehicles, and ship propulsion systems. When conducting system analysis of this or any other type of drive, average-value reduced-order models are invaluable since they provide a means of rapidly predicting the electromechanical dynamics and are readily linearized for control system synthesis. In this paper, a highly accurate average-value reduced-order model of a hysteresis current-regulated brushless DC drive is set forth. In so doing it is demonstrated that the drive exhibits five distinct operating modes. The physical cause of each of these modes is explained and a mathematical model for each mode is set forth. The mathematical models are verified both experimentally and through the use of computer simulation. It has been found that the model set fourth herein is on the order of 300 times faster than a detailed computer simulation in calculating electromechanical transients     

ANALYSIS OF CONJUGATE HEAT TRANSFER IN MICROCHANNEL HEAT SINKS

Thermal radiation, although considered an important mode of heat transfer in high temperature conditions, often is neglected in fire modeling, mainly because of the complex physics involved. This study provides modelers with guidance on the engineering treatment of radiation transfer. Two widely used radiation models, the discrete transfer and the six-flux models, are reviewed and their performance is assessed in a benchmark fire case. The models are compared in terms of computational efficiency, ease of application, and predictive accuracy, and their range of validity is delineated, for single compartment fire cases. The results demonstrate that the simple six-flux model suffices for small compartment fires, up to 100 kW. For higher heat release rates, where the six-flux model breaks down, the discrete transfer provides sufficient accuracy, under certain conditions.     

Mathematical modeling and simulation for external electrothermal characteristics of an alkaline water electrolyzer

The water electrolyzer is a key device in the direct energy interaction between the hydrogen production system and the fluctuation power supply. Therefore, to understand its external electrothermal characteristics and modeling, an efficient simulation method is not only theoretically significant but also of great value in engineering applications for the key techniques, such as the study of control strategy and optimum configuration of renewable energy generation. Currently, research studies on the electrothermal characteristics of the alkaline water electrolyzer (AWE) are focused mainly on the microcosmic mechanism, without sufficient emphasis on the modeling and simulation technique of the external macroscopic electrothermal characteristics. Based on relevant theories in electrochemistry and test results of the electrothermal characteristics, this paper establishes a mathematical model of the equivalent impedance characteristics, electrothermal characteristics, and power regulation characteristics of AWE. Then, a simulation model of the external electrothermal characteristics is built with Matlab/Simulink. Finally, the accuracy of the established mathematical model and the functionality of the simulation model are verified. The research can provide some reference for the modeling and simulation of the electrical characteristics of AWE.     

Parametric sensitivity analysis of PEM fuel cell electrochemical Model

In order to obtain an adequate PEM Fuel Cell model, it is necessary to define the values for a specific group of modeling parameters. The disagreements between the experimental and simulation results arise because of uncertainties stemming not only from the experimental measurements, but also from the modeling parameters used in the theoretical calculations. The modeling parameters were analyzed using Multi-Parametric Sensitivity Analysis (MPSA). This paper presents a sensitivity investigation of PEMFC electrochemical models and aims to determine the relative importance of each parameter on the modeling results. A computer program is written in Dev-cpp environment to calculate the sensitivity index for each parameter. As a result, the parameters were classified according to their influence in the modeling results as: insensitive, sensitive and highly sensitive. Thus it is possible to evaluate the relative importance of each parameter to the simulation accuracy. The present work benefits to understand the most effecting parameters, thus it helps the manufacturer to be more cautious in defining the exact value for them.     

发动机冷却系统陈述式动态模型

鉴于发动机冷却系统传统过程式模型在模块化、重用性、参数化等方面的不足,在详细分析发动机冷却系统部件数学模型的基础上,采用面向对象的陈述式建模方式在多领域仿真平台MWorks上建立了易于管理、修改、重用和扩充的发动机冷却系统陈述式动态模型库,模型库各重要部件均采用动态表征。为更精确地计算散热器动态性能,提出了二维离散方法构建散热器模型。通过试验数据验证了散热器模型,散热器出口冷却液温度和空气温度的稳态仿真值与试验值误差分别为4.20%和4.75%。通过调用模型库中的部件模型构建了结构典型的发动机冷却系统,并对仿真结果进行了理论对比分析。     

Intelligent computing for the dynamics of fluidic system of electrically conducting Ag/Cu nanoparticles with mixed convection for hydrogen possessions

The present study aims to provide an innovative stochastic numerical solver's application by the use of neural networks with Levenberg-Marquardt backpropagation to examine the dynamics of hydrogen possessions and variable viscosity in the fluidic system of electrically conducting copper and silver nanoparticles with mixed convection. The system of PDEs obtained by mathematical modeling of the physical phenomena are reduced into non-linear ODEs by utilizing suitable transformations. The ODEs dataset is constructed through Adams numerical solver and target parameters for input and output parameter of neural networks. The testing, validation and training processes are exploited in neural network models with learning based on backpropagation of LM method to calculate the solution for different scenarios created on variation of physical parameters of the proposed flow of Reynolds and Vogel models. Validation and verification of neural network model to find the solution of fluid flow problem is endorsed on the assessment of achieved accuracy through mean squared error, error histograms and regression studies.     

Analytical Model of a Combined Adsorption Cooling and Mechanical Vapor Compression Refrigeration System

ABSTRACT

A combined adsorption and mechanical vapor compression system is a reasonable option to reduce the consumption of fossil fuels for air conditioning by utilizing waste heat. Performance predictions of combined adsorption and mechanical vapor compression systems require detailed dynamic modeling because the transitional characteristics explain the nature of the adsorption system. It is, however, desirable to simplify the model for practical use at engineering stages. Since the mechanical vapor compression system is based on the steady-state thermodynamic cycle, a semi-steady-state modeling of adsorption cycles would be functional for analysis of combined systems. In our study, the analytical solution of transient simulation for adsorption cycles was combined with a steady-state mathematical model of the mechanical vapor compression system. The performance of the combined system was analyzed based on the model developed, taking into account the cycle time of the adsorption cycle. The results show the performance characteristics as well as the energy-saving potential of the combined system.     

Inductive modeling of lithium-ion cells

Sandia National Laboratories has conducted a sequence of studies on the performance of lithium ion and other types of electrochemical cells using inductive models. The objectives of some of these investigations are: (1) to develop procedures to rapidly determine performance degradation rates while these cells undergo life tests; (2) to model cell voltage and capacity in order to simulate cell output under variable load and temperature conditions; (3) to model rechargeable battery degradation under conditions of cyclic charge/discharge, and many others. Among the uses for the models are: (1) to enable efficient predictions of battery life; (2) to characterize system behavior.

Inductive models seek to characterize system behavior using experimentally or analytically obtained data in an efficient and robust framework that does not require phenomenological development. There are certain advantages to this. Among these advantages is the ability to avoid making measurements of hard to determine physical parameters or having to understand cell processes sufficiently to write mathematical functions describing their behavior. We have used artificial neural networks (ANNs) for inductive modeling, along with ancillary mathematical tools to improve their accuracy.

This paper summarizes efforts to use inductive tools for cell and battery modeling. Examples of numerical results are presented.     

基于伪随机信号的链条锅炉动态特性辨识

有效的控制策略是提高工业锅炉运行经济性的重要保证,但是,控制系统的设计和优化升级都需要有合适的数学模型作为指导,对基于伪随机信号(PRBS)的工业锅炉动态特性辨识建模进行了比较深入的研究.着重讨论了PRBS信号参数的确定、数据的预处理,基于最小二乘的建模方法及模型的验证;以此为基础,还用MATLAB高级语言编写和开发了相应的辨识程序.结合某20 t/h链条工业锅炉的现场试验数据,利用该方法及其对应的程序对锅炉动态特性进行了建模,经验证,该辨识模型具有较高的可信度,可为锅炉控制系统设计和优化升级提供相应的理论基础和科学依据.     

An Exact-Steady-state Adaptive Chemistry method for combustion simulations: Combining the efficiency of reduced models and the accuracy of the full model

Many reduced-model methods have been developed to alleviate the computational expense of simulating chemically reacting flows with detailed kinetics. However, it is still impossible to determine exactly the loss in accuracy relative to the full model when reduced kinetic models are used for predicting quantities of interest (typically state variables). Ideally, one wishes to obtain the predictions of the full chemistry model at the fast speed of the simplified model(s). This paper describes a technique for achieving this goal for steady-state simulations. The new method, called Exact-Steady-state Adaptive Chemistry (ESAC), performs multiple fast reduced-model simulations of the steady-state problem, each time refining the accuracy of the solution by using increasingly accurate reduced models. Smaller (less accurate, but faster) reduced models are used when the simulation is far from (the full-model) steady-state; and more accurate (larger, slower) models are used as the simulation approaches the final steady-state solution. The simulation is completed by applying the trusted full kinetic model, guaranteeing the accuracy of the steady-state solution obtained using ESAC. We have developed a basic algorithm that applies this method and we present results from 2-D CFD simulations of steady-state methane and ethylene flames. ESAC simulations yielded the full-model solution (as guaranteed by the method) and were generally a factor of 3–4 times faster than the equivalent standard full-model-everywhere simulations. Future refinement of the basic implementations described here can further increase the speedup obtained when using ESAC. In applications where computational time rather than computer memory availability is the limiting factor, this technique enables efficient computation of the steady-state predicted by the full, detailed chemical kinetics model.     

不完全微分PID控制自动调速系统仿真

自动调速系统是应用较为广泛的电力拖动自控系统,根据其物理系统建立数学模型,利用科学与工程计算工具ＭＡＴＬＡＢ所提供的ＳＩＭＵＬＩＮＫ进行动态建模,在计算机上进行仿真实验,对于设计、调试各种新型调速系统具有开放性强、结构易修改、重复利用率高等优点。     

Nonlinear analysis of dual-phase lag bio-heat model in living tissues induced by laser irradiation

Abstract

This paper provides a method for determining a numerical solution of the thermal damage of living tissues using a nonlinear dual phase lag model. Due to the nonlinearity of the basic equations, the finite element approach is adopted to solve such problems. The numerical outcomes obtained by the finite element technique are also compared with the existing experimental study to verify the accuracy of the numerical calculations. Based on the formulation of Arrhenius, the thermal damages to the tissues are estimated by the denatured protein range. Numerical results for temperatures are presented graphically. Also, the comparisons between the numerical outcomes and the existing experimental data show that the present mathematical models are effective tools to evaluate the bioheat transfer in a spherical living tissue.     

汽轮机叶片的建模及插补算法研究

为提高汽轮机的工作效率,汽轮机叶片的表面通常是设计成扭曲的变截面曲面,叶片形状十分复杂,因此,汽轮机叶片的精确几何造型对保证叶片加工质量十分重要。进行汽轮机叶片数学建模和数控插补算法研究,根据图纸数据对汽轮机叶片进行基于NURBS曲线和曲面的反求计算,建立了汽轮机叶片的精确数学模型。针对叶片高速高精度数控加工的要求,以叶片数学模型为基础,建立叶片截面的NURBS曲线组,利用MATLAB编程仿真,验证了采用不同插补算法进行叶片数控加工的适应性。     

恒装置角模式井眼轨迹控制计算方法研究

在滑动钻进过程中,井眼轨迹具有井眼曲率和装置角基本保持不变的特征,但是使用空间圆弧模型计算出的装置角是逐渐变化的。为了解决这个理论与实际相矛盾的问题,提出了使用恒装置角曲线模型进行井眼轨迹控制方案设计的数学模型,并对求解方法进行了初步研究。建立了扭方位模型、点靶模式、线靶模式等三种实际问题中经常使用的轨迹控制方式的优化目标函数,使用序贯数论网格优化算法(SNTO)对一些算例进行了实际计算。结果表明,所建立的数学模型具有可行性,能够设计出合理的井眼轨迹控制方案,并且能够使用计算机软件编程来实现。本文的研究是初步的由于优化目标函数具有"狭长峡谷"特征,对数值优化算法的求解效率要求很高,这个问题需要进一步的深入研究。