Modularization modeling and simulation of turbine test rig main test system

Comprehensive applications of modularization modeling method have proven its effectiveness and versatility in system simulation field. This paper establishes the modularization numerical model of a turbine test rig main test system by using a finite volume numerical system developed. The simulation study based on an experiment is conducted. The comparison with available experimental data indicates that the general trends of simulation curves are in agreement with test curves and that there is obvious thermal stratification phenomenon at different positions along combustion gas flow direction. Accordingly, it can be concluded that the analysis of experimental data is reasonable and the established numerical system is effective. It is also found that the modeling of valve spool throttling and the modeling of components-wall heat transfer are two key factors of affecting simulation accuracy.     

Variational inequality model for the simulation of gas transmission networks

The steady-state simulation of a gas transmission network involves the solution of a system of nonlinear algebraic equations subject to a set of inequality constraints. The purpose of this paper is to consider how the problem can be cast into a variational inequality framework using the dual extremum principles described by Noble and Sewell in 1972. The reliability of the model is tested on two networks supplied by the British Gas Corporation.     

A procedure to design the mainline system in natural gas networks

With the start up of West–East Natural Gas Transmission Project, the construction of natural gas-pipeline will enter on a new era in China. The development tendency will be towards large-diameter, high-pressure and long-distance for natural gas-pipelines. Correspondingly, the life cycle cost of natural gas-pipeline networks is increasing gradually. The mainline system is a vital part of natural gas network systems. The investment required for the mainline system is enormous, usually accounting for 80% of the total investment for this system. In general, the investment required for a gas-pipeline depends on its operating parameters. Therefore, based on the characteristics of gas networks, optimization for investment becomes indispensable to gas networks design. A comprehensive and optimal mathematic model of a gas networks system is established in this paper which considers all the factors influencing the total investment of a gas networks system (e.g. pipe diameter, thickness, pressure, length, compression ratio, etc). From the standpoint of the characteristics of a model comprising both continuous and discrete variables, a new methodology, rank-optimization, is presented. On the basis of this model, a simple and visual high-pressure networks optimization program has been compiled. Furthermore, the developed optimization program has been applied to a practical project and the effects of operating parameters on the total investment have been analyzed. The simulation model in this paper is shown to be an effective method to solve optimization on mainline system in high-pressure gas networks.     

GasTurbnLab: a multidisciplinary problem solving environment for gas turbine engine design on a network of nonhomogeneous machines

Gas turbine engines are very complex (with 20–40,000 parts) and have extreme operating conditions. The important physical phenomena take place on scales from 10–100 microns to meters. A complete and accurate dynamic simulation of an entire engine is enormously demanding. Designing a complex system, like a gas turbine engine, will require fast, accurate simulations of computational models from multiple engineering disciplines along with sophisticated optimization techniques to help guide the design process. In this paper, we describe the architecture of an agent-based software framework for the simulation of various aspects of a gas turbine engine, utilizing a “network” of collaborating numerical objects through a set of interfaces among the engine parts. Moreover, we present its implementation using the Grasshopper agent middleware and provide simulation results that show the feasibility of the computational paradigm implemented.     

Mathematical modeling of the argon oxygen decarburization converter exhaust gas system at the reduction stage

For metallurgical processes, many problems relate to the combination of very large computing domain, chemical reaction, and radiation, high turbulent and multiphase flow, which causes difficulties in the implementation of mathematical modeling. This paper describes the CFD simulation of the complex turbulent exhaust gas flow in an argon oxygen decarburization (AOD) converter in the metallurgical industry combining with species transfer, combustion, and radiation. Some details are explained in order to obtain a fast and good convergence to solve this sort of high non-linear problem. The influence on the simulation result of selecting different species as the last species in the species transfer model is discussed in this paper. The influence of argon blowing rate from bottom tuyeres on the gas flow pattern in the system is also investigated. Although it is very difficult to fully verify the simulated results in the industry at this moment, some of measured data in the factory agree well with the calculation.     

Simulation and experiment on standoff distance affecting gas flow in laser cutting

A three-dimensional axial symmetrical model of laser cutting is established by adopting N–S equation and RNG k–ε onflow model in the paper, and numerical simulation is put up to analyze the flow field of shield gas in cutting slot. The investigation reveals the law about how standoff distance affects the dynamic characteristic of gas jet in cutting process, and the distribution of pressure and velocity of gas jet with different standoff distances are shown in the study. Two typical subsonic nozzles are designed for the laser cutting experiment. At the end of the paper experimental results are compared with the numerical simulation results.     

Modeling and simulation of a gas distribution pipeline network

This research study focuses on the modeling and simulation of a gas distribution pipeline network with a special emphasis on gas ducts. Gas ducts are the most important components of such kind of systems since they define the major dynamic characteristics. Isothermal, unidirectional flow is usually assumed when modeling the gas flow through a gas duct. This paper presents two simplified models derived from the set of partial differential equations governing the dynamics of the process. These models include the inclination term, neglected in most related papers. Moreover, two numerical schemes are presented for the integration of such models. Also, it is shown how the pressure drop along the pipe has a strong dependency with the inclination term. To solve the system dynamics through the proposed numerical schemes a based MATLAB-Simulink library was built. With this library it is possible to simulate the behavior of a gas distribution network from the individual simulation of each component. Finally, the library is tested through three application examples, and results are compared with the existing ones in the literature.     

A new method of digital simulation for an aircraft gas turbine engine control system

An LD-9 aircraft gas turbine engine with its control system is simulated digitally by a new method, called the ‘method of spare parts’. The computer program of simulation possesses the main capabilities of a real engine altitude test facility and is called a ‘digital engine altitude simulator’. The results of simulation show that the capabilities of this new method are much better than that of the ordinary ‘method of block diagram’. The method can be used for modelling and simulating any type of gas turbine engines or industrial process control systems.     

Numerical simulation study on gas–solid two-phase flow in pre-calciner

A three-dimensional numerical simulation of DD (dual combustion and denitratior process) pre-calciner for cement production was conducted in this paper. In Euler coordinate system, the fluid phase is expressed with RNG k–ε two-equation model and the solid phase is expressed with particle stochastic trajectory model in Lagrange coordinate system. Four mixture fractions are deduced in this article to simulate the gas compositions. The results of numerical simulation predicted the burn-out ratio of coal and the decomposition ratio of limestone particles along with particle trajectories. It also supplied theoretical foundation for industrial analysis of the coupling relation between coal combustion and calcium carbonate decomposition.     

Transient Modeling and Simulation of Gas Pipe Networks with Characteristic Diagram Models for Compressors

One challenge for the simulation and optimization of real gas pipe networks is the treatment of compressors. Their behavior is usually described by characteristic diagrams reflecting the connection of the volumetric flow and the enthalpy change or shaft torque. Such models are commonly used for an optimal control of compressors and compressor stations [4,7] using stationary models for the gas flow through the pipes. For transient simulations of gas networks, simplified compressor models have been studied in [1–3]. Here, we present a transient simulation of gas pipe networks with characteristic diagram models of compressors using a stable network formulation as (partial) differential-algebraic system. (© 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)     

相关光谱式气体检测系统的光学仿真及优化

依据相关光谱式红外气体传感器检测原理,以系统中红外光与气体反应的气室为研究对象,利用光学设计专用软件Tracepro对理想红外朗伯光源在不同反射镜类型下光源的最佳位置进行了仿真分析;通过建立光路传输系统的数学模型,对气室不同结构尺寸下的光功率输出、以及气室内壁反射率对传感系统性能的影响进行了仿真与优化.在理论模型的基础上,根据仿真结果,确定了最佳气室模型的参数组合.实验结果表明,通过对气室中红外光源的位置、反射镜类型、气室长度等部分进行适当的优化修改后,可使探测器接收信号幅度得到明显提高,将有利于后级电路的信号放大、数模转换等处理过程,从而提高气体浓度检测的灵敏度和精度.     

A meta-modeling simulation of structure abandonment timing decisions

An offshore oil and gas structure will be decommissioned and removed from service at the end of its productive life, depending upon operator preferences, legislative requirements, and strategic opportunities. The basic aim of decommissioning is to render all wells permanently safe and remove most, if not all, surface/seabed signs of production activity. The purpose of this paper is to characterize the timing decisions associated with abandoning offshore oil and gas structures. Three models are developed, ranging from a production-based forecast to a risked, net present value approach. Functions that describe how the age of the structure upon abandonment is related to system parameters is constructed using a meta-modeling simulation and illustrated on a generic field development scenario.     

Linking Discrete-Event Simulation Models with Expert Systems

This paper describes experiments designed to test the feasibility of linking discrete-event simulation models with expert systems. Two microcomputer systems are used: one contains the simulation model, while the other contains the expert system. The paper shows that by linking a simulation model with an expert system, it is possible to use the combination for simulation parameter learning, expert system development and expert system control of a simulation model.     

Space-time discontinuous Galerkin method for the solution of fluid-structure interaction

The paper is concerned with the application of the space-time discontinuous Galerkin method (STDGM) to the numerical solution of the interaction of a compressible flow and an elastic structure. The flow is described by the system of compressible Navier-Stokes equations written in the conservative form. They are coupled with the dynamic elasticity system of equations describing the deformation of the elastic body, induced by the aerodynamical force on the interface between the gas and the elastic structure. The domain occupied by the fluid depends on time. It is taken into account in the Navier-Stokes equations rewritten with the aid of the arbitrary Lagrangian-Eulerian (ALE) method. The resulting coupled system is discretized by the STDGM using piecewise polynomial approximations of the sought solution both in space and time. The developed method can be applied to the solution of the compressible flow for a wide range of Mach numbers and Reynolds numbers. For the simulation of elastic deformations two models are used: the linear elasticity model and the nonlinear neo-Hookean model. The main goal is to show the robustness and applicability of the method to the simulation of the air flow in a simplified model of human vocal tract and the flow induced vocal folds vibrations. It will also be shown that in this case the linear elasticity model is not adequate and it is necessary to apply the nonlinear model.     

噪声实验室供气系统的可靠性分析

文章研究了噪声实验室供气系统的可靠性问题,根据供气系统的工程设计框图绘制了可靠性框图．进而得到了供气系统的可靠性表达式．根据可靠性的评估方法,结合模拟试验的数据得到了供气系统可靠性评估的定量结果．通过时评估结果的分析,给出了改进噪声实验室供气系统的工程设计从而提高其可靠性的方法．     

The modeling and numerical simulation of gas flow networks

Summary. A network formulation is introduced for the modeling and numerical simulation of complex gas transmission systems like a multi-cylinder internal combustion engine. Several simulation levels are discussed which result in different network representations of a specific system. Basic elements of a network are chambers of finite volume, straight pipes and connections like valves or nozzles. The pipe flow is modeled by the unsteady, one-dimensional Euler equations of gas dynamics. Semi-empirical approaches for the chambers and the connections yield differential-algebraic equations (DAEs) in time. The numerical solution is based on a TVD scheme for the pipe equations and a predictor-corrector method for the DAE-system. Simulation results for an internal combustion engine demonstrate the practical interest of the new approach. Received May 12, 1994 / Revised version received August 26, 1994     

充气薄膜球囊测压法的数学方程

把流动坐标原点设在球囊中心,探讨了用充气薄膜球囊测量流体压力的数学方程,提出了应优选圆球囊测压,并分析了测压误差及误差处理方法,绘出了仿真曲线与实验曲线,通过实验验证了仿真的正确性.     

How to Inflate in the Right Places-An Analysis of Design Characteristics to Cope with Variations in Gas Transmission Networks

This paper considers how much margin to allow when designing a large pipe network based on predictions of future gas supply and demand. Thus it deals with forecasting from the engineering aspect of how to cope with variations from the predicted pattern of events.The subject of the paper is the British Gas National Transmission System. The detail of the paper concerns some of the margins used to design the system, in particular their purpose, size and application.The methods used to analyse the margins are: simulation, regression, distribution fitting, convolution and risk analysis.The conclusion of the work is that different parts of the network require different sizes of margin to retain the same level of security, since the impact of localized forecasting errors and predicted plant failures varies significantly across the grid.     

Consistent Forecasting of Severe Winter Gas Demand

British Gas plans to be able to meet the demand for gas which might occur in a very cold winter such as might occur with a frequency of once in fifty years. Every year the twelve Regions of British Gas renew their forecasts of the 1 in 50 demand for the following five winters. The problem addressed by the paper has two aspects; first, how do we decide what constitutes 1 in 50 winter conditions?, and second, what will be the demand for gas in such conditions? The paper describes how the problem has evolved over the years, and the approach taken by a new Steering Group over the period January 1979-July 1980. This has included the development of a Monte-Carlo simulation model to generate daily gas demands through a winter period over a wide range of conditions. The result has been a new set of guidelines enabling a higher quality and consistency of the Industry's forecasts.     

Modelling of high-pressure gas transmission lines

Gas flow in a transmission line is described by a set of three coupled partial differential equations (PDE) expressing conservation of mass, momentum and energy; the gas properties are described by a non-ideal equation of state. A technique is introduced which reduces the energy equation into a single parameter in the mass equation without the assumption of isothermal or isentropic flow.The remaining set of PDEs is solved by two different techniques. An accurate but time-consuming technique consists of applying the method of characteristics, for which an improved representation of the friction term is presented. The second way consists of a finite-difference implementation with a second-order truncation error on an analogue computer. Both the physical assumptions and the numerical approximations are checked against data obtained from experiments in the main transport system of Gasunie.Guidelines on the analogue modelling of pipeline systems and the interpretation of simulation results conclude the paper.