Academic literature on the topic 'Transient differential characteristics'

Research on the wide-band modelling method of the grounding grid and the analysis of the electromagnetic transients on the grounding grid has significant practical meaning on the engineering problems, e.g. overvoltage protection, insulation coordination and electromagnetic interference and the increasing levels of capacity in the power and communication systems. This paper presents strategies which establish the equivalent circuit for computing the transient performance of grounding grid base on fractional order differential theory, which takes into account the fractional frequency characteristics of soil permittivity. In order to validate the presented method, an example is considered and the transient responses are compared with the results obtained by the method of moments.

Based on the theory of hydraulic transients and the method of characteristics (MOC), a mathematic model of the differential surge tank with pressure-reduction orifices (PROs) and overflow weirs for transient calculation is proposed. The numerical model of hydraulic transients is established using the data of a practical hydropower station; and the probable transients are simulated. The results show that successive load rejection is critical for calculating the maximum pressure in spiral case and the maximum rotating speed of runner when the bifurcated pipe is converging under the surge tank in a diversion-type hydropower station; the pressure difference between two sides of breast wall is large during transient conditions, and it would be more serious when simultaneous load rejections happen after load acceptance; the reasonable arrangement of PROs on breast wall can effectively decrease the pressure difference.

In this paper, based on the choice of voltage level 500kV for large transformer differential protection of maloperation accident actually as an example, discusses how to improve the reliability and the transformer differential protection with the relationship between pressure test. Analysis found that in order to avoid the excitation transient exciting current transformer differential protection sparked the misoperation, on-site technical personnel in the differential protection setting calculation process, make use of data in conformity with the relevant parameters, rules and standards, familiar with differential protection, also need to understand the characteristics of transformer excitation transient exciting current high-voltage tests, the influence of characteristic more should fully exert the modern PC wave record device, instrument function can improve the actual effect of transformer differential protection. This factory for transformer differential protection for setting, protection greatly improves the reliability. This experience is worth popularizing.

This paper presents a non-linear math model on ship power station and numerical simulation, aiming at describing dynamic characteristic of electric propulsion ship shipboard power system precisely. Non-linear differential algebraic equations are given by differential equation modeling theory, concerning with diesel engine speed characteristics, electromagnetic and electrical transient characteristics (Φd, Φq, Ed", Eq", E'q, ω, δ as status variables) of synchronous generator and voltage characteristics of excitation system. Then the non-linear equations are solved by implicit trapezoidal integration method, finally dynamic curves of status variables such as voltage, speed of rotor, three phase current of stator and so on are drawn based on simulation program written by C#.NET. Simulation results demonstrate that the non-linear math model proposed by this paper is reasonable, and the results are theory foundation of transient stability on ship integrated power system for further research.

On the basis of explaining the basis theory on transient electromagnetic sounding, wavelet theory and imaging principle of differential conductivity for transient electromagnetic sounding data, this thesis proposes rapid imaging technology of electromagnetic sounding based on wavelet analysis, describes the characteristics of noises under wavelet decomposition, and employs wavelet packet analysis to eliminate noise of signals, at last, introduces wavelet analysis into transient electromagnetic sounding on the platform of MATLAB wavelet function toolbox and deals with differential conductivity imaging processing steps of transient electromagnetic sounding.

When expressed in the form of characteristic differential equations, the laws governing propagation of linear one-dimensional waves through heterogeneous media show that the only properties of significance are the sound speed c and the acoustic impedance ρc, either of which may vary spatially. The former occurs in the differential equations governing the (curved) characteristics, while the latter appears in the differential equations governing the evolution of particle velocity and stress along the characteristics. The present study employs an inherently stable finite difference representation of the characteristic equations, in which the spatial grid is obtained by evaluating the intersections in space-time of constant time lines with comparable increments of the characteristic variables. The numerical procedure is used to follow the propagation of a single-lobe sine pulse in cases where only ρ or c fluctuates spatially about a mean value while the other property is constant, and compares those results to the case were both material properties vary. Nonconstancy of c is shown to cause temporal shifts in waveforms, while spatial variation of ρc causes attenuation and distortion of the waveform.

Very few stochastic systems are known to have closed-form transient solutions. In this article we consider an immigration birth and death population process with total catastrophes and study its transient as well as equilibrium behavior. We obtain closed-form solutions for the equilibrium distribution as well as the closed-form transient probability distribution at any time t ≥ 0. Our approach involves solving ordinary and partial differential equations, and the method of characteristics is used in solving partial differential equations.

Congenital contractures are a heterogeneous group of various diseases with different etiology and pathogenesis. The article describes a family case of hereditary sensory-motor polyneuropathy caused by a mutation with 943GA (p Arg315Trp) in the TRPV4 gene (transient receptor potential vanilloid cation channel 4, NM_021625. 4). The article presents the clinical and neurological characteristics of the patient, the results of genetic and neurophysiological examination of the patient and his parents, differential diagnosis of this disease. Congenital contractures are a heterogeneous group of various diseases with different etiology and pathogenesis. The article describes a family case of hereditary sensory-motor polyneuropathy caused by a mutation with 943GA (p Arg315Trp) in the TRPV4 gene (transient receptor potential vanilloid cation channel 4, NM_021625. 4). The article presents the clinical and neurological characteristics of the patient, the results of genetic and neurophysiological examination of the patient and his parents, differential diagnosis of this disease. Congenital contractures are a heterogeneous group of various diseases with different etiology and pathogenesis. The article describes a family case of hereditary sensory-motor polyneuropathy caused by a mutation with 943GA (p Arg315Trp) in the TRPV4 gene (transient receptor potential vanilloid cation channel 4, NM_021625. 4). The article presents the clinical and neurological characteristics of the patient, the results of genetic and neurophysiological examination of the patient and his parents, differential diagnosis of this disease. Congenital contractures are a heterogeneous group of various diseases with different etiology and pathogenesis. The article describes a family case of hereditary sensory-motor polyneuropathy caused by a mutation with 943GA (p Arg315Trp) in the TRPV4 gene (transient receptor potential vanilloid cation channel 4, NM_021625. 4). The article presents the clinical and neurological characteristics of the patient, the results of genetic and neurophysiological examination of the patient and his parents, differential diagnosis of this disease. Congenital contractures are a heterogeneous group of various diseases with different etiology and pathogenesis. The article describes a family case of hereditary sensory-motor polyneuropathy caused by a mutation with 943GA (p Arg315Trp) in the TRPV4 gene (transient receptor potential vanilloid cation channel 4, NM_021625. 4). The article presents the clinical and neurological characteristics of the patient, the results of genetic and neurophysiological examination of the patient and his parents, differential diagnosis of this disease. Congenital contractures are a heterogeneous group of various diseases with different etiology and pathogenesis. The article describes a family case of hereditary sensory-motor polyneuropathy caused by a mutation with 943GA (p Arg315Trp) in the TRPV4 gene (transient receptor potential vanilloid cation channel 4, NM_021625. 4). The article presents the clinical and neurological characteristics of the patient, the results of genetic and neurophysiological examination of the patient and his parents, differential diagnosis of this disease. Congenital contractures are a heterogeneous group of various diseases with different etiology and pathogenesis. The article describes a family case of hereditary sensory-motor polyneuropathy caused by a mutation with 943GA (p Arg315Trp) in the TRPV4 gene (transient receptor potential vanilloid cation channel 4, NM_021625. 4). The article presents the clinical and neurological characteristics of the patient, the results of genetic and neurophysiological examination of the patient and his parents, differential diagnosis of this disease. Congenital contractures are a heterogeneous group of various diseases with different etiology and pathogenesis. The article describes a family case of hereditary sensory-motor polyneuropathy caused by a mutation with 943GA (p Arg315Trp) in the TRPV4 gene (transient receptor potential vanilloid cation channel 4, NM_021625. 4). The article presents the clinical and neurological characteristics of the patient, the results of genetic and neurophysiological examination of the patient and his parents, differential diagnosis of this disease. Congenital contractures are a heterogeneous group of various diseases with different etiology and pathogenesis. The article describes a family case of hereditary sensory-motor polyneuropathy caused by a mutation with 943GA (p Arg315Trp) in the TRPV4 gene (transient receptor potential vanilloid cation channel 4, NM_021625. 4). The article presents the clinical and neurological characteristics of the patient, the results of genetic and neurophysiological examination of the patient and his parents, differential diagnosis of this disease. Congenital contractures are a heterogeneous group of various diseases with different etiology and pathogenesis. The article describes a family case of hereditary sensory-motor polyneuropathy caused by a mutation with 943GA (p Arg315Trp) in the TRPV4 gene (transient receptor potential vanilloid cation channel 4, NM_021625. 4). The article presents the clinical and neurological characteristics of the patient, the results of genetic and neurophysiological examination of the patient and his parents, differential diagnosis of this disease. Congenital contractures are a heterogeneous group of various diseases with different etiology and pathogenesis. The article describes a family case of hereditary sensory-motor polyneuropathy caused by a mutation with 943GA (p Arg315Trp) in the TRPV4 gene (transient receptor potential vanilloid cation channel 4, NM_021625. 4). The article presents the clinical and neurological characteristics of the patient, the results of genetic and neurophysiological examination of the patient and his parents, differential diagnosis of this disease. Congenital contractures are a heterogeneous group of various diseases with different etiology and pathogenesis. The article describes a family case of hereditary sensory-motor polyneuropathy caused by a mutation with 943GA (p Arg315Trp) in the TRPV4 gene (transient receptor potential vanilloid cation channel 4, NM_021625. 4). The article presents the clinical and neurological characteristics of the patient, the results of genetic and neurophysiological examination of the patient and his parents, differential diagnosis of this disease. Congenital contractures are a heterogeneous group of various diseases with different etiology and pathogenesis. The article describes a family case of hereditary sensory-motor polyneuropathy caused by a mutation with 943GA (p Arg315Trp) in the TRPV4 gene (transient receptor potential vanilloid cation channel 4, NM_021625. 4). The article presents the clinical and neurological characteristics of the patient, the results of genetic and neurophysiological examination of the patient and his parents, differential diagnosis of this disease. Congenital contractures are a heterogeneous group of various diseases with different etiology and pathogenesis. The article describes a family case of hereditary sensory-motor polyneuropathy caused by a mutation with 943GA (p Arg315Trp) in the TRPV4 gene (transient receptor potential vanilloid cation channel 4, NM_021625. 4). The article presents the clinical and neurological characteristics of the patient, the results of genetic and neurophysiological examination of the patient and his parents, differential diagnosis of this disease. Congenital contractures are a heterogeneous group of various diseases with different etiology and pathogenesis. The article describes a family case of hereditary sensory-motor polyneuropathy caused by a mutation with 943GA (p Arg315Trp) in the TRPV4 gene (transient receptor potential vanilloid cation channel 4, NM_021625. 4). The article presents the clinical and neurological characteristics of the patient, the results of genetic and neurophysiological examination of the patient and his parents, differential diagnosis of this disease. Congenital contractures are a heterogeneous group of various diseases with different etiology and pathogenesis. The article describes a family case of hereditary sensory-motor polyneuropathy caused by a mutation with 943GA (p Arg315Trp) in the TRPV4 gene (transient receptor potential vanilloid cation channel 4, NM_021625. 4). The article presents the clinical and neurological characteristics of the patient, the results of genetic and neurophysiological examination of the patient and his parents, differential diagnosis of this disease. Congenital contractures are a heterogeneous group of various diseases with different etiology and pathogenesis. The article describes a family case of hereditary sensory-motor polyneuropathy caused by a mutation with 943GA (p Arg315Trp) in the TRPV4 gene (transient receptor potential vanilloid cation channel 4, NM_021625. 4). The article presents the clinical and neurological characteristics of the patient, the results of genetic and neurophysiological examination of the patient and his parents, differential diagnosis of this disease. Congenital contractures are a heterogeneous group of various diseases with different etiology and pathogenesis. The article describes a family case of hereditary sensory-motor polyneuropathy caused by a mutation with 943GA (p Arg315Trp) in the TRPV4 gene (transient receptor potential vanilloid cation channel 4, NM_021625. 4). The article presents the clinical and neurological characteristics of the patient, the results of genetic and neurophysiological examination of the patient and his parents, differential diagnosis of this disease. Congenital contractures are a heterogeneous group of various diseases with different etiology and pathogenesis. The article describes a family case of hereditary sensory-motor polyneuropathy caused by a mutation with 943GA (p Arg315Trp) in the TRPV4 gene (transient receptor potential vanilloid cation channel 4, NM_021625. 4). The article presents the clinical and neurological characteristics of the patient, the results of genetic and neurophysiological examination of the patient and his parents, differential diagnosis of this disease. Congenital contractures are a heterogeneous group of various diseases with different etiology and pathogenesis. The article describes a family case of hereditary sensory-motor polyneuropathy caused by a mutation with 943GA (p Arg315Trp) in the TRPV4 gene (transient receptor potential vanilloid cation channel 4, NM_021625. 4). The article presents the clinical and neurological characteristics of the patient, the results of genetic and neurophysiological examination of the patient and his parents, differential diagnosis of this disease. Congenital contractures are a heterogeneous group of various diseases with different etiology and pathogenesis. The article describes a family case of hereditary sensory-motor polyneuropathy caused by a mutation with 943GA (p Arg315Trp) in the TRPV4 gene (transient receptor potential vanilloid cation channel 4, NM_021625. 4). The article presents the clinical and neurological characteristics of the patient, the results of genetic and neurophysiological examination of the patient and his parents, differential diagnosis of this disease. Congenital contractures are a heterogeneous group of various diseases with different etiology and pathogenesis. The article describes a family case of hereditary sensory-motor polyneuropathy caused by a mutation with 943GA (p Arg315Trp) in the TRPV4 gene (transient receptor potential vanilloid cation channel 4, NM_021625. 4). The article presents the clinical and neurological characteristics of the patient, the results of genetic and neurophysiological examination of the patient and his parents, differential diagnosis of this disease. Congenital contractures are a heterogeneous group of various diseases with different etiology and pathogenesis. The article describes a family case of hereditary sensory-motor polyneuropathy caused by a mutation with 943GA (p Arg315Trp) in the TRPV4 gene (transient receptor potential vanilloid cation channel 4, NM_021625. 4). The article presents the clinical and neurological characteristics of the patient, the results of genetic and neurophysiological examination of the patient and his parents, differential diagnosis of this disease. Congenital contractures are a heterogeneous group of various diseases with different etiology and pathogenesis. The article describes a family case of hereditary sensory-motor polyneuropathy caused by a mutation with 943GA (p Arg315Trp) in the TRPV4 gene (transient receptor potential vanilloid cation channel 4, NM_021625. 4). The article presents the clinical and neurological characteristics of the patient, the results of genetic and neurophysiological examination of the patient and his parents, differential diagnosis of this disease. Congenital contractures are a heterogeneous group of various diseases with different etiology and pathogenesis. The article describes a family case of hereditary sensory-motor polyneuropathy caused by a mutation with 943GA (p Arg315Trp) in the TRPV4 gene (transient receptor potential vanilloid cation channel 4, NM_021625. 4). The article presents the clinical and neurological characteristics of the patient, the results of genetic and neurophysiological examination of the patient and his parents, differential diagnosis of this disease. Congenital contractures are a heterogeneous group of various diseases with different etiology and pathogenesis. The article describes a family case of hereditary sensory-motor polyneuropathy caused by a mutation with 943GA (p Arg315Trp) in the TRPV4 gene (transient receptor potential vanilloid cation channel 4, NM_021625. 4). The article presents the clinical and neurological characteristics of the patient, the results of genetic and neurophysiological examination of the patient and his parents, differential diagnosis of this disease. Congenital contractures are a heterogeneous group of various diseases with different etiology and pathogenesis. The article describes a family case of hereditary sensory-motor polyneuropathy caused by a mutation with 943GA (p Arg315Trp) in the TRPV4 gene (transient receptor potential vanilloid cation channel 4, NM_021625. 4). The article presents the clinical and neurological characteristics of the patient, the results of genetic and neurophysiological examination of the patient and his parents, differential diagnosis of this disease.

Transient saturation characteristics of TPY-type current transformer have great impact on the right action of line differential protection. This paper proposes an analytical method of line differential protection under current transformer saturation by utilizing current transformer model and test methods. The true current value of primary side can be obtained by our proposed method and therefore it yields correct assessment of line operating status. This method has high reliability applying to practical engineering examples of differential protection.

This master’s thesis deals with the design of equipment for testing differentials. The aim of the thesis is therefore the design of a special device that will be able to measure the steady and transient characteristics of differentials. Master’s thesis is divided into four chapters. The first chapter points out the disadvantages of fully open and closed differentials, the second deals with a basic overview of the structures and design of self-locking differentials. The third chapter deals with research of existing devices that test and measure the characteristics of differentials. The fourth chapter then discusses the possible drives of the tested unit. The fifth chapter focuses on the actual construction design of the test equipment. The subsequent sixth chapter then solves the strength calculations of the chosen structural elements of this device.

The effectiveness of an optimization algorithm can be reduced to its ability to navigate an objective function’s topology. Hybrid optimization algorithms combine various optimization algorithms using a single meta-heuristic so that the hybrid algorithm is more robust, computationally efficient, and/or accurate than the individual algorithms it is made of. This thesis proposes a novel meta-heuristic that uses search vectors to select the constituent algorithm that is appropriate for a given objective function. The hybrid is shown to perform competitively against several existing hybrid and non-hybrid optimization algorithms over a set of three hundred test cases. This thesis also proposes a general framework for evaluating the effectiveness of hybrid optimization algorithms. Finally, this thesis presents an improved Method of Characteristics Code with novel boundary conditions, which better characterizes pipelines than previous codes. This code is coupled with the hybrid optimization algorithm in order to optimize the operation of real-world piston pumps.

The MSc Thesis deals with real-time modelling, especially with the control circuits, where we focus on the regulation circuit with auxiliary model of the regulated system. The introduction contains the Theory of Controls and regulation. The work is divided into two basic parts. The first part deals with the problems from the theoretical point of view. The theoretical part is concerned with the general systems. Various definitions of systems, their partition and mathematical methods for their description are mentioned after introducing. A description the regulation circuits, their partition, structures and types follows. There are shown the particular regulators and different types of regulated systems in details. Mathematical methods applied to solve the differential equations that describe the models of the systems are summarized in the second part of the work. The end of this chapter is concerned with the TKSL system. In the practical part I have produced Microsoft Power Point program which summarizes the results of experiments, made in the TKSL and TKSL/C system. The output of simulation was transformed into the graphs in the format of Microsoft Excel. The last part deals with suggestion and implementation simulators of control circuits.

The neurology chapter examines mild, transient, and more serious, underlying neurological conditions that present in the newborn period. Abnormalities of tone, activity, alertness, and movements (i.e., seizures) can occur in many neonatal conditions, some of which require immediate intervention. Assessments include testing infant tone and reflexes, the Encephalopathy Assessment Table, distinguishing jitteriness from seizure activity, and identifying seizure characteristics. Early identification of infants with hypoxic ischemic encephalopathy—a primary cause of neonatal encephalopathy—is essential and should prompt either thermoregulatory management (strict normothermia) or therapeutic hypothermia, providing specific criteria are met. Symptomatic hypoglycemia can have long-term neurodevelopmental consequences and must be treated emergently with intravenous dextrose solution. Anticonvulsant therapy should be initiated for seizures, even when the underlying cause is not yet determined. Diagnostic testing and differential diagnoses, such as neonatal abstinence syndrome or neonatal opiate withdrawal are considered. Three case scenarios follow care pathways for two unwell infants.

Migraine and epilepsy are both characterized by transient attacks of altered brain function with a clinical, pathophysiological, and therapeutic overlap. Furthermore, epilepsy and migraine may mimic each other. In particular, occipital lobe seizures may be easily misinterpreted as migraine with visual aura, although there seems to be several clinical characteristics that can differentiate between visual auras of epileptic and migrainous origin

The symptomatic repertoire of cardiac disease is relatively narrow and most conditions will present with one or more of chest pain, dyspnoea, palpitation, syncope, or presyncope. On the other hand, the differential diagnosis of each of these symptoms is broad and includes both cardiac and non-cardiac disorders. Certain features of acute chest pain alter the likelihood of acute coronary syndrome but, in isolation, the history is usually insufficient to rule in or rule out the diagnosis. Intermittent chest pain can be categorized as typical angina, atypical angina, or non-anginal based on three symptom characteristics; this classification has substantial diagnostic value and helps to determine the need for and the most appropriate mode of further investigation. Orthopnoea and paroxysmal nocturnal dyspnoea are more specific for heart failure than other forms of dyspnoea. However, it is not possible to diagnose either acute or chronic heart failure by the history alone. For both angina and chronic heart failure, the European Society of Cardiology recommends objective assessment of symptom severity using the Canadian Cardiovascular Society and New York Heart Association classifications respectively. Definitive diagnosis of palpitation usually requires documentation of the cardiac rhythm during symptoms but a clear description of the symptom may suggest the likely diagnosis and guide the optimal approach to rhythm monitoring. The history is invaluable in differentiating syncope and presyncope from other causes of transient loss of consciousness and dizziness. Beyond this, clinical features such as prodromal symptoms or precipitation of episodes by exposure to pain can help to distinguish cardiac from reflex syncope.

Phospholipids, which provide valuable model systems for lipid membranes, display a variety of polymorphic phases, depending on their molecular structure and on environmental conditions. High hydrostatic pressure has been used as a physical parameter to study the thermodynamic properties and phase behavior of these systems. High pressure is also a characteristic feature of certain natural membrane environments. In the first part of this article, we review our recent work on the temperature- and pressure-dependent phase behavior of phospholipid systems differing in lipid conformation and headgroup structure. In the second part, we report on the determination of the (T, x, p) phase diagrams of binary phospholipid mixtures. An additional section deals with effects of incorporating ions, small amphiphilic molecules, and steroids into the bilayer on the experimental temperature- and pressure-dependent phase behavior of lipid systems. Finally, we discuss lamellar to nonlamellar thermotropic and barotropic phase transformations, which occur for a number of lipids, such as phosphatidylethanolamines, monoacylglycerides, and lipid mixtures. It has been suggested that nonlamellar lipid structures might play an important role as transient and local intermediates in a number of biochemical processes. High-pressure smallangle x-ray (SAXS) and neutron (SANS) scattering, differential scanning calorimetry (DSC), high-pressure differential thermal analysis (DTA), and p, V, T measurements have been used as experimental methods for the investigation of these systems. Lipid bilayer dispersions, in particular the phosphatidylcholines and phosphatidylethanolamines, are the workhorses for the investigation of biophysical properties of membrane lipids because they constitute the basic structural component of biological membranes. They exhibit a rich lyotropic and thermotropic phase behavior (Cevc & Marsh, 1987; Marsh, 1991; Yeagle, 1992). Most fully hydrated saturated phospholipid bilayers exhibit two principal thermotropic lamellar phase transitions, corresponding to a gel to gel (Lβ′–Pβ′) transition and a gel to liquid-crystalline (Pβ′–Lα) main transition at a temperature Tm. In the fluid-like La phase, the hydrocarbon chains of the lipid bilayers are conformationally disordered, whereas in the gel phases the hydrocarbon chains are more extended and relatively ordered.

Our objective in this paper is to introduce the detailed implementation and performance of a new method so called Incremental Differential Quadrature Method (IDQM) for modeling transient flow in pipelines. The basics of IDQM, its structure, and the formulation of the method for numerical simulation of transient flow in pipelines are discussed. The results obtained from this numerical exercise are compared with the method of characteristics and experimental data. The test case studies show that the best structure for IDQM solution is cosine grid distribution. In terms of viscous damping, the inclusion of unsteady friction term in the governing equations can improve the results significantly. This study demonstrates that IDQM can be regarded as a new alternative for numerical solution of transient flow such as water hammer in pipelines. IDQM is highly implicit in nature which makes the method unconditionally stable. It gives accurate results using few grid points.

Nowadays, anticipating and controlling transient response is a critical design activity for ensuring both safety and integrity of the operational subsea system. Predicting transient effect, commonly known as surge pressure, is of high importance for offshore industry. In order to determine the installation of protection equipments to avoid surge pressure effects, the operational teams have raised concerns, whether the system is adequately designed to protect the subsea system against possible surge pressures during the event of sudden closure of a valve. Researches, referred to transient effects, explain that is necessary to evaluate the system performance under current and desired operating conditions. The main goal of this paper is to predict the surge pressure during unforeseen closure valves at Refrigerated LPG and Gasoline (C5+) pipeline systems. In these systems the valves are located downstream the flowlines. Detailed computer modeling attempts to simulate the complex interactions between flowline and fluid, aiming at providing efficient flowline system integrity. These models are based on Transient Methodology which is defined for a set of nonlinear partial differential equations that relate fundamental variables with pressure head and flow velocity. The solution of differential equations has been carried out by Finite Difference Method that transforms these equations into characteristic equations. These can be accurately solved through high-speed digital computers. Flowmaster, Chicago, USA, was the software used to develop the analysis models. The software offers an advanced graphical interface to build networks and resultant graphics. The results from Flowmaster have been validated through a defined methodology that applies the Characteristics Method based on Wylie and Streeter assumptions. Simulations considering the fluid as gasoline have shown a sudden damping of pressure wave when the valve closure time was 10 seconds, leading to the restoration of the initial flow conditions. The analysis using the Method of Characteristics, however, does not exhibit this sudden damping, although a gradually reduction of fluctuations around the initial pressure are observed. The transient analysis through Flowmaster for Refrigerated LPG leads to a pressure envelope that shows a change of the flow direction triggering a cyclical process until the restoration of the initial operational conditions.

Transient response of gas turbine engines depends on several parameters including engine type, components’ characteristics, and operational condition. This paper briefly describes the general methodology and approach for transient sensitivity analysis of various gas turbine engines, and the results of a computer program for analysis of the transient behavior of a single spool turbojet. Based on the method of intercomponent volumes, the general methodology applicable to transient analysis of any gas turbine based system has been developed. The method results in a set of stiff, time dependent non-linear ordinary differential equations (ODE) which can be solved by an appropriate ODE solver. The coefficients of the differential equations depend on the design and operational condition of the components represented by the component maps. The initial conditions of the ODE can be any steady state operating point of the engine. A steady state engine model provides these initial conditions. The program has the capability to match the components, and obtain a steady state operating point for the engine, accept a fuel protocol and predict the transient behavior of the engine. The program has produced satisfactory results for step, ramp and sinusoidal fuel inputs, as well as ramp variation in nozzle exit area.

The finite difference technique of vibroacoustical pipeline characteristics are developed. The technique allows calculations vibroacoustical characteristics of pipe with the axial line lying in one plane under force excitation by oscillating fluid flow. The technique is based on the solving differential equation system of interaction between solid and oscillating fluid in the pipeline. Solution was done for transient non-stationary nonlinear differential equation system. The boundary conditions for fluid is a parameter combination of complex pressure oscillation amplitude of pipeline inlet section, complex pressure oscillation amplitude of pipeline outlet section, complex velocity oscillation amplitude of pipeline inlet section, complex velocity oscillation amplitude of pipeline outlet section, load impedance, input impedance. The boundary conditions for solid is bonding of the pipeline. Time response of the pipeline vibration are resulted of these techniques. The mathematical technique computational coast is 3 orders less than Ansys technique. The method is developed for pipeline diameter much smaller than acoustic wavelength in a fluid. It is actual for aircraft pipelines, pipes of power plants, mobile machines and pipes of stationary processing machines.

This study examines the transient behavior of a seal injection system, for four boiler circulating water pumps, in an effort to optimize seal flush rates under startup conditions. During startup, seal injection supply water experiences a large increase in pressure, going from 1.8–26.2 MPa. This large increase in supply pressure presents a challenge in maintaining the desired differential pressure across the seals, and hence the optimum seal flush rate. Overshoot of the control valve position can result in starving the seals of seal water. Delayed responses expose the seals to excessively large differential pressures. The seal injection system was modeled using PIPENET™ Vision. The model consists of a detailed replica of the seal injection system pipe network. Initial and boundary conditions were obtained from plant DCS data and pump OEM specifications. A baseline model was developed and validated using actual system response data. Extended models considered two types of control systems, manual and differential pressure-control; as well as, control valves with various flow characteristics: linear and equal percentage. Additionally, a diffuser breakdown assembly and startup control valve were also introduced as control components into the model. Results show that the implantation of a diffuser breakdown assembly in series with the primary control valve (modified linear), in conjunction with automated controls produced a differential pressure of 436 kPa which was within the OEM specified range of differential pressures (345–690 kPa). A startup control valve used in series with the primary control valve also produced acceptable results (388 kPa). The proper design and operation of seal injection systems is vital to extending time between overhauls, thereby reducing maintenance costs. The use of the aforementioned control components in series with control valves is common for boiler feedwater regulation systems during startup; however, this is the first application known to the authors for pump seal injection systems in fossil plants. The results of the hydraulic simulation outlined in this study show this application is viable.

Abstract As a consequence of the increasing share of renewable energy sources in present-day electrical grid systems, time variations of the power demand for fossil fuel plants can become more sudden. Therefore, an ability to respond to sudden load changes becomes an important issue for power generation gas turbines. This paper describes a real-time model for predicting the transient performance of gas turbines. The method includes basic transient phenomena, such as volume packing and the heat transfer between the working fluid and the structural elements. The dynamics of components are quantified by solving ordinary differential equations with appropriate initial and boundary conditions. Compressor and turbine operating points are determined from corresponding performance maps previously calculated using sophisticated aerodynamic, through-flow codes. This includes a sufficient number of such characteristics to account for the variations in speed and machine geometry. The developed dynamic model was verified by comparison of simulation results with experimentally recorded operating parameters for a real engine. This includes the start-up sequence and the change of load. Additional simulation covers the system response to a step increase in fuel flow. The simulation is carried out faster than the real process.

Abstract Numerical simulation of flow, combustion phenomena and pollutants emission characteristics have been obtained on an internal combustion engine having conventional flat piston and advanced piston geometries. The code employed the time marching procedure that solves the governing partial differential equations of multi-component chemically reactive fluid flow by finite difference method. The transient solution is marched out in a sequence of time steps. The results show that both the piston geometry and inlet flow conditions affects the local flame properties which subsequently alters the pollutants emission levels. The numerical results provide a cost effective means of developing advanced internal combustion engine chamber geometry design that provides high efficiency and low pollution levels. It is expected that increased computational tools will be used in the future for enhancing our understanding of the detailed combustion process in internal combustion engines and all other energy conversion systems. Such detailed information is critical for energy conservation and environmental pollution control.

Abstract An on-board rotor-bearing system operating at high speed is inevitably subjected to additional inertial forces and parametric excitations caused by aircraft maneuvering flights. The differential equations of motion for a squeeze film damped rotor system moving with the aircraft during maneuvering flight are derived based on Lagrange’s principle. Transient characteristics of the rotor system considering instantaneous static eccentricity of journal in turning maneuver are calculated by Newmark-HHT integration method. The effects of forward speed, radius of curvature, and elastic support stiffness on transient responses are discussed subsequently. The results indicate that when the aircraft conducts a maneuvering flight, the whirl orbit of journal deviates from the center of the damper, and the deviation direction is determined by the centrifugal acceleration of aircraft and the additional gyroscopic moment. The journal performs a nonsynchronous whirl around the instantaneous static eccentricity. Its magnitude is related to the additional maneuvering loads and the stiffness of elastic support. Increasing forward speed or decreasing maneuvering radius, the rotor vibration will enter earlier into or withdraw later from the relatively large eccentric condition. The stiffness of elastic support has a great impact on transient characteristics of rotor-bearing system during maneuvering flight. Overall, using finite element modeling combined with mechanism analysis, a flexible and efficient approach is proposed to predict transient responses of engine rotor systems during aircraft maneuvering flights.

In the present study, the flow characteristics of a top discharge blow tank at high pressure were investigated. Experiments on discharge properties of pulverized coal in dense-phase pneumatic conveying system with a high pressure blow tank were carried out. The influences of fluidizing velocity, pressurizing velocity, transporting differential pressure, sending pressure in the blow tank and pulverized coal diameter on the solid mass flow rate were studied. The experimental results indicated that the ratio of fluidizing velocity to pressurizing velocity was of great importance on the solid mass flow rate and there existed an optimum range. The solid mass flow rate increased as the transporting differential pressure and sending pressure increased. The increase of particle diameter led to the decrease of the solid mass flow rate. A model for determining the solid mass flow rate has been formulated using dimensional analysis. It was found that the calculation results were in good agreement with the experimental data. Finally, a kinetic–frictional model, which treated the kinetic and frictional stresses in an additive manner, was incorporated into the two fluid model based on the kinetic theory of granular flow to simulate the transient behaviors of the high pressure blow tank.