Lumped Parameter Approach Research Articles

Modelling the heat dynamics of a residential building unit: Application to Norwegian buildings

The paper refers to the development of a continuous time mathematical heating model for a building unit based on the rst principles. The model is described in terms of the state space variables, and a lumped parameter approach is used to represent the room air temperature and air density using mass and energy balances. The one-dimensional heat equation in cartesian coordinates and spherical coordinates is discretized in order to describe the thermic characteristics of the layers of the building framework and furniture respectively. The developed model is implemented in a MATLAB environment, and mainly a theoretical approach is used to validate it for a residential building unit. Model is also validated using experimental data for a limited period. Short term simulations are used to test the energy eciency of the building unit with regard to factors such as the operation of heat sources, ventilation, occupancy patterns of people, weather conditions, features of the building structure and heat recovery. The results are consistent and are obtained considerably fast, implying that the model can be used further in modelling the heating dynamics of complex architectural designs and in control applications.

Energy Savings in the Hydraulic Circuit of Agricultural Tractors

Increasing interest in reducing pollutant emissions and fuel consumption of off-road vehicles has led to research into alternative systems that aim to reduce the power dissipation of the hydraulic circuits equipping such vehicles. This work proposes alternative hydraulic architectures for agricultural tractors in comparison with traditional systems. The alternative circuit architecture uses independent metering valves and electronically controlled variable pump and involves different control strategies. The analysis is performed with reference to the hydraulic circuit and operating conditions of the remote utilities of a medium-sized tractor. A duty cycle for remote utilities is used for the analysis, obtained from experimental measurements on a tractor equipped with a front loader. Traditional and alternative architectures are modelled using a lumped parameter approach. In this way it is demonstrated that considerable energy savings can be achieved using the alternative architectures.

Thermodynamic Analysis of ORC for Energy Production from Geothermal Resources

This study concerns a thermodynamic analysis of Organic Rankine Cycles for energy conversion from geothermal resources. A numerical flow-chart tool based on a lumped parameters approach is adopted to compute values of thermodynamic variables during each transformation composing the cycle. The equation of state is expressed by the Peng-Robinson formulation. The different plant components are outlined by single blocks, linked each other by connections through balance equations. Analyses are carried-out considering two working fluids (isopentane and isobutane). Results are obtained for several sets of operating parameters, such as the evaporation and condensation pressure for the working fluid, the mass flow rate of the geothermal fluid and the cooling water temperature. From results, thermodynamic cycles are built-up in the T-s plan, allowing to quantify effectiveness and energy benefit related to the investigated functional scenarios.

Stability analyses for the European LFR demonstrator

The development of next-generation Lead-cooled Fast Reactors (LFRs) up to industrial deployment requires the realization of a demonstration plant intended to prove the viability of technology as well as the overall system behavior. The conceptual design of a low-cost scaled-down LFR named ALFRED (Advanced Lead Fast Reactor European Demonstrator) has been undertaken within the European Commission's 7th Framework Programme's LEADER (Lead-cooled European Advanced Demonstration Reactor) project. A simulation tool has been developed in MATLAB® based on a lumped-parameter approach, aimed at investigating the reactor stability and identifying potential regions of instability through relatively straightforward analyses. As a major outcome, ALFRED has turned out to be inherently stable on the entire power range independently of both the fuel burn-up and the value of the coolant density coefficient, which should reach unrealistic high values (nearly 6pcmK−1) to make the reactor unstable. The results of this study have provided the reactor designers with important feedbacks leading to the finalization of the primary system configuration.

Nonlinear Dynamic Analysis of Multi-component Mooring Lines Incorporating Line-seabed Interaction

In this study, a deterministic approach for the dynamic analysis of a multi-component mooring line was formulated. The floater motion responses were considered as the mooring line upper boundary conditions while the anchored point was considered as pinned. Lumped parameter approach was adopted for the mooring line modelling. The forces considered were the submerged weights of mooring/attachment, physical/added inertia, line tension, fluid/line relative drag forces and line/seabed reactive forces. The latter interactions were modelled assuming that the mooring line rested on an elastic dissipative foundation. An iterative procedure for the dynamic analysis was developed and results for various mooring lines partially lying on different soils were obtained and validated by conducting a comparative study against published results. Good agreement between numerical and published experimental results was achieved. The contribution of the soil characteristics of the seabed to the dynamic behaviour of mooring line was investigated for different types of soil and reported.

Acoustic metamaterials with circular sector cavities and programmable densities

Considerable interest has been devoted to the development of various classes of acoustic metamaterials that can control the propagation of acoustical wave energy throughout fluid domains. However, all the currently exerted efforts are focused on studying passive metamaterials with fixed material properties. In this paper, the emphasis is placed on the development of a class of composite one-dimensional acoustic metamaterials with effective densities that are programmed to adapt to any prescribed pattern along the metamaterial. The proposed acoustic metamaterial is composed of a periodic arrangement of cell structures, in which each cell consists of a circular sector cavity bounded by actively controlled flexible panels to provide the capability for manipulating the overall effective dynamic density. The theoretical analysis of this class of multilayered composite active acoustic metamaterials (CAAMM) is presented and the theoretical predictions are determined for a cascading array of fluid cavities coupled to flexible piezoelectric active boundaries forming the metamaterial domain with programmable dynamic density. The stiffness of the piezoelectric boundaries is electrically manipulated to control the overall density of the individual cells utilizing the strong coupling with the fluid domain and using direct acoustic pressure feedback. The interaction between the neighboring cells of the composite metamaterial is modeled using a lumped-parameter approach. Numerical examples are presented to demonstrate the performance characteristics of the proposed CAAMM and its potential for generating prescribed spatial and spectral patterns of density variation.

Retort process modelling for Indian traditional foods.

Indian traditional staple and snack food is typically a heterogeneous recipe that incorporates varieties of vegetables, lentils and other ingredients. Modelling the retorting process of multilayer pouch packed Indian food was achieved using lumped-parameter approach. A unified model is proposed to estimate cold point temperature. Initial process conditions, retort temperature and % solid content were the significantly affecting independent variables. A model was developed using combination of vegetable solids and water, which was then validated using four traditional Indian vegetarian products: Pulav (steamed rice with vegetables), Sambar (south Indian style curry containing mixed vegetables and lentils), Gajar Halawa (carrot based sweet product) and Upama (wheat based snack product). The predicted and experimental values of temperature profile matched with ±10% error which is a good match considering the food was a multi component system. Thus the model will be useful as a tool to reduce number of trials required to optimize retorting of various Indian traditional vegetarian foods.

Multicell Active Acoustic Metamaterial With Programmable Effective Densities

Considerable interest has been devoted to the development of various classes of acoustic metamaterials. Acoustic metamaterials are those structurally engineered materials that are composed of periodic cells designed in such a fashion to yield specific material properties (density and bulk modulus) that would affect the wave propagation pattern within in a specific way. All the currently exerted efforts are focused on studying passive metamaterials with fixed material properties. In this paper, the emphasis is placed on the development of a new class of composite one-dimensional acoustic metamaterials with effective densities that are programmed to vary according to any prescribed patterns along the volume of the metamaterial. The theoretical analysis of this class of multilayered composite active acoustic metamaterials (CAAMM) is presented and the theoretical predictions are determined for an array of fluid cavities separated by piezoelectric boundaries. These smart self-sensing and actuating boundaries are used to modulate the overall stiffness of the metamaterial periodic cell and in turn its dynamic density through direct acoustic pressure feedback. The interaction between the neighboring layers of the composite metamaterial is modeled using a lumped-parameter approach. One-dimensional wave propagation as well as long wavelength assumptions are adapted in the current analysis. Numerical examples are presented to demonstrate the performance characteristics of the proposed CAAMM and its potential for generating prescribed spatial and spectral patterns of density variation. The CAAMM presents a viable approach to the development of effective acoustic cloaks that can be used for treating critical objects in order to render them acoustically invisible.

ANN based Sensor Faults Detection, Isolation, and Reading Estimates – SFDIRE: Applied in a nuclear process

In this paper a new method is developed based on the capabilities of the Artificial Neural Networks (ANNs) to detect, isolate, and output an estimated reading of faulty sensor/s reading/s that serves in monitoring a complex process. For a number of measured signals working to monitor a process, we allow training of an equal number of ANN’s to those signals. Each ANN has an output signal equal to one corresponding measured signal and the set of inputs is the rest of other measured signals and other networks output signals using two-hidden layer feedforward network with different number of neurons for each. After the measuring the error between the real signal and the ANN output, the faulty sensor can be detected. The reading of this faulty sensor could be isolated and an estimated reading is sent to the monitoring system. This method could be applied for any difficult to model process to increase its availability and in the same time maintaining safety. In this paper, the application considered is the thermal–hydraulics process of Egyptian Training and Research Reactor-2 (ETRR-2) core cooling system. Data from the reactor are used to train the networks using backpropagation algorithm, An approximated model based on the lumped parameters approach for the thermal–hydraulics of the reactor core is built to compare results against ANN based system. The proposed system deals with 6 signals. From comparison, very good results are achieved when testing the design.

Effect of flexible pin on the dynamic behaviors of wind turbine planetary gear drives

Flexible pins eliminate the need for straddle mounting, and therefore enable the maximum possible number of planets to be used for any particular epicyclic ratio of power transmission systems. Having more planet gears will significantly increase the input torque density. In this type of design, the pin stiffness and position tolerances are important parameters as they affect the dynamic performances significantly. The present study addresses this issue by modeling, the design of double cantilevered flexible pin, and analyzing the contributions of pin stiffness and misalignment applying the lumped parameter approach. The proposed model formulates the coupled lateral-torsional dynamic response of a planetary spur gear, including the effects of mesh stiffness and phasing as a function of pin error. The resultant equations of motion are applied to examine the effects of pin stiffness and position errors on the natural modes and structural dynamic response. The effects of pin stiffness on deviation of the tooth contact forces of the sun-planet and ring-planet gear pairs are analyzed to understand the relationship between mesh characteristic and input speed variations. The calculated supporting forces of the planet gear are examined to understand the load sharing characteristic due to pin errors, pin stiffness and input load of the power transmission system.

Time-optimal control of the race car: influence of a thermodynamic tyre model

The robustness of an existing numerical method for the time-optimal control of the race car is demonstrated through its application to a model of a Formula 1 car equipped with a simplified thermodynamic tyre model. The tyre model includes a temperature- and frequency-dependent model of road/tyre friction. A lumped parameter approach is used to model the thermodynamics of the various parts of the tyre such as the tread, carcass and inflation gas. The influence of tyre, track surface and ambient temperatures on time-optimal manoeuvring is presented.

Warship propulsion system control

The modelling of a dual gas turbine, single-shaft transmission drive, for a naval propulsion system, is considered. Owing to the spatial dispersion of the arrangement, a distributed–lumped parameter approach to the dynamic analysis problem is necessary. This enables the relatively concentrated assemblies to be included as lumped, pointwise representations and the propulsion shaft to be incorporated as a dispersed inertia and stiffness element. A multivariable, least effort controller design strategy is employed to achieve the regulation required. The performance of the closed-loop system following reference input and load disturbances is evaluated and the drive shaft speed and twist angle response transients are computed.

Onset of Self-Excited Oscillations of Traveling Wave Thermo-Acoustic-Piezoelectric Energy Harvester Using Root-Locus Analysis

The onset of self-excited oscillations is developed theoretically for a traveling wave thermo-acoustic-piezoelectric (TAP) energy harvester. The harvester is intended for converting thermal energy, such as solar or waste heat energy, directly into electrical energy without the need for any moving components. The thermal energy is utilized to generate a steep temperature gradient along a porous regenerator. At a specific threshold of the temperature gradient, self-sustained acoustic waves are generated inside an acoustic resonator. The resulting pressure fluctuations excite a piezoelectric diaphragm, placed at the end of the resonator, which converts the acoustic energy directly into electrical energy. The pressure pulsations are amplified by using an acoustic feedback loop which introduces appropriate phasing that make the pulsations take the form of traveling waves. Such traveling waves render the engine to be inherently reversible and thus highly efficient. The behavior of this class of harvesters is modeled using the lumped-parameter approach. The developed model is a multifield model which combines the descriptions of the acoustic resonator, feedback loop, and the regenerator with the characteristics of the piezoelectric diaphragm. A new method is proposed here to analyze the onset of self-sustained oscillations of the traveling wave engine using the classical control theory. The predictions of the developed models are validated against published results. Such models present invaluable tools for the design of efficient TAP energy harvesters and engines.

Valuing Ecosystem Services with Fishery Rents: A Lumped-Parameter Approach to Hypoxia in the Neuse River Estuary

Valuing ecosystem services with microeconomic underpinnings presents challenges because these services typically constitute nonmarket values and contribute to human welfare indirectly through a series of ecological pathways that are dynamic, nonlinear, and difficult to quantify and link to appropriate economic spatial and temporal scales. This paper develops and demonstrates a method to value a portion of ecosystem services when a commercial fishery is dependent on the quality of estuarine habitat. Using a lumped-parameter, dynamic open access bioeconomic model that is spatially explicit and includes predator-prey interactions, this paper quantifies part of the value of improved ecosystem function in the Neuse River Estuary when nutrient pollution is reduced. Specifically, it traces the effects of nitrogen loading on the North Carolina commercial blue crab fishery by modeling the response of primary production and the subsequent impact on hypoxia (low dissolved oxygen). Hypoxia, in turn, affects blue crabs and their preferred prey. The discounted present value fishery rent increase from a 30% reduction in nitrogen loadings in the Neuse is $2.56 million, though this welfare estimate is fairly sensitive to some parameter values. Surprisingly, this number is not sensitive to initial conditions.

Valuing Ecosystem Services with Fishery Rents: A Lumped-Parameter Approach to Hypoxia in the Neuse River Estuary

Valuing ecosystem services with microeconomic underpinnings presents challenges because these services typically constitute nonmarket values and contribute to human welfare indirectly through a series of ecological pathways that are dynamic, nonlinear, and difficult to quantify and link to appropriate economic spatial and temporal scales. This paper develops and demonstrates a method to value a portion of ecosystem services when a commercial fishery is dependent on the quality of estuarine habitat. Using a lumped-parameter, dynamic open access bioeconomic model that is spatially explicit and includes predator-prey interactions, this paper quantifies part of the value of improved ecosystem function in the Neuse River Estuary when nutrient pollution is reduced. Specifically, it traces the effects of nitrogen loading on the North Carolina commercial blue crab fishery by modeling the response of primary production and the subsequent impact on hypoxia (low dissolved oxygen). Hypoxia, in turn, affects blue crabs and their preferred prey. The discounted present value fishery rent increase from a 30% reduction in nitrogen loadings in the Neuse is $2.56 million, though this welfare estimate is fairly sensitive to some parameter values. Surprisingly, this number is not sensitive to initial conditions.

Dynamic analysis of spiral bevel geared rotor systems applying finite elements and enhanced lumped parameters

The dynamics of spiral bevel gears like most high-speed precision gears employed in motor vehicles and off highway equipments are substantially affected by the structural characteristics of the shafts and bearings. The lumped parameter model is one of the common tools applied to perform gear dynamic analysis. Even though the lumped parameter approach is computationally fast and conveniently efficient, it typically uses limited number of coordinates and may not fully account for the shaft-bearing structural characteristics accurately. In this analysis, the finite element formulation, that can generally represent more complete characteristics of the shaft-bearing assembly, is employed to enhance the current lumped parameter synthesis theory using the concept of effective mass and inertia elements. Computational output shows that the enhanced lumped parameter synthesis model is capable of predicting sufficiently accurate dynamic response when compared to the direct dynamic finite element calculations, and much more precise response than previous lumped parameter results, especially when the gear dynamics are associated with the pinion or gear bending modes. Even though this analysis focuses primarily on the spiral bevel geared rotor systems, the proposed methodology and analysis results can be easily extended to other types of gears.

Pressure oscillation delivery to the lung: Computer simulation of neonatal breathing parameters

Preterm newborn infants may develop respiratory distress syndrome (RDS) due to functional and structural immaturity. A lack of surfactant promotes collapse of alveolar regions and airways such that newborns with RDS are subject to increased inspiratory effort and non-homogeneous ventilation. Pressure oscillation has been incorporated into one form of RDS treatment; however, how far it reaches various parts of the lung is still questionable. Since in-vivo measurement is very difficult if not impossible, mathematical modeling may be used as one way of assessment. Whereas many models of the respiratory system have been developed for adults, the neonatal lung remains essentially ill-described in mathematical models. A mathematical model is developed, which represents the first few generations of the tracheo-bronchial tree and the 5 lobes that make up the premature ovine lung. The elements of the model are derived using the lumped parameter approach and formulated in Simulink™ within the Matlab™ environment. The respiratory parameters at the airway opening compare well with those measured from experiments. The model demonstrates the ability to predict pressures, flows and volumes in the alveolar regions of a premature ovine lung.

Transfer Behavior of Heat Exchanger

This study deals with the transient response of heat exchanger which is approximated to the first-order system with delay. This function is of simple form and easy to be applied to design the practical controllers. The parameters such as gain K, time constant T and delay time are derived in this paper. On the basis of using the first-order system as the transfer function for a heat exchanger, more accurate models are built to derive the parameters K, T and respectively, which are constructed with a lumped parameter approach. Unlike a number of recent analyses K is obtained by using arithmetic mean temperature difference, log mean temperature difference has been employed instead, which minimized the error; time constant T is obtained by deriving the time constant of baffle; delay time is estimated by flow rate. The result shows that this method to study the dynamic characteristics of heat exchanger is easier, more accurate.

Development of a Customized Autopilot for Unmanned Helicopter Model Using Genetic Algorithm via the Application of Different Guidance Strategies

The objective of this paper is to develop a customized autopilot system that enables a helicopter model to carry out an autonomous flight using on-board microcontroller. The main goal of this project is to provide a comprehensive controller design methodology, Modeling, simulation, guidance and verification for an unmanned helicopter model. The autopilotsystem was designed to demonstrate autonomous maneuvers such as flying over the planned waypoints with constant forward speed and considerable steep maneuvers. For the controller design, the nonlinear dynamic model of the Remote Control helicopter was built by employing Lumped Parameter approach comprising of four different subsystems such as actuator dynamics, rotary wing dynamics, force and moment generation process and rigid body dynamics. The nonlinear helicopter mathematical model was then linearized using small perturbation theory for stability analysis and linear feedback control system design. The linear state feedback for the stabilization and control of the helicopter was derived using Pole Placement Method. The overall dynamic system control with output feedback was computed using Genetic Algorithm. Series of Matlab-Simulink models and guidance algorithms were presented in this work to simulate and verify the autopilot system performance. The proposed autopilot has shown acceptable capability of stabilizing and controlling the helicopter during tracking the desired waypoints. This paper is presenting a detailed comparison study for two different guidance strategies. The first strategy is concerning the difference between the desired heading or elevation referred to the next waypoint and the actual heading or elevation of the unmanned helicopter model. The second strategy is concerning the relative distance between the actual and the desired trajectories. In other words the first method is tracking the waypoints while the second one is tracking the trajectory. In this work a comparison study was conducted through the mentioned strategies simulation to show the significant differences in the output performance. Some performance indexes were presented to evaluate the system performance errors and the control effort needed for both strategies using the same desired trajectory and the same waypoints.

ICONE19-43654 SIMULATION OF HYDROGEN DEFLAGRATION EXPERIMENTS IN THE ENACCEF FACILITY USING ASTEC CODE

During a hypothetic severe accident in the NPP involving degradation of the core of a light water reactor, hydrogen could be generated and released into the containment atmosphere posing a deflagration or even a detonation risk. In the case of deflagration, the integrity of the containment would be threatened by the increase of the containment atmosphere pressure and temperature. Other risks of containment damage due to turbulent flames exist, caused by high pressure pulses, shock waves and etc. For the simulation of such processes a reliable numerical codes are needed. Despite flame acceleration being largely studied for homogeneous hydrogen - air mixtures, there are still unresolved issues in this research area, e.g., the effect of turbulence level on flame acceleration and quenching. This paper presents simulations of hydrogen deflagration experiments in the ENACCEF facility using ASTEC code, performed in the frames of International Standard Program No. 49 and SARNET2 project. Experiments and simulations were performed with the aim of evaluating the codes' (a number of participants with various codes participated in the project) capabilities to simulate hydrogen combustion. ASTEC code is an integral lumped-parameter approach based nuclear safety analysis code. For the presented simulations, ASTEC modules CPA (containment thermohydromechanics) and FRONT (hydrogen deflagration) were used. Paper present ENACCEF test facility, its nodalisation schemes developed for the calculations, simulated experiments and simulations' results. Brief description of FRONT module is also presented. Calculations' results are compared with experimental results and analyzed.