On the dynamics of the two-for-one twister

1993 ◽  
Vol 442 (1915) ◽  
pp. 409-425 ◽  
Keyword(s):  
Mathematical Model ◽  
Bifurcation Diagram ◽  
Operating Conditions ◽  
Bifurcation Parameter ◽  
Cylinder Radius ◽  
Tension Level ◽  
Constant Tension ◽  
The Mathematical Model ◽  
Control Cylinder ◽  
Nonlinear Nature

The mathematical model of the two-for-one twister described in this paper extends the previous work of V. K. Kothari and G. A. V. Leaf. A more realistic analysis of the action of the storage cylinder and over-run plate is made, and the effect of the balloon-control cylinder is modelled. Attention is focused on the role played by the ballooning yarn in regulating the tension and producing a constant tension level at the guide eye under steady operating conditions. The model is used to simulate the operation of the two-for-one twister, with and without the balloon-control cylinder. The essential nonlinear nature of the free balloon problem is demonstrated through the bifurcation diagram, which shows guide-eye tension against storage-cylinder radius used as the bifurcation parameter.

scholarly journals Performance Evaluation of a Gravity-Assisted Heat Pipe-Based Indirect Evaporative Cooler

Energies ◽  
2020 ◽  
Vol 13 (1) ◽  
pp. 200 ◽  
Author(s):  
Krzysztof Rajski ◽  
Jan Danielewicz ◽  
Ewa Brychcy
Keyword(s):  
Mathematical Model ◽  
Heat Pipe ◽  
Cooling Capacity ◽  
Operating Conditions ◽  
Coefficient Of Performance ◽  
Mass Transfer Processes ◽  
Air Cooler ◽  
Evaporative Cooler ◽  
The Mathematical Model ◽  
Further Development

In the present work, the effects of different operating parameters on the performance of a gravity-assisted heat pipe-based indirect evaporative cooler (GAHP-based IEC) were investigated. The aim of the theoretical study is to evaluate accurately the cooling performance indicators, such as the coefficient of performance (COP), wet bulb effectiveness, and cooling capacity. To predict the effectiveness of the air cooler under a variety of conditions, the comprehensive calculation method was adopted. A mathematical model was developed to simulate numerically the heat and mass transfer processes. The mathematical model was validated adequately using experimental data from the literature. Based on the conducted numerical simulations, the most favorable ranges of operating conditions for the GAHP-based IEC were established. Moreover, the conducted studies could contribute to the further development of novel evaporative cooling systems employing gravity-assisted heat pipes as efficient equipment for transferring heat.

scholarly journals Global and Local Structures of Bifurcation Curves of ODE with Nonlinear Diffusion

2018 ◽  
Vol 2018 ◽  
pp. 1-7
Author(s):  
Tetsutaro Shibata
Keyword(s):  
Mathematical Model ◽  
Eigenvalue Problem ◽  
Nonlinear Diffusion ◽  
Nonlinear Term ◽  
Nonlinear Eigenvalue Problem ◽  
Maximum Norm ◽  
Bifurcation Parameter ◽  
Local Structures ◽  
Global And Local ◽  
The Mathematical Model

We consider the nonlinear eigenvalue problem Duu′′+λfu=0, u(t)>0, t∈I≔(0,1), u(0)=u(1)=0, where D(u)=uk, f(u)=u2n-k-1+sin⁡u, and λ>0 is a bifurcation parameter. Here, n∈N and k (0≤k<2n-1) are constants. This equation is related to the mathematical model of animal dispersal and invasion, and λ is parameterized by the maximum norm α=uλ∞ of the solution uλ associated with λ and is written as λ=λ(α). Since f(u) contains both power nonlinear term u2n-k-1 and oscillatory term sin⁡u, it seems interesting to investigate how the shape of λ(α) is affected by f(u). The purpose of this paper is to characterize the total shape of λ(α) by n and k. Precisely, we establish three types of shape of λ(α), which seem to be new.

Study on Control Characteristics of Driving and Lifting System for Logistics and Loading Machinery

2012 ◽  
Vol 268-270 ◽  
pp. 1517-1522 ◽  
Author(s):  
Guo Jin Chen ◽  
Ting Ting Liu ◽  
Ni Jin ◽  
You Ping Gong ◽  
Huo Qing Feng
Keyword(s):  
Mathematical Model ◽  
Dynamic Characteristics ◽  
Optimization Design ◽  
Integrated System ◽  
Operating Conditions ◽  
Control Methods ◽  
Lifting System ◽  
The Mathematical Model ◽  
Power Match

The logistics and loading machinery is the typical hydromechatronics integrated system. How to solve the reasonable power match in the driving and lifting process of the logistics and loading machinery, we need to establish the mathematical model of the driving and lifting system, and analyze their control characteristics. Aiming at the load requirements for different operating conditions, this paper studies respectively the dynamic characteristics of the driving and lifting system. Through simulation and computation, the control methods and strategies based on the best performance are proposed. That lays the foundation for the optimization design of the logistics and loading machinery.

scholarly journals The Mathematical Model and Numerical Study of Heat and Mass Transfer Processes in the Combustion Chamber of Diesel-Generator Units with a Valve-Inductor Generator

2020 ◽  
pp. 611-625
Author(s):  
Dmitriy V. Guzei ◽  
Andrey V. Minakov ◽  
Vasiliy I. Panteleev ◽  
Maksim I. Pryazhnikov ◽  
Dmitriy V. Platonov ◽  
...  
Keyword(s):  
Mathematical Model ◽  
Mass Transfer ◽  
Combustion Chamber ◽  
Heat And Mass Transfer ◽  
Operating Conditions ◽  
Diesel Generator ◽  
Transfer Processes ◽  
Mass Transfer Processes ◽  
Actual Geometry ◽  
The Mathematical Model

The mathematical model of heat and mass transfer processes in the combustion chamber of diesel generator units with valve inductor generators has been developed. The mathematical model takes into account the actual geometry of the combustion chamber and the operating conditions of the diesel engine. A study of the main characteristics of a diesel generator in a wide range of modes of operation has been carried out. In addition to energy characteristics, environmental parameters have been considered

Improving the Performance of a Two Way Flow Control Valve, Using a 3D CFD Modeling

2014 ◽  
Author(s):  
Emma Frosina ◽  
Adolfo Senatore ◽  
Dario Buono ◽  
Michele Pavanetto ◽  
Micaela Olivetti ◽  
...  
Keyword(s):  
Mathematical Model ◽  
Flow Control ◽  
Fluid Dynamic ◽  
Control Valve ◽  
Operating Conditions ◽  
Cfd Modeling ◽  
Flow Control Valve ◽  
Development Costs ◽  
Definition Of ◽  
The Mathematical Model

The paper introduces a methodology aimed to optimize the performance of hydraulic components; in particular the design of a new two way flow control valve studying the valve internal fluid-dynamic behavior will be introduced. The methodology is based on the definition of a CFD tridimensional fluid-dynamic model. In fact, the model can help engineers to develop the best geometry, to optimize the valve performance, reducing the prototyping requirement and finally the time-to-market and, consequently, the development costs. At first, the original spool internal geometry has been evaluated and studied to tune the mathematical model and to validate it comparing its results with the data obtained through an experimental campaign. Then, the same approach has been applied to investigate several different internal spool geometries to define the best one in all operating conditions. A limited number of solutions have been prototyped and tested to verify the mathematical model predictions, in order to find the best configuration whose performances are consistent with the assigned objective for the component.

Modeling Carbon Monoxide Direct Oxidation in Solid Oxide Fuel Cells

2009 ◽  
Vol 6 (2) ◽  
Author(s):  
Luca Andreassi ◽  
Claudia Toro ◽  
Stefano Ubertini
Keyword(s):  
Mathematical Model ◽  
Carbon Monoxide ◽  
Solid Oxide Fuel Cells ◽  
Operating Conditions ◽  
Solid Oxide ◽  
Direct Oxidation ◽  
Fuel Cell Performance ◽  
The Mathematical Model ◽  
Oxidation Of Carbon Monoxide ◽  
Made In

In the present study, the results of the numerical implementation of a mathematical model of a planar anode-supported SOFC are reported. In particular, model results are validated and discussed when the fuel is a mixture of hydrogen and carbon monoxide, focusing on the importance of simulating direct oxidation of carbon monoxide. The mathematical model is solved in a 3D environment and the key issue is the validation comparing with experimental data, which is made in different operating conditions to establish the reliability of the presented model. The results show the importance of simulating direct oxidation of carbon monoxide and its effect on the fuel cell performance.

scholarly journals Procedure for the quantification of the degradation index of Photovoltaic Generators

2021 ◽  
Vol 2 (2) ◽  
pp. 47-53
Author(s):  
Proenza Y. Roger ◽  
Camejo C. José Emilio ◽  
Ramos H. Rubén
Keyword(s):  
Mathematical Model ◽  
Power Generation ◽  
Solar Energy ◽  
Operating Conditions ◽  
Energy Research ◽  
Degradation Index ◽  
Starting Point ◽  
Santiago De Cuba ◽  
Photovoltaic Generators ◽  
The Mathematical Model

A procedure is presented for the quantification of the degradation index of Photovoltaic Generators, based on the quantification of the operational losses inherent in the system, which allows maintaining the nominal operating conditions and by the warranty terms of the photovoltaic generator. A photovoltaic generator connected to the network with a nominal power of 7.5 kWp, installed in the Solar Energy Research Center of Santiago de Cuba, is used to evaluate and validate the procedure. The starting point is the mathematical model of the photovoltaic generator, then the operational losses of the photovoltaic generator are quantified and the mathematical model is adjusted to real conditions, through a polynomial adjustment.  The results obtained show that the photovoltaic generator presents deviations in terms of the nominal power generation, because the operational losses are 7% with respect to the values ​​given by the manufacturer.

Effects of Heat Accumulation on the Thermodynamic and Economic Performance of CHP

2001 ◽  
Author(s):  
Jozef Portacha ◽  
Adam Smyk ◽  
Alicja Zielinska ◽  
Jerzy K. Fiszdon
Keyword(s):  
Mathematical Model ◽  
Numerical Method ◽  
Economic Performance ◽  
Electrical Energy ◽  
Operating Conditions ◽  
Electricity Production ◽  
Heat Accumulation ◽  
Heat Accumulator ◽  
The Mathematical Model

Abstract Heat accumulation in cogenerating plants allows increased electricity production during highest demand period. It also causes change of the overall electricity production. Changes in cogeneration coefficient follow the same trend. This paper examines the effect on the average cogeneration factor caused by adding the heat accumulator to the existing CHP. Variation of this coefficient influences the plant economics, since electrical energy is most expensive during the peak hours. In the model presented the operating conditions vary due to variations in the surroundings temperature and due to cyclical operation of the heat accumulator. Assumptions made, the mathematical model, and numerical method used are also presented.

A Theoretical-Experimental Method for Analyzing the Dynamic Behavior of Elastomeric Lip Seals

1987 ◽  
Vol 60 (1) ◽  
pp. 176-189 ◽  
Author(s):  
Edzeario Prati
Keyword(s):  
Mathematical Model ◽  
Experimental Method ◽  
Dynamic Behavior ◽  
Operating Conditions ◽  
Inertial Effects ◽  
Contact Conditions ◽  
Lip Seals ◽  
Rotating Shafts ◽  
The Mathematical Model

Abstract An analytical-experimental method has been presented, which permits the dynamic behavior of lip seals for rotating shafts to be analyzed in the presence of both interference and static and dynamic eccentricities. A mathematical model which accounts for viscoelastic and inertial effects, permits determination of the lip—shaft contact conditions, the dynamic lip profile, and the gap area for various shaft speeds. The parameters which define the mathematical model have been determined experimentally. Such a model permits the performance of the particular seal studied to be predicted for various operating conditions. Finally, the influence of parameters characterizing the viscoelastic and inertial effects on the gap area have been examined. The analytical findings correlate well with the experimental measurements of fluid leakage for practically relevant values of the shaft angular velocity.

scholarly journals Experience in modeling a comfortable environment in the transport compartment

2020 ◽  
Vol 157 ◽  
pp. 01019
Author(s):  
Vladimir Pankratov ◽  
Alexey Golikov ◽  
Elena Pankratova ◽  
Marina Barulina ◽  
Sofiya Galkina
Keyword(s):  
Mathematical Model ◽  
Operating Conditions ◽  
Temperature Fields ◽  
Thermal Processes ◽  
Passenger Compartment ◽  
The Public ◽  
Actual Operating ◽  
Specific Proposal ◽  
Series Of Experiments ◽  
The Mathematical Model

The theoretical base was developed and the mathematical model of dynamic thermal processes in a compartment of public transport was constructed. The software which is realized the constructed mathematical model was developed. The mathematical model provides for the possibility of taking into account the most possible environmental conditions which can have place in the actual operating conditions of a transport even the angle of illumination - the current temperature of the external environment, the presence of solar radiation taking into account the angle of sun’s illumination, and the temperature of the roadway. The software allows calculation and visualization non –stationary temperature fields in the public transport’s compartments using the example of a trolley bus. For a specific trolley bus design, a series of experiments to calculate the comfortable temperature for passengers were conducted, These experiments are showed the performance of the constructed model and allowed to formulate a specific proposal for improving the thermoregulation system of the trolleybus’ passenger compartment.

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