scholarly journals Research on Heat Transfer Dynamic Characteristics of Composite Layer Based on Laplace Transform

2019 ◽  
Author(s):  
Chunyu Xu ◽  
Junhua Lin ◽  
Wenhao Liu ◽  
Yuanbiao Zhang
Keyword(s):  
Heat Transfer ◽  
Composite Materials ◽  
Temperature Distribution ◽  
Transfer Function ◽  
Dynamic Characteristics ◽  
Transfer Functions ◽  
Composite Layer ◽  
Engineering Application ◽  
Second Order ◽  
Inverse Transformation

This paper predict and effectively control the temperature distribution of the steady-state and transient states of anisotropic four-layer composite materials online, knowing the density, specific heat, heat conductivity and thickness of the composite materials. Based on the transfer function, a mathematical model was established to study the dynamic characteristics of heat transfer of the composite materials. First of all, the Fourier heat transfer law was used to establish a one-dimensional Fourier heat conduction differential equation for each composite layer, and the Laplace transformation was carried out to obtain the system function. Then the approximate second-order transfer function of the system was obtained by Taylor expansion, and the Laplace inverse transformation was carried out to obtain the transfer function of the whole system in the time domain. Finally, the accuracy of the simplified analytical solutions of the first, second and third order approximate transfer functions was compared with computer simulation. The results showed that the second order approximate transfer functions can describe the dynamic process of heat transfer better than others. The research on the dynamic characteristics of heat transfer in the composite layer and the dynamic model of heat transfer in composite layer proposed in this paper have a reference value for practical engineering application. It can effectively predict the temperature distribution of composite layer material and reduce the cost of experimental measurement of heat transfer performance of materials.

Dynamic Observer Method Based on Modified Green’s Functions for Robust and More Stable Inverse Algorithms

2008 ◽  
Author(s):  
Priscila F. B. Sousa ◽  
Ana P. Fernandes ◽  
Vale´rio Luiz Borges ◽  
George S. Dulikravich ◽  
Gilmar Guimara˜es
Keyword(s):  
Heat Transfer ◽  
Transfer Function ◽  
Green's Functions ◽  
Transfer Functions ◽  
Green’S Functions ◽  
Three Dimensional ◽  
Original Method ◽  
Identification Algorithm ◽  
Transfer Function Model ◽  
Function Model

This work presents a modified procedure to use the concept of dynamic observers based on Green’s functions to solve inverse problems. The original method can be divided in two distinct steps: i) obtaining a transfer function model GH and; ii) obtaining heat transfer functions GQ and GN and building an identification algorithm. The transfer function model, GH, is obtained from the equivalent dynamic systems theory using Green’s functions. The modification presented here proposes two different improvements in the original technique: i) A different method of obtaining the transfer function model, GH, using analytical functions instead of numerical procedures, and ii) Definition of a new concept of GH to allow the use of more than one response temperature. Obtaining the heat transfer functions represents an important role in the observer method and is crucial to allow the technique to be directly applied to two or three-dimensional heat conduction problems. The idea of defining the new GH function is to improve the robustness and stability of the algorithm. A new dynamic equivalent system for the thermal model is then defined in order to allow the use of two or more temperature measurements. Heat transfer function, GH can be obtained numerically or analytically using Green’s function method. The great advantage of deriving GH analytically is to simplify the procedure and minimize the estimative errors.

Transfer Function Based Optimization of Film Hole Sizes With Conjugate Heat Transfer Analysis

2020 ◽  
Author(s):  
Sandip Dutta ◽  
Reid Smith
Keyword(s):  
Heat Transfer ◽  
Transfer Function ◽  
Transfer Functions ◽  
Optimization Technique ◽  
Leading Edge ◽  
Optimization Procedure ◽  
Metal Temperature ◽  
Heat Transfer Analysis ◽  
Maximum Temperature ◽  
Transfer Coefficients

Abstract With the improvements of 3D metal printing of turbine components, it is now feasible to produce ready to use production quality parts without casting and conventional machining. This new manufacturing technique has opened new frontiers in cooling optimizations that could not be practiced before. For example, it is now or in-the-near-future possible to have unconventional diameters of film holes. This paper seeks to optimize each film hole diameter at the leading edge of a turbine to achieve an optimum thermal objective. The design technique developed uses a transfer function-based learning model and can be used for both stationary and rotating airfoils. Proposed optimization procedure will also work on other parts of an airfoil; but our current analysis is limited to the leading-edge region. To apply this work on other critical regions, the corresponding heat transfer coefficients need to be implemented while building the transfer functions suitable for that specific component; however, the underlying optimization technique stays the same for any other component. Any optimization technique needs cost and benefit criteria. Cost is minimized in optimization to get maximum benefit with given constraints. In gas-turbine heat transfer, there is a ceiling constraint on maximum temperature that must be satisfied. This study minimizes the coolant flow with satisfying the constraints on average metal temperature and metal temperature variations that limit the life of turbine components. Proposed methodology provides a scientific basis for the sizing of film holes and is expected to decrease developmental cost of efficient thermal designs.

Model Reduction of Transfer Functions Using a Dominant Root Method

1990 ◽  
Vol 112 (3) ◽  
pp. 547-554 ◽  
Author(s):  
J. E. Seem ◽  
S. A. Klein ◽  
W. A. Beckman ◽  
J. W. Mitchell
Keyword(s):  
Heat Transfer ◽  
Transfer Function ◽  
Model Reduction ◽  
Transfer Functions ◽  
Linear Time ◽  
Padé Approximation ◽  
Computational Effort ◽  
Pade Approximation ◽  
Bilinear Transformation ◽  
Transfer Problems

Transfer function methods are more efficient for solving long-time transient heat transfer problems than Euler, Crank-Nicolson, or other classical techniques. Transfer functions relate the output of a linear, time-invariant system to a time series of current and past inputs, and past outputs. Inputs are modeled by a continuous, piecewise linear curve. The computational effort required to perform a simulation with transfer functions can be significantly decreased by using the Pade´ approximation and bilinear transformation to determine transfer functions with fewer coefficients. This paper presents a new model reduction method for reducing the number of coefficients in transfer functions that are used to solve heat transfer problems. There are two advantages of this method over the Pade´ approximation and bilinear transformation. First, if the original transfer function is stable, then the reduced transfer function will also be stable. Second, reduced multiple-input single-output transfer functions can be determined by this method.

scholarly journals Validation of Fractional-Order Lowpass Elliptic Responses of (1 + α)-Order Analog Filters

2018 ◽  
Vol 8 (12) ◽  
pp. 2603 ◽  
Author(s):  
David Kubanek ◽  
Todd Freeborn ◽  
Jaroslav Koton ◽  
Jan Dvorak
Keyword(s):  
Transfer Function ◽  
Least Squares ◽  
Fractional Order ◽  
Frequency Band ◽  
Operational Amplifier ◽  
Transfer Functions ◽  
Second Order ◽  
Experimental Results ◽  
Analog Filters ◽  
Lowpass Filter

In this paper, fractional-order transfer functions to approximate the passband and stopband ripple characteristics of a second-order elliptic lowpass filter are designed and validated. The necessary coefficients for these transfer functions are determined through the application of a least squares fitting process. These fittings are applied to symmetrical and asymmetrical frequency ranges to evaluate how the selected approximated frequency band impacts the determined coefficients using this process and the transfer function magnitude characteristics. MATLAB simulations of ( 1 + α ) order lowpass magnitude responses are given as examples with fractional steps from α = 0.1 to α = 0.9 and compared to the second-order elliptic response. Further, MATLAB simulations of the ( 1 + α ) = 1.25 and 1.75 using all sets of coefficients are given as examples to highlight their differences. Finally, the fractional-order filter responses were validated using both SPICE simulations and experimental results using two operational amplifier topologies realized with approximated fractional-order capacitors for ( 1 + α ) = 1.2 and 1.8 order filters.

A Novel Method of Transfer-Function Identification for Unknown Systems

2013 ◽  
Vol 321-324 ◽  
pp. 1967-1970
Author(s):  
Chung Neng Huang ◽  
Chen Min Cheng
Keyword(s):  
Transfer Function ◽  
Electromechanical Coupling ◽  
High Efficiency ◽  
Transfer Functions ◽  
Second Order ◽  
System A ◽  
Derivative Free ◽  
Efficiency Control ◽  
Novel Method ◽  
Free Search

This study proposes a new modeling method for unknown systems. Through this method, the transfer functions can be identified. First, the input-output data pairs of the unidentified system should be collected. Then, the transfer function’s coefficients can be identified based on the errors via the derivative-free search methods such as GA etc. Here, a second-order transfer function is used in this study. For a second-order transfer function is difficult to approach each system, a plurality of transfer functions may be used depending on the precise requirement. Finally, following the previous steps, the other transfer function can be found in succession. In order to confirm the effectiveness of this proposed method, an electromagnetic flywheel (EF) system is used in this study. Such kinds of systems are always with many uncertainties as nonlinear electromechanical coupling and electromagnetic saturation, etc. They are difficult to modeling via traditional mathematic ways. In this study, the data pairs of EF system is collected by experiments. By assessing the results of the proposal and experimental data shows that this method is feasible to any unknown systems. system, achieve more saving energy and high efficiency control purposes.

scholarly journals Estimation of Transfer Function Coefficients for Second-Order Systems via Metaheuristic Algorithms

Sensors ◽  
2021 ◽  
Vol 21 (13) ◽  
pp. 4529
Author(s):  
Omar Rodríguez-Abreo ◽  
Juvenal Rodríguez-Reséndiz ◽  
Francisco Antonio Castillo Velásquez ◽  
Alondra Anahi Ortiz Verdin ◽  
Juan Manuel Garcia-Guendulain ◽  
...  
Keyword(s):  
Transfer Function ◽  
Transfer Functions ◽  
Standard Form ◽  
Estimation Method ◽  
Second Order ◽  
Parametric Estimation ◽  
Metaheuristic Algorithms ◽  
Step Response ◽  
Gray Wolf ◽  
Final Value

The present research develops the parametric estimation of a second-order transfer function in its standard form, employing metaheuristic algorithms. For the estimation, the step response with a known amplitude is used. The main contribution of this research is a general method for obtaining a second-order transfer function for any order stable systems via metaheuristic algorithms. Additionally, the Final Value Theorem is used as a restriction to improve the velocity search. The tests show three advantages in using the method proposed in this work concerning similar research and the exact estimation method. The first advantage is that using the Final Value Theorem accelerates the convergence of the metaheuristic algorithms, reducing the error by up to 10 times in the first iterations. The second advantage is that, unlike the analytical method, it is unnecessary to estimate the type of damping that the system has. Finally, the proposed method is adapted to systems of different orders, managing to calculate second-order transfer functions equivalent to higher and lower orders. Response signals to the step of systems of an electrical, mechanical and electromechanical nature were used. In addition, tests were carried out with simulated signals and real signals to observe the behavior of the proposed method. In all cases, transfer functions were obtained to estimate the behavior of the system in a precise way before changes in the input. In all tests, it was shown that the use of the Final Value Theorem presents advantages compared to the use of algorithms without restrictions. Finally, it was revealed that the Gray Wolf Algorithm has a better performance for parametric estimation compared to the Jaya algorithm with an error up to 50% lower.

A Numerical Evaluation of the Quadratic Transfer Function for a Floating Structure

2019 ◽  
Author(s):  
Zhitian Xie ◽  
Yujie Liu ◽  
Jeffrey Falzarano
Keyword(s):  
Transfer Function ◽  
Frequency Domain ◽  
Transfer Functions ◽  
Second Order ◽  
Wave Frequency ◽  
Wave Forces ◽  
Floating Structure ◽  
Transfer Function Matrix ◽  
Wave Induced ◽  
Function Matrix

Abstract The second order force of a floating structure can be expressed in terms of a time independent quadratic transfer functions along with the incident wave elevation, through which it is possible to evaluate the second order wave exciting forces in the frequency domain. Newman’s approximation has been widely applied in approximating the elements of the quadratic transfer function matrix while numerically evaluating the second order wave induced force. Through Newman’s approximation, the off-diagonal elements can be numerically approximated with the diagonal elements and thus the numerical calculation efficiency can be enhanced. Newman’s approximation assumes that the off-diagonal elements do not change significantly with the wave frequency and that hydrodynamic phenomenon regarding the low difference frequency are usually of interest. However, it is obviously less satisfying when an element that is close to the diagonal line in the quadratic transfer function matrix shows an extremum if the corresponding wave frequency is close to the natural frequency of the certain motion. In this paper, the full derivation and expression of the second order wave forces and moments applied to a floating structure have been presented, through which the numerical results of the quadratic transfer function matrix including the diagonal and the off-diagonal elements will be illustrated. This work will present the basis of numerically evaluating the second order forces in the frequency domain. The comparisons among various approximations regarding the second order forces in deep water will also be presented as a meaningful reference.

scholarly journals Experimental Study of the Direct Drive Hydraulic System with the Torque Mode

Energies ◽  
2021 ◽  
Vol 14 (4) ◽  
pp. 941
Author(s):  
Chenyang Zhang ◽  
Hongzhou Jiang
Keyword(s):  
Transfer Function ◽  
Dynamic Characteristics ◽  
Control Strategy ◽  
Hydraulic System ◽  
Parallel Mechanism ◽  
Dynamic Pressure ◽  
Second Order ◽  
Direct Drive ◽  
Pressure Feedback ◽  
Speed Mode

The torque mode is more suitable for the direct drive 6 degree of freedom (6-DOF) parallel mechanism than the speed mode that both dynamic coupling and current coupling among motors are easily solved, but its key parameters and dynamic characteristics have never been studied, which are important and are the goals of this paper. First the hydraulic system of the direct drive 6-DOF parallel mechanism is simplified. Then the transfer function of the direct drive hydraulic system with the torque mode is deduced together with that of the speed mode. Finally, comparative experiments are conducted. Results show that the dynamic characteristics of the system with the torque mode which are generally worse than those with the speed mode, are mainly determined by the parameters of the motor-pump second-order element of the transfer function composed of two under-damped second-order elements, proportion differentiation (PD) control strategy and dynamic pressure feedback (DPF) control strategy are useful for the system with the torque mode, but practical and effective methods are still needed.

Multimode Vibrations Suppression Compensators Design Using Specified Dynamic Performance Reference Models

2012 ◽  
Vol 463-464 ◽  
pp. 1125-1128
Author(s):  
Marius Sebastian Rusu ◽  
Lucian Grama
Keyword(s):  
Transfer Function ◽  
Dynamic Behavior ◽  
Transfer Functions ◽  
Reference Model ◽  
Dynamic Performance ◽  
Second Order ◽  
Model Parameters ◽  
Mechatronic Systems ◽  
Parallel Connection ◽  
Reference Models

This paper presents a method of designing vibration compensators for linear mechatronic systems based on their inverse multimodal representation and a customized second order transfer function embedding the specified dynamic behavior. The linear non-compensated system is modeled by a parallel connection of independent second order transfer functions. There are four flavors of compensators described in this paper, each having a different choice of the reference model parameters. A brief numerical example is also provided.

Dynamic characteristics of baroreflex neural and peripheral arcs are preserved in spontaneously hypertensive rats

2011 ◽  
Vol 300 (1) ◽  
pp. R155-R165 ◽  
Author(s):  
Toru Kawada ◽  
Shuji Shimizu ◽  
Atsunori Kamiya ◽  
Yusuke Sata ◽  
Kazunori Uemura ◽  
...  
Keyword(s):  
Transfer Function ◽  
Dynamic Characteristics ◽  
Spontaneously Hypertensive Rats ◽  
Transfer Functions ◽  
Carotid Sinus ◽  
Hypertensive Rats ◽  
Spontaneously Hypertensive ◽  
Carotid Sinus Baroreflex ◽  
Low Pass ◽  
Dynamic Gain

Although baroreceptors are known to reset to operate in a higher pressure range in spontaneously hypertensive rats (SHR), the total profile of dynamic arterial pressure (AP) regulation remains to be clarified. We estimated open-loop transfer functions of the carotid sinus baroreflex in SHR and Wistar Kyoto (WKY) rats. Mean input pressures were set at 120 (WKY120 and SHR120) and 160 mmHg (SHR160). The neural arc transfer function from carotid sinus pressure to efferent splanchnic sympathetic nerve activity (SNA) revealed derivative characteristics in both WKY and SHR. The slope of dynamic gain (in decibels per decade) between 0.1 and 1 Hz was not different between WKY120 (10.1 ± 1.0) and SHR120 (10.4 ± 1.1) but was significantly greater in SHR160 (13.2 ± 0.8, P < 0.05 with Bonferroni correction) than in SHR120. The peripheral arc transfer function from SNA to AP showed low-pass characteristics. The slope of dynamic gain (in decibels per decade) did not differ between WKY120 (−34.0 ± 1.2) and SHR120 (−31.4 ± 1.0) or between SHR120 and SHR160 (−32.8 ± 1.3). The total baroreflex showed low-pass characteristics and the dynamic gain at 0.01 Hz did not differ between WKY120 (0.91 ± 0.08) and SHR120 (0.84 ± 0.13) or between SHR120 and SHR160 (0.83 ± 0.11). In both WKY and SHR, the declining slope of dynamic gain was significantly gentler for the total baroreflex than for the peripheral arc, suggesting improved dynamic AP response in the total baroreflex. In conclusion, the dynamic characteristics of AP regulation by the carotid sinus baroreflex were well preserved in SHR despite significantly higher mean AP.

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