Application of Transfer Functions to Canned Tuna Fish Thermal Processing

2010 ◽  
Vol 16 (1) ◽  
pp. 43-51 ◽  
Author(s):  
M.R. Ansorena ◽  
C. del Valle ◽  
V.O. Salvadori
Keyword(s):  
Transfer Function ◽  
Thermal Processing ◽  
Dynamic Models ◽  
Transfer Functions ◽  
Control Strategies ◽  
Sampling Interval ◽  
Computational Effort ◽  
Operating Conditions ◽  
Tuna Fish ◽  
External Conditions

Design and optimization of thermal processing of foods need accurate dynamic models to ensure safe and high quality food products. Transfer functions had been demonstrated to be a useful tool to predict thermal histories, especially under variable operating conditions. This work presents the development and experimental validation of a dynamic model (discrete transfer function) for the thermal processing of tuna fish in steam retorts. Transfer function coefficients were obtained numerically, using commercial software of finite elements (COMSOL Multiphysics) to solve the heat transfer balance. Dependence of transfer function coefficients on the characteristic dimensions of cylindrical containers (diameter and height) and on the sampling interval is reported. A simple equation, with two empirical parameters that depends on the container dimensions, represented the behavior of transfer function coefficients with very high accuracy. Experimental runs with different size containers and different external conditions (constant and variable retort temperature) were carried out to validate the developed methodology. Performance of the thermal process simulation was tested for predicting internal product temperature of the cold point and lethality and very satisfactory results were found. The developed methodology can play an important role in reducing the computational effort while guaranteeing accuracy by simplifying the calculus involved in the solution of heat balances with variable external conditions and emerges as a potential approach to the implementation of new food control strategies leading not only to more efficient processes but also to product quality and safety.

A new system configuration design and power management strategies for a multi-source hybrid truck

2018 ◽  
Vol 232 (8) ◽  
pp. 1053-1062 ◽  
Author(s):  
Zhenhe Li ◽  
Yanjun Huang ◽  
Hong Wang
Keyword(s):  
Fuel Consumption ◽  
Power Management ◽  
Hybrid System ◽  
Dynamic Models ◽  
Control Strategies ◽  
Management Strategies ◽  
Operating Conditions ◽  
System Structure ◽  
System Configuration ◽  
Power Management Strategy

In this article, a novel system configuration with multiple energy sources is proposed for a hybrid truck in order to reduce fuel consumption and overcome the drawbacks of using a single energy source. The energy-saving characteristics of the hybrid system can be displayed after analyzing its system structure and performances. In order to validate the advantages of this presented system, the dynamic models of the system components are established in a MATLAB/Simulink environment, and initial and improved power management strategies with rule-based algorithms are developed. Then, the hybrid system is simulated based on the models and control strategies over the urban dynamometer driving schedule driving cycle. The simulation results show that the fuel consumption employing the initial power management strategy is 12.49 L/100 km, and there is a significant decrease with around 13.6% based on the improved strategy. The results also verify that the better fuel economy can be achieved by the proposed multi-source system compared to the counterparts under the same operating conditions.

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 Simulation of the performance of alternative refrigerants in liquid chillers

2001 ◽  
Vol 215 (4) ◽  
pp. 429-441 ◽  
Author(s):  
I. N. Grace ◽  
S. A. Tassou
Keyword(s):  
Dynamic Models ◽  
Control Strategies ◽  
Cooling Capacity ◽  
Operating Conditions ◽  
Coefficient Of Performance ◽  
System Component ◽  
Alternative Refrigerants ◽  
Expansion Valve ◽  
Shell And Tube Evaporator ◽  
The Impact

The impact of refrigeration systems on the environment can be reduced by (a) the use of alternative refrigerants which are less harmful to the environment and (b) the optimization of systems and control strategies to deliver increased levels of energy efficiency. Mathematical modelling offers the opportunity to test the performance of systems under different operating conditions and with alternative refrigerants. Dynamic models allow comparison of both transient and steady state behaviour and this is of particular importance for liquid chillers since these systems can operate under transient conditions for long periods. This paper covers the development of a general dynamic model for the simulation of liquid chillers. Brief descriptions of the system component models are given, including a semihermetic reciprocating compressor and thermostatic expansion valve as well as a shell-and-tube evaporator and condenser. The paper demonstrates the application of the model to simulate the performance of a liquid chiller retrofitted with a range of alternative refrigerants. The performance of the system is determined in terms of cooling capacity, power consumption and coefficient of performance for a range of different operating conditions. The relative performance of each refrigerant is discussed and the preferred alternative identified for typical applications.

Rational transfer function models for nitrifying trickling filters

1999 ◽  
Vol 39 (4) ◽  
pp. 121-128 ◽  
Author(s):  
T. Wik
Keyword(s):  
Transfer Function ◽  
Dynamic Models ◽  
Transfer Functions ◽  
Controller Design ◽  
Ammonium Concentration ◽  
Trickling Filters ◽  
Rational Transfer ◽  
Simulated Effluent ◽  
Function Models ◽  
Transfer Function Models

An important step towards optimization and control of wastewater treatment plants is the development of dynamic models and efficient methods of simulation. Using standard simplifying assumptions, non-rational transfer function models describing the fast dynamics of nitrifying trickling filters, are derived. With a method based on the location of their singularities, it is shown how low order rational transfer functions can approximate the non-rational ones. These transfer functions can be used in efficient simulation routines and in standard methods of controller design. Effluent concentrations from trace substance pulse response experiments and an experiment with varying flow and varying influent ammonium concentration carried out on a large pilot plant NTF show close agreement with simulated effluent concentrations using the rational transfer functions.

scholarly journals UAV generalized longitudinal model for autopilot controller designs

2021 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Eduard Bertran ◽  
Paula Tercero ◽  
Alex Sànchez-Cerdà
Keyword(s):  
Transfer Function ◽  
State Space ◽  
Transfer Functions ◽  
Control Strategies ◽  
Finite Element Method Simulation ◽  
Model Parameters ◽  
Strong Wind ◽  
State Variables ◽  
Content Type ◽  
Short Period

Purpose This paper aims to overcome the main obstacle to compare the merits of the different control strategies for fixed-wing unmanned aerial vehicles (UAVs) to assess autopilot performances. Up to now, the published studies of control strategies have been carried out over disperse models, thus being complicated, if not impossible, to compare the merits of each proposal. The authors present a worked benchmark for autopilots studies, consisting of generalized models obtained by merging UAVs’ parameters gathered from selected literature (journals) with other parameters directly obtained by the authors to include some relevant UAVs whose models are not provided in the literature. To obtain them it has been used a dedicated software (from U.S. Air Force). Design/methodology/approach The proposed models have been constructed by averaging both the main aircraft defining parameters (model derivatives) and pole-zero locations of longitudinal transfer functions. The suitability of the used methodologies has been checked from their capability to fit the short period and the phugoid modes. Previous analytical model arrangement has been required to match a uniform set of parameters, as the inner state variables are neither the same along the different published models nor between the additional models the authors have here contributed. Besides, moving models between the space state representation and transfer function is not just a simple averaging process, as neither the parameters nor the model orders are the same in the different published works. So, the junction of the models to a common set of parameters requires some residual’s computation and transient responses assessment (even Fourier analysis has been included to preserve the dominance of the phugoid) to keep the main properties of the models. The least mean squares technique has been used to have better fittings between SISO model parameters with state–space ones. Findings Both the SISO (Laplace) and state-space models for the longitudinal transfer function of an “averaged” fixed-wing UAV are proposed. Research limitations/implications More complicated situations, such as strong wind conditions, need another kind of models, usually based on finite element method simulation. These particular models apply fluid dynamics to study aerostructural aircraft aspects, such as flutter and other aerolastic aspects, the behavior under icing conditions or other distributed parameter problems. Even some models aim to control other aspects than the autopilot, such as the trajectory prediction. However, these models are not the most suitable for the basic UAV autopilot design (early design), so they are outside the objective of this paper. Obviously, the here-considered UAVs are not all the existing ones, but the number is large enough to consider the result as a reliable and realistic representation. The presented study may be seen as a stepping stone, allowing to include other UAVs in future works. Practical implications The proposed models can be used as benchmarks, or as a previous step to produce improved benchmarks, in order to have a common and realistic scenario the compare the benefits of the different control actions in UAV autopilots continuously presented in the published research. Originality/value A work with the scope of the presented one, merging model parameters from literature with other (often referred in papers and websites) whose parameters have been obtained by the authors has been never published.

Pressure Influence on the Flame Transfer Function of a Premixed Swirling Flame

2006 ◽  
Author(s):  
E. Freitag ◽  
H. Konle ◽  
M. Lauer ◽  
C. Hirsch ◽  
T. Sattelmayer
Keyword(s):  
High Pressure ◽  
Transfer Function ◽  
High Speed ◽  
Transfer Functions ◽  
Ambient Pressure ◽  
Operating Conditions ◽  
Phase Lag ◽  
Operating Pressure ◽  
Common Procedure ◽  
Wide Range

In order to assess the stability of gas turbine combustors measured flame transfer functions are frequently used in thermoacoustic network models. Although many combustion systems operate at high pressure, the measurement of flame transfer functions was essentially limited to atmospheric conditions in the past. With the test rig employed in the study presented in the paper transfer function measurements were made for a wide range of combustor pressures. The results show similarities of the amplitude response in the entire pressure range investigated. However, the increase of the pressure leads to a considerable amplitude gain at higher frequencies. In the low frequency regime the phase is also independent of pressure, whereas above this region the pressure increase results in a considerably smaller phase lag. These observations are particularly important when evaluating Rayleigh’s criterion: Interestingly, the choice of the operating pressure can render a system stable or unstable, so that the common procedure of applying flame transfer functions measured at ambient pressure for the high pressure engine case may not always be appropriate. The detailed analysis of high speed camera images, which were recorded to get locally resolved information on the flame response reveal different regions of activity within the flame that change in strength, size and location with changing operating conditions. The observed transfer function phase behavior is explained by the interaction of those regions and it is shown that the region of highest dynamic activity dominates the phase.

The Effect of Confinement on the Structure and Dynamic Response of Lean-Premixed, Swirl-Stabilized Flames

2015 ◽  
Author(s):  
Alexander J. De Rosa ◽  
Stephen J. Peluso ◽  
Bryan D. Quay ◽  
Domenic A. Santavicca
Keyword(s):  
Transfer Function ◽  
Strouhal Number ◽  
Transfer Functions ◽  
Flame Structure ◽  
Major Effect ◽  
Expansion Ratio ◽  
Forced Response ◽  
Operating Conditions ◽  
Lean Premixed ◽  
Wall Interaction

The effect of flame-wall interaction on the forced response of a lean-premixed, swirl-stabilized flame is experimentally investigated by examining flames in a series of three combustors, each with a different diameter and therefore a different degree of lateral confinement. The confinement ratios tested are 0.5, 0.37 and 0.29 when calculated using the diameter of the nozzle relative to the combustor diameter. Using both flame images and measured flame transfer functions, the effect of confinement is investigated and generalized across a broad range of operating conditions. The major effect of confinement is shown to be a change in flame structure in both the forced and unforced cases. This effect is captured using the parameter Lf,CoHR/Dcomb, which describes the changing degree of flame-wall interaction in each combustor size. The measured flame transfer function data, as a function of confinement, is then generalized by Strouhal number. Data from the two larger combustors is collapsed by multiplying the Strouhal number by the confinement ratio to account for the flow expansion ratio and change in convective velocity within the combustor. Trends at the transfer function extrema are also assessed by examining them in the context of confinement and by using flame images. A change in the fluctuating structure of the flame is also seen to result from an increase in confinement.

Mixture-Forced Flame Transfer Function Measurements and Mechanisms in a Single-Nozzle Combustor at Elevated Pressure

2011 ◽  
Author(s):  
Nick Bunce ◽  
Jong Guen Lee ◽  
Bryan D. Quay ◽  
Domenic A. Santavicca
Keyword(s):  
Transfer Function ◽  
Heat Release ◽  
Velocity Fluctuation ◽  
Transfer Functions ◽  
Modulation Frequency ◽  
Shear Layers ◽  
Operating Conditions ◽  
Phase Curve ◽  
Destructive Interference ◽  
Resultant Velocity

The mixture-forced flame transfer function of a lean fully premixed single-nozzle research combustor operating on natural gas is determined experimentally at combustor pressures from 1 to 4 atm. Measurements are made over a range of inlet temperatures (100–300°C), mean velocities (25–35 m/s), and equivalence ratios (0.5–0.75). A rotating siren device, located upstream of the nozzle, is used to modulate the flow rate of the premixed fuel-air mixture. The amplitude and phase of the resultant velocity fluctuation are measured near the exit of the nozzle using the two-microphone method. The measured normalized velocity fluctuation serves as the input to the flame transfer function. In this study, the amplitude of the normalized velocity fluctuation is fixed at 5% and the modulation frequency is varied from 100 to 500 Hz. The output of the flame transfer function is the normalized global heat release fluctuation, which is measured using a photomultiplier tube and interference filter which captures the CH* chemiluminescence from the entire flame. In addition, two-dimensional CH* chemiluminescence images are taken for both forced and unforced flames. Forced flame images are phase-synchronized with the velocity fluctuation. The flame transfer functions for all of the operating conditions tested exhibit similar behavior. At low frequencies, the gain is initially greater than one, but then decreases as the frequency increases. After reaching a minimum, the gain increases with increasing frequency to a second peak and then again decreases. At certain operating conditions, the gain exhibits a second minimum. At frequencies corresponding to the minima in gain the phase curve exhibits inflection points. Regions of maximum and minimum gain are explained in terms of the constructive and destructive interference of vorticity fluctuations generated in the inner and outer shear layers. Phase-synchronized images are analyzed to isolate the fluctuating component of heat release. At frequencies where the gain is amplified, this analysis shows that the heat release fluctuations caused by the vorticity fluctuations generated in the inner and outer shear layers are in phase. While when the gain is at its minimum value, the heat release fluctuations are out of phase and therefore destructively interfere.

Analytic integration of contrast transfer functions

1988 ◽  
Vol 46 ◽  
pp. 822-823
Author(s):  
Peter Rez
Keyword(s):  
Wave Function ◽  
Transfer Function ◽  
Transfer Functions ◽  
Spherical Aberration ◽  
Continuous Distribution ◽  
Objective Lens ◽  
Direction Parallel ◽  
Scattering Angle ◽  
Analytic Integration ◽  
Image Position

In high resolution microscopy the image amplitude is given by the convolution of the specimen exit surface wave function and the microscope objective lens transfer function. This is usually done by multiplying the wave function and the transfer function in reciprocal space and integrating over the effective aperture. For very thin specimens the scattering can be represented by a weak phase object and the amplitude observed in the image plane is1where fe (Θ) is the electron scattering factor, r is a postition variable, Θ a scattering angle and x(Θ) the lens transfer function. x(Θ) is given by2where Cs is the objective lens spherical aberration coefficient, the wavelength, and f the defocus.We shall consider one dimensional scattering that might arise from a cross sectional specimen containing disordered planes of a heavy element stacked in a regular sequence among planes of lighter elements. In a direction parallel to the disordered planes there will be a continuous distribution of scattering angle.

A Comparison of Two Sub-structuring Techniques for Representing the Modal Properties of Tires

2001 ◽  
Vol 29 (1) ◽  
pp. 23-43 ◽  
Author(s):  
D. Tsihlas ◽  
T. Lacroix ◽  
B. Clayton
Keyword(s):  
Automobile Industry ◽  
Dynamic Models ◽  
Transfer Functions ◽  
Component Mode Synthesis ◽  
Numerical Techniques ◽  
The Past ◽  
Custom Made ◽  
Modal Behavior ◽  
Noise Vibration ◽  
Reduced Dynamic

Abstract Different numerical sub-structuring techniques for the representation of tire modal behavior have been developed in the past 20 years. By using these numerical techniques reduced dynamic models are obtained which can not only be used for internal studies but also be provided to the automobile industry and linked to reduced dynamic vehicle models in order to optimize the coupled vehicle-tire response for noise vibration and harshness purposes. Two techniques that have been developed in a custom-made finite element code are presented: 1) the component mode synthesis type models for which the wheel center interface is free and 2) the Craig and Bampton type models for which the wheel center interface is fixed. For both techniques the interface between the tire and the ground is fixed. The choice of fixed or free wheel center boundary condition is arbitrary. In this paper we will compare the formulation of these two numerical methods, and we will show the equivalency of both methods by showing the results obtained in terms of frequency and transfer functions. We will show that the two methods are equivalent in principle and the reduced dynamic models can be converted from one to the other. The advantages-disadvantages of each method will be discussed along with a comparison with experimentally obtained results.

Sign in / Sign up

Export Citation Format

Share Document