Erasmo Mancusi

Mathematical modeling and numerical simulation of heat and moisture transfer in a porous textile medium

The moisture accumulation within clothing is a serious problem for sportswear and clothing in cold climate. There are several experimental methods available to measure moisture build up in insulate materials. However, information on parameters such as temperature, relative humidity and vapor pressure can be obtained through simulation using a predictive mathematical model. The focus of this study is the development of a mathematical model to simulate heat and moisture transfer in a sample of fabric, coated to provide insulation, which is in contact with human skin on one side and with the external environment on the other. To numerically simulate the mathematical model, the finite volume method is used and a computational procedure for the solution of the model is designed. The simulation results are analyzed to verify whether they are consistent with the physical reality.

Chemical Looping Reforming: Impact on the Performances Due to Carbon Fouling on Catalyst

Abstract The paper presents a numerical analysis of an autothermal chemical looping reforming (CLR) process for hydrogen production. A packed–bed reactor has been simulated, which uses a Ni-based oxygen carrier. A one-dimensional pseudo-homogeneous model, validated with data available in literature is used to describe the overall process. The model accounts for different reactions taking place (methane and hydrogen oxidation, steam reforming, dry reforming, Ni and carbon oxidation by air), and simultaneously describes heat and mass transport. To take into account the catalyst fouling due to carbon deposition, CH 4 decomposition and carbon regasification by steam and CO 2 (Boudouard reaction) have been considered in the kinetic model, and a catalyst deactivation function has been introduced. By means of numerical simulations we highlight that carbon deposition gradually blocks catalyst active sites, leading to a progressive loss of catalytic activity. and we quantify the effects of catalyst poisoning on process performances.

Bifurcation Analysis of Perfectly Stirred Reactors with Large Reaction Mechanisms

An accurate characterization of new generation fuels gets through a definition of the ignition and extinction conditions. According to the terminology of non-linear analysis the ignition and extinction conditions (critical conditions) are defined as the turning-points on the S-curve and are uniquely identified by two saddle-node bifurcations. The exact location of the critical points that mark the ignition and extinction conditions, the onset of instabilities, as well as the dependence of the location on parameter values, cannot be obtained easily using temporal simulations tools. For a systematic and accurate analysis, the bifurcation analysis and the parametric continuation technique are the tools of choice. Even when the reactive mixture is described by a simple surrogate, but in conjunction with very complex and detailed chemical mechanism, the computation of the critical conditions become computationally very demanding. Usually, these difficulties are overcome by using reduced schemes and allowing simplifications in the model, like constant averaged thermodynamic properties. In this work we explore these issues. Particularly, we show that the adoption of a Broyden type corrector in the continuation algorithm leads to performances that made affordable the computations even with desktop computers. Consequently, we introduce a suitable algorithm to investigate ignition, extinction and linear stability of the air-fuel mixtures in a Perfectly Stirred Reactor (PSR). The algorithm is based on the well-known Keller pseudo-arclength continuation method in order to compute steady state solution curves. The solutions stability and then ignition and extinction states are identified by test functions based on the numerical eigenvalues of the Jacobian of the governing system of equations. The algorithm is implemented in the numerical computing environment Matlab coupled with the CANTERA Toolbox for managing of complex chemical kinetic mechanisms. The algorithm is thus easily applicable to chemical schemes available in the standard ChemKin format. To illustrate the capability of the resulting method, the characteristic S-Shaped curve, including non-stable branches, for several air-hydrocarbon mixtures have been computed.

Mapping resonance regions in loop networks with spatio-temporal symmetry

The nonlinear dynamics of a network of n cells where the connections are periodically switched in a loop/ring configuration is analyzed. Each cell is a nonlinear dynamical system which may behave as an oscillator. As system parameters are changed, the forcing frequency of the switching law interacts with natural frequencies of the system giving rise to resonance phenomena. The resonance regions corresponding to different rotation numbers (Arnold tongues) are mapped in two parameter space through the use of two-parameter continuation technique. Moreover, as the forcing induce spatio-temporal symmetries in the system, each tongue divides regions with different symmetries of the multiperiodic regimes.

Devil's staircases in loop networks with symmetry locking

In this work we analyze symmetry locking phenomena in loop networks with periodically switched connections. Exploiting the spatio-temporal symmetry properties of the system, we compute the rotation numbers of locked periodic regimes for which symmetry locking occurs. As a bifurcation parameter is varied, we compute the complete Devils staircase reporting the symmetry of the locked periodic regimes.