Artículos (Ingeniería de la Construcción y Proyectos de Ingeniería)

URI permanente para esta colecciónhttps://hdl.handle.net/11441/11337

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A Localized Version of the Dual-Primal Finite Element Tearing and Interconnecting Method for the Partitioned Analysis of Heterogeneous Structural Systems
(Wiley, 2026-01) González Pérez, José Ángel; Hoon Kang, Seung; Hyun Kim, Hyea; Joon Shin, Sang; Park, K. C.; Ingeniería de la Construcción y Proyectos de Ingeniería; Ministerio de Ciencia, Innovación y Universidades (MICIU). España; National Research Foundation of Korea
FETI-DP is a mature domain decomposition algorithm that has been successfully applied to different problems, demonstrating impressive performance. To be effective, the algorithm needs to be equipped with different technicalities that somewhat complicate its implementation. Examples include the treatment of constraint multiplicities at partition edges, the convergence enhancement using additional constraints, and the construction of an efficient preconditioner for heterogeneous problems. Nevertheless, we believe that it is possible to achieve the same performance as FETI-DP with a simpler implementation. This paper applies the method of localized Lagrange multipliers to the domain decomposition problem with a combination of dual and primal constraints, formulating a localized variant of FETI-DP named AFETI-DP. Although the convergence of AFETI-DP is equivalent to the basic FETI-DP algorithm, its implementation is simpler, eliminating the constraint multiplicity problem at the partition edges. Another benefit is that the localized multipliers can be scaled independently, an advantage for heterogeneous cases where FETI-DP needs to construct special jump operators for preconditioning. Finally, it is also demonstrated how to include additional constraints with AFETI-DPc by using a classical deflation and balancing approach with projection. For this task, the subdomain rigid body modes are capitalized in a completely uncoupled manner to attain convergence properties equivalent to the most modern FETI-DP methods.
A Green–Taylor element method for the solution of Helmholtz problems with variable wavenumber
(Elsevier, 2026-05) Cerrato Casado, Antonio; González Pérez, José Ángel; Galán Fernández, José Manuel; Ingeniería de la Construcción y Proyectos de Ingeniería; Ministerio de Ciencia e Innovación (MICIN). España; Ministerio de Ciencia, Innovación y Universidades (MICIU). España; Agencia Estatal de Investigación. España; European Commission (EC). Fondo Europeo de Desarrollo Regional (FEDER); European Union (UE)
Boundary element methods are particularly attractive for the analysis of wave propagation problems because of their reduced dimensionality and accurate representation of radiation conditions. However, their application to Helmholtz problems with spatially varying wavenumber is limited by the lack of fundamental solutions in closed form and the complexity associated with the computation of additional domain integrals. In this work, we propose a domain partitioning method combined with a boundary integral formulation applied locally on each element using the Green–Taylor Element Method (GTEM). This approach extends the original one-dimensional formulation of GTEM (Cerrato-Casado and González, 2026) to the two-dimensional Helmholtz equation with variable wavenumber. The method applies Green’s third identity locally on subdomains, accounting for inhomogeneities at the element level, and approximates the interior fields through Taylor series expansions constructed from boundary quantities. This local treatment maintains the boundary character of the formulation by substituting global domain integrations with simpler element integrations. Numerical results demonstrate that the proposed GTEM approach achieves higher accuracy with fewer elements per wavelength compared to finite element and finite difference methods of the same order. Moreover, the method exhibits a low sensitivity to mesh distortion, outperforming classical approaches on irregular meshes commonly used in practical engineering applications.
Solving FEM models without assembly: Its promise and challenge
(Elsevier, 2026-03) Park, K.C.; González Pérez, José Ángel; Shin, SangJoon; Kang, Seung-Hoon; Hwang, M.H.; Kim, J.G.; Baqir, M.F.; Han, J.H.; Hagos, R.W.; Felippa, C.A.; Ingeniería de la Construcción y Proyectos de Ingeniería; National Research Foundation of Korea; Institute of Civil Military Technology Cooperation (Korea); Ministerio de Ciencia, Innovación y Universidades (MICIU). España; Agencia Estatal de Investigación. España; European Commission (EC). Fondo Europeo de Desarrollo Regional (FEDER)
The present paper is a compendium of recent advances by seven research teams who have applied the PartStiff and PartFlex methods in solving seven distinctly different problems. Each of the research teams exploited the key feature of the PartStiff and PartFlex methods: partitioned (unassembled) FEM models without Lagrange multipliers. The unassembled PartStiff equation is given by 𝐌̈𝐝 = 𝒫𝑑 (𝐟 − 𝐊𝐝) where (𝐌, 𝐊, 𝐟,̈ 𝐝, 𝐝, 𝒫𝑑 ) are the partitioned block diagonal mass and block diagonal stiffness matrices and the applied force, acceleration and displacement vectors, and the projection operator 𝒫𝑑 which accomplishes the necessary coupling among the partitions. The paper presents applications of both the PartStiff and PartFlex methods: high-fidelity parallel solvers for heterogeneous problems; an element-by-element implicit-explicit transient algo- rithm; reduced-order modeling (ROM) with a practical model-order reduction criterion; component mode synthesis guided by a rational mode selection guide, identification of damage locations and damage levels via experimentally identified models and/or data-driven digital-twin models; and, topology optimization, among others.
Expressions to predict the rotation capacity of austenitic stainless steel members under constant axial load and cyclic bending
(Elsevier, 2025-12) Bustamante Mora, Boris; Arrayago, Itsaso; González de León, Isabel; Real, Esther; Ingeniería de la Construcción y Proyectos de Ingeniería; Ministerio de Ciencia, Innovación y Universidades (MICIU). España
Stainless steel is a structural material with increasing demand for its aesthetic and mechanical properties, as well as its potential in seismic design due to its ductility and strain hardening. However, research on the behaviour of stainless steel under seismic loads is scarce, especially when focused on the global response of structures. One of the key parameters governing the seismic response of systems is the rotation capacity of structural members and compacts, for which recent investigations have proposed predicting expressions under cyclic bending. However, in more complex loading cases such as members subjected to constant axial loads (i.e., gravity loads) and cyclic bending (i.e., seismic actions), the existing expressions for predicting the rotation capacity are very complex or only applicable to a limited range of cases. In this context, the present investigation proposes simple analytical expressions to predict the full moment-rotation diagrams of austenitic stainless steel hollow section elements under combined axial loading and cyclic bending. The proposal is based on an extensive numerical parametric study considering a range of elements under different local slendernesses and several levels of axial loading. The rotation capacities and corresponding bending moment resistances are related to the key affecting parameters, such as the axial load, section stiffness and local slenderness, from which the key features of the full moment-rotation diagrams can be obtained for the characterisation of plastic hinges, allowing a more efficient seismic design of stainless steel structures.
Enhanced experimental assessment of ultra-low temperature auto-cascade refrigeration systems via data reconciliation
(Elsevier, 2026-03) Vélez Godiño, José Antonio; Expósito Carrillo, José Antonio; Sánchez de la Flor, Francisco José; Ingeniería de la Construcción y Proyectos de Ingeniería
Interest in ultra-low temperature applications has grown rapidly following the emergence of mRNA-based COVID-19 vaccines. The auto-cascade refrigeration cycle has become the most widely adopted solution for such applications, prompting numerous studies aimed at optimizing refrigerant mixtures and improving cycle efficiency through strategies such as ejector integration. However, most experimental research has focused on achieving minimum temperatures or analysing the pull-down process rather than performing a complete thermodynamic characterization of the cycle. Only a few recent studies have used Coriolis mass flow meters to fully determine circulating compositions and key performance metrics, such as cooling capacity and COP. Nonetheless, such instrumentation is rarely available in commercial systems. To address this limitation, the present work proposes, as its main novelty, the use of Data Reconciliation and Gross Error Detection methodologies to characterize the refrigeration cycle using only non-invasive measurements of pressure, temperature, and power consumption. This methodology identifies and corrects measurement errors in the experimental setup, resulting in a consistent dataset and allowing the determination of the circulating composition, cooling capacity, and COP with an average deviation below 5 % compared to raw data. A sensor sensitivity analysis revealed that temperatures at the evaporator inlet and outlet are the most critical for accurate COP estimation, as measurement errors of 0.5 K at these points can cause deviations of up to 5 %. The proposed approach proved to be a powerful tool for the analysis and future development of ultra-low temperature refrigeration cycles, especially those using zeotropic refrigerant mixtures.
A new design formula to estimate wave transmission on cubipod homogeneous low-crested structures
(Elsevier, 2025-12) Díaz Carrasco, Pilar; Mares Nasarre, Patricia; Molines, Jorge; Gómez Martín, M. Esther; Medina, Josep R.; Ingeniería de la Construcción y Proyectos de Ingeniería; Ministerio de Ciencia e Innovación (MICIN). España; European Commission (EC). Fondo Europeo de Desarrollo Regional (FEDER)
This study presents a new explicit empirical formula to estimate wave transmission on Cubipod Homogeneous Low-Crested Structures (HLCS) under depth-limited breaking wave conditions. The formula was derived using Artificial Neural Networks (ANN) to identify and quantify the influence of nineteen candidate explanatory variables on the squared wave transmission coefficient, K2T. A total of 210 two-dimensional physical model tests conducted at the Universitat Politècnica de València (Spain) were used to calibrate the formula. The dimensionless crest freeboard using the nominal diameter (Rc/Dn50) and the dimensionless incident wave height at the structure toe using the water depth (Hm0,I/hs) were identified as the most relevant explanatory variables. A new two-variable formulation with 3 fitting-parameters was found to estimate the proportion of transmitted energy, K2T, with a coefficient of determination R2 = 0.89. The proposed formula was also applied to an external dataset of experimental tests on Cubipod HLCS previously reported in the literature. The results demonstrated a significantly better agreement than existing empirical formulas confirming the robustness and applicability of the new formula. The proposed formula is a reliable and easy-to-apply new tool for the preliminary design of emerged and submerged undamaged HLCS in depth-limited breaking wave conditions. The new explicit formula is particularly suited for low-crested structures aimed at combining coastal protection and ecosystem enhancement, such as artificial reefs in coral environments.
Experimental minimization of pilot diesel injection for stable hydrogen combustion in compression ignition engines
(Elsevier, 2025) Vélez Godiño, José Antonio; Serrano Reyes, Javier; Tagua Navarrete, Miguel Ángel; Jiménez-Espadafor Aguilar, Francisco José; Ingeniería de la Construcción y Proyectos de Ingeniería; Ingeniería Energética
Hydrogen has emerged as a promising alternative fuel due to its zero-carbon combustion. However, its use in compression ignition engines presents challenges, including abnormal combustion phenomena, which limit the maximum attainable load, and increased nitrogen oxides emissions. This study explores the use of hydrogen as the primary fuel in a compression ignition engine, implementing a novel strategy where diesel is employed solely as a minimized pilot ignition source. This approach departs from conventional dual-fuel combustion methods by significantly reducing diesel usage while maintaining stable combustion. The main novelties consist of determining the lowest feasible diesel quantity required for stable combustion and demonstrating the improvement in performance resulting from reduced diesel pilot injection. The experimental investigation was conducted on a modified turbocharged compression ignition engine, incorporating water injection as a strategy to mitigate abnormal combustion and nitrogen oxides formation. The study analyses the effects of key operating parameters, including start of injection timing, compression ratio, and engine speed, on combustion stability and performance. The results highlight the critical role of pilot diesel injection in achieving stable combustion while minimizing carbon dioxide emissions. Furthermore, maximizing hydrogen energy share leads to enhanced thermal efficiency without compromising engine operability. Additionally, water injection effectively reduces nitrogen oxides emissions and delays the onset of knock combustion, despite its slight negative impact on efficiency. Compared to other operational strategies, the approach proposed here improves thermal efficiency (by 1–3 %), reduces knock tendency (peak pressure rise rate < 5 bar/CAD), and lowers nitrogen oxides emissions (by 30–50 %).
Joint data reconciliation and artificial neural network based modelling: application to a cogeneration power plant
(Elsevier, 2024-01) Vélez Godiño, José Antonio; Jiménez-Espadafor Aguilar, Francisco José; Ingeniería de la Construcción y Proyectos de Ingeniería; Ingeniería Energética; Junta de Andalucía; TEP137: Máquinas y Motores Térmicos; TIC152: Ingeniería de la Construcción y Proyectos de Ingeniería
This contribution represents a practical application of predictive thermal modelling of an existing cogeneration plant. The analysed cogeneration plant consists of a gas turbine coupled to a heat recovery steam generator, which produces two streams of superheated steam (65 bar and 10 bar) and a thermal oil stream at 350 °C. The proposed model was based on an artificial neural network and was trained using real operational data. However, although data acquisition systems currently used in power generation plants allow for the recording of multiple measurements using small sampling intervals, this does not guarantee a satisfactory analysis of operational data. Therefore, the potential of artificial neural networks can result in incorrect or imprecise results if the calibration of the network is performed with inconsistent or highly uncertain datasets. The novelty of this work consisted on the application of data reconciliation to the real dataset before the model training, in order to minimize the typical uncertainty associated with plant instrumentation measurements. The results obtained demonstrated the advantage of training the network with reconciled data and that modelling error is reduced for all analysed outputs when the model is based on artificial neural networks instead of polynomial models.
A high-order accurate Green-Taylor element method for the numerical solution of Helmholtz’s equation with variable wavenumber
(Elsevier, 2026-02) Cerrato Casado, Antonio; González Pérez, José Ángel; Ingeniería de la Construcción y Proyectos de Ingeniería; Ministerio de Ciencia e Innovación (MICIN). España; European Commission (EC). Fondo Europeo de Desarrollo Regional (FEDER); TIC152: Ingeniería de la Construcción y Proyectos de Ingeniería
In this work, we propose a novel Green-Taylor element method (GTEM) for solving the Helmholtz equation with variable wavenumber. The method combines a boundary integral form of the problem, derived from Green’s second theorem, with a discrete element approach to incorporate the effect of domain heterogeneity. A key feature of GTEM is the treatment of the domain integrals using Taylor series expansions from the element boundaries to approximate the interior variation of the solution, thus avoiding internal variables and enabling high-order approximations without the need of additional unknowns. The method is here particularized to the one-dimensional case, studying its accuracy and convergence properties. Different tests and practical applications of the Helmholtz equation for heterogeneous media are used to demonstrate the superior accuracy of GTEM compared to other classical numerical techniques such as hp-finite elements, spectral elements, or isogeometric analysis with b-splines.
Clean and zero-emission urban buses: Compliance with EU regulations and fleet transition in Seville
(Elsevier, 2025-09-30) Tagua Navarrete, Miguel Ángel; Serrano Reyes, Javier; Vélez Godiño, José Antonio; Jiménez-Espadafor Aguilar, Francisco José; Ingeniería Energética; Ingeniería de la Construcción y Proyectos de Ingeniería
The EU public transport sector is dominated by diesel and natural gas buses, but fleet structures are rapidly changing. EU climate laws drive two strategies: one for bus manufacturers and another for public transport operators (PTO), with different timelines. PTOs must progressively replace fleets with clean and zero-emission buses. This paper develops bus replacement strategies aligned with EU standards, focusing on cost minimization and CO 2 emission reduction. Three propulsion technologies (diesel, compressed natural gas, and electric) and two bus types (regular and articulated) are analyzed. The strategies consider acquisition, operational, and service costs, along with CO 2 emissions. The proposed approach, applied over a 10-year period, uses real-word data from Seville (Spain) PTO to meet EU standards for 2025–2035. Operational data allow precise energy demand estimation, considering propulsion, climatization air compressor, and auxiliaries. CO 2 culations show that CNG buses emit 24 % more CO 2 emissions calper km than diesel buses. Optimization results indicate that a CO 2 minimization strategy reduces emissions by 16.3 %, with only a 6.7 % cost increase compared to the minimal-cost strategy.
A new method to measure damage progression in Homogeneous Low-Crested Structures with a low-cost 3D depth-sensor
(Elsevier, 2025-04-15) Muñoz-Palao, Sergio; Díaz Carrasco, Pilar; Molines, Jorge; Gómez-Martín, M. Esther; Medina, Josep R.; Ingeniería de la Construcción y Proyectos de Ingeniería; Ministerio de Ciencia e Innovación (MICIN). España; European Union (UE)
Mechanical profilers are commonly used to measure damage to rubble mound breakwaters in small-scale physical tests. This study developed a non-intrusive methodology using low-cost 3D depth-sensors to measure damage progression in Homogeneous Low-Crested Structures (HLCS) with and without water in the wave flume. Although light refraction causes distortion in the presence of water, distorted scans are corrected with this new method using a Neural Network (NN) model. The new methodology is adequate to obtain undistorted profiles of emerged or submerged breakwaters and may be described in two steps: (1) a digital profiler algorithm, to describe the breakwater models in series of profiles in order to measure damage, and (2) a trained NN model, to correct the distortions caused by light refraction for the scans taken with water in the wave flume. The NN model to correct profiles requires two sets of scans, one in empty conditions and the other in submerged conditions; the two scans (dry-wet) can be easily obtained without disturbing the usual test programs. This is done by taking the scans at the beginning (dry and wet) and at the end (wet and dry) of each test series. By comparing profiles, the breakwater damage can be analysed after obtaining the series of undistorted profiles from the trained NN model and the distorted scans. To validate the method, a series of small-scale physical tests with Cubipod HLCS were carried out from no damage to severe damage, and then the estimations given by the trained NN models were compared with blind observations, taken from additional pairs of dry and wet scans. The good agreement between the observations and the estimations (R2 > 0.985, r > 0.993) showed that low-cost 3D depth-sensors may be used as non-intrusive methods for breakwater profiling, even when scanning is done with water in the wave flume or basin.
Microwave Drying Method before Sieving to Obtain Accuracy of Sand Size Parameters
(Multidisciplinary Digital Publishing Institute (MDPI), 2024-03) López García, Patricia; Muñoz Pérez, Juan José; Contreras de Villar, Antonio; Contreras de Villar, Francisco; Romero Cózar, Jeanette; Díaz Carrasco, Pilar; Jigena Antelo, Bismarck; Ingeniería de la Construcción y Proyectos de Ingeniería; Junta de Andalucía; Unión Europea
The purpose of this study is to determine the differences between the size parameter findings, comparing the results of a muffle during a 12-h sand-drying process with those of a microwave, because the effectiveness of sand drying with a microwave has not previously been studied. To achieve the best outcomes and assess any inaccuracies, a technique was established. Several power levels and durations were used in the tests. Furthermore, as the median particle size (D50) affects the porosity of sand, samples from three beaches in the south of Spain with varying sand sizes were used in this study. When drying for at least 5 min, the error findings for D50 are less than 3.5%, which is perfectly acceptable for beach nourishment purposes. Regarding power, 462 watts was the optimal power; a lower power, approximately 300 watts, did not completely dry the material, even after nearly 15 min. Furthermore, errors in the sorting (σ) parameter were negligible. It is essential to implement the following recommendations in microwave drying methods: the use of a light and wide container for the sand, interruptions during drying, and a minimum duration of 5 min.
Dipolar Brush Polymers: A Numerical Study of the Force Exerted onto a Penetrating Colloidal Particle Under an External Field
(MDPI, 2025-02) Fuster-Aparisi, A.; Cerrato Casado, Antonio; Batle, Josep; Cerdà, Joan Josep; Ingeniería de la Construcción y Proyectos de Ingeniería; Ministerio de Economía y Competitividad (MINECO). España; TIC152: Ingeniería de la Construcción y Proyectos de Ingeniería
Langevin Dynamics numerical simulations have been used to compute the force profiles that dipolar polymer brushes exert onto a penetrating colloidal particle. It has been observed that force profiles are strongly influenced by externally applied fields: at large distances from the grafting surface, a force barrier appears, and at shorter distances a region with lower repulsive forces develops. Furthermore, with the right combination of polymer grafting density, polymer chain length and strength of the external field, it is possible to observe in this intermediate region both the existence of net attractive forces onto the penetrating particle and the emergence of a stationary point. The existence of these regions of low repulsive or net attractive forces inside the dipolar brushes, as well as their dependence on the different parameters of the system can be qualitatively reasoned in terms of a competition between steric repulsion forces and Kelvin forces arising from the dipolar mismatch between different regions of the system. The possibility to tune force profile features such as force barriers and stationary points via an external field paves the way for many potential surface–particle-related applications.
A domain decomposition method employing displacement-only partitioned equations for quasi-static structural analysis
(Elsevier, 2024-11-01) Kang, Seung-Hoon; Park, K.C.; González Pérez, José Ángel; Shin, SangJoon; Ingeniería de la Construcción y Proyectos de Ingeniería; Korean government (MSIT); TIC152: Ingeniería de la Construcción
The present study reports a family of iterative domain decomposition method for the static structural analysis, labeled as AFETI-DO and its variants (AFETI-DOc and AFETI-DOci), all of which employ a recently developed Displacement-Only (DO) partitioned formulation (Park et al., 2023). The DO partitioned equation (P𝑑(𝐟 − 𝐊𝐝) = 0) consists of the applied force 𝐟, the block-diagonal stiffness matrix (𝐊) for each partition, the coupling projection operator (P𝑑), and the unknown partitioned displacements (𝐝). Numerical experiments with the AFETI-DO and its two variants demonstrate that, while their performance is comparable to existing iterative solution algorithms for homogeneous problems, for highly heterogeneous two and threedimensional problems the proposed methods yield an accurate convergence threshold compared with the FETI-DP method (Farhat et al., 2001). For fourth-order elasticity problems (i.e., thin plates and shells), the present methods offer a comparable accuracy and computational effort required with the FETI-DP method. In addition, while not extensive, the numerical performance of the proposed AFETI-DO method and its variants appear to exhibit scalability and improved accuracy, provided the preconditioners are paired with the commensurate heterogeneities.
Failure analysis of an overhead valve train system in urban buses
(Elsevier, 2019-02) Vélez Godiño, José Antonio; Torres-García, Miguel; Jiménez-Espadafor Aguilar, Francisco José; Palomo Guerrero, Daniel; Ingeniería de la Construcción y Proyectos de Ingeniería; Ingeniería Energética
This work is focused on the study of the failures identified in the valve train system of two different types of engines, one diesel and one fed by compressed natural gas, both pertaining to a fleet of urban buses. The studied failure has been reported in >20 different units, the affected elements being both the cams (material removal at the cam nose) and the tappets (hard plate removal and strong tappet core deformation) and requiring the vehicles to be out of service until being repaired. In order to determine the root cause of the failure, the performed analyses have covered the lube oil characteristics, the kinematic chain status, highlighting the review of the camshaft modal response and the behaviour of the valves springs, and, finally, the verification of the selection regarding both the material and heat treatment of the camshaft.
Innovative power train configurations for aircraft auxiliary power units focused on reducing carbon footprint
(Elsevier Masson, 2020-11) Jiménez-Espadafor Aguilar, Francisco José; Vélez Godiño, José Antonio; Ingeniería de la Construcción y Proyectos de Ingeniería; Ingeniería Energética; Ministerio de Economía y Competitividad (MINECO). España
Auxiliary power units constitute a non-negligible source of pollution not only in flight conditions but also at airports and their surrounding areas. This work compiles a technical feasibility assessment focused on the analysis of innovative alternatives to the traditional aircraft gas turbine based auxiliary power unit arrangement. The proposed innovations involve both new power train configurations and the use of different fuels, with the purpose of reducing both the primary energy consumption and the environmental impact of these systems. The core innovation proposed here consists in the use of a supercharged rotary engine as an alternative configuration to traditional auxiliary power units in aircraft. The rotary engine can achieve higher thermal efficiencies than gas turbines, which corresponds to a lower specific fuel consumption and, thus, a lower carbon footprint. Additionally, the proposed alternatives will involve hybrid configurations, providing thermal energy generation with electrical storage devices. Finally, the assessed arrangements will be based on the “more electric aircraft” concept, which implies a simplification of the aircraft non-propulsive power system design and allows the addition of batteries to the generating unit. In order to perform this assessment, different thermal models and simulations have been developed, allowing the quantification of the improvements related to the alternative proposed configuration.
Experimental analysis of late direct injection combustion mode in a compression-ignition engine fuelled with biodiesel/diesel blends
(Elsevier, 2022-01-15) Vélez Godiño, José Antonio; Torres-García, Miguel; Jiménez-Espadafor Aguilar, Francisco José; Ingeniería de la Construcción y Proyectos de Ingeniería; Ingeniería Energética; Junta de Andalucía
A compression ignition reciprocating internal combustion engine has been modified to allow operation with late direct injection of rapeseed biodiesel fuel blends. The purpose of these modifications is to reduce both the engine's carbon footprint and emission of nitrogen oxides and soot, without decreasing performance or using expensive emission post-treatment systems. The experimental part of this work is based on the measurement of the main pollutants being emitted and the analysis of the combustion process, which is accomplished by the study of the heat release rate curve. This curve is derived from the experimental chamber pressure data, in combination with a zero-dimensional thermodynamic model assuming a perfect mixing reactor with temporal variation in volume and chemical composition, temperature-dependent properties and heat losses. The analysis of the experimental results allows deepening the knowledge of the combustion process in a compression ignition engine with late direct injection using different biodiesel blends. There is a significant reduction (>50%) of emissions of nitrogen oxides in comparison with the original configuration. This allows considering the modified configuration as an advanced combustion mode, intermediate between conventional compression ignition engines and homogeneous charge compression ignition combustion mode.
Simulation of HCCI combustion in air-cooled off-road engines fuelled with diesel and biodiesel
(Elsevier, 2018-08) Vélez Godiño, José Antonio; Jiménez-Espadafor Aguilar, Francisco José; Torres-García, Miguel; Ingeniería de la Construcción y Proyectos de Ingeniería; Ingeniería Energética; Ministerio de Economía y Competitividad (MINECO). España
The present work describes the elaboration of a predictive tool consisting on a phenomenological multi-zone model, applicable to the simulation of HCCI combustion of both diesel and biodiesel fuels. The mentioned predictive tool is created with the aim to be applied in the future to perform engine characterization during both pre-design and post-design stages. The methodology applied to obtain the proposed predictive model is based on the generation of an analytical mechanism that, given a set of regression variables representing the engine operative conditions, provides the user with the optimal figures for the scaling coefficients needed to particularize both the ignition delay and the heat release rate functional laws, which rule the combustion development in the proposed multi-zone model for HCCI engines. The validation of the proposed predictive multi-zone model consists on the comparison between chamber pressure curve derived from the simulations and experimental data based on a DEUTZ FL1 906 unit modified in order to allow HCCI combustion operation mode using diesel EN590 and rapeseed biodiesel. Finally, evidences of the capabilities of the proposed model to be used as a predictive tool applicable to the analysis of off-road engines under HCCI conditions are provided, consisting in the characterization and optimization of the operational maps related to both Brake Specific Fuel Consumption and NOx emissions.
Explicit multistep time integration for discontinuous elastic stress wave propagation in heterogeneous solids
(2019-05) Cho, Sang S.; Kolman, Radek; González Pérez, José Ángel; Park, K.C.; Ingeniería de la Construcción y Proyectos de Ingeniería; TIC152: Ingeniería de la Construcción y Proyectos de Ingeniería
A multistep explicit time integration algorithm is presented for tracking the propagation of discontinuous stress waves in heterogeneous solids whose subdomain-to-subdomain critical time step ratios range from tens to thousands. The present multistep algorithm offers efficient and accurate computations for tracking discontinuous waves propagating through such heterogeneous solids. The present algorithm, first, employs the partitioned formulation for representing each subdomain, whose interface compatibility is enforced via the method of the localized Lagrange multipliers. Second, for each subdomain, the governing equations of motion are decomposed into the extensional and shear components so that tracking of waves of different propagation speeds is treated with different critical step sizes to significantly reduce the computational dispersion errors. Stability and accuracy analysis of the present multistep time integration is performed with one-dimensional heterogeneous bar. Analyses of the present algorithm are also demonstrated as applied to the stress wave propagation in one-dimensional heterogeneous bar and in heterogeneous plain strain problems.
Inverse mass matrix for isogeometric explicit transient analysis via the method of localized Lagrange multipliers
(John Wiley & Sons, 2019-03) González Pérez, José Ángel; Kopačka, J.; Kolman, Radek; Cho, Sang S.; Park, K.C.; Ingeniería de la Construcción y Proyectos de Ingeniería; Czech Science Foundation; Korea Foundation of Nuclear Safety; TIC152: Ingeniería de la Construcción y Proyectos de Ingeniería
A variational framework is employed to generate inverse mass matrices for isogeometric analysis (IGA). As different dual bases impact not only accuracy but also computational overhead, several dual bases are extensively investigated. Specifically, locally discontinuous biorthogonal basis functions are evaluated in detail for B-splines of high continuity and Bézier elements with a standard C0 continuous finite element structure. The boundary conditions are enforced by the method of localized Lagrangian multipliers after generating the inverse mass matrix for completely free body. Thus, unlike inverse mass matrix methods without employing the method of Lagrange multipliers, no modifications in the reciprocal basis functions are needed to account for the boundary conditions. Hence, the present method does not require internal modifications of existing IGA software structures. Numerical examples show that globally continuous dual basis functions yield better accuracy than locally discontinuous biorthogonal functions, but with much higher computational overhead. Locally discontinuous dual basis functions are found to be an economical alternative to lumped mass matrices when combined with mass parameterization. The resulting inverse mass matrices are tested in several vibration problems and applied to explicit transient analysis of structures

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