Numerical Computations with H(div)-Finite Elements for the Brinkman Problem

The H(div)-conforming approach for the Brinkman equation is studied numerically, verifying the theoretical a priori and a posteriori analysis in previous work of the authors. Furthermore, the results are extended to cover a non-constant permeability. A hybridization technique for the problem is presented, complete with a convergence analysis and numerical verification. Finally, the numerical convergence studies are complemented with numerical examples of applications to domain decomposition and adaptive mesh refinement.Comment: Minor clarifications, added references. Reordering of some figures. To appear in Computational Geosciences, final article available at http://www.springerlink.co

Numerical Study on Hydrogen–Gasoline Dual-Fuel Spark Ignition Engine

Data Availability Statement: This study did not report any data.Copyright © 2022 by the authors. Hydrogen, as a suitable and clean energy carrier, has been long considered a primary fuel or in combination with other conventional fuels such as gasoline and diesel. Since the density of hydrogen is very low, in port fuel-injection configuration, the engine’s volumetric efficiency reduces due to the replacement of hydrogen by intake air. Therefore, hydrogen direct in-cylinder injection (injection after the intake valve closes) can be a suitable solution for hydrogen utilization in spark ignition (SI) engines. In this study, the effects of hydrogen direct injection with different hydrogen energy shares (HES) on the performance and emissions characteristics of a gasoline port-injection SI engine are investigated based on reactive computational fluid dynamics. Three different injection timings of hydrogen together with five different HES are applied at low and full load on a hydrogen–gasoline dual-fuel SI engine. The results show that retarded hydrogen injection timing increases the concentration of hydrogen near the spark plug, resulting in areas with higher average temperatures, which led to NOX emission deterioration at −120 Crank angle degree After Top Dead Center (CAD aTDC) start of injection (SOI) compared to the other modes. At −120 CAD aTDC SOI for 50% HES, the amount of NOX was 26% higher than −140 CAD aTDC SOI. In the meanwhile, an advanced hydrogen injection timing formed a homogeneous mixture of hydrogen, which decreased the HC and soot concentration, so that −140 CAD aTDC SOI implied the lowest amount of HC and soot. Moreover, with the increase in the amount of HES, the concentrations of CO, CO2 and soot were reduced. Having the HES by 50% at −140 CAD aTDC SOI, the concentrations of particulate matter (PM), CO and CO2 were reduced by 96.3%, 90% and 46%, respectively. However, due to more complete combustion and an elevated combustion average temperature, the amount of NOX emission increased drastically.This research received no external funding

The multi-level Monte Carlo Finite Element Method for a stochastic Brinkman problem

We present the formulation and the numerical analysis of the Brinkman problem derived rigorously in [2, 3] with a random permeability tensor. The random permeability tensor is assumed to be a lognormal random field taking values in the symmetric matrices of size d×d , where d denotes the spatial dimension of the physical domain D . We prove that the solutions admit bounded moments of any finite order with respect to the random input's Gaussian measure. We present a Mixed Finite Element discretization in the physical domain D which is uniformly stable with respect to the realization of the lognormal permeability field. Based on the error analysis of this Mixed Finite Element Method (MFEM), we develop a Multi-Level Monte Carlo (MLMC) discretization of the stochastic Brinkman problem and prove that the MLMC-MFEM allows to estimate the statistical mean field with asymptotically the same accuracy versus work as the MFEM for a single instance of the stochastic Brinkman problem. The robustness of the MFEM implies in particular that the present analysis also covers the Darcy diffusion limit. Numerical experiments confirm the theoretical results

Physics-based dynamic simulation opportunities with digital twins

Abstract This paper aims to provide a viewpoint on the exploitation of physics-based dynamic simulation in product development and discrete manufacturing products. The dynamics models can be represented with computationally light models when the product and its dynamics are well known and thereby analyzing the performance e.g., with AI methods rapidly and accurately. The recent developments with methodologies, sensor development, measuring techniques and increased computing capacity are making the simulation world closer to reality and the ability for real-time operation simulations paralleled to the real system. This enables the exploitation of the digital twin paradigm at full capacity together with high-maturity digital twin models

Hydrogen and ammonia fuelled internal combustion engines, a pathway to carbon-neutral fuels future

Abstract Issues such as climate change and ever-increasing global warming have obliged governments and world authorities to comply with stringent regulations on the control of greenhouse gas(GHG) emissions in internal combustion engines (ICEs). Carbon dioxide (CO2), the most produced GHG, has been the major concern of climate change in recent years. To reduce carbon emissions, fuels with lower carbon content, such as alcohol fuels, or fuels with no carbon content, like hydrogen and ammonia, should be taken into consideration to be replaced by fossil fuels in internal combustion engines

Electric vehicles’ powertrain systems architectures design complexity

Abstract Strict emission regulations and energy scarcity have ushered in a new era of automotive technology. Utilizing electric power as a second source of energy or an alternative to fossil fuel energy has been the center of attention for decades. Implementing electric energy in vehicles’ powertrain systems requires new system architecture and rigorous methods for decision-making in a multi-disciplinary design procedure. Accordingly, the challenge is to define the design requirements and the economic feasibility of the final product

Proposing a hybrid BTMS using a novel structure of a microchannel cold plate and PCM

Abstract The battery thermal management system (BTMS) for lithium-ion batteries can provide proper operation conditions by implementing metal cold plates containing channels on both sides of the battery cell, making it a more effective cooling system. The efficient design of channels can improve thermal performance without any excessive energy consumption. In addition, utilizing phase change material (PCM) as a passive cooling system enhances BTMS performance, which led to a hybrid cooling system. In this study, a novel design of a microchannel distribution path where each microchannel branched into two channels 40 mm before the outlet port to increase thermal contact between the battery cell and microchannels is proposed. In addition, a hybrid cooling system integrated with PCM in the critical zone of the battery cell is designed. Numerical investigation was performed under a 5C discharge rate, three environmental conditions, and a specific range of inlet velocity (0.1 m/s to 1 m/s). Results revealed that a branched microchannel can effectively improve thermal contact between the battery cell and microchannel in a hot area of the battery cell around the outlet port of channels. The designed cooling system reduces the maximum temperature of the battery cell by 2.43 °C, while temperature difference reduces by 5.22 °C compared to the straight microchannel. Furthermore, adding PCM led to more uniform temperature distribution inside battery cell without extra energy consumption

Effect of natural gas direct injection (NGDI) on the performance and knock behavior of an SI engine

Abstract The unique properties of natural gas (NG), including high availability and lower cost compared with other fossil fuels, make it attractive in internal combustion engine (ICE) application. NG is composed mainly of methane and has greater knock resistance than gasoline, enabling higher compression ratios (CR). In contrast with the distinctive advantages, the NG fueled engines suffer from lower power and torque outputs. To address the subject, this study proposes an approach employing NG direct injection (NGDI) strategy (with higher volumetric efficiency unlike port injection), enabling a higher CR irrespective of knock limit. This work applies reactive computational fluid dynamics (CFD) to investigate spark ignited co-combustion of direct-injected NG with port-admitted gasoline. The results are validated against experimental data. In all simulated cases, the equivalence ratio (i.e., ∅ = 1) and the total input energy are kept constant. Engine performance is evaluated for three CRs (10.5, 11.5, and 12.5:1), five proportion of CNG (RCNG) and at part- and full-load conditions at an engine speed of 1500 rpm. Results indicated that while running RCNG = 100 % with a CR of 10.5:1, carbon monoxide (CO) and carbon dioxide (CO₂) emissions were decreased by 29.3 % and 23.5 % respectively, compared to RCNG = 0 %. The corresponding emission reduction at CR = 11.5:1 was 27.1 % and 24 %; at CR = 12.5:1 they were 29.6 % and 23.5 % respectively. At each CR, the knock intensity at full load fell significantly as the percentage of NG increased. At a CR of 12.5:1, ringing intensity (RI) at full load decreased by 88.6 % when using RCNG = 100 %, instead of RCNG = 0 %. Under the same conditions, RCNG = 25 % cut RI by 56 %

Micromechanical modeling of the role of Inclusions in high cycle fatigue damage Initiation and short crack growth

Abstract Multiscale microstructural and micromechanical modeling has arisen as a candidate to improve upon the classical methodologies for evaluation of fatigue crack initiation and propagation, both concerning improving our understanding of the fundamental material deformation and damage processes as well as in establishing more accurate design rules for engineering purposes. By exploiting methodologies of multiscale materials modeling, the vision is that engineering material properties can be directly computed based on microstructural scale analysis of single crystal plasticity and damage evolution. The models can then be further used to simulate the various dependencies affiliated with fatigue damage arising from material microstructure, such as the effects of stress triaxiality, compressive loading, and overall complex stress states. The overall goal of these efforts is the general decrease in empiricism, inaccuracy and affiliated uncertainty in the fatigue modeling and design chain. Current work utilizes novel crystal plasticity coupled damage model to evaluate the inclusion of steel microstructure interactions with the objective of better understanding and quantifying the role inclusions play concerning nucleation and growth of microstructure scale fatigue cracks. The approach is microstructural, i.e., material characteristics such as microstructural morphologies, individual phases, and inclusions are included explicitly in the numerical finite element models, and the subsequent behavior concerns single crystal deformation and initiation of fatigue. The analysis uses a micromechanical model where crystal plasticity and damage directly couple. A case study is carried out for primarily martensitic quenched and tempered steel for machine construction. The results suggest potential ways of exploiting multiscale materials modeling in the design of fatigue resistant microstructures, optimization of material solutions and improved fatigue design of products and components

Numerical study on hydrogen–gasoline dual-fuel spark ignition engine

Abstract Hydrogen, as a suitable and clean energy carrier, has been long considered a primary fuel or in combination with other conventional fuels such as gasoline and diesel. Since the density of hydrogen is very low, in port fuel-injection configuration, the engine’s volumetric efficiency reduces due to the replacement of hydrogen by intake air. Therefore, hydrogen direct in-cylinder injection (injection after the intake valve closes) can be a suitable solution for hydrogen utilization in spark ignition (SI) engines. In this study, the effects of hydrogen direct injection with different hydrogen energy shares (HES) on the performance and emissions characteristics of a gasoline port-injection SI engine are investigated based on reactive computational fluid dynamics. Three different injection timings of hydrogen together with five different HES are applied at low and full load on a hydrogen–gasoline dual-fuel SI engine. The results show that retarded hydrogen injection timing increases the concentration of hydrogen near the spark plug, resulting in areas with higher average temperatures, which led to NOX emission deterioration at −120 Crank angle degree After Top Dead Center (CAD aTDC) start of injection (SOI) compared to the other modes. At −120 CAD aTDC SOI for 50% HES, the amount of NOX was 26% higher than −140 CAD aTDC SOI. In the meanwhile, an advanced hydrogen injection timing formed a homogeneous mixture of hydrogen, which decreased the HC and soot concentration, so that −140 CAD aTDC SOI implied the lowest amount of HC and soot. Moreover, with the increase in the amount of HES, the concentrations of CO, CO₂ and soot were reduced. Having the HES by 50% at −140 CAD aTDC SOI, the concentrations of particulate matter (PM), CO and CO₂ were reduced by 96.3%, 90% and 46%, respectively. However, due to more complete combustion and an elevated combustion average temperature, the amount of NOX emission increased drastically