In this work, the Global Energy Balance (GEB) of a 1.6 L compression ignition engine is analyzed during WLTC using a combination of experimental measurements and simulations, by means of a Virtual Engine. The energy split considers all the relevant energy terms at two starting temperatures (20°C and 7°C) and two altitudes (0 and 1000 m). It is shown that reducing ambient temperature from 20°C to −7°C decreases brake efficiency by 1% and increases fuel consumption by 4%, mainly because of the higher friction due to the higher oil viscosity, while the effect of increasing altitude 1000 m decreases brake efficiency by 0.8% and increases fuel consumption by 2.5% in the WLTC mainly due to the change in pumping. In addition, GEB shows that ambient temperature is affecting exhaust enthalpy by 4.5%, heat rejection to coolant by 2%, and heat accumulated in the block by 2.5%, while altitude does not show any remarkable variations other than pumping and break power.

Background: Periodontitis has been associated to systemic diseases and this association could be due to an increase in circulating inflammatory and oxidative stress biomarkers in the periodontal disease. This study aimed to evaluate the relationship between inflammatory and pro-oxidant markers according to different stages of periodontitis. Methods: This cross-sectional study included 70 subjects who were divided into three groups according to periodontitis stage: stage II (n = 22), stage III (n = 30), and stage IV (n = 18). We evaluated periodontal parameters and levels of high-sensitivity C-reactive protein (hsCRP), fibrinogen, and malondialdehyde (MDA) in serum, and 8-hydroxy-2′-deoxyguanosine (8-OHdG) in urine. Results: Serum hsCRP and fibrinogen levels were associated with periodontitis severity, which were higher in stage IV than in stages III and II of periodontitis (p = 0.003 and p = 0.025, respectively). We observed a slight yet insignificant increase in MDA levels related to periodontitis severity. Probing depth and clinical attachment loss were associated with serum fibrinogen and hsCRP levels. However, there were no significant associations between periodontal variables and MDA and 8-OHdG levels. Conclusion: Our data support an association between periodontitis and systemic inflammation, which increases with periodontal disease severity. This indicates the importance of the early diagnosis and treatment of periodontal disease to avoid the development or worsening of systemic inflammatory diseases.

Background: The aim of this study is to determine the changes in serum levels of malondialdehyde, 8-hydroxy-2’-deoxyguanosine, hsCRP and fibrinogen as indicators of oxidative stress and inflammatory markers, in response to non-surgical periodontal treatment. Case description: The patient, a 51-year-old male diagnosed with periodontitis was taken so as to be studied with a therapeutic objective, which should allow after three months the time of diagnosis and after non-surgical treatment. Topical doxycycline was used as adjunctive medication. Conclusion: A significant reduction in both serum levels of pro-inflammatory markers and oxidative stress indicators is observed after periodontal treatment.

Encouraged by the diversity of n-dodecane chemical mechanisms currently available, this investigation focuses on analysing the impact of using different fuel oxidation schemes on the diesel-like Engine Combustion Network (ECN) Spray A flame structure, simulated by means of an Unsteady Flamelet Progress Variable (UFPV) combustion model. The present research discusses systematically the characteristics of four n-dodecane chemical mechanisms in perfectly stirred reactors and counterflow laminar diffusion flames (flamelets) before the final evaluation in turbulent reacting sprays in order to describe the effects of adding different physical levels of complexity to the ignition of the mixtures. In addition, this analysis is complemented with the description of the effect of the boundary conditions on the flame structure. Results evidence the extreme importance of the low temperature chemistry including the period for which the cool flame extends. The different prediction of this stage between mechanisms leads to noticeable different laminar flame structures which in turn produce substantially distinct turbulent flames, especially in the vicinity of the lift-off length (LOL) in terms of reactivity and positioning in the Z-T map. Finally, simulations confirm the strong effect of the boundary conditions, especially for the ambient temperature, on the ignitable mixtures which directly impacts on the soot precursors formation. (C) 2019 The Combustion Institute. Published by Elsevier Inc. All rights reserved.

The increasingly stringent internal combustion engines emissions regulations, has led to the extended use of after-treatment systems, giving progressively more importance to the engine efficiency optimization. In this framework, the combined modelling and experimental methodologies to perform and analyse the energy balance are key to evaluate the potential of different engine strategies aimed at the consumption optimization and the identification of the improvement paths. This work has been divided into two parts, dealing separately with the development and application of a Global Energy Balance tool. This article corresponds to the first part, which comprises the description of the models required to perform a detailed energy balance and the calibration methodologies followed to achieve accurate energy terms estimation. The models are calibrated based on experimental information, thus, a thermodynamic analysis aimed at defining comparable quantities between experimental and modelled terms is performed. The uncertainty analysis of the tool shows a deviation in the determination of the heat transfer to the coolant and the oil of about ±2%, and in terms of fuel energy about ±1%.

The increasingly restrictive legislation on pollutant emissions is involving new homologation procedures driven to be representative of real driving emissions.This context demands an update of the modelling tools leading to an accurate assessment of the engine and aftertreatment systems performance at the same time as these complex systems are understood as a single element.In addition, virtual engine models must retain the accuracy while reducing the computational effort to get closer to real-time computation.It makes them useful for pre-design and calibration but also potentially applicable to on-board diagnostics purposes.This paper responds to these requirements presenting a lumped modelling approach for the simulation of aftertreament systems.The basic principles of operation of flow-through and wall-flow monoliths are covered leading the focus to the modelling of gaseous emissions conversion efficiency and particulate matter abatement, i.e. filtration and regeneration processes.The model concept is completed with the solution of pressure drop and heat transfer processes.The lumped approach hypotheses and the solution of the governing equations for every submodel are detailed.While inertial pressure drop contributions are computed from the characteristic pressure drop coefficient, the porous medium effects in wall-flow monoliths are considered separately.Heat transfer sub-model applies a nodal approach to account for heat exchange and thermal inertia of the monolith substrate and the external canning.In wall-flow monoliths, the filtration and porous media properties are computed as a function of soot load applying a spherical packed bed approach.The soot oxidation mechanism including adsorption reactant phase is presented.Concerning gaseous emissions, the general scheme to solve the chemical species transport in the bulk gas and washcoat regions is also described.In particular, it is finally applied to the modelling of CO and HC abatement in a DOC and DPF brick.The model calibration steps against a set of steady-state in-engine experiments allowing separate certain phenomena are discussed.As a final step, the model performance is assessed against a transient test during which all modelled processes are taking place simultaneously under highly dynamic driving conditions.This test is simulated imposing different integration time-steps to demonstrate the model´s potential for real-time applications.

The ability of flamelet models to reproduce turbulent combustion in devices such as diesel engines or gas turbines has enhanced the usage of these approaches in Computational Fluid Dynamics (CFD) simulations. The models based on turbulent look-up tables generated from counterflow laminar diffusion flames (DF model) permit drastic reduction of the computational cost of the CFD calculation. Nevertheless, for complex molecular fuels, such as n-heptane, the oxidation process involves hundreds of species and the calculation of the transport equations together with the ODE system that models the chemical kinetics for the DF solution becomes unaffordable for industrial devices where hundreds of flamelets are required. In this context, new hypotheses have to be introduced in order to reduce the computational cost maintaining the coherence of the combustion process. Recently, a new model known as Approximated Diffusion Flamelet (ADF) has been proposed with the aim of solving the turbulent combustion for complex fuels in a reduced time. However, the validity of this model is still an open question and has to be verified in order to justify subsequent CFD calculations. This work assesses the ADF model and its ability to reproduce accurately the combustion process and its main parameters for three fuels with different chemical complexity and boundary conditions by its comparison with the DF model. Results show that although some discrepancies arise, the ADF model has the ability to correctly describe the ignition delay and the "combustion structure in the auto-ignition zone that is the most relevant one for industrial processes. (C) 2017 Elsevier Inc. All rights reserved.

The ability of a computational fluid dynamics (CFD) simulation to reproduce the diesel-like reacting spray ignitionprocess and its corresponding flame structure strongly depends on both the fidelity of the chemical mechanismfor reproducing the oxidation of the fuel and also on how the turbulence-chemistry interaction (TCI) is modeled.Therefore, investigating the performance of different chemical mechanisms not only in perfect stirred reactors butdirectly in the diesel-like spray itself is of great interest in order to evaluate their suitability for being further appliedto CFD engine simulations.This research work focuses on applying a presumed probability density function (PDF) unsteady flamelet combustionmodel to the well-known spray A from the Engine Combustion Network (ECN), using three chemical mechanismswidely accepted by the scientific community as a way to figure out the influence of chemistry in the keycharacteristics of the combustion process in the frame of diesel-like spray simulations. Results confirm that in spiteof providing all of them correct trends for ignition delays (ID) and lift-off lengths (LOL), when comparing with experimentalresults, the structure of the flame presents noticeable differences, especially in the low and intermediatetemperatures and high equivalence ratio regions. Consequently, the selection of the chemical mechanism has animpact on the zones of influence of key species as observed in both spatial coordinates and also in the equivalenceratio-temperature maps. These differences are expected to be relevant considering the implications when couplingpollutant emissions models. The analysis of temperature and oxygen concentration parametric studies evidenceshow the observed differences are consistent and moderately dependent on the ambient conditions.DOI: http://dx.doi.org/10.4995/ILASS2017.2017.4746

6 Ideal models provide the simplest way to reproduce internal combustion engine (ICE) 7 cycles, but usually they do not represent with sufficient accuracy the actual behaviour of 8 an ICE. A suitable alternative for research and development applications is provided by 9 zero-dimensional (0D) thermodynamic models. Such models are very useful to predict the 10 instantaneous pressure and temperature in the combustion chamber, which in turn allow 11 the prediction of engine operation characteristics. However, their simplifying hypotheses 12 led in some cases to a leak of accuracy or a limited predictive capability. 13 This paper describes a 0D single-zone thermodynamic model that takes into account 14 the heat transfer to the chamber walls, the blow-by leakage, the fuel injection and engine 15 deformations, along with the instantaneous change of the gas properties. Special atten16 tion have been paid to the description of the specific sub-models that have been used for 17 the calculation of the energy and mass equations terms. Also the procedures followed 18 for the estimation of some mechanical and heat transfer parameters and the combustion 19 model fitting is detailed. After the fitting, the model was validated in a large amount 20 of operation points in a 4-cylinder 2-litre DI diesel engine, showing a good capability for 21 accurate predictions of the gas state during the closed cycle and engine performance. 22

AbstractThis article presents the basic operation characteristics of compression‐ignition (CI) or diesel engines, focusing on those features that are distinctive of these powerplants. Therefore, the focus has been placed on the thermofludynamic phenomena related to air management, injection, and combustion. Moreover, in every section, after presenting the basics, the most important expected technologies and strategies for future improvements are commented. Care has been taken for not repeating information that is contained in other article of the manual.First, the main characteristics, advantages, and challenges of theCIengine are discussed, often in contrast with the alternativeSIengine. Then, the main features of the injection combustion and pollutant formation processes are exposed. Even though these processes are completely interrelated and occur partially simultaneously at the same time, an effort has been made to separate their individual aspects in every section. Following, some sections are devoted to the air management requirements such as turbocharging, exhaust gas recirculation, and variable valve timing.

The increasingly stringent internal combustion engines (ICE) emissions regulations, has led to the extended use of after-treatment systems, giving progressively more importance to the engine efficiency optimization. In this context, the experimental methodologies to perform and analyse the energy balance show as a key issue to evaluate the potential of different engine strategies aimed at the consumption optimization and the improvement paths identification. This works deals with the complete description of an experimental energy balance tool, including the comprehensive description of the specific designed experimental installation used to the determination of each energy term involved in the energy balance. After the tool description, a study of the energy balance in the engine map of a DI Diesel engine was carried out, with the objective of determining the engine speed and load influence on each energy term. A subsequent parametric study varying the coolant temperature, the intake air temperature and the start of the injection (SOI) and their influence in the engine efficiency has been performed. The results shows that the variation of the coolant temperature has an almost negligible effect in terms of efficiency whilst cooling the air yields in an improvement about 1% and advancing the SOI about 1.5%.

New regulations on pollutants and, specially, on CO2 emissions could restrict the use of the internal combustion engine in automotive applications. This paper presents a review of different technologies under development for meeting such regulations, ranging from new combustion concepts to advanced boosting methods and after-treatment systems. Many of them need an accurate control of the operating conditions and, in many cases, they impose demanding requirements at a system integration level. In this framework, engine control disciplines will be key for the implementation and development of the next generation engines, taking profit of recent advancements in models, methods and sensors. According to authors’ opinion, the internal combustion engine will still be the dominant technology in automotive applications for the next decades.

The behavior of small turbochargers is deeply affected by heat transfer phenomena. The external heat losses of these machines are studied and a simplified model that takes into account both radiation and convective mechanisms has been proposed. The model has been adjusted in a turbocharger test bench for two different turbochargers, later on it has been validated against experimental measurements on an engine test bench. Finally, the model has been used to estimate the most important external heat flows among the different elements of the turbocharger, showing the operative points in which external heat transfer in turbochargers cannot be neglected.

The generalization of exhaust aftertreatment systems along with the growing awareness about climate change is leading to an increasing importance of the efficiency over other criteria during the design of reciprocating engines.Using experimental and theoretical tools to perform detailed global energy balance (GEB) of the engine is a key issue for assessing the potential of different strategies to reduce consumption.With the objective of improving the analysis of GEB, this paper describes a tool that allows calculating the detailed internal repartition of the fuel energy in DI Diesel engines.Starting from the instantaneous in-cylinder pressure, the tool is able to describe the different energy paths thanks to different submodels for all the relevant subsystems.Hence, the heat transfer from gases to engine walls is obtained with specific convective and radiative models in the chamber and ports; the repartition of the heat flux throughout the engine metal elements towards the oil and coolant is estimated with a lumped capacitance model; finally, the ancillary systems and friction losses are obtained through specific semiempirical submodels.The validation of the tool is performed in a 4cylinder DI Diesel engine instrumented to perform detailed experimental GEB.Finally, a simple analysis of combined internal and external analysis in the complete engine map shows the effect of operating conditions on each energy term.Thus it is demonstrated the utility of the proposed tool, that complements the experimental heat flow measurements in Diesel engine researches oriented to the reduction of energy consumption.

AbstractThis chapter summarizes the main concepts of the gas exchange process in reciprocating internal combustion engines. The main indexes used to measure gas exchange process quality are volumetric efficiency and pumping losses; they have been described and analyzed in this chapter. The compressible flow effects in valves and ports, the flow inertia effects in ports and ducts, and the dynamic effects generated by pulsating flow in the intake and exhaust lines have been briefly analyzed in the different subsections. The influence of valve cross section and timing on volumetric efficiency has been discussed in relation with the previously mentioned flow concepts. General relations between those phenomena and variables are provided through the different sections with the aim of highlighting those concepts that are relevant to the automotive engineer for the tasks of designing and diagnosing. Finally, exhaust gas recirculation (EGR) and pumping work are specifically studied as part of the wider air management concept and as complementary processes to the cylinder gas exchange process.

In this work, three Engine Combustion Network (ECN) single-hole nozzles with the same nominal characteristics have been tested under a wide range of conditions measuring spray penetration and spreading angle. n-Dodecane has been injected in non-evaporative conditions at different injection pressures ranging from 50 to 150 MPa and several levels of ambient densities from 7.6 to 22.8 kg/m(3). Nitrogen and Sulphur Hexafluoride (SF6) atmospheres have been explored and, in the first case, a temperature sweep from 300 to 550 K at constant gas density has been executed. Mie scattering has been used as the optical technique by employing a fast camera, whereas image processing has been performed through a home-built Mat lab code.Differences in spray penetration related to spray orifice diameter, spreading angle and start of injection transient have been found for the three injectors. Significant differences have been obtained when changing the ambient gas, whereas ambient temperature hardly affects the spray characteristics up to 400 K. However, a reduction in penetration has been observed beyond this point, mainly due to the sensitivity limitation of the technique as fuel evaporation becomes important. The different behavior observed when injecting in different gases could be explained due to the incomplete momentum transfer between spray droplets and entrained gas, together with the fact that there is an important change in speed of sound for the different gases, which affects the initial stage of the injection. (C) 2014 Elsevier Inc. All rights reserved.

There are many approaches addressing the problem of optimal energy management in hybrid electric vehicles; however, most of them optimise the control strategy for particular driving cycles. This paper takes into account that the driving cycle is not a priori known to obtain a near-optimal solution. The proposed method is based on analysing the power demands in a given receding horizon to estimate future driving conditions and minimise the fuel consumption while cancelling the expected battery energy consumption after a defined time horizon. Simulations show that the proposed method allows charge sustainability providing near-optimal results.