Soot temperature characterization of spray a flames by combined extinction and radiation methodology

[EN] Even though different optical techniques have been applied on 'Spray A' in-flame soot quantification within Engine Combustion Network in recent years, little information can be found for soot temperature measurement. In this study, a combined extinction and radiation methodology has been developed with different wavelengths and applied on quasi-steady Diesel flame to obtain the soot amount and temperature distribution simultaneously by considering self-absorption issues. All the measurements were conducted in a constant pressure combustion chamber. The fuel as well as the operating conditions and the injector used were chosen following the guidelines of the Engine Combustion Network. Uncertainty caused by wavelength selection was evaluated. Additionally, temperature-equivalence ratio maps were constructed by combining the measurements with a 1D spray model. Temperature fields during the quasi-steady combustion phase show peak temperatures around the limit of the radiation field, in agreement with a typical diffusion flame structure. Effects of different operating parameters on soot formation and temperature were investigated. Soot temperature increases dramatically with oxygen concentration, but it shows much less sensitivity with ambient temperature and injection pressure, which on the other hand have significant effects on soot production. (C) 2019 The Combustion Institute. Published by Elsevier Inc. All rights reserved.This study was partially funded by the Ministerio de Economia y Competitividad from Spain in the frame of the CHEST Project (TRA2017-89139-C2-1-R) and China Postdoctoral Science Foundation (2018M642176). This study was also partially supported by State Key Laboratory of Engines, Tianjin University.Xuan, T.; Desantes J.M.; Pastor, JV.; García-Oliver, JM. (2019). Soot temperature characterization of spray a flames by combined extinction and radiation methodology. Combustion and Flame. 204:290-303. https://doi.org/10.1016/j.combustflame.2019.03.02329030320

Effect of hydrogen addition on the OH* and CH* chemiluminescence emissions of premixed combustion of methane-air mixtures

[EN] Chemiluminescence emissions measurements of OH* and CH* are used to characterize the combustion of blends of methane and hydrogen in air in a constant volume combustion bomb, with two sets of initial conditions. The combined results of combustion development cover from 0.1 to 2.5 MPa. Burning velocity, heat release and unburned/burned gas temperatures are obtained from the pressure by using a two-zone thermodynamic combustion diagnostic model. Intensity of OH* and CH* increases with the initial temperature and the percentage of hydrogen, in parallel with the usual increase in burning velocity. The timings of the peaks of OH* and CH* chemiluminescence emissions are found to correlate respectively with the maximum rate of heat release and flame temperature. These results show that both chemiluminescence signals can be used to monitorize the burning process in combustion devices operating in the pressure range studied.Reyes, M.; Tinaut, F.; Giménez, B.; Pastor, JV. (2018). Effect of hydrogen addition on the OH* and CH* chemiluminescence emissions of premixed combustion of methane-air mixtures. International Journal of Hydrogen Energy. 43(42):19778-19791. https://doi.org/10.1016/j.ijhydene.2018.09.005S1977819791434

Effect of laser induced plasma ignition timing and location on Diesel spray combustion

[EN] An experimental study about the influence of the local conditions at the ignition location on combustion development of a direct injection spray is carried out in an optical engine. A laser induced plasma ignition system has been used to force the spray ignition, allowing comparison of combustion's evolution and stability with the case of conventional autoignition on the Diesel fuel in terms of ignition delay, rate of heat release, spray penetration and soot location evolution. The local equivalence ratio variation along the spray axis during the injection process was determined with a 1D spray model, previously calibrated and validated. Upper equivalence ratios limits for the ignition event of a direct injected Diesel spray, both in terms of ignition success possibilities and stability of the phenomena, could been determined thanks to application of the laser plasma ignition system. In all laser plasma induced ignition cases, heat release was found to be higher than for the autoignition reference cases, and it was found to be linked to a decrease of ignition delay, with the premixed peak in the rate of heat release curve progressively disappearing as the ignition delay time gets shorter. Ignition delay has been analyzed as a function of the laser position, too. It was found that ignition delay increases for plasma positions closer to the nozzle, indicating that the amount of energy introduced by the laser induced plasma is not the only parameter affecting combustion initiation, but local equivalence ratio plays a major role, too. (C) 2016 Elsevier Ltd. All rights reserved.The authors acknowledge that this research work has been partly funded by the Government of Spain under the project HiR-eCo TRA2014-58870-R and grant BES-2015-072119. The equipment used in this work has been partially supported by FEDER project ICTS-2012-06, framed in the operational program of unique scientific and technical infrastructure of the Ministry of Science and Innovation of Spain.Pastor, JV.; García-Oliver, JM.; García Martínez, A.; Pinotti, M. (2017). Effect of laser induced plasma ignition timing and location on Diesel spray combustion. Energy Conversion and Management. 133:41-55. https://doi.org/10.1016/j.enconman.2016.11.054S415513

Redesign and characterization of a single-cylinder optical research engine to allow full optical access and fast cleaning during combustion studies

[EN] This work describes the update of an optical engine design with the aim of increasing its capabilities when used for combustion studies. The criteria followed to perform the optical engine redesign were: maximize the optical accessibility to the combustion chamber, minimize the time consumed to clean the optical parts, and minimize the adaptation costs. To meet these requirements, a modular design using window-holders to fit the windows in the optical flange, was proposed. This novel solution allows optical access near the cylinder-head plane while maintaining high operating flexibility (i.e. fast transition between optical and metal engine, and very fast cleaning procedure). The new engine design has three additional optical accesses to the combustion chamber and resulted in more efficient operation compared to the original design, reducing the time consumed to clean the optical parts from 40 down to 10 min. Two main parameters of the new engine were characterized, the effective compression ratio and the rotatory flow field velocity (swirl). The characterization process revealed very similar values between the effective and geometric compression ratios (14.7:1 vs 14.2:1), which confirms the use of appropriate dimensional tolerances during the machining process and low amount of blow-by. Finally, the swirl ratio was characterized through particle image velocimetry measurements for different crank timings at 1200 rpm and motored conditions, using the optical piston with a cylindrical bowl. This method revealed swirl ratios varying from 1 to 1.7 depending on the timing considered, with increasing trend as the piston moves towards the top dead center.This work has been partially funded by the Spanish Government under the project HiReCo TRA2014-58870-R. The equipment used has been partially funded by FEDER project ICTS-2012-06, framed in the operational program of unique scientific and technical infrastructure of the Ministry of Science and Innovation of Spain. The author J. Monsalve-Serrano acknowledges the financial support from the Universitat Politecnica de Valencia under the grant "Ayudas Para la Contratacion de Doctores para el Acceso al Sistema Espanol de Ciencia, Tecnologia e Innovacion". The authors wish to thank Daniel Lerida for his technical work during the redesign process.Benajes, J.; Pastor, JV.; García Martínez, A.; Monsalve-Serrano, J. (2018). Redesign and characterization of a single-cylinder optical research engine to allow full optical access and fast cleaning during combustion studies. Experimental Techniques. 42(1):55-68. https://doi.org/10.1007/s40799-017-0219-9S5568421Dargay J, Gately D (1999) Income’s effect on car and vehicle ownership, worldwide: 1960-2015. 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Indicator codes: CSI 003 , APE 009. https://www.eea.europa.eu/data-and-maps/indicators/emissions-of-primary-particles-and-5/assessment-3(2009) Regulation (EC) 595/2009 of the European Parliament and of the Council of 18 June 2009 on type-approval of motor vehicles and engines with respect to emissions from heavy duty vehicles (Euro VI) and on access to vehicle repair and maintenance information and amending Regulation (EC) 715/2007 and Directive 2007/46/EC and repealing Directives 80/1269/EEC, 2005/55/EC and 2005/78/EC. Off J Eur Union L 188:1–13Pastor JV, García-Oliver JM, García A, Micó C, Möller S (2016) Application of optical diagnostics to the quantification of soot in n-alkane flames under diesel conditions. Combust Flame 164:212–223Desantes JM, Pastor JV, García-Oliver JM, Briceño FJ (2014) An experimental analysis on the evolution of the transient tip penetration in reacting diesel sprays. Combust Flame 161(8):2137–2150Desantes JM, Arregle JM, Lopez JJ (2006) Scaling laws for free turbulent gas jets and diesel-like sprays. Atomization Sprays 16:443–473Desantes JM, Torregrosa AJ, Broatch A (2001) Experiments on flow noise generation in simple exhaust geometries. Acustica 87(1):46–55Benajes J, García A, Monsalve-Serrano J, Boronat V Achieving clean and efficient engine operation up to full load by combining optimized RCCI and dual-fuel diesel-gasoline combustion strategies. Energy Convers Manag 136:142–151Payri R, Gimeno J, Bardi M, Plazas A (2013) Study liquid length penetration results obtained with a direct acting piezo electric injector. Appl Energy 106:152–162Garcia A, Monsalve-Serrano J, Heuser B, Jakob M, Kremer F, Pischinger S (2016) Influence of fuel properties on fundamental spray characteristics and soot emissions using different tailor-made fuels from biomass. Energy Convers Manag 108:243–254An H, Chung J, Lee S, Song S (2015) The effects of hydrogen addition on the auto-ignition delay of homogeneous primary reference fuel/air mixtures in a rapid compression machine. Int J Hydrog Energy 40(40):13994–14005Payri F, Desantes JM, Pastor JV (1996) LDV measurements of the flow inside the combustion chamber of a 4-valve D.I. Diesel engine with axisymmetric piston-bowls. Exp Fluids 22(2):118–128Benajes J, Molina S, García A, Monsalve-Serrano J, Durrett R (2014) Conceptual model description of the double injection strategy applied to the gasoline partially premixed compression ignition combustion concept with spark assistance. Appl Energy 129:1–9Desantes JM, Lopez JJ, García JM (2007) Evaporative diesel spray modeling. Atomization Sprays 17:193–231Battistoni M, Mariani F, Risi F, Poggiani C, Combustion CFD (2015) Modeling of a spark ignited optical access engine fueled with gasoline and ethanol. Energy Procedia 82:424–431Benajes J, García A, Pastor JM, Monsalve-Serrano J (2016) Effects of piston bowl geometry on reactivity controlled compression ignition heat transfer and combustion losses at different engine loads. Energy 98:64–77Benajes J, García A, Monsalve-Serrano J, Balloul I, Pradel G (2016) An assessment of the dual-mode RCCI/CDC capabilities in a EURO VI medium-duty diesel engine fueled with an intermediate ethanol-gasoline blend and biodiesel. Energy Convers Manag 123:381–391Benajes J, Martín J, García A, Villalta D, Warey A (2015) In-cylinder soot radiation heat transfer in direct-injection diesel engines. Energy Convers Manag 106:414–427Luján JM, Climent H, Dolz V, Moratal A, Borges-Alejo J, Soukeur Z (2016) Potential of exhaust heat recovery for intake charge heating in a diesel engine transient operation at cold conditions. Appl Therm Eng 105:501–508Bohla T, Tiana G, Zengb W, Heb X, Roskilly A (2014) Optical investigation on diesel engine fuelled by vegetable oils. Inter Conf on Appl energy, ICAE2014. Energy Procedia 61:670–674Bizon K, Continillo G, Lombardi S, Sementa P, Vaglieco B (2016) Independent component analysis of cycle resolved combustion images from a spark ignition optical engine. Combust Flame 163:258–269Mancaruso E, Sequino L, Vaglieco B (2016) Analysis of the pilot injection running common rail strategies in a research diesel engine by means of infrared diagnostics and 1d model. Fuel 178:188–201Zeng W, Sjöberg M, Reuss D, Hu Z (2016) High-speed PIV, spray, combustion luminosity, and infrared fuel-vapor imaging for probing tumble-flow-induced asymmetry of gasoline distribution in a spray-guided stratified-charge DISI engine. Proc Combust Inst 36(3):3459–3466Catapano F, Sementa P, Vaglieco B (2016) Air-fuel mixing and combustion behavior of gasoline-ethanol blends in a GDI wall-guided turbocharged multi-cylinder optical engine. Renew Energy 96:319–332Merola S, Tornatore C, Irimescu A, Marchitto L, Valentino G (2016) Optical diagnostics of early flame development in a DISI (direct injection spark ignition) engine fueled with n-butanol and gasoline. Energy 108:50–62Marseglia G, Costa M, Catapano F, Sementa P, Vaglieco B (2017) Study about the link between injection strategy and knock onset in an optically accessible multi-cylinder GDI engine. Energy Convers Manag 134:1–19Irimescu A, Merola S, Tornatore C, Valentino G (2016) Effect of coolant temperature on air-fuel mixture formation and combustion in an optical direct injection spark ignition engine fueled with gasoline and butanol. J Energy Inst 90:452–465. https://doi.org/10.1016/j.joei.2016.03.004.Irimescu A, Merola S, Valentino G (2016) Application of an entrainment turbulent combustion model with validation based on the distribution of chemical species in an optical spark ignition engine. Appl Energy 162:908–923Pastor JV, García-Oliver JM, García A, Pinotti M (2016) Laser induced plasma methodology for ignition control in direct injection sprays. Energy Convers Manag 120:144–156Regan C, Chun K, Schock H (1987) Engine flow visualization using a copper vapor laser. Proc SPIE: New Dev Appl Gas Lasers 737:17–27Le Coz J-F, Henriot S, Pinchon P (1990) An experimental and computational analysis of the flow field in a four-valve spark ignition engine-focus on cycle-resolved turbulence. SAE International in United States. https://doi.org/10.4271/900056Catapano F, Sementa P, Vaglieco B (2013) Optical characterization of bio-ethanol injection and combustion in a small DISI engine for two wheels vehicles. Fuel 106:651–666Bowditch F (1958) Cylinder and Piston Assembly. US Patent, App 2,919,688, 2,919,688 https://www.google.com/patents/US2919688Pastor JV, García-Oliver JM, García A, Micó C, Durrett R (2013) A spectroscopy study of gasoline partially premixed compression ignition spark assisted combustion. Appl Energy 104:568–575Di Iorio S.; Sementa P.; Vaglieco B. Analysis of combustion of methane and hydrogen–methane blends in small DI SI (direct injection spark ignition) engine using advanced diagnostics. Energy 2016, 108, 99–107.Sementa P, Vaglieco B, Catapano F (2012) Thermodynamic and optical characterizations of a high performance GDI engine operating in homogeneous and stratified charge mixture conditions fueled with gasoline and bio-ethanol. Fuel 96:204–219Richman R, Reynolds W (1984) The development of a transparent cylinder engine for piston engine fluid mechanics research. SAE International in United States. https://doi.org/10.4271/840379Bates S (1988) A transparent engine for flow and combustion visualization studies. SAE International in United States. https://doi.org/10.4271/880520Zhang Y, Zhang R, Rao L, Kim D, Kook S (2017) The influence of a large methyl ester on in-flame soot particle structures in a small-bore diesel engine. Fuel 194:423–435Reuss D (2000) Cyclic variability of large-scale turbulent structures in directed and undirected IC engine flows. SAE International in United States. https://doi.org/10.4271/2000-01-0246López JJ, García-Oliver JM, García A, Domenech V (2014) Gasoline effects on spray characteristics, mixing and auto-ignition processes in a CI engine under partially premixed combustion conditions. Appl Therm Eng 70(1):996–1006Benajes J, García A, Domenech V, Durrett R (2013) An investigation of partially premixed compression ignition combustion using gasoline and spark assistance. 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An Optical Engine Used as a Physical Model for Studies of the Combustion Process Applying a Two-Color Pyrometry Technique

[EN] This work describes an experimental installation for the investigation of the combustion and injection processes. This installation is based on a two-stroke direct injection diesel engine with a total displacement of 3 L and a cylinder head equipped with three quartz windows. The windows are optical accesses that allow studying the process of injection, the atomization and evaporation of the fuel jet in an inert atmosphere (nitrogen), and the combustion process in a reactive atmosphere (ambient air). Additionally, the application of a two-color pyrometry technique to measure soot formation in this facility is presented. A methodological study is carried out regarding the influence of the dynamic range of the detectors and the wavelengths used. Maps of KL2C, flame temperature, and error probability are presented. The use of cameras with high dynamic range provides better results since the system seems to be less sensitive to measurement noise, and fewer points are obtained with a non-physical solution. Moreover, an appropriate combination of interference filters can improve the reliability of the solution. The greater the difference between the wavelengths of both interference filters, the fewer points with a non-physical solution, which improves the reliability of results.This research was funded by Castilla-La Mancha Government to the project grant number ASUAV Ref. SBPLY/19/180501/000116.Corral-Gómez, L.; Armas, O.; Soriano, JA.; Pastor, JV.; García-Oliver, JM.; Micó, C. (2022). An Optical Engine Used as a Physical Model for Studies of the Combustion Process Applying a Two-Color Pyrometry Technique. Energies. 15(13):1-17. https://doi.org/10.3390/en15134717117151

A Synergic Application of High-Oxygenated E-Fuels and New Bowl Designs for Low Soot Emissions: An Optical Analysis

[EN] Synthetic fuels significantly reduce pollutant emissions and the carbon footprint of ICE applications. Among these fuels, oxymethylene dimethyl ethers (OMEX) are an excellent candidate to entirely or partially replace conventional fuels in compression ignition (CI) engines due to their attractive properties. The very low soot particle formation tendency allows the decoupling of the soot-NOX trade-off in CI engines. In addition, innovative piston geometries have the potential to reduce soot formation inside the cylinder in the late combustion stage. This work aims to analyze the potential of combining OMEX with an innovative piston geometry to reduce soot formation inside the cylinder. In this way, several blends of OMEX-Diesel were tested using a radial-lips bowl geometry and a conventional reentrant bowl. Tests were conducted in an optically accessible engine under simulated EGR conditions, reducing the in-cylinder oxygen content. For this purpose, 2-colour pyrometry and high-speed excited state hydroxyl chemiluminescence techniques were applied to trace the in-cylinder soot formation and oxidation processes. The results confirm that increasing OMEX in Diesel improves the in-cylinder soot reduction under low oxygen conditions for both piston geometries. Moreover, using radial lips bowl geometry significantly improves the soot reduction, from 17% using neat Diesel to 70% less at the highest OMEX quantity studied in this paper.This work has been partially funded by Universitat Politècnica de València through the program of access contracts for PhD research staff in Research Structures of the Universitat Politècnica de València with reference PAID-10-22. The presence of Cinzia Tornatore at Universitat Politècnica de València was funded by the Short Term Mobility (STM) Program of the Italian National Research Council.Pastor, JV.; Micó, C.; De Vargas Lewiski, F.; Tejada-Magraner, FJ.; Tornatore, C. (2023). A Synergic Application of High-Oxygenated E-Fuels and New Bowl Designs for Low Soot Emissions: An Optical Analysis. Applied Sciences. 13(14). https://doi.org/10.3390/app13148560131

An experimental analysis on the evolution of the transient tip penetration in reacting Diesel sprays

Schlieren imaging has helped deeply characterize the behavior of Diesel spray when injected into an oxygen-free ambient. However, when considering the transient penetration of the reacting spray after autoignition, i.e. the Diesel flame, few studies have been found in literature. Differences among optical setups as well as among experimental conditions have not allowed clear conclusions to be drawn on this issue. Furthermore, soot radiation may have a strong effect on the image quality, which cannot be neglected. The present paper reports an investigation on the transient evolution of Diesel flame based upon schlieren imaging. Experimental conditions have spanned values of injection pressure, ambient temperature and density for typical Diesel engine conditions. An optimized optical setup has been used, which makes it possible to obtain results without soot interference. Based on observations for a long injection event (4 ms Energizing Time), the analysis has resorted to extensive comparison of inert and reacting sprays parameters, which have made it possible to define different phases after autoignition. Shortly after autoignition, axial and radial expansion of the spray have been observed in terms of tip penetration and radial cone angle. After that, during a stabilization phase, the reacting spray penetrates at a similar rate as the inert one. Later, the reacting spray undergoes an acceleration period, where it penetrates at a faster rate than the inert one. Finally, the flame enters a quasi-steady penetration phase, where the ratio of reacting and inert penetration stabilizes at a nearly constant value. The duration of the reacting spray penetration stages shows modifications when varying engine parameters such as air temperature, air density, injection pressure, and nozzle diameter. However, the proportionality between reacting and inert penetration has been observed to depend mainly on temperature, in agreement with observed reductions in entrainment when shifting from inert to reacting conditions. (C) 2014 The Combustion Institute. Published by Elsevier Inc. All rights reserved.This work was partially funded by the Spanish Ministry of Science and Technology through the "EFFICIENT AND CLEAN COMBUSTION IN COMPRESSION IGNITION ENGINES USING THE DUAL-FUEL CONCEPT" Project (TRA2011-26359). Mr. Francisco J. Briceno wishes to acknowledge financial support through a PhD studies Grant (AP2008-02231) also sponsored by the Spanish Ministry of Education and Science. Last, but not least, authors would like to express their gratitude to Jose Enrique del Rey for his enthusiasm, proactiveness and help during data acquisition.Desantes Fernández, JM.; Pastor, JV.; García Oliver, JM.; Briceño Sánchez, FJ. (2014). An experimental analysis on the evolution of the transient tip penetration in reacting Diesel sprays. Combustion and Flame. 161(8):2137-2150. https://doi.org/10.1016/j.combustflame.2014.01.022S21372150161

Study of turbocharger shaft motion by means of non-invasive optical techniques: Application to the behaviour analysis in turbocharger lubrication failures

[EN] This paper presents a novel non-invasive technique to estimate the turbocharger shaft whirl motion. The aim of this article is to present a system for monitoring the shaft motion of a turbocharger, which will be used in turbocharger destructive testing. To achieve this, a camera and a light source were installed in a turbocharger test bench with a controlled lubrication circuit. An image recording methodology and a process algorithm have been developed, in order to estimate the shaft motion. This processing consists on differentiating specific zones of the image, in order to obtain their coordinates. Two reference points have been configured on the compressor side, which help to calculate the relative position of the shaft, avoiding the errors due to structural vibrations. Maximum eccentricity of the turbocharger has been determined and it has been compared with shaft motion when it is spinning in different conditions. A luminosity study has been also done, in order to improve the process and to obtain locus of shaft position in a picture exposition time period. The technique has been applied to diagnosis of a lubrication failure test and the main results will be presented in this article: like shaft motion figures; thermodynamic variables and pictures of the shaft while it is spinning at abnormal lubrication conditions. The measuring components used in this technique have the ability to withstand the catastrophic failure of the turbocharger in this type of test. © 2012 Elsevier Ltd.Pastor, JV.; Serrano, J.; Dolz, V.; López Hidalgo, M.; Bouffaud, F. (2012). Study of turbocharger shaft motion by means of non-invasive optical techniques: Application to the behaviour analysis in turbocharger lubrication failures. Mechanical Systems and Signal Processing. 32:292-305. doi:10.1016/j.ymssp.2012.04.020S2923053

Simultaneous high-speed spectroscopy and 2-color pyrometry analysis in an optical compression ignition engine fueled with OME X -diesel blends

[EN] E-fuels are a very attractive way for improving the well-to-wheel emissions of CO 2 in internal combustion engines. In the particular case of compression ignition engines, the Oxymethylene dimethyl ether (OME X ), an e-fuel with nearly soot-free combustion under mixing-controlled conditions, is a good candidate for the replacement of fossil fuels. However, the Lower Heating Value of OME X is nearly half of the diesel fuel, which means that much longer injection durations are required in the real engine. In addition, the very low viscosity and lubricity of OME X can damage the injection system if used pure, but it can be an interesting fuel when blended with conventional diesel. Thus, the main objective of this paper is to evaluate the potential of OME X -diesel blends to bypass these OME X limitations whilst keeping low soot formation trends. For this purpose, a single cylinder optical diesel engine at part load was employed. The soot production for the different fuel blends was analyzed by applying three different high-speed imaging techniques: natural luminosity, flame spectroscopy and 2-color pyrometry. Natural luminosity analysis showed that the flame light intensity scales with diesel fraction up to 30% of diesel in the blend. The spectroscopy analysis has revealed that soot formation of OME X fuel is almost null. When blended with diesel at 50%, although soot formation is still lower than for pure diesel, higher soot levels are obtained in the last stages of the cycle as a consequence of the longer injections required.This work was partially funded by Generalitat Valenciana through the Programa Santiago Grisola (GRISOLIAP/2018/142) program.Pastor, JV.; García Martínez, A.; Micó, C.; De Vargas Lewiski, F. (2021). Simultaneous high-speed spectroscopy and 2-color pyrometry analysis in an optical compression ignition engine fueled with OME X -diesel blends. Combustion and Flame. 230:1-13. https://doi.org/10.1016/j.combustflame.2021.111437S11323

Experimental Study of the Effect of Hydrotreated Vegetable Oil and Oxymethylene Ethers on Main Spray and Combustion Characteristics under Engine Combustion Network Spray A Conditions

[EN] Featured Application This work contributes to the understanding of the macroscopic characteristics of the spray as well as to the evolution of the combustion process for alternative fuels. All these fuels have been studied under the same operating conditions than diesel therefore the comparison can be made directly, leaving in evidence that some fuels can achieve a similar behavior to diesel in terms of auto ignition but avoiding one of the biggest disadvantages of diesel such as the soot formation. Moreover, the quantification of characteristic parameters such as ignition delay, liquid length, vapor penetration and flame lift-off length represent the most important data to adjust and subsequently validate the computational models that simulate the spray evolution and combustion development of these alternative fuels inside the combustion chamber. The stringent emission regulations have motivated the development of cleaner fuels as diesel surrogates. However, their different physical-chemical properties make the study of their behavior in compression ignition engines essential. In this sense, optical techniques are a very effective tool for determining the spray evolution and combustion characteristics occurring in the combustion chamber. In this work, quantitative parameters describing the evolution of diesel-like sprays such as liquid length, spray penetration, ignition delay, lift-off length and flame penetration as well as the soot formation were tested in a constant high pressure and high temperature installation using schlieren, OH* chemiluminescence and diffused back-illumination extinction imaging techniques. Boundary conditions such as rail pressure, chamber density and temperature were defined using guidelines from the Engine Combustion Network (ECN). Two paraffinic fuels (dodecane and a renewable hydrotreated vegetable oil (HVO)) and two oxygenated fuels (methylal identified as OME(1)and a blend of oxymethylene ethers, identified as OMEx) were tested and compared to a conventional diesel fuel used as reference. Results showed that paraffinic fuels and OME(x)sprays have similar behavior in terms of global combustion metrics. In the case of OME1, a shorter liquid length, but longer ignition delay time and flame lift-off length were observed. However, in terms of soot formation, a big difference between paraffinic and oxygenated fuels could be appreciated. While paraffinic fuels did not show any significant decrease of soot formation when compared to diesel fuel, soot formed by OME(1)and OME(x)was below the detection threshold in all tested conditions.This research has been partly funded by the European Union's Horizon 2020 Programme through the ENERXICO project, grant agreement no 828947, and from the Mexican Department of Energy, CONACYT-SENER Hidrocarburos grant agreement no B-S-69926 and by Universitat Politecnica de Valencia through the Programa de Ayudas de Investigacion y Desarrollo (PAID-01-18).Pastor, JV.; García-Oliver, JM.; Mico Reche, C.; Garcia-Carrero, AA.; Gómez, A. (2020). Experimental Study of the Effect of Hydrotreated Vegetable Oil and Oxymethylene Ethers on Main Spray and Combustion Characteristics under Engine Combustion Network Spray A Conditions. Applied Sciences. 10(16):1-20. https://doi.org/10.3390/app10165460S1201016Reşitoğlu, İ. A., Altinişik, K., & Keskin, A. (2014). 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