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

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

Analysis of the Influence of Diesel Spray Injection on the Ignition and Soot Formation in Multiple Injection Strategy

[EN] Multiple injection strategies have increased their capabilities along with the evolution of injection system technologies up to the point that nowadays it is possible to inject eight different pulses, permitting to improve the engine performance, and consequently, emissions. The present work was realized for two simplified strategies: a pilot-main and a main-post, in order to analyze the influence of an auxiliary pulse on the main and otherwise, in reactive conditions for two pilot/post quantities and four hydraulic dwell times. The study was carried out by employing two optical techniques: diffused back-illumination with flame bandpass chemiluminescence for measuring soot, represented by soot-maps distribution, and single-pass schlieren for ignition delay (ID). Furthermore, a novel methodology for decoupling the start of combustion (SOC) of the second pulse was developed and successfully validated. From the ignition delay results, it was found for all test points that the pilot injection enhanced conditions, which promote a faster ignition of the main pulse, also at higher chamber temperatures, all conditions presented a separate combustion event for each injection. In emission terms, soot increased in the pilot-main strategies compared to its single injection case, as well as, in conditions that promote faster-premixed combustion.This research has been partially funded by Spanish "Ministerio de Ciencia, Innovacion y Universidades" through project RTI2018-099706-B-100. Additionally, the experimental hardware was purchased through FEDER and Generalitat Valenciana under project IDIFEDER/2018/037.Payri, R.; García-Oliver, JM.; Mendoza, V.; Viera, A. (2020). Analysis of the Influence of Diesel Spray Injection on the Ignition and Soot Formation in Multiple Injection Strategy. Energies. 13(13):1-22. https://doi.org/10.3390/en13133505S1221313Musculus, M. P. B., Miles, P. C., & Pickett, L. M. (2013). Conceptual models for partially premixed low-temperature diesel combustion. Progress in Energy and Combustion Science, 39(2-3), 246-283. doi:10.1016/j.pecs.2012.09.001Han, S., Kim, J., & Bae, C. (2014). Effect of air–fuel mixing quality on characteristics of conventional and low temperature diesel combustion. Applied Energy, 119, 454-466. doi:10.1016/j.apenergy.2013.12.045Mingfa, Y., Hu, W., Zunqing, Z., & Yan, Y. (2009). Experimental Study of Multiple Injections and Coupling Effects of Multi-Injection and EGR in a HD Diesel Engine. SAE Technical Paper Series. doi:10.4271/2009-01-2807Schöppe, D., Stahl, C., Krüger, G., & Dian, V. (2012). Servo-Driven Piezo Common Rail Diesel Injection System. ATZautotechnology, 12(2), 42-47. doi:10.1365/s35595-012-0107-yO’Connor, J., & Musculus, M. (2013). Post Injections for Soot Reduction in Diesel Engines: A Review of Current Understanding. SAE International Journal of Engines, 6(1), 400-421. doi:10.4271/2013-01-0917Samuel J, J., & A, R. (2018). A physics-based model for real-time prediction of ignition delays of multi-pulse fuel injections in direct-injection diesel engines. International Journal of Engine Research, 21(3), 540-558. doi:10.1177/1468087418776876Siebers, D. L., & Higgins, B. (2001). Flame Lift-Off on Direct-Injection Diesel Sprays Under Quiescent Conditions. SAE Technical Paper Series. doi:10.4271/2001-01-0530Benajes, J., Payri, R., Bardi, M., & Martí-Aldaraví, P. (2013). Experimental characterization of diesel ignition and lift-off length using a single-hole ECN injector. Applied Thermal Engineering, 58(1-2), 554-563. doi:10.1016/j.applthermaleng.2013.04.044Payri, R., Salvador, F. J., Manin, J., & Viera, A. (2016). Diesel ignition delay and lift-off length through different methodologies using a multi-hole injector. Applied Energy, 162, 541-550. doi:10.1016/j.apenergy.2015.10.118Higgins, B., Siebers, D. L., & Aradi, A. (2000). Diesel-Spray Ignition and Premixed-Burn Behavior. SAE Technical Paper Series. doi:10.4271/2000-01-0940O’Connor, J., & Musculus, M. (2013). Effects of exhaust gas recirculation and load on soot in a heavy-duty optical diesel engine with close-coupled post injections for high-efficiency combustion phasing. International Journal of Engine Research, 15(4), 421-443. doi:10.1177/1468087413488767Baert, R. S. G., Frijters, P. J. M., Somers, B., Luijten, C. C. M., & de Boer, W. (2009). Design and Operation of a High Pressure, High Temperature Cell for HD Diesel Spray Diagnostics: Guidelines and Results. SAE Technical Paper Series. doi:10.4271/2009-01-0649Payri, R., Gimeno, J., Martí-Aldaraví, P., & Viera, A. (2020). Measurements of the mass allocation for multiple injection strategies using the rate of injection and momentum flux signals. International Journal of Engine Research, 22(4), 1180-1195. doi:10.1177/1468087419894854Payri, R., Salvador, F. J., Abboud, R., & Viera, A. (2020). Study of evaporative diesel spray interaction in multiple injections using optical diagnostics. Applied Thermal Engineering, 176, 115402. doi:10.1016/j.applthermaleng.2020.115402Tschöke, H., & Marohn, R. (Eds.). (2017). 10. Tagung Diesel- und Benzindirekteinspritzung 2016. Proceedings. doi:10.1007/978-3-658-15327-4Payri, R., Bracho, G., Marti-Aldaravi, P., & Viera, A. (2017). Nozzle Geometry Size Influence on Reactive Spray Development: From Spray B to Heavy Duty Applications. SAE Technical Paper Series. doi:10.4271/2017-01-0846Payri, R., Gimeno, J., Cardona, S., & Ayyapureddi, S. (2019). Experimental study of the influence of the fuel and boundary conditions over the soot formation in multi-hole diesel injectors using high-speed color diffused back-illumination technique. Applied Thermal Engineering, 158, 113746. doi:10.1016/j.applthermaleng.2019.113746Meijer, M., Somers, B., Johnson, J., Naber, J., Lee, S.-Y., Malbec, L. M., … Bazyn, T. (2012). ENGINE COMBUSTION NETWORK (ECN): CHARACTERIZATION AND COMPARISON OF BOUNDARY CONDITIONS FOR DIFFERENT COMBUSTION VESSELS. Atomization and Sprays, 22(9), 777-806. doi:10.1615/atomizspr.2012006083Ghandhi, J. B., & Heim, D. M. (2009). An optimized optical system for backlit imaging. Review of Scientific Instruments, 80(5), 056105. doi:10.1063/1.3128728Settles, G. S. (2001). Schlieren and Shadowgraph Techniques. doi:10.1007/978-3-642-56640-0Manin, J., Bardi, M., Pickett, L. M., & Manin, J. (2012). SP2-4 Evaluation of the liquid length via diffused back-illumination imaging in vaporizing diesel sprays(SP: Spray and Spray Combustion,General Session Papers). The Proceedings of the International symposium on diagnostics and modeling of combustion in internal combustion engines, 2012.8(0), 665-673. doi:10.1299/jmsesdm.2012.8.665Payri, R., Salvador, F. J., Bracho, G., & Viera, A. (2017). Differences between single and double-pass schlieren imaging on diesel vapor spray characteristics. Applied Thermal Engineering, 125, 220-231. doi:10.1016/j.applthermaleng.2017.06.140Payri, R., Gimeno, J., Bracho, G., & Vaquerizo, D. (2016). Study of liquid and vapor phase behavior on Diesel sprays for heavy duty engine nozzles. Applied Thermal Engineering, 107, 365-378. doi:10.1016/j.applthermaleng.2016.06.159Pastor, J. V., Payri, R., Garcia-Oliver, J. M., & Nerva, J.-G. (2012). Schlieren Measurements of the ECN-Spray A Penetration under Inert and Reacting Conditions. SAE Technical Paper Series. doi:10.4271/2012-01-0456Siebers, D. L. (1998). Liquid-Phase Fuel Penetration in Diesel Sprays. SAE Technical Paper Series. doi:10.4271/980809Skeen, S. A., Manin, J., Pickett, L. M., Cenker, E., Bruneaux, G., Kondo, K., … Hawkes, E. (2016). A Progress Review on Soot Experiments and Modeling in the Engine Combustion Network (ECN). SAE International Journal of Engines, 9(2), 883-898. doi:10.4271/2016-01-0734Payri, R., García-Oliver, J. M., Xuan, T., & Bardi, M. (2015). A study on diesel spray tip penetration and radial expansion under reacting conditions. Applied Thermal Engineering, 90, 619-629. doi:10.1016/j.applthermaleng.2015.07.042Wu, G., Zhou, X., & Li, T. (2019). Temporal Evolution of Split-Injected Fuel Spray at Elevated Chamber Pressures. Energies, 12(22), 4284. doi:10.3390/en12224284Maes, N., Bakker, P. C., Dam, N., & Somers, B. (2017). Transient Flame Development in a Constant-Volume Vessel Using a Split-Scheme Injection Strategy. SAE International Journal of Fuels and Lubricants, 10(2), 318-327. doi:10.4271/2017-01-0815Park, C., & Busch, S. (2017). The influence of pilot injection on high-temperature ignition processes and early flame structure in a high-speed direct injection diesel engine. International Journal of Engine Research, 19(6), 668-681. doi:10.1177/1468087417728630Kozlov, A., Grinev, V., Terenchenko, A., & Kornilov, G. (2019). An Investigation of the Effect of Fuel Supply Parameters on Combustion Process of the Heavy-Duty Dual-Fuel Diesel Ignited Gas Engine. Energies, 12(12), 2280. doi:10.3390/en12122280Desantes, J. M., García-Oliver, J. M., García, A., & Xuan, T. (2018). Optical study on characteristics of non-reacting and reacting diesel spray with different strategies of split injection. International Journal of Engine Research, 20(6), 606-623. doi:10.1177/1468087418773012Jorques Moreno, C., Stenlaas, O., & Tunestal, P. (2017). Influence of Small Pilot on Main Injection in a Heavy-Duty Diesel Engine. SAE Technical Paper Series. doi:10.4271/2017-01-0708Ameen, M. M., & Abraham, J. (2014). RANS and LES Study of Lift-Off Physics in Reacting Diesel Jets. SAE Technical Paper Series. doi:10.4271/2014-01-1118Pickett, L. M., & Siebers, D. L. (2004). Soot in diesel fuel jets: effects of ambient temperature, ambient density, and injection pressure. Combustion and Flame, 138(1-2), 114-135. doi:10.1016/j.combustflame.2004.04.006Wu, T., Yao, A., Yao, C., Pan, W., Wei, H., Chen, C., & Gao, J. (2018). Effect of diesel late-injection on combustion and emissions characteristics of diesel/methanol dual fuel engine. Fuel, 233, 317-327. doi:10.1016/j.fuel.2018.06.063Peraza, J. E., Payri, R., Gimeno, J., & Bazyn, T. (2017). Spray/wall interaction analysis on an ECN single-hole injector at diesel-like conditions through Schlieren visualization. Proceedings ILASS–Europe 2017. 28th Conference on Liquid Atomization and Spray Systems. doi:10.4995/ilass2017.2017.4709Zhao, L., Torelli, R., Zhu, X., Naber, J., Lee, S.-Y., Som, S., … Raessi, M. (2018). Evaluation of Diesel Spray-Wall Interaction and Morphology around Impingement Location. SAE Technical Paper Series. doi:10.4271/2018-01-027

Development of a soot radiation model for diesel flames

[EN] This paper describes a radiation model for diesel sprays that can predict the heat losses based on spray characteristics to the spray plume due to radiation. The model is based on three sub-models: spray model, soot model and radiation model. The spray model is a one-dimensional model that simulates the axial and radial distribution of a fuel spray for each instant. The soot model is a one-dimensional tool, which is based on formation and oxidation processes calculating the axial and radial soot concentration profile for each instant. The output results of the two sub-models are used as input information for the radiation model, which obtains the radiation heat transfer values for a diesel flame. The experimental measurements used to adjust the different constants and to validate the sub-models were performed in a high-pressure high-temperature vessel using three different optical techniques: Schlieren, to obtain spray penetration, Diffused Back-Illumination technique (DBI) for the soot concentration and the 2-color method for calculating the soot temperature and concentration. The radiant fraction shows values from 0.11% to 0.43% with respect to the total energy of the fuel depending on the operating condition. Taking into account the different assumptions taken for modeling the spray radiation, these results are consistent with those obtained in the literature, in which the radiation was characterized under similar conditions.The authors acknowledge FEDER and Spanish Ministerio de Economía y Competitividad for partially supporting this research through TRANCO project (TRA2017-87694-R).López, JJ.; García-Oliver, JM.; García Martínez, A.; Villalta-Lara, D. (2019). Development of a soot radiation model for diesel flames. Applied Thermal Engineering. 157:1-10. https://doi.org/10.1016/j.applthermaleng.2019.04.120S11015

Study of Air Flow Interaction with Pilot Injections in a Diesel Engine by Means of PIV Measurements

[EN] With ever-demanding emission legislations in Compression Ignition (CI) engines, new premixed combustion strategies have been developed in recent years seeking both, emissions and performance improvements. Since it has been shown that in-cylinder air flow affects the combustion process, and hence the overall engine performance, the study of swirling structures and its interaction with fuel injection are of great interest. In this regard, possible Turbulent Kinetic Energy (TKE) distribution changes after fuel injection may be a key parameter for achieving performance improvements by reducing in-cylinder heat transfer. Consequently, this paper aims to gain an insight into spray-swirl interaction through the analysis of in-cylinder velocity fields measured by Particle Image Velocimetry (PIV) when PCCI conditions are proposed. Experiments are carried out in a single cylinder optical Diesel engine with bowl-in-piston geometry. A standard 2D PIV system is used for measuring instantaneous velocity fields in a cross section (swirl-plane) inside the combustion chamber. The test matrix is based on an advanced single pilot injection with energizing time and injection pressure sweeps at different crank-angles. Results show that swirl ratio decreases with the increase of injected fuel mass. The decrease in swirl ratio also comes with a homogenization of the flow field. This homogenization along with lower swirl ratios might decrease heat transfer to cylinder walls.The support of the Spanish Ministry of Economy and Competitiveness (TRA2014-58870-R,) is greatly acknowledged through HiReCo project.García-Oliver, JM.; García Martínez, A.; Gil, A.; Pachano-Prieto, LM. (2017). Study of Air Flow Interaction with Pilot Injections in a Diesel Engine by Means of PIV Measurements. SAE International Journal of Engines. 10(3):740-751. doi:10.4271/2017-01-0617S74075110

Optical study on characteristics of non-reacting and reacting diesel spray with different strategies of split injection

[EN] Even though studies on split-injection strategies have been published in recent years, there are still many remaining questions about how the first injection affects the mixing and combustion processes of the second one by changing the dwell time between both injection events or by the first injection quantity. In this article, split-injection diesel sprays with different injection strategies are investigated. Visualization of n-dodecane sprays was carried out under both non-reacting and reacting operating conditions in an optically accessible two-stroke engine equipped with a single-hole diesel injector. High-speed Schlieren imaging was applied to visualize the spray geometry development, while diffused backgroundillumination extinction imaging was applied to quantify the instantaneous soot production (net result of soot formation and oxidation). For non-reacting conditions, it was found that the vapor phase of second injection penetrates faster with a shorter dwell time and independently of the duration of the first injection. This could be explained in terms of onedimensional spray model results, which provided information on the local mixing and momentum state within the flow. Under reacting conditions, interaction between the second injection and combustion recession of the first injection is observed, resulting in shorter ignition delay and lift-off compared to the first injection. However, soot production behaves differently with different injection strategies. The maximum instantaneous soot mass produced by the second injection increases with a shorter dwell time and with longer first injection duration.The author(s) disclosed receipt of the following financial support for the research, authorship, and/or publication of this article: This study was partially funded by the Spanish Ministry of Economy and Competitiveness in the frame of the advanced spray combustion models for efficient powertrains (COMEFF) (TRA2014-59483-R) project. Funding for Tiemin Xuan's PhD studies was granted by Universitat Politecnica de Valencia through the Programa de Apoyo para la Investigacion y Desarrollo (PAID) (grant reference FPI-2015-S2-1068)Desantes, J.; García-Oliver, JM.; García Martínez, A.; Xuan, T. (2019). Optical study on characteristics of non-reacting and reacting diesel spray with different strategies of split injection. International Journal of Engine Research. 20(6):606-623. https://doi.org/10.1177/1468087418773012S606623206Arrègle, J., Pastor, J. V., López, J. J., & García, A. (2008). Insights on postinjection-associated soot emissions in direct injection diesel engines. Combustion and Flame, 154(3), 448-461. doi:10.1016/j.combustflame.2008.04.021Mendez, S., & Thirouard, B. (2008). Using Multiple Injection Strategies in Diesel Combustion: Potential to Improve Emissions, Noise and Fuel Economy Trade-Off in Low CR Engines. SAE International Journal of Fuels and Lubricants, 1(1), 662-674. doi:10.4271/2008-01-1329He, Z., Xuan, T., Jiang, Z., & Yan, Y. (2013). Study on effect of fuel injection strategy on combustion noise and exhaust emission of diesel engine. Thermal Science, 17(1), 81-90. doi:10.2298/tsci120603159hKook, S., Pickett, L. M., & Musculus, M. P. B. (2009). Influence of Diesel Injection Parameters on End-of-Injection Liquid Length Recession. SAE International Journal of Engines, 2(1), 1194-1210. doi:10.4271/2009-01-1356Musculus, M. P. B., & Kattke, K. (2009). Entrainment Waves in Diesel Jets. SAE International Journal of Engines, 2(1), 1170-1193. doi:10.4271/2009-01-1355O’Connor, J., Musculus, M. P. B., & Pickett, L. M. (2016). Effect of post injections on mixture preparation and unburned hydrocarbon emissions in a heavy-duty diesel engine. Combustion and Flame, 170, 111-123. doi:10.1016/j.combustflame.2016.03.031O’Connor, J., & Musculus, M. (2013). Post Injections for Soot Reduction in Diesel Engines: A Review of Current Understanding. SAE International Journal of Engines, 6(1), 400-421. doi:10.4271/2013-01-0917O’Connor, J., & Musculus, M. (2014). In-Cylinder Mechanisms of Soot Reduction by Close-Coupled Post-Injections as Revealed by Imaging of Soot Luminosity and Planar Laser-Induced Soot Incandescence in a Heavy-Duty Diesel Engine. SAE International Journal of Engines, 7(2), 673-693. doi:10.4271/2014-01-1255Bruneaux, G., & Maligne, D. (2009). Study of the Mixing and Combustion Processes of Consecutive Short Double Diesel Injections. SAE International Journal of Engines, 2(1), 1151-1169. doi:10.4271/2009-01-1352Pickett, L. M., Kook, S., & Williams, T. C. (2009). Transient Liquid Penetration of Early-Injection Diesel Sprays. SAE International Journal of Engines, 2(1), 785-804. doi:10.4271/2009-01-0839Skeen, S., Manin, J., & Pickett, L. M. (2015). Visualization of Ignition Processes in High-Pressure Sprays with Multiple Injections of n-Dodecane. SAE International Journal of Engines, 8(2), 696-715. doi:10.4271/2015-01-0799Bolla, M., Chishty, M. A., Hawkes, E. R., & Kook, S. (2017). Modeling combustion under engine combustion network Spray A conditions with multiple injections using the transported probability density function method. International Journal of Engine Research, 18(1-2), 6-14. doi:10.1177/1468087416689174Blomberg, C. K., Zeugin, L., Pandurangi, S. S., Bolla, M., Boulouchos, K., & Wright, Y. M. (2016). Modeling Split Injections of ECN «Spray A» Using a Conditional Moment Closure Combustion Model with RANS and LES. SAE International Journal of Engines, 9(4), 2107-2119. doi:10.4271/2016-01-2237Cung, K., Moiz, A., Johnson, J., Lee, S.-Y., Kweon, C.-B., & Montanaro, A. (2015). Spray–combustion interaction mechanism of multiple-injection under diesel engine conditions. Proceedings of the Combustion Institute, 35(3), 3061-3068. doi:10.1016/j.proci.2014.07.054Moiz, A. A., Cung, K. D., & Lee, S.-Y. (2017). Simultaneous Schlieren–PLIF Studies for Ignition and Soot Luminosity Visualization With Close-Coupled High-Pressure Double Injections of n-Dodecane. Journal of Energy Resources Technology, 139(1). doi:10.1115/1.4035071Maes, N., Bakker, P. C., Dam, N., & Somers, B. (2017). Transient Flame Development in a Constant-Volume Vessel Using a Split-Scheme Injection Strategy. SAE International Journal of Fuels and Lubricants, 10(2), 318-327. doi:10.4271/2017-01-0815Moiz, A. A., Ameen, M. M., Lee, S.-Y., & Som, S. (2016). Study of soot production for double injections of n-dodecane in CI engine-like conditions. Combustion and Flame, 173, 123-131. doi:10.1016/j.combustflame.2016.08.005PASTOR, J., JAVIERLOPEZ, J., GARCIA, J., & PASTOR, J. (2008). A 1D model for the description of mixing-controlled inert diesel sprays. Fuel, 87(13-14), 2871-2885. doi:10.1016/j.fuel.2008.04.017Desantes, J. M., Pastor, J. V., García-Oliver, J. M., & Pastor, J. M. (2009). A 1D model for the description of mixing-controlled reacting diesel sprays. Combustion and Flame, 156(1), 234-249. doi:10.1016/j.combustflame.2008.10.008Pastor, J., Garcia-Oliver, J. M., Garcia, A., Zhong, W., Micó, C., & Xuan, T. (2017). An Experimental Study on Diesel Spray Injection into a Non-Quiescent Chamber. SAE International Journal of Fuels and Lubricants, 10(2), 394-406. doi:10.4271/2017-01-0850Settles, G. S. (2001). Schlieren and Shadowgraph Techniques. doi:10.1007/978-3-642-56640-0Pastor, J. V., Payri, R., Garcia-Oliver, J. M., & Briceño, F. J. (2013). Schlieren Methodology for the Analysis of Transient Diesel Flame Evolution. SAE International Journal of Engines, 6(3), 1661-1676. doi:10.4271/2013-24-0041Pastor, J. V., Garcia-Oliver, J. M., Novella, R., & Xuan, T. (2015). Soot Quantification of Single-Hole Diesel Sprays by Means of Extinction Imaging. SAE International Journal of Engines, 8(5), 2068-2077. doi:10.4271/2015-24-2417Pickett, L. M., & Siebers, D. L. (2004). Soot in diesel fuel jets: effects of ambient temperature, ambient density, and injection pressure. Combustion and Flame, 138(1-2), 114-135. doi:10.1016/j.combustflame.2004.04.006Ko¨ylu¨, U. O., & Faeth, G. M. (1994). Optical Properties of Overfire Soot in Buoyant Turbulent Diffusion Flames at Long Residence Times. Journal of Heat Transfer, 116(1), 152-159. doi:10.1115/1.2910849Manin, J., Pickett, L. M., & Skeen, S. A. (2013). Two-Color Diffused Back-Illumination Imaging as a Diagnostic for Time-Resolved Soot Measurements in Reacting Sprays. SAE International Journal of Engines, 6(4), 1908-1921. doi:10.4271/2013-01-2548Choi, M. Y., Mulholland, G. W., Hamins, A., & Kashiwagi, T. (1995). Comparisons of the soot volume fraction using gravimetric and light extinction techniques. Combustion and Flame, 102(1-2), 161-169. doi:10.1016/0010-2180(94)00282-wKnox, B. W., & Genzale, C. L. (2015). Reduced-order numerical model for transient reacting diesel sprays with detailed kinetics. International Journal of Engine Research, 17(3), 261-279. doi:10.1177/1468087415570765Burke, S. P., & Schumann, T. E. W. (1928). Diffusion Flames. Industrial & Engineering Chemistry, 20(10), 998-1004. doi:10.1021/ie50226a005Desantes, J. M., García-Oliver, J. M., Xuan, T., & Vera-Tudela, W. (2017). A study on tip penetration velocity and radial expansion of reacting diesel sprays with different fuels. Fuel, 207, 323-335. doi:10.1016/j.fuel.2017.06.108Nerva, J.-G. (s. f.). An Assessment of fuel physical and chemical properties in the combustion of a Diesel spray. doi:10.4995/thesis/10251/29767Payri, R., Salvador, F. J., Gimeno, J., & Bracho, G. (2008). A NEW METHODOLOGY FOR CORRECTING THE SIGNAL CUMULATIVE PHENOMENON ON INJECTION RATE MEASUREMENTS. Experimental Techniques, 32(1), 46-49. doi:10.1111/j.1747-1567.2007.00188.xPayri, R., Gimeno, J., Novella, R., & Bracho, G. (2016). On the rate of injection modeling applied to direct injection compression ignition engines. International Journal of Engine Research, 17(10), 1015-1030. doi:10.1177/1468087416636281Malbec, L.-M., Eagle, W. E., Musculus, M. P. B., & Schihl, P. (2015). Influence of Injection Duration and Ambient Temperature on the Ignition Delay in a 2.34L Optical Diesel Engine. SAE International Journal of Engines, 9(1), 47-70. doi:10.4271/2015-01-1830Payri, R., García-Oliver, J. M., Xuan, T., & Bardi, M. (2015). A study on diesel spray tip penetration and radial expansion under reacting conditions. Applied Thermal Engineering, 90, 619-629. doi:10.1016/j.applthermaleng.2015.07.042Knox, B. W., & Genzale, C. L. (2017). Scaling combustion recession after end of injection in diesel sprays. Combustion and Flame, 177, 24-36. doi:10.1016/j.combustflame.2016.11.021García-Oliver, J. M., Malbec, L.-M., Toda, H. B., & Bruneaux, G. (2017). A study on the interaction between local flow and flame structure for mixing-controlled Diesel sprays. Combustion and Flame, 179, 157-171. doi:10.1016/j.combustflame.2017.01.02

Optimization of spray break-up CFD simulations by combining Sigma-Y Eulerian atomization model with a response surface methodology under diesel engine-like conditions (ECN Spray A)

[EN] This work evaluates the performance of the Sigma-Y Eulerian atomization model at reproducing the internal structure of a diesel spray with a special focus on Sauter Mean Diameter (SMD) predictions. Modeling results have been compared to x-ray radiography measurements [21,24,38] which provided unique data within dense spray region. The first step corresponds to accurately reproduce the large scale spray dispersion. Among different RANS turbulence models, the standard k-s with the round jet corrected CIE value (1.60), has shown the best performance, as shown in [12]. Then, the study is devoted to the application and optimization of the predicted interphase surface density (E). In this work, a combination of CFD modeling and the statistical Design of Experiments (DOE) technique known as Response Surface Method (RSM) is applied in order to improve Sauter Mean Diameter (SMD) predictions from E equation compared to experimental measurements. In the investigation, two different optimizations are conducted for the three modeling parameters involved in the equation, following a Central Composite Design (CCD), leading to 15 simulations for each one. After that, both optimum sets of values are validated to assure the accuracy of the method and it is decided the best choice. Finally, different injection and ambient conditions are simulated, with those selected values, providing a remarkable improvement in the modeling performance.Authors acknowledge that part of this work was possible thanks to the Programa de Ayudas de Investigacion y Desarrollo (PAID 2013 3198) of the Universitat Politecnica de Valencia. Also this study was partially funded by the Spanish Ministry of Economy and Competitiveness in the frame of the COMEFF (TRA2014-59483R) project.Pandal-Blanco, A.; Payri, R.; García-Oliver, JM.; Pastor Enguídanos, JM. (2017). Optimization of spray break-up CFD simulations by combining Sigma-Y Eulerian atomization model with a response surface methodology under diesel engine-like conditions (ECN Spray A). Computers & Fluids. 156:9-20. doi:10.1016/j.compfluid.2017.06.022S92015

An Experimental Study on Diesel Spray Injection into a Non-Quiescent Chamber

[EN] Visualization of single-hole nozzles into quiescent ambient has been used extensively in the literature to characterize spray mixing and combustion. However in-cylinder flow may have some meaningful impact on the spray evolution. In the present work, visualization of direct diesel injection spray under both non-reacting and reacting operating conditions was conducted in an optically accessible two-stroke engine equipped with a single-hole injector. Two different high-speed imaging techniques, Schlieren and UV-Light Absorption, were applied here to quantify vapor penetration for non-reacting spray. Meanwhile, Mie-scattering was used to measure the liquid length. As for reacting conditions, Schlieren and OH* chemiluminescence were simultaneously applied to obtain the spray tip penetration and flame lift-off length under the same TDC density and temperature. Additionally, PIV was used to characterize in-cylinder flow motion. Results were compared with those from the Engine Combustion Network database obtained under quiescent ambient conditions in a high pressure high temperature vessel. Because of the air flow induced by piston movement, in-cylinder conditions in the two-stroke engine during the spray injection are highly unsteady, which has a significant impact on the spray development and interference on the spray visualization. From the comparison with quiescent data from the Engine Combustion Network, air flow induced by piston movement was found to slow down tip penetration. Moreover, both ignition delay and lift-off length under unsteady flow conditions show less sensitivity with ambient temperature than that of quasi-steady conditions.This work was partially funded by the Government of Spain through COMEFF Project (TRA2014-59483-R). In addition, the authors acknowledge that some equipment used in this work has been partially supported by FEDER project funds (FEDER-ICTS-2012-06), framed in the operational program of unique scientific and technical infrastructure of the Ministry of Science and Innovation of Spain. The authors want also to express their gratitude to CONVERGENT SCIENCE Inc for their kind support for this research.Pastor, JV.; García-Oliver, JM.; García Martínez, A.; Zhong, W.; Micó Reche, C.; Xuan, T. (2017). An Experimental Study on Diesel Spray Injection into a Non-Quiescent Chamber. SAE International Journal of Fuel and Lubricants. 10(2):1-13. https://doi.org/10.4271/2017-01-0850S11310

Application of a one-dimensional spray model to teach diffusion flame fundamentals for engineering students

[EN] This study presents the application of an existing interactive application for teaching spray dynamics in engineering degrees. The model is based on spray momentum conservation and can be used to evaluate both fuel-air mixing characteristics in inert conditions as well as diffusion flame performance once combustion takes place. During a dedicated computer-lab session, the students perform parametric studies regarding the influence of the nozzle outlet diameter, the combustion chamber density and the spray cone opening angle on the mixing process, characterized by the maximum stoichiometric length. Later on, the effect of the combustion reaction on the mixing field is evaluated. The results are analyzed taking as a reference to the theoretical development made by Spalding and Schlichting for diffusion gas jets. The outcomes of several years using this technique are reported.García-Oliver, JM.; García Martínez, A.; De La Morena, J.; Monsalve-Serrano, J. (2019). Application of a one-dimensional spray model to teach diffusion flame fundamentals for engineering students. Computer Applications in Engineering Education. 27(5):1202-1216. https://doi.org/10.1002/cae.22146S12021216275Aleiferis, P. G., Behringer, M. K., & Malcolm, J. S. (2016). Integral Length Scales and Time Scales of Turbulence in an Optical Spark-Ignition Engine. Flow, Turbulence and Combustion, 98(2), 523-577. doi:10.1007/s10494-016-9775-9Battin-Leclerc, F. (2008). Detailed chemical kinetic models for the low-temperature combustion of hydrocarbons with application to gasoline and diesel fuel surrogates. Progress in Energy and Combustion Science, 34(4), 440-498. doi:10.1016/j.pecs.2007.10.002Burke, R. D., De Jonge, N., Avola, C., & Forte, B. (2017). A virtual engine laboratory for teaching powertrain engineering. Computer Applications in Engineering Education, 25(6), 948-960. doi:10.1002/cae.21847Desantes, J. M., Pastor, J. V., García-Oliver, J. M., & Briceño, F. J. (2014). An experimental analysis on the evolution of the transient tip penetration in reacting Diesel sprays. Combustion and Flame, 161(8), 2137-2150. doi:10.1016/j.combustflame.2014.01.022Desantes, J. M., Pastor, J. V., García-Oliver, J. M., & Pastor, J. M. (2009). A 1D model for the description of mixing-controlled reacting diesel sprays. Combustion and Flame, 156(1), 234-249. doi:10.1016/j.combustflame.2008.10.008Dumouchel, C., Cousin, J., & Triballier, K. (2005). On the role of the liquid flow characteristics on low-Weber-number atomization processes. Experiments in Fluids, 38(5), 637-647. doi:10.1007/s00348-005-0944-1Edmonds, E. (1980). Where Next in Computer Aided Learning? British Journal of Educational Technology, 11(2), 97-104. doi:10.1111/j.1467-8535.1980.tb00396.xFansler, T. D., & Parrish, S. E. (2014). Spray measurement technology: a review. Measurement Science and Technology, 26(1), 012002. doi:10.1088/0957-0233/26/1/012002Gutiérrez-Romero, J. E., Zamora-Parra, B., & Esteve-Pérez, J. A. (2016). Acquisition of offshore engineering design skills on naval architecture master courses through potential flow CFD tools. Computer Applications in Engineering Education, 25(1), 48-61. doi:10.1002/cae.21778IPCC. Intergovernmental Panel on Climate Change Working Group I. Climate Change 2013: The Physical Science Basis.Long‐term Climate Change: Projections Commitments and Irreversibility  Cambridge University Press New York NY  2013:1029–136.https://doi.org/10.1017/CBO9781107415324.024W. Kirchstetter, T., Harley, R. A., Kreisberg, N. M., Stolzenburg, M. R., & Hering, S. V. (1999). On-road measurement of fine particle and nitrogen oxide emissions from light- and heavy-duty motor vehicles. Atmospheric Environment, 33(18), 2955-2968. doi:10.1016/s1352-2310(99)00089-8K. BenNaceur L.Cozzi andT.Gould.World Energy Outlook 2016.2016.https://doi.org/10.1787/weo‐2016‐enM.Nesbitet al. Comparative Study on the differences between the EU and US legislation on emissions in the automotive sector.2016.PASTOR, J., JAVIERLOPEZ, J., GARCIA, J., & PASTOR, J. (2008). A 1D model for the description of mixing-controlled inert diesel sprays. Fuel, 87(13-14), 2871-2885. doi:10.1016/j.fuel.2008.04.017PAYRI, R., GARCIA, J., SALVADOR, F., & GIMENO, J. (2005). Using spray momentum flux measurements to understand the influence of diesel nozzle geometry on spray characteristics. Fuel, 84(5), 551-561. doi:10.1016/j.fuel.2004.10.009Payri, R., Salvador, F. J., Gimeno, J., & Novella, R. (2011). Flow regime effects on non-cavitating injection nozzles over spray behavior. International Journal of Heat and Fluid Flow, 32(1), 273-284. doi:10.1016/j.ijheatfluidflow.2010.10.001Perumal, K., & Ganesan, R. (2015). CFD modeling for the estimation of pressure loss coefficients of pipe fittings: An undergraduate project. Computer Applications in Engineering Education, 24(2), 180-185. doi:10.1002/cae.21695Regueiro, A., Patiño, D., Míguez, C., & Cuevas, M. (2017). A practice for engineering students based on the control and monitoring an experimental biomass combustor using labview. Computer Applications in Engineering Education, 25(3), 392-403. doi:10.1002/cae.21806Sick, V., Drake, M. C., & Fansler, T. D. (2010). High-speed imaging for direct-injection gasoline engine research and development. Experiments in Fluids, 49(4), 937-947. doi:10.1007/s00348-010-0891-3SPALDING, D. B. (1979). The stability of steady exothermic chemical reactions in simple non-adiabatic systems. Combustion and Mass Transfer, 399-406. doi:10.1016/b978-0-08-022106-9.50025-5Weilenmann, M., Soltic, P., Saxer, C., Forss, A.-M., & Heeb, N. (2005). Regulated and nonregulated diesel and gasoline cold start emissions at different temperatures. Atmospheric Environment, 39(13), 2433-2441. doi:10.1016/j.atmosenv.2004.03.081www.upv.es. Universitat Politècnica de València.Zhao, H., & Ladommatos, N. (1998). Optical diagnostics for soot and temperature measurement in diesel engines. Progress in Energy and Combustion Science, 24(3), 221-255. doi:10.1016/s0360-1285(97)00033-

In-flame soot quantification of diesel sprays under sooting/non-sooting critical conditions in an optical engine

[EN] Because of the challenge of meeting stringent emissions regulations for internal combustion engines, some advanced low temperature combustion modes have been raised in recent decades to improve combustion efficiency. Therefore, detailed understanding and capability for accurate prediction of in-flame soot processes under such low sooting conditions are becoming necessary. Nowadays, a lot of investigations have been carried out to quantify in-flame soot in Diesel sprays under high sooting conditions by means of different optical techniques. However, no information of soot quantification can be found for sooting/non-sooting critical conditions. In current study, the instantaneous soot production in a two-stroke optical engine under low sooting conditions has been measured by means of a Diffused back-illumination extinction technique (DBI) and two-color method (2C) simultaneously. The fuels used were n-dodecane and n-heptane, which have been injected separately though two different injectors equipped with single-hole nozzles. A large cycle-to-cycle variation on soot production can be observed under such operating conditions, however the in-cylinder heat release traces were quite repeatable. It is the same with the well-known trends of soot amount to operating conditions that the probability of sooting cycles increases with higher ambient temperature, higher ambient density and lower injection pressure. Both techniques present a pretty good agreement on soot amount when the peak of KL value is close to 1. However, the KL value of two-color method becomes bigger than that of DBI and the difference increases with lower sooting conditions.This study was partially funded by the Natural Science Foundation of China (No. 51876083), China Postdoctoral Science Foundation (2018M642176) and High-tech Research Key laboratory of Zhenjiang (SS2018002)Xuan, T.; Pastor, JV.; García-Oliver, JM.; García Martínez, A.; He, Z.; Wang, Q.; Reyes, M. (2019). In-flame soot quantification of diesel sprays under sooting/non-sooting critical conditions in an optical engine. Applied Thermal Engineering. 149:1-10. https://doi.org/10.1016/j.applthermaleng.2018.11.112S11014