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Artykuły w czasopismach na temat "Spray combustion environment"
1
Desantes, Jose M., Jose M. Garcia-Oliver, Ricardo Novella, and Leonardo Pachano. "A numerical study of the effect of nozzle diameter on diesel combustion ignition and flame stabilization." International Journal of Engine Research 21, no. 1 (2019): 101–21. http://dx.doi.org/10.1177/1468087419864203.
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The role of nozzle diameter on diesel combustion is studied by performing computational fluid dynamics calculations of Spray A and Spray D from the Engine Combustion Network. These are well-characterized single-hole sprays in a quiescent environment chamber with thermodynamic conditions representative of modern diesel engines. First, the inert spray evolution is described with the inclusion of the concept of mixing trajectories and local residence time into the analysis. Such concepts enable the quantification of the mixing rate, showing that it decreases with the increase in nozzle diameter. In a second step, the reacting spray evolution is studied focusing on the local heat release rate distribution during the auto-ignition sequence and the quasi-steady state. The capability of a well-mixed-based and a flamelet-based combustion model to predict diesel combustion is also assessed. On one hand, results show that turbulence–chemistry interaction has a profound effect on the description of the reacting spray evolution. On the other hand, the mixing rate, characterized in terms of the local residence time, drives the main changes introduced by the increase of the nozzle diameter when comparing Spray A and Spray D.
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Jafarmadar, Samad, Shram Khalilarya, Sina Shafee, and Ramin Barzegar. "Modeling the effect of spray/wall impingement on combustion process and emission of DI diesel engine." Thermal Science 13, no. 3 (2009): 23–33. http://dx.doi.org/10.2298/tsci0903023j.
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This work is presented to study the effect of spray impinging on the combustion process and emissions in a direct injection diesel engine at various engine speeds. Computations are carried out using a three-dimensional modeling for sprays, spray-wall interactions, flow field, emission, and combustion process. Results indicate an increase in engine speed leads to increased spray impinging (wall film formation), turbulence intensity and average wall temperature in cylinder. The enhanced air/fuel mixing and intensified evaporation of wall film decreases soot emission by reducing the extent of the fuel rich regions specially in impinging zones. Also at higher engine speeds, combustion is delayed and fuel is consumed in a shorter time period by the enhanced air and fuel mixing. The shorter combustion duration provides less available time for soot and NOx formations. However, only a few attempts have been made to address the effect of impingement of spray with piston walls on the emissions and combustion process. The results of model in addition to approving the corresponding data in the literature are also compared with the experimental data and shown good agreement.
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Arai, Masataka. "Interpretative Review of Diesel Spray Penetration Normalized by Length and Time of Breakup (Similarity Law of Diesel Spray and Its Application)." Energies 15, no. 13 (2022): 4926. http://dx.doi.org/10.3390/en15134926.
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Tip penetration of diesel spray is one of the most useful parameters to evaluate diesel combustion dynamics. It has strong relationships with ignition delay, premix/diffusion combustion and engine performance, including exhaust emissions. To discuss general combustion physics in various size sprays, non-dimensional expression of spray tip penetration is reviewed. Length and time of injected fuel jet breakup can be considered as characteristic length and timescale of diesel spray. Then, normalized penetration by length and time of breakup was proposed for the scaling of various diesel sprays. Using the proposed scaling method and similarity law, tip penetrations of various size sprays are collapsed into one simple expression. It becomes a base of similarity law of diesel spray. For example, local or average A/F is uniquely expressed by the normalized length and time of breakup. Penetration of a wall impingement spray is also expressed uniquely by this normalization method and physical parameters affecting the wall impingement spray are explained. Injection rate shaping effect at an initial stage of injection is clearly demonstrated by using this scaling. Further, mixing degrees of diesel spray at an ignition timing and in a combustion phase can be reasonably explained by the equivalence ratio change with non-dimensional elapsed time after injection start.
4
Liu, Yu, Jun Li, Ying Gao, and Xin Mei Yuan. "Laser Diagnostic Investigation on the Spray and Combustion with Butanol-Biodiesel-Diesel Fuel Blends." Advanced Materials Research 443-444 (January 2012): 986–95. http://dx.doi.org/10.4028/www.scientific.net/amr.443-444.986.
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. In this paper, blends of butanol-biodiesel-diesel were tested inside a constant volume chamber to investigate liquid spray and combustion of the fuels. With high-speed camera and synchronized copper vapor laser, spray penetration during injection is recorded since it has a higher light reflectivity. Various ambient temperatures and fuel composition were investigated. There is a sudden drop in spray penetration at 800 K and 900 K, but not at 1000 K and 1200 K. When the spray penetration of the butanol-biodiesel-diesel blends is compared to that of the biodiesel-diesel blends, under non-combusting environment, a sudden drop in spray penetration length is also observed at 1100 K. High speed imaging shows that, for the non-combusting case, at 1100 K, the tip of the spray jet erupts into a plume sometime after injection for the butanol-biodiesel-diesel blend. The same is not seen with the biodiesel-diesel blend, neither at lower ambient temperature of 900 K. It is concluded that micro-explosion can occurs under particular conditions for the butanol-biodiesel-diesel blend, and the results is consistent with previous study in the literature.
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Chung, Wai Tong, Peter C. Ma, and Matthias Ihme. "Examination of diesel spray combustion in supercritical ambient fluid using large-eddy simulations." International Journal of Engine Research 21, no. 1 (2019): 122–33. http://dx.doi.org/10.1177/1468087419868388.
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High-pressure conditions in diesel engines can often surpass the thermodynamic critical limit of the working fluid. Consequently, the injection of fuel at these conditions can lead to complex behaviors that remain only incompletely understood. This study is concerned with investigating the application of a diffuse-interface method in conjunction with a finite-rate chemistry model in large-eddy simulations of diesel spray injection and ignition in a supercritical ambient environment. The presented numerical approach offers the capability of simulating these complex conditions without the need for parameter tuning that is commonly employed in spray-breakup models. Numerical simulations of inert and reacting n-dodecane sprays — under the Engine Combustion Network Spray A and Spray D configurations — are studied, and results are compared with experimental data for liquid/vapor penetration lengths and ignition timing. In addition, parametric studies are performed to identify flow sensitivities arising from the variation in nozzle diameters between both injectors, along with the impact of low-temperature oxidation on ignition in Spray D simulations. Spray A simulations are found to be insensitive to turbulence, and predictions for penetration length and ignition behavior are in good agreement with experiments. In contrast, Spray D predictions for penetration length and ignition delay demonstrated significant sensitivities to in-nozzle turbulence, introducing uncertainty to the predicted results and stipulating the need for quantitative measurements for model evaluation.
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Xuan, Tiemin, Zhongcheng Sun, Peng Lu, et al. "Optical study on needle lift and its effects on reacting diesel sprays of a single-hole solenoid injector." Thermal Science, no. 00 (2020): 289. http://dx.doi.org/10.2298/tsci190925289x.
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Precise control of needle lift provides one possibility to control the Diesel spray and combustion process actively. However, most studies of needle lift focus on internal flow or near nozzle spray. Little work has been performed on its effects on reacting spray. In this work, one way to change the needle lift profile of a solenoid injector has been developed and the relationship between needle lift and reacting spray has been investigated. The needle movement was detected with an optical nozzle. In addition, the visualization of reacting sprays of the same injector equipped with a single-hole nozzle was conducted in a combustion chamber. Some simulations were also performed to assist the analysis. The results show that the needle lift profile can be regulated by changing the thickness of an adjusting pad. It seems the different needle lift profiles do not bring in significant influences on reacting spray characteristics. The CFD results indicate that it is mainly caused by the similar internal flow characteristics which do not show strong variation when needle lift is higher than 0.1 mm. However, the discharge coefficient and velocity coefficient decrease sharply when needle lift is smaller than 0.05 mm because of the ?throttle? effect.
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Luo, Meng, Pingping Zhu, Usman Rana, Hu Ma, Zhendong Yu, and Oskar J. Haidn. "Modeling Investigation of Liquid Oxygen Flashing Spray with CFD." Journal of Physics: Conference Series 2235, no. 1 (2022): 012061. http://dx.doi.org/10.1088/1742-6596/2235/1/012061.
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Abstract Injection of cryogenic propellants (e.g. liquid oxygen) into low-pressure environment (e.g. upper-stage rocket engine) may trigger flashing phenomenon, which severely affects the propellants’ mixing and combustion. In order to unveil the characteristics of flashing sprays, numerical models of flashing sprays were developed and validated. First, a developed model based on Adachi-correlation was employed for the flashing spray simulation. The results show good agreements with the experiments, both for the flashing spray morphology and temperature distribution. In the near-injector region, the flashing evaporation dominates the spray vaporization with the evaporation mass flow rate of about 2 orders of magnitude higher than that by the other heat transfers, whereas downstream the injector, the external heat transfer (i.e. heat conduction and convection) does. Furthermore, a new flashing spray model based on the nucleate boiling theory was proposed, which shows an improved agreement of the droplet temperature between the simulation and test data.
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Li, Zhijie, Jie Pan, Wei Li, Xiangting Wang, Haiqiao Wei, and Jiaying Pan. "New Insights into Abnormal Combustion Phenomena Induced by Diesel Spray-Wall Impingement under Engine-Relevant Conditions." Energies 15, no. 8 (2022): 2941. http://dx.doi.org/10.3390/en15082941.
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High altitude and low temperature is the common extreme environment for internal combustion engines. Under such operating conditions, heavy-duty diesel engines often suffer from serious abnormal combustion, such as knocking combustion, which results in piston crown breakdown and cylinder head erosion. Spray-wall impingement and pool fires are considered potential causes; however, the detailed mechanism remains poorly understood owing to the lack of research data. In this study, for the first time, the destructive abnormal combustion induced by diesel spray-wall impingement was identified using an optical rapid compression machine under engine-relevant conditions at high altitudes. Combining instantaneous pressure and temperature measurements with simultaneously recorded high-speed photography gives useful insights into understanding the detailed combustion processes. The experimental results show that depending on the extent of diesel spray-wall impingement, supersonic detonation-like reaction fronts featuring bright luminosity can be observed. The propagation of these reaction fronts in-cylinder results in severe pressure oscillations with an amplitude approaching hundreds of atmospheres, which is like the super-knock events in boosted direct-injection spark-ignition engines. Further parametric analysis indicates that the interplay between the diffusion combustion controlled by diesel spray and the premixed combustion dominated by attached film evaporation results in the formation of abnormal combustion. Destructive reaction fronts tend to occur at a prolonged ignition delay time, which facilitates the mixing between diesel evaporation and hot air.
9
Raghu, P., K. Thilagan, M. Thirumoorthy, Siddharth Lokachari, and N. Nallusamy. "Spray Characteristics of Diesel and Biodiesel in Direct Injection Diesel Engine." Advanced Materials Research 768 (September 2013): 173–79. http://dx.doi.org/10.4028/www.scientific.net/amr.768.173.
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Alternative fuels for diesel engines are becoming important due to the decrease of petroleum reservoirs and the increase of environment pollution problems. The biodiesel is technically competitive with conventional petroleum-derived diesel fuel and requires no changes in the fuel distribution system. Injection process of biodiesel influences the atomization and dispersion of fuel in the combustion chamber. In diesel Engine different tests have been performed to improve the efficiency in cycle, power, less emission, speed, etc. There are various methods of visualizing the combustion chamber in a Diesel engine. For visualizing spray characteristics of combustion chamber in Diesel engine the window of 10mm diameter hole, transparent quartz glass materials are used, which can with-stand 1500°C temperature and pressure of about 1000 bar and engine is hand cranked for conducting the experiments. Spray characteristics of palm oil methyl ester (POME) and diesel were studied experimentally. Spray penetration and spray angle were measured in a combustion chamber of DI diesel engine by employing high definition video camera and image processing technique. The study shows the POME gives longer spray tip penetration and spray angle are smaller than those of diesel fuels. This is due to the viscosity and density of biodiesel.
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Duronio, Francesco, Angelo De De Vita, Alessandro Montanaro, and Luigi Allocca. "Experimental Investigation and Numerical CFD Assessment of a Thermodynamic Breakup Model for Superheated Sprays with Injection Pressure up to 700 Bar." Fluids 8, no. 5 (2023): 155. http://dx.doi.org/10.3390/fluids8050155.
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Among the most relevant fields of research recently investigated for improving the performance of gasoline direct injection (GDI) engines, there are ultrahigh injection pressures and the flash-boiling phenomenon. Both perform relevant roles in improving the air/fuel mixing process, reducing tailpipe emissions and implementing new combustion methods. When a high-temperature fuel is released into an environment with a pressure lower than the fuel’s saturation pressure, flash boiling occurs. Due to complex two-phase flow dynamics and quick droplet vaporization, flash boiling can significantly modify spray formation. Specifically, if properly controlled, flash boiling produces important benefits for the fuel–air mixture formation, the combustion quality and, in general, for overall engine operation. Flash boiling was broadly investigated for classical injection pressure, but few works concern ultrahigh injection pressure. Here, the investigation of the spray produced by a multihole injector was performed using both experimental imaging techniques and CFD simulations aiming to highlight the combined impact of the injection pressure and the flash boiling occurrence on the spray morphology. The shadowgraph method was employed to observe the spray experimentally. The information gathered allows for assessing the performances of an Eulerian–Lagrangian algorithm purposely developed. Breakup and evaporation models, appropriate for flashing sprays, were implemented in a CFD (Computational Fluid Dynamics) code. The experimental results and the CFD simulations demonstrate a good agreement, demonstrating that through adoption of a flash-boiling breakup model, it is possible to reproduce non-evaporating and superheated sprays while changing few simulation parameters. Finally, the results also show the significance of injection pressure in preventing spray collapse.