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A simplified model for a diesel spray
Abstract
This paper describes a computer simulation and measurements of the liquid phase of Diesel spray formation.
The spray is divided into small elementary volumes in which the amounts of liquid and gaseous fuel, air, mean, maximum and minimum fuel droplet diameter are calculated, as well as their number. The total air–fuel and air–fuel vapour ratios are calculated for each elementary volume. The mathematical model of the Diesel spray is based on continuity and momentum equations in Eulerian-Lagrangian formulation.
The measurements of the sprays were carried out in the combustion chamber at the LTT, which is equipped with a high pressure 250 MPa fuel injection system. During the experiments, ambient pressure varied from 3 MPa to 7 MPa, temperature from 673 K to 973 K, injection pressure from 40 MPa to 200 MPa and nozzle temperature from 243 K to 363 K. The injection quantity was 13.5 mm³ per cycle in all cases. The combustion chamber was filled with pure nitrogen instead of air. Thermodynamic properties of nitrogen are similar to those of air. That way, self-ignition was prevented. We measured only the liquid phase of the fuel in the spray, and to this end, Mie scattering measuring technique was applied.
The comparison between the simulated and actual liquid spray penetration depth and spray cone angle showed good matching.
... SMD analysis showed that the smallest drops were obtained with a mixture of diesel oil and methyl laurate. The authors of [6] validated the computer analysis of the fuel atomization process in the combustion chamber. The mathematical model of the fuel injection process in the combustion chamber was developed based on the Euler-Lagrange equations. ...
This article presents the authors’ considerations regarding the possibilities of developing fuel equipment for modern compression ignition engines used in special and non-road vehicles. The paper discusses the process of fuel combustion and atomization in the chamber of a piston combustion engine. The paper then presents the concept of modifying the atomizer of a modern fuel injector for operation using hydrogen-containing fuels of plant origin. The authors present a review of tests performed using an engine dynamometer on a modern engine with a Common Rail system running on biofuel. The CI engine operated with standard and modified fuel injectors. During the tests, the external ecological characteristics of the engine were analyzed as a function of rotational speed; the values of injection doses at individual rotational speeds and their effects on the characteristics were read from the current parameters, and the pressure and temperature in the engine’s combustion chamber were measured. The research results show that implementing the changes proposed by the authors of this work is a good direction for the development of compression ignition engines.
... Recording images inside a cylinder of an internal combustion engine can be difficult mainly due to high temperature and pressure, limited access to a cylinder and a very dynamic nature of recorded phenomena [20]. However, optical techniques are becoming increasingly popular, as evidenced by research using fixed-volume chambers in universities and R&D centers in China [21], Spain [22,23], or by simulation studies conducted in research centers in Korea and the USA [24], and Germany and Slovenia [25]. ...
This paper presents the research results for a diesel and hydrogen fueled engine. The research object is a four-cylinder, four-stroke ADCR engine with a displacement of 2,636 cm3. In the experiments, glow plugs were replaced with compressed hydrogen injectors and a special adapter. Hydrogen was supplied directly into a combustion chamber using a test injector. A hydrogen dose in the tests was changed at selected test points and ranged from 0 to 160 dm3/min. The research were conducted at 1,500 rpm. A hydrogen injection start angle and maximum hydrogen dose were specified from the preliminary experiments. The following parameters were analyzed: indicated mean effective pressure, maximum pressure, crank angle of maximum cylinder pressure occurrence and heat release. The obtained results were statistically analyzed. The conducted analysis focused on determining whether there are significant differences between early and late injection and how these changes affect the measured parameters.
... A simplified model for a Diesel fuel spray described in [124] is based on the same continuity and momentum equations as the model described above based on [174]. Good agreement between predicted and observed liquid spray penetration and cone angle were demonstrated by these authors. ...
Conventional understanding of spray formation when liquid leaves the nozzle is based on the analysis of the following stages: development of the jet, conversion of the jet into liquid sheets and ligaments, disintegration of ligaments into relatively large droplets (primary break-up) and break-up of large droplets into smaller ones (secondary break-up). The following stages of spray formation are considered in this chapter: instability of a jet emerging from the nozzle, break-up of droplets and spray penetration considering and not considering the effect of turbulence. In the case of petrol direct injection engines, the development of sprays is typically accompanied by the formation of vortex ring-like structures. Some new approaches to modelling these structures, not including and including the effects of confinement, are described. The predicted velocities of displacement of the regions of maximal vorticity in typical petrol engines are compared with available experimental data where possible. The results of the investigation of two-phase vortex ring flows using the fully Lagrangian approach are presented.
... Registration of images inside the combustion engine cylinder meets with a number of difficulties, mainly related to high temperature and pressure, limited access to the cylinder and very high dynamics of recorded phenomena [7]. However, optical techniques are becoming more and more popular, as evidenced by studies using fixed volume chambers in universities and R&D centres in China [5], Spain [5,9] or simulation studies conducted in centres in Korea and the USA [6] or in Germany and Slovenia [10]. ...
The paper presents the research results of the injector construction with the modified injection nozzle. The injector is designed for a prototype opposed-piston aircraft diesel engine. The measurements were based on the Mie scattering technique. The conditions of the experiment corresponded to maximum loads similar to those occurring at the start. The measuring point was selected in line with the analysis of engine operating conditions: combustion chamber pressure at the moment of fuel delivery (6 MPa) and fuel pressure in the injection rail (140 MPa). The analysis focused on the average spray range and distribution, taking into account the differences between holes in the nozzle. As a result of the conducted research, the fuel spray range was defined with the determined parameters of injection. The fuel spray ranges inside the constant volume chamber at specific injection pressures and in the chamber were examined, and the
obtained results were used to verify and optimize the combustion process in the designed opposed-piston two-stroke engine.
... From the perspective of the physical phenomena of fuel spray and flame combustion, the injection pressure could have an important impact on the fuel spray configuration, the air entrainment in the cylinder, and the mixing of fuel and gas. Many visualization experiments on injection pressure have shown that the air entrainment intensity of fuel spray will be enhanced under higher injection pressure [14,15]. Especially under the ultra-high injection pressure with a high-pressure common rail system, the fuel-air mixing is greatly enhanced [16]. ...
In this paper, the visualization experiments of spray, ignition, and combustion of diesel under variable injection pressure (from 90 to 130 MPa) were studied by using a constant volume vessel and impinging combustion plate system. With the development of the down-sizing of diesel engines, the wall impinging combustion without liquid spray collision will be the research focus in the diesel engine combustion process. The flame natural luminosity in the experiment represents the soot formation of diesel combustion. Besides, the detailed information of diesel spray mixing combustion was obtained by using the CFD (Computational Fluid Dynamics) simulation of alternative fuels in CONVERGE™. The specific conclusions are as follows. The high velocity of the spray under the higher injection pressure could reduce the low-mixing area near the impinging wall by entraining more air. Under higher injection pressure in simulation, the gas diffused more extensively, and more heat was released after combustion. Therefore, a large amount of soot formed in the early stage of combustion and then oxidized in high-temperature regions, which agreed with the conclusions in the experiments. Under the influence of the superposition of image pixels of the flame, the change of soot generation with injection pressure is smaller than the actual value, so the visualization experiment can be used as the basis of combustion prediction.
... In this way, the spray tip penetration was predicted with respect to the ambient gas density changes. The model proposed by Mar ci c et al. 89 considered the spray in two limiting cases: the initial stage and the two-phase flow regime by dividing the spray into small elementary volumes. For each elementary volume, the liquid spray penetration, droplet diameter, fuel-air ratio was calculated based on the conservation equation of momentum and continuity. ...
Driven by the increasingly remarkable problems of environmental pollution and energy crisis, the combustion optimization of diesel engine seems to be more urgent than ever, therefore, advanced injection strategies are gradually proposed and employed in modern diesel engines. Phenomenological model, which serves as an effective tool to conduct the parametric study on the spray penetration, needs to be improved to fit the intensified injection condition. Since that there are no attempts to review the spray penetration model developments, in order to help to build a comprehensive understanding of diesel spray propagation, this article briefly summarized the early history and introduced the widely used classical and improved phenomenological spray penetration models. Besides, to provide a helpful reference for selection of suitable models, the modeling methods were analyzed and features and simulation of various models were discussed and compared. After that, the trend of modeling methods and promising directions for future spray modeling were suggested.
... Fuel injector is a device for spraying diesel fuel in a very fine scattering mist into the combustion chamber. Fuel Injection Pressure (IP) and fuel injection timing are the parameters that affect the engine performance, combustion, and emission significantly [9]. Also, the proper nozzle adjustment can reduce the density of exhaust gases and improve the engine performance [10]. ...
The use of diesel engines for vehicle applications has expanded for decades. However, it produces black smoke in the form of particulate matter contains fine and invisible particles during operation. The popular method for measuring the smoke opacity is by using a smoke meter for its simplicity and less costly. Fuel injection pressure is one of the parameters that affect the emission significantly, and the proper nozzle adjustment can reduce the density of exhaust gases and improve the engine performance. The purpose of this study is to determine the optimum fuel spray pressure that produces the lowest opacity value and analyze the effect of fuel spray pressure on the opacity value at a different engine speed. The present experiment uses the Hyundai D4BB engine, and the pressure variations were implemented on the injector nozzle at 125, 130, and 135 kg/cm2. The engine was also tested with various engine idle speed, i.e., 1000, 1500, 2000, and 2500 rpm. It has been found that the optimum distance of fuel spraying is 147.679 mm with injector nozzle pressure 130 kg/cm2, and the value of opacity is 9.51%.
... Thus, the CFD method is not suitable for the preliminary and robust analysis of spray development. Instead, some simplified spray models, like the quasi-dimensional model of Mrzljak et al. [20], the one-dimensional spray model of Cheng et al. [21], and the two-dimensional spray model of Marčiča et al. [22], have shown superiority in studying the spray characteristics. However it is a pity that those models didn't investigate the influence of various injection rate shapes on the spray characteristics, so a simplified diesel spray model with varying injection rate shape as the core, ignoring some complicated yet uninfluential factors, is still badly needed to study the mixing characteristics of diesel spraying. ...
Common rail systems have been widely used in diesel engines due to the stricter emission regulations. The advances in injector technology and ultrahigh injection pressure greatly promote the development of multiple-injection strategy, leading to the shorter injection duration and more variable injection rate shape, which makes the mixing process more significant for the formation of pollutant emission. In order to study the mixing process of diesel sprays under variable injection rate shapes and find the optimized injection strategy, a one-dimensional spray model was modified in this paper. The model was validated by the measured spray penetrations based on shadowgraphy experiments with the varying injection rate. The simulations were performed with five injection rate shapes, triangle, ramping-up, ramping-down, rectangle and trapezoid. Their spray penetrations, entrainment rates and equivalence ratios along spray axial distance are compared. The potentials of multiple-injection and gas-jet after end-of-injection (EOI) to improve mixing process and emission reduction are discussed finally. The results indicated that ramping-up injection rate obtains the highest entrainment rate after EOI, and it needs 1.5 times of injection duration for the entrainment wave to arrive at the spray tip. For the other four injection rates, the sprays can be treated as a steady-like state, needing twice of injection duration from EOI to the time the entrainment wave reaches the spray tip. The multiple-injection with proper injection rate shape enhanced the entrainment rate, and the gas-jet after EOI affected the mixture distribution and entrainment rate in spray tail under ramping-down injection rate.
En este trabajo se estudia aborda los métodos y diseños experimentales didácticos – investigativos usados para modelar el chorro líquido en motores de combustión interna Diésel y la validación de dichos modelos; además, busca conocer la tendencia actual en este campo. También, conocer los principios físicos y la tendencia tecnológica del proceso de inyección, con el fin de cimentar una base para futuros trabajos sobre el tema. Este acercamiento encontró que la tendencia actual es la de mejorar la combustión para producir menor materia contaminante, para así poder cumplir con las normativas vigentes, además se demostró que el modelado CFD es la herramienta más usada por los investigadores en el último año, debido a su relativo bajo costo y su precisión, en términos tecnológicos la inyección directa sigue siendo la opción más investigada y la cavitación presenta ahora un campo relativamente virgen de investigación debido a su complejidad, estas razones hacen a la cavitación un campo interesante de investigación, por otra parte el uso de bancos de inyección es la forma de validación más usada, debido a la facilidad para observar el proceso y controlar los distintos parámetros que gobiernan a la inyección, por otro lado los métodos ópticos son una opción interesantes para recoger datos debido a su exactitud.
The work substantiates the feasibility of manufacturing electrical equipment housings with variable curvature by shells expansion with explosion energy. The possibility of deformation of cylindrical shells during the explosion of a charge that is displaced relative to the axis of symmetry of the shell is considered. A calculation method and model that reflect the real picture of the pulsed deformation of a cylindrical workpiece are proposed. The developed mechanical-mathematical model allows us to consider the nature of the hardening of the material under pulsed action and the inertial components under high-speed loading.
In this study, the preferential evaporation behavior of diesel fuel is investigated using a discrete continuous multicomponent (DCMC) evaporation model. By analyzing real diesel fuel composition data from a 2D gas chromatography (GCxGC) measurement, 180 individual species from 11 different hydrocarbon families could be identified. To utilize these detailed composition data in the DCMC model, four continuous distribution functions for normal paraffins, mono-naphthenics, mono-aromatics, and naphthenic-mono-aromatics have been derived, which cover 80% of the total diesel composition. A specific property database for these hydrocarbon groups was established and suitable correlations were derived. The DCMC model was validated with experimental results of evaporating acoustically levitated single diesel droplets. Gas temperatures up to 200 °C were investigated, where the diesel fuel did not evaporate completely due to the presence of very long-chain compounds with low volatilities. The DCMC model using the experimentally-based diesel composition successfully captures this trend. To prove the importance of using the DCMC model with experimentally based fuel composition data at diesel engine conditions, a single droplet was exposed to a gas environment of 700 °C. Here, the diesel droplet showed the longest lifetime, while dodecane, which is commonly used in diesel surrogate mixtures, evaporated significantly faster.
This paper provides a study of injection process in a research compression ignition engine fueled with Rapeseed Methyl Ester pure biodiesel and its blends by advanced optical diagnostics and 1D model. Experimental tests have been performed in an optical direct injection single-cylinder engine equipped with the Common Rail injection system of a real compression ignition engine. The injection strategies consisted of two events per cycle, the pilot and the main. The investigated conditions were representative of two engine operating points of the WLTC corresponding to two different engine speed and brake mean effective pressure values. The 2D visible imaging and the novel infrared (IR) technique have been applied to evaluate fuel spray parameters (i.e. penetration and cone angle) for liquid and vapor phases, respectively. Experimental results have been compared to data obtained with commercial diesel fuel available from previous authors’ works, underlining the main differences. Furthermore, to improve biodiesel spray knowledge, 1D model for diesel jets has been suitably modified to analyze RME spray. The model has been set up via collected experimental data. Pure fuel and blends properties have been evaluated using REFPROP® software. Once the model has been validated, it has allowed to calculate the equivalence ratio along both the jet axis and radial direction, and the amount of vapor fuel over time. The modified 1D model presented in this study could be an advanced and effective instrument to study injection process in the modern engines fed with biofuel, supporting experimental activities in order to reduce time and costs.
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