Liquid Film Atomization on Wall Edges—Separation Criterion and Droplets Formation Model

2002 ◽  
Vol 124 (3) ◽  
pp. 565-575 ◽  
Author(s):  
F. Maroteaux ◽  
D. Llory ◽  
J-F. Le Coz ◽  
C. Habchi
Keyword(s):  
Liquid Film ◽  
Fuel Injection ◽  
Liquid Sheet ◽  
Operating Conditions ◽  
Spark Ignition Engine ◽  
Physical Parameters ◽  
Lagrangian Description ◽  
Fuel Film ◽  
Separation Criterion ◽  
Film Separation

In order to predict the fuel mixture preparation inside the cylinder of port fuel injection engines, a model for the aerodynamic stripping of the fuel film deposited on the manifold walls is discussed, and a model for the fuel film separation and atomization near the sharp edges is developed. A separation criterion is set up using an analogy with Rayleigh-Taylor instabilities driven by the inertial forces of the liquid film. To determine the physical parameters of the resulting droplets, a liquid sheet atomization scheme is used. The critical value for the separation criterion is adjusted using experimental data obtained in 2D wind tunnel equipped with different steps shaped as a valve seat, and reproducing the main characteristics of the intake of spark ignition engine. CFD simulations are performed using the KMB code, a modified version of KIVA-2 already including a stochastic Lagrangian description of the spray, and an Eulerian liquid film model. Computations results for different operating conditions are in good agreement with the images of film separation and measured droplet size distributions.

Potential of inertial instabilities for fuel film separation in port fuel injection engine conditions

2003 ◽  
Vol 4 (1) ◽  
pp. 11-26 ◽  
Author(s):  
F Maroteaux ◽  
D Llory ◽  
J-F le Coz ◽  
C Habchi
Keyword(s):  
Fuel Injection ◽  
Fuel Mixture ◽  
Spark Ignition Engine ◽  
Lagrangian Description ◽  
Fuel Film ◽  
Separation Criterion ◽  
Fuel Droplets ◽  
Port Fuel Injection ◽  
Intake Stroke ◽  
Film Separation

In port fuel injection engines, the liquid fuel film accumulated in the vicinity of intake valves is torn away and goes into the cylinder during the intake phase. In order to predict the fuel mixture preparation inside the cylinder, a model for the fuel film separation near the sharp edges of the intake valves has been developed. A separation criterion is set up using an analogy with Rayleigh-Taylor instabilities driven by the inertial forces of the film. The critical value for the separation criterion is adjusted using experimental data obtained in a two-dimensional wind tunnel fitted with different steps shaped as the valve seat and reproducing the main characteristics of the intake of a spark ignition engine. Computational fluid dynamics simulations are performed using the KMB code, a modified version of KIVA-2 already including a film model and a stochastic Lagrangian description of the spray. Computation for the intake stroke on a four-cylinder 1.9 litre port fuel injection engine confirms that the fuel droplets are not completely vaporized at the end of the intake stroke.

scholarly journals Individual Cylinder Combustion Optimization to Improve Performance and Fuel Consumption of a Small Turbocharged SI Engine

Energies ◽  
2020 ◽  
Vol 13 (21) ◽  
pp. 5548
Author(s):  
Luca Marchitto ◽  
Cinzia Tornatore ◽  
Luigi Teodosio
Keyword(s):  
Fuel Consumption ◽  
Internal Combustion Engines ◽  
Fuel Injection ◽  
Combustion Process ◽  
Operating Conditions ◽  
Spark Ignition Engine ◽  
Exhaust Emission ◽  
Cycle Variation ◽  
Spark Timing ◽  
Experimental Findings

Stringent exhaust emission and fuel consumption regulations impose the need for new solutions for further development of internal combustion engines. With this in mind, a refined control of the combustion process in each cylinder can represent a useful and affordable way to limit cycle-to-cycle and cylinder-to-cylinder variation reducing CO2 emission. In this paper, a twin-cylinder turbocharged Port Fuel Injection–Spark Ignition engine is experimentally and numerically characterized under different operating conditions in order to investigate the influence of cycle-to-cycle variation and cylinder-to-cylinder variability on the combustion and performance. Significant differences in the combustion behavior between cylinders were found, mainly due to a non-uniform effective in-cylinder air/fuel (A/F) ratio. For each cylinder, the coefficients of variation (CoVs) of selected combustion parameters are used to quantify the cyclic dispersion. Experimental-derived CoV correlations representative of the engine behavior are developed, validated against the measurements in various speed/load points and then coupled to an advanced 1D model of the whole engine. The latter is employed to reproduce the experimental findings, taking into account the effects of cycle-to-cycle variation. Once validated, the whole model is applied to optimize single cylinder operation, mainly acting on the spark timing and fuel injection, with the aim to reduce the specific fuel consumption and cyclic dispersion.

A Novel Method to Estimate Parameters of the Wall-Wetting Fuel Model in MPFI Engines for Cold Start and Warm Up Conditions

2004 ◽  
Author(s):  
M. Shahbakhti ◽  
M. Ghafuri ◽  
A. R. Aslani ◽  
A. Sahraeian ◽  
S. A. Jazayeri ◽  
...  
Keyword(s):  
Fuel Injection ◽  
Cold Start ◽  
Spark Ignition Engine ◽  
Intake Manifold ◽  
Exhaust Emission ◽  
Model Parameters ◽  
Transfer Model ◽  
Fuel Film ◽  
Warm Up ◽  
Fuel Ratio

In order to fulfill the LEV/ULEV exhaust emission standards, it is necessary to have a precise control of air fuel ratio under transient conditions especially during cold start and warm up periods. The objective in this study was to estimate parameters of a fuel delivery model and use them to provide a correct fuel injection compensation strategy. In this study, fuel transfer characteristics of intake port of a typical fuel-injected spark ignition engine have been determined for engine warm-up conditions following cold starts at temperature down to −15°C and extending to fully-warmed-up conditions, using a method based upon perturbing fuel injection rate and recording AFR (Air Fuel Ratio) response. Since there was no cold chamber available to perform tests in cold start conditions, a new method was utilized to simulate cold start conditions. This method can be used on any PFI engine with closed valve injection strategy. Following the estimation of fuel transfer model parameters, the variation of fuel film deposit factor (X), fuel film evaporation time constant (τf) and transport delay to oxygen sensor (ΔT) parameters over a range of temperatures, engine speeds and intake manifold pressures have been evaluated, providing a good insight to define transient fuel compensation requirements for cold start and warm up conditions.

A Method to Determine Fuel Transport Dynamics Model Parameters in Port Fuel Injected Gasoline Engines During Cold Start and Warm-Up Conditions

2010 ◽  
Vol 132 (7) ◽  
Author(s):  
M. Shahbakhti ◽  
M. Ghafuri ◽  
A. R. Aslani ◽  
A. Sahraeian ◽  
S. A. Jazayeri ◽  
...  
Keyword(s):  
Thermal Conditions ◽  
Cold Start ◽  
Operating Conditions ◽  
Spark Ignition Engine ◽  
New Method ◽  
Intake Manifold ◽  
Dynamics Model ◽  
Fuel Film ◽  
Warm Up ◽  
Transport Dynamics

In order to meet stringent emission standards, it is essential to have a precise control of air-fuel ratio (AFR) under cold start and warm-up conditions. This requires an understanding of the fuel transport dynamics in the intake system during these conditions. This study centers on estimating the parameters of a fuel transport dynamics model during engine operation at different thermal conditions ranging from cold start to fully warmed-up conditions. A method of system identification based on perturbing fuel injection rate is used to find fuel dynamics parameters in a port fuel injected (PFI) spark ignition engine. Since there was no cold chamber available to prepare cold start conditions, a new method was utilized to simulate cold start conditions. The new method can be applied on PFI engines, which use closed valve injection timing. A four-cylinder PFI engine is tested for different thermal conditions from −15°C to 82°C at a range of engine speeds and intake manifold pressures. A good agreement is observed between simulated and experimental AFR for 52 different transient operating conditions presented in this study. Results indicate that both fuel film deposit factor (X) and fuel film evaporation time constant (τf) decrease with increasing coolant temperature or engine speed. In addition, an increase in the intake manifold pressure results in an increase in X while causes a decrease in τf.

scholarly journals Ethanol/Gasoline Blends as Alternative Fuel in Last Generation Spark-Ignition Engines: A Review on CO and HC Engine Out Emissions

Energies ◽  
2021 ◽  
Vol 14 (13) ◽  
pp. 4034
Author(s):  
Paolo Iodice ◽  
Massimo Cardone
Keyword(s):  
Physicochemical Properties ◽  
Alternative Fuels ◽  
Experimental Studies ◽  
Alternative Fuel ◽  
Exhaust Emissions ◽  
Spark Ignition ◽  
Operating Conditions ◽  
Spark Ignition Engine ◽  
Spark Ignition Engines ◽  
The Impact

Among the alternative fuels existing for spark-ignition engines, ethanol is considered worldwide as an important renewable fuel when mixed with pure gasoline because of its favorable physicochemical properties. An in-depth and updated investigation on the issue of CO and HC engine out emissions related to use of ethanol/gasoline fuels in spark-ignition engines is therefore necessary. Starting from our experimental studies on engine out emissions of a last generation spark-ignition engine fueled with ethanol/gasoline fuels, the aim of this new investigation is to offer a complete literature review on the present state of ethanol combustion in last generation spark-ignition engines under real working conditions to clarify the possible change in CO and HC emissions. In the first section of this paper, a comparison between physicochemical properties of ethanol and gasoline is examined to assess the practicability of using ethanol as an alternative fuel for spark-ignition engines and to investigate the effect on engine out emissions and combustion efficiency. In the next section, this article focuses on the impact of ethanol/gasoline fuels on CO and HC formation. Many studies related to combustion characteristics and exhaust emissions in spark-ignition engines fueled with ethanol/gasoline fuels are thus discussed in detail. Most of these experimental investigations conclude that the addition of ethanol with gasoline fuel mixtures can really decrease the CO and HC exhaust emissions of last generation spark-ignition engines in several operating conditions.

scholarly journals A 2-D model for Intermediate Temperature Solid Oxide Fuel Cells Preliminarily Validated on Local Values

Catalysts ◽  
2019 ◽  
Vol 9 (1) ◽  
pp. 36 ◽  
Author(s):  
Bruno Conti ◽  
Barbara Bosio ◽  
Stephen John McPhail ◽  
Francesca Santoni ◽  
Davide Pumiglia ◽  
...  
Keyword(s):  
Fuel Cells ◽  
Operating Conditions ◽  
Solid Oxide ◽  
Intermediate Temperature ◽  
Physical Parameters ◽  
Local Concentration ◽  
Oxide Fuel ◽  
Molten Carbonate ◽  
Experimental Apparatus ◽  
Set Up

Intermediate Temperature Solid Oxide Fuel Cell (IT-SOFC) technology offers interesting opportunities in the panorama of a larger penetration of renewable and distributed power generation, namely high electrical efficiency at manageable scales for both remote and industrial applications. In order to optimize the performance and the operating conditions of such a pre-commercial technology, an effective synergy between experimentation and simulation is fundamental. For this purpose, starting from the SIMFC (SIMulation of Fuel Cells) code set-up and successfully validated for Molten Carbonate Fuel Cells, a new version of the code has been developed for IT-SOFCs. The new release of the code allows the calculation of the maps of the main electrical, chemical, and physical parameters on the cell plane of planar IT-SOFCs fed in co-flow. A semi-empirical kinetic formulation has been set-up, identifying the related parameters thanks to a devoted series of experiments, and integrated in SIMFC. Thanks to a multi-sampling innovative experimental apparatus the simultaneous measurement of temperature and gas composition on the cell plane was possible, so that a preliminary validation of the model on local values was carried out. A good agreement between experimental and simulated data was achieved in terms of cell voltages and local temperatures, but also, for the first time, in terms of local concentration on the cell plane, encouraging further developments. This numerical tool is proposed for a better interpretation of the phenomena occurring in IT-SOFCs and a consequential optimization of their performance.

Modeling of Gas Turbine Fuel Nozzle Spray

1997 ◽  
Vol 119 (1) ◽  
pp. 34-44 ◽  
Author(s):  
N. K. Rizk ◽  
J. S. Chin ◽  
M. K. Razdan
Keyword(s):  
Gas Turbine ◽  
Fuel Injection ◽  
Near Field ◽  
Continuous Phase ◽  
Liquid Sheet ◽  
Vapor Concentration ◽  
Fuel Vapor ◽  
Fuel Injector ◽  
Gas Temperature ◽  
Sheet Breakup

Satisfactory performance of the gas turbine combustor relies on the careful design of various components, particularly the fuel injector. It is, therefore, essential to establish a fundamental basis for fuel injection modeling that involves various atomization processes. A two-dimensional fuel injection model has been formulated to simulate the airflow within and downstream of the atomizer and address the formation and breakup of the liquid sheet formed at the atomizer exit. The sheet breakup under the effects of airblast, fuel pressure, or the combined atomization mode of the airassist type is considered in the calculation. The model accounts for secondary breakup of drops and the stochastic Lagrangian treatment of spray. The calculation of spray evaporation addresses both droplet heat-up and steady-state mechanisms, and fuel vapor concentration is based on the partial pressure concept. An enhanced evaporation model has been developed that accounts for multicomponent, finite mass diffusivity and conductivity effects, and addresses near-critical evaporation. The presents investigation involved predictions of flow and spray characteristics of two distinctively different fuel atomizers under both nonreacting and reacting conditions. The predictions of the continuous phase velocity components and the spray mean drop sizes agree well with the detailed measurements obtained for the two atomizers, which indicates the model accounts for key aspects of atomization. The model also provides insight into ligament formation and breakup at the atomizer exit and the initial drop sizes formed in the atomizer near field region where measurements are difficult to obtain. The calculations of the reacting spray show the fuel-rich region occupied most of the spray volume with two-peak radial gas temperature profiles. The results also provided local concentrations of unburned hydrocarbon (UHC) and carbon monoxide (CO) in atomizer flowfield, information that could support the effort to reduce emission levels of gas turbine combustors.

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