scholarly journals 3D-CFD Simulation of a GDI Injector Under Standard and Flashing Conditions

2020 ◽  
Vol 197 ◽  
pp. 06002
Author(s):  
Simone Sparacino ◽  
Fabio Berni ◽  
Matteo Riccardi ◽  
Andrea Cavicchi ◽  
Lucio Postrioti
Keyword(s):  
Combustion Chamber ◽  
Ambient Pressure ◽  
Cone Angle ◽  
Combustion Process ◽  
Operating Conditions ◽  
Pollutant Emissions ◽  
Experimental Comparison ◽  
Spray Cone ◽  
Wide Range ◽  
Flash Boiling

In the optimization of GDI engines, fuel injection plays a crucial role since it can affect the combustion process and, thus, fuel efficiency and pollutant emissions. The challenging task is to obtain the required fuel distribution and atomization inside the combustion chamber over a wide range of engine operating conditions. To achieve such goals, flash-boiling can be exploited. Flash-boiling is a phenomenon occurring when fuel temperature exceeds saturation temperature or, similarly, when ambient pressure is lower than saturation one. Under these conditions, which can occur inside the injector or directly in the combustion chamber, the fuel undergoes extremely accelerated breakup and quickly evaporates. The proposed manuscript shows the application of an alternative flashboiling model, recently implemented by Siemens-PLM in STAR-CD V.2019.1, to be applied in 3D-CFD Lagrangian simulations of GDI sprays. Results are validated against experimental data, provided by the SprayLAB of the University of Perugia, on a single-hole research injector. The new flash-boiling model consists of three main parts: an atomization model able to compute droplet initial conditions and the overall spray cone angle; an evaporation model and, finally, a droplet break-up model; the last two models are designed to simulate all the physical events occurring when droplets are injected into the combustion chamber. As for the investigated operating condition, vessel pressure and temperature are 40 kPa and 293K, respectively; as for the fuel (n-Heptane) temperature, it ranges from 303.15 K to 393.15 K, on equal injection pressure (10 MPa). The numerical-experimental comparison is carried out in terms of liquid penetration, imaging, and droplet sizing.

Effects of Fuel Nozzle Condition on Gas Turbine Combustion Chamber Exit Temperature Distributions

2010 ◽  
Author(s):  
Kristen Bishop ◽  
William Allan
Keyword(s):  
Combustion Chamber ◽  
Ambient Pressure ◽  
Cone Angle ◽  
Operating Conditions ◽  
Spray Cone Angle ◽  
Mixing Processes ◽  
Spray Cone ◽  
Temperature Distributions ◽  
Fuel Nozzle ◽  
Exit Temperature

The effects of fuel nozzle condition on the temperature distributions experienced by the nozzle guide vanes have been investigated using an optical patternator. Average spray cone angle, symmetry, and fuel streaks were quantified. An ambient pressure and temperature combustion chamber test rig was used to capture exit temperature distributions and to determine the pattern factor. The rig tests matched representative engine operating conditions by matching Mach number, equivalence ratio, and fuel droplet size. It was observed that very small deviations (± 10° in spray cone angle) from a nominal distribution in the fuel nozzle spray pattern correlated to increases in pattern factor, apparently due to a degradation of mixing processes, which created larger regions of very high temperature core flow and smaller regions of cooler temperatures within the combustion chamber exit plane. The spray cone angle had the most measureable influence while the effects of spray roundness and streak intensity had slightly less influence. Comparisons were made with published studies conducted on the combustion chamber geometry, and recommendations were made for fuel nozzle inspections.

scholarly journals Experimental Studies of Fuel Injection in a Diesel Engine with an Inclined Injector

Energies ◽  
2019 ◽  
Vol 12 (14) ◽  
pp. 2643
Author(s):  
V. G. Kamaltdinov ◽  
V. A. Markov ◽  
I. O. Lysov ◽  
A. A. Zherdev ◽  
V. V. Furman
Keyword(s):  
Combustion Chamber ◽  
High Speed ◽  
Cone Angle ◽  
Combustion Process ◽  
Experimental Studies ◽  
Uneven Distribution ◽  
Orifice Diameter ◽  
Spray Cone ◽  
Fuel Sprays ◽  
The Difference

Comparative experimental studies of fuel sprays evolution dynamics in a constant volume chamber were carried out with a view to reduce the uneven distribution of diesel fuel in the combustion chamber when the Common Rail injector is inclined. The fuel sprays was captured by a high-speed camera with simultaneous recording of control pulses of camera and injector on an oscilloscope. Two eight-hole diesel injectors were investigated: One injector with identical orifice diameter (nozzle 1) and another injector with four orifices of the same diameter as orifices of nozzle 1 and four orifices of enlarged diameters (nozzle 2). Both injectors were tested at rail pressure from 100 to 165 MPa and injector control pulse width of 1.5 ms. The dynamics of changes in the spray penetration length and spray cone angle were determined. It was found that sprays develop differently in nozzle 1 fuel. The difference in the length of fuel sprays is 10–15 mm. As for nozzle 2, the fuel sprays develop more evenly: The difference in length is no more than 3–5 mm. The difference of the measured fuel spray cone angles for nozzle 1 is 0.5°–1.5°, and for nozzle 2 is 3.0°–4.0°. It is concluded that the differential increase in the diameters of nozzle orifices, the axes of which are maximally deviated from the injector axis, makes it possible to reduce the uneven distribution of fuel in the combustion chamber and improve the combustion process and the diesel performance as a whole.

Computational and Experimental Analysis of Direct CNG Injection and Mixture Formation in a Spark Ignition Research Engine

2010 ◽  
Author(s):  
Mirko Baratta ◽  
Andrea E. Catania ◽  
Francesco C. Pesce
Keyword(s):  
Numerical Model ◽  
Combustion Chamber ◽  
Cone Angle ◽  
Combustion Process ◽  
Laser Induced Fluorescence ◽  
Operating Conditions ◽  
Design Parameters ◽  
Experimental Investigations ◽  
Injection Timing ◽  
Mixture Formation

Direct injection (DI) of compressed natural gas (CNG) under high pressure conditions is a topic of great interest, owing to its potential for improving SI engine performance and fuel consumption. However, relevant technical difficulties have yet to be resolved in order to stabilize combustion process, especially for stratified engine operating conditions. The present paper is focused on experimental and numerical investigations of the jet formation and fuel-air mixing process in a research optical-access single-cylinder engine. The engine is based on the multi-cylinder engine under development within the European Community (EC) VII Framework Program (FP) InGAS Integrated Project, and features a centrally mounted poppet-valve injector on a pent-roof combustion chamber with a bowl in piston. Experimental investigations were made by means of the planar laser-induced fluorescence technique, and revealed a cycle-to-cycle jet shape variability. In particular, for specific cylinder pressure values at the start of injection, the jet can adhere to chamber walls for a relevant number of cycles, leading to an ‘umbrella-like’ shape. This can change the mixing capabilities of the combustion chamber and cause instabilities in the combustion process. The mentioned behaviour is strongly dependent not only on the injection and cylinder pressures, but also on important design parameters, such as needle cone angle and in-chamber injector protrusion. For this reason, in order to obtain a deep insight into the injected gas behaviour on an average cycle basis, the experimental investigation was supported by a numerical analysis. Simulations were carried out by an optimized variable-density finite-volume numerical model which was built within the Star-CD environment. A previously developed and validated ‘virtual injector’ model was implemented. The outcomes of the numerical model were compared to laser-induced fluorescence images, for both stratified- and homogeneous-charge engine operating conditions and a good agreement was obtained, substantiating the reliability of the applied computational model. Then, the effects of the injector protrusion in the combustion chamber and of injection timing were analyzed, and their impact on jet stability and mixture-formation process was analyzed.

Structure of Airblast Sprays Under High Ambient Pressure Conditions

1997 ◽  
Vol 119 (3) ◽  
pp. 512-518 ◽  
Author(s):  
Q. P. Zheng ◽  
A. K. Jasuja ◽  
A. H. Lefebvre
Keyword(s):  
Ambient Pressure ◽  
Laser Sheet ◽  
Cone Angle ◽  
Ambient Air ◽  
Operating Conditions ◽  
Air Pressure ◽  
Spray Cone Angle ◽  
Spray Cone ◽  
Spray Volume ◽  
Drop Size Distributions

A single-velocity-component phase Doppler particle analyzer is used to survey and measure local variations in drop-size distributions and drop velocities in the nearnozzle region of a practical, contraswirling, prefilming airblast atomizer. The technique of laser sheet imaging is used to obtain global patterns of the spray. All measurements are taken with a constant pressure drop across the atomizer of 5 percent, at ambient air pressures of 1, 6, and 12 bar. The liquid employed is aviation kerosine at flow rates up to 75 g/s. The results show that increasing the air pressure from 1 to 12 bar at a constant air/fuel ratio causes the initial spray cone angle to widen from 70 to 105 deg. Farther downstream the spray volume remains largely unaffected by variations in atomizer operating conditions. However, the radial distribution of fuel within the spray volume is such that increases in fuel flow rate cause a larger proportion of fuel to be contained in the outer regions of the spray. The effect of ambient pressure on the overall Sauter mean diameter is small. This is attributed to the fact that the rapid disintegration of the fuel sheet produced by the contraswirling air streams ensures that the atomization process is dominated by the “prompt” mechanism. For this mode of liquid breakup, theory predicts that mean drop sizes are independent of air pressure.

scholarly journals X-ray diagnostics of dodecane jet in spray A conditions using the new one shot engine (NOSE)

2017 ◽  
Author(s):  
Ajrouche Hugo ◽  
Chiboub Ibrahim ◽  
Nilaphai Ob ◽  
Dozias Sébastien ◽  
Moreau Bruno ◽  
...  
Keyword(s):  
Ambient Pressure ◽  
Cone Angle ◽  
Physical Characteristics ◽  
Operating Conditions ◽  
Photon Absorption ◽  
Optical Methods ◽  
Working Fluid ◽  
X Rays ◽  
Spray Cone ◽  
X Ray

Quantifying liquid mass distribution data in the dense near nozzle area to develop and optimize diesel spray byoptical diagnostic is challenging. Optical methods, while providing valuable information, have intrinsic limitations due to the strong scattering of visible light at gas-liquid boundaries. Because of the high density of the droplets near the nozzle, most optical methods are ineffective in this area and prevent the acquisition of reliable quantitative data. X-ray diagnostics offer a solution to this issue, since the main interaction between the fuel and the X-rays is absorption, rather than scattering, thus X-ray technique offers an appealing alternative to optical techniques for studying fuel sprays. Over the last decade, x-ray radiography experiments have demonstrated the ability to perform quantitative measurements in complex sprays. In the present work, an X-ray technique based on X-ray absorption has been conducted to perform measurements in dodecane fuel spray injected from a single-hole nozzle at high injection pressure and high temperature. The working fluid has been doped with DPX 9 containing a Cerium additive, which acts as a contrast agent. The first step of this work was to address the effect of this dopant, which increases the sensitivity of X-ray diagnostics due its strong photon absorption, on the behavior and the physical characteristics of n-dodecane spray. Comparisons of the diffused back illumination images acquired from n- dodecane spray with and without DPX 9 under similar operating conditions show several significant differences. The current data show clearly that the liquid penetration length is different when DPX 9 is mixed with dodecane. To address this problem, the dodecane was doped with a several quantities of DPX containing 25% ± 0.5 of Cerium. Experiments show that 1.25% of Ce doesn’t affect the behaviour of spray. Radiography and density measurements at ambient pressure and 60 bars are presented. Spray cone angle around 5° is obtained. The obtained data shows that the result is a compromise between the concentration of dopant for which the physical characteristics of thespray do not change and the visualization of the jet by X-ray for this concentration.DOI: http://dx.doi.org/10.4995/ILASS2017.2017.4705

Spray Characteristics of Swirl Effervescent Injector in Rocket Application: A Review

2012 ◽  
Vol 225 ◽  
pp. 423-428
Author(s):  
Zulkifli Abdul Ghaffar ◽  
Ahmad Hussein Abdul Hamid ◽  
Mohd Syazwan Firdaus Mat Rashid
Keyword(s):  
Combustion Chamber ◽  
Rocket Engine ◽  
Cone Angle ◽  
Operating Conditions ◽  
Spray Characteristics ◽  
Spray Cone Angle ◽  
Spray Cone ◽  
Breakup Length ◽  
Mixing Chamber ◽  
Discharge Orifice

Injector is one of the vital devices in liquid rocket engine (LRE) as small changes in its configurations and design can result in significantly different LRE performance. Characteristics of spray such as spray cone angle, breakup length and Sauter mean diameter (SMD) are examples of crucial parameters that play the important role in the performance of liquid propellant rocket engine. Wider spray cone angle is beneficial for widespread of fuel in the combustion chamber for fast quiet ignition and a shorter breakup length provides shorter combustion chamber to be utilized and small SMD will result in fast and clean combustion. There are several mechanisms of liquid atomization such as swirling, e.g. jet swirl atomization or introducing bubbles into the liquid and effervescent atomization. Introducing a swirl component in the flow can enhance the propellant atomization and mixing whereas introducing bubbling gas directly into the liquid stream inside the injector leads to finer sprays even at lower injection pressures. This paper reviews the influence of both operating conditions and injector internal geometries towards the spray characteristics of swirl effervescent injectors. Operating conditions reviewed are injection pressure and gas-to-liquid ratio (GLR), while the injector internal geometries reviewed are limited to swirler geometry, mixing chamber diameter (dc), mixing chamber length (lc), aeration hole diameter (da), discharge orifice diameter (do) and discharge orifice length (lo).

Droplet size and velocity distributions in a spray from a pressure swirl atomizer: Application of maximum entropy formalism

2004 ◽  
Vol 218 (7) ◽  
pp. 737-749 ◽  
Author(s):  
D Mondal ◽  
A Datta ◽  
A Sarkar
Keyword(s):  
Maximum Entropy ◽  
Droplet Size ◽  
Ambient Pressure ◽  
Cone Angle ◽  
Distribution Functions ◽  
Operating Conditions ◽  
Spray Parameters ◽  
Spray Cone ◽  
Maximum Entropy Formalism ◽  
Pressure Swirl

The present work has attempted a unification of the empirical spray parameters for the pressure swirl atomizers with the maximum entropy formalism principle for the predictions of both size and velocity distributions in a spray. The information entropy is maximized under suitable constraint conditions to evaluate a number-based droplet size and velocity joint distribution parameter. The constraint equations have been defined to include the spray parameters, such as the Sauter mean diameter, spray cone angle and liquid film thickness, to consider their influence on the distribution. A comparison of the predicted results using the present theory is made with the experimental data available in the literature and good agreement is achieved. The effects of the atomizer input conditions, such as injection pressure, ambient pressure and the properties of atomizing liquids, on the size and velocity distributions are studied using the present model. A calculation of the efficiency of the atomization process using the size and velocity distribution functions is also made to study the effect of operating conditions on the performance of atomization.

Structure of Airblast Sprays Under High Ambient Pressure Conditions

1996 ◽  
Author(s):  
Q. P. Zheng ◽  
A. K. Jasuja ◽  
A. H. Lefebvre
Keyword(s):  
Ambient Pressure ◽  
Laser Sheet ◽  
Cone Angle ◽  
Ambient Air ◽  
Operating Conditions ◽  
Air Pressure ◽  
Spray Cone Angle ◽  
Spray Cone ◽  
Spray Volume ◽  
Drop Size Distributions

A single-velocity-component Phase Doppler Particle Analyzer is used to survey and measure local variations in drop-size distributions and drop velocities in the near-nozzle region of a practical, contra-swirling, prefilming airblast atomizer. The technique of Laser Sheet Imaging is used to obtain global patterns of the spray. All measurements are taken with a constant pressure drop across the atomizer of 5 percent, at ambient air pressures of 1, 6 and 12 bar. The liquid employed is aviation kerosine at flow rates up to 75 g/s. The results show that increasing the air pressure from 1 to 12 bar at a constant air/fuel ratio causes the initial spray cone angle to widen from 85° to 105°. Further downstream the spray volume remains largely unaffected by variations in atomizer operating conditions. However, the radial distribution of fuel within the spray volume is such that increases in fuel flow rate cause a larger proportion of fuel to be contained in the outer regions of the spray. The effect of ambient pressure on the overall Sauter mean diameter is small. This is attributed to the fact that the rapid disintegration of the fuel sheet produced by the contra-swirling air streams ensures that the atomization process is dominated by the ‘prompt’ mechanism. For this mode of liquid breakup, theory predicts that mean drop sizes are independent of air pressure.

Prediction of gaseous pollutant emissions from a spark-ignition direct-injection engine with gas-exchange simulation

2021 ◽  
pp. 146808742110050
Author(s):  
Stefania Esposito ◽  
Lutz Diekhoff ◽  
Stefan Pischinger
Keyword(s):  
Gas Exchange ◽  
Combustion Chamber ◽  
Direct Injection ◽  
Spark Ignition ◽  
Operating Conditions ◽  
Pollutant Emissions ◽  
Operating Parameters ◽  
Gaseous Pollutant ◽  
Fuel Ratio ◽  
No Emissions

With the further tightening of emission regulations and the introduction of real driving emission tests (RDE), the simulative prediction of emissions is becoming increasingly important for the development of future low-emission internal combustion engines. In this context, gas-exchange simulation can be used as a powerful tool for the evaluation of new design concepts. However, the simplified description of the combustion chamber can make the prediction of complex in-cylinder phenomena like emission formation quite challenging. The present work focuses on the prediction of gaseous pollutants from a spark-ignition (SI) direct injection (DI) engine with 1D–0D gas-exchange simulations. The accuracy of the simulative prediction regarding gaseous pollutant emissions is assessed based on the comparison with measurement data obtained with a research single cylinder engine (SCE). Multiple variations of engine operating parameters – for example, load, speed, air-to-fuel ratio, valve timing – are taken into account to verify the predictivity of the simulation toward changing engine operating conditions. Regarding the unburned hydrocarbon (HC) emissions, phenomenological models are used to estimate the contribution of the piston top-land crevice as well as flame wall-quenching and oil-film fuel adsorption-desorption mechanisms. Regarding CO and NO emissions, multiple approaches to describe the burned zone kinetics in combination with a two-zone 0D combustion chamber model are evaluated. In particular, calculations with reduced reaction kinetics are compared with simplified kinetic descriptions. At engine warm operation, the HC models show an accuracy mainly within 20%. The predictions for the NO emissions follow the trend of the measurements with changing engine operating parameters and all modeled results are mainly within ±20%. Regarding CO emissions, the simplified kinetic models are not capable to predict CO at stoichiometric conditions with errors below 30%. With the usage of a reduced kinetic mechanism, a better prediction capability of CO at stoichiometric air-to-fuel ratio could be achieved.

Effects of H2 Addition to CNG Blends on Cycle-to-Cycle and Cylinder-to-Cylinder Combustion Variation in an SI Engine

2012 ◽  
Author(s):  
Mirko Baratta ◽  
Stefano d’Ambrosio ◽  
Daniela Misul ◽  
Ezio Spessa
Keyword(s):  
Diagnostic Tool ◽  
Combustion Process ◽  
Experimental Tests ◽  
Test Point ◽  
Pollutant Emissions ◽  
Engine Operation ◽  
Pressure Transducers ◽  
Rate Analysis ◽  
Spark Plug ◽  
Wide Range

An experimental investigation and a burning-rate analysis have been performed on a production 1.4 liter CNG (compressed natural gas) engine fueled with methane-hydrogen blends. The engine features a pent-roof combustion chamber, four valves per cylinder and a centrally located spark plug. The experimental tests have been carried out in order to quantify the cycle-to-cycle and the cylinder-to-cylinder combustion variation. Therefore, the engine has been equipped with four dedicated piezoelectric pressure transducers placed on each cylinder and located by the spark plug. At each test point, in-cylinder pressure, fuel consumption, induced air mass flow rate, pressure and temperature at different locations on the engine intake and exhaust systems as well as ‘engine-out’ pollutant emissions have been measured. The signals correlated to the engine operation have been acquired by means of a National Instruments PXI-DAQ system and a home developed software. The acquired data have then been processed through a combustion diagnostic tool resulting from the integration of an original multizone thermodynamic model with a CAD procedure for the evaluation of the burned-gas front geometry. The diagnostic tool allows the burning velocities to be computed. The tests have been performed over a wide range of engine speeds, loads and relative air-fuel ratios (up to the lean operation). For stoichiometric operation, the addition of hydrogen to CNG has produced a bsfc reduction ranging between 2 to 7% and a bsTHC decrease up to the 40%. These benefits have appeared to be even higher for lean mixtures. Moreover, hydrogen has shown to significantly enhance the combustion process, thus leading to a sensibly lower cycle-to-cycle variability. As a matter of fact, hydrogen addition has generally resulted into extended operation up to RAFR = 1.8. Still, a discrepancy in the abovementioned conclusions was observed depending on the engine cylinder considered.

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