Energies

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23 pages, 36341 KiB

Open AccessArticle

Turbulent Flame Geometry Measurements in a Mass-Production Gasoline Direct Injection Engine

by Manfredi Villani and Phillip Aquino

Energies 2020, 13(1), 189; https://doi.org/10.3390/en13010189 - 1 Jan 2020

Cited by 1 | Viewed by 2197

Direct optical access to the combustion chamber of a gasoline direct injection (GDI) engine provides extremely valuable information about the combustion process. Experimental measurements of the geometric characteristics of the turbulent flame—such as the flame radius, flame center, flame edges and flame brush [...] Read more.

Direct optical access to the combustion chamber of a gasoline direct injection (GDI) engine provides extremely valuable information about the combustion process. Experimental measurements of the geometric characteristics of the turbulent flame—such as the flame radius, flame center, flame edges and flame brush thickness—are of fundamental interest in support of the development and validation of any combustion model. To determine the macroscopic properties of sprays and flames, visualization and digital image processing techniques are typically used in controlled experimental setups like single-cylinder optical engines or closed vessels, while optical measurements on mass-production engines are more uncommon. In this paper the optical experimental setup (consisting of a high-speed camera, a laser light source and a data acquisition system) used to characterize the planar turbulent flame propagation in the cylinder of a 3.5 L GDI V6 mass-production engine, is described. The image acquisition process and the image processing that is necessary to evaluate the geometric characteristics of the propagating flame front, which are usually omitted in the referenced literature, are reported in detail to provide a useful guideline to other researchers. The results show that the step-by-step algorithm and the calculation formulae proposed allow to retrieve clear visualizations of the propagating flame front and measurements of its geometrical properties. Full article

(This article belongs to the Special Issue Experimental and Numerical Analysis of Fuel Spray in Engines)

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22 pages, 19772 KiB

Open AccessFeature PaperArticle

CFD Analysis of Port Water Injection in a GDI Engine under Incipient Knock Conditions

by Jacopo Zembi, Michele Battistoni, Francesco Ranuzzi, Nicolò Cavina and Matteo De Cesare

Energies 2019, 12(18), 3409; https://doi.org/10.3390/en12183409 - 4 Sep 2019

Cited by 30 | Viewed by 3435

Abstract

This paper investigates, through computational fluid dynamics (CFD) simulations, the knock resistance improvements that can be obtained in a turbo-charged GDI engine with water injection. In a first step, water and gasoline injector models are validated comparing the results with experimental data from [...] Read more.

This paper investigates, through computational fluid dynamics (CFD) simulations, the knock resistance improvements that can be obtained in a turbo-charged GDI engine with water injection. In a first step, water and gasoline injector models are validated comparing the results with experimental data from constant volume chamber tests. Then, multi-cycle simulations are performed using the G-equation turbulent combustion model focusing on spray evolution and wall film dynamics. The main intent is analyzing the effectiveness of different water injection timings and injection pressures in a port water injection (PWI) installation. Combustion rates are validated against experimental engine data, with and without water injection. Afterwards, in order to predict autoignition behavior with different spark advance (SA) timings, the extended coherent flamelet model (ECFM) combined with a tabulated kinetic ignition (TKI) dataset is used. End-gas autoignition delays are calculated using a reduced mechanism for toluene primary reference fuel (TPRF), which revealed essential for capturing actual gasoline ignition characteristics. Results indicate that the water atomization quality, i.e., injection pressure, is significant in a PWI installation allowing a reduction of the water wall film formation in the ports. Water injection timing needs also to be carefully chosen for optimized performance. As the injected water allows the SA to be increased, the overall benefits on indicated mean effective pressure and fuel consumption are quantified under the same knock safety margin, matching adequately well the available measurements. Full article

(This article belongs to the Special Issue Experimental and Numerical Analysis of Fuel Spray in Engines)

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19 pages, 10465 KiB

Open AccessArticle

The Effect of Initial Conditions on the Laminar Burning Characteristics of Natural Gas Diluted by CO₂

by Zhiqiang Han, Zhennan Zhu, Peng Wang, Kun Liang, Zinong Zuo and Dongjian Zeng

Energies 2019, 12(15), 2892; https://doi.org/10.3390/en12152892 - 27 Jul 2019

Cited by 5 | Viewed by 2610

Abstract

The initial conditions such as temperature, pressure and dilution rate can have an effect on the laminar burning velocity of natural gas. It is acknowledged that there is an equivalent effect on the laminar burning velocity between any two initial conditions. The effects [...] Read more.

The initial conditions such as temperature, pressure and dilution rate can have an effect on the laminar burning velocity of natural gas. It is acknowledged that there is an equivalent effect on the laminar burning velocity between any two initial conditions. The effects of initial temperatures (323 K–423 K), initial pressures (0.1 MPa–0.3 MPa) and dilution rate (0–16%, CO₂ as diluent gas) on the laminar burning velocity and the flame instability were investigated at a series of equivalence ratios (0.7–1.2) in a constant volume chamber. A chemical kinetic simulation was also conducted to calculate the laminar burning velocity and essential radicals’ concentrations under the same initial conditions. The results show that the laminar burning velocity of natural gas increases with initial temperature but decreases with initial pressure and dilution rate. The maximum concentrations of H, O and OH increase with initial temperature but decrease with initial pressure and dilution rate. Laminar burning velocity is highly correlated with the sum of the maximum concentration of H and OH. Full article

(This article belongs to the Special Issue Experimental and Numerical Analysis of Fuel Spray in Engines)

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24 pages, 20126 KiB

Open AccessArticle

Impact of the Primary Break-Up Strategy on the Morphology of GDI Sprays in 3D-CFD Simulations of Multi-Hole Injectors

by Simone Sparacino, Fabio Berni, Alessandro d’Adamo, Vesselin Krassimirov Krastev, Andrea Cavicchi and Lucio Postrioti

Energies 2019, 12(15), 2890; https://doi.org/10.3390/en12152890 - 26 Jul 2019

Cited by 28 | Viewed by 3515

Abstract

The scientific literature focusing on the numerical simulation of fuel sprays is rich in atomization and secondary break-up models. However, it is well known that the predictive capability of even the most diffused models is affected by the combination of injection parameters and [...] Read more.

The scientific literature focusing on the numerical simulation of fuel sprays is rich in atomization and secondary break-up models. However, it is well known that the predictive capability of even the most diffused models is affected by the combination of injection parameters and operating conditions, especially backpressure. In this paper, an alternative atomization strategy is proposed for the 3D-Computational Fluid Dynamics (CFD) simulation of Gasoline Direct Injection (GDI) sprays, aiming at extending simulation predictive capabilities over a wider range of operating conditions. In particular, attention is focused on the effects of back pressure, which has a remarkable impact on both the morphology and the sizing of GDI sprays. 3D-CFD Lagrangian simulations of two different multi-hole injectors are presented. The first injector is a 5-hole GDI prototype unit operated at ambient conditions. The second one is the well-known Spray G, characterized by a higher back pressure (up to 0.6 MPa). Numerical results are compared against experiments in terms of liquid penetration and Phase Doppler Anemometry (PDA) data of droplet sizing/velocity and imaging. CFD results are demonstrated to be highly sensitive to spray vessel pressure, mainly because of the atomization strategy. The proposed alternative approach proves to strongly reduce such dependency. Moreover, in order to further validate the alternative primary break-up strategy adopted for the initialization of the droplets, an internal nozzle flow simulation is carried out on the Spray G injector, able to provide information on the characteristic diameter of the liquid column exiting from the nozzle. Full article

(This article belongs to the Special Issue Experimental and Numerical Analysis of Fuel Spray in Engines)

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22 pages, 8241 KiB

Open AccessArticle

Close Nozzle Spray Characteristics of a Prefilming Airblast Atomizer

by Simon Holz, Samuel Braun, Geoffroy Chaussonnet, Rainer Koch and Hans-Jörg Bauer

Energies 2019, 12(14), 2835; https://doi.org/10.3390/en12142835 - 23 Jul 2019

Cited by 23 | Viewed by 5893

Abstract

The formation of pollutant emissions in jet engines is closely related to the fuel distribution inside the combustor. Hence, the characteristics of the spray formed during primary breakup are of major importance for an accurate prediction of the pollutant emissions. Currently, an Euler–Lagrangian [...] Read more.

The formation of pollutant emissions in jet engines is closely related to the fuel distribution inside the combustor. Hence, the characteristics of the spray formed during primary breakup are of major importance for an accurate prediction of the pollutant emissions. Currently, an Euler–Lagrangian approach for droplet transport in combination with combustion and pollutant formation models is used to predict the pollutant emissions. The missing element for predicting these emissions more accurately is well defined starting conditions for the liquid fuel droplets as they emerge from the fuel nozzle. Recently, it was demonstrated that the primary breakup can be predicted from first principles by the Lagrangian, mesh-free, Smoothed Particle Hydrodynamics (SPH) method. In the present work, 2D Direct Numerical Simulations (DNS) of a planar prefilming airblast atomizer using the SPH method are presented, which capture most of the breakup phenomena known from experiments. Strong links between the ligament breakup and the resulting spray in terms of droplet size, trajectory and velocity are demonstrated. The SPH predictions at elevated pressure conditions resemble quite well the effects observed in experiments. Significant interdependencies between droplet diameter, position and velocity are observed. This encourages to employ such multidimensional interdependence relations as a base for the development of primary atomization models. Full article

(This article belongs to the Special Issue Experimental and Numerical Analysis of Fuel Spray in Engines)

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13 pages, 2199 KiB

Open AccessArticle

Evaluation of a Scale-Resolving Methodology for the Multidimensional Simulation of GDI Sprays

by Giovanni Di Ilio, Vesselin K. Krastev and Giacomo Falcucci

Energies 2019, 12(14), 2699; https://doi.org/10.3390/en12142699 - 15 Jul 2019

Cited by 15 | Viewed by 2420

Abstract

The introduction of new emissions tests in real driving conditions (Real Driving Emissions—RDE) as well as of improved harmonized laboratory tests (World Harmonised Light Vehicle Test Procedure—WLTP) is going to dramatically cut down NO_x and particulate matter emissions [...] Read more.

The introduction of new emissions tests in real driving conditions (Real Driving Emissions—RDE) as well as of improved harmonized laboratory tests (World Harmonised Light Vehicle Test Procedure—WLTP) is going to dramatically cut down NO_x and particulate matter emissions for new car models that are intended to be fully Euro 6d compliant from 2020 onwards. Due to the technical challenges related to exhaust gases’ aftertreatment in small-size diesel engines, the current powertrain development trend for light passenger cars is shifted towards the application of different degrees of electrification to highly optimized gasoline direct injection (GDI) engines. As such, the importance of reliable multidimensional computational tools for GDI engine optimization is rapidly increasing. In the present paper, we assess a hybrid scale-resolving turbulence modeling technique for GDI fuel spray simulation, based on the Engine Combustion Network “Spray G” standard test case. Aspects such as the comparison with Reynolds-averaged methods and the sensitivity to the spray model parameters are discussed, and strengths and uncertainties of the analyzed hybrid approach are pointed out. The outcomes of this study serve as a basis for the evaluation of scale-resolving turbulence modeling options for the development of next-generation directly injected thermal engines. Full article

(This article belongs to the Special Issue Experimental and Numerical Analysis of Fuel Spray in Engines)

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18 pages, 6861 KiB

Open AccessArticle

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

by V. G. Kamaltdinov, V. A. Markov, I. O. Lysov, A. A. Zherdev and V. V. Furman

Energies 2019, 12(14), 2643; https://doi.org/10.3390/en12142643 - 10 Jul 2019

Cited by 16 | Viewed by 6852

Abstract

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 [...] Read more.

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. Full article

(This article belongs to the Special Issue Experimental and Numerical Analysis of Fuel Spray in Engines)

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16 pages, 29795 KiB

Open AccessArticle

Analyzing the Interaction of Vortex and Gas–Liquid Interface Dynamics in Fuel Spray Nozzles by Means of Lagrangian-Coherent Structures (2D)

by Thilo F. Dauch, Cihan Ates, Tobias Rapp, Marc C. Keller, Geoffroy Chaussonnet, Johannes Kaden, Max Okraschevski, Rainer Koch, Carsten Dachsbacher and Hans-Jörg Bauer

Energies 2019, 12(13), 2552; https://doi.org/10.3390/en12132552 - 2 Jul 2019

Cited by 10 | Viewed by 3845

Abstract

Predictions of the primary breakup of fuel in realistic fuel spray nozzles for aero-engine combustors by means of the SPH method are presented. Based on simulations in 2D, novel insights into the fundamental effects of primary breakup are established by analyzing the dynamics [...] Read more.

Predictions of the primary breakup of fuel in realistic fuel spray nozzles for aero-engine combustors by means of the SPH method are presented. Based on simulations in 2D, novel insights into the fundamental effects of primary breakup are established by analyzing the dynamics of Lagrangian-coherent structures (LCSs). An in-house visualization and data exploration platform is used in order to retrieve fields of the finite-time Lyapunov exponent (FTLE) derived from the SPH predictions aiming at the identification of time resolved LCSs. The main focus of this paper is demonstrating the suitability of FTLE fields to capture and visualize the interaction between the gas and the fuel flow leading to liquid disintegration. Aiming for a convenient illustration at a high spatial resolution, the analysis is presented based on 2D datasets. However, the method and the conclusions can analoguosly be transferred to 3D. The FTLE fields of modified nozzle geometries are compared in order to highlight the influence of the nozzle geometry on primary breakup, which is a novel and unique approach for this industrial application. Modifications of the geometry are proposed which are capable of suppressing the formation of certain LCSs, leading to less fluctuation of the fuel flow emerging from the spray nozzle. Full article

(This article belongs to the Special Issue Experimental and Numerical Analysis of Fuel Spray in Engines)

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17 pages, 4527 KiB

Open AccessArticle

Experimental Research of High-Temperature and High-Pressure Water Jet Characteristics in ICRC Engine Relevant Conditions

by Zhe Kang, Zhehao Zhang, Jun Deng, Liguang Li and Zhijun Wu

Energies 2019, 12(9), 1763; https://doi.org/10.3390/en12091763 - 9 May 2019

Cited by 11 | Viewed by 3277

Abstract

The internal combustion Rankine cycle (ICRC) concept provides a potential solution for future high thermal efficiency and low emission powertrains, and direct water injection (DWI) proved to be the key parameter for ICRC optimization. This paper was dedicated to investigating the fundamental mechanisms [...] Read more.

The internal combustion Rankine cycle (ICRC) concept provides a potential solution for future high thermal efficiency and low emission powertrains, and direct water injection (DWI) proved to be the key parameter for ICRC optimization. This paper was dedicated to investigating the fundamental mechanisms of water spray characteristics under different water injection control parameters. In order to do so, an experimental test system was carefully designed and built based on the Bosch and Schlieren methods: the Bosch method is utilized to measure the effect of injection and ambient pressure on water injection characteristics, and the Schlieren method is utilized to investigate the impact of water injection and ambient temperature on water spray and evaporation processes. The experimental results indicate that both control parameters show important effects on water injection and spray characteristics. The water injection and ambient pressure show significant impacts on steady-state flow quantity and cyclic water injection quantity, and the water injection and ambient pressure affect the evaporation ability of water vapor within the spray which leads to a different variation trend during the initial, developing, and developed water spray stages. The results of this work can be used as fundamental supplements for ICRC, steam assistant technology (SAT), and DWI-related ICEs experimental and numerical researches, and provide extra information to understand the DWI process within engine-relevant conditions. Full article

(This article belongs to the Special Issue Experimental and Numerical Analysis of Fuel Spray in Engines)

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