Gasoline Direct Injection Sprays Research Articles

Acceleration of Modeling Capability for GDI Spray by Machine-Learning Algorithms

Cold start causes a high amount of unburned hydrocarbon and particulate matter emissions in gasoline direct injection (GDI) engines. Therefore, it is necessary to understand the dynamics of spray during a cold start and develop a predictive model to form a better air-fuel mixture in the combustion chamber. In this study, an Artificial Neural Network (ANN) was designed to predict quantitative 3D liquid volume fraction, liquid penetration, and liquid width under different operating conditions. The model was trained with data derived from high-speed and Schlieren imaging experiments with a gasoline surrogate fuel, conducted in a constant volume spray vessel. A coolant circulator was used to simulate the low-temperature conditions (−7 °C) typical of cold starts. The results showed good agreement between machine learning predictions and experimental data, with an overall accuracy R2 of 0.99 for predicting liquid penetration and liquid width. In addition, the developed ANN model was able to predict detailed dynamics of spray plumes. This confirms the robustness of the ANN in predicting spray characteristics and offers a promising tool to enhance GDI engine technologies.

CFD unified approach under Eulerian-Lagrangian framework for methanol and gasoline direct injection sprays in evaporative and flash boiling conditions

Innovative synthetic fuels for advanced propulsion systems, such as methanol and ammonia, and synthetic blended fuels (E00, E10, and E30), known for their high volatility, are often injected directly into combustion chambers. It follows that Eulerian-Lagrangian spray models need to accurately capture the spray collapse as a consequence of flash boiling onset and be capable of proficiently handling the preferential evaporation of multi-component fuels in evaporative scenarios.So, we performed the assessment of an Eulerian-Lagrangian CFD code for simulating methanol and E00 gasoline blend sprays in both early and late injection conditions involving flash boiling conditions and preferential evaporation. The adoption of an effervescent breakup model and of a non-equilibrium phase transition model for the discrete phase allows the adoption of a setup that is almost completely free from specific constant tuning, especially for what concerns the breakup model. We validated the simulations using experimental PLV maps of methanol and E00 sprays issued from the ECN Spray M injector. The results highlight a significantly different morphology of the methanol spray compared to the E00 one under late injection conditions. Under stratified combustion, low-volatile fuels are likely to be ignited first, and the flame propagates toward the high-volatile fuels. The spray collapse was also correctly reproduced, inducing the presence of a low-pressure zone and modifying the spray morphology.

Numerical studies of gasoline direct-injection sprays (ECN Spray G) under early- and late-injection conditions using Large Eddy Simulation and droplets-statistics-based Eulerian–Lagrangian framework

This paper presents an approach that uses Large Eddy Simulation under the Eulerian–Lagrangian framework to model the gasoline direct-injection (GDI) spray from Engine Combustion Network (ECN) multi-hole and counter-bore injectors. The approach considers the significant role that cavitation plays in primary atomization due to the counter-bore configuration. The local Weber number (We) and Reynolds number (Re) for GDI sprays are much smaller than those for a diesel spray, which renders conventional diesel spray approaches unsuitable. The proposed one uses a statistics-based droplet distribution function to address this and incorporates necessary information from a DNS inner-nozzle flow simulation. The corresponding models for drag, heat transfer, evaporation, and breakup consider the effects of viscous and distorted spray droplets. The approach has been applied to two different operating conditions, with simulation results that agree well with experimental data. Compared to the blob method assuming the ejected droplets are at the size of the injector diameter, the proposed CFD framework can reproduce a more accurate plume shape in the Spray G3 case. Applying the late-injection condition (Spray G1), the proposed approach improves the projected liquid volume (PLV) extinction compared to the blob method by providing a more accurate droplet evaporation prediction. These findings demonstrate the significance of the proposed approach for modeling GDI sprays and highlight its potential for future research in this area.

Macroscopic and Microscopic Characteristics of a GDI Spray Under Various Thermodynamic Conditions

Article Macroscopic and Microscopic Characteristics of a GDI Spray Under Various Thermodynamic Conditions Jian Li 1, Lulu Li 1, Rujie Xiao 1, Yuanfei Liang 1, Shuyi Qiu 2, and Xuesong Li 2,* 1 SAIC GM Wuling Automobile Co., Ltd., 18 Hexi Rd, Liunan District, Liuzhou 545001, China 2 School of Mechanical Engineering, Shanghai Jiao Tong University, 800 Dongchuan Road, Shanghai 200240, China * Correspondence: xuesonl@sjtu.edu.cn Received: 12 June 2023 Accepted: 9 August 2023 Published: 28 August 2023 Abstract: Gasoline direct injection (GDI) is the most common and advanced fuel supply strategy for gasoline engines. The fuel atomization quality and fuel/air mix degree determine the subsequent combustion efficiency and emissions. However, the engine works in complex conditions which have numerous thermodynamic boundary conditions, and the characteristics of fuel atomization also change accordingly. It is necessary to clarify the influence of various thermodynamic conditions on the GDI spray. In this work, three different types of optics diagnostic methods were utilized to capture the macroscopic and microscopic characteristics of a commercial GDI injector spray under various thermodynamic boundary conditions. Specifically, Mie-scattering photography was employed to get the macroscopic parameters; planar Mie-scattering photography was utilized to get the spray pattern; phase Doppler interferometry (PDI) was used to get the microscopic characteristic, i.e., the droplet size distributions. It is found from this study that higher injection pressure, lower ambient pressure, and lower ambient temperature would lead to longer penetration and larger plume width. Lower ambient pressure and higher ambient temperature would cause a smaller spray pattern. Higher injection pressure, lower ambient pressure, and higher ambient temperature would result in smaller droplet sizes.

Evaluation of GDI spray structures under flash boiling and strong collapse conditions with diverse fuels

GDI (Gasoline Direct Injection) sprays are a matter of continuous research due to their potential for higher thermal efficiency and power output. Injections in GDI engines tend to happen at relatively high temperatures, which, combined with volatile fuels, are a perfect environment for flashing sprays, which are present in recently developed GDI engine passenger cars. Phenomena like flash boiling and especially spray collapse are still being investigated due to their complexity and impact on the engine performance. In the present research, the impact of different levels of flash boiling in the sprays is analyzed. Four surrogate mono-component fuels were tested with different volatile properties. Two optical techniques were carried out simultaneously: light extinction images (DBI) and frontal MIE scattering. The spray width was used to represent the radial expansion and study its relation with the spray collapse due to flash boiling. The degree of collapse was quantified by means of the instantaneous spray width variation for which three levels of collapse were identified. A novel MIE frontal approach was employed to study the spray surface evolution and the collapsing time by monitoring the nozzle tip clouding (opaquing) by the fuel. Results showed an increment of the width with the ratio of saturation to ambient pressure (Rp), as well as a strong correlation between the spray surface and the Rp at each fuel temperature when the spray is stabilized. Based on the MIE technique, three collapse instants were identified throughout the injection time depending on the Rp.

High-speed low-coherence interferometry of fuel films in impinging gasoline direct injection sprays

Quantitative experimental characterization of dynamic fuel film deposition processes is critical to developing better understanding and modeling of cold-start behavior in gasoline direct injection engines. Low-Coherence Interferometry (LCI) offers a quantitative fuel film thickness diagnostic that is immune or resistant to major confounding influences that limit other optical diagnostics in engine-relevant environments. This work describes an extension of spectral LCI techniques to high-speeds (10 kHz) that are capable of resolving the dynamics of fuel film deposition and evaporation in impinging gasoline sprays. Two approaches to LCI, Michelson interferometry and Fizeau interferometry, were tested and results demonstrate the superiority of the Fizeau configuration for enclosed vessel experiments. Experiments were performed at cold start conditions in an enclosed spray chamber with a gasoline spray impinging on a transparent wall. High-speed LCI was used to measure fuel film thicknesses and dynamic changes in thickness. The measurements were used to observe variation in film thickness and behavior with changes in system temperature and fuel composition.

Numerical Simulation of Cavitation and FlashBoiling in GDI Nozzle and Spray

This work aims at using Computational Fluid Dynamics (CFD) method to establish a gasoline direct injection (GDI) engine nozzle and combustion chamber model to simulate cavitation and flash boiling phenomena and analyze how these phenomena affect the engine performance. FLUENT 15.0 is used to simulate the flow of fuel. The cavitation phenomenon in GDI nozzle was simulated comprehensively, and the influences of parameter values such as inlet pressure and outlet pressure on cavitation were studied in this work. The results show that high injection pressure can promote the occurrence of cavitation and high outlet pressure has an inhibitory effect on cavitation. However, the effect of cavitation on atomization cannot be seen intuitively only through the simulation of the internal nozzle. The two-dimensional inter nozzle model established in this work is a foundation for the establishment of external nozzle model. It can provide specific boundary conditions at nozzle outlet. In addition, a three-dimensional external nozzle model was established to simulate the flash boiling spray in the combustion chamber. Based on the mechanism, it can be found that flash boiling spray improves the atomization quality. After verifying the simulation results with relevant experiments, these models could bring great convenience to the study of cavitation and flash boiling with sufficient reliability in further study.

Spray–wall impingement in a multi-hole GDI injector for split injection at elevated wall temperature and ambient conditions

Post wall-impingement characteristics of pulsatile and split injection sprays in multi-hole Gasoline Direct Injection (GDI) are investigated. A combined experimental and numerical approach is adopted, to examine the influence of wall temperature as well as gas temperature and pressure on spray evolution. For fuel injection condition, split proportion and wall stand-off distance are not varied. The single injection case is also studied for comparison. The experiments were conducted under atmospheric conditions but for different wall temperatures, and the fuel spray was visualized using high-speed shadowgraph technique. The three-dimensional Eulerian–Lagrangian spray simulations were validated against the measured post-impingement plume width and height. Simulations were carried out to analyse spray–wall interaction process under elevated ambient temperature and pressure conditions also. Considerably smaller radial and vertical spread of the spray plume is obtained for split injection, highlighting its benefits over the single injection case. Both plume and wall film characteristics are strongly influenced by the ambient gas density and temperature rather than the wall temperature. However, time evolutions of the mass, thickness and temperature of the film are similar for both single and split cases at different operating conditions, exhibiting some interesting trends. For split injection, the vapour plumes from the two injection pulses interact. At high ambient temperatures, the peak equivalence ratio values are lower for split injection due to lower injected mass per pulse, in comparison to the single injection strategy. • GDI spray–wall interaction is investigated experimentally and computationally. • The measured post-impingement plume height/width corroborate well with the predictions. • The plume characteristics are primarily dependent on gas phase density. • The wall film thickness reduces considerably for split-injection compared to single injection. • For split-injection and elevated ambient temperature, the initial wall film vaporizes prior to 2nd injection.

Spray collapse characteristics of practical GDI spray for lateral-mounted GDI engines

Spray collapsing and plume merging processes were investigated using a lateral-mounted gasoline direct injection (GDI) injector with a practical 'triangular' spray pattern. High-speed diffusive back illumination extinction imaging followed by computed tomography reconstruction was applied to understand the spatiotemporal plume dynamics under engine-like conditions. The spray chamber and injector conditions include (1) cold, subcooled standard temperature and pressure (STP) used by the injector manufacturer, (2) practical gasoline fuels with full-range distillation, (3) flash-boiling with fuel temperature and vacuum gas pressure, and (4) high gas pressure and temperature typical of injection during compression. The novel experiments permit tracking of plume merging at different times and axial distances downstream of the nozzle. A triangular 6-hole pattern, which is widely used in lateral-mounted GDI engines, was found to be prone to having the centrally located plumes move close to each other thus leading to spray collapse with these plumes at all practical test conditions (2)–(4). Variations of air entrainment and local pressure with different conditions were identified as dominant factors for the timing and position of spray collapse.

High-speed low-coherence interferometry for film thickness measurements in impinging gasoline direct injection sprays

High-speed low-coherence interferometry for film thickness measurements in impinging gasoline direct injection sprays

A zonal secondary break-up model for 3D-CFD simulations of GDI sprays

In Gasoline Direct Injection (GDI) engines, the secondary break-up plays a significant role in air–fuel mixing. In fact, spray granulometry affects evaporation rate, liquid penetration and plume morphology. Operating pressures and temperatures of both liquid and gaseous phases strongly influence the droplet disruption mechanism in the combustion chamber. In 3D Computational Fluid Dynamics (CFD), several models can be adopted to simulate the secondary break-up process, among which the Reitz-Diwakar and the Kelvin-Helmholtz Rayleigh-Taylor (KHRT) are the most diffused ones in the engine community. However, application of such models in their original versions is limited to a reduced range of injection parameters and ambient conditions. As a matter of fact, large variations of them usually require ad-hoc calibrations of the model constants. To improve the predictive capabilities and reduce the need of case-by-case tuning, an alternative secondary break-up model is proposed in the present paper. It is based on the Reitz-Diwakar one but, compared to the latter, a zonalization of the break-up regimes is proposed. Specifically, it is assumed that only Stripping break-up can occur near the nozzle, while Bag break-up only takes place sufficiently far from it. Moreover, model parameters are now treated as functions of the operating conditions. In particular, the impact of the ambient density on the model parameters is analysed in the present work. The proposed model is calibrated via constant volume vessel simulations on a single-hole GDI research injector at vacuum-to-pressurized conditions (namely at 0.4, 1.0, and 3.0 bar(a) of back pressure), on equal temperature. Model parameters are found to be linear functions of the ambient density. Thereafter, model validation is carried out on two different GDI injectors. The first is again a single-hole (remarkably different compared to the previous one), while the second is a 5-hole prototype. Numerical results provided by the proposed model show a satisfactory agreement compared to the experiments in terms of liquid penetration, Phase Doppler Anemometry (PDA) data and imaging, without any dedicated tuning. Conversely, the Reitz-Diwakar and KHRT models, applied to simulate (with default calibration constants) the same injectors, provide results which remarkably deviate from the experiments.

Investigation of the effects of cavitation on near nozzle dynamics in multi-hole gasoline direct injection sprays

Investigation of the effects of cavitation on near nozzle dynamics in multi-hole gasoline direct injection sprays

The effect of the divergent-convergent GDI injector on inner flow and spray characteristics at high injection pressure

ABSTRACT The effects of Divergent-Convergent (D-C) nozzle parameters on the inner flow and spray characteristics of GDI (Gasoline Direct Injection) injector were studied under the condition of high injection pressure of 40 MPa. Homogeneous Relaxation Model (HRM) was used to explore the GDI orifice inner cavitation flow and nozzle exit flow parameters. A one-way coupled spray model was adopted to study the GDI spray behaviors. From these results, the cavitation density in the orifice decreases with the increase of the medium diameter ratio Km, while the discharge coefficient and the orifice exit velocity increases with the increase of Km. Moreover, the nozzle exit average velocity increases with the increase of Xm, and the nozzle exit average velocity with the Km of 1.5 is about 14.1% larger than that of the cylindrical nozzle. While the changing of the Xm has no effect on the nozzle exit average velocity for the same median diameter ratio. Additionally, the turbulent kinetic energy at the nozzle exit decreases with the increase of Km, especially the turbulent kinetic energy for the D-C nozzle with Km of 1.5 is about 17.1% smaller than that of the cylindrical nozzle. In addition, the D-C nozzle with Xm of 0.5 held the smallest turbulent kinetic energy. Also, the Sauter Mean Diameter (SMD) decreases with the decrease of Km at the initial injection stage. However, the spray SMD increases with the decrease of Km, and the SMD decreases with the increase of Xm at the late injection stage. Furthermore, the SMD of D-C nozzle is smaller than that of the cylindrical nozzle at the late injection stage.

Study of spray structure from non-flash to flash boiling conditions with space-time tomography

Flash boiling and plume interaction are common phenomena occurring in gasoline direct injection (GDI) spray at throttling and low load engine conditions. Combined with optical engines and low-pressure vessels, several optical techniques, such as backlight imaging, Mie-scattering, and laser sheet imaging have been employed to study the flash boiling morphology. However, in the 2D images resulting from these techniques (projection views or planar imaging), the 3D information is lost. Those methods are then incapable of providing satisfactory information, especially for the study of multi-plume interaction in flash boiling spray, since multi-plume interaction is not a 2D event. This paper reports the implementation of a 4D tomographic reconstruction method from multi-view diffused back illumination (DBI) images, used for the first time in spray characterization. This cost-effective and time-saving method with a simple experimental setup clarifies the 3D spray structure and fuel trajectory change from non-flashing conditions to flare flash conditions, and quantifies the 3D characteristics of individual plumes in non-flash conditions.

Experimental Analysis of Gasoline Direct Injection Spray Characteristics by Mixing with High-boiling Component Fuel

Experimental Analysis of Gasoline Direct Injection Spray Characteristics by Mixing with High-boiling Component Fuel

Elucidation of Gasoline Direct Injection Spray Characteristics by Mixing with High-boiling Component Fuel (First Report)

Elucidation of Gasoline Direct Injection Spray Characteristics by Mixing with High-boiling Component Fuel (First Report)

高沸点成分燃料の混合による直噴ガソリン噴霧特性の評価（第2報）:―燃料噴射差圧が噴霧の微粒化特性に及ぼす影響の解明―

高沸点成分燃料の混合による直噴ガソリン噴霧特性の評価（第2報）:―燃料噴射差圧が噴霧の微粒化特性に及ぼす影響の解明―

An investigation on the impact of small-scale models in gasoline direct injection sprays (ECN Spray G)

The work presents a numerical investigation of gasoline direct injection and the resulting early development of spray plumes from an eight-hole injector (Engine Combustion Network Spray G). The objective is to evaluate the impact on the droplet size distribution (DSD) statistics from the assumed model physics, particularly for the small scales. Two modelling approaches are compared: Eulerian–Lagrangian spray atomisation with adaptive mesh refinement and a stochastic fields transported probability density function method. The two models simulate the small scales and sub-grid droplet physics with different approaches, but based on the same concept of transport of liquid surface density. Both approaches predict similar liquid distributions in the near-field comparable to experimental measurements. The spray break-up patterns are very similar and both models reproduce quasi-log-normal droplet distributions, with same overall Sauter mean diameters. The Eulerian–Lagrangian spray atomisation with probability density function approach shows different break-up behaviour between droplets originating from the dilute region and those originating from the dense core region. The transition from Eulerian to Lagrangian can be observed in the Eulerian–Lagrangian spray atomisation with adaptive mesh refinement predicted distribution with an abrupt change in the DSD. Both methods are able to produce similar DSD below filter width/grid size resolution.

Dynamic Thermal Behavior of a GDI Spray Impacting on a Heated Thin Foil by Phase-Averaged Infrared Thermography

<div class="section abstract"><div class="htmlview paragraph">The regulations about pollutant emissions imposed by Community’s laws encourage the investigation on the combustion optimization in modern engines and in particular in those adopting the gasoline direct injection (GDI) or direct injection spark-ignited (DISI) configuration. It is known that the piston head and cylinder surface temperatures, coupled with the fuel injection pressure, strongly influence the interaction between droplets of injected fluid and the impinged wall. In the present study, the Infrared (IR) thermography is applied to investigate the thermal footprint of an iso-octane spray generated by a multi-hole GDI injector impinging on a heated thin foil. The experimental apparatus includes an Invar foil (50 μm in thickness) heated by Joule effect, clamped within a rigid frame, and the GDI injector located 11 mm above the surface. Thermal images of the impinging spray are acquired from the dry side of the foil at several time delays after the impact instant at two different injection pressures (10 and 20 MPa). The temperature difference distributions are employed to describe the unsteady dynamics of the impingement.</div></div>

Characteristics of the deposited fuel liquid film when GDI spray impacts viscous oil film

Quantitative two-dimensional characteristics of the deposited fuel film on a surface with pre-existing thin oil film after the impingement of a GDI (gasoline direct injection) spray were investigated with laser induced fluorescence (LIF) technique. Since the oil and the incident test fuel could mix during impingement, we examined the theory of the LIF technique and found it could no longer provide information on the mixture thickness but could still help us measuring the mass of the deposited fuel. Mixture of isooctane and 3-pentanone was chosen as the test fuel and silicone oil of different viscosity was selected as the surrogate liquid for the oil to eliminate disturbing LIF emission. The sprays with injection pressure from 7 to 15 MPa, injected mass from 2.9 to 6.4 mg were tested, the pre-existing oil film with viscosity of 10 and 100 cSt and thickness between 10 and 50 μm were studied. A lower fuel mass deposited ratio was found under higher injection pressure and thinner oil film, while the effects of the injected mass and viscosity of oil viscosity were found to be more complicated and were analysed with the help of single drop experiments from literature.