EXPERIMENTAL ANALYSIS OF MICROSCOPIC SPRAY PROPERTIES OF NONSTABILIZED WATER-IN-GASOLINE EMULSIONS USING SHADOWGRAPH IMAGING

Modelling and prediction of cavitation erosion in GDi injectors operated with E100 fuel

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.

The purpose of this research is to prevent the abnormal injection process in Gasoline Direct Injection (GDI) injector, realize accurate control of the fuel injection quantity and improve the performance of gasoline engine. The mechanical characteristics of the needle valve in a porous GDI injector is analyzed, the needle dynamics model is established, and the needle oscillation process is simulated with a mechanic-electronic-hydraulic integration method with the help of AMEsim software. The validity of the model is verified. The factors that influence the dynamics of the needle valve are analyzed. The results show that the dynamics of needle movement in GDI injector are mainly affected by the seat cone angle and the moving mass of the needle valve. The comprehensively improved structure of GDI injector is proposed based on the needle oscillation analysis. The simulation results show that the dynamic characteristics in GDI injector’s needle valve can be significantly improved with the optimized new structure. The experimental results of fuel injection flow characteristic and penetration distance show that the reliability and safety of the injector has been enhanced after structure optimization.

GDI (Gasoline Direct injection) injector is one of the most important components in GDI engine, which requires high precision and dynamic response. The magnetic circuit configuration as the key part of GDI injector which decides the magnetic force, dynamic response, energy loss and temperature risi ng. All these factors directly or indirectly impact on the GDI injector comprehensive performance. The aim of this investigation is to optimize the magnetic circuit configuration and improve the comprehensive performance for GDI injector. The specific factors that influence the optimum operation of the GDI injector have been analyzed based on physical theories. MOSA (Multi Objective Simulated Annealing) algorithm is used to implement the multi-objective parameters optimization for the magnetic circuit configuration. To validate the optimization results the multi-physical fields coupling simulation based on Finite Element Method (FEM) is used, and the simulation results were validated by experiments. Compared the initial configuration to the optimized one, the comprehensive performances have great improvement after optimization. The results indicate that the methods can be used to GDI injector concept design and performances prediction.

The spray structure and its developments generated by a multi-hole gasoline direct injection (GDI) have been investigated and discussed. Experiments were carried out on a constant volume chamber (CVC) rig. The effects of injection pressure, ambient pressure and ambient temperature were examined using high speed CCD camera. Images were processed by a specific program based on MatLAB. The spray tip penetration and overall spray cone angle were then analyzed and discussed. It was found that the spray penetration was mostly affected by ambient pressure and by injection secondly, while the ambient temperature slightly affected them both.

Spray morphology transformation of propane, n-hexane and iso-octane under flash-boiling conditions

Characterizing under-expansion behaviors induced by rapid phase change of flash-boiling jets

Experimental and numerical study of flash boiling in gasoline direct injection sprays

<div class="section abstract"><div class="htmlview paragraph">LEV-3 regulation changes require 100% SULEV30 fleet average by 2025. While present applications meeting SULEV30 are predominately small displacement 4-cylinder engines, LEV-3 standards will require larger displacement engines to also meet SULEV30. One concept previously investigated to reduce the cold start engine-out HC emissions was to heat the fuel injected during the cold start and initial engine idle period. Improved atomization and increased vaporization of heated fuel decreased wall wetting and unburned fuel. This resulted in more fuel available to take part in combustion, thus reducing the required injected fuel mass and HC emissions.</div><div class="htmlview paragraph">Single cylinder engine testing with experimental heated Gasoline Direct Injection (GDi) injectors was conducted at 40°C engine coolant and oil temperature conditions. The operating mode simulated cold start idle operating conditions, with split injection for improved Catalyst Light-Off (CATLO) times. Testing showed that fuel heating increased engine stability at leaner Air/Fuel (A/F) ratios. The leaner A/F ratio operation reduced emissions, particulates and smoke.</div><div class="htmlview paragraph">These results led to further investigations in a vehicle platform. The method of heating the fuel was altered due to hardware limitations, and pre-heating a fuel rail and GDi injector fuel coils were used to produce a representative fuel stream temperature profile, previously measured with experimental Heated GDi injectors. Heated versus unheated gasoline cold start emission performance was compared on a 3.8L 6-cylinder naturally aspirated vehicle which demonstrated a reduction in HC emissions using heated fuel.</div><div class="htmlview paragraph">The experimental GDi injectors, single cylinder test results, fuel heating methodology, vehicle installation, engine re-calibration, as well as comparisons of engine-out and tailpipe emissions produced with unheated and heated fuel are presented and discussed.</div></div>

Nowadays it has become particularly valuable to control the Particulate Matter (PM) emissions from the road transport sector, especially in vehicle powertrains with an Internal Combustion Engine (ICE). However, almost no publication has focused on a comparison of the microscopic characteristics of gasoline and ethanol spray under injection pressure conditions of more than 30 MPa, except in the impingement process. By using a Phase Doppler Particles Analyser (PDPA) system, the microscopic characteristics of gasoline and ethanol spray from a Gasoline Direct Injection (GDI) injector under injection pressure (PI) up to 50 MPa was fully explored in this research. The experimental results demonstrate that under the same PI, the second peak of the probability (pd) curves of droplet normal velocity for gasoline is slightly higher than that of ethanol. Moreover, gasoline spray exceeds ethanol by about 5.4% regarding the average droplet tangential velocity at 50 mm of jet downstream. Compared to ethanol, the pd curve’s peak of droplet diameter at (0, 50) for gasoline is 1.3 percentage points higher on average, and the overall Sauter mean diameter of gasoline spray is slightly smaller. By increasing PI from 10 MPa to 50 MPa, pd of the regions of “100 ≤ Weber number (We) < 1000” and “We ≥ 1000” increases by about 23%, and the pd of large droplets over 20 μm shows a significant reduction. This research would provide novel insights into the deeper understanding of the comparison between gasoline and ethanol spray in microscopic characteristics under ultra-high PI. Additionally, this research would help provide a theoretical framework and practical strategies to reduce PM emissions from passenger vehicles, which would significantly contribute to the protection and sustainability of the environment.

Characteristics of flash boiling and its effects on spray behavior in gasoline direct injection injectors: A review

Hydraulic flip in a gasoline direct injection injector and its effect on injected spray

Spray dynamics and atomization characteristics of multi-hole GDI injectors under flash boiling conditions

The purpose of this study is to investigate the overall spray behavior characteristics for various injection conditions in a gasoline direct injection(GDI) injector with multi-hole. The spray characteristics, such as the spray penetration, the spray angle, and the injection quantity, were studied through the change of the injection pressure, the ambient pressure, and the energizing duration in a high-pressure chamber with a constant volume. The n-heptane with 99.5% purity was used as the test fuel. In a constant volume chamber, the injected spray was visualized by the spray visualization system, which consisted of the high-speed camera, the metal-halide lamp, the injector control device, and the image analysis system with the image processing program. It was revealed that the injection quantity was mainly affected by the difference between the injection pressure and the ambient pressure. For low injection pressure conditions, the injection quantity was decreased by the increase of the ambient pressure, while it nearly maintained regardless of the ambient pressure at high injection pressure. According to the increase of the ambient pressure in the constant volume chamber, the spray development became slow, consequently, the spray tip penetration decreased, and the spray area increased. In additions, the circular cone area decreased, and the vortex area increased.

Spray characteristics of direct injection injectors with different nozzle configurations under flash-boiling conditions