Gasoline Direct Injection System Research Articles

Low-pressure gasoline direct injection system development and emissions analysis for a reciprocating two-stroke engine

This study presents the design and construction of an electronic low-pressure gasoline direct injection system for two-stroke engines, with the objective to study engine performance and the emission of exhaust polluting gases, maintaining the expectations of this type of engine. The investigation includes a test bench with an incorporated engine and the required control devices for this, as well as a gas analyzer Class 0, a computerized data acquisition and several tools for displaying and process all the electronic signals from the engine in real time. In order to manage this system, a custom electronic injection control unit has been designed and built, which allows to control the fuel injection timing and duration. This unit uses the signal from an inductive sensor installed in the crankshaft as a reference and synchronization point. Additionally, modifications have been made to the fuel feeder circuit and the electronic of the test engine, as well as to some parts of the mechanism in order to adapt them to this technology. The implementation of the engine tests is described, and the performance and operational points of the original system and those of the new injection system are evaluated.

Experimental analysis of the near-nozzle direct injection spray for gasoline and ethanol-gasoline blended fuels

The current work analyses the spray during the early stage of development in the near-nozzle region using a single-hole gasoline direct injection system for gasoline (G100) and ethanol-gasoline (E85) blended fuels. The present work combined a Galilean-type beam expander with an achromatic lens, using an LED light and a high-speed camera to visualize a magnified view of the near-nozzle microscopic aspect of the emerged jet. Three different shapes, spheroids, cylindrical, and steeple, were visualized experimentally during the evolution of the fuel jet under different fuel injection and chamber pressures. A transition in shape from the steeple-to-spheroid shape was detected. It was observed that the velocity of the emerged jet is affected by its evolved shapes, attributing to differences in the initial breakup characteristics and shot-to-shot variation in the spray at a given condition. The velocity of the cylindrical-shaped jet was 14% and 42% higher than the steeple and spheroid-shaped jets, respectively. The Rayleigh-Plesset equation describes the reason for an increase in the spheroidal-shaped jet velocity by 84% when the chamber pressure is reduced from 0.6 to 0.1 MPa. The Ohnesorge and Reynolds number of the emerged liquid jets were estimated to describe the breakup regime of the jet during the initial stage. It was observed that the cylindrical and the steeple-shaped jets pertain to a higher tendency to atomize during the initial stage of evolution compared to the spheroidal jet. The average jet velocities and liquid penetrations in the near-nozzle region for E85 and G100 were estimated.

Laser ignition and flame propagation of methanol-air mixture in a constant volume combustion chamber

ABSTRACT The combustion performance of laser-ignited methanol-air mixture in a constant volume combustion chamber was investigated using the Schlieren photography technique. The experimentation was conducted at 5, 7, 9, and 11 MPa fuel injection pressure and 363 K initial chamber temperature using a neodymium-doped yttrium aluminum garnet (Nd:YAG) laser of 1064 nm wavelength. The gasoline direct injection (GDI) system was used for injecting the fuel at different pressures inside the chamber. The laser beam is focused into the chamber using a 150 mm focal length lens, and laser energy of 200 mJ was used for all experimentation. The Schlieren system was used for capturing flame propagation of methanol-air mixture for different equivalence ratios. The pressure-time history for equivalence ratio (ϕ) of 0.8, 0.9, and 1.0 was plotted and analyzed at different chamber filling pressures. Flame propagation was found faster for ϕ of 1.0 due to higher laminar velocity than 0.8 and 0.9. Flame visualization showed that the flame attains the ellipsoid shape during the early stage of ignition. It generates two lobes in the vertical direction and then again expands in a horizontal direction toward the ignition source. For all equivalence ratios, the flame propagation toward the incoming laser source (X-) was observed faster compared to the flame propagation in the direction and perpendicular to the laser beam direction. For all equivalence ratios, higher laminar flame speed was observed at 5 MPa injection pressure; however, it decreases as the injection pressure increases. At ϕ of 1.0 and 11 MPa injection pressure, the maximum peak pressure of 0.67 MPa and combustion duration of 19.3 ms were noted. At 9 MPa injection pressure and ϕ of 1.0, the peak pressure and combustion duration was found as 0.61 MPa and 19.4 ms, respectively. At ϕ of 0.8, the peak pressure and combustion duration were observed 0.27 MPa with 34.6 ms duration and 0.47 MPa with 36.9 ms duration at 5 MPa and 11 MPa injection pressures, respectively.

On Modeling of Spray G ECN Using ROI-Based Eulerian-Lagrangian Simulation

A numerical study has been carried out to understand the effects of Unsteady Reynolds Averaged Navier-Stokes (standard k ― ε and RNG k ― ε model) and large eddy simulations (LES) on a multi-hole gasoline direct injection (GDI) system. The fuel injector considered in this study is the Spray G nozzle from the Engine Combustion Network (ECN). A blob injection model, based on empirical rate of injection (ROI) profile, is considered in this study. The latest data on spray penetrations from Engine Combustion Network is used for model validation along with experimental findings on suction velocity and local droplet diameter. The spray breakup is simulated by using the KH-RT breakup length model. The turbulence model constant Cε1, is tuned to match with the experimental data of liquid and vapor penetrations in simulations while using the standard k-ε turbulence model. On the other hand, the Kelvin-Helmholtz breakup model time constant (B1) and Rayleigh Taylor breakup length constant (Cbl) are tuned for the RNG k ― ε turbulence model. From this work it is observed that by increasing the breakup length model constants (Cbl), the radial dispersion of the spray increases, and the extent of breakup is lowered. The set of optimized model parameters used with RNG k - ε is also used for LES modeling studies with different sub-grid models. The spray penetrations with standard k ― ε turbulence (Cε1=1.44) model are reported underpredicting, and the RNG k ― ε and LES sub-grid models predicted well with the latest and recommended data from ECN. In terms of gas axial velocity comparison, the standard k-ε(Cε1=1.44) simulation setup does not perform as well as the simulation setups using RNG k-ε and LES turbulence models (with breakup parameters: Cbl = 16 and B1 = 32). However, the standard k-ε(Cε1=1.44) simulation setup perform better than the simulation setups using RNG k-ε and LES turbulence models (with breakup parameters: Cbl = 16 and B1 = 32) when it comes to predicting local droplet diameter at 15 mm downstream of the injector tip. A parametric study is also performed considering the geometry of the stepped holes in the computational domain. The rate of injection based simulation is initiated at the end of the smaller hole. The case including the stepped holes led to over-prediction compared to the case with the usual computational domain (i.e., without the stepped holes), in terms of spray penetrations, but exhibited higher levels of fluctuations in the spray morphology. Finally, parametric studies were carried out to understand the relative importance of the individual spray sub-models (breakup, evaporation and collision) and the results are conclusive that for a spray simulation the breakup models are the dominant factors.

Comparison of ethanol/diesel fuel dual direct injection (DI2) strategy with reactivity controlled compression ignition (RCCI) in a diesel research engine

The dual direct injection (DI2) strategy is expected to cover the advantages of conventional diesel (CDI) mode while avoiding deficiencies of reactivity controlled compression ignition (RCCI) strategy such as high amount of incomplete combustion emissions and extremely high rate of pressure rise. Therefore, the present study focused on the comparison of combustion characteristics of these combustion modes in a diesel research engine, which was firstly operated under CDI mode at varying loadings and a constant speed of 2400 rpm to establish the reference data. Then, a low pressure port fuel injection (PFI) and high pressure gasoline direct injection (GDI) systems were activated to run on RCCI and DI2 modes, respectively, whereas test engine was already equipped with a common-rail direct injection (CRDI) system for conventional diesel fuel injection. Results showed that both direct and port injection methods increased the in-cylinder pressure (up to 9%) compared to conventional mode. In RCCI combustion, the rate of pressure rise increased more than direct injection and conventional mode. CDI exhibited higher thermal efficiency than RCCI and DI2 modes while both advanced modes were successful in reducing NOx and Smoke Opacity. However, significantly higher CO and unburned HC emissions were observed with both advanced modes in comparison to conventional one. Both CO and unburned HC emissions were reduced by direct injection of ethanol (DI2 strategy) at the rates of 16% and 35% compared with port injection method of RCCI strategy. This is an important finding of this study, which shows that the DI2 strategy has a potential to address a deficiency of RCCI and will bring it closer to its application to practical engines.

Modeling the spray characteristics of blended fuels for gasoline direct injection applications

ABSTRACT Methanol and ethanol are considered as potential candidates for alternative fuels in spark-ignited engines and flex-fuel vehicles. Alcoholic fuels have higher latent heat of vaporization (), lower boiling-point temperature and higher-octane numbers help the engine run under higher compression ratios, resulting in better efficiency and fuel economy. A numerical study is carried out to understand the spray-breakup and vaporization characteristics of binary blended fuel and ternary fuel blend compared to single-component fuel for gasoline direct injection (GDI) system. Multiple simulations were carried out by substituting individual fuel properties of isooctane with those of ethanol to understand the relative importance and effect of fuel properties on spray characteristics. The spray characteristics of pure isooctane fuel and their blends with ethanol and methanol are studied and compared, and the charge cooling effects for alcoholic fuels have been observed. The Spray G operating condition has been taken from the Engine Combustion Network (ECN) for this study. The simulated data for isooctane has been validated with the experimental data from the ECN, and a similar model setup has been used for pure and blended fuel sprays. The discrete-phase modeling (DPM) approach is carried out, and the Unsteady Reynolds-Averaged Navier–Stokes (URANS) RNG (Renormalization) k-ε turbulence model is considered in understanding the spray characterization. The blended methanol fuels have higher penetration lengths compared with ethanol ones. The penetration of the blended fuels (binary and ternary) is slightly lower than the isooctane. The ternary blends showed spray characteristics similar to those of E85, and it indicates that the ternary blended fuel has the potential to be used as a drop-in fuel for a GDI-based flex-fuel vehicle.

Study of the hydraulic characteristics of two injectors fed with different fuels in a GDI system

In the latter years, the Gasoline Direct Injection systems (GDI) have been studied with the aim of providing a solution to the particulate matter emission issue. It has been proved that emission levels are reduced with the tuning of certain variables, such as the injection pressure, that affect the internal flow in the nozzle, which in turn plays an vital role in the spray development. On the other hand, the implementation of fuels such as alcohols and some surrogates shows potential for improving the engine performance and emissions because of the different physical properties of the fuels that can alter the mixture formation and the chemical properties that affect the combustion. In this work, an experimental study of the influence of different fuels on the internal flow is realized for a vast number of conditions, including those that promote flash boiling and strong collapse of the spray at different ambient temperatures and pressures. The fuels employed are three components of gasoline: iso-octane, n-hexane and n-pentane; ethanol; and two blends (E00 and E20) for two nozzle geometries. Two experimental techniques are used to measure the mass flow rate and momentum flux of the spray, and then characterize the flow inside the nozzle. The results show a similar injector behavior for all fuels, except for the ethanol, which shows an increase in the rate of injection and induces a hydraulic delay.

Process optimization for hot forging of difficult parts by computer experiments and response surface analysis

Closed die hot forging of 304L stainless steel is difficult compared to carbon and micro-alloyed steels in terms of higher forming force and defects. An appropriate combination of design and process factors including cross-section diameter, initial billet temperature, and flash land thickness is crucial to minimize the forming force without causing any under-filling or folding defects. This paper aims to develop an optimized closed-die hot forging process for long, thin, and tubular rail body components used in gasoline direct injection systems. The effects on the forging load are investigated using computer experiments containing the finite element method under a full factorial array of three factors at three levels to obtain the main and interaction effects. Linear and quadratic surface response analyses are performed to define the relation between forging load and input factors, and finally, the simulations are validated with some limited experiments. The simulation results that fit the nonlinear regression model were in close agreement with the experiments, and an optimal set of parameters is conveniently proposed for industrial production.

A Study on Gasoline Direct Injection (GDI) Pump System Performance using Model-Based Simulation


 
 
 This paper focuses on a simulation study of a newly developed high-pressure fuel pump system for small engine. When an engine is operated at high speed in a typical Gasoline Direct Injection (GDI) system, its pump will perform extra pumping requiring continuous engine work. Because it is driven by the engine’s camshaft, the extra pumping action is both unavoidable and parasitic. In this study, a new GDI pump has been designed and built to only operate at a constant speed, regardless of engine load and speed. The pump is driven by an electric motor via a camshaft and is intended for a four-stroke, 0.2 litre, single-cylinder, spark ignition engine. The electric motor is governed by a control unit called the Engine Control Unit (ECU). The GDI pump will supply fuel to a rail up to its maximum pressure capacity. The pump is developed in accordance with a physical model-based design approach and is simulated using Matlab- SimscapeTM. Based on the calculation and simulation performed, the designed pump pressure is capable of producing discharge exceeding 4.5 MPa. Theoretical calculation also shows that the pressure developed by the pump reaches 10.54 MPa when a two lobe cam is used. In addition, the pressure developed by the pump is recorded to be 11.15 MPa, with an error of 5.8 % when a similar condition is applied to the physical modelling.
 
 

Spark ignition engine performance, standard emissions and particulates using GDI, PFI-CNG and DI-CNG systems

Gaseous fuels, e.g., natural gas, biogas, have several advantages over liquid fuels owing to their favorable physical and chemical properties, e.g., lower carbon numbers in the fuel composition and no issues regarding fuel evaporation. The present study investigated compressed natural gas (CNG) port fuel injection (PFI) and direct injection (DI) systems compared to gasoline direct injection (GDI) cases in a spark ignition (SI) naturally aspirated single cylinder engine at stoichiometric conditions. The tests included usual engine working points – from 4.5 bar IMEP to 9 bar IMEP engine load at different engine speeds – from 1500 rpm to 2500 rpm. The main aim was to investigate how gaseous fuels can improve the SI engine efficiency, reduce standard emissions and particulates, and explain the benefits of a natural gas DI system versus standard gas PFI and GDI systems. Analysis of the results showed that the rate of heat release of natural gas was lower than that of gasoline fuel. However, the stable combustion process of DI-CNG gave additional benefits, e.g., increased turbulence in the cylinder, which increased the combustion rate and affected the exhaust gas formation. The highest engine efficiency was achieved with the same natural gas DI system. The highest iSHC, iSCO, iSCO2 and iSNOx emissions reduction achieved at low and part load conditions with DI-CNG compared to GDI combustion. Particulates formation was lower with the gaseous fuel compared to gasoline. Additional benefits of lower particulate numbers among three injection systems were observed with DI-CNG combustion.

定常過渡における PM/PN 排出低減に向けた燃料噴射系の開発

定常過渡における PM/PN 排出低減に向けた燃料噴射系の開発

Experimental study of spray behavior and laser ignited combustion characteristics of a gasoline-air mixture using the GDI system

This study focuses on the spray behavior and combustion characteristics of laser ignited gasoline-air mixture. A gasoline direct injection (GDI) system was used to inject the gasoline-air fuel mixture with high injection pressure into a constant volume combustion chamber. This high-pressure injection helps to improve the mixing quality and atomization, which further enhances the combustion process. The spray characteristics were studied for the injection pressures of up to 11 MPa in steps of 2 MPa, injection duration 1 to 5 ms, and a chamber pressure of 0.1 to 0.7 MPa. The maximum spray penetration length was found at 11 MPa injection pressure. The dependence of spray characteristics was found dominant on injection pressure compared with the injection duration. The experimental results were validated with CFD simulations. The empirical correlation was developed for spray penetration length, which was further used to calculate the spray penetration length for the gasoline-air mixture's laser combustion. The laser combustion was done at all the injection pressure ranges to study the effect of injection pressure on combustion peak pressure. An increase in peak pressure was found with an increase in injection pressure. The combustion peak pressure and the net heat release were found maximum for ϕ = 1, reducing lean and rich mixture conditions.

Low-Pressure Injection of Water and Urea-Water Solution in Flash-Boiling Conditions

<div class="section abstract"><div class="htmlview paragraph">The flash-boiling effect in sprays has been shown to have the capability to decrease droplet diameters and spray penetration, as well as improve the vaporization process in gasoline direct injection systems. It has also been shown that in certain conditions, the effect on spray penetration can be the opposite. Under a high degree of overheating the spray collapse effect may appear and lead to increased spray penetration - flare flash boiling. Moreover, when the boiling is already strongly present in the nozzle it may lead to flow choking. Thus, the process is difficult to be controlled. While most studies so far have focused on high-pressure direct injection systems, we investigate the process in a low-pressure system to verify if the effects observed in high-pressure systems will be similar. The study was performed on two liquids, water and a urea-water solution, to limit any individual substance’s effects on the results and to improve the practical importance of the study. The results showed no increased penetration in any of the flash-boiling cases, although at the highest considered temperatures the two plumes tend to form a single spray cloud. Although the characteristics were similar for both studied liquids, in certain measurement conditions the differences in almost all analysed spray parameters were considerable. Moreover, the study has shown that the flash-boiling effect can be considered as an effective way to improve jet and droplet break-up while avoiding a pressure increase in low-pressure injection systems.</div></div>

Rail Pressure-based Diagnostic Functions for Gasoline Direct Injection Systems

Rail Pressure-based Diagnostic Functions for Gasoline Direct Injection Systems

Effects of spray behavior and wall impingement on particulate matter emissions in a direct injection spark ignition engine equipped with a high pressure injection system

The effects of injection pressure on spray behaviors governing particulate matter emissions were investigated for various injection timings and engine loads in an optically accessible single cylinder engine equipped with gasoline direct injection system. In a spray visualization and particle number (PN) measurement experiment, injection timing and engine load were varied to examine their effects on the spray behavior including cylinder wetting that causes the emission of particulate matter. The analysis was based on the time-averaged spray images, spray variations between the cycles, combustion, and PN emission characteristics. The spray structure in the cylinder under the engine operating conditions used in the present study was a collapsed spray that was evident at high pressure injection under atmospheric conditions. For an injection timing of before top death center (BTDC) 300 deg, at the initial stage of the intake process, the magnitude of spray deflection formed by the in-cylinder flow interacting with the spray in the reverse direction increased owing to the high pressure injection promoting fuel atomization and increasing the effects of the in-cylinder flow. The spray variations between the cycles caused by the in-cylinder flow in the region of spray deflection were also increased by high pressure injection. When the weak in-cylinder flow was formed in the late intake process (BTDC 210 deg), increasing the injection pressure accelerated the initial droplet velocity and increased the amount of fuel reaching the cylinder wall opposite the injector, thus increasing the wall film and PN emissions. In contrast, for the conditions under which the wall film was formed on the piston top by fuel interaction, the large droplet momentum corresponding to high pressure injection increased in the amount of rebounded droplets at collision, thereby reducing the amount of wall film and PN emissions.

An experimental study for effect factors of the roller tappet induced impact noise in high-pressure fuel system of GDi engine

With the wide application of gasoline direct injection system, its noise problem is becoming increasingly prominent under serious competitive environment. As the primary noise source of the engine in idle condition, the significant noise generated by the low-to-high pressure transmission part of high-pressure fuel pump becomes more and more serious. This paper focuses on the driving component of high-pressure fuel pump, the roller tappet, and experimentally studies effect factors of impact noise induced by it at engine idle. Both the impact occurrence time and position are analyzed from the combined vibration acceleration and crankshaft/camshaft rotation angle signals in the time domain according to the structure and kinematic mechanism of the roller tappet. The influences of the axial clearance between roller and tappet shell, the engine rotation speed and the lubrication conditions are investigated by experiments. The experimental results show that the lubrication is the primary factor for the roller tappet induced impact noise reduction. A significant improvement about 83% can be achieved under pressure lubrication.

Comparative Investigation of Gaseous Emissions and Particle Emission Characteristics from Turbo-Charged Direct Injection (DI) Engine with Gasoline and LPG Fuel Depending on Engine Control Parameters

To meet greenhouse gas (GHG) emission target, automotive manufacturers should promote low carbon emission technology, including gasoline direct injection (GDI) systems. However, recent studies have shown that excessive levels of nanoparticles were emitted from GDI vehicles compared to port fuel injection (PFI) vehicles. One of the many ways to decrease nanoparticle emissions from GDI engine is to use alternative fuel This study used turbo charged 2.0 L 4-cylinder LPG direct injection engine (T-LPDi) that was converted from a turbo charged gasoline direct injection engine (T-GDI) with dedicated LPG fuel supply and control system. To analysis on combustion phenomena and nanoparticle emissions, in-cylinder pressure and exhaust gas were measured under engine dynamometer test. Additionally, various engine control parameters were swung to understand the effects of the control parameters on combustion and nanoparticle characteristics. Throughout this study, T-LPDi engine, compared to T-GDI engine, showed ∼ 9 % and 76 % reduction of CO2 and PN emissions respectively. By optimizing engine parameters based on parametric study, PN emissions were improved 70 % from the baseline of T-LPDi engine emissions.

Parameter and Design Analysis for Gasoline Direct Injection Injector using CFD and Design of Experiments

Numerical modeling of internal nozzle flow can be regarded as an essential investigation in the field of gasoline direct injection system of combustion engines since it is directly connected with fuel spray atomization and subsequently efficiency of exhaust gas emission. Internal nozzle flow can be changed and formed according to several parameters such as; system pressure, chosen fuel type, the orientation of spray holes according to injector axis, conicity of spray holes and distribution of spray holes on valve-seat, etc. The changes in these parameters also affect the formation of cavitation inside of whole domain, spray angle and create wall-wetting on the spray hole surfaces. The present work investigates the parameter and design analysis in the valve-seat region of direct gasoline injection (GDI) injector using Computational Fluid Dynamics (CFD) and Design of Experiments (DOE). CFD is employed to study the behaviors of internal flow inside the valve-seat region according to several design parameters, whereas a mixed-level factorial design is used to test the significance of the effects on the response variables. In conclusion, the effects of the most significant factors on response parameters as amount of vapor formation, spray (Tau) angle, and pre-hole wall wetting are determined for further efficient design.

Investigation of water injection benefits on downsized boosted direct injection spark ignition engine

Engine downsizing and boosting are key technologies to achieve the increasingly stringent emissions standards for spark ignition (SI) engines. However, knock is a major obstacle inhibiting further downsizing of SI engines. Water injection is a promising technology that has regained attention recently to solve the knock problem. In this paper, a 1.5L turbocharged gasoline direct injection (GDI) engine was modified by installing a water port injection (WPI) system on the intake manifold. The WPI system was modified from a GDI system and deionized water was pressured to 50 bar in a water tank by compressed nitrogen. The effect of WPI on engine combustion and emissions performance were experimentally investigated under different water/gasoline volume percentages and WPI timings. The results show that WPI has great potential in suppressing engine knock. At original engine setting (without adjustment of spark timing), all the combustion indexes related to knock are decreased by WPI, including maximum in-cylinder pressure (Pmax) and maximum pressure rise rate (Rmax). The flame kernel formation process (CA0-5), initiation combustion duration (CA0-10), early combustion duration (CA0-50) and major combustion duration (CA0-90) are deteriorated, resulting in decreased indicated mean effective pressure (IMEP) and thermal efficiency. By properly advancing spark timing, the combustion process can be improved, allowing the engine to achieve higher Pmax and better combustion phases without occurrence of knock. It is also found that the water/gasoline volume percentage should be kept within a proper range (30% in this study) because over WPI can lead to deterioration of combustion and pollutant emissions. WPI can effectively reduce the production of NO and CO emissions, while HC emissions are increased with the rise of water/gasoline volume percentage.

Effects of second injection timing on combustion characteristics of the spark ignition direct injection gasoline engines with dimethyl ether enrichment in the intake port

Dimethyl ether (DME), as a sustainable fuel, could be used as an ignition improver in spark ignition engines to improve the performance under lean conditions. Direct injection engines could gain higher thermal efficiency than the port fuel injection engines. To study the effects of second injection (SOI2) timing on the engine combustion characteristics, experiments were conducted on an engine with independent DME port injection and gasoline direct injection systems. Tests were performed at a constant engine speed of 1400 rpm and manifolds absolute pressure of 60 kPa under excess air ratios of 1.2 and 1.3. The start of injection during intake was kept constant at 300 oCA BTDC and the SOI2 timing was varied from 90 to 150 oCA BTDC. Split injection ratio was 1:1. Results showed that a higher brake thermal efficiency (BTE), lower cyclic variation, HC and particle emissions were obtained for DME-gasoline blends engines. Moreover, the ideal SOI2 timing could make the heat release more concentrated and ease the cyclic variation, which enhance BTE and reduce HC, NOx and particle number emissions. In addition, when more fuel was obtained, the combustion temperature was increased, improving BTE and reducing HC emissions under lean combustion conditions.