Direct-Injection Gasoline Engines

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Spray characteristics of a multi-hole injector for direct-injection gasoline engines

Spray characteristics of a multi-hole injector for direct-injection gasoline engines

The sprays generated from multi-hole injectors, introduced recently in spray-guided direct injection gasoline engines, have been characterised in terms of droplet velocities/diameters at injection pressures of 120 and 200bar and chamber pressures varying from atmospheric to 12bar. Additional spray visualisation has confirmed that the spray angle remains constant and is almost independent of injection and chamber pressure, a significant advantage relative to pressure-swirl atomisers used in the first-generation, wall-guided gasoline engines. The internal nozzle flow and the near nozzle spray characteristics have been estimated by employing a combination of computer models. Those comprised a 1-D model simulating the flow inside the injection system, a 3-D Navier-Stokes equations flow solver simulating the sac-volume and injection holes and a phenomenological nozzle hole cavitation. In addition, a cavitation-induced atomisation model was used to provide estimates of the liquid velocity increase due to hole cavitation and the corresponding effect on the size of the droplets formed during the atomisation process of the injected fuel. The results have shown that cavitation is the main flow factor that determines injection velocity and initial droplet size. At the same time, internal flow simulations have shown that multi-hole injectors with a central hole have an uneven flow distribution which results to an over
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Multihole injectors for direct-injection gasoline engines

Multihole injectors for direct-injection gasoline engines

6.4 RECOMMENDATIONS FOR FUTURE WORK It can be argued that the presented work provided useful information about gasoline multi-hole high-pressure injector nozzle flow, spray characterisat[r]

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A REVIEW ON LASER INDUCED IGNITION OF GASOLINE DIRECT INJECTION ENGINES

A REVIEW ON LASER INDUCED IGNITION OF GASOLINE DIRECT INJECTION ENGINES

Sustainability with regard to internal combustion engines is strongly linked to the fuels burnt and the overall efficiency. Laser ignition can enhance the combustion process and minimize pollutant formation. This paper is on laser ignition of sustainable fuels for future internal combustion engines. Ignition is the process of starting radical reactions until a self-sustaining flame has developed. In technical appliances such as internal combustion engines, reliable ignition is necessary for adequate system performance. Ignition strongly affects the formation of pollutants and the extent of fuel conversion. This paper presents experimental results on laser- induced ignition for technical applications.Laser ignition tests were performed with the fuels hydrogen and biogas in a static combustion cell and with gasoline in a spray-guided internal combustion engine. A Nd:YAG laser with 6 ns pulse duration, 1064 nm wavelength and 1-50 mJ pulse energy was used to ignite the fuel/air mixtures at initial pressures of 1-3 MPa. Schlieren photography was used for optical diagnostics of flame kernel development and shock wave propagation. Compared to a conventional spark plug, a laser ignition system should be a favorable ignition source in terms of lean burn characteristics and system flexibility. Yet several problems remain unsolved, e.g. cost issues and the stability of the optical window. The literature does not reveal much information on this crucial system part. Different window configurations inengine test runs are compared and discussed.
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Experimental Investigation of Spray and Combustion of Gasoline Direct Injection under Different Ambient Conditions.

Experimental Investigation of Spray and Combustion of Gasoline Direct Injection under Different Ambient Conditions.

While gasolines with higher octane numbers can enable more efficient future spark ignition (SI) engines, low octane gasoline-like fuels might be desirable in compression ignition (CI) engines. Generally, low octane refinery fuel, such as Naphtha, is composed of C5 to C11 hydrocarbons and has a low research octane number (RON) value. Since these fuels requires much less processing in the refinery than either gasoline or diesel, there is an additional benefit in terms of well-to-wheel CO2 emissions and overall energy consumed[14]. Compared to commercial gasoline and diesel fuels, blends of various refinery streams with low octane fuels have been considered attractive alternatives to provide suitable chemical characteristics (longer ignition delay than diesel) in GCI engines at lower production cost and well-to-tank CO2 emissions. Hao et al.[15] found that compared with the conventional pathway, the low-octane gasoline-GCI pathway leads to a 24.6% reduction in energy consumption and a 22.8% reduction in GHG emissions. It is attracting research interest to have a deeper understanding on the spray and combustion characteristics of gasoline and gasoline surrogate fuels.
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Direct Fuel Injection of LPG in Small Two-Stroke Engines

Direct Fuel Injection of LPG in Small Two-Stroke Engines

Retrofitting the gasoline engine to use LPG is an appealing possibility [6]-[8]. Many countries have programs for converting popular two-stroke vehicles to LPG owing to its low fuel price in comparison with gasoline [9]. Typically these conversions consist of simple gaseous carburettors, premixing the fuel with the incoming air [10]. Engines thus converted to premixed LPG are popularly believed to be much cleaner than the original gasoline engine due to a significant reduction in visible smoke produced. They do nothing, however, to address the fuel short-circuiting, and subsequently suffer from both poor fuel efficiency and high hydrocarbon emissions, albeit in the form of a gaseous fuel which is less likely to condense and form visible “smoke”. Fig. 2 shows the difference in visible smoke emissions when running on gasoline (top) and LPG premixed (bottom). LPG is a cleaner burning fuel as it generally will reduce the emissions of CO and many others of the higher molecular weight hazardous air pollutants as LPG is fully vaporized before combustion and consist exclusively of lower molecular weight hydrocarbons.
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Characterisation of soot in oil from a gasoline direct injection engine using Transmission Electron Microscopy

Characterisation of soot in oil from a gasoline direct injection engine using Transmission Electron Microscopy

Barone et al. [30] used TEM to investigate the diameter of aggregate primary particles from GDI exhaust gas soot. They studied particles morphology as a function of injection strategy. Early fuel injections, leading to a more homogeneous air/fuel mixture before combustion, produced nano-particle aggregates ranging between 8 and 52 nm. For retarded fuel injection strate- gies, most aggregates had fractal-like morphology similar to diesel soot. Mathis et al. [31] studied exhaust soot particles from GDI engines and identi fi ed primary particles with a size of about 27 nm. Choi et al. [32] analysed exhaust soot from a GDI engine, showing chain-like structures ranging from 70 to 400 nm in size, with particle cores between 30 and 80 nm. Uy et al. [33] have recently characterised the nanostructure of gasoline soot. They determined and compared the degree of order of the graphitic planes of soot primary particles extracted from the exhaust gas and from engine oil. Soot-in-oil from GDI engine has not been investigated widely; to the authors' best knowledge, its agglom- erate size distribution and shape have not been reported in the literature. A summary of the typical dimensions of soot particles from internal combustion engines is reported in Table 1.
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Cfd Modeling of the In Cylinder Flow In Direct-Injection Diesel Engines

Cfd Modeling of the In Cylinder Flow In Direct-Injection Diesel Engines

Combustion processes For internal combustion engines, two different types of four-stroke combustion processes are traditionally used; spark ignited (SI) and compression ignited (CI) combustion. The former is used in gasoline engines, where the fuel is mixed with the air prior to TDC when a spark ignites the mixture. In the latter, the compression ignition engine, the fuel is injected close to TDC and the heatcaused by the compression ignites the fuel. This type of engine, use primarily diesel fuel and is often called diesel engines. In a spark ignited engines the fuel is mixed with the air at start of combustion (SOC). The combustion process is thus entirely premixed. In the direct injected diesel engine, several processes occur before and after the main discussion combustion
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Comparative nanostructure analysis of gasoline turbocharged direct injection and diesel soot in oil with carbon black

Comparative nanostructure analysis of gasoline turbocharged direct injection and diesel soot in oil with carbon black

As the size of soot nanoparticles is typically well below one micrometre, high resolution transmission electron microscopy (HRTEM) is the preferred imaging technique for subsequent nanoscale analysis of morphology and structure. TEM has been used to characterise soot from both the exhaust gas [18 e 21 ,24] and lubricating oil [7,17,18,24] of internal combustion engines, as well as soot from diffusion fl ames [23,30,31]. Depending on the soot origin the methods of sample collection differ signi fi cantly. A variety of techniques have been previously employed to obtain soot from exhaust gas of internal combustion engines. Gaddam and Vander Wal [20] sampled soot directly from the exhaust gas on TEM grids. However, high soot concentration in the exhaust gas can over- saturate the grids. To prevent oversaturation and reduce over- lapping of agglomerates, the collection time can be reduced [32]. Alternatively, the exhaust gas can be diluted with clean air [19] or an inert gas, e.g. nitrogen [33], enabling longer collection times. Barone et al. [19] as well as Liati et al. [21] diluted the exhaust gas by a factor of 30 and 13.5, respectively, prior to deposition on TEM grids. To image soot-in-oil samples, the soot agglomerates need to be separated from the lubricating oil. Esangbedo et al. [24] diluted oil samples in heptane and transferred small amounts onto TEM grid after ultrasonically bathing. La Rocca et al. [7] separated soot from the used lubricating oil by multiple cycles of centrifugation and replacing the liquid oil-phase with heptane. Despite altering the observed size distribution of the agglomerates, this procedure enabled observation of the primary particle nanostructure. A similar procedure was employed by Uy et al. [18] using hexane as the solvent. Soot generated from diffusion fl ames, also known as carbon black, can be collected directly from the fl ame by thermo- phoresis on TEM grids, as done by Bhowmick et al. [30] and Schenk et al. [31]. Alf e et al. [23] collected soot from the fl ame on probes in bulk and subsequently transferred onto TEM grids by ultrasonic agitation in methanol.
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Computational Fluid Dynamics (CFD) Modelling of Mixture Formation in Gasoline Direct Injection (GDI) Engine

Computational Fluid Dynamics (CFD) Modelling of Mixture Formation in Gasoline Direct Injection (GDI) Engine

Gasoline Direct Injection (GDI) is regarded as a wide-used technology in modern spark ignition (SI) engines due to its improved thermal efficiency and exhaust emission compared with port fuel injection [1-4]. Generally, there are two types of GDI engines with different injection strategies, early injection operating under homogeneous charge mode while late injection at stratified charge condition. It is indicated that the latter could achieve the potential of GDI engine on better fuel economy and emission level [4,5]. As a result, the GDI engine with late injection and its process of mixture formation and fuel atomisation leading to fuel vaporisation and burning of the air-fuel mixture has been a research focus.
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A study of fuel spray structure and its relationship to emissions and performance of a gasoline direct injection engine

A study of fuel spray structure and its relationship to emissions and performance of a gasoline direct injection engine

W ith PFI engines, operation is possible with relatively low fuel pressures, as the spray is very often impacted on hot port and valve surfaces from where it evaporates. A GDI engine usually requires small droplets so that evaporation occurs before impaction, at least at some o f the operating conditions. Mitsubishi's engine utilises a fuel pressure o f 5.5 MPa, while Jackson et al [1996] describe a similar engine which operates within a range o f 5 - 10 MPa. Lower fuel pressures are not likely to be possible due to a num ber o f reasons. The first, and most significant, is the requirement for good fuel atomisation. Even if fine atom isation were possible at lower pressures, metering errors would occur due to the variation o f m etering pressure differential caused by rapid changes in cylinder pressure. However, it is not practical to have very high pressures either, as pump wear becomes a problem. Currently, some diesel fuel systems operate at pressures up to 200 M Pa [Kimberley, 1999]. However, this is aided by the lubrication properties o f diesel. Gasoline does not have this lubricity. Therefore a higher- pressure system will be, at best, more expensive to design and produce. At worst, impractical.
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DOWNSIZING OF GASOLINE ENGINES

DOWNSIZING OF GASOLINE ENGINES

Downsizing is today considered as a promising way to increase fuel economy with a good cost to benefit ratio. The challenge is here to reduce the engine displacement volume while keeping the same performance in terms of torque and power than the initial larger engine, and simultaneously to ensure an improvement in engine efficiency. Downsizing of gasoline engine is already an industrial reality. During last years, several car makers have presented 1.8 l to 2.0 l turbocharged engines. The performances of these engines are typically the ones of naturally aspirated engines with 2.5 l displacement. The reduction of fuel consumption is typically about 10%. The second generation of downsized engines is today the object of extensive research. Target is to reduce by half the displacement of the engines and also to consider the downsizing of smaller engines than the upperclass engines with 2.5 l displacement or more. This paper explains the concept of downsizing using aturbocharger coupledwith gasoline direct injection and illustrates the potential of downsizing in the very near future.
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Effect of Cylinder Air Pressure and Fuel
Injection Pressure on Combustion
Characteristics of Direct Injection (DI) Diesel
Engine Fueled with Diesel and Gasoline

Effect of Cylinder Air Pressure and Fuel Injection Pressure on Combustion Characteristics of Direct Injection (DI) Diesel Engine Fueled with Diesel and Gasoline

IDI engine is less efficient than the DI engine. This is because the high velocity air motion in the combustion chamber causes high heat transfer rates resulting in greater loss of fuel energy. The lower efficiency of the IDI engine has resulted in it being out-of-favor and although there are a large number of these engines currently being produced, virtually all new engine designs use direct injection technology [1].

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Computational Investigations On A Four Cylinder Four Stroke Cycle Spark Ignition Engine With Hydrogen And Gasoline Direct Injection

Computational Investigations On A Four Cylinder Four Stroke Cycle Spark Ignition Engine With Hydrogen And Gasoline Direct Injection

This paper presents the results of the computational investigations on a four cylinder four stroke cycle spark ignition engine using hydrogen as an alternative fuel to conventional gasoline or petrol in direct injection modes of fuel supply. The results were computed in the professional thermodynamic internal combustion engines simulation software, AVL BOOST. The Software uses the fundamental conservation laws of mass, energy and momentum along with the numerical finite volume method needed to solve the partial differential equations written for a control volume. These equations were written for the flow based gas exchange processes in the intake and exhaust gas manifolds using pipe connections in their designs. The laws of thermodynamics and gas dynamic principles help to solve and compute the values of the thermodynamic variables in all the components of the engine. Further the software has provision for selection of suitable combustion models, heat transfer models, frictional power based models, along with the models needed for the analysis of emission produced by the modeled engine. The software has exten- sive provisions to select alternative elements used in the development of a complete model for a particu- lar class of engines. The modeled engine was first run in the gasoline direct injection mode and the re- sults were computed for its performance and emissions analysis. These results were used as a reference data for this type of conventional engine.
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Effects of intake flow and coolant temperature on the spatial fuel distribution in a direct-injection gasoline engine by PLIF technique

Effects of intake flow and coolant temperature on the spatial fuel distribution in a direct-injection gasoline engine by PLIF technique

The key to success and also the challenge in DISI engines is to prepare fuel/air mixture towards the spark plug over the full range of engine operating conditions, as the fuel/air mixing process is influenced by many time dependant variables. In this study, a follow up of the previous study [11] by the same authors, the planar laser induced fluorescence technique is used to study the in-cylinder fuel concentration distribution generated by a high pressure multi-hole injector with the effect of the in-cylinder air charge motion, the coolant temperature of the engine cylinder head and the fuel injection pressure under the two main injection strategies, i.e. the homogenous charge mode and the stratified charge mode. The engine configuration and experimental techniques for the present experiments are described in the following section, the results are presented and discussed in section 3, and the paper ends with a summary of the most important findings.
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Performance and Emission Characteristics of MPFI Engine by Using Gasoline - Ethanol Blends

Performance and Emission Characteristics of MPFI Engine by Using Gasoline - Ethanol Blends

Multiport fuel injection injects fuel into the intake ports just upstream of each cylinder's intake valve, rather than at a central point within an intake manifold. MPFI (or just MPI) systems can be sequential, in which injection is timed to coincide with each cylinder's intake stroke; batched, in which fuel is injected to the cylinders in groups, without precise synchronization to any particular cylinder's intake stroke; or simultaneous, in which fuel is injected at the same time to all the cylinders. The intake is only slightly wet, and typical fuel pressure runs between 40-60 psi. Many modern EFI systems utilize sequential MPFI; however, in newer gasoline engines, direct injection systems are beginning to replace sequential ones.
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Evaluation of Lean Operation Limit on Performance Features of Stratified Charge Gasoline Direct Injection (GDI) Engine

Evaluation of Lean Operation Limit on Performance Features of Stratified Charge Gasoline Direct Injection (GDI) Engine

In internal combustion engines, the cylinder pressure profile variation is caused by uncertainty in charge inlet and its imperfect mix during combustion, moreover, ignition time when combustion starts is also important to cylinder pressure [1, 7]. Even though the MBT was fixed to all tests, the variation in air fuel ratio and its subsequent mixing has caused different in cylinder pressure profile at each operating variable. It is clearly evident from figure 13, 14 the operating variable combination AFR 16.7, SOI 100° bTDC with MBT 18° showed better combustion pressure profile. Being AFR 16.7 was identified as lean limit air fuel ratio and this operating module exhibits significant difference in cylinder pressures profiles and huge difference at TDC.
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Performance Analysis of Gasoline Direct Injection inTwo Stroke Spark-ignition Engines

Performance Analysis of Gasoline Direct Injection inTwo Stroke Spark-ignition Engines

Homogeneous mode (or Early Injection): At higher loads, the mixture in the stratified mode can become too rich leading to soot formation. Also at high speeds we cannot provide sufficient stratification due to turbulence in the cylinder. So at high loads and high speeds Homogeneous Charge Compression ignition mode is used. It causes a fully mixed charge to self-ignite by compressing it together with hot exhaust gas from the previous cycle. It offers the possibility of diesel-like fuel economy on gasoline with high torque and fewer emissions. It is represented in Figure No.3.
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Spray structure from double fuel injection in multihole injectors for gasoline direct-injection engines

Spray structure from double fuel injection in multihole injectors for gasoline direct-injection engines

As illustrated in Figure 14 (top row), in the interval between the two injection events (marked region), droplet sizes are similar or even larger than those measured during the main injections. The results also indicate that the droplet size distributions during the longer dwell time (1ms with no pre-spray) are either similar (SMD) or larger (AMD) than those during the shorter dwell time (0.3ms with pre-spray) at 2.5mm from the nozzle exit (Figure 14 top row). This can be explained from the type of droplets and the number of samples collected during the dwell time periods. In the case of the 0.3ms dwell time (Figure 14a) when there is a pre-spray, the data rate is very high and the validated samples per averaging time window can be as many as 3,000, thus influencing the AMD values. On the other hand, a dwell time of 1ms (Figure 14b) does not produce a pre-spray and the validated samples during that period are low and may not exceed 500 per time window. This low number of validated samples during the dwell time period is the result of droplets formed by liquid ligaments exiting the injection holes after the needle has closed; these liquid ligaments are produced from the liquid left in the sac volume and emerge from the injection holes with little atomisation due to the lack of upstream pressure; they are captured by the PDA system as few large droplets which control the SMD values. However, the afore-described situation is reversed at 10mm from the nozzle exit (Figure 14 bottom row).
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Internal flow and cavitation in a multi-hole injector for gasoline direct-injection engines

Internal flow and cavitation in a multi-hole injector for gasoline direct-injection engines

Observation of the flow in the large-scale multi-hole nozzle has revealed that increasing the cavitation number resulted in the formation of different types of cavitation. All of the investigated conditions confirmed that cavitation behaviour in the enlarged nozzle was highly dynamic and unstable. Initially and unexpectedly, a ‘needle string’ was identified prior to any evidence of hole cavitation. It is termed ‘needle string’ since it appears to originate at the needle surface facing an injection hole and to extend downstream inside the hole. At very low cavitation numbers, of the order of 0.5-0.7, strings originating at the needle surface extended downstream into the hole when the process was fully developed, as can be seen in Figure 9 top row. The occurrence of such strings is quite random and can happen to any one of the nozzle holes. There is evidence that needle strings are created at the core of the instantaneous vortical flow structures which extend from the nozzle hole axis towards the section of the needle surface with the lowest local pressure, due probably to the adverse pressure gradient as the flow turns following the curvature of the needle tip. It can be argued that the slightest geometric eccentricity of the needle due to a manufacturing imperfection can promote the formation of a vortical structure in the sac volume; this effect is not significant in the present enlarged nozzle geometry which is axisymmetric with a concentric needle.
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Investigation of Spray and Combustion of a Piezoelectric Fuel Injector for Gasoline Direct Injection Engines

Investigation of Spray and Combustion of a Piezoelectric Fuel Injector for Gasoline Direct Injection Engines

28 attentions because of their sensitive and fast response, which are significant for small quantities or closely spaced multiple injections [46]. Spray from a piezo injector has a hollow-cone structure with visible striations and filaments. Unlike hollow cone pressure-swirl sprays, no collapse arises with the spray development [47], and this spray pattern is quite repeatable [48]. Studies have been done on both types of injectors in GDI engines in the past few years. Smith et al. [49] conducted a systematic performance comparison of two spray-guided, single- cylinder, spark-ignited direct-injected (SIDI) engine combustion system designs with both solenoid and piezo injectors and found that the two kinds of injectors have comparable combustion stability and smoke emissions. Achleitner et al. [50] demonstrated the possibility to develop a spray-guided combustion system to meet the requirements to the maximum possible extent by using a piezo injector. Skogsberg et al. [48] and Wang et al. [51] explored the atomization of sprays generated by a piezo injector. It was shown that a leading edge vortex is formed at the outer periphery of the spray. The location of the leading edge vortex depends on back pressure. Zhang and co-authors [52] demonstrated that the cone angles at the developed phase for alcohol fuels and isooctane are consistently stable for a solenoid swirl GDI fuel injector. Higher injection pressure helps reduce droplet size.
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