Mixture preparation and combustion in a GDI engine under stoichiometric or lean charge: an experimental and numerical study on an optically accessible engine

Costa, Michela; Catapano, Francesco; Sementa, Paolo; Sorge, Ugo; Vaglieco, Bianca Maria

doi:10.1016/j.apenergy.2016.07.089

Cited by 50 publications

(21 citation statements)

References 36 publications

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“…Flexible control of the air-fuel ratio in the combustion chamber, typical of DI engines, is due to the possibility of realizing either stratified charge or homogeneous mixtures. This is possible by changing the injection pulse while maintaining the overall air-fuel ratio at the stoichiometric point [8], and features the potential for applying advanced operating regimes. Yang et al [9] reported that injection during the intake stroke ("homogeneous mixture") improves volumetric efficiency.…”

Section: Introductionmentioning

confidence: 99%

Flame Front and Burned Gas Characteristics for Different Split Injection Ratios and Phasing in an Optical GDI Engine

2019

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Direct-injection in spark-ignition engines has long been recognized as a valid option for improving fuel economy, reducing CO2 emissions and avoiding knock occurrence due to higher flexibility in control strategies. However, problems associated with mixture formation are responsible for soot emissions, one of the most limiting factors of this technology. Therefore, the combustion process and soot formation were investigated with different injection strategies on a gasoline direct injection (GDI) engine. The experimental analysis was realized on an optically accessible single cylinder engine when applying single, double and triple injection strategies. Moreover, the effect of fuel delivery phasing was also scrutinized by changing the start of the injection during late intake- and early compression-strokes. The duration of injection was split in different percentages between two or three pulses, so as to obtain close to stoichiometric operation in all conditions. The engine was operated at fixed rotational speed and spark timing, with wide-open throttle. Optical diagnostics based on cycle resolved digital imaging was applied during the early and late stages of the combustion process. Detailed information on the flame front morphology and soot formation were obtained. The optical data were correlated to in-cylinder pressure traces and exhaust gas emission measurements. The results suggest that the split injection of the fuel has advantages in terms of reduction of soot formation and NOx emissions and a similar combustion performance with respect to the single injection timing. Moreover, an early injection resulted in higher rates of heat release and in-cylinder pressure, together with a reduction of soot formation and flame distortion. The double injection strategy with higher percentage of fuel injected in the first pulse and early second injection pulse showed the best results in terms of combustion evolution and pollutant emissions. For the operative condition studied, a higher time for mixture homogenization and split of fuel injected in the intake stroke shows the best results.

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Section: Introductionmentioning

confidence: 99%

Flame Front and Burned Gas Characteristics for Different Split Injection Ratios and Phasing in an Optical GDI Engine

2019

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“…1–5 The fuel economy, catalyst efficiency and system security will degrade if the AFR deviates from stoichiometric value for a long time. 6–8…”

Section: Introductionmentioning

confidence: 99%

Enhanced intelligent proportional-integral-like fuzzy knowledge–based controller using chaos-enhanced accelerated particle swarm optimization algorithm for transient calibration of air–fuel ratio control system

Zhou

Zhang

et al. 2019

Proceedings of the Institution of Mechanical Engineers, Part D:

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The self-adaptive and highly robust proportional-integral-like fuzzy knowledge–based controller has been developed to regulate air–fuel ratio for gasoline direct injection engines, in order to improve the transient response behaviour and reduce the effort to be spent on calibration of parameter settings. However, even though the proportional-integral-like fuzzy knowledge–based controller can automatically correct the initially calibrated proportional and integral parameters, a more appropriate selection of controller parameter settings will lead to better transient performance. Thus, this article proposes an enhanced intelligent proportional-integral-like fuzzy knowledge–based controller using chaos-enhanced accelerated particle swarm optimization algorithm to automatically define the most optimal parameter settings. An alternative time-domain objective function is applied for the transient calibration programme without the need for prior selection of the search-domain. The real-time transient performance of the enhanced controller is investigated on the air–fuel ratio control system of a gasoline direct injection engine. The experimental results show that the enhanced proportional-integral-like fuzzy knowledge–based controller based on chaos-enhanced accelerated particle swarm optimization is able to damp out the oscillations with less settling time (up to 75% reduction) and less integral of absolute error (up to 64.07% reduction) compared with the conventional self-adaptive proportional-integral-like fuzzy knowledge–based controller. Repeatability tests indicate that the chaos-enhanced accelerated particle swarm optimization algorithm–based proportional-integral-like fuzzy knowledge–based controller is also able to reduce the mean value of objective function by up to 10.61% reduction and the standard deviation of the objective function by up to 28.29% reduction, compared with the conventional accelerated particle swarm optimization algorithm–based proportional-integral-like fuzzy knowledge–based controller.

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“…Numerous study are reported hereto in both wall-guided and spray-guided engines using multi-stream, hollow-cone, pressure-swirl and air-assisted injector configurations, see e.g. [4,5,6,7,8,9,10,11,12,13] [14,15,16,17] and references therein. Aside lubrication problems, fuel wall films with fuel-rich regions in their vicinity are considered important sources of soot formation [18,19,20].…”

Section: Introductionmentioning

confidence: 99%

Large Eddy Simulations and Tracer-LIF Diagnostics of Wall Film Dynamics in an Optically Accessible GDI Research Engine

Frapolli¹,

Boulouchos²,

Wright³

et al. 2019

SAE Technical Paper Series

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Large Eddy Simulations (LES) and tracer-based Laser-Induced Fluorescence (LIF) measurements were performed to study the dynamics of fuel wall-films on the piston top of an optically accessible, four-valve pent-roof GDI research engine for a total of eight operating conditions. Starting from a reference point, the systematic variations include changes in engine speed (600; 1,200 and 2,000 RPM) and load (1000 and 500 mbar intake pressure); concerning the fuel path the Start Of Injection (SOI=360°, 390° and 420° CA after gas exchange TDC) as well as the injection pressure (10, 20 and 35 MPa) were varied. For each condition, 40 experimental images were acquired phase-locked at 10° CA intervals after SOI, showing the wall-film dynamics in terms of spatial extent, thickness and temperature. The simulation framework was developed as follows: first, the spray model was calibrated using spray morphology evolution data of the same injector, characterized in a constant volume spray chamber by high-speed shadow imaging. In a second step, the wall impingement and film models were calibrated using the reference condition. With the model constants now fixed, simulations were run for the remaining operating points and results were compared with the experimental data. The simulations captured all trends observed experimentally, with good quantitative in the transient films' spatial extents and thicknesses.

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Mixture preparation and combustion in a GDI engine under stoichiometric or lean charge: an experimental and numerical study on an optically accessible engine

Cited by 50 publications

References 36 publications

Flame Front and Burned Gas Characteristics for Different Split Injection Ratios and Phasing in an Optical GDI Engine

Flame Front and Burned Gas Characteristics for Different Split Injection Ratios and Phasing in an Optical GDI Engine

Enhanced intelligent proportional-integral-like fuzzy knowledge–based controller using chaos-enhanced accelerated particle swarm optimization algorithm for transient calibration of air–fuel ratio control system

Large Eddy Simulations and Tracer-LIF Diagnostics of Wall Film Dynamics in an Optically Accessible GDI Research Engine

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