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Combustion stability, engine efficiency and emissions in a multi-cylinder spark-ignition internal combustion engines can be improved through the advanced control and optimization of individual cylinder operation. In this work, experimental and numerical analyses were carried out on a twin-cylinder turbocharged port fuel injection (PFI) spark-ignition engine to evaluate the influence of cylinder-by-cylinder variation on performance and pollutant emissions. In a first stage, experimental tests are performed on the engine at different speed/load points and exhaust gas recirculation (EGR) rates, covering operating conditions typical of Worldwide harmonized Light-duty vehicles Test Cycle (WLTC). Measurements highlighted relevant differences in combustion evolution between cylinders, mainly due to non-uniform effective in-cylinder air/fuel ratio. Experimental data are utilized to validate a one-dimensional (1D) engine model, enhanced with user-defined sub-models of turbulence, combustion, heat transfer and noxious emissions. The model shows a satisfactory accuracy in reproducing the combustion evolution in each cylinder and the temperature of exhaust gases at turbine inlet. The pollutant species (HC, CO and NOx) predicted by the model show a good agreement with the ones measured at engine exhaust. Furthermore, the impact of cylinder-by-cylinder variation on gaseous emissions is also satisfactorily reproduced. The novel contribution of present work mainly consists in the extended numerical/experimental analysis on the effects of cylinder-by-cylinder variation on performance and emissions of spark-ignition engines. The proposed numerical methodology represents a valuable tool to support the engine design and calibration, with the aim to improve both performance and emissions.
Luigi Teodosio; Luca Marchitto; Cinzia Tornatore; Fabio Bozza; Gerardo Valentino. Effect of Cylinder-by-Cylinder Variation on Performance and Gaseous Emissions of a PFI Spark Ignition Engine: Experimental and 1D Numerical Study. Applied Sciences 2021, 11, 6035 .
AMA StyleLuigi Teodosio, Luca Marchitto, Cinzia Tornatore, Fabio Bozza, Gerardo Valentino. Effect of Cylinder-by-Cylinder Variation on Performance and Gaseous Emissions of a PFI Spark Ignition Engine: Experimental and 1D Numerical Study. Applied Sciences. 2021; 11 (13):6035.
Chicago/Turabian StyleLuigi Teodosio; Luca Marchitto; Cinzia Tornatore; Fabio Bozza; Gerardo Valentino. 2021. "Effect of Cylinder-by-Cylinder Variation on Performance and Gaseous Emissions of a PFI Spark Ignition Engine: Experimental and 1D Numerical Study." Applied Sciences 11, no. 13: 6035.
This paper offers new insights into a partial fuel stratification (PFS) combustion strategy that has proven to be effective at stabilizing overall lean combustion in direct injection spark ignition engines. To this aim, high spatial and temporal resolution optical diagnostics were applied in an optically accessible engine working in PFS mode for two fuels and two different durations of pilot injection at the time of spark: 210 µs and 330 µs for E30 (gasoline blended with ethanol by 30% volume fraction) and gasoline, respectively. In both conditions, early injections during the intake stroke were used to generate a well-mixed lean background. The results were compared to rich, stoichiometric and lean well-mixed combustion with different spark timings. In the PFS combustion process, it was possible to detect a non-spherical and highly wrinkled blue flame, coupled with yellow diffusive flames due to the combustion of rich zones near the spark plug. The initial flame spread for both PFS cases was faster compared to any of the well-mixed cases (lean, stoichiometric and rich), suggesting that the flame propagation for PFS is enhanced by both enrichment and enhanced local turbulence caused by the pilot injection. Different spray evolutions for the two pilot injection durations were found to strongly influence the flame kernel inception and propagation. PFS with pilot durations of 210 µs and 330 µs showed some differences in terms of shapes of the flame front and in terms of extension of diffusive flames. Yet, both cases were highly repeatable.
Cinzia Tornatore; Magnus Sjöberg. Optical Investigation of a Partial Fuel Stratification Strategy to Stabilize Overall Lean Operation of a DISI Engine Fueled with Gasoline and E30. Energies 2021, 14, 396 .
AMA StyleCinzia Tornatore, Magnus Sjöberg. Optical Investigation of a Partial Fuel Stratification Strategy to Stabilize Overall Lean Operation of a DISI Engine Fueled with Gasoline and E30. Energies. 2021; 14 (2):396.
Chicago/Turabian StyleCinzia Tornatore; Magnus Sjöberg. 2021. "Optical Investigation of a Partial Fuel Stratification Strategy to Stabilize Overall Lean Operation of a DISI Engine Fueled with Gasoline and E30." Energies 14, no. 2: 396.
Stringent exhaust emission and fuel consumption regulations impose the need for new solutions for further development of internal combustion engines. With this in mind, a refined control of the combustion process in each cylinder can represent a useful and affordable way to limit cycle-to-cycle and cylinder-to-cylinder variation reducing CO2 emission. In this paper, a twin-cylinder turbocharged Port Fuel Injection–Spark Ignition engine is experimentally and numerically characterized under different operating conditions in order to investigate the influence of cycle-to-cycle variation and cylinder-to-cylinder variability on the combustion and performance. Significant differences in the combustion behavior between cylinders were found, mainly due to a non-uniform effective in-cylinder air/fuel (A/F) ratio. For each cylinder, the coefficients of variation (CoVs) of selected combustion parameters are used to quantify the cyclic dispersion. Experimental-derived CoV correlations representative of the engine behavior are developed, validated against the measurements in various speed/load points and then coupled to an advanced 1D model of the whole engine. The latter is employed to reproduce the experimental findings, taking into account the effects of cycle-to-cycle variation. Once validated, the whole model is applied to optimize single cylinder operation, mainly acting on the spark timing and fuel injection, with the aim to reduce the specific fuel consumption and cyclic dispersion.
Luca Marchitto; Cinzia Tornatore; Luigi Teodosio. Individual Cylinder Combustion Optimization to Improve Performance and Fuel Consumption of a Small Turbocharged SI Engine. Energies 2020, 13, 5548 .
AMA StyleLuca Marchitto, Cinzia Tornatore, Luigi Teodosio. Individual Cylinder Combustion Optimization to Improve Performance and Fuel Consumption of a Small Turbocharged SI Engine. Energies. 2020; 13 (21):5548.
Chicago/Turabian StyleLuca Marchitto; Cinzia Tornatore; Luigi Teodosio. 2020. "Individual Cylinder Combustion Optimization to Improve Performance and Fuel Consumption of a Small Turbocharged SI Engine." Energies 13, no. 21: 5548.
This paper reports a numerical and experimental analysis on a twin-cylinder turbocharged Spark Ignition engine carried out to investigate the cylinder-to-cylinder variability in terms of performance, combustion evolution and exhaust emissions. The engine was tested at 3000 rpm in 20 different steady-state operating conditions, selected with the purpose of observing the influence of cylinder-by-cylinder A/F ratio variations and the EGR effects on the combustion process and exhaust emissions for low to medium/high loads. The experimental outcomes showed relevant differences in the combustion evolution (characteristic combustion angles) between cylinders and not negligible variations in the emissions of the single cylinder exhaust and the overall engine one. This misalignment resulted to be due to differences in the injected fuel amount by the port injectors in the two cylinders, mainly deriving from the specific fuel rail geometry. The experimental data were then used to validate a 1D engine model, integrated with refined sub-models of turbulence, combustion, heat transfer and emissions. The model takes into account the in-cylinder production of noxious species, and their propagation in the exhaust system, up to the three-way catalytic converter. A satisfactory accuracy was reached in reproducing the overall engine performance and the combustion process in the two cylinders. In particular, the emission sub-models confirmed that the variations of the cylinder-out exhaust emissions (NOx, HC and CO) were mainly due to the non-uniform effective in-cylinder A/F ratio. The proposed numerical methodology has the potential to highlight unexpected combustion non-uniformities among different cylinders and represents a powerful support to the engine design and development. It also allows for the prediction of the overall exhaust emissions at different engine operating conditions up to the entire domain, thus assisting the engine calibration phase and reducing the experimental efforts.
Luca Marchitto; Luigi Teodosio; Cinzia Tornatore; Gerardo Valentino; Fabio Bozza. Experimental and 1D Numerical Investigations on the Exhaust Emissions of a Small Spark Ignition Engine Considering the Cylinder-by-Cylinder Variability. SAE Technical Paper Series 2020, 1 .
AMA StyleLuca Marchitto, Luigi Teodosio, Cinzia Tornatore, Gerardo Valentino, Fabio Bozza. Experimental and 1D Numerical Investigations on the Exhaust Emissions of a Small Spark Ignition Engine Considering the Cylinder-by-Cylinder Variability. SAE Technical Paper Series. 2020; ():1.
Chicago/Turabian StyleLuca Marchitto; Luigi Teodosio; Cinzia Tornatore; Gerardo Valentino; Fabio Bozza. 2020. "Experimental and 1D Numerical Investigations on the Exhaust Emissions of a Small Spark Ignition Engine Considering the Cylinder-by-Cylinder Variability." SAE Technical Paper Series , no. : 1.
The stringent worldwide exhaust emission legislations for CO2 and pollutants require significant efforts to increase both the combustion efficiency and the emission quality of internal combustion engines. With this aim, several solutions are continuously developed to improve the combustion efficiency of spark ignition engines. Among the various solutions, EGR represents a well-established technology to improve the gasoline engine performance and the nitrogen-oxides emissions. This work presents the results of an experimental investigation on the effects of the EGR technique on combustion evolution, knock tendency, performance and emissions of a small-size turbocharged PFI SI engine, equipped with an external cooled EGR system. Measurements are carried out at different engine speeds, on a wide range of loads and EGR levels. The standard engine calibration is applied at the reference test conditions. Then, the exhaust gas is recirculated and the load is controlled by adjusting the intake pressure, the injection and the spark timing. The main results show a significant reduction in specific fuel consumption at low load due to the lower pumping losses when EGR is active, independent on the engine speed. At high load, a lower improvement in fuel economy has been found, mainly due to a slight reduction in the knock tendency. EGR results in a reduction in NO emission at each engine speed and load, with penalties in HC emission.
Luca Marchitto; Cinzia Tornatore; Gerardo Valentino; Luigi Teodosio. Impact of Cooled EGR on Performance and Emissions of a Turbocharged Spark-Ignition Engine under Low-Full Load Conditions. SAE Technical Paper Series 2019, 1 .
AMA StyleLuca Marchitto, Cinzia Tornatore, Gerardo Valentino, Luigi Teodosio. Impact of Cooled EGR on Performance and Emissions of a Turbocharged Spark-Ignition Engine under Low-Full Load Conditions. SAE Technical Paper Series. 2019; ():1.
Chicago/Turabian StyleLuca Marchitto; Cinzia Tornatore; Gerardo Valentino; Luigi Teodosio. 2019. "Impact of Cooled EGR on Performance and Emissions of a Turbocharged Spark-Ignition Engine under Low-Full Load Conditions." SAE Technical Paper Series , no. : 1.
This study examines the effects of ethanol and gasoline injection mode on the combustion performance and exhaust emissions of a twin cylinder port fuel injection (PFI) spark ignition (SI) engine. Generally, when using gasoline–ethanol blends, alcohol and gasoline are externally mixed with a specified blending ratio. In this activity, ethanol and gasoline were supplied into the intake manifold into two different ways: through two separated low pressure fuel injection systems (Dual-Fuel, DF) and in a blend (mix). The ratio between ethanol and gasoline was fixed at 0.85 by volume (E85). The initial reference conditions were set running the engine with full gasoline at the knock limited spark advance boundary, according to the standard engine calibration. Then E85 was injected and a spark timing sweep was carried out at rich, stoichiometric, and lean conditions. Engine performance and gaseous and particle exhaust emissions were measured. Adding ethanol could remove over-fueling with an increase in thermal efficiency without engine load penalties. Both ethanol and charge leaning resulted in a lowering of CO, HC, and PN emissions. DF injection promoted a faster evaporation of gasoline than in blend, shortening the combustion duration with a slight increase in THC and PN emissions compared to the mix mode.
Cinzia Tornatore; Luca Marchitto; Maria Antonietta Costagliola; Gerardo Valentino. Experimental Comparative Study on Performance and Emissions of E85 Adopting Different Injection Approaches in a Turbocharged PFI SI Engine. Energies 2019, 12, 1555 .
AMA StyleCinzia Tornatore, Luca Marchitto, Maria Antonietta Costagliola, Gerardo Valentino. Experimental Comparative Study on Performance and Emissions of E85 Adopting Different Injection Approaches in a Turbocharged PFI SI Engine. Energies. 2019; 12 (8):1555.
Chicago/Turabian StyleCinzia Tornatore; Luca Marchitto; Maria Antonietta Costagliola; Gerardo Valentino. 2019. "Experimental Comparative Study on Performance and Emissions of E85 Adopting Different Injection Approaches in a Turbocharged PFI SI Engine." Energies 12, no. 8: 1555.
Cooled exhaust gas recirculation (EGR) is a viable technique to mitigate the knock occurrence, to improve the fuel consumption and to reduce the nitrogen oxides (NOx) emissions of spark-ignition engines. This work aims at investigating the effects of a low-pressure cooled EGR system on the performance and exhaust emissions of a small-size turbocharged SI engine through numerical and experimental analyses. First, the experiments are carried out at a speed of 3000 rpm and different engine loads. The standard engine calibration is applied at the reference test conditions. Then, the EGR system is activated and the load is controlled by adjusting the plenum pressure and the spark timing. The experimental results are used to validate a 1D engine model, developed in GT-Power™ software. The latter is integrated with “user-defined” sub-models for an accurate description of the in-cylinder processes, namely turbulence, combustion and heat transfer. Maximum EGR benefits over fuel consumption are achieved at low load, thanks to the reduction of the pumping losses. At high load, minor fuel consumption improvements are obtained, mainly arising from a slight increased knock resistance. Furthermore, increasing EGR rate results in a sensible NOx reduction at each engine load, with a slight penalty on the unburned hydrocarbon emission.
Cinzia Tornatore; Fabio Bozza; Vincenzo De Bellis; Luigi Teodosio; Gerardo Valentino; Luca Marchitto. Experimental and numerical study on the influence of cooled EGR on knock tendency, performance and emissions of a downsized spark-ignition engine. Energy 2019, 172, 968 -976.
AMA StyleCinzia Tornatore, Fabio Bozza, Vincenzo De Bellis, Luigi Teodosio, Gerardo Valentino, Luca Marchitto. Experimental and numerical study on the influence of cooled EGR on knock tendency, performance and emissions of a downsized spark-ignition engine. Energy. 2019; 172 ():968-976.
Chicago/Turabian StyleCinzia Tornatore; Fabio Bozza; Vincenzo De Bellis; Luigi Teodosio; Gerardo Valentino; Luca Marchitto. 2019. "Experimental and numerical study on the influence of cooled EGR on knock tendency, performance and emissions of a downsized spark-ignition engine." Energy 172, no. : 968-976.
Water in diesel emulsion (WiDE) is a viable solution for lowering both NOx and Soot emissions from compression ignition (CI) engines. In this paper, the effect of WiDE on the combustion process and exhaust emissions of a prototype optically accessible CI engine was investigated through conventional in-cylinder pressure measurements and optical diagnostics. The emulsion (9.1%v of water) was produced through a prototype designed microchannels emulsifier with a small amount of nonionic surfactant. Commercial diesel was set as reference fuel and compared to WiDE. The start of injection (SOI) was swept from 8 to 23 CAD BTDC. For diesel fuel, the injected mass and injection pressure were representative of a medium load regime, WiDE injection interval was adjusted to keep constant the energy content. Compared to Diesel, WiDE induced an increase in ignition time, enhancing the air/fuel mixing with a simultaneous reduction in PM and NOx. 2D chemiluminescent emission measurements highlighted a reduction in soot formation using WiDE, without significant changes in soot oxidation rate.
C Tornatore; R Calabria; L Marchitto; J Belletre; P Massoli; A Montillet; G Valentino. Optical Analysis of Combustion and Soot Formation in a CI Engine Fuelled with Water in Diesel Emulsion through Microchannels Emulsification. Journal of Physics: Conference Series 2018, 1110, 012010 .
AMA StyleC Tornatore, R Calabria, L Marchitto, J Belletre, P Massoli, A Montillet, G Valentino. Optical Analysis of Combustion and Soot Formation in a CI Engine Fuelled with Water in Diesel Emulsion through Microchannels Emulsification. Journal of Physics: Conference Series. 2018; 1110 (1):012010.
Chicago/Turabian StyleC Tornatore; R Calabria; L Marchitto; J Belletre; P Massoli; A Montillet; G Valentino. 2018. "Optical Analysis of Combustion and Soot Formation in a CI Engine Fuelled with Water in Diesel Emulsion through Microchannels Emulsification." Journal of Physics: Conference Series 1110, no. 1: 012010.
Luca Marchitto; Cinzia Tornatore; Maria Antonietta Costagliola; Arturo Iacobacci; Gerardo Valentino. Effect of Water Injection on Fuel Efficiency and Gaseous and PN Emissions in a Downsized Turbocharged SI Engine. Journal of Energy Engineering 2018, 144, 04018044 .
AMA StyleLuca Marchitto, Cinzia Tornatore, Maria Antonietta Costagliola, Arturo Iacobacci, Gerardo Valentino. Effect of Water Injection on Fuel Efficiency and Gaseous and PN Emissions in a Downsized Turbocharged SI Engine. Journal of Energy Engineering. 2018; 144 (4):04018044.
Chicago/Turabian StyleLuca Marchitto; Cinzia Tornatore; Maria Antonietta Costagliola; Arturo Iacobacci; Gerardo Valentino. 2018. "Effect of Water Injection on Fuel Efficiency and Gaseous and PN Emissions in a Downsized Turbocharged SI Engine." Journal of Energy Engineering 144, no. 4: 04018044.
The paper reports the results of an experimental investigation carried out on a prototype optically accessible compression ignition engine fueled with water in diesel emulsion (WiDE) and Diesel only. The effect of WiDE on combustion process evolution and exhaust emissions was investigated through standard engine benchmark and optical diagnostics. 2D chemiluminescent emission measurements centered at 690 nm were carried out during the whole combustion process to discriminate the soot emission from other excited chemical species. The emulsion was produced through a prototype designed microchannels emulsifier that can also work inline. The water concentration was 9.1%v with a small amount (0.2%v) of nonionic surfactant (SPAN80) used to stabilize the emulsion. Tests were performed comparing combustion and exhaust emissions of the reference commercial diesel fuel to the WiDE. For any investigated fuel and operating point, engine tests were carried out changing the injection interval to achieve the same chemical energy as the reference diesel (935 J/str). Compared to Diesel, the WiDE induced an increase in ignition time, enhancing the air/fuel mixing with a simultaneous reduction in both PM and NOx. The digital imaging and 2D chemiluminescence techniques highlighted a reduction in soot formation without significant changes on the soot oxidation rate. The results suggest the use of WiDE as a reliable method to improve NOx-soot trade-off of CI engines.
Luca Marchitto; R. Calabria; Cinzia Tornatore; Jerome Bellettre; P. Massoli; A. Montillet; G. Valentino. Optical investigations in a CI engine fueled with water in diesel emulsion produced through microchannels. Experimental Thermal and Fluid Science 2018, 95, 96 -103.
AMA StyleLuca Marchitto, R. Calabria, Cinzia Tornatore, Jerome Bellettre, P. Massoli, A. Montillet, G. Valentino. Optical investigations in a CI engine fueled with water in diesel emulsion produced through microchannels. Experimental Thermal and Fluid Science. 2018; 95 ():96-103.
Chicago/Turabian StyleLuca Marchitto; R. Calabria; Cinzia Tornatore; Jerome Bellettre; P. Massoli; A. Montillet; G. Valentino. 2018. "Optical investigations in a CI engine fueled with water in diesel emulsion produced through microchannels." Experimental Thermal and Fluid Science 95, no. : 96-103.
This paper presents results of an experimental investigation on a flexible port dual fuel injection using different ethanol to gasoline mass fractions. A four stroke, two cylinder turbocharged SI engine was used for the experiments. The engine speed was set at 3000 rpm, tests were carried out at medium-high load and two air-fuel-ratio.The initial reference conditions were set running the engine, fueled with full gasoline at the KLSA boundary, in accordance with the standard ECU engine map. This engine point was representative of a rich mixture (λ=0.9) in order to control the knock and the temperature at turbine inlet. The investigated fuels included different ethanol-gasoline mass fractions (E10, E20, E30 and E85), supplied by dual injection within the intake manifold. A spark timing sweep, both at stoichiometric and lean (λ=1.1) conditions, up to the most advanced one without knock was carried out. Engine performance, gaseous exhaust emissions, particle size distribution and particulate matter were measured and the results were compared to the gasoline reference case.The main results showed that the E20 and E30 ethanol mass fractions, allowing advanced spark timings, achieved the same engine load as the gasoline case with a significant increase in thermal efficiency (≅10%), in spite of alcohol’s lower energy content. Compared to gasoline, E30 or E85 attained a significant reduction in particle number emissions as well a cut of the particulate mass (60-80%), particularly significant for the lean case (90%).
Luca Marchitto; Cinzia Tornatore; Maria Antonietta Costagliola; Gerardo Valentino. Impact of Ethanol-Gasoline Port Injected on Performance and Exhaust Emissions of a Turbocharged SI Engine. SAE Technical Paper Series 2018, 1 .
AMA StyleLuca Marchitto, Cinzia Tornatore, Maria Antonietta Costagliola, Gerardo Valentino. Impact of Ethanol-Gasoline Port Injected on Performance and Exhaust Emissions of a Turbocharged SI Engine. SAE Technical Paper Series. 2018; ():1.
Chicago/Turabian StyleLuca Marchitto; Cinzia Tornatore; Maria Antonietta Costagliola; Gerardo Valentino. 2018. "Impact of Ethanol-Gasoline Port Injected on Performance and Exhaust Emissions of a Turbocharged SI Engine." SAE Technical Paper Series , no. : 1.
Cinzia Tornatore; Daniela Siano; Luca Marchitto; Arturo Iacobacci; Gerardo Valentino; Fabio Bozza. Water Injection: a Technology to Improve Performance and Emissions of Downsized Turbocharged Spark Ignited Engines. SAE International Journal of Engines 2017, 10, 2319 -2329.
AMA StyleCinzia Tornatore, Daniela Siano, Luca Marchitto, Arturo Iacobacci, Gerardo Valentino, Fabio Bozza. Water Injection: a Technology to Improve Performance and Emissions of Downsized Turbocharged Spark Ignited Engines. SAE International Journal of Engines. 2017; 10 (5):2319-2329.
Chicago/Turabian StyleCinzia Tornatore; Daniela Siano; Luca Marchitto; Arturo Iacobacci; Gerardo Valentino; Fabio Bozza. 2017. "Water Injection: a Technology to Improve Performance and Emissions of Downsized Turbocharged Spark Ignited Engines." SAE International Journal of Engines 10, no. 5: 2319-2329.
Diversification of the energy mix and the drive for increasing security of supply have extended the use of alternative fuels in internal combustion engines. Butanol is a viable energy source for spark ignition (SI) power units featuring higher energy density and compatibility with existing systems. The present work investigated the use of n-butanol in an optically accessible wall guided direct injection SI engine, operated at low load, as well as wide open throttle. Engine speed and injection pressure were kept constant, while coolant temperature was alternated between two values, so as to simulate cold-start and fully warmed-up conditions. In-cylinder pressure and exhaust gas emission measurements were coupled with optical results obtained through UV-visible flame visualization and 2D chemiluminescence. This allowed a more detailed insight into the occurrence of diffusive flames near the piston surface and an analysis of flame front propagation, as well as its morphology. The correlation of thermodynamic data and flame imaging with band-pass filters for recording the spatial distribution of the OH radical, soot precursors and carbonaceous structures gave information on the evolution of chemical species during combustion. While at low load the alcohol performed slightly better compared to gasoline, at wide open throttle the opposite was recorded. The effect of coolant temperature was more evident for butanol. These observations were correlated to the presence of liquid fuel film on the piston crown, which resulted in slower flame propagation and higher related emissions for the alcohol.
Adrian Irimescu; Simona Silvia Merola; Cinzia Tornatore; Gerardo Valentino. Effect of coolant temperature on air–fuel mixture formation and combustion in an optical direct injection spark ignition engine fueled with gasoline and butanol. Journal of the Energy Institute 2017, 90, 452 -465.
AMA StyleAdrian Irimescu, Simona Silvia Merola, Cinzia Tornatore, Gerardo Valentino. Effect of coolant temperature on air–fuel mixture formation and combustion in an optical direct injection spark ignition engine fueled with gasoline and butanol. Journal of the Energy Institute. 2017; 90 (3):452-465.
Chicago/Turabian StyleAdrian Irimescu; Simona Silvia Merola; Cinzia Tornatore; Gerardo Valentino. 2017. "Effect of coolant temperature on air–fuel mixture formation and combustion in an optical direct injection spark ignition engine fueled with gasoline and butanol." Journal of the Energy Institute 90, no. 3: 452-465.
In the recent past engine knock emerged as one of the main limiting aspects for the achievement of higher efficiency targets in modern spark-ignition (SI) engines. To attain these requirements, engine operating points must be moved as close as possible to the onset of abnormal combustions, although the turbulent nature of flow field and SI combustion leads to possibly ample fluctuations between consecutive engine cycles. This forces engine designers to distance the target condition from its theoretical optimum in order to prevent abnormal combustion, which can potentially damage engine components because of few individual heavy-knocking cycles. A statistically based RANS knock model is presented in this study, whose aim is the prediction not only of the ensemble average knock occurrence, poorly meaningful in such a stochastic event, but also of a knock probability. The model is based on look-up tables of autoignition times from detailed chemistry, coupled with transport equations for the variance of mixture fraction and enthalpy. The transported perturbations around the ensemble average value are based on variable gradients and on a local turbulent time scale. A multi-variate cell-based Gaussian-PDF model is proposed for the unburnt mixture, resulting in a statistical distribution for the in-cell reaction rate. An average knock precursor and its variance are independently calculated and transported; this results in the prediction of an earliest knock probability preceding the ensemble average knock onset, as confirmed by the experimental evidence. The proposed model estimates not only the regions where the average knock is promoted, but also where and when the first knock is more likely to be encountered. The application of the model to a RANS simulation of a modern turbocharged direct injection (DI) SI engine with optical access is presented and the analysis of the knock statistical occurrence obtained by the proposed model adds an innovative contribution to overcome the limitation of consolidated “average knock” analyses typical of a RANS approach
Alessandro D'Adamo; Sebastiano Breda; Stefano Fontanesi; Adrian Irimescu; Simona Silvia Merola; Cinzia Tornatore. A RANS knock model to predict the statistical occurrence of engine knock. Applied Energy 2017, 191, 251 -263.
AMA StyleAlessandro D'Adamo, Sebastiano Breda, Stefano Fontanesi, Adrian Irimescu, Simona Silvia Merola, Cinzia Tornatore. A RANS knock model to predict the statistical occurrence of engine knock. Applied Energy. 2017; 191 ():251-263.
Chicago/Turabian StyleAlessandro D'Adamo; Sebastiano Breda; Stefano Fontanesi; Adrian Irimescu; Simona Silvia Merola; Cinzia Tornatore. 2017. "A RANS knock model to predict the statistical occurrence of engine knock." Applied Energy 191, no. : 251-263.
Simona Silvia Merola; Cinzia Tornatore; Adrian Irimescu. Cycle-resolved visualization of pre-ignition and abnormal combustion phenomena in a GDI engine. Energy Conversion and Management 2016, 127, 380 -391.
AMA StyleSimona Silvia Merola, Cinzia Tornatore, Adrian Irimescu. Cycle-resolved visualization of pre-ignition and abnormal combustion phenomena in a GDI engine. Energy Conversion and Management. 2016; 127 ():380-391.
Chicago/Turabian StyleSimona Silvia Merola; Cinzia Tornatore; Adrian Irimescu. 2016. "Cycle-resolved visualization of pre-ignition and abnormal combustion phenomena in a GDI engine." Energy Conversion and Management 127, no. : 380-391.
Ever tighter restrictions on pollutant emissions, energy security and a continuous drive for improving fuel economy have extended the range of application for direct injection in spark ignition engines and promoted the use of alternative fuels. Direct injection features higher soot formation compared to external mixture preparation, and therefore, intensive research is performed for understanding the processes related to this pollutant category. This study looked into the effect of injection timing in a wall-guided direct injection spark ignition engine when gasoline was completely replaced with n-butanol. Thermodynamic measurements were coupled with optical investigations that provided improved insight into local distribution of diffusive flames during late combustion stages. These data were correlated with exhaust gas measurements of CO, HC and NOx, as well as opacity. The optimum setting for injection timing was found to be a compromise between intake airflow velocity and piston positioning that influenced wall impingement. Late injection resulted in reduced soot but higher HC emissions, as well as lower performance compared to the optimum point. Early fuel delivery had roughly the same effect on indicated mean effective pressure and stability, with the downside of increased opacity. These observations were detailed with data obtained through cycle-resolved imaging that showed different integral luminosities with respect to injection phasing and confirmed that fuel impingement on the piston crown is the main factor of influence for soot formation. Ultraviolet–visible spectroscopy in the late combustion phase was also applied in repetitive mode in order to provide better insight into cyclic variability of the emission intensity in the range specific for carbonaceous structures.
Simona Silvia Merola; Adrian Irimescu; Luca Marchitto; Cinzia Tornatore; Gerardo Valentino. Effect of injection timing on combustion and soot formation in a direct injection spark ignition engine fueled with butanol. International Journal of Engine Research 2016, 18, 490 -504.
AMA StyleSimona Silvia Merola, Adrian Irimescu, Luca Marchitto, Cinzia Tornatore, Gerardo Valentino. Effect of injection timing on combustion and soot formation in a direct injection spark ignition engine fueled with butanol. International Journal of Engine Research. 2016; 18 (5):490-504.
Chicago/Turabian StyleSimona Silvia Merola; Adrian Irimescu; Luca Marchitto; Cinzia Tornatore; Gerardo Valentino. 2016. "Effect of injection timing on combustion and soot formation in a direct injection spark ignition engine fueled with butanol." International Journal of Engine Research 18, no. 5: 490-504.
Given the instability in supply and finite nature of fossil fuels, alternative renewable energy sources are continuously investigated throughout the production–distribution-use chain. Within this context, the research presented in this work is focused on using butanol as gasoline replacement in a Direct Injection Spark Ignition engine. The impact of this fuel on the combustion processes was investigated using optical diagnostics and conventional methods in a transparent single cylinder engine. Three different load settings were investigated at fixed engine speed, with combined throttling and mixture strength control. The engine was operated in homogenous charge mode, with commercial gasoline and pure n-butanol fueling. High spatial and temporal resolution visualization was applied in the first phase of the combustion process in order to follow the early flame development for the two fuels. The optical data were completed with conventional measurements of thermodynamic data and pollutants emission at the exhaust. Improved performance was obtained in throttled stoichiometric mode when using the alternative fuel, while at wide open throttle, gasoline featured higher indicated mean effective pressure at both air–fuel ratio settings. These overall findings were correlated to flame characteristics; the alcohol was found to feature more distorted flame contour compared to gasoline, especially in lean conditions. Differences were reduced during throttled stoichiometric operation, confirming that mass transfer processes, along with fuel chemistry and physical properties, exert a significant influence on local phenomena during combustion.
Simona Silvia Merola; Cinzia Tornatore; Adrian Irimescu; Luca Marchitto; Gerardo Valentino. Optical diagnostics of early flame development in a DISI (direct injection spark ignition) engine fueled with n-butanol and gasoline. Energy 2016, 108, 50 -62.
AMA StyleSimona Silvia Merola, Cinzia Tornatore, Adrian Irimescu, Luca Marchitto, Gerardo Valentino. Optical diagnostics of early flame development in a DISI (direct injection spark ignition) engine fueled with n-butanol and gasoline. Energy. 2016; 108 ():50-62.
Chicago/Turabian StyleSimona Silvia Merola; Cinzia Tornatore; Adrian Irimescu; Luca Marchitto; Gerardo Valentino. 2016. "Optical diagnostics of early flame development in a DISI (direct injection spark ignition) engine fueled with n-butanol and gasoline." Energy 108, no. : 50-62.
This work investigates the effect of n-butanol on combustion processes in a direct injection spark ignition (DISI) engine through the analysis of flame front propagation. Specific attention is given to the sensitivity of n-butanol when changing injection mode in terms of timing and number of injections. Tests were carried out on an optically accessible single-cylinder DISI engine fueled with n-butanol and gasoline, alternatively. The engine is equipped with the head of a commercial turbocharged engine with similar geometrical specifications (bore, stroke, compression ratio). The head has four valves and a centrally located spark device. A conventional elongated hollow piston is used and an optical crown, accommodating a fused-silica window, is screwed onto it. The injector is side mounted and features six holes oriented so that the spray is directed toward the piston crown. During the experimental activity, injection pressure was maintained at 100 bar for all conditions; homogeneous charge conditions performed through single- and split-injection strategy (i.e., two injections per cycle) were compared for investigating their influence on combustion and emissions. Cycle-resolved visualization was applied in order to follow the combustion process, from ignition to the completion of flame front propagation. Macroscopic parameters (inflamed area, shape factor) and microscopic data (curvature distributions) were evaluated through image processing. All the optical data were correlated with conventional measurements of thermodynamic analysis and exhaust emissions. The effect of split injection was found to be relatively negligible for gasoline, while significant differences were recorded when switching from single to double injection for butanol. This points to a different mixture formation process, mainly related to the evaporative properties of butanol.
Simona Silvia Merola; Adrian Irimescu; Cinzia Tornatore; Gerardo Valentino. Effect of the Fuel-Injection Strategy on Flame-Front Evolution in an Optical Wall-Guided DISI Engine with Gasoline and Butanol Fueling. Journal of Energy Engineering 2016, 142, 1 .
AMA StyleSimona Silvia Merola, Adrian Irimescu, Cinzia Tornatore, Gerardo Valentino. Effect of the Fuel-Injection Strategy on Flame-Front Evolution in an Optical Wall-Guided DISI Engine with Gasoline and Butanol Fueling. Journal of Energy Engineering. 2016; 142 (2):1.
Chicago/Turabian StyleSimona Silvia Merola; Adrian Irimescu; Cinzia Tornatore; Gerardo Valentino. 2016. "Effect of the Fuel-Injection Strategy on Flame-Front Evolution in an Optical Wall-Guided DISI Engine with Gasoline and Butanol Fueling." Journal of Energy Engineering 142, no. 2: 1.
Sebastiano Breda; Alessandro D'adamo; Stefano Fontanesi; Nicola Giovannoni; Francesco Testa; Adrian Irimescu; Simona Silvia Merola; Cinzia Tornatore; Gerardo Valentino. CFD Analysis of Combustion and Knock in an Optically Accessible GDI Engine. SAE International Journal of Engines 2016, 9, 641 -656.
AMA StyleSebastiano Breda, Alessandro D'adamo, Stefano Fontanesi, Nicola Giovannoni, Francesco Testa, Adrian Irimescu, Simona Silvia Merola, Cinzia Tornatore, Gerardo Valentino. CFD Analysis of Combustion and Knock in an Optically Accessible GDI Engine. SAE International Journal of Engines. 2016; 9 (1):641-656.
Chicago/Turabian StyleSebastiano Breda; Alessandro D'adamo; Stefano Fontanesi; Nicola Giovannoni; Francesco Testa; Adrian Irimescu; Simona Silvia Merola; Cinzia Tornatore; Gerardo Valentino. 2016. "CFD Analysis of Combustion and Knock in an Optically Accessible GDI Engine." SAE International Journal of Engines 9, no. 1: 641-656.
Adrian Irimescu; Simona Silvia Merola; Cinzia Tornatore; Gerardo Valentino; Alberto Grimaldi; Eugenio Carugati; Stefano Silva. Plasma Assisted Ignition Effects on a DISI Engine Fueled with Gasoline and Butanol under Lean Conditions and with EGR. SAE Technical Paper Series 2016, 1, 1 .
AMA StyleAdrian Irimescu, Simona Silvia Merola, Cinzia Tornatore, Gerardo Valentino, Alberto Grimaldi, Eugenio Carugati, Stefano Silva. Plasma Assisted Ignition Effects on a DISI Engine Fueled with Gasoline and Butanol under Lean Conditions and with EGR. SAE Technical Paper Series. 2016; 1 ():1.
Chicago/Turabian StyleAdrian Irimescu; Simona Silvia Merola; Cinzia Tornatore; Gerardo Valentino; Alberto Grimaldi; Eugenio Carugati; Stefano Silva. 2016. "Plasma Assisted Ignition Effects on a DISI Engine Fueled with Gasoline and Butanol under Lean Conditions and with EGR." SAE Technical Paper Series 1, no. : 1.