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Valorization of n-butanol as gasoline replacement in a DISI engine and the effect of injection phasing

Merola S. S., Irimescu A., Valentino G., Colmenares-Quintero R. F., Rodas Y. A. L.

Prace Naukowe Instytutu Nafty i Gazu

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2015

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nr 204

169--185

EN

Alcohols represent a viable replacement for gasoline> with the advantages of providing improved energy security as well as reduced environmental impact. Compared to ethanol, which holds the majority of the alternative fuels market share in transportation, n-butanol features higher energy density and better compatibility with existing fuel systems designed for gasoline. Given this background, the present study investigated the use of pure n-butanol fuelling of a wall guided direct injection spark ignition (DISI) engine with optical accessibility through the piston crown. Different injection timings were considered, and variations of soot emissions were evaluated based on smoke measurements. Besides thermodynamic investigations through the analysis in-cylinder pressure traces, flame chemiluminescence was applied for a more detailed view of the chemical processes during combustion. All conditions were benchmarked to gasoline fuelling, thus giving comprehensive information on the effect of fuel properties. It was found that the change in injection timing, even by a relatively reduced crank angle, had a significant effect on the smoke at the exhaust, for both fuel types. Early fuel delivery resulted in high soot emissions, while late injection had the opposite effect. No soot- nitrogen oxides trade-off point, specific for diesel power units, could be identified, but the optimum injection strategy resulted in high engine output and low particulate emissions. The alcohol featured increased sensitivity not only to changes in the start of injection, but also showed the potential for very low smoke. The investigations further emphasize the importance of air-fuel mixture formation and also identified ways to minimize the environmental impact of DISI engines through the development of optimized control strategies.

2

Spray Combustion Investigation through Optical Techniques in a Prototype Compression Ignition Engine fuelled with n-Butanol-Diesel Blends

Marchitto L., Merola S. S., Tornatore C., Valentino G.

Prace Naukowe Instytutu Nafty i Gazu

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2015

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nr 204

199--215

EN

The increasing energy demand from emerging countries and the simultaneous fossil oil shortage promote the use of alternative fuels. Even if gasoline and diesel continue to dominate automotive market, the use of non-conventional fuels such as biodiesel or alcohols is growing. Exhaust emissions and performance of compression ignition engines fuelled with diesel-alcohol fuel blends have been widely investigated. On the other hand, a deeper understanding of in-cylinder combustion is necessary as the different chemical physical properties of alcohols, such as oxygen content, volatility and cetane number affect the ignition, combustion mechanism and the pollutants formation. This work reports results of cycle resolved visualization and UV-visible optical imaging, carried out in an optically accessible compression ignition engine. Two different blends of diesel and n-butanol were tested: 20% and 40% of n-butanol by volume. The effect of n-butanol concentration on flame lift-off length and soot formation was investigated. Exhaust Gas Recirculation (O2 at intake 17%) was used for further reducing the local temperature peak. The combined effect of EGR and high oxygen content of n-butanol/diesel blends induced a simultaneous reduction of both NOx and soot emission. The correlation of optical measurements with thermodynamic and exhaust emission analysis allowed to emphasize the role of n-butanol oxygen content in the soot oxidation process.

3

Optical investigations of alternative fuel combustion in common rail compression ignition engine

Merola S. S., Tornatore C., Valentino G., Marchitto L.

Journal of KONES

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2012

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Vol. 19, No. 3

279-288

EN

The increasing global energy demand and the decreasing fossil-energy resources are enhancing the interest in the combustion characteristics of alternative fuels for diesel engines. Alternative-fuel combustion has been studied in detail in light-duty diesel engines, even if the comparison of test results from different chemical nature fuels obtained by integrated optical methodologies is lacking. Thus, it is the primary objective of the present study to characterize the combustion of selected alternative fuels in an optical common rail compression ignition engine by high-speed luminescence imaging and natural emission spectroscopy. The effects of the fuels on in-cylinder spray combustion and soot formation were investigated through UV-visible digital imaging and natural emission spectroscopy. Experiments were performed in a single cylinder high swirl compression ignition engine. The test engine was optically accessible and equipped with a common rail multi-jets injection system. Several injection pressures and timings at two EGR rates were tested. Digital imaging allowed characterizing the evaporating spray and the combustion process. UV-visible emission spectroscopy was used to follow the evolution of the combustion process chemical markers. Chemiluminescence signal due to OH was identified. The soot spectral feature in the visible wavelength range was correlated to soot engine out emissions. Conventional and optical data related to diesel fuel blended with gasoline and butanol were compared.

4

In - cylinder OH and CO2* detection in SI engine through UV natural emission spectroscopy

Merola S. S., Tornatore C., Marchitto L., Valentino G.

Journal of KONES

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2012

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Vol. 19, No. 4

429-437

EN

Processes of the combustion of liquid fuels and solid are more complex than combustion of fuel gases. With reference to liquid fuels occur additionally processes of vaporization of the fuel, and with reference to solid fuels - decomposition of the solid phase with processes of melting and vaporization, pyrolysis, or gasification. This simultaneous and also different influence of different parameters is sometimes a reason of incorrect interpretation of experimental results. The study of the theoretical model of the combustion process concerning of liquid and solid fuels and which then the model takes into account also the gas- phase, because combustion processes take place in this phase, and occurs the interaction of the phase gas- and liquid or the solid one. The theoretical model is presented basing on experimental initial researches realized in a model with reference to liquid fuels and solid ones. Researches realized in the constant volume chamber with measurements of the pressure during the process of the combustion with the use of quick photography and with measurement of the distribution of the velocity in the spray of the fuel and droplet measurements by means the laser Doppler equipment LDV and PDPA. There were obtained a good agreement of findings experimental researches with the theoretical model. Generally, on the combustion velocity of liquid fuels and solid one significant influence has a kind (laminar, temporary and turbulent) and the thickness of the thermal boundary layer.

5

Effect of butanol blend on in-cylinder combustion process. Part 1: Spark ignition engine

Tornatore C., Marchitto L., Mazzei A., Valentino G.

Journal of KONES

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2011

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Vol. 18, No. 2

427-438

EN

The addition of alcohol to conventional hydrocarbon fuels for a spark-ignition engine can increase the fuel octane rating and the power for a given engine displacement and compression ratio. In this work, the influence of butanol addition to gasoline in a port fuel-injection, spark ignition engine was investigated. The experiments were realized in a single cylinder ported fuel injection SI engine with an external boosting device. The optical accessible engine was equipped with the head of commercial SI turbocharged engine with the same geometrical specifications (bore, stroke, compression ratio) as the research engine. The effect on the spark ignition combustion process of 40% n-butanol blended in volume with gasoline was investigated by cycle resolved visualization. The engine worked at low speed, medium boosting and wide open throttle. Changes in spark timing and fuel injection phasing were considered in order to investigate normal and abnormal combustion. Comparisons between the parameters related to the flame luminosity and to the pressure signals were performed. The duration of injection for butanol blend was increased to obtain stoichiometric mixture. In open valve injection condition, the fuel deposits on intake manifold and piston surfaces decreased, allowing a reduction in fuel consumption. Butanol blend granted the performance levels of gasoline and in open valve injection allowed to minimize the abnormal combustion effects and the formation of ultrafine carbonaceous particles.

6

Effect of butanol blend on in-cylinder combustion process. Part 2: Compression ignition engine

Tornatore C., Marchitto L., Mazzei A., Valentino G., Corcione F. E., Merola S. S.

Journal of KONES

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2011

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Vol. 18, No. 3

473-483

EN

To meet the future stringent emission standards, innovative diesel engine technology, exhaust gas after-treatment, and clean alternative fuels are required. Oxygenated fuels showed tendency to decrease internal combustion engine emissions. In the same time, advanced fuel injection modes can promote further reduction in pollutants at the exhaust without penalty for the combustion efficiency. One of the more interesting solutions is provided by the premixed low temperature combustion (LTC) mechanism jointly to lower-cetane, higher-volatility fuels. In this paper, to understand the role played by these factors on soot formation, cycle resolved visualization, UV-visible optical imaging were applied in an optically accessed high swirl multi-jets compression ignition engine. Combustion tests were carried out using two fuels: commercial diesel and a blend of diesel with n-butanol. The fuels were tested at 70MPa injection pressure and different timings. At late injection timing coupled to high EGR rate (50%), the blends increased the ignition delay allowing operating in partially premixed LTC (PPLTC) regime in which the fuel is completely injected before the start of combustion. Strong reduction in engine out emissions of smoke and NOx were obtained with a little penalty on engine efficiency. This limitation was overcome operating at earlier injection timing in which a mixing controlled combustion (MCC) LTC regime was realized. In this regime, a good compromise between low engine out emissions and efficiency was achieved.