This study was designed to evaluate a “what if” scenario in terms of using butanol as an oxygenate in place of ethanol in an engine calibrated for gasoline operation. No changes to the stock engine calibration were performed for this study. Combustion analysis, efficiency, and emissions of pure gasoline, 10% ethanol, and 10% butanol blends in a modern direct-injection four-cylinder spark-ignition engine were analyzed. Data were taken at engine speeds of 1000 rpm up to 4000 rpm with load varying from 0 N m (idle) to 150 N m. Relatively minor differences existed between the three fuels for the combustion characteristics such as heat release rate, 50% mass fraction burned, and coefficient of variation in indicated mean effective pressure at low and medium engine loads. However at high engine loads the reduced knock resistance of the butanol blend forced the engine control unit to retard the ignition timing substantially, compared with the gasoline baseline and, even more pronounced, compared with the ethanol blend. Brake specific volumetric fuel consumption, which represented a normalized volumetric fuel flow rate, was lowest for the gasoline baseline fuel due to the higher energy density. The 10% butanol blend had a lower volumetric fuel consumption compared with the ethanol blend, as expected, based on energy density differences. The results showed little difference in regulated emissions between 10% ethanol and 10% butanol. The ethanol blend produced the highest peak specific NOx due to the high octane rating of ethanol and effective antiknock characteristics. Overall, the ability of butanol to perform equally as well as ethanol from an emissions and combustion standpoint, with a decrease in fuel consumption, initially appears promising. Further experiments are planned to explore the full operating range of the engine and the potential benefits of higher blend ratios of butanol.

The new U.S. Renewable Fuel Standard requires an increase of ethanol and advanced biofuels to 36 billion gallons by 2022. Due to its high octane number, renewable character and minimal toxicity, ethanol was believed to be one of the most favorable alternative fuels to displace gasoline in spark-ignited engines. However, ethanol fuel results in a substantial reduction in vehicle range when compared to gasoline. In addition, ethanol is fully miscible in water which requires blending at distribution sites instead of the refinery. Butanol, on the other hand, has an energy density comparable to gasoline and lower affinity for water than ethanol. Butanol has recently received increased attention due to its favorable fuel properties as well as new developments in production processes. The advantageous properties of butanol warrant a more in-depth study on the potential for butanol to become a significant component of the advanced biofuels mandate. This study evaluates the combustion behavior, performance, as well as the regulated engine-out emissions of ethanol and butanol blends with gasoline. Two of the butanol isomers; 1-butanol as well as iso-butanol, were tested as part of this study. The evaluation includes gasoline as a baseline, as well as various ethanol/gasoline and butanol/gasoline blends up to a volume blend ratio of 85% of the oxygenated fuel. The test engine is a spark ignition, direct-injection, (SIDI), four-cylinder test engine equipped with pressure transducers in each cylinder. These tests were designed to evaluate a scenario in terms of using these alcohol blends in an engine calibrated for pump gasoline operation. Therefore no modifications to the engine calibration were performed. Following this analysis of combustion behavior and emissions with the base engine calibration, future studies will include detailed heat release analysis of engine operation without exhaust gas recirculation. Also, knock behavior of the different fuel blends will be studied along with unregulated engine out emissions.

Air separation membranes (ASMs) could potentially replace exhaust gas recirculation (EGR) technology in engines due to the proven benefits in NOx reduction but without the drawbacks of EGR. Previous investigations of nitrogen-enriched air (NEA) combustion using nitrogen bottles showed up to 70% NOx reduction with modest 2% nitrogen enrichment. The investigation in this paper was performed with an ASM capable of delivering at least 3.5% NEA to a single-cylinder spark-ignited natural gas engine. Low temperature combustion is one of the pathways to meet the mandatory ultra low NOx emissions levels set by regulatory agencies. In this study, a comparative assessment is made between natural gas combustion in standard air and 2% NEA. Enrichment beyond this level degraded engine performance in terms of power density, brake thermal efficiency (BTE), and unburned hydrocarbon emissions for a given equivalence ratio. The ignition timing was optimized to yield maximum brake torque for standard air and NEA. Subsequently, conventional spark ignition was replaced by laser ignition (LI) to extend lean ignition limit. Both ignition systems were studied under a wide operating range from ψ:1.0 to the lean misfire limit. It was observed that with 2% NEA, for a similar fuel quantity, the equivalence ratio (Ψ) increases by 0.1 relative to standard air conditions. Analysis showed that lean burn operation along with NEA and alternative ignition source, such as LI, could pave the pathway for realizing lower NOx emissions with a slight penalty in BTE.

This study was designed to evaluate a ‘what-if’ scenario in terms of using butanol as an oxygenate, in place of ethanol in an engine calibrated for gasoline operation. No changes to the stock engine calibration were performed for this study. Combustion analysis, efficiency and emissions of pure gasoline, 10% ethanol and 10% butanol blends in a modern, direct-injection four-cylinder, spark ignition engine were analyzed. Data was taken at engine speeds of 1000 RPM up to 4000 RPM with load varying from 0 Nm (idle) to 150 Nm. Relatively minor differences existed between the three fuels for the combustion characteristics such as heat release rate, 50% mass fraction burned, and coefficient of variation of indicated mean effective pressure at low and medium engine loads. However at high engine loads the reduced knock resistance of the butanol blend forced the engine control unit to retard the ignition timing substantially, compared to the gasoline baseline and even more pronounced compared to the ethanol blend. Brake specific volumetric fuel consumption which represented a normalized volumetric fuel flow rate, was lowest for the gasoline baseline fuel, due to the higher energy density. The 10% butanol blend had a lower volumetric fuel consumption compared to the ethanol blend, as expected based on energy density differences. Results showed little difference in regulated emissions between 10% ethanol and 10% butanol. The ethanol blend produced the highest peak specific NOx due to the high octane rating of ethanol and effective anti-knock characteristics. Overall, the ability of butanol to perform equally as well as ethanol from an emissions and combustion standpoint, with a decrease in fuel consumption, initially appears promising. Further experiments are planned to explore the full operating range of the engine and the potential benefits of higher blend ratios of butanol.

Total particulate number, size, and morphology were analyzed fbr several biofuel blends fired in a gasoline direct iajection engine. The particle sampling was taken at several common operating conditions using a Scanning Mobility Particle Sizer (SMPS) unit and a thermophoretic sampling device. The fuels tested were gasoline, EIO, E85, and iso-butanol-16 (iBl6) and the test points were for 25%, 50%, and 75% loads at 2,OOO rpm as well as idling. Exhaust gas recirculation (EGR) levels or fuel iniection parameters were not changed from the manufacturer's setup. There were significant differences in the levels of particulate number produced for the fuels and for the different loadlspeed combinations. E85 produced significantly lower particulate levels than did any of the other fuels tested. The ElO and iB16 produced higher levels than did the gasoline fuel in the entire load rage, due to the inherent thermo-physical and chemical properties of the al ¢ ohol fuels. At a 75% engine load, the paniculate size measured by the SMPS increased in the order of gasoline, ElO, and iB16. This trend quite agreed with the size data measured by a transmission electron microscope. The TEM observation ofparticle morphology showed that particle number concentrations were extremely low at 25% and 50% loads, particularly with the biofuel blends. Further detailed analysis in morphology for the biofuels revealed the nanostructures significantly different from those for the gasoline, exhibiting a lower level of graphitic structures with some amorphous structures.dynamometer setup, to allow it to function with the engine operating on the dynamometer; therefore, the engine eontrol unit is referred to as `dyne-ready.'The ignition system is the stock automotive ignition system supplied with the engine without modifications.

Air Separation Membranes (ASM) could potentially replace Exhaust Gas Recirculation (EGR) technology in engines due to the proven benefits in NOx reduction but without the drawbacks of EGR. Previous investigations of Nitrogen Enriched Air (NEA) combustion using nitrogen bottles showed up to 70% NOx reduction with modest 2% nitrogen enrichment. The investigation in this paper was performed with an ASM capable of delivering at least 3.5% NEA to a single cylinder spark ignited natural gas engine. Low Temperature Combustion (LTC) is one of the pathways to meet the mandatory ultra low NOx emissions levels set by regulatory agencies. In this study, a comparative assessment is made between natural gas combustion in standard air and 2% NEA. Enrichment beyond this level degraded engine performance in terms of power density, Brake Thermal Efficiency (BTE), and unburned hydrocarbon (UHC) emissions for a given equivalence ratio. The ignition timing was optimized to yield maximum brake torque for standard air and NEA. Subsequently, conventional spark ignition (SI) was replaced by laser ignition (LI) to extend lean ignition limit. Both ignition systems were studied under a wide operating range from ψ: 1.0 to the lean misfire limit. It was observed that with 2% NEA, for a similar fuel quantity, the equivalence ratio (Ψ) increases by 0.1 relative to standard air conditions. Analysis showed that lean burn operation along with NEA and alternative ignition source such as LI could pave the pathway for realizing lower NOx emissions with a slight penalty in BTE.

A comparative analysis of nitrogen and oxygen enriched combustion is presented in this paper. Nitrogen enrichment of intake air is proposed as an alternative to Exhaust Gas Recirculation (EGR). NOx reduction by EGR is not very promising due to engine reliability concerns and increased maintenance costs. Air separation membrane, on the other hand, is a potential strategy for NOx reduction due to uncompromised reliability of engine performance. Oxygen-rich and nitrogen-rich streams are produced by passing air through a nonporous polymeric membrane. Nitrogen Enriched Air (NEA) reduces NOx formation by lowering in-cylinder combustion temperatures but with a compromise in Fuel Conversion Efficiency (FCE). However, advanced ignition timing improves FCE considerably. Oxygen Enriched Air (OEA), on the other hand, improves FCE due to the availability of extra oxygen for better combustion which results in higher bulk gas temperatures and NOx emissions. This behavior could be controlled by retarding the ignition timing. Experimental results of nitrogen and oxygen enriched combustion of a Kohler M12 generator (converted to operate with natural gas) is presented in this paper. A 68% reduction in NOx and a 0.8% drop in FCE were observed at −30 ATDC ignition timing (IT) with 2.1% N2 enrichment (40 slpm). A 9% O2 enrichment (40 slpm) at −30 ATDC IT improved FCE by 1% but with higher NOx emissions. The increase in NOx emissions was minimal with a 2% improvement in FCE at −10 ATDC IT and 9% O2 enrichment (40 slpm). Some of the drawbacks encountered were engine misfire at higher concentrations of nitrogen enriched air and retarded ignition timing resulting in poor FCE. This paper discusses both the approaches and highlights the benefits of nitrogen enrichment using an air separation membrane over its counterpart for NOx reduction.