On the Correlation between NOx Emissions and the Diesel Premixed Burn

Experiments on a modern DI Diesel engine were carried out: The engine was fuelled with standard Diesel fuel, RME and a mixture of 85% standard Diesel fuel, 5% RME and 10% higher alcohols under low load conditions (4 bar IMEP).During these experiments, different external EGR levels were applied while the injection timing was chosen in a way to keep the location of 50% heat release constant.Emission analysis results were in accordance with widely known correlations: Increasing EGR rates lowered NOx emissions. This is explained by a decrease of global air-fuel ratio entailing longer ignition delay. Local gas-fuel ratio increases during ignition delay and local combustion temperature is lowered. Exhaust gas analysis indicated further a strong increase of CO, PM and unburned HC emissions at high EGR levels. This resulted in lower combustion efficiency. PM emissions however, decreased above 50% EGR which was also in accordance with previously reported results.Besides those similar trends, fuel dependent differences in indicated thermal efficiency as well as CO, HC, NOx and especially PM emissions were observed. These differences were evaluated by detailed heat release analysis and explanation models based upon fuel characteristics as fuel viscosity and fuel distillation curve.Fuel spray evaporation and heat release were influenced by these fuel characteristics. Due to these characteristics it was concluded that RME has a higher tendency to form fuel rich zones at low load conditions than the other tested fuel types.Moreover it was found that improved fuel spray vaporisation is an option to improve exhaust emissions at low load conditions.

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“…Hence, both PM and NOx-emissions are lower with ICN improvers even though the overall fuel cetane number is virtually unaffected [17].…”

Section: Distillation Curvementioning

confidence: 97%

Detailed Heat Release Analyses with Regard to Combustion of RME and Oxygenated Fuels in an HSDI Diesel Engine

Horn¹,

Egnell²,

Johansson³

et al. 2007

SAE Technical Paper Series

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“…Since the peak of premixed heat release increases in Miller schemes, the in-cylinder temperature and pressure will increase rapidly in this period. This phenomenon not only leads to rough working possibly, but also weakens the ability to reduce NOx emission [27]. On the other hand, there is no obvious change in the soot emissions with low degree Miller cycle.…”

Section: Effects Of Miller Valve Timingmentioning

confidence: 99%

A Numerical Study on Combustion and Emission Characteristics of a Medium-Speed Diesel Engine Using In-Cylinder Cleaning Technologies

Feng

et al. 2015

Energies

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Abstract:In order to clarify the potential of internal purification methods on medium speed diesel engines to meet the IMO Tier III nitrogen oxide (NOx) emission regulations, combined 1-D engine working cycle simulation and 3-D CFD simulation were conducted to predict the performance and emissions of the engine under different valve close timings, geometric compression ratios, injection timings, and Exhaust Gas Recirculation (EGR) rates. The numerical results show that, as the inlet valve close timing is advanced, NOx is reduced by as much as 27%, but the peak of premixed combustion heat release rate is increased; this can weaken the ability to reduce NOx with the Miller cycle. Moreover, the peak of premixed combustion heat release rate is reduced when the geometric compression ratio is increased to 15.4, and linking with injection timing by delaying 6°CA can further reduce NOx by 55.3% from the baseline. Finally, over 80% NOx reduction can be achieved when the above schemes are combined with over 15% EGR. The NOx and soot can be reduced simultaneously by using moderate Miller cycle combination with moderate EGR, and the results show a large reduction of NOx and moderate reduction of soot. This can be a feasible technical solution to meet Tier III regulations.

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“…NOx emissions has been demonstrated [113]. Musculus has shown that as the premixedburn fraction increases, NOx emissions increase.…”

Section: Mixing: In the Literature A Connection Between The Premixedmentioning

confidence: 99%

“…Musculus showed that soot radiation from the flame zone may cool down the diffusion flame temperature and thus lead to a reduction in NOx emissions [113,114]. Since there is less soot in the diffusion flame region during the combustion of biodiesel, this can lead to a reduction of soot radiation from the flame region and result in higher flame temperatures [113,114].…”

Section: Adiabatic Flame Temperaturementioning

confidence: 99%

Hydrogen-Assisted IC Engine Combustion as a Route to Hydrogen Implementation

Boehman¹,

Haworth²

2008

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On the Correlation between NOx Emissions and the Diesel Premixed Burn

Cited by 74 publications

References 42 publications

Detailed Heat Release Analyses with Regard to Combustion of RME and Oxygenated Fuels in an HSDI Diesel Engine

Detailed Heat Release Analyses with Regard to Combustion of RME and Oxygenated Fuels in an HSDI Diesel Engine

A Numerical Study on Combustion and Emission Characteristics of a Medium-Speed Diesel Engine Using In-Cylinder Cleaning Technologies

Hydrogen-Assisted IC Engine Combustion as a Route to Hydrogen Implementation

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