The Potential of Fuel Metering Control for Optimising Unburned Hydrocarbon Emissions in Diesel Low Temperature Combustion

A modern common-rail diesel engine was used to investigate hydrocarbon emissions under low temperature diesel combustion conditions. In this work, various EGR ratios and fuel mixing strategies were applied under a series of fixed-load conditions to progressively lower the flame temperature, which is verified by progressively reduced NOx emission. During the tests, the concentrations of total hydrocarbons, representative light hydrocarbon species (methane, acetylene, and ethylene), and hydrogen gas were measured with a set of emission analyzers, FTIR, and H2 mass-spectrometer. The trend for light hydrocarbon emissions was identified to be a function of both load and EGR ratio. Hydrogen gas can be emitted in significant quantities with the application of very high EGR. Under ultra-low NOx production conditions for medium and high load conditions, the light hydrocarbon species can account for the majority of hydrocarbon emissions.

Download Full-text

Detailed Unburned Hydrocarbon Investigations in a Highly-Dilute Diesel Low Temperature Combustion Regime

SAE International Journal of Engines ◽

10.4271/2009-01-0928 ◽

2009 ◽

Vol 2 (1) ◽

pp. 858-879 ◽

Cited By ~ 51

Author(s):

Chad P. Koci ◽

Youngchul Ra ◽

Roger Krieger ◽

Mike Andrie ◽

David E. Foster ◽

...

Keyword(s):

Low Temperature ◽

Combustion Regime ◽

Low Temperature Combustion ◽

Unburned Hydrocarbon ◽

Temperature Combustion

Download Full-text

Effects of intake-port throttling on combustion behaviour in diesel low-temperature combustion

International Journal of Engine Research ◽

10.1177/1468087417732881 ◽

2017 ◽

Vol 19 (8) ◽

pp. 827-838 ◽

Cited By ~ 2

Author(s):

Oluwasujibomi Sogbesan ◽

Colin P Garner ◽

Martin H Davy

Keyword(s):

Low Temperature ◽

Load Condition ◽

Combustion Products ◽

Hydrocarbon Emissions ◽

Intake Port ◽

Low Temperature Combustion ◽

High Hydrocarbon ◽

Low Load ◽

Temperature Combustion ◽

Port Throttling

This article describes the effects of intake-port throttling on diesel low-temperature combustion at a low and medium load condition. These conditions were known for their characteristically high hydrocarbon emissions predominantly from over-mixed and under-mixed mixture zones, respectively. The investigation was carried out to supplement current findings in the literature with valuable information on the formation of high hydrocarbon emissions with increasing swirl levels generated by intake-port throttling. This was achieved through the use of cycle-resolved high hydrocarbon measurements in addition to cycle averaged emissions and in-cylinder pressure-derived metrics. While there was negligible overall effect at the moderately dilute low-load conditions, increasing swirl has been shown to be beneficial to premixing efficacy under highly dilute conditions with extended ignition delay. This potential advantage was found to be nullified by the swirl-induced confinement of fuel and combustion products to the central region of the cylinder leading to poor late cycle burn rates and increased smoke emissions. High hydrocarbon emissions from the squish and head quench regions were reduced by an increase in swirl ratio.

Download Full-text

Potential of in-cylinder exhaust gas recirculation stratification for combustion and emissions in diesel engines

Proceedings of the Institution of Mechanical Engineers Part D Journal of Automobile Engineering ◽

10.1177/0954407011420510 ◽

2011 ◽

Vol 226 (4) ◽

pp. 547-559 ◽

Cited By ~ 3

Author(s):

W Park ◽

S Lee ◽

S Choi ◽

K Min

Keyword(s):

Low Temperature ◽

Diesel Engines ◽

Exhaust Gas Recirculation ◽

Hydrocarbon Emissions ◽

Exhaust Gas ◽

Low Temperature Combustion ◽

Engine Simulation ◽

Temperature Combustion ◽

Soot Emissions ◽

Gas Recirculation

It is difficult to decrease the emissions of nitrogen oxides (NO x) and soot simultaneously in conventional diesel engines. Low-temperature combustion concepts have been studied in an effort to overcome this problem. Low-temperature combustion has the potential to reduce NO x and soot emissions, but it has many limitations, including narrow operating ranges, high carbon monoxide and hydrocarbon emissions, and difficulties with ignition control. Exhaust gas recirculation (EGR) stratification is another combustion concept used to reduce NO x and soot emissions simultaneously using the local non-uniformity of EGR gas instead of increasing the overall EGR rate. In this study, the EGR stratification concept was improved using computational fluid dynamics. First, a two-step piston was developed to maximize the stratified EGR effects by obtaining a favourable EGR distribution pattern and injecting fuel into the high-EGR region. Then, the possibility of combustion and emission control using stratified EGR was estimated. The ideally distributed EGR in the cylinder results showed that the region of locally high EGR effectively influences the combustion characteristics and, thus, horizontally and centrally stratified EGR has the potential to reduce the nitric oxide (NO x) and soot emissions at the same time. Engine simulation results also showed simultaneous reductions in the NO x and the soot emissions.

Download Full-text

Speciation Analysis of Light Hydrocarbons and Hydrogen Production During Diesel Low Temperature Combustion

ASME 2011 Internal Combustion Engine Division Fall Technical Conference ◽

10.1115/icef2011-60130 ◽

2011 ◽

Cited By ~ 4

Author(s):

Usman Asad ◽

Arturo Mendoza ◽

Kelvin Xie ◽

Marko Jeftic ◽

Meiping Wang ◽

...

Keyword(s):

Low Temperature ◽

Hydrogen Production ◽

Oxidation Catalyst ◽

Individual Species ◽

Hydrocarbon Emissions ◽

Exhaust Aftertreatment ◽

Boost Pressure ◽

Single Shot ◽

Low Temperature Combustion ◽

Temperature Combustion

The simultaneous reduction in engine-out NOx and soot emissions with diesel low temperature combustion (LTC) is generally accompanied by high levels of hydrocarbon (THC) and carbon monoxide (CO) emissions in the exhaust. To achieve clean diesel combustion in terms of low regulated emissions (NOx, soot, THC, and CO), the exhaust combustibles must be dealt with the exhaust aftertreatment (typically a diesel oxidation catalyst). In this work, engine tests were performed to realize LTC on a single-cylinder common-rail diesel engine up to 12 bar IMEP. A single-shot fuel injection strategy was employed to push the diesel cycles into LTC with exhaust gas recirculation (EGR). The combustibles in the exhaust were generally found to increase with the LTC load and were observed to be a function of the overall equivalence ratio. A Fourier transform infrared (FTIR) spectroscopy analysis of light hydrocarbon emissions found methane to constitute a significant component of the hydrocarbon emissions under the tested LTC conditions. The relative fraction of individual species in the hydrocarbons also changed, indicating a richer combustion zone and a reduction in engine-out THC reactivity. The hydrogen production was found to correlate consistently with the CO emissions, largely independent of the boost pressure or engine load under the tested LTC conditions. This research intends to identify the major constituents of the THC emissions and highlight the possible impact on exhaust aftertreatment.

Download Full-text