Dual-Fuel Combustion Characterization on Lean Conditions and High Loads

Pettinen, Rasmus; Kaario, Ossi; Larmi, Martti

doi:10.4271/2017-01-0759

Cited by 19 publications

(10 citation statements)

References 16 publications

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“…Furthermore, it was observed that the HRR shapes are sensitive to the TDC temperature, equivalence ratio, and operating load conditions. These HRR shapes are found to be different from the shapes obtained at high loads and higher diesel-pilot amounts for the similar base engine in Pettinen [21], where a short combustion phase of diesel-pilot and entrained premixed methane-air combustion is followed by the bulk methane-air mixture combustion. In contrast to Pettinen, the current DF combustion test yielded a considerably longer time available for diesel-pilot to mix with in-cylinder charge due to lower engine load, and hence lower gas pressure and density.…”

Section: Effect Of φCh4 and Intake Air Temperature (Ttdc)contrasting

confidence: 73%

“…In the first column of Figure 11, there is a weaker flame propagation and the combustion at PR=16.5% is the less luminous compared to the PR = 27.5% case. However, with an increase in the pilot ratio, there is more diesel fuel available to entrain the larger volume of the methane-air mixture that causes an increase in the burnt fraction of the mixture and leads to a successful flame propagation, as also explained by Alla et al [13] and Pettinen [21]. Therefore, at this lean condition (φCH4=0.55) with higher pilot ratio, a more luminous and an early start of combustion can be seen in the second column of Figure 11.…”

Section: Effect Of Pilot Ratio (Pr)mentioning

confidence: 87%

“…Each test point was run for 150 cycles, out of which 22 cycles were combustion cycles. The pilot fuel used in the test runs was commercial diesel fuel (EN590) [21] and the main fuel was 99.9% methane. Methane was injected into intake air manifold at 3.6 bar by two methane injectors at -365 CAD ATDC that was then inducted into the cylinder through the intake valves along with the intake air.…”

Section: Operating Methodsmentioning

confidence: 99%

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An Optical Characterization of Dual-Fuel Combustion in a Heavy-Duty Diesel Engine

Ahmad¹,

Aryal²,

Ranta³

et al. 2018

SAE Technical Paper Series

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Dual fuel (DF) combustion technology as a feasible approach controlling engine-out emissions facilitates the concept of fuel flexibility in diesel engines. The abundance of natural gas (90-95% methane) and its relatively low-price and the clean-burning characteristic has attracted the interest of engine manufacturers. Moreover, with the low C/H ratio and very low sooting tendency of methane combined with high engine efficiency, makes it a viable primary fuel for diesel engines. However, the fundamental knowledge on in-cylinder combustion phenomena still remains limited and needs to be studied for further advances in the research on DF technology. The objective of this study is to investigate the ignition delay with the effect of, 1) methane equivalence ratio, 2) intake air temperature and 3) pilot ratio on the diesel-methane DFcombustion. Combustion phenomenon was visualized in a single cylinder heavy-duty diesel engine modified for DF operations with an optical access. The high-speed natural luminosity (NL) imaging technique was employed to record the temporally resolved incylinder combustion event at an operating load of approx. 10 bar IMEP at 1400 rpm. The results show that flame propagation becomes stable and sustained with an increase in either of the methane equivalence ratio, intake air temperature, or diesel amount. However, the sensitivity of each effect on the flame propagation and ignition delay was observed to be different. The effect of these parameters on DF combustion has been characterized with the help of NL images and corresponding cylinder pressure and net heat-release rate (HRR) data. The study also presents a detailed discussion on the analyzed ignition delay trends.

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Section: Effect Of φCh4 and Intake Air Temperature (Ttdc)contrasting

confidence: 73%

Section: Effect Of Pilot Ratio (Pr)mentioning

confidence: 87%

Section: Operating Methodsmentioning

confidence: 99%

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An Optical Characterization of Dual-Fuel Combustion in a Heavy-Duty Diesel Engine

Ahmad¹,

Aryal²,

Ranta³

et al. 2018

SAE Technical Paper Series

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“…Various aspects of dual-fuel combustion (Diesel pilot ignited) have been studied up to date in complete engines [5][6][7], single cylinder engines [8][9][10][11][12][13][14][15], optical engines [15][16][17][18] as well as rapid compression machines [19][20][21]. The approach of most of the engine experiments was to substitute part of the Diesel fuel (by reducing the injection duration) with premixed methane while monitoring the exhaust emissions and heat release rate.…”

Section: Introductionmentioning

confidence: 99%

Optical Investigation of Sooting Propensity of n-Dodecane Pilot/Lean-Premixed Methane Dual-Fuel Combustion in a Rapid Compression-Expansion Machine

Srna¹,

Bruneaux²,

Rotz³

et al. 2018

SAE Int. J. Engines

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The sooting propensity of dual-fuel combustion with n-dodecane pilot injection in a lean-premixed methane-air charge has been investigated using an optically accessible Rapid Compression-Expansion Machine to achieve engine relevant pressure and temperature conditions at start of pilot injection. A Diesel injector with a 100 µm single-hole coaxial nozzle, mounted at the cylinder periphery, has been employed to admit the pilot fuel.The aim of this study was to enhance the fundamental understanding of soot formation and oxidation processes of n-dodecane in presence of methane in the air charge by parametric variation of methane equivalence ratio, charge temperature and pilot fuel injection duration. The influence of methane on ignition delay and flame extent of the pilot fuel jet has been determined by simultaneous OH* chemiluminescence and Schlieren imaging. The sooting behavior of the flame has been characterized using the 2D-DBI imaging methodology. The apparent soot black-body temperature has been measured 1D-resolved along the injector axis by applying an imaging spectrograph.Addition of methane into the air charge considerably prolongs the ignition delay with an increasing effect under less reactive conditions and with higher methane equivalence ratios. Therefore, the influence of methane on the formation of soot is two-fold: in case of short pilot injection, the presence of methane was found to decrease the soot formation due to the leaner pilot fuel mixture at time of ignition. For longer pilot fuel injections, methane enhances the soot production by decreasing oxygen availability and introducing additional carbon. In all cases, methane strongly defers the oxidation of soot due to the lower availability of oxygen.

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“…Under emissions-optimized operational strategy Euro 6 (heavy-duty) compliance of engine-out NO x emissions [3] and particulate matter emissions [4] (though exceeding the particulate number limit) has already been demonstrated in a dual-fuel engine at only slightly compromised efficiency (1-2%). However, several authors observed a tradeoff between low soot and NOx emissions on one hand, and low UHC emissions and high thermal efficiency on the other hand [3,5,6,7,8,9,10]. Considering these findings it becomes clear that in order to fulfill the development goals 1.)…”

mentioning

confidence: 99%

POMDME as an Alternative Pilot Fuel for Dual-Fuel Engines: Optical Study in a RCEM and Application in an Automotive Size Dual-Fuel Diesel Engine

Srna

Barro

Herrmann³

et al. 2018

SAE Technical Paper Series

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D ual-fuel natural gas engines are seen as an attractive solution for simultaneous reduction of pollutant and CO 2 emissions while maintaining high engine thermal efficiency. However, engines of this type exhibit a tradeoff between misfire as well as high UHC emissions for small pilot injection amounts and higher emissions of soot and NO X for operation strategies with higher pilot fuel proportion. The aim of this study was to investigate POMDME as an alternative pilot fuel having the potential to mitigate the emissions tradeoff, enabling smokeless combustion due to high degree of oxygenation, and being less prone to misfire due to its higher cetane number. Furthermore, POMDME can be synthetized carbon neutrally. First, characteristics of POMDME ignition in methane/ air mixture and the transition into premixed flame propagation were investigated optically in a rapid compression-expansion machine (RCEM) by employing Schlieren and OH* chemiluminescence imaging. A single-hole coaxial injector mounted at the cylinder periphery was used to admit POMDME or n-dodecane as the reference pilot fuel. In the second stage, POMDME was applied as a pilot-fuel in a VW 2 l 4-cylinder industrial Diesel engine modified for dual-fuel operation. Engine performance with POMDME and EN590 Diesel pilot-fuels was compared. In the RCEM, in air, dodecane and POMDME exhibit similar ignition delay times. In methane/air mixtures, ignition of both pilot fuels was deferred with increasing methane content, with stronger influence on POMDME than on dodecane. Indication of pilot-fuel over-mixing was observed for the shortest considered POMDME injections. In the engine experiment, while keeping the total combustion equivalence ratio constant, POMDME was found to have shorter ignition delays than Diesel fuel, attributed to its higher cetane number. At constant engine load using POMDME instead of Diesel pilot fuel, stable operation with lower pilot-fuel energy and mass input was possible along with soot mass reduction to close to zero.

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Dual-Fuel Combustion Characterization on Lean Conditions and High Loads

Cited by 19 publications

References 16 publications

An Optical Characterization of Dual-Fuel Combustion in a Heavy-Duty Diesel Engine

An Optical Characterization of Dual-Fuel Combustion in a Heavy-Duty Diesel Engine

Optical Investigation of Sooting Propensity of n-Dodecane Pilot/Lean-Premixed Methane Dual-Fuel Combustion in a Rapid Compression-Expansion Machine

POMDME as an Alternative Pilot Fuel for Dual-Fuel Engines: Optical Study in a RCEM and Application in an Automotive Size Dual-Fuel Diesel Engine

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