Efficiency and Emissions Characteristics of Partially Premixed Dual-Fuel Combustion by Co-Direct Injection of NG and Diesel Fuel (DI<sup>2</sup>)

Florea, Radu; Neely, Gary D.; Abidin, Zainal; Miwa, Jason

doi:10.4271/2016-01-0779

Cited by 37 publications

(42 citation statements)

References 25 publications

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“…15–17 In other investigations, it has been noted that as the NG EOI is advanced relative to the partially premixed HRR peak, significant reduction of PM emissions can be achieved, although this is at the cost of higher unburned CH 4 and N O x emissions. 15,17,20,37 These observations motivate improved understanding of the role the RIT plays in primary heat release.…”

Section: Primary Ng Combustionmentioning

confidence: 96%

Parametric study of pilot-ignited direct-injection natural gas combustion in an optically accessible heavy-duty engine

Rochussen

McTaggart-Cowan²,

Kirchen

2019

International Journal of Engine Research

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Natural gas is an attractive fuel for internal combustion engines in light of its potential for reduced greenhouse gas and particulate emissions, and significant reserves. To facilitate natural gas use in compression ignition engines, pilot-ignited direct-injection natural gas combustion uses a small pilot injection of diesel to ignite a more significant direct injection of natural gas. Compared to modern diesel combustion, this strategy is a promising technology for the reduction of CO2 emissions while retaining diesel-like efficiency without a significant CH4 emission penalty. To further develop this technology, investigation of in-cylinder combustion processes is needed to identify the primary fuel conversion processes. The objective of this work was to provide a framework of conceptual understanding by identifying key processes in a typical pilot-ignited direct-injection natural gas combustion event and characterizing their sensitivity to fuel injection parameters. A parametric sweep of injection pressure, natural gas injection duration, and relative timing of the diesel pilot and natural gas injections was performed in an optically accessible 2 L single-cylinder engine. Combined heat release rate and OH*-chemiluminescence reaction zone analysis was used to demarcate the transition from ignition reactions to primary natural gas heat release. Five distinct combustion processes were identified: (1) pilot auto-ignition; (2) natural gas ignition; (3) rapid, distributed partially premixed natural gas combustion; (4) non-premixed combustion; and (5) late-cycle oxidation. While natural gas ignition was found to be insensitive to injection pressure, it was strongly affected by the time between pilot and natural gas injections. Reducing the relative injection timing from +8° to −6° resulted in the primary natural gas heat release transitioning from non-premixed, to distributed partially premixed, to stratified premixed flame propagation as a result of increasing natural gas premixing. The presented measurements and analysis serve to refine an initial conceptual model of the combustion process and lay the groundwork for future, more focused studies of pilot-ignited, direct-injection natural gas combustion.

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Section: Primary Ng Combustionmentioning

confidence: 96%

Parametric study of pilot-ignited direct-injection natural gas combustion in an optically accessible heavy-duty engine

Rochussen

McTaggart-Cowan²,

Kirchen

2019

International Journal of Engine Research

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“…High flow rates are needed especially during this phase. Westport, [36] to [42,44], has traditionally used a main injection of the LNG following a pilot injection of the diesel, but more recently has also explored the opportunity to inject part of the LNG before, and part of the LNG after the diesel, [39,41,42,44]. This latter activity is both experimental and computational.…”

Section: Methodsmentioning

confidence: 99%

“…It is also very well known, from the experience by Westport, references [36][37][38][39][40][41][42], to name a few references, with thousands of heavy-duty trucks, diesel engines converted to diesel-LNG by using their patented dual-fuel diesel-LNG injector; when replacing the main injection of the diesel with a main injection of the LNG, there is no penalty in the fuel conversion efficiency, nor in the BMEP output. The Westport results are supported by engine performance simulations, engine laboratory experiments, and the experience of heavy-duty truck drivers.…”

Section: Introductionmentioning

confidence: 99%

Numerical Analysis of High-Pressure Direct Injection Dual-Fuel Diesel-Liquefied Natural Gas (LNG) Engines

Boretti¹

2020

Processes

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Dual fuel engines using diesel and fuels that are gaseous at normal conditions are receiving increasing attention. They permit to achieve the same (or better) than diesel power density and efficiency, steady-state, and substantially similar transient performances. They also permit to deliver better than diesel engine-out emissions for CO2, as well as particulate matter, unburned hydrocarbons, and nitrous oxides. The adoption of injection in the liquid phase permits to further improve the power density as well as the fuel conversion efficiency. Here, a model is developed to study a high-pressure, 1600 bar, liquid phase injector for liquefied natural gas (LNG) in a high compression ratio, high boost engine. The engine features two direct injectors per cylinder, one for the diesel and one for the LNG. The engine also uses mechanically assisted turbocharging (super-turbocharging) to improve the steady-state and transient performances of the engine, decoupling the power supply at the turbine from the power demand at the compressor. Results of steady-state simulations show the ability of the engine to deliver top fuel conversion efficiency, above 48%, and high efficiencies, above 40% over the most part of the engine load and speed range. The novelty of this work is the opportunity to use very high pressure (1600 bar) LNG injection in a dual fuel diesel-LNG engine. It is shown that this high pressure permits to increase the flow rate per unit area; thus, permitting smaller and lighter injectors, of faster actuation, for enhanced injector-shaping capabilities. Without fully exploring the many opportunities to shape the heat release rate curve, simulations suggest two-point improvements in fuel conversion efficiency by increasing the injection pressure.

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“…Reference [51] uses the Westport HPDI ICE to study both diffusion-controlled and partially premixed combustion strategies. The partially premixed combustion is called DI 2 .…”

Section: F Diesel-lng Ices Randdmentioning

confidence: 99%

Advances in Diesel-LNG Internal Combustion Engines

Boretti

2020

Applied Sciences

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Diesel-LNG internal combustion engines (ICEs) are the most promising light and heavy-duty truck (HDT) powering solution for a transition towards a mixed electric-hydrogen renewable energy economy. The diesel-liquid CH 4 ICEs have indeed many commonalities with diesel-liquid H 2 ICEs, in the infrastructure, on-board fuel storage, and injection technology, despite the fact H 2 needs a much lower temperature. The paper outlines the advantages of dual fuel (2F) diesel-LNG ICEs developed adopting two high-pressure (HP) injectors per cylinder, one for the diesel and one for the LNG, plus super-turbocharging. The diesel-LNG ICEs provide high fuel energy conversion efficiencies, and reduced CO 2 , PM, and NOx emissions. Super-turbocharging permits the shaping of the torque curve while improving acceleration transients. Diesel-LNG ICEs may also clean up the air of background pollution in many polluted areas in the world. Computational results prove the steady-state advantages of the proposed novel design. While the baseline diesel model is a validated model, the 2F LNG model is not. The perfect alignment of the diesel and diesel-LNG ICE performances proven by Westport makes however the proposed results trustworthy. the lean-burn operation, with combustion occurring with excess air [23]. The reduction of both PM and NOx is achieved by after-treatment. As the after-treatment is imperfect, the diesel combustion strategies are dictated by the best trade-off between PM and NOx emissions.The use of a fuel with reduced carbon content, that is also gas in normal conditions, such as the NG, has major advantages in both CO 2 and engine-out PM emissions. Even if injected liquid, the NG rapidly vaporizes and quickly mixes with the air. The PM emissions are usually negligible. Not having the constraint of the best PM-NOx trade-off to design the injection profile, the injection profile can be shaped to achieve reduced NOx production. Thus, NG indirectly also permits to reduce the NOx engine-out emissions. NG (CH 4 ) has a smaller carbon-to-hydrogen ratio vs. the diesel (C 13.5 H 23.6 ) also featuring a higher lower heating value. Less CO 2 is emitted to produce the same output of the diesel with the same η. As NG is also gas in normal conditions, this practically reduces to zero the PM emissions. In the dual-fuel (2F) operation, the only PM originates from the pilot diesel.As NG is a low cetane but a high octane number fuel, it is difficult to use alone in a CI ICE The issue is solved by using the 2F diesel-NG design with the diesel-injection-ignition [24,25]. A small amount of the DI diesel fuel ignites mixed with air within the cylinder. The NG that is injected prior, or after the diesel, then burns premixed, i.e. diffusion. The first phase of combustion translates into a rapid pressure build-up. The rate of combustion of the second phase is determined by the injection rate of the NG.One issue with fuels that are gases under normal conditions is the specific volume, as the density of the gas under normal conditions is much lower than...

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Efficiency and Emissions Characteristics of Partially Premixed Dual-Fuel Combustion by Co-Direct Injection of NG and Diesel Fuel (DI²)

Cited by 37 publications

References 25 publications

Parametric study of pilot-ignited direct-injection natural gas combustion in an optically accessible heavy-duty engine

Parametric study of pilot-ignited direct-injection natural gas combustion in an optically accessible heavy-duty engine

Numerical Analysis of High-Pressure Direct Injection Dual-Fuel Diesel-Liquefied Natural Gas (LNG) Engines

Advances in Diesel-LNG Internal Combustion Engines

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Efficiency and Emissions Characteristics of Partially Premixed Dual-Fuel Combustion by Co-Direct Injection of NG and Diesel Fuel (DI2)

Cited by 37 publications

References 25 publications

Parametric study of pilot-ignited direct-injection natural gas combustion in an optically accessible heavy-duty engine

Parametric study of pilot-ignited direct-injection natural gas combustion in an optically accessible heavy-duty engine

Numerical Analysis of High-Pressure Direct Injection Dual-Fuel Diesel-Liquefied Natural Gas (LNG) Engines

Advances in Diesel-LNG Internal Combustion Engines

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Product

Resources

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Efficiency and Emissions Characteristics of Partially Premixed Dual-Fuel Combustion by Co-Direct Injection of NG and Diesel Fuel (DI²)