Method to Reach High Substitution of an Ammonia Fueled Engine Using Dual Fuel RCCI and Active Combustion Control

Abstract

The International Marine Organization (IMO) has a goal of reaching 40% reduction of GHG emissions by 2030 and target of a full 50% reduction in marine fleet wide GHG emissions by 2050, while other organizations and governments desire to develop a path to Net-Zero GHG emissions by no later than 2050. To accomplish this, engines with near zero GHG emissions must be developed now. In addition to new ships, there is a large existing fleet of diesel fueled engines in the market today which are candidates for retrofit. Ammonia fueling of a diesel engine using dual-fuel combustion represents a viable zero-carbon fuel and combustion strategy suitable for long-haul / heavy-duty transportation due to its favorable storage properties of liquid at low tank pressure. The challenge, however, is ammonia is hard to ignite, slow to burn, and cool when it does burn which creates a significant challenge from a combustion point of view. Conventional dual fuel (CDF) will not be able to burn more than 50% NH3-Diesel ratios efficiently with acceptable combustion quality, thus, combustion enhancement is required to get ammonia to ignite and burn at higher substitution rates. Woodward has developed a fueling and combustion control strategy using diesel pilot injection as the ignition source and combustion accelerant. And using RCCI combustion (Reactivity Controlled Compression Ignition) controlled by Active Combustion Control (ACC) high ammonia-diesel substitution ratios (GSR) is demonstrated to burn as fast or faster than the baseline diesel. With the proportional reduction of carbon in the fuel and an appropriate ammonia slip catalytic technology, it is demonstrated that ammonia can be used as a GHG reduction fuel in dual-fuel diesel engines which can contribute to reduction in GHG emissions proportional to the NH3 substitution ratio. This is a technology which can be deployed today on both retrofit of existing engines as well as on new engines to meet the marine fleet average GHG emissions goals.

The future of ship engines: Renewable fuels and enabling technologies for decarbonization

“…Diesel and NH 3 can be possible combinations of fuels for RCCI operation to achieve high efficiency and low emissions (Figure 10 and 11). 41 An optically accessible test rig 39 under pressuretemperature and turbulence conditions similar to an IC engine has provided insights into relevant features of NH 3 -dodecane combustion in dual-fuel mode. The results were compared with methane-dodecane dual-fuel combustion under the same conditions.…”

“…RCCI concepts fueled by gasoline-diesel 75 and NGdiesel 57,76 was demonstrated on a 1.9 L passenger CI engine. Chiera et al 77,78 used the high-speed diesel engine (170 mm bore) with the same fuel equipment as the CDF (LNG + vaporizer + port-admitted gas + pilot-injected diesel). Enabling early diesel injection timing and active combustion control (ACC) provides Figure 23.…”

“…79,80 However, with controlled end-gas autoignition (CEGAI) enabled by ACC, fast combustion of natural gas, even with high EGR percentage, enables short burn duration and good combustion phasing, thus achieving high brake thermal efficiency and power density similar to that of diesel engines. 77 Emissions out of a three-way catalyst (TWC) are low enough to achieve Euro6/China6 emissions standards and have the potential to meet the expected targets of Euro7 and California emissions standards. With a TWC, engine-out methane emissions can be well-oxidized and reduced to minimum levels below 1 g/kWh.…”

“…83,84 Field trial demonstrations were conducted on B30 biodiesel 85 and B15 renewable diesel/hydrotreated vegetable oil 86 (Right) 10°-90°CA burn durations for CDC, CDF, and RCCI combustion over a range of gross indicated mean effective pressure (IMEP). 77 blends in existing ships. Developing low-cost, advanced biofuels for marine use must show compatibility with existing engine architectures.…”

“…(Left) HRRs for conventional diesel combustion, conventional dual fuel combustion, and RCCI dual fuel combustion. (Right) 10°-90°CA burn durations for CDC, CDF, and RCCI combustion over a range of gross indicated mean effective pressure (IMEP) 77.…”