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Reactivity Controlled Compression Ignition (RCCI) is commonly mentioned as a potential efficient and clean combustion concept. This study makes the first evaluation of natural gas-diesel RCCI combustion for mid-speed marine engines. A state-of-the-art dual-fuel engine with 350 mm bore diameter is the basis for numerical simulations. GT-Power is used to create a one-dimensional air-path model. RCCI is simulated using TNO's multi-zone combustion model incorporating detailed chemical kinetics. The simulations aim to optimize engine efficiency, with peak incylinder pressure and emissions as constraints. The study shows best-point Indicated Efficiency of 47.8% is achievable (@75% load) using RCCI mode on stock engine hardware, while meeting IMO Tier III's NOx limit. This performance is similar to the best contemporary marine gas engines, but RCCI also provides additional methane and CO emission reductions. Thus, RCCI combustion can meet Europe's new rigorous Stage V limits, offering significant improvements in a marine engine's GHG footprint. Crucially, the study indicates an engine using hardware optimized for RCCI could deliver outstanding indicated efficiencies of 52%, with emissions of below 1g/kWh for all legislative species. This combination of high efficiency and ultra-low emissions would make RCCI combustion an attractive proposition for future marine propulsion and gen-set applications. ; fi=vertaisarvioitu|en=peerReviewed|

The focus on seeking alternative fuels for combustion engines has been on the environmental and political scene for many years. Simultaneously there is a more and more serious problem of non-degradable waste utilization. In the present work an attempt has been made to asses both of those aspects by proposing a tailor-made, 3-component mixture consisting of mineral diesel, crude rapeseed oil and waste tyre pyrolytic oil. It was proven that the addition of pyrolytic oil can improve some basic drawbacks of rapeseed oil / diesel mixtures like high density and viscosity or low cold filter plugging point. On the basis of maximum bio-component share and optimum physicochemical properties a best fuel sample (40% mineral diesel oil, 55% rapeseed oil and 5% pyrolytic oil fraction) had been selected for engine tests, performed on a light-duty multi-cylinder Compression Ignition (CI) engine with electronic, Common Rail (CR) injection system. The steady state tests were performed for two rotational speeds and two injection strategies (single and sequential fuel injection), for each of which a full load sweep was performed. The engine research included in-cylinder pressure analysis along with efficiency estimation and exhaust gas emission measurements. The research confirmed the assumption that the selected fuel mixture is suitable for modern CI engines. The specific fuel consumption was similar or lower for the tested fuel compared to standard diesel, except the cases were sequential injection was incorporated. Emissions remained on similar levels as for both fuels except Total HydroCarbons (THC) at sequential injection operation points, which correlated with lower fuel conversion efficiency.

The focus on seeking alternative fuels for combustion engines has been on the environmental and political scene for many years. Simultaneously there is a more and more serious problem of non-degradable waste utilization. In the present work an attempt has been made to asses both of those aspects by proposing a tailor-made, 3-component mixture consisting of mineral diesel, crude rapeseed oil and waste tyre pyrolytic oil. It was proven that the addition of pyrolytic oil can improve some basic drawbacks of rapeseed oil / diesel mixtures like high density and viscosity or low cold filter plugging point. On the basis of maximum bio-component share and optimum physicochemical properties a best fuel sample (40% mineral diesel oil, 55% rapeseed oil and 5% pyrolytic oil fraction) had been selected for engine tests, performed on a light-duty multi-cylinder Compression Ignition (CI) engine with electronic, Common Rail (CR) injection system. The steady state tests were performed for two rotational speeds and two injection strategies (single and sequential fuel injection), for each of which a full load sweep was performed. The engine research included in-cylinder pressure analysis along with efficiency estimation and exhaust gas emission measurements. The research confirmed the assumption that the selected fuel mixture is suitable for modern CI engines. The specific fuel consumption was similar or lower for the tested fuel compared to standard diesel, except the cases were sequential injection was incorporated. Emissions remained on similar levels as for both fuels except Total HydroCarbons (THC) at sequential injection operation points, which correlated with lower fuel conversion efficiency.