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The new emission legislation for sea-going vessels issued by the International Maritime Organization (IMO) requires drastic reduction in exhaust gas nitrogen oxides (NOx), and the combination of different primary methods can be an interesting solution without increasing remarkably the machinery. In this paper, the Miller cycle and the dilution with exhaust gas in the combustion chamber were tested to reach the Tier III limits for a four-stroke marine engine. In particular, the Miller cycle is used to reduce the in-cylinder temperature, and lower oxygen content in the combustion chamber is realized with cooled exhaust gas recirculation (EGR). Despite a remarkable reduction in NOx, the main drawback was a significant increase in fuel consumption. Split injection is combined with the abovementioned methods, in order to improve the engine efficiency. The novelty of this study consists in the simultaneous use of a split fuel injection, the Miller cycle and EGR in a marine-size application. Along this study, combining Miller timing with a relatively low EGR rate reduces NOx emissions by 90%. On the other hand, split injection does not bring significant advantages in fuel economy, although the results with very early pilot injection suggest further studies to be realized.

This work presents an alternative way of exhaust gas recirculation (EGR) systems implementation in the turbocharged compression ignition engines. This sort of EGR has been studied as well as the most commonly used EGR system, where the intake and the exhaust manifolds are directly connected with a hose. However, in authors opinion the setup described in this paper has not been investigated enough, as most of the research papers concentrate on a conventional configuration modeling and control design. A problem of overcoming a positive scavenging pressure drop and delivering high amount of EGR is addressed in this article. It comes from the fact that in this kind of engines the exhaust pressure is lower than the intake, making it difficult to deliver high and stable portion of EGR over the engine operating range. A generic mean value engine model is developed in this work and an initial simple control structure is proposed.

Limited crude oil resources and growing environmental awareness have raised a huge led to a huge motivation to seek new fuel alternatives for combustion engines. In this study the goal was to research the potential of ethanol as a compression ignition engine fuel utilizing dual-fuel combustion technology. In the studied DF (dual-fuel) concept, the primary fuel is injected into the intake manifold and it is ignited by injecting diesel fuel into the cylinder near the TDC (top-dead centre). A similar concept has been widely used in natural gas dual-fuel engines. By using ethanol as a primary fuel instead of gaseous fuel, the dual-fuel concept could be a true alternative for on-road and off-road heavy-duty vehicles without the obstacles of energy density and fuel distribution challenges of the gaseous fuels. The research engine in this study was a high speed heavy duty diesel engine modified for dual fuel combustion. The engine was equipped with a common-rail diesel injection system, which gave flexibility to modify the diesel injection to control the combustion. Especially the relationship between pilot and main diesel injection was investigated. The gathered results were promising. A maximum ethanol/diesel mass ratio of around 90% was achieved at high load conditions.

Fully paraffinic diesel fuel produced from hydrotreated vegetable oils (HVOs) is one alternative to increase the share of renewable energy in the transport sector. HVO fuel has also been shown to reduce exhaust emissions but, as the fuel contains no oxygen, even higher emissions reductions are possible by blending the HVO fuel with suitable oxygenate. From a large number of oxygenates, di-n-pentyl ether (DNPE) was chosen due to its favourable fuel properties (e.g. high cetane number and good solubility to diesel). In this paper, it was studied how fuel blend containing 2 wt.% oxygen (80 wt.% HVO and 20 wt.% DNPE) affects particulate and NOx emissions of a single-cylinder research engine. It was observed that the blend reduced emitted particulate mass 25-30% depending on load while the NOx emissions was changed under 5%. Thus, PM and NOx can possibly be both reduced e.g. by utilising EGR. In addition to emission reductions, the effects of the blend on the hygroscopic properties of produced exhaust particles were studied using a hygroscopic tandem differential mobility analyzer (HTDMA). The addition of oxygen into fuel led to a small increase in the hygroscopicity of exhaust particles.

Natural gas direct-injection (DI) with diesel pilot ignition using stratified combustion concept has been considered as a challenging and innovative technology to improve engine efficiency and meet stringent emission limits. Due to stratified mixture usually formed by late injection near the top dead center, the jet pressure ratio (PR) between injection pressure and motored in-cylinder pressure is usually very low, which may lead to poor jet mixing efficiency. In the present study, wall impingement was used to enhance the mixing process of low PR pulsed jet (PR

Hydrotreated vegetable oil (HVO) diesel fuel is a promising biofuel candidate that can complement or substitute traditional diesel fuel in engines. It has been already reported that by changing the fuel from conventional EN590 diesel to HVO decreases exhaust emissions. However, as the fuels have certain chemical and physical differences, it is clear that the full advantage of HVO cannot be realized unless the engine is optimized for the new fuel. In this article, we studied how much exhaust emissions can be reduced by adjusting engine parameters for HVO. The results indicate that, with all the studied loads (50%, 75%, and 100%), particulate mass and NOx can both be reduced over 25% by engine parameter adjustments. Further, the emission reduction was even higher when the target for adjusting engine parameters was to exclusively reduce either particulates or NOx. In addition to particulate mass, different indicators of particulate emissions were also compared. These indicators included filter smoke number (FSN), total particle number, total particle surface area, and geometric mean diameter of the emitted particle size distribution. As a result of this comparison, a linear correlation between FSN and total particulate surface area at low FSN region was found.

Conventional fossil diesel fuel and renewable diesel fuel based on hydrotreated vegetable oils (HVO) were compared regarding the oxidation characteristics of the generated soot particulate. The comparison was performed by utilizing a high-temperature oxidation tandem differential mobility analyser in which monodisperse soot aerosol was first selected and then heated in a high-temperature furnace. The particle size reduction caused by oxidation during the furnace treatment was then measured as a function of furnace temperature. The results indicate that soot oxidation is very similar between the studied fuels. This is supported by the obtained HR-TEM images and EELS-spectra which were practically indistinguishable between different fuels and engine conditions. The similar oxidation properties and surface structure between fossil and HVO-based diesel fuels imply that the oxidative aftertreatment devices designed for fossil diesel should work well also with the studied renewable diesel fuel.

Hydrotreating of vegetable oils or animal fats is an alternative process to esterification for producing biobased diesel fuels. Hydrotreated products are also called renewable diesel fuels. Hydrotreated vegetable oils (HVO) do not have the detrimental effects of ester-type biodiesel fuels, like increased NO x emission, deposit formation, storage stability problems, more rapid aging of engine oil or poor cold properties. HVOs are straight chain paraffinic hydrocarbons that are free of aromatics, oxygen and sulfur and have high cetane numbers. In this paper, NO x ‐ particulate emission trade-off and NO x ‐ fuel consumption trade-off are studied using different fuel injection timings in a turbocharged charge air cooled common rail heavy duty diesel engine. Tested fuels were sulfur free diesel fuel, neat HVO, and a 30% HVO + 70% diesel fuel blend. The study shows that there is potential for optimizing engine settings together with enhanced fuel composition. HVO could be used in optimized low emission diesel power trains in captive fleet applications like city buses, indoor fork-lift trucks, or mine vehicles.