Teemu Sarjovaara

Hydrotreated Vegetable Oil (HVO) as a Renewable Diesel Fuel: Trade-off between NOx, Particulate Emission, and Fuel Consumption of a Heavy Duty Engine

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.

Reductions in Particulate and NOx Emissions by Diesel Engine Parameter Adjustments with HVO Fuel

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 NO(x) 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 NO(x). 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.

Study of Miller timing on exhaust emissions of a hydrotreated vegetable oil (HVO)-fueled diesel engine

The effect of intake valve closure (IVC) timing by utilizing Miller cycle and start of injection (SOI) on particulate matter (PM), particle number, and nitrogen oxide (NOx) emissions was studied with a hydrotreated vegetable oil (HVO)-fueled nonroad diesel engine. HVO-fueled engine emissions, including aldehyde and polyaromatic hydrocarbon (PAH) emissions, were also compared with those emitted with fossil EN590 diesel fuel. At the engine standard settings, particle number and NOx emissions decreased at all the studied load points (50%, 75%, and 100%) when the fuel was changed from EN590 to HVO. Adjusting IVC timing enabled a substantial decrease in NOx emission and combined with SOI timing adjustment somewhat smaller decrease in both NOx and particle emissions at IVC −50 and −70 °CA points. The HVO fuel decreased PAH emissions mainly due to the absence of aromatics. Aldehyde emissions were lower with the HVO fuel with medium (50%) load. At higher loads (75% and 100%), aldehyde emissions were slightly higher with the HVO fuel. However, the aldehyde emission levels were quite low, so no clear conclusions on the effect of fuel can be made. Overall, the study indicates that paraffinic HVO fuels are suitable for emission reduction with valve and injection timing adjustment and thus provide possibilities for engine manufacturers to meet the strictening emission limits. Implications: NOx and particle emissions are dominant emissions of diesel engines and vehicles. New, biobased paraffinic fuels and modern engine technologies have been reported to lower both of these emissions. In this study, even further reductions were achieved with engine valve adjustment combined with novel hydrotreated vegetable oil (HVO) diesel fuel. This study shows that new paraffinic fuels offer further possibilities to reduce engine exhaust emissions to meet the future emission limits. Supplementary Materials: Supplementary materials are available for this paper. Go to the publishers online edition of the Journal of the Air & Waste Management Association for a complete list of analysed PAH compounds.

Experimental Investigation of Characteristics of Transient Low Pressure Wall-impinging Gas Jet

This paper describes an investigation of the jet structure and mixture formation process of wall-impinging gas jet injected by a low pressure gas injector in a constant volume chamber at room conditions. The tracer-based planar laser-induced fluorescence (PLIF) technique is applied to qualitatively evaluate the mixture formation process. The macroscopic structure and concentration distribution of wall-impinging jet were studied based on a series of time evolution high-definition images. In particular, the effects of injection pressure on characteristics of turbulence were investigated. Experimental results show that vortex structure with large scale is one of important characteristics for wall-impinging jet, and the interaction among jet flow, impingement wall, and surrounding air plays a dominant role in the mixture formation. The comparative study about the effect of injection pressure on wall-impinging jet reveals higher injection leads to higher mixing efficiency and better mixture formation.

Influence of the in-cylinder gas density and fuel injection pressure on the combustion characteristics in a large-bore diesel engine:

Engine research is going toward higher specific power and downsizing. This topic is of increasing interest in compression-ignition engines, due to high output demand and more restrictive legislation. This study focuses on the influence of in-cylinder gas density and fuel injection pressure on the combustion and performance in a large-bore medium speed research engine. From a baseline setup close to a commercial engine, the specific power density was augmented by higher in-cylinder pressure ranging from 200 to 300 bar. This corresponds to gas density between 65 and 90 kg/m3 at top dead center. In addition, fuel injection pressure was varied between 1500 and 2400 bar. Based on the literature, this is the first study to report engine operation with 300 bar cylinder pressure. The results show that ignition delay is significantly reduced by increasing the injection pressure, while gas density has only a moderate effect. In addition, specific nitrogen oxides increase strongly with higher injection pressure but only moderately with higher gas density. Running with high gas density permits to improve the engine fuel economy. The test outcomes also show that the combustion duration can be decreased by increasing the in-cylinder density.

Modeling and control of diesel engines with a high-pressure exhaust gas recirculation system

Abstract 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.