Future Combustion Technology for Synthetic and Renewable Fuels in Compression Ignition Engines (REFUEL) - Final report

This domestic project, Future Combustion Technology for Synthetic and Renewable Fuels in Compression Ignition Engines (ReFuel), was part of a Collaborative Task "Future Combustion Technology for Synthetic and Renewable Fuels in Transport" of International Energy Agency (IEA) Combustion Agreement. This international Collaborative Task is coordinated by Finland. The three-year (2009-2011) project was a joint research project with Aalto University (Aalto), Tampere University of Technology (TUT), Technical Research Centre of Finland (VTT) and Åbo Akademi University (ÅAU). The project was funded by TEKES, Wärtsilä Oyj, Neste Oil Oyj, Agco Sisu Power, Aker Arctic Technology Oy and the research partners listed above. Modern renewable diesel fuels have excellent physical and chemical properties, in comparison to traditional crude oil based fuels. Purely paraffinic fuels do not contain aromatic compounds and they are totally sulphur free. Hydrotreated Vegetable Oil (HVO) was studied as an example of paraffinic high cetane number (CN) diesel fuels. HVO has no storage and low temperature problems like the fatty acid methyl esters (FAMEs) have. The combustion properties are better than those of crude oil based fuels and FAME, because they have very high cetane numbers and contain no polyaromatic hydrocarbons (PAH). With low HVO density, viscosity and distillation temperatures, these advantageous properties allow far more advanced combustion strategies, such as very high exhaust gas recirculation (EGR) rates or extreme Miller timings, than has been possible with current fossil fuels. The implementation of these advanced combustion technologies, together with the novel renewable diesel fuel, brought significant nitrogen oxides (NOx), particulate matter (PM) emission reductions with no efficiency losses. The objective of ReFuel project was to develop new extremely low emission combustion technologies for new renewable fuels in compression ignition engines. The target was to decrease emissions at least by 70%. The scope was to utilize the physical and chemical properties of the renewable fuels that differ from properties of the traditional crude oil based fuels and to develop optimum combustion technologies for them. The project focused firstly, on paraffinic high cetane number fuels i.e. hydrotreated vegetable oil fuel as a typical representative of this kind of fuel and secondly, on fuels with high content of oxygenates. This was implemented by blending oxygenate to HVO fuel.

Monoterpene pollution episodes in a forest environment : indication of anthropogenic origin and association with aerosol particles

We used a monoterpene volume mixing ratio dataset measured from 12 June 2006 to 24 September 2007 and from 1 June 2008 to 3 March 2009 at the SMEAR II station to quantify the magnitude of anthropogenic monoterpene emissions aside from biogenic origins, to examine the anthropogenic sources, and to look at other associated pollutants. We discuss the relations between increased monoterpene mixing ratios and particle concentrations. We also characterize chemical properties of aerosol particles during two monoterpene pollution episodes in case studies. Out of 580 days analyzed, anthropogenic monoterpene pollution episodes were found on 341 (58.8%) days. The average monoterpene mixing ratio increased from 0.19 to 0.26 ppbv due to the presence of anthropogenic monoterpenes, which is equal to an increase of 36.8%. The observed anthropogenic monoterpenes were mostly from the Korkeakoski sawmill. Other gas pollutants might occasionally be emitted during the episodes, but did not show clear association with anthropogenic monoterpenes. Aerosol particle concentrations substantially increased during episodes, and monoterpene mixing ratios showed strong connections with Aitken mode particles both in number and volume concentrations. Particles associated with monoterpene episodes reached a CCN (cloud concentration nucleus) size. The chemical characterizations of aerosol particles in case studies show that the increase in aerosol particle mass was mainly from secondary organic aerosol

Dieselsuihkututkimuksia modernissa dieselmoottorissa

The public defense on 20th May 2020 at 12:00 will be organized via remote technology. Link: https://aalto.zoom.us/j/65180381929 Zoom Quick Guide: https://www.aalto.fi/en/services/zoom-quick-guideIn this doctoral thesis, diesel injection and spray formation in modern diesel engines were studied. The goal of this thesis is to answer some fundamental questions and hypotheses about injection and spray formation in modern diesel engines. First, the fundamental spray characteristics of renewable diesel were studied under non-evaporative conditions. Second, these spray characteristics were studied under extremely high cylinder pressure. Third, the spray characteristics of conical nozzle orifice geometry were studied. Finally, the spray characteristics of biofuel blends were studied in an optical engine during late-post-injection, which is relevant to exhaust gas after-treatment. Studies showed that the spray tip penetrations with renewable diesel and petroleum diesel were similar under non-evaporative conditions. The spray angle was slightly wider, spray tip velocities were higher, and the inner delay of the injector was shorter with renewable diesel. The conclusion of the study was that there is no need to redesign the combustion chamber or readjust the injection parameters due to wall impact or spray collision. Very high in-cylinder pressure and density have a significant effect on spray penetration. Higher gas phase mixing was observed with higher in-cylinder density. No negative aspects were found for extremely high gas density. When the spray tip penetration was compared between different conical geometries and a cylindrical nozzle orifice geometry, a clear difference was not found under non-evaporative conditions. This result is inconsistent with earlier studies. The main reasons for this inconsistency may be the different approach and high injection pressure. The spray angle was smaller, and the mass flow rate higher, with conical nozzle orifice geometry. Standard hydraulic flow measurement with an injection pressure of 100 bar underestimates the flow rate of conical orifices due to lack of cavitation. Different hypotheses about higher spray tip penetration and cylinder wall-wetting during late post-injection were studied. A clear difference in the spray tip penetration was not observed when three different fuel blends were compared. The conditions that would be needed for droplets to evaporate before reaching the cylinder wall are not attained with very late injection. Hence, hypotheses that the amount of fuel ending up on the cylinder walls is higher with biofuels are unlikely. The main reason for oil dilution rate differences between fuel blends is probably related to the volatility of the fuel fraction, or because the control unit increases the volume of the post-injections due to the lower volumetric heat value of renewable diesel.Väitöskirjassa on tutkittu dieselin ruiskutusta ja polttoainesuihkun muodostumista nykyaikaisissa dieselmoottoreissa. Tavoitteena on vastata perustavanlaatuisiin kysymyksiin ja hypoteeseihin dieselin ruiskutuksesta ja polttoainesuihkun muodostumisesta nykyaikaisissa dieselmoottoreissa. Väitöskirjassa tutkittiin polttoainesuihkuja uusiutuvalla dieselillä höyrystymättömissä olosuhteissa, erittäin korkeassa sylinteripaineessa ja kartiomaisella suutinaukolla. Lopuksi biopolttoaine- sekoitusten polttoainesuihkua tutkittiin optisessa moottorissa myöhäisen jälkiruiskutuksen aikana liittyen pakokaasujen jälkikäsittelyyn. Tutkimukset osoittivat, että uusiutuvan dieselin ja raakaöljydieselin polttoainesuihkun kärjen eteneminen ei eroa höyrystymättömissä olosuhteissa. Uusiutuvalla dieselillä suihkun avautumiskulma oli leveämpi, kärjen etenemisnopeus suurempi ja suuttimen sisäinen viive lyhyempi. Johtopäätöksenä oli, että palotilaa ei tarvitse suunnitella uudelleen eikä ruiskutusparametreja tarvitse muuttaa, koska polttoainesuihkut eivät törmää toisiinsa tai sylinterin seinään. Erittäin korkealla sylinteripaineella ja -tiheydellä on merkittävä vaikutus polttoainesuihkun etenemiseen. Kaasufaasin havaittiin sekoittuvan paremmin korkealla sylinterin tiheydellä. Erittäin korkealla sylinteripaineella ei havaittu olevan negatiivisia vaikutuksia suihkun muodostumiseen ja sekoittumiseen. Suuttimen kartiomaisuuden ei havaittu vaikuttavan suihkun kärjen etenemiseen höyrystymättömissä olosuhteissa. Havainto on ristiriidassa aiempien tutkimusten kanssa. Syy tähän saattaa olla erilainen lähestymistapa aiheeseen ja korkeampi ruiskutuspaine verrattuna aiempiin tutkimuksiin. Suihkun avautumiskulma oli pienempi ja massavirta suurempi kartiomaisella suutinaukolla. Standardin mukainen hydraulinen virtausmittaus 100-baarin ruiskutuspaineella aliarvioi kartiomaisen suuttimen virtausnopeutta kavitaation puutteen vuoksi. Aiemmin oli esitetty hypoteeseja biopolttoainesuihkujen kärjen nopeammasta etenemisestä ja sen vaikutuksesta sylinterin seinämien kastumiseen. Väitöskirjatutkimuksessa vertailtiin kolmea erilaista polttoainesekoitusta. Niiden välillä ei havaittu merkittävää eroa suihkun kärjen tunkeutumisessa. Hyvin myöhäisessä ruiskutuksessa edellytykset pisaroiden haihtumiseksi ennen sylinteriseinämään törmäämistä eivät täyty. Näin ollen hypoteesi, jonka mukaan sylinterin seinämille päätyvä polttoaineen määrä on biopolttoaineilla korkeampi, on todennäköisesti väärä. Öljyn laimenemisnopeuden erojen pääasiallinen syy polttoainesekoitusten välillä liittynee polttoaineen haihtuvuuteen tai siihen, että moottorin ohjausyksikkö lisää ruiskutusannosta uusiutuvan dieselin alhaisemman lämpöarvon vuoksi

Dieselpolttoainesuihkujen vertailu optisin menetelmin

In this master's thesis, diesel fuel sprays were studied by optical method. The main aim of this thesis was to compare fuel spray characteristics between crude oil based EN 590 diesel and hydro treated vegetable oil (HVO). HVO is produced from vegetable oils and animal fats using hydro treatment. HVO is used in diesel engines. In Finland, HVO is produced by the brand name NExBTL. Another objective of this thesis was to study the effects of comparatively high injection pressure and small injector orifice. Optical measurements of diesel spray were performed in a cold pressurized test rig. The fuel injection was arranged with a modem common rail fuel injection system and all injection parameters such as injection pressure and time were completely controlled. The fuel spray measurements were made with high speed backlight photography based on short laser pulse and digital image processing. The master's thesis includes a theoretical section and an experimental section. In the theoretical section, firstly, emission formation of diesel process and properties of bio fuels are presented briefly. Secondly, fundamentals of spray characteristics are determined and a literature survey is carried out about the effects of variation of injection parameters. In the experimental section, results of the measurements are presented with conclusions, accuracy of measurements is discussed and finally recommendations for future research subjects are proposed. According to the fuel spray measurements, no significant and consistent difference was founded between crude oil based EN 590 diesel and HVO. However, some results were inconsistent whereupon further studies are highly recommended with various injection parameters.Tässä diplomityössä tutkittiin dieselpolttoainesuihkuja optisin menetelmin. Tutkimuksen päätavoitteena oli vertailla polttoainesuihkujen ominaisuuksia maaöljypohjaisen EN 590 dieselin ja vetykäsitellyn kasviöljyn välillä. Vetykäsitelty kasviöljy on kasvi- ja eläinperäisistä rasvoista vetykäsittelyllä valmistettua dieselmoottorikäyttöön tarkoitettua polttoainetta, jota valmistetaan Suomessa tuotenimellä NExBTL. Samalla tutkittiin tavallista korkeamman ruiskutuspaineen ja hieman normaalia pienemmän suutinreiän vaikutusta polttoainesuihkun ominaisuuksiin. Dieselpolttoainesuihkujen optiset mittaukset tehtiin paineistetussa koekammiossa säädettävällä polttoaineensyöttöjärjestelmällä, jolla voidaan vapaasti säätää polttoaineen ruiskutuspainetta ja -aikaa. Mittauksissa käytettiin taustavalokuvausta, jossa polttoainesuihku valaistaan pulssilaserilla ja kuvataan digitaalikameralla vastakkaisesta suunnasta, jonka jälkeen kuvat voidaan analysoida tietokoneohjelmilla. Työ koostuu teoriaosuudesta ja kokeellisesta osuudesta. Teoriaosuudessa käsitellään ensin lyhyesti päästöjen muodostumista dieselmoottorissa sekä tarkastellaan biopolttoaineiden keskeisiä ominaisuuksia. Tämän jälkeen esitellään polttoainesuihkujen tärkeimpiä ominaisuuksia ja selvitetään miten ruiskutusparametrit ovat vaikuttaneet näihin ominaisuuksiin aiemmissa tutkimuksissa. Kokeellisessa osuudessa esitellään mittaustulokset johtopäätöksineen, tarkastellaan mittausten luotettavuutta ja esitetään näkemys jatkotutkimuksen tarpeesta. Mittauksissa ei voitu havaita johdonmukaista ja merkittävää eroa polttoainesuihkujen keskeisissä ominaisuuksissa EN 590 dieselin ja vetykäsitellyn kasvisöljyn välillä. Tulokset olivat kuitenkin osittain ristiriitaiset ja näiden mittausten perusteella on suositeltavaa tutkia aihetta laajemmalla mittausmatriisilla

HVO, RME and diesel fuel combustion in an optically accessible compression ignition engine

The current paper investigates the spray and combustion characteristics of hydrotreated vegetable oil (HVO), petrol diesel (EN590), blends of HVO with petrol diesel (70% EN590 and 30% HVO), and rapeseed oil methyl esters (RME) in an optically accessible compression ignition engine. Mie scattering and natural luminosity imaging are employed to measure the liquid spray and combustion behaviors. The spray and combustion processes are divided into four stages based on optical imaging. The morphology and quantitative analysis based on imaging provides a method for visualizing the in-cylinder spray and combustion behavior with four test fuels. The ignition delay and combustion characteristics detected from optical measurements are compared to those determined from cylinder pressure. The results show that the ignition delay of HVO and RME occurs earlier and the flame propagation at the premixed combustion stage proceeds faster compared to EN590 and HVO30. The spray and combustion characteristics of HVO30 are similarto EN590. However, ignition occurs earlier for HVO30 due to the higher CN. Comparison of the HVO and RME shows that there is a marginal difference in the ignition delay for these two fuels. However, the combustion duration of RME is shorter than that of HVO.Peer reviewe

Spray dynamics of HVO and EN590 diesel fuels

This investigation aims at quantifying the spray dynamics of diesel-like injection at the steady stage. A 1D model based on momentum flux conservation and combined with Gaussian radial profiles is derived to predict the axial and radial velocity, fuel concentration, liquid volume fraction and density distribution within the steady spray field. To validate the model over a range of conditions, global quantities such as spray tip penetration, spray cone angle, spray tip velocity, and spray volume was measured by diffused back-illumination imaging. The spray characteristics of hydrotreated vegetable oil (HVO) and European standard diesel fuel (EN590) under different ambient air conditions (36 kg/m3 and 115 kg/m3) are compared to further predict the local velocity, fuel concentration, liquid volume fraction and density distribution. The present results indicate that an accurate model of diesel-like spray evolution can be obtained for different fuel types and ambient air densities.Peer reviewe

Biofuel blend late post-injection effects on oil dilution and diesel oxidation catalyst performance

In this article, the effects of different biofuel–diesel blends on engine oil dilution and diesel oxidation catalyst performance during late post-injections were investigated. The engine tests were made with an off-road diesel engine under low load conditions at 1200 r/min engine speed. During the experiments, oil samples were periodically taken from the engine oil and later analyzed. Emissions and temperatures before and after the diesel oxidation catalyst were also measured. The fuels studied were fossil EN590:2013 diesel fuel, 30 vol.% biodiesel (fatty acid methyl ester) and 30 vol.% hydrotreated vegetable oil, which is a paraffinic diesel fuel fulfilling the EN15940 specification. The novelty of the study is based on two parts. First, similar late post-injection tests were run with blends of both hydrotreated vegetable oil and fatty acid methyl ester, giving a rare comparison with the fuels. Second, oil dilution and the fuel exit rates during normal mode without the late post-injections were measured. Theresults showed the oil dilution and the diesel oxidation catalyst performance to be very similar with regular diesel and hydrotreated vegetable oil blend. With the fatty acid methyl ester blend, increased oil dilution, smaller temperature rise in the diesel oxidation catalyst and higher emissions were measured. This indicates that during diesel particulate filter regeneration by late post-injections, fatty acid methyl ester blends increase fuel consumption and require shorter oil change intervals, while hydrotreated vegetable oil blends require no parameter changes.Peer reviewe