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.

Dieselmoottorin staattiset virtausmittaukset

This Master's Thesis examines different methods of measuring the steady state flow of a diesel engine. Its goal was to lay foundations for future research on Particle Image Velocimetry (PlV). The thesis includes traditional in-cylinder measurements and literature research on PIV theory and its implementation in engine research. The focus of this study was the measurement of the vortex rotating around the cylinder axis, which has an important role in the formation of diesel emissions. The vortex is also known as the swirl. The swirl was measured using the paddle wheel method originally developed by AVL LIST GmbH. The experimental apparatus used in this thesis is not identical to the original, however; only the basic concept of the swirl measurement is the same. The apparatus was designed for a four-valve direct injection off-road diesel engine. The experiment results correlated well with the reference values presented in the literature. A further aim was to test the experiment method's dependency on pressure differences over the cylinder head. The results confirmed the assumption that the method is independent of the pressure level. PlV is a novel optical flow field velocity measurement method that is very well suited to combustion engine in-cylinder flow measurement. PlV is a complex measurement method requiring a high level of expertise. The steady state flow rig developed in this thesis is suitable for PlY measurements of the swirl. With a few modifications, it would also lend itself to measuring the valve discharge and intake channel flows. Preliminary designs for these modifications are included in the thesis. The results obtained with flow measurements have a critical role in research and simulation work aimed at decreasing the emissions of diesel engines. In particular, the local flow field velocities obtained with the PIV method will offer valuable reference data for flow simulation. PIV will be one of the most important tools in diesel engine development in the near future.Tässä diplomityössä tarkasteltiin erilaisia menetelmiä dieselmoottorin sylinterin sisäisten virtausten mittaamiseksi staattisessa virtauskoepenkissä. Diplomityössä tehtiin mittauksia perinteisellä mittausmenetelmällä ja perehdyttiin modernin optisen PIV-mittaustekniikan periaatteisiin ja käytännön toteutukseen. Erityinen pääpaino oli vaakapyörteen mittauksessa, jolla on tärkeä rooli dieselmoottorien päästöjen vähentämistyössä. Diplomityön tavoitteena oli luoda pohja jatkossa tehtävälle PIV-tekniikkaan perustuvalle tutkimustyölle. Vaakapyörteen mittaus suoritettiin käyttämällä potkurilapaa ilmaisemaan virtauskentän vaakapyörrekomponentti. Potkurilapa mittausmenetelmä perustuu AVL LIST GmbH:n kehittämään mittauslaitteistoon, joka tosin eroaa jokin verran tätä diplomityötä varten rakennetusta laitteistosta. Koelaitteiston lähtökohtana oli neliventtiilinen suoraruiskutustyökonedieselmoottori. Saadut tulokset täsmäsivät hyvin kirjallisuudessa esitettyjen vertailuarvojen kanssa. Kokeen aikana tutkittiin myös menetelmän riippuvuutta sylinterikannen yli vaikuttavasta paine-erosta. Kokeen tulokset tukivat menetelmän teorian perusteella tehtyä oletusta, ettei paineella ole vaikutusta suhteelliseen vaakapyörrelukuun. PIV on moderni optinen virtausmittausmenetelmä, jonka todettiin soveltuvan erinomaisesti sylinterin sisäisiin virtausmittauksiin. Menetelmä on erittäin haastava ja varsinkin sen soveltaminen moottoritutkimuksessa vaatii ehdotonta huippuosaamista. Diplomityössä toteutettu staattinen virtauskoepenkki soveltuu sellaisenaan vaakapyörteen PIV -mittauksiin. Työssä suunniteltiin alustavasti myös venttiili- ja imukanavirtausmittausten vaatimat muutokset koelaitteistoon. Virtausmittauksilla saadut tulokset ovat ensiarvoisen tärkeitä dieselmoottoreiden paastojen alentamiseen tähtäävässä tutkimus- ja mallinnustyössä. PIV -mittaustekniikalla saatavat paikalliset virtausnopeudet tarjoavat erinomaista vertailutietoa virtausmallinnukselle ja PIV -tekniikka tuleekin olemaan avainasemassa lähitulevaisuudessa dieselmoottoreiden kehitystyössä

Optical measurements of diesel fuel spray on medium speed engine

This Licentiate's Thesis examines experimental approach to fuel spray of medium speed diesel engine. Fuel spray and its local conditions determine the emission generation on compression ignition engine, where the combustion is traditionally mixing controlled. Optical measurement methods offer excellent way to study highly turbulent fuel sprays both in optical engines and in chambers. The gathered results can be utilized to increase the knowledge of basic fuel spray physics, develop combustion process and to offer reference data for numerical simulations. There are a lot of reported optical measurements of diesel fuel spray and combustion, but they have concentrated on small high speed engines. There have been only few studies focusing on large bore engines. Large bore engines are more challenging to modify for optical measurements, since their dimensions and high cylinder pressures, and also the emission legislation have not been as strict as with smaller engines. The thesis presents measurements of medium speed engine's fuels spray. Two optical measurement methods are presented -particle image velocimetry (PIV) and backlight imaging. The measurements have been carried out in cold chambers and in optical engine. The results gathered for the chamber measurements have excellent quality while results from engine measurement did have some quality problem. But both measurement results offered valuable information from in-cylinder phenomena of large bore medium speed diesel engine

Tutkimuksia vaihtoehtoisista polttoaineista työkonemoottoreihin

This experimental study examined the possible alternative fuels for heavy-duty engines, while the focus was on two specific renewable fuels: hydrotreated vegetable oil (HVO) and ethanol. These two fuels represent two extremities of fragmented fields of alternative fuels since HVO, as a "drop-in" fuel, can be di- rectly used in current diesel engine and ethanol will require significant modifications for existing engines. In this study ethanol was utilized in dual-fuel combustion concept, where ethanol was injected to intake manifold to form homogenous premixed charge to engine cylinder. Near engine top-dead-center, high-reactive diesel fuel was injected into cylinder to initialize the ignition. In studies with HVO the main focus was on exhaust gas emission – especially on nitrogen oxides (NOx) and on particulate matter (PM). As HVO has paraffinic compound and high cetane number, it enabled reduction of both NOx and PM emissions, while the effect on PM was the most evident. It was noteworthy that, as the trade-off between these two emission components is traditionally very strong, with HVO NOx and PM emissions decreased simultaneously. This behavior came more evident as the engine parameters (injection timing, exhaust gas recirculation and intake valve closure) were calibrated. In spite the PM emissions reduced significantly with HVO, the soot particle characteristics were found to be similar with the ones of fossil diesel fuel. The ethanol dual-fuel studies were carried out with both, neat ethanol and E85 blend (85% ethanol and 15% "gasoline-like" component). In these studies the focus was mainly on feasibility of the concept that was weighted mainly by the achieved ethanol share and exhaust gas emissions. The maximum ethanol share (energy based) at different engine conditions varied between circa 30% and 90%, while main limitiations were high cylinder pressure rise rate and the minimum diesel injection quantity of standard diesel injector. On exhaust gas emissions ethanol dual-fuel increased significantly both carbon monoxide and unburned hydrocarbon concentrations. This thesis focused on two different alternative fuel strategies that had significant difference on technological readiness level. HVO has already made its way to markets and has clear potential to reduce the harmful emissions of existing diesel engines. Ethanol in dual-fuel concept has evident potential, but to make its way to the markets, it will require significant research and development. The concept also will require dedicated engines, which will be a major drawback for commercial break-through. Additional advantage for HVO is that it can be distributed by existing diesel fuel logistic system, which is the case for ethanol in the most countries.Tämän väitöstutkimuksen tavoitteena oli vertailla työkonemoottoreiden vaihtoehtoisia polt- toaineita. Tutkimus keskittyi kahteen uusiutuvaan polttoainevaihtoehtoon: vetykäsiteltyyn kasviöljyyn (HVO) sekä etanoliin. Nämä kaksi polttoainetta edustavat erilaisia lähestymis- tapoja  haasteeseen korvata fossiiliset polttoaineet uusiutuvilla, mutta samalla ne myös edus- tavat ja todentavat polttoainevaihtoehtojen laajaa kirjoa. HVO:ta voidaan käyttää nykyisissä moottoreissa ilman teknisiä muutoksia, mutta etanolin käyttö vaati merkittäviä muutoksia moottoritekniikkaan. Tässä tutkimuksessa etanolia käytettiin hyödyntämällä kaksoispoltto-ainepalamista (engl. dual-fuel), jossa etanoli ruiskutettiin moottorin imusarjaan esisekoittu-neen ja homogeenisen seoksen muodostamiseksi. Etanoli sytytettiin ruiskuttamalla diesel-polttoainetta moottorin sylinteriin lähellä yläkuolokohtaa. Tutkimuksen HVO osuudessa päähuomio oli typen oksidi (NOx) ja hiukkaspäästöissä (PM), mitkä molemmat pienenivät tutkimuksissa - HVO:n parafiinisen rakenteen ja korkean setaani-luvun ansiosta. Erityisen huomionarvoista tuloksissa oli, että HVO:lla NOx- ja PM-päästöt laskivat yhtäaikaisesti, mikä poikkeaa tyypillisestä fossiilisella dieselillä havaittavasta kään-teisestä korrelaatiosta. Tutkimuksissa havaittiin myös, että moottoriparametrien (ruikutus-ajoitus, pakokaasujen takaisin kierrätys ja imuvent-tiilin ajoitus) uudelleen kalibroinnilla, PM- ja NOx-päästöt laskivat entisestään HVO:ta käytettäessä. Hiukkaspäästöjen voimakkaasta vähentymisestä huolimatta, hiukkasten rakenteessa ei havaittu eroa- vaisuuksia HVO:n ja fossiilisen dieselin välillä. Etanolikaksoispolttoaine tutkimuksessa käytettiin sekä puhdasta etanolia että E85 seosta, jossa on 85% etanolia ja 15% bensiinin kaltaisia hiilivetyjä. Pääpainopiste oli konseptin sovel-tuvuustutkimuksessa - erityisesti pakokaasupäästöjen ja etanoli energiaosuuden kannalta. Tutkimuksissa maksimi- etanoliosuus vaihteli välillä 30-90%, riippuen moottorin kuormapis-teestä. Osuutta rajoittavat suuri sylinteripaineen kulmakerroin sekä dieselsuuttimen mini-miruiskutusannos. Tutkimuksissa etanolikaksoispolttoainepalamiselle ominaista oli hiilimo-noksidi- ja hiilivetypäästöjen voimakas nousu. Tutkimuksessa verrattiin kahta uusiutuvaa vaihtoehtoista polttoainetta, joiden ominaisuudet ja tekninen kypsyysaste erosivat merkittävästi. HVO on jo kaupallinen tuote, sitä voidaan käyt-tää olemassa olevissa moottoreissa ja sillä saavutetaan selkeitä hyötyjän pakokaasupäästöissä. Etanolikaksois-polttoainepalaminen, selkeästä potentiaalista huolimatta, vaatii vielä pitkäl-listä tutkimusta ja kehitystä, ennen sen mahdollista kaupallistammista. HVO:n etuna on myös, että se soveltuu olemassa olevaan dieselpolttoaineen jakelujärjestelmään toisin kuin etanoli, jolle ei ole olemassa jakelujärjestelmää suurimmassa osassa maita

On the super adiabatic flame temperature (SAFT) of toluene primary reference fuels

Toluene primary reference fuel (TPRF) mixtures containing iso-octane (i-C8H18), n-heptane (n-C7H16), and toluene (C6H5CH3) are commonly used as gasoline surrogates. We report the occurrence of super adiabatic flame temperature (SAFT) during the premixed combustion of TPRF mixtures in air. Both 1-D premixed flame and 0-D (well-stirred) reactor configurations have been considered for chemical kinetic analysis with Cantera version 2.5.1. A recently developed detailed gasoline surrogate mechanism (C3MechV3.3) has been used for the 0-D reactor analysis. On the other hand, the flame structures have been simulated with a skeletal mechanism. To ensure accurate analysis, the mechanisms used in this work have been validated at SAFT relevant conditions against experimental data from literature. For the first time in literature, post-flame heat release and brute force reaction sensitivity analysis have been performed to identify important reactions contributing towards SAFT in TPRF surrogates. The degree of superadiabaticity for 1-D and 0-D cases have been expressed with non-dimensional parameters ξ1D and ξ0D respectively. The results show that ξ1D and ξ0D increase with the increase in iso-octane content in TPRF compositions, while n-heptane and toluene have minor influence on SAFT. Key chemical observations to the SAFT mechanism in gasoline surrogate mixtures include: 1) The competition between the exothermic reaction zone and the endothermic post-flame region causes SAFT. 2) Both 1-D flame and 0-D reactor analysis show that the reactions involving H, OH, and C3 species have major influence on SAFT. 3) Iso-octane augments SAFT as its β-scission product iso-butene (i-C4H8) influences the post-flame endothermicity and C3 species formation.Peer reviewe

Effects of blending 2,5-dimethylfuran and dimethyl ether to toluene primary reference fuels

Funding Information: This work was funded by Neste Oy. The authors acknowledge the computational resources provided by the Aalto Science-IT project. Publisher Copyright: © 2021 The Author(s)In the present work, renewable oxygenates 2,5-dimethylfuran (DMF) and dimethyl ether (DME) are considered as alternatives to fossil fuels for gasoline engines. The effects of blending DMF and DME on the combustion of gasoline surrogate are numerically studied. The gasoline surrogate is toluene primary reference fuel (TPRF) mixtures containing iso-octane, n-heptane, and toluene. Two skeletal mechanisms are proposed for the analysis: mechanism A with 504 species and 4212 reactions and mechanism B with 153 species and 740 reactions. These mechanisms are validated against a wide range of experimental data on ignition delay times and 1-D flames. The main findings of the present work are: 1) The ignition inhibiting effect of DMF dominates over the promoting effect of DME at 750 K and 25 bar when the total mole fraction of DMF and DME is less than 20 %. On the contrary, DME augments ignition with greater strength than the inhibition effect of DMF at 825 K and 25 bar. These observations are made for equimolar mixtureof DMF and DME blended with TPRF in varying proportions. 2) The laminar burning velocity change stays within 10% of TPRF-air values for 50% TPRF/25%DMF/25%DME-air mixture for 0.6 ≤ φ ≤ 1. 6. 3) DME mitigates additional soot emission caused by DMF blending with TPRF. 4) For the first time in literature, it is shown that the laminar burning velocity and the maximum slope of OḢ mole fraction in the stoichiometric flames vary linearly with the research octane number (RON) for TPRF-air mixtures.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

Impact of HVO blends on modern diesel passenger cars emissions during real world operation

Regulated and unregulated emissions from two Euro 6b diesel passenger cars tested using three different blends of hydrotreated vegetable oil (HVO), fossil diesel and commercial diesel (B7) were investigated at 23 °C and −7 °C using the World harmonized Light-duty vehicle Test Procedure at the Vehicle Emission Laboratory of the European Commission Joint Research Centre Ispra, Italy. The HVO blends used were: Neat HVO (100 vol% HVO), 30 vol% HVO and 7 vol% HVO. One of the vehicles was also tested using the three HVO blends on-road following a RDE compliant route. Overall, the use of different HVO blends and diesel did not lead to fuel related trends on the emissions of the tested vehicles in the laboratory nor on-road. However, HVO-100 resulted in∼4% lower CO2 emissions than the other fuel tested in all the studied conditions. Low ambient temperature caused an increase of the emissions of studied compounds (with the exception of NH3) with all tested blends. The experimental results showed that in many cases the observed outcomes were probably attributable to a combination of combustion effects, after-treatment effects, and their control strategy.JRC.C.4-Sustainable Transpor