Search

Most biofuels in use today are obtained from feedstock that can also be used for food-grade agriculture, creating an ever growing ethical problem. In the search for so-called second-generation (2G) sustainable transportation fuels that are not in competition with food production, a woody biomass-based biofuel production technique is currently under development. The process development is integrated in the Belgian federal government funded Ad-Libio project and its process outcome is mainly consisting of hydrocarbons containing five to six carbon atoms, that differ significantly from gasoline or diesel fuel. Since the Ad-Libio fuel composition can be changed, a fuel blend calculator with integrated fuel database has been developed. This tool enables fast fuel property calculations, so quick decisions can be made on the fuel production process outcome. After a first screening with the calculator, a fuel research engine was used to evaluate the combustion properties of the promising fuel blends, enabling quick in-house experimental verification of the calculations. The ultimate goal is to produce a drop-in fuel, made out of wood waste, that can be fully interchanged with the gasoline fuels in use today, enabling sustainable transportation for modern and legacy combustion engine-powered vehicles.

The negative impact of transport on climate has led to incentives to increase the amount of renewable fuels used in internal combustion engines (ICEs). Oxygenated, liquid biofuels are promising alternatives, as they exhibit similar combustion behaviour to gasoline. In this article, the effect of the different biofuels on engine efficiency, combustion propagation and emissions of a gasoline-optimised direct injected spark ignited (DISI) engine were evaluated through engine experiments. The experiments were performed without any engine hardware modifications. The investigated fuels are gasoline, four alcohols (methanol, ethanol, n-butanol and iso-butanol) and one ether (MTBE). All fuels were tested at two speed sweeps at low and mid load conditions, and a spark timing sweep at low load conditions. The oxygenated biofuels exhibit increased efficiencies, even at non-knock-limited conditions. At lower loads, the oxygenated fuels decrease CO, HC and NOx emissions. However, at mid load conditions, decreased volatility of the alcohols leads to increased emissions due to fuel impingement effects. Methanol exhibited the highest efficiencies and significantly increased burn rates compared to the other fuels. Gasoline exhibited the lowest level of PN and PM emissions. N-butanol and iso-butanol show significantly increased levels of particle emissions compared to the other fuels QC 20210917 Framtida alternativa transportbränslen

The transport sector is one of the main sources of greenhouse gas emissions.Replacing fossil fuels with renewable fuels can help reduce the impact oftransportation on the climate. Liquid, oxygenated biofuels show great potentialas a replacement in spark-ignited engines, as they exhibit similarcombustion behavior to gasoline, and are compatible with existing infrastructure.This thesis aims to expand the knowledge on how oxygenated fuelsaffect emissions and performance in direct-injected spark-ignited (DISI) engines.Experiments on a gasoline optimised DISI engine at low and mid loadconditions, were conducted to establish how these fuels affect engine efficiency,combustion propagation, and emissions. A thorough investigationon how the particle emissions change with different fuels was also performed.The research evaluated five different oxygenated fuels in comparison to gasoline:ethanol, methanol, n-butanol, iso-butanol, and methyl tert-butyl ether.The oxygenated fuels all increased engine efficiency, even at low loads wherethe engine was not knock limited. The most significant increase in efficiencywas observed for methanol, with up to 12% improvement in indicated thermalefficiency compared to gasoline. At low loads all oxygenated fuels decreasedthe emissions of unburned hydrocarbons, carbon monixde and nitrogenoxides. The results at mid load conditions show that fuels with lowvolatility will increase these emissions. The findings also indicate that fuelvolatility will have a more significant impact on the particle emissions levelsthan fuel oxygen content. This effect is more pronounced at lower enginespeeds and higher engine loads.This thesis work reveals great potential to use liquid, oxygenated biofuelsin DISI engines to decrease transport-associated carbon dioxide emissions.Even without engine modifications, oxygenated fuels yield improved engineefficiency compared to gasoline. Optimized injection for fuels with decreasedvolatility is needed to reduce emissions at higher engine loads. Transportsektorn är en stor bidragande faktor till utsläppen av växthusgaser. Därmed kan ersättningen av fossila bränslen med förnyelsebara bränslen bidra till att reducera transportsektorns inverkan på klimatet. Flytande oxygenerade biobränslen visar stor potential som ersättningsalternativ till bensin, eftersom de har liknande förbränningsegenskaper och är kompatibla med nuvarande infrastruktur. Målet med denna avhandling är att bidra till en ökad kunskap om hur oxygenerade bränslen påverkar emissioner och prestanda i direktinsprutade gnisttända (DISI) motorer. Experiment på en bensinoptimerad DISI motor utfördes för att fastställa hur dessa bränslen påverkar motorns verkningsgrad, flamutbredning, samt utsläppsnivåerna av emissioner. En grundlig undersökning av hur partikelemissionerna förändrades med olika bränslen genomfördes också. Fem olika oxygenarade bränslen undersöktes, och jämfördes med bensin: etanol, metanol, n-butanol, iso-butanol, och metyl tert-butyl eter. Alla de oxygenerade bränslena ökade motorns verkninsgrad, även vid lägre laster då motorn inte var begränsad av knack. Störst öking av verkningsgraden uppvisades då metanol användes som bränsle. Metanol ökade den indikerade termiska verkningsgraden med upp till 12% jämfört med bensin. Vid låga laster minskade emissionerna av oförbrända kolväten, kolmonoxid och kväveoxider vid användning av oxygenerade bränslen jämfört mot bensin. Medan vid medelhög last så ökade emissionerna för de bränslen som har låg flyktighet. De experimentella resultaten visar att bränslets flyktighet har högre inverkan på mängden partiklar som motorn släpper ut än bränslets syrehalt. Denna effekt är tydligare vid lägre varvtal och högre laster. Den här avhandlingen visar att användningen av flytande, oxygenerade bränslen i DISI motorer visar stor potential till att minska transportsektorns koldioxid utsläpp. De oxygenerade bränslena ökade motorns verkningsgrad i jämförelse med bensin, även optimering av motorn till dessa bränslen. Optimering av bränsleinsprutningen krävs för att minska emissionerna vid högre laster för bränslen med lägre flyktighet än bensin.

Knock is the most crucial limitation in attaining the peak load required at high efficiency in heavy duty (HD) spark ignition (SI) engines. Renewable fuels such as ethanol and methanol have high resistance to autoignition and can help overcome this limitation. To reduce knock and improve efficiency further, dilution can be used to add specific heat capacity and reduce combustion temperature. This work studied diluted combustion and knock characteristics of gasoline, ethanol, and methanol on a HD SI single cylinder engine for a wide load range. Ethanol and methanol displayed excellent knock resistance which allowed a peak gross IMEP of 25.1 and 26.8 bar respectively, compared to gasoline which only reached 8.3 bar at λ=1.4 with a compression ratio of 13. Over 18% increase in gross IMEP was possible for gasoline and ethanol when increasing air excess ratio from 1 to 1.4. Methanol achieved the target gross IMEP at λ=1 and required no spark retard at =1.6. A peak indicated efficiency above 48% was recorded for ethanol and methanol at =1.6 and gross IMEP of approximately 21 bar. At part loads, stable operation was possible until =1.8 for all fuels. Increase in intake temperature showed a marginal improvement in stability but no increase in lean limit. The concept shows promise as diluted combustion of ethanol and methanol reduced knock and achieved diesel baseline load. With optimization, there is potential to improve efficiency further and possible cost savings compared to commercial diesel engines.