The aviation industry represents approximately 3% of global greenhouse gas emissions, however with significant growth expected over the coming decades this proportion is expected to increase. Continued governmental and social pressure to reduce global emissions is posing a challenging question to the industry; how to improve environmental efficiency and reduce emissions with increasing industry growth. The environmental impact of aviation globally is discussed, examining the significant emissions and protocols that exist and their relative impacts both environmentally and economically. The viability of alternative biofuels is discussed, determining the life cycle environmental impact of future replacements to kerosene based jet fuel. This thesis therefore aims to provide an understanding of the fundamentals of aviation emissions but also most importantly provide possible solutions to assist the industry in reducing its emissions ‘footprint’. An important factor in determining efficiency improvements is to understand the impact of particular stages of an aircraft life and the impact they have individually. This was achieved using an established methodology called Life Cycle Assessment (LCA), which is an efficient tool for the analytical consideration of the environmental impact of manufacturing, operation and decommissioning. The results of a comprehensive LCA study of an Airbus A320 are documented considering all phases of the service life. The study draws useful conclusions, indicating the significance of special materials such as carbon fibre reinforced plastic (CFRP) on the total manufacturing emissions of the aircraft and indicating its operational phase as the one contributing most in its environmental performance breakdown. The thesis also examines short-term efficiencies for emissions reduction in commercial aviation, focussing on improvements in aircraft routing. The initiation of the EU emissions trading system (ETS) within European aviation willincentivise airlines to reduce their annual CO2 emissions. An alternative routing strategy is proposed for selected long haul routes, which introduces multiple stages into the route utilising two aircraft and is shown to reduce total CO2 emissions by up to 13.7%. Combined with blended biofuel, this reduction was estimated to increase to 16.6% with a reduction in ticket fares estimated to be as high as $19 per passenger per flight.

This master’s thesis discusses the impact of air traffic on our environment. The fuels combustion, the conditions necessary for realization of air traffic, or the situations resulting from it, such as aircraft maintenance, noise, emergencies, etc., have a negative impact on not only on the environment, but also on health and comfort of people, as well as flora and fauna, exposed to these conditions. Apart from the air traffic impacts on our environment mentioned above, the thesis also describes especially the possibilities of their reduction and companies dealing with them. The large main part of thesis paper is dedicated to an analysis of a new aircraft design technology, which should reduce the production of emissions in the future.

This project evaluates the opportunity to convert a three-cylinder automobile piston engine (the Tiny Friendly Giant) to an aircraft engine from an environmental and practical point of view. The problem of increased emissions from aviation calls for technical and socioeconomic solutions, which is the reason why this report is written. The main goals are to choose the best fuel for the piston engine in aviation, as well as to study emissions, engine cooling and practical challenges with conversion. The structure resembles a feasibility study where the problem is solved using literature in a trade study, together with emission estimations using The Greenhouse gases, Regulated Emissions, and Energy use in Technologies Model framework and Boeing Fuel Flow Method 2. An estimation for engine cooling is done using a semiemprical method from Lycoming, showing air cooling can be sufficient for the Tiny Friendly Giant in aviation. The results furthermore show that none of the alternative automobile fuels are appropriate for use in aviation and that alternative pathways to jet fuel are more suited for high altitude. The conclusion is thus that the engine should be converted to jet fuel compatibility. To avoid large turning moment fluctuations, two-stroke can be applied. Conversion and use of the engine in aviation is not considered to be feasible because of practical limitations - instead the study concludes designing a new engine from scratch is easier and most likely quicker. The study shows that reducing carbon dioxide emissions also lead to reductions in water and sulfur- and nitrous oxides. However, the same mitigation strategy leads to increase in carbon monoxide and hydrocarbons. In general, the conclusion is that alternative fuels can significantly reduce aircraft emissions. / Detta examensarbete utvärderar möjligheten att konvertera en trecylindrig bilkolvmotor (Tiny Friendly Giant motorn) till en flygplansmotor från en miljömässig och praktisk synvinkel. Problemet med ökade utsläpp från flyget kräver tekniska och socioekonomiska lösningar, vilket är anledningen till att detta arbete är genomfört. De största målen går ut på välja det bästa bränslet för kolvmotorn inom flyget, samt att studera utsläpp, motorkylning och praktiska utmaningar med konvertering. Strukturen liknar en förstudie där problemet löses med hjälp av litteratur i en paramterstudie, tillsammans med utsläppsuppskattningar med hjälp av The Greenhouse gases, Regulated Emissions, and Energy use in Technologies Model ramverket och Boeing Fuel Flow Method 2. En uppskattning för motorkylning är beräknat med en semiemprisk metod från Lycoming, som visar att luftkylning vara tillräckligt för Tiny Friendly Giant motorn inom flyg. Resultaten visar vidare att inget av de alternativa bilbränslena är lämpliga för användning inom flyget och att alternativa vägar till flygbränsle är mer lämpat för hög höjd. Slutsatsen är att motorn bör konverteras till flygbränslekompatibilitet. För att undvika stora vridmomentfluktuationer kan tvåtakt användas. Konvertering och användning av motorn inom flyget anses inte vara genomförbart på grund av praktiska begränsningar - istället drar studien slutsatsen att design av en ny motor från grunden är enklare och med största sannolikhet snabbare. Studien visar att minskade koldioxidutsläpp också leder till minskningar av vatten och svavel- och dikväveoxider. Samma strategi leder dock till en ökning av kolmonoxid och kolväten. Generellt sett är slutsatsen att alternativa bränslen avsevärt kan minska flygplanens utsläpp.

<p dir="ltr">Soot is a byproduct formed during incomplete combustion of hydrocarbon fuels. Atmospheric soot from aircraft emissions increases local air temperatures, drives cloud formation, and decreases albedo on snow and ice: three factors that promote global warming. It is also potentially harmful to humans and has been associated with negative effects on heart and lung health. Operationally, soot formation indicates an inefficiency in combustion and can cause deterioration in aircraft engines. Modeling soot formation in complex flow fields is difficult and has been largely unsuccessful. In-situ soot measurements at relevant conditions can inform the design and operation of aircraft engines with reduced soot emissions. Laser-induced incandescence (LII) is a diagnostic that allows for non-intrusive measurements of soot volume fraction and primarily particle size in combustion environments. It involves laser-heating soot particles to temperatures at which they incandescence and measuring the radiated signal. The strong absorption capabilities and high sublimation temperature of soot make this diagnostic highly selective against the detection of other species. A coupled set of differential equations can be used to model the change in temperature and mass of a soot particle over time. Methods for modeling the fundamental processes in LII were reviewed in this work and comparisons were made between several different models.</p><p dir="ltr">International Sooting Flame target conditions were used to form a laminar diffusion flame in a Yale burner with a range of soot levels. Soot volume fraction measurements were conducted and compared with other experimental values to validate the accuracy of the experimental setup and techniques used. A calibration was performed using a laser extinction measurement from a previous study. Results showed an overall increase in soot volume fraction with increasing percentages of ethylene, as well as a transition in the peak location. Time-resolved LII was conducted at 10 MHz to determine the primary particle size of soot particles. Larger primary particles were observed with increasing height for flames with higher ethylene content. Changes in the soot formation and surface growth rates are suspected factors in the observed trends in the data. </p><p dir="ltr">The overall objective of this study was to validate an experimental setup for Laser-Induced Incandescence using a laminar diffusion flame. LII measurements were successfully demonstrated using the same diagnostic setup in a liquid-fueled swirl-stabilized flame at aircraft engine-relevant conditions. This study sets the groundwork for further investigation into aircraft soot generation using LII. </p>