Sök:

Vätedriven förbränningsmotor

Klarläggande av framtida hållbarhet

Today when new and harder demands on CO2 emissions are developed, vehicle manufacturers must work to develop new engine solutions to new kinds of fuels to replace fossil fuels. A fuel that could be applied is hydrogen. When hydrogen is combusted only water vapor occurs. Hydrogen is known to be explosive and flammable. These properties are both good and bad for combustion. The purpose of this study is to present the problems and solutions that concern hydrogen as a fuel both inside and outside the combustion engine.The most common method of production is steam reforming of natural gas but produces high CO2 emissions. There are eco-friendly methods using only water as a raw material, but at the present they are expensive and need to be developed.The biggest problem during combustion is abnormal combustion. The reason is that hydrogen is sensitive to knock, have high flame velocity, low required autoignition energy and wide range of flammability. To avoid abnormal combustion and NOx, engines can be run with a lean fuel injection strategy. This helps but the result is lower power and torque output than the stoichiometric combustion.Otto engine, both with port injection and direct injection, and diesel engine can run on hydrogen. It turned out that direct injected otto engine gives the best efficiency, power output and lowest NOx emissions. However, this requires high temperatures and pressures that may contribute to short life length of components. Today's applications are therefore using port injection. The diesel engine could have even better efficiency, but because of high risk of abnormal combustion the engine only runs at low engine loads. Modifications of the engines must be done, in particular new materials are needed because hydrogen embrittles steel.Hydrogen is stored either as a liquid or as a compressed gas. Liquid hydrogen stores more energy on board by volume relatively compressed hydrogen, but must be cooled to -253° C. When the vehicle is not active hydrogen gas is formed and leaks out. In order to build a safe vehicle sensors are required to detect leaks.The conclusion is that hydrogen is applicable as a fuel, but hydrogen alone would not solve the fuel problems. Today the production capacity of hydrogen is too low, more eco-friendly production methods must be developed and new infrastructure to transport and refuel hydrogen must be implemented. This could result in high costs for the society.

Författare

Alexander Lönnergård

Lärosäte och institution

KTH/Skolan för teknikvetenskap (SCI)

Nivå:

"Kandidatuppsats". Självständigt arbete (examensarbete ) om minst 15 högskolepoäng utfört för att erhålla kandidatexamen.

Läs mer..