Fuel modification, and sensing to improve cold-start and transient performance
This dissertation describes the continuous development of Active Vapor Utilization System (AVUS) that collects fuel tank vapors for use as a cold-starting fuel. The AVUS system create from normally occurring fuel tank vapors a highly volatile fuel that improves combustion stability and decrease emissions during the starting and warm-up periods. Five specific topics are considered: the first briefly gives a background of the research, the second is to determine the feasibility of the AVUS concept with respect to generating a suitable cold starting fuel from normally occurring tank vapors, the third describes a new technology concept that was proven to be capable of determining a distillation profile of a motor fuel , the fourth is the AVUS's performance with butanol/gasoline blends based fuels, and lastly a flash calculation of a mixture of hydrocarbon is performed using Peng Robinson equation of state and the Rachford-Rice equation. To determine the feasibility of the AVUS concept, the system was run using a commercial gasoline. The condensate produced from the AVUS was then tested and analyzed using ASTM distillation analyzer. The AVUS condensates were found to be extremely more volatile than the parent fuels from which they were derived. Volatility by definition is a measurement of how easily the fuel vaporizes. Knowledge of variation in volatility is essential for eliminating the hydrocarbon emissions. Thus a new sensor concept for in-situ fuel volatility was used to improve the Usability of Liquid Motor Fuel. The technology of this new sensor is based on the principle that at a given temperature, higher volatility can dissipate more energy during nucleate boiling heat transfer than lower volatility fuel. Conversely, lower volatility fuels dissipate more energy during film boiling at a given temperature. To check the performance of the AVUS system with alcohol fuel, the AVUS system was run using butanol blended in amount of 20, 40, 60 and 80 % by volume with gasoline for the subject evaluation. The AVUS condensates generated from the butanol blends, however, exhibited much higher volatility, exceeding that of the straight gasoline. The measured T10 values for the condensates cB20-cB80 were 34 oC - 44 oC. Notably; T50 for the B60 condensate was comparable to that of gasoline. A flash calculation of a mixture of hydrocarbon using the Rachford-Rice equation with the capability of predicting liquid fuel composition has been established throughout in this study. The algorithm has proven to be very effective and relatively precise.