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Balagurunathan, JayakishanInvestigation of Ignition Delay Times of Conventional (JP-8) and Synthetic (S-8) Jet Fuels: A Shock Tube Study
Master of Science (M.S.), University of Dayton, 2012, Mechanical Engineering
The global depletion of petroleum-based fuels has led the world to more closely examine alternate fuels. Therefore, alternate fuels produced from feedstocks such as coal, soybeans, palm oil or switch grass through methods such as coal liquefaction, biomass gasification, and Fischer-Tropsch synthesis have been tested. Among these techniques, fuels generated using Fischer-Tropsch technologies are of interest because they produce clean burning hydrocarbons similar to those found in commercial fuels. Therefore, in this study the Fischer-Tropsch derived S-8 fuel was evaluated as a drop-in replacement for the jet fuel JP-8. The jet fuel JP-8 is comprised of n-, iso- and cyclo- alkanes as well as aromatics while the S-8 fuel is primarily comprised of n- and iso- alkanes. The composition of the fuel affects its ignition characteristics chemically and physically by either advancement or delay of time to ignition. Since this study focused on the chemical effects, the fuels were completely pre-vaporized and pre-mixed. A high pressure, high temperature heated single pulse shock tube was used for this study. The shock tube is an established experimental tool used to obtain ignition delay data behind reflected shock waves under operating conditions relevant to modern engines. The experiments were conducted over a temperature range of 1000-1600 K, a pressure of 19±2 atm, equivalence ratios of 0.5, 1 and 3, within a dwell time of 7.6±0.2 ms and an argon dilution of 93% (v/v). Ignition delay times were measured using the signal from the pressure transducer on the end plate with guidance from the optical diagnostic signal. Along with JP-8 and S-8, the ignition delay of n-heptane was also studied. N-heptane was chosen to represent the n-alkanes in the fuels for this study since it was present in both fuels and also to prove the fact that the n-alkanes were rate controlling. The results indicate that both S-8 and JP-8 fuels have similar ignition delays at corresponding equivalence ratios. The fuel-rich mixtures ignited faster at lower temperatures (<1150 K) and the fuel-lean mixtures ignited faster at higher temperatures (>1150 K). In the transition period between lower to higher temperatures (~1100-1200 K), the equivalence ratio had no significant effect on the ignition delay time. The results also show that the ignition delay time measurements of S-8 and JP-8 fuels are similar to the ignition delay of n-heptane at the equivalence ratio of Φ=0.5 and thereby indicate that the n-alkanes present in these fuels controlled the ignition under these conditions. The ignition delay results of S-8 and JP-8 at Φ=3.0 from this study were also compared to prior work (Kahandawala et al., 2008) on 2-methylheptane and n-heptane/toluene (80/20 liquid vol.%), respectively and found to be indistinguishable. This data serves to extend the gas phase ignition delay database for both JP-8 and S-8 and is the first known data taken for both these fuels at higher temperatures (>1000 K) for an equivalence ratio of 3.0 with argon as the diluent gas.

Committee:

Sukh Sidhu, Dr (Committee Chair); Philip Taylor, Dr (Committee Member); Moshan Kahandawala, Dr (Committee Member)

Subjects:

Aerospace Engineering; Aerospace Materials; Alternative Energy; Automotive Engineering; Automotive Materials; Chemical Engineering; Chemistry; Energy; Engineering; Environmental Engineering; Mechanical Engineering; Petroleum Engineering; Technology

Keywords:

Ignition delay; shock tube; S-8; JP-8; Jet fuels; Fuel characteristics; heated shock tube; Fischer-Tropsch; Alternate fuels; alkanes; synthetic fuel; fuel; iso-alkanes; jayakishan balagurunathan

Somuri, Dinesh ChandraStudy of Particulate Number Concentrations in Buses running with Bio diesel and Ultra Low Sulfur diesel
Master of Science, University of Toledo, 2011, Civil Engineering
Most of the air quality standards available today are mass based and confined to PM2.5 and PM10 fractions. Size of most particles released from combustion sources is of submicron range, which has minor contribution to mass concentration. Therefore it is essential to obtain inventories for particulate number concentrations in this range. The study was mainly focused on in-vehicle particulate number concentrations in public transport buses running on alternative fuels in the city of Toledo. The in-vehicle particulate number concentrations were collected over a period of one year from July 2008 to June 2009, in Biodiesel and Ultra low sulfur diesel fueled buses. The size of particulates found was in the range of 0.3µm and 20µm. Using the above measured particulate concentration data, the diurnal, monthly, and seasonal variations were studied. Various factors effecting in-vehicle particulate concentrations like number of passengers in the bus, vehicles moving near the bus, ambient temperature, relative humidity, wind speed, wind direction, precipitation were also analyzed using regression tree analysis. It was found that 65-70 % of particulates observed were in the size range of 0.3-0.4 µm. From this we were able to conclude that particulates emitted from diesel vehicles mostly consisted of fine particles. It was observed that particulate concentrations in biodiesel bus were slightly more when compared to ultra low sulfur diesel bus concentrations. From diurnal graphs, it was found that maximum particulate concentrations were obtained during the early mornings, when bus starts its run. From monthly and seasonal trends, it was obtained that maximum concentrations were found during the winter season, because of limited air exchange rate within the bus compartment. From the above trends it was clearly understood that in-vehicle particulate number concentrations were mainly influenced by peak hours, vehicular traffic, positioning of doors and windows, and passengers travelling. Regression analysis showed that in-vehicle particulate concentrations were influenced by meteorology. Wind speed and wind direction were found to have a significant impact on particulate concentrations. Various combinations of variables explained the pattern of monitored concentrations. The measured in-vehicle particulate number concentrations in B20 and ULSD buses were converted in to mass concentrations of PM1.0, PM2.5 and PM10. These PM mass concentrations were compared with previously measured two years PM concentrations in the same buses. Using all the above data annual and seasonal PM trends were studied. It was observed that PM mass concentrations increased in the year 2009 compared to 2008 concentration levels. In all the three years, particulate matter concentrations were found to be more in winter season when compared to other seasons in both BD and ULSD buses. A screening mass balance model was developed for modeling of in-vehicle PM2.5 concentrations for buses. The model was tested over four different seasons during a one year period. The air exchange rate and, deposition loss rate were estimated from literature review and from the analysis of monitored concentrations when developing the mass balance model. The developed model predicts the in-vehicle PM2.5 levels inside buses for four seasons performed well up to 1:00 PM. It is suggested that a forecasting model should be used for ambient concentrations to improve the accuracy during afternoon hours.

Committee:

Ashok Kumar, PhD (Committee Chair); Andrew Heydinger, PhD (Committee Member); Vijay Devabhaktuni, PhD (Committee Member)

Subjects:

Civil Engineering

Keywords:

Particulate Number concentrations; Alternate fuels; PM 2.5; In-vehicle air quality; Modeling