Autoignition of fuels

An autoignition test section and a premixing fuel injector developed to determine the autoignition characteristics of a variety of aircraft fuels are described. Parametric tests to map the ignition delay characteristics of Jet-A fuel were conducted at pressures of 10, 15, 20, 25, and 30 atm, inlet air temperatures up to 900K and fuel-air equivalence ratios of 0.3, 0.5, 0.7, and 1.0. Residence times in the range of 1 to 50 msec were obtained by interchanging spool pieces to create six different mixer/vaporizer lengths (6, 23, 53, 84, 99, and 130 cm) and by testing at two different airflow rates (0.5 and 1.0 kg/sec). The resulting free-stream velocities were in the range 20 to 100 m/sec. As expected, the results indicate that the ignition delay times decrease with increasing air temperature and pressure. Also, the data show that, for lean mixtures, ignition delay times decrease with increasing equivalence ratios

Towards 2000: A Tougher Future for Australian Business?

The paper reports on the future business environment expected by top level Australian executives. It forecasts environmental changes to the year 2000 and updates projections reported in an earlier study. Specifically, top managers from 171 of Australia\u27s largest 500 corporations provide their views concerning world ecology, the economy, technology and political-social developments. Their perceptions are then linked to specific competitive strategies that are evoked by the long-range forecast which they expect

Autoignition characteristics of no. 2 diesel fuel

Parametric tests to map the ignition delay characteristics were conducted at pressures of 3, 4, and 5 atm, inlet air temperatures up to 1150 K and fuel air equivalence ratios ranging from 0.2 to 1.0. Ignition delay times in the range of 6 msec to 60 msec at freestream flow velocities ranging from 10 m/sec to 40 m/sec were obtained. The ignition delay times appeared to correlate with the inverse of pressure and the inverse exponent of temperature

Autoignition characteristics of aircraft-type fuels

The ignition delay characteristics of Jet A, JP 4, no. 2 diesel, cetane and an experimental referee broad specification (ERBS) fuel in air at inlet temperatures up to 1000 K, pressures of 10, 15, 20, 25 and 30 atm, and fuel air equivalence ratios of 0.3, 0.5, 0.7 and 1.0 were mapped. Ignition delay times in the range of 1 to 50 msec at freestream flow velocities ranging from 20 to 100 m/sec were obtained using a continuous flow test apparatus which permitted independent variation and evaluation of the effect of temperature, pressure, flow rate, and fuel/air ratio. The ignition delay times for all fuels tested appeared to correlate with the inverse of pressure and the inverse exponent of temperature. With the exception of pure cetane, which had the shortest ignition delay times, the differences between the fuels tested did not appear to be significant. The apparent global activation energies for the typical gas turbine fuels ranged from 38 to 40 kcal/mole, while the activation energy determined for cetane was 50 kcal/mole. In addition, the data indicate that for lean mixtures, ignition delay times decrease with increasing equivalence ratio. It was also noted that physical (apparatus dependent) phenomena, such as mixing (i.e., length and number of injection sites) and airstream cooling (due to fuel heating, vaporization and convective heat loss) can have an important effect on the ignition delay

Markov bases and linear algebra: connecting fibres of integer linear maps

La tesi esplora metodi per costruire strutture di grafi connessi partendo da fibre, ossia insiemi di vettori naturali che condividono la stessa immagine sotto applicazione lineare. A tale scopo, verranno introdotti metodi per migliorare sensibilmente le stime superiori già note per la norma di un dato insieme di mosse, nel senso definito da D. Holmes in "The norm of the saturation of a binomial ideal, and applications to Markov bases

Deposit formation in hydrocarbon rocket fuels

An experimental program was conducted to study deposit formation in hydrocarbon fuels under flow conditions that exist in high-pressure, rocket engine cooling systems. A high pressure fuel coking test apparatus was designed and developed and was used to evaluate thermal decomposition (coking) limits and carbon deposition rates in heated copper tubes for two hydrocarbon rocket fuels, RP-1 and commercial-grade propane. Tests were also conducted using JP-7 and chemically-pure propane as being representative of more refined cuts of the baseline fuels. A parametric evaluation of fuel thermal stability was performed at pressures of 136 atm to 340 atm, bulk fuel velocities in the range 6 to 30 m/sec, and tube wall temperatures in the range 422 to 811 K. Results indicated that substantial deposit formation occurs with RP-1 fuel at wall temperatures between 600 and 800 K, with peak deposit formation occurring near 700 K. No improvements were obtained when deoxygenated JP-7 fuel was substituted for RP-1. The carbon deposition rates for the propane fuels were generally higher than those obtained for either of the kerosene fuels at any given wall temperature. There appeared to be little difference between commercial-grade and chemically-pure propane with regard to type and quantity of deposit. Results of tests conducted with RP-1 indicated that the rate of deposit formation increased slightly with pressure over the range 136 atm to 340 atm. Finally, lating the inside wall of the tubes with nickel was found to significantly reduce carbon deposition rates for RP-1 fuel

Deposit formation in hydrocarbon rocket fuels: Executive summary

An experimental program was conducted to study deposit formation in hydrocarbon fuels under flow conditions that exist in high-pressure, rocket engine cooling systems. A high pressure fuel coking test apparatus was designed and developed and was used to evaluate thermal decomposition (coking) limits and carbon deposition rates in heated copper tubes for two hydrocarbon rocket fuels, RP-1 and commercial-grade propane. Tests were also conducted using JP-7 and chemically-pure propane as being representative of more refined cuts of the baseline fuels. A parametric evaluation of fuel thermal stability was performed at pressures of 136 atm to 340 atm, bulk fuel velocities in the range 6 to 30 m/sec, and tube wall temperatures in the range 422 to 811K. In addition, the effect of the inside wall material on deposit formation was evaluated in selected tests which were conducted using nickel-plated tubes. The results of the tests indicated that substantial deposit formation occurs with RP-1 fuel at wall temperatures between 600 and 800K, with peak deposit formation occurring near 700K. No improvements were obtained when de-oxygenated JP-7 fuel was substituted for RP-1. The carbon deposition rates for the propane fuels were generally higher than those obtained for either of the kerosene fuels at any given wall temperature. There appeared to be little difference between commercial-grade and chemically-pure propane with regard to type and quantity of deposit. The results of tests conducted with RP-1 indicated that the rate of deposit formation increased slightly with pressure over the range 136 atm to 340 atm. Finally, plating the inside wall of the tubes with nickel was found to significantly reduce carbon deposition rates for RP-1 fuel

Deposit formation and heat transfer in hydrocarbon rocket fuels

An experimental research program was undertaken to investigate the thermal stability and heat transfer characteristics of several hydrocarbon fuels under conditions that simulate high-pressure, rocket engine cooling systems. The rates of carbon deposition in heated copper and nickel-plated copper tubes were determined for RP-1, propane, and natural gas using a continuous flow test apparatus which permitted independent variation and evaluation of the effect on deposit formation of wall temperature, fuel pressure, and fuel velocity. In addition, the effects of fuel additives and contaminants, cryogenic fuel temperatures, and extended duration testing with intermittent operation were examined. Parametric tests to map the thermal stability characteristics of RP-1, commercial-grade propane, and natural gas were conducted at pressures of 6.9 to 13.8 MPa, bulk fuel velocities of 30 to 90 m/s, and tube wall temperatures in the range of 230 to 810 K. Also, tests were run in which propane and natural gas fuels were chilled to 230 and 160 K, respectively. Corrosion of the copper tube surface was detected for all fuels tested. Plating the inside of the copper tubes with nickel reduced deposit formation and eliminated tube corrosion in most cases. The lowest rates of carbon deposition were obtained for natural gas, and the highest rates were obtained for propane. For all fuels tested, the forced-convection heat transfer film coefficients were satisfactorily correlated using a Nusselt-Reynolds-Prandtl number equation

The First Sign: Detecting Future Financial Fraud from the IPO Prospectus

In this study, I examine whether it is possible to predict future financial statement fraud using disclosure content prior to the fraud. Specifically, I employ a machine learning algorithm to construct a unique measure based on the lexical cues embedded within a firm’s first public disclosure, the Management’s Discussion and Analysis section of the S-1 filing, during the Initial Public Offering process. I use this measure to predict whether a firm that is not already committing fraud will commit fraud within five years of the Initial Public Offering (IPO) that results in an Accounting or Enforcement Release (AAER). I find there is information within the S-1 filing that is useful in the prediction of out-of-sample fraud. Additionally, I find that the measure performs better than both benchmark measures from prior literature and a new measure using quantitative information, when using information available at the S-1 date. Furthermore, the lexical cues measure performs well in predicting fraud relative to the benchmark measures even after updating the benchmark measures with misstated annual filings to aid their (but not my measure’s) fraud detection abilities. I find that my new measure is not limited to only predicting AAER based misconduct, but that the out-of-sample results hold when using an alternate sample based on 10(b)-5 filings as well as a comprehensive set of quantitative variables. Lastly, my measure identifies firms more likely to manage earnings to meet/beat analyst forecasts, firms who experience higher levels of information asymmetry around earnings announcements within the five years following the IPO, and has some predictive ability over future abnormal returns

An Analysis Of Factors That Influenced Brevard Students To Drop Out And Why They Returned To Earn Their General Education Development (ged) Diploma

Dropping out of high school almost guarantees a life of hardship. The absence of a diploma contributes to poverty, increased crime rates and weakens the economy. To that end, school districts have a moral and ethical responsibility to bring an end to the dropout epidemic. This study was based on an analysis of more than 26,000 Brevard public school students. The researcher used 2006-2007, 2007-2008 and 2008-2009 student data to determine the relationship between race, grade level, ESE status, ELL status, SES, type of promotion and dropping out of school. In addition, the researcher reviewed Student Exit Survey data and face-to-face interview data to determine why students dropped out and identified strategies students felt would have kept them in school. Finally, individual interview data were analyzed to understand the circumstances that encouraged participants to return to earn their diplomas. The researcher recommended use of data management and tracking systems for early identification of potential dropouts so intervention could be delivered at the onset of failure, assignment of trained adult leaders to monitor and intervene for students; enforcement of compulsory school attendance; creation of mechanisms to reduce absenteeism that do not lead to school failure; required intervention for students who are truant; identification and assignment of highly effective teachers to at-risk youth; intervention in classrooms that have high rates of student failure; use of relevant curriculum and employment of instructional practices proven to increase engagement; alignment of intervention strategies with researched practices; gathering of input and feedback from students to determine program effectiveness; iv creation of meaningful exit interview processes; utilization of survey data to identify and remove school-related barriers and collaboration with community agencies to find meaningful and genuine solutions for students in crisis