In this paper we summarize the main points of beta regression models under Bayesian perspective, including a presentation of the Bayesianbetareg R-package, used to fit the beta regression models under a Bayesian approach. Finally, beta regression models are fitted to a reading score database using, respectively, the Bayesianbetareg and betareg R-Packages for Bayesian and classic perspectives.

New experimental results for lean flammability limits (LFLs) of syngas/air (H2/CO/air) mixtures have been obtained at temperatures up to 200 °C and pressures up to 9 bar. ASTM Standard E918 (1983) provided the framework for tests at these elevated conditions, using a 1-L pressure-rated test cylinder in which the fuel–air mixtures were prepared and then ignited. The purpose for characterizing the flammability limits for these gaseous mixtures is to facilitate development of appropriate procedures for the safe industrial use of syngas, which contains large quantities of hydrogen and carbon monoxide gas. The LFLs for each gas mixture are found to decrease linearly with increasing temperature at all test pressures. The LFL results at atmospheric pressure are consistent with previous flammability studies, while those at elevated pressures represent new flammability data. An increase in the initial test pressure results in an increase of the LFLs for each test mixture, which also serves to address the lack of syngas/air flammability data at elevated pressures. An empirical formula is derived that allows for the calculation of the LFLs of all syngas/air test mixtures in the temperature and pressure range of the current study in an effort to promote the ease of use in practical applications. Predicted LFL values obtained using Le Chatelier’s mixing rule and an appropriate choice for the lower flammability limit of pure carbon monoxide are consistent with the experimentally determined values near ambient conditions of temperature and pressure.

Elevated pressure and temperature conditions are widely encountered during gas turbine operation. To avoid unexpected ignition and explosion of mixtures of fuel and air under these conditions, it is imperative to identify the flammability limits of relevant fuel mixtures. Common fuels include process gases such as natural gas, coke oven gas and IGCC syngas fuel. The flammability limits of pure fuels and common gas/air mixtures have been widely reported, however a significant lack of flammability data for fuel mixtures relevant for use in gas turbines as well as data at elevated pressure and temperature conditions is available. The objective of this study is to characterize the flammability limits of fuel/air mixtures and their dependence on initial temperature and pressure. Experimental studies of lean flammability limits (LFLs) for methane, hydrogen, and carbon monoxide, in addition to mixtures of these gases (i.e. CH4/H2, H2/CO, and CH4/CO2) were performed at temperatures up to 200 °C and pressures up to 9 bar. ASTM Standard E918 (1983) provided the framework for tests using a one-liter pressure-rated test cylinder in which the fuel-air mixtures were prepared and then ignited. Flammability is determined using a 7% and 5% pressure rise criterion per the ASTM E918 and European EN 1839 standards, respectively. The LFLs for each gas and gas mixture are found to decrease linearly with increasing temperature for the temperature range tested. The LFLs of hydrogen and mixtures containing hydrogen are observed to increase with an increase in the initial pressure, whereas the LFLs of all other mixtures exhibit a negligible dependence on pressure. For mixtures, predicted LFL values obtained using Le Chatelier’s mixing rule (LC) are fairly consistent with the experimentally determined values near ambient conditions, however it is not recommended for use at elevated pressure and/or temperature. Finally, the experimental data presented in this study are compared with previous experimental studies, flammability limits calculated using numerical methods, and past studies of predicted LFL values for similar fuel/air mixtures. The purpose for characterizing the flammability limits for these gaseous mixtures is to extend the results to developing appropriate procedures for the safe industrial use of renewable gases, such as bio-derived methane, biogas composed mainly of methane and carbon dioxide, and renewably derived syngas which contains large quantities of hydrogen and carbon monoxide gas.

No abstract