Development of biomass cookstoves that reduce emissions of CO and PM2.5 by more than 50% and 95%, respectively, compared to a three-stone fire has been promoted as part of efforts to reduce exposure to household air pollution (HAP) among people that cook with solid fuels. Gasifier cookstoves have attracted interest because some have been shown to emit less CO and PM2.5 than other designs. A laboratory test bed and new test procedure were used to investigate the influence of air flow rates, stove geometry, fuel type, and operating mode on gasifier cookstove performance. Power output, CO emissions, PM2.5 emissions, fuel consumption rates, producer gas composition, and fuel bed temperatures were measured. The test bed emitted <41 mg·MJd–1 PM2.5 and <8 g·MJd–1 CO when operating normally with certain prepared fuels, but order of magnitude increases in emission factors were observed for other fuels and during refueling. Changes in operating mode and fuel type also affected the composition of the producer gas entering the secondary combustion zone. Overall, the results suggest that the effects of fuel type and operator behavior on emissions need to be considered, in addition to cookstove design, as part of efforts to reduce exposure to HAP.
In this study, the autoignition behavior
of primary reference fuels
(PRF) and blends of n-heptane/n-butanol
were examined in a Waukesha Fuel Ignition Tester (FIT) and a Homogeneous
Charge Compression Engine (HCCI). Fourteen different blends of iso-octane, n-heptane, and n-butanol were tested in
the FIT28 test runs with 25 ignition measurements for each
test run, totaling 350 individual tests in all. These experimental
results supported previous findings that fuel blends with high alcohol
content can exhibit very different ignition delay periods than similarly
blended reference fuels. The experiments further showed that n-butanol blends behaved unlike PRF blends when comparing
the autoignition behavior as a function of the percentage of low reactivity
component. The HCCI and FIT experimental results favorably compared
against single and multizone models with detailed chemical kinetic
mechanismsboth an existing mechanism as well as one developed
during this study were used. The experimental and modeling results
suggest that that the FIT instrument is a valuable tool for analysis
of high pressure, low temperature chemistry, and autoignition for
future fuels in advanced combustion engines. Additionally, in both
the FIT and engine experiments the fraction of low temperature heat
release (fLTHR) was found to correlate very well with the crank angle
of maximum heat release and shows promise as a useful metric for fuel
reactivity in advanced combustion applications.
This study is concerned with the identification and quantification of species generated during the combustion of cyclopentane in a jet stirred reactor (JSR). Experiments were carried out for temperatures between 740 and 1250 K, equivalence ratios from 0.5 to 3.0, and at an operating pressure of 10 atm. The fuel concentration was kept at 0.1% and the residence time of the fuel/O 2 /N 2 mixture was maintained at 0.7 s. The reactant, product, and intermediate species concentration profiles were measured using gas chromatography and Fourier transform infrared spectroscopy. The concentration profiles of cyclopentane indicate inhibition of reactivity between 850-1000 K for φ=2.0 and φ=3.0. This behavior is interesting, as it has not been observed previously for other fuel molecules, cyclic or non-cyclic. A kinetic model including both low-and high-temperature reaction pathways was developed and used to simulate the JSR experiments. The pressure-dependent rate coefficients of all relevant reactions lying on the PES of cyclopentyl + O 2 , as well as the CC and C-H scission reactions of the cyclopentyl radical were calculated at the UCCSD(T)-F12b/cc-pVTZ-F12//M06-2X/6-311++G(d,p) level of theory. The simulations reproduced the unique reactivity trend of cyclopentane and the measured concentration profiles of intermediate and product species. Sensitivity and reaction path analyses indicate that this reactivity trend may be attributed to differences in the reactivity of allyl radical at different conditions, and it is highly sensitive to the C-C/C-H scission branching ratio of the cyclopentyl radical decomposition.
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