THE DESIGN AND ANALYSIS OF EXPERIMENTS. By Oscar Kempthorne. New York, John Wiley and Sons, Inc., 1952. 631 pp. $8.50. This book by a teacher of statistics (as well as a consultant for \"experimenters\") is a comprehensive study of the philosophical background for the statistical design of experiment. It is necessary to have some facility with algebraic notation and manipulation to be able to use the volume intelligently. The problems are presented from the theoretical point of view, without such practical examples as would be helpful for those not acquainted with mathematics. The mathematical justification for the techniques is given. As a somewhat advanced treatment of the design and analysis of experiments, this volume will be interesting and helpful for many who approach statistics theoretically as well as practically. With emphasis on the \"why,\" and with description given broadly, the author relates the subject matter to the general theory of statistics and to the general problem of experimental inference. MARGARET J. ROBERTSON

The Design and Analysis of Experiments

Over the last two decades, our understanding of soot formation has evolved from an empirical, phenomenological description to an age of quantitative modeling for at least small fuel compounds. In this paper, we review the current state of knowledge of the fundamental sooting processes, including the chemistry of soot precursors, particle nucleation and mass/size growth. The discussion shows that though much progress has been made, critical gaps remain in many areas of our knowledge. We propose the roles of certain aromatic radicals resulting from localized π electron structures in particle nucleation and subsequent mass growth. The existence of these free radicals provides a rational explanation for the strong binding forces needed for forming initial clusters of polycyclic aromatic hydrocarbons. They may also explain a range of currently unexplained sooting phenomena, including the large amount of aliphatics observed in nascent soot formed in laminar premixed flames and the mass growth of soot in the absence of gas-phase H atoms. While the above suggestions are inspired, to an extent, by recent theoretical findings from the materials research community, this paper also demonstrates that the knowledge garnered through our longstanding interest in soot formation may well be carried over to flame synthesis of functional nanomaterials for clean and renewable energy applications. In particular, work on flame-synthesized thin films of nanocrystalline titania illustrates how our combustion knowledge might be useful for developing advanced yet inexpensive thin-film solar cells and chemical sensors for detecting gaseous air pollutants.

Formation of nascent soot and other condensed-phase materials in flames

Chemical characterization of particulate emissions from diesel engines: A review

Intuitively, the rate of heat release from an unwanted fire is a major indication of the threat of the fire to life and property. This is indeed true, and a reliable measurement of a fire’s heat release rate was a goal of fire researchers at NBS and other fire laboratories at least as early as the 1960s. Historically, heat release measurements of burning materials were based on the temperature rise of ambient air as it passed over the burning object. Because the fraction of heat released by radiant emission varies with the type of material being burned, and because not all the radiant energy contributes to temperature rise of the air, there were large errors in the measurements. Attempts to account for the heat that was not captured by the air required siting numerous thermal sensors about the fire to intercept and detect the additional heat. This approach proved to be tedious, expensive, and susceptible to large errors, particularly when the burning “object” was large, such as a full-sized room filled with flammable furnishings and surface finishes. A novel alternative technique for determining heat release rate was developed at NBS during the 1970s. It had distinct advantages over the customary approach, but its widespread acceptance was hampered by uneasiness in the fire science community concerning potential errors if the technique were used in less-than-ideal circumstances. In 1980 Clayton Huggett, a fire scientist at NBS, published the seminal paper [1] that convinced the fire science community that the new technique was scientifically sound and sufficiently accurate for fire research and testing. The technique is now used worldwide and forms the basis for several national and international standards. The underlying principle of the new heat release rate technique was “discovered” in the early 1970s. Faced with the challenge of measuring the heat release of combustible wall linings during full-scale room fire tests, William Parker, Huggett’s colleague at NBS, investigated an alternative approach based on a simple fact of physics: in addition to the release of heat, the combustion process consumes oxygen. As part of his work on the ASTM E 84 tunnel test, Parker [2] explored the possibility of using a measurement of the reduction of oxygen in fire exhaust gases as an indicator of the amount of heat released by the burning test specimens. Indeed, for well-defined materials with known chemical composition, heat release and oxygen consumption can both be calculated from thermodynamic data. The problem with applying this approach to fires is that in most cases the chemical compositions of modern materials/ composites/mixes that are likely to be involved in real fires are not known. In the process of examining data for complete combustion (combustion under stoichiometric or excess air conditions) of the polymeric materials with which he was working, Parker found that, although the heat released per unit mass of material consumed (i.e., the specific heat of combustion), varied greatly, the amount of heat released per unit volume of oxygen consumed was fairly constant, i.e., within 15 % of the value for methane, 16.4 MJ/m of oxygen consumed. This fortunate circumstance—that the heat release rate per unit volume of oxygen consumed is approximately the same for a range of materials used to construct buildings and furnishings—meant that the heat release rate of materials commonly found in fires could be estimated by capturing all of the products of combustion in an exhaust hood and measuring the flow rate of oxygen in that exhaust flow. The technique was dubbed oxygen consumption calorimetry, notwithstanding the absence of any actual calorimetric (heat) measurements. Later in the decade, Huggett [1] performed a detailed analysis of the critical assumption of constant proportionality of oxygen consumption to heat release. Parker’s assumption was based on enthalpy calculations for the complete combustion of chemical compounds to carbon dioxide, water, and other fully oxidized compounds. Indeed, a literature review by Huggett revealed that Parker’s findings were actually a rediscovery and extension of the work of W. M. Thornton [3], published in 1917, which found that the heat released per unit amount of oxygen consumed during the complete combustion of a large number of organic gases and liquids was fairly constant. Nevertheless, since in real fires and fire experiments the oxygen supply is sometimes limited, incomplete combustion and partially oxidized products can be produced. Huggett’s paper examined in detail the assumption of constant heat release per amount of oxygen consumed under real fire conditions and assessed its effect on the accuracy of heat release rate determinations for fires. Instead of expressing results on a unit volume basis, as Parker did, Huggett expressed results in the more convenient and less ambiguous unit mass of oxygen

Estimation of Rate of Heat Release by Means of Oxygen Consumption Measurements

Impact of fuel formulation on the nanostructure and reactivity of diesel soot

An investigation on the morphology, internal microstructure, and fractal geometry of particulate matter (PM) was conducted for a 1.7-L light-duty diesel engine. The experimental and analytical instruments used in this study include a unique thermophoretic sampling system, a high-resolution transmission electron microscope (TEM), customized digital image processing/data acquisition system, and a Raman scattering spectrometer that have been extensively used at Argonne National Laboratory. During experiments, diesel particulates were directly collected from the exhaust stream. In the morphological observations using TEM, graphitic crystallite structures were found from these light-duty diesel particulates, particularly at high engine loads. In subsequent analysis, Raman spectra revealed details of these graphitic structures quantitatively: the collected diesel PM was quite similar in atomic structures to typical graphite, and the degree of its crystalline structures increased as the engine load increased. In PM size measurements, mean primary particle diameters ( d p ) are in a range of 19.4–32.5 nm and radii of gyration ( R g ) in a range of 77.4–134.1 nm, respectively, across the engine operating conditions of 780–4000 rpm and 0–100% loads. From the fractal analysis, smaller fractal dimensions ( D f ) (1.46–1.70) were measured for the light-duty diesel engine used in this study, compared to those of heavy-duty diesel particulates that ranged in 1.80–1.88. This result implies that more stretched chain-like particles were produced from the light-duty engine under the diffusion-limit formation mechanism. The database on the physical dimension and fractal geometry of light-duty diesel PM obtained from this study offers data for the future standards of diesel PM sizes and development of advanced diesel PM emission control technologies.

Effects of engine operating conditions on morphology, microstructure, and fractal geometry of light-duty diesel engine particulates

Combustion and oxy-fuel combustion characteristics of torrefied pine wood chips were investigated by Thermogravimetric Analysis (TGA). Three torrefaction temperatures (250, 300, and 350 °C) and two residence times (15 and 30 min) were considered. Experiments were carried out at three heating rates of 10, 20, and 40 °C/min. The isoconversional kinetic methods of FWO, KAS, and Friedman were employed to estimate the activation energies. The assessment of uncertainty in obtaining the activation energy values was also considered. The obtained results indicated that due to torrefaction, the O/C and H/C atomic ratios decreased, resulting the 300oC-30 min and 350oC-15 min torrefied biomass to be completely embedded in lignite region in van-Krevelen's diagram. Oxy-fuel combustion affected the decomposition of cellulose and lignin components of biomass while the impact on the hemicellulose component was negligible. The kinetic analysis revealed that with the evolution of conversion degree, the activation energy values increased during hemicellulose degradation, remained approximately constant during cellulose decomposition and showed a sharp decrease for lignin decomposition. The activation energy trends were comparable in both air and oxy-fuel combustion conditions, however slight changes in activation energy values were noticed. The highest activation energy value was obtained for 250oC-30 min torrefied biomass at 183.40 kJ/mol and the lowest value was 72.93 kJ/mol for 350oC-15 min biomass. The uncertainty values related to FWO method were lower than KAS and Friedman methods. The uncertainty values for FWO and KAS methods were at the range of 5–15%.

TGA and kinetic study of different torrefaction conditions of wood biomass under air and oxy-fuel combustion atmospheres

A well-stirred reactor (WSR) followed by a plug flow reactor (PFR) is being used to study polycyclic aromatic hydrocarbon (PAH) growth and soot inception. Soot size distributions were measured using a dilution probe followed by a nano-differential mobility analyzer (Nano-DMA). A rapid insertion probe was fabricated to thermophoretically collect particles from the reactor for transmission electron microscopy (TEM) imaging. Results are presented on the effect of equivalence ratio on the soot size distributions obtained for fixed dilution ratio, the effect of dilution ratio on the soot size distributions obtained for fixed equivalence ratio, and the effect of temperature on the soot size distributions obtained for fixed equivalence ratio. In addition to particle sizing measurements, gas samples were analyzed by a gas chromatograph to determine the concentration of gaseous species in the PFR thought to be important in soot formation. Our soot size distribution measurements demonstrate that the mixing conditions in the flame zone affect whether or not a nucleation mode was detected in the size distribution. Published by Elsevier Inc. on behalf of The Combustion Institute.

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Ahmet Yozgatligil

Papers

Effects of engine operating conditions on morphology, microstructure, and fractal geometry of light-duty diesel engine particulates

TGA and kinetic study of different torrefaction conditions of wood biomass under air and oxy-fuel combustion atmospheres

Soot particle size distributions in a well-stirred reactor/plug flow reactor

A study on the effects of catalysts on pyrolysis and combustion characteristics of Turkish lignite in oxy-fuel conditions

Sizes, Graphitic Structures and Fractal Geometry of Light-Duty Diesel Engine Particulates