Advances in rapid compression machine studies of low- and intermediate-temperature autoignition phenomena

© 2017 Elsevier Ltd Rapid compression machines (RCMs) are widely used to acquire experimental insights into fuel autoignition and pollutant formation chemistry, especially at conditions relevant to current and future combustion technologies. RCM studies emphasize important experimental regimes, characterized by low- to intermediate-temperatures (600–1200 K) and moderate to high pressures (5–80 bar). At these conditions, which are directly relevant to modern combustion schemes including low temperature combustion (LTC) for internal combustion engines and dry low emissions (DLE) for gas turbine engines, combustion chemistry exhibits complex and experimentally challenging behaviors such as the chemistry attributed to cool flame behavior and the negative temperature coefficient regime. Challenges for studying this regime include that experimental observations can be more sensitive to coupled physical-chemical processes leading to phenomena such as mixed deflagrative/autoignitive combustion. Experimental strategies which leverage the strengths of RCMs have been developed in recent years to make RCMs particularly well suited for elucidating LTC and DLE chemistry, as well as convolved physical-chemical processes. Specifically, this work presents a review of experimental and computational efforts applying RCMs to study autoignition phenomena, and the insights gained through these efforts. A brief history of RCM development is presented towards the steady imp rovement in design, characterization, instrumentation and data analysis. Novel experimental approaches and measurement techniques, coordinated with computational methods are described which have expanded the utility of RCMs beyond empirical studies of explosion limits to increasingly detailed understanding of autoignition chemistry and the role of physical-chemical interactions. Fundamental insight into the autoignition chemistry of specific fuels is described, demonstrating the extent of knowledge of low-temperature chemistry derived from RCM studies, from simple hydrocarbons to multi-component blends and full-boiling range fuels. Emerging needs and further opportunities are suggested, including investigations of under-explored fuels and the implementation of increasingly higher fidelity diagnostics

The analysis and discrimination of pyrolysis products from biological and non-biological sources

This work involves the limited use of human tissue samples. These samples were obtained through body donation and under full ethical approval from the University of Strathclyde ethics committee. Products generated through pyrolysis of common materials can act as background compounds, interfering with the analysis and identification of potential human remains. The development of a robust methodology for the generation and analysis of volatile products from biological (porcine and human tissues) and non-biological (textile materials) sources stands at the core of this study, combined with examining various factors that causes these profiles to deviate. This process began with the validation of porcine samples as a substitute of human samples through the identification of similar key indicators, characteristic to both tissues. Interestingly, different temperature ranges (pre- and post-ignition) and type of porcine tissues utilised were found to effect the type of key indicators detected; and as such, has convincingly resolved key indicators reported in previous research literature. In addition, key indicators of pure and blended textiles were also established and the effects of blended fibres towards the overall thermal properties of the textile, highlighted. Alterations to the key indicators of individual porcine and textile samples were examined, subjectively and objectively, when both samples were burnt together (combined samples). Subjective analysis involved the scrutiny of the chromatographic output, revealing the dominance of key indicators of porcine samples over textiles for majority of the combined samples. EIC and EIP proved to be a beneficial tool in extracting key indicators of porcine samples in the presence of contamination (textiles). At 70% presence, SOFM provided an objective and successful classification and discrimination of pyrolytic data according to the type of pyrolysis product detected across textiles, porcine bones and also in the combined textile-bone samples while underlining meaningful associations amongst similar groups. Overall, although this work suggests that pyrolytic data can be unpredictable, such as its dependence on various factors, with suitable analytical and statistical techniques, it has revealed pertinent information on the key indicators of porcine, human and textiles samples and the inter- and intra-molecular changes that occur to them during pyrolysis.This work involves the limited use of human tissue samples. These samples were obtained through body donation and under full ethical approval from the University of Strathclyde ethics committee. Products generated through pyrolysis of common materials can act as background compounds, interfering with the analysis and identification of potential human remains. The development of a robust methodology for the generation and analysis of volatile products from biological (porcine and human tissues) and non-biological (textile materials) sources stands at the core of this study, combined with examining various factors that causes these profiles to deviate. This process began with the validation of porcine samples as a substitute of human samples through the identification of similar key indicators, characteristic to both tissues. Interestingly, different temperature ranges (pre- and post-ignition) and type of porcine tissues utilised were found to effect the type of key indicators detected; and as such, has convincingly resolved key indicators reported in previous research literature. In addition, key indicators of pure and blended textiles were also established and the effects of blended fibres towards the overall thermal properties of the textile, highlighted. Alterations to the key indicators of individual porcine and textile samples were examined, subjectively and objectively, when both samples were burnt together (combined samples). Subjective analysis involved the scrutiny of the chromatographic output, revealing the dominance of key indicators of porcine samples over textiles for majority of the combined samples. EIC and EIP proved to be a beneficial tool in extracting key indicators of porcine samples in the presence of contamination (textiles). At 70% presence, SOFM provided an objective and successful classification and discrimination of pyrolytic data according to the type of pyrolysis product detected across textiles, porcine bones and also in the combined textile-bone samples while underlining meaningful associations amongst similar groups. Overall, although this work suggests that pyrolytic data can be unpredictable, such as its dependence on various factors, with suitable analytical and statistical techniques, it has revealed pertinent information on the key indicators of porcine, human and textiles samples and the inter- and intra-molecular changes that occur to them during pyrolysis