In this final installment of a 14-part series of articles, The Combustion Institute recognizes the 2017 Distinguished Papers selected from among the scientific papers presented during the 36th International Symposium on Combustion. Congratulations to Nancy Faßheber, Marvin C. Schmidt, and Gernot Friedrichs for winning the DPA in the Reaction Kinetics colloquium.

The authoritative paper, Quantitative HNO detection behind shock waves, presents the first Nitroxyl (HNO) absorption measurements behind shock waves, a key species in NOx flame chemistry. The paper’s research targets on direct measurements of rate constant data that are relevant for modeling NOx formation in flames.

Performing a series of shock tube experiments under well-controlled high-temperature reaction conditions, the scientific team successfully generated and detected HNO as well as formyl radicals (HCO) in the gas phase at temperatures up to 1800 K (2073°C). Building on previous work on HCO, the team was able to reproduce both HCO and HNO concentration-time-profiles. They succeeded in putting the measured HNO signal levels on an absolute concentration scale and were able to determine the HNO absorption cross section.

The determined HNO high-temperature absorption cross section forms the basis for much-needed direct kinetic measurements of bimolecular HNO reactions at combustion relevant temperatures. The scientific team’s research in the paper can lead to cleaner and more efficient combustion, which can decrease NOx pollution and hence prevent environmental damage and reduce human health risks. To achieve this goal, a detailed knowledge of the reaction mechanisms in flames is essential to provide a sound chemical background for the design of improved combustors that offer both higher efficiency and lower pollutant emissions.

The immediate impact of the paper raises awareness in the combustion community that current understanding of HNO flame chemistry remains unsatisfying. For that reason, HNO must be studied more closely by experimentalists, modelers and theoreticians. This will lead to improved chemical reaction mechanisms for NOx formation that can be adopted for modeling of practical combustion devices.

The direct measurements of HNO high temperature kinetics hold the potential for an experimentally verified and improved understanding of NOx formation in flames. The scientific team plans to perform such measurements using their shock tube apparatus in the near future. However, the data provided in the paper serve as the basis for other kinetic experiments as well, for example the quantitative detection of HNO in model flames and for reaction kinetic studies in high temperature flow reactors.

The paper’s research took place at the Institute for Physical Chemistry, Christian-Albrechts-University Kiel, Germany. Research efforts for the paper started in 2014 and HNO experiments came later. The valuable data set was submitted as a paper prior to the 36th International Symposium on Combustion in Seoul, Korea. The scientific team is planning to continue their efforts in further improving the HNO detection scheme and measurements on bimolecular HNO reactions.

About 1,300 papers were submitted to the 36th Symposium in 14 combustion science colloquia. Those papers were categorized by teams of colloquium coordinators and co-chairs, and then distributed to approximately 1,000 scientific reviewers. One paper in each discipline was awarded the recognition of Distinguished Paper.

The 14 Distinguished Papers undergo committee review for consideration to receive the Silver Combustion Medal that will be awarded during the 37th Symposium in Dublin, Ireland. A paper selected for this honor exemplifies quality, achievement, and significance to advance a field of combustion science. Distinguished papers are selected biennially from among the scientific papers presented during the International Symposium on Combustion and accepted for publication in the Proceedings of The Combustion Institute.