EAGER: A Shock Tube Study of Laminar Flames in Transportation Fuels at Engine Relevant Temperatures

Stanford University, Stanford CA

Investigators

Abstract

This project aims to develop novel experimental techniques for studying flames at conditions relevant to transportation systems. Currently, experimental limitations prevent the study of premixed flames at the high-temperatures found in modern spark-ignition and jet engines. By using shock tubes, this work aims to overcome those practical limits and allow future experimental studies to be conducted at the conditions most relevant to modern engines. Exploratory work will also be undertaken to understand unique structures only present in high-temperature flames. Together, this work will support the development of the clean and efficient engines needed to meet the critical goals of reducing air pollution, reigning in transportation-related greenhouse gas emissions, and limiting dependence on foreign fossil fuels. The first of two major goals of this project is to refine the shock-tube flame speed method recently demonstrated in the Hanson laboratory. The rapid heating and quiescent post-shock conditions in a shock tube allow for spherically expanding flames to be initiated and studied at previously inaccessible temperatures. This method will be further refined and validated to optimize experimental and data-processing methods in order to ensure that high-temperature flame data produced using the method meets the high quality standards of the scientific and engineering communities. The second major goal is to use a variety of laser- and imaging-based diagnostics to study peculiar flame structures observed at high temperatures. Both simulations and preliminary experimental evidence suggest that two-stage flames, with a cool flame preceding the classical hot flame, may be observed at high temperatures. This phenomenon will be experimentally investigated, an objective that will leverage both the unique ability to generate flames at high temperatures afforded by the shock tube and the existing optical diagnostic expertise of the Hanson lab. Diagnostics to be employed in the study of high-temperature flame structure are likely to include line-of-sight laser absorption, planar laser-induced fluorescence, and spectrally filtered emission imaging. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.