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For several years the Air Force Research Lab Propulsion Directorate has been studying the difficulties in fueling supersonic combustion ramjet engines with hydrocarbon based fuels. Recent investigations have focused on the use of direct air injection into a directly-fueled cavity-based flameholder. Direct air injection has been shown qualitatively to be a valuable tool for improving cavity combustion. Little quantitative data is available that characterizes the performance of cavity-based flameholders. The objective of this research was to quantitatively determine the specific advantages and disadvantages of the direct air injection scheme. This was accomplished via intrusive probing into a supersonic free stream flow at an axial location behind the cavity flameholder. Pitot and static pressure, total temperature, and gas sampling measurements were taken and the corresponding values were processed to yield relevant engineering quantities. Data were taken over a range of fuel and air injection rates. Direct air injection resulted in increased combustion throughout the area of interest behind the cavity. Air injection increased the static temperature and pressure throughout the area of interest. Enthalpy spread into the free stream was also increased through the use of air injection. Total pressure losses increased as a result of the direct air injection scheme. The ratio of enthalpy increase to increase in total pressure losses increased with higher fuel flow rates, indicating that the direct air injection technique shows more promise for higher fuel loadings.This work has been selected by scholars as being culturally important, and is part of the knowledge base of civilization as we know it. This work was reproduced from the original artifact, and remains as true to the original work as possible. Therefore, you will see the original copyright references, library stamps (as most of these works have been housed in our most important libraries around the world), and other notations in the work.This work is in the public domain in the United States of America, and possibly other nations. Within the United States, you may freely copy and distribute this work, as no entity (individual or corporate) has a copyright on the body of the work.As a reproduction of a historical artifact, this work may contain missing or blurred pages, poor pictures, errant marks, etc. Scholars believe, and we concur, that this work is important enough to be preserved, reproduced, and made generally available to the public. We appreciate your support of the preservation process, and thank you for being an important part of keeping this knowledge alive and relevant.
