The paper “Turbulence and Area Production in Binary-Species, Super- critical Transitional Mixing Layers” presents a more recent account of the research sum- marized at an earlier stage in “Area Production in Super- critical, Transitional Mixing Layers” (NPO-30425), NASA Tech Briefs, Vol. 26, No. 5 (May 2002) page 79. The focus of this research is on supercritical C7H16/N2 and O2/H2 mixing layers undergoing transitions to turbulence. The C7H16/N2 system serves as a simplified model of hydrocarbon/air systems in gasturbine and diesel engines; the O2/H2 system is representative of liquid rocket engines. One goal of this research is to identify ways of controlling area production to increase disintegration of fluids and enhance combustion in such engines. As used in this research, “area production” signifies the fractional rate of change of surface area oriented perpendicular to the mass-fraction gradient of a mixing layer. In the study, a database of transitional states obtained from direct numerical simulations of the aforementioned mixing layers was analyzed to investigate global layer characteristics, phenomena in regions of high density-gradient magnitude (HDGM), irreversible entropy production and its relationship to the HDGM regions, and mechanisms leading to area production.
This work was done by Nora Okong’o and Josette Bellan of Caltech for NASA’s Jet Propulsion Laboratory.
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Update on Area Production in Mixing of Supercritical Fluids
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Overview
The document presents a technical report on research conducted by NASA’s Jet Propulsion Laboratory (JPL) regarding turbulence and area production in binary-species, supercritical transitional mixing layers. The focus of the study is on two specific systems: C₇H₁₆/N₂, which serves as a simplified model for hydrocarbon/air systems in gas turbine and diesel engines, and O₂/H₂, representative of liquid rocket engines.
The primary objective of the research is to identify methods to control area production, which is defined as the fractional rate of change of surface area oriented perpendicular to the mass-fraction gradient of a mixing layer. This control is essential for enhancing the disintegration of fluids, thereby improving combustion efficiency in various engine types. The study utilizes a database of transitional states obtained from direct numerical simulations to analyze global layer characteristics, phenomena in regions of high density-gradient magnitude (HDGM), and the relationship between irreversible entropy production and HDGM regions.
The document emphasizes the novelty of the research, noting that there are currently no existing calculations of area production in supercritical flows. The motivation behind the study stems from the need to predict the disintegration of supercritical jets of fluids introduced into combustion chambers, which is critical for effective fuel combustion in engines. The researchers, Nora Okong’o and Josette Bellan, have developed a model that predicts the increase in area of optically observed parcels of fluid, providing valuable insights into fluid disintegration processes.
The report also includes a disclaimer regarding the use of trade names and manufacturers' names, clarifying that such references do not imply endorsement by the U.S. Government or JPL. The work was carried out under contract with NASA, highlighting the collaborative nature of the research.
In summary, this document outlines significant advancements in understanding turbulence and area production in supercritical mixing layers, with implications for improving combustion processes in gas turbine, diesel, and rocket engines. The findings aim to contribute to the development of more efficient combustion technologies, ultimately enhancing performance and reducing emissions in aerospace applications.
