Designing scramjets with extremely high-speed propulsion just got easier: Numerical simulations show the effects of shockwaves on fluid vortices and detail the complex wave forms and chemical reactions in shocked fuel.
In a jet engine, the flow of air is slowed down to increase the temperature and pressure for combustion -- burning fuel with the right ratio of fuel and air to conquer drag allows for acceleration.
Instantaneous distributions of dimensionless temperature T/T0 and fuel mass fraction, with blue dashed lines given by YF=0.05: (top, Case LP-OS1) weak shock with stoichiometric mixture, (middle, Case LP-OS2) strong shock with stoichiometric mixture, and (bottom, Case LP-OS2-H) strong shock with fuel-rich mixture. Here, the gray dots indicate evaporating fuel droplets.
Credit: Zhaoxin Ren, Bing Wang and Longxi Zheng
Usage Restrictions: This image may be used only with appropriate credit.
But in supersonic engines achieving the right flow speed, producing the right ratio of evaporated fuel and causing ignition at the right time is more complex. With evaporating liquid in a combustion chamber, there is more at play than just gravity and drag, especially with supersonic shock waves in the equation.
Vortices -- the dynamic structures created in a turbulent flow --are affected by the shock wave. This changes the way the fuel combusts and multiplies the number of possibilities of how particles can behave. To deepen our understanding of the dynamics of supersonic flow, researchers look to numerical modeling to calculate the huge variety of possible outcomes in this changed system.
In their study, published this week in Physics of Fluids, by AIP Publishing, Zhaoxin Ren, Bing Wang and Longxi Zheng viewed supersonic combustion in a time series through numerical modeling. This allowed them to see how changing variables, such as mass loading fuel, the intensity of the shock wave, and the types of reflecting and transmitted waves created at different points in time will affect ignition.
They were able to quantitatively characterize the influence of an incident oblique shock wave on large-scale shearing vortices and exothermal reactions, mathematically mapping the influence of variables and the resulting types of waves created in a shocked gas. Their analysis establishes a reliable simulation method for supersonic combustion using mathematical modeling tools specifically designed for this purpose.
"Currently, no commercial software can simulate the supersonic combustion problem because it requires high-order numerical schemes to compute supersonic flows with complicated evolved shocks, as well as corrected models to describe the droplet dynamics, both of which we carefully consider in our in-house simulation codes," Wang said, a co-author of the study. "Direct numerical simulation can capture the full scales of flows involved in the shock-vortex interaction."
Using a combination of custom simulation codes and the Eulerian-Lagrangian method commonly applied to particle-laden two-phase flows, the authors were able to run a broad range of simulations and provide a series of test cases that inform scramjet engine design. Their analysis revealed two induced combustion modes, including a local quasi detonation mode that occurs due to the formation of a refracted wave coupled with the chemical reaction.
"The scramjet engine is the most favorable option for high-speed flight at Mach six or more," Wang said. "Understanding the complicated physical mechanism of supersonic combustion and the impact of incident shock waves could help engineers choose the best combination of mixing and combustion through installing movable components in the combustor."
The article, "Numerical analysis on interactions of vortex, shock wave and exothermal reaction in a supersonic planar shear layer laden with droplets," is authored by Zhaoxin Ren, Bing Wang and Longxi Zheng. The article appeared in Physics of Fluids March 13, 2018 (DOI: 10.1063/1.5011708) and can be accessed at https:/
ABOUT THE JOURNAL
Physics of Fluids is devoted to the publication of original theoretical, computational, and experimental contributions to the dynamics of gases, liquids, and complex or multiphase fluids. See http://pof.
Julia Majors | EurekAlert!
Robert Alfano team identifies new 'Majorana Photons'
16.07.2019 | City College of New York
Hubble discovers mysterious black hole disc
12.07.2019 | ESA/Hubble Information Centre
Scientists at the University Würzburg and University Hospital of Würzburg found that megakaryocytes act as “bouncers” and thus modulate bone marrow niche properties and cell migration dynamics. The study was published in July in the Journal “Haematologica”.
Hematopoiesis is the process of forming blood cells, which occurs predominantly in the bone marrow. The bone marrow produces all types of blood cells: red...
For some phenomena in quantum many-body physics several competing theories exist. But which of them describes a quantum phenomenon best? A team of researchers from the Technical University of Munich (TUM) and Harvard University in the United States has now successfully deployed artificial neural networks for image analysis of quantum systems.
Is that a dog or a cat? Such a classification is a prime example of machine learning: artificial neural networks can be trained to analyze images by looking...
An international research group led by scientists from the University of Bayreuth has produced a previously unknown material: Rhenium nitride pernitride. Thanks to combining properties that were previously considered incompatible, it looks set to become highly attractive for technological applications. Indeed, it is a super-hard metallic conductor that can withstand extremely high pressures like a diamond. A process now developed in Bayreuth opens up the possibility of producing rhenium nitride pernitride and other technologically interesting materials in sufficiently large quantity for their properties characterisation. The new findings are presented in "Nature Communications".
The possibility of finding a compound that was metallically conductive, super-hard, and ultra-incompressible was long considered unlikely in science. It was...
An interdisciplinary research team at the Technical University of Munich (TUM) has built platinum nanoparticles for catalysis in fuel cells: The new size-optimized catalysts are twice as good as the best process commercially available today.
Fuel cells may well replace batteries as the power source for electric cars. They consume hydrogen, a gas which could be produced for example using surplus...
The fly agaric with its red hat is perhaps the most evocative of the diverse and variously colored mushroom species. Hitherto, the purpose of these colors was...
24.06.2019 | Event News
29.04.2019 | Event News
17.04.2019 | Event News
16.07.2019 | Power and Electrical Engineering
16.07.2019 | Information Technology
16.07.2019 | Physics and Astronomy