Understanding upstream flame propagation in scramjets is challenging, particularly concerning flame flashback in a combustor with a novel strut-cavity flame holder. Two-dimensional unsteady Reynolds-averaged Navier–Stokes (URANS) simulations were performed to investigate how Mach number and wall divergence affect flame behavior. The utility of the strut-cavity flame holder was highlighted through a study of its non-reacting flow characteristics. Flow dynamics are significantly altered as the shear layer above the cavity interacts with the downstream hydrogen jet. Shear layer dynamics and fuel-air mixing are improved through key factors such as shock-train behavior, cavity oscillations, and transverse fuel injection. The submerged fuel jet is less exposed to supersonic flow and demonstrates reduced entropy rise, achieving a 16% increase in mixing efficiency compared to standalone struts and a 46% improvement over transverse injection without a flame holder. Thermal choking shifts the shock train upstream, facilitating interactions with the shear layer and enhancing vortex formation, which decreases flow speed and promotes upstream flame propagation. The presence of OH radicals indicates that flame flashback follows a periodic pattern with an initial gradual slope, suggesting effective anchoring. Stability and flashback likelihood are affected by low-speed zones, vortex merging, and wall divergence. At Mach 3, combustion efficiency improves without wall divergence due to increased heat release, while wall divergence prevents flame flashback by sustaining supersonic core flow and managing flow-flame interactions. At higher core flow velocities, flame stabilization occurs at the cavity's separation corner, despite a tendency for upstream propagation, with validation of the URANS results achieved through two-dimensional large eddy simulations.
In this recent paper from our group on SCRAM-RAM modes inside a Dual-Mode-Scramjet-Engine (DMSJ), Rajesh Kumar shows that for the Supersonic-at-Strut modes, shockwaves in the combustor respond predictably to an increase or decrease in fuel flow rates. Intermediate and final flow fields bear close resemblance to the steady state flow fields predicted by RANS for those fuel flow rates. Shocks adjust accordingly to match the combustion driven pressure rise. Under the Supersonic-at-Strut mode, when fuel flow rate is increased, the shocks steepen and concentrate near the base of the strut. When fuel flow rate is decreased, the opposite trend is observed wherein shocks become more oblique and spread away downstream from the base of the strut. For the Subsonic-at-Strut modes, shockwaves in the flow field are rather unstable to fuel flow rate modulations. Any change in fuel flow rates causes the isolator shocks to immediately move upstream irrespective of if the fuel flow rate is increased or decreased, suddenly or gradually. Because of this instability of isolator shocks for the Subsonic-at-Strut modes, feedback control of isolator shocks using fuel-flow rate modulations alone may not be feasible.
🚀 Just returned from the Aviation Forum 2024, and what an incredible experience it was! I am grateful to my supervisor, Dr. Amardip Ghosh, for his consistent support and insightful advice, and many thanks to my institute, the Indian Institute of Technology Kharagpur, India, for the financial support that made this journey possible. 🙏
What happens in Vegas doesn’t stay in Vegas – it’s coming with me as newfound knowledge and inspiration for my future work! ✈️
I had the pleasure of presenting my paper titled "Effect of Wall Divergence on the Flow Field Inside a Scramjet Engine" (DOI: 10.2514/6.2024-3891). Engaging with fellow researchers and exchanging ideas has truly been inspiring. The conference was a fantastic opportunity to connect with some brilliant minds in the field of aerodynamics and propulsion.
I’m also deeply thankful to my co-authors for their dedication and hard work in ensuring we met the submission deadline. Your contribution was key to our success. A special thanks to Dipesh Raj, a fellow researcher, for his invaluable help in planning and organizing everything – we couldn't have done it without you!
Looking forward to applying these experiences and insights as I continue the journey in aviation research! ✈️
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Insights into flame flashback phenomenon utilizing a Strut-Cavity flame holder inside scramjet combustor
Pranay Singeetham #Advanced Propulsion Systems (APSYS) Lab @Amardip Ghosh
Understanding upstream flame propagation in scramjets is challenging, particularly concerning flame flashback in a combustor with a novel strut-cavity flame holder. Two-dimensional unsteady Reynolds-averaged Navier–Stokes (URANS) simulations were performed to investigate how Mach number and wall divergence affect flame behavior. The utility of the strut-cavity flame holder was highlighted through a study of its non-reacting flow characteristics. Flow dynamics are significantly altered as the shear layer above the cavity interacts with the downstream hydrogen jet. Shear layer dynamics and fuel-air mixing are improved through key factors such as shock-train behavior, cavity oscillations, and transverse fuel injection. The submerged fuel jet is less exposed to supersonic flow and demonstrates reduced entropy rise, achieving a 16% increase in mixing efficiency compared to standalone struts and a 46% improvement over transverse injection without a flame holder. Thermal choking shifts the shock train upstream, facilitating interactions with the shear layer and enhancing vortex formation, which decreases flow speed and promotes upstream flame propagation. The presence of OH radicals indicates that flame flashback follows a periodic pattern with an initial gradual slope, suggesting effective anchoring. Stability and flashback likelihood are affected by low-speed zones, vortex merging, and wall divergence. At Mach 3, combustion efficiency improves without wall divergence due to increased heat release, while wall divergence prevents flame flashback by sustaining supersonic core flow and managing flow-flame interactions. At higher core flow velocities, flame stabilization occurs at the cavity's separation corner, despite a tendency for upstream propagation, with validation of the URANS results achieved through two-dimensional large eddy simulations.
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Instability of isolator shocks to fuel flow rate modulations in a strut-stabilised scramjet combustor
Amardip Ghosh #Advanced Propulsion Systems (APSYS) Lab
In this recent paper from our group on SCRAM-RAM modes inside a Dual-Mode-Scramjet-Engine (DMSJ), Rajesh Kumar shows that for the Supersonic-at-Strut modes, shockwaves in the combustor respond predictably to an increase or decrease in fuel flow rates. Intermediate and final flow fields bear close resemblance to the steady state flow fields predicted by RANS for those fuel flow rates. Shocks adjust accordingly to match the combustion driven pressure rise. Under the Supersonic-at-Strut mode, when fuel flow rate is increased, the shocks steepen and concentrate near the base of the strut. When fuel flow rate is decreased, the opposite trend is observed wherein shocks become more oblique and spread away downstream from the base of the strut. For the Subsonic-at-Strut modes, shockwaves in the flow field are rather unstable to fuel flow rate modulations. Any change in fuel flow rates causes the isolator shocks to immediately move upstream irrespective of if the fuel flow rate is increased or decreased, suddenly or gradually. Because of this instability of isolator shocks for the Subsonic-at-Strut modes, feedback control of isolator shocks using fuel-flow rate modulations alone may not be feasible.
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Effect of Wall Divergence on the Flow Field Inside a Scramjet Engine
Rajesh Kumar #Advanced Propulsion Systems (APSYS) Lab @Amardip Ghosh
🚀 Just returned from the Aviation Forum 2024, and what an incredible experience it was! I am grateful to my supervisor, Dr. Amardip Ghosh, for his consistent support and insightful advice, and many thanks to my institute, the Indian Institute of Technology Kharagpur, India, for the financial support that made this journey possible. 🙏
What happens in Vegas doesn’t stay in Vegas – it’s coming with me as newfound knowledge and inspiration for my future work! ✈️
I had the pleasure of presenting my paper titled "Effect of Wall Divergence on the Flow Field Inside a Scramjet Engine" (DOI: 10.2514/6.2024-3891). Engaging with fellow researchers and exchanging ideas has truly been inspiring. The conference was a fantastic opportunity to connect with some brilliant minds in the field of aerodynamics and propulsion.
I’m also deeply thankful to my co-authors for their dedication and hard work in ensuring we met the submission deadline. Your contribution was key to our success. A special thanks to Dipesh Raj, a fellow researcher, for his invaluable help in planning and organizing everything – we couldn't have done it without you!
Looking forward to applying these experiences and insights as I continue the journey in aviation research! ✈️
#AviationForum2024 #Research #Networking #Gratitude
Attachments