Evaluation of hydrogen combustion reaction mechanisms in large eddy simulations for supersonic hydrogen combustion
(2024) MVKM05 20241Department of Energy Sciences
- Abstract
- The scramjet engine is an air-breathing engine that can be used to travel at supersonic speeds. Research is being done into how these engines can be used as reusable launch vehicles for space travel, missile propulsion, and many hope one day scramjets can be used for commercial flight. Scramjets are highly beneficial in the sense that hydrogen is the primary fuel and that manufacturing is simple compared to other types of engines due to the lack of moving parts. The prospect of supersonic flight that doesn’t have large CO2 emissions is very exciting, but it is not without challenges. The thermal and structural load on both the engine and aircraft presents a heavy challenge in making scramjets viable, flight and combustion occur at... (More)
- The scramjet engine is an air-breathing engine that can be used to travel at supersonic speeds. Research is being done into how these engines can be used as reusable launch vehicles for space travel, missile propulsion, and many hope one day scramjets can be used for commercial flight. Scramjets are highly beneficial in the sense that hydrogen is the primary fuel and that manufacturing is simple compared to other types of engines due to the lack of moving parts. The prospect of supersonic flight that doesn’t have large CO2 emissions is very exciting, but it is not without challenges. The thermal and structural load on both the engine and aircraft presents a heavy challenge in making scramjets viable, flight and combustion occur at supersonic speeds which requires solutions for removing heat and using materials that can withstand such extreme temperatures. The residence time in the combustor for a scramjet is on the order of milliseconds which presents another challenge in ensuring good mixing and achieving combustion in a non-premixed flame environment. Understanding the combustion physics is key to optimizing these engines from both a mixing and combustion standpoint as well as thermal load management. The purpose of this study was to assess which hydrogen combustion reaction mechanism represents diffusion flame supersonic hydrogen combustion most accurately. Additionally determining important features for modeling supersonic diffusion flame was a secondary purpose of this study. Using computational fluid dynamics simulations the assessment of design considerations and the reaction mechanisms was made. It was found that boundary layer development and turbulence at the inlet were very important factors in modeling the case. For problems of this type the cross-over temperature region is an important consideration, mechanisms that have multiple progression paths depending on the temperature are favorable. The Baurle mechanism did not include HO2 and H2O2 chemistry which are vital radicals for combustion below the cross-over temperature. Validation against the benchmarking case was not achieved so making conclusions is difficult. Future work would include validating the simulation against experiments and comparing more than five mechanisms. (Less)
- Popular Abstract
- The scramjet engine is an engine that uses air from the atmosphere and hydrogen as fuel to travel at supersonic flight speeds. Research is being done into how these engines can be used for space travel, missile propulsion, and many hope one day scramjets can be used for commercial flight as well. Scramjets are highly beneficial in the sense that hydrogen is the primary fuel, hydrogen is a green fuel that does not produce carbon dioxide when burned. Additionally, scramjets don’t have any moving pieces which makes manufacturing and producing these engines relatively simple compared to other engines. The prospect of supersonic flight that doesn’t have large carbon dioxide emissions is very exciting, but it is not without challenges. The... (More)
- The scramjet engine is an engine that uses air from the atmosphere and hydrogen as fuel to travel at supersonic flight speeds. Research is being done into how these engines can be used for space travel, missile propulsion, and many hope one day scramjets can be used for commercial flight as well. Scramjets are highly beneficial in the sense that hydrogen is the primary fuel, hydrogen is a green fuel that does not produce carbon dioxide when burned. Additionally, scramjets don’t have any moving pieces which makes manufacturing and producing these engines relatively simple compared to other engines. The prospect of supersonic flight that doesn’t have large carbon dioxide emissions is very exciting, but it is not without challenges. The temperatures achieved in the engine and the stress put on the body of the aircraft structure due to the nature of supersonic flight presents a problem. Flight and combustion occur at supersonic speeds which require solutions for removing heat and using materials that can withstand such extreme temperatures. Another problem is that since flight and combustion occur at supersonic speeds the air and hydrogen are in the engine for a short amount of time, in the order of milliseconds. For a mixture of fuel and air to combust there needs to be sufficient mixing between the two, which is difficult when the mixture is only in the engine for a few milliseconds, this presents a design challenge and damages fuel efficiency. Understanding the combustion process occurring in the engine is key to optimizing these engines from both an air-fuel mixing and combustion standpoint as well as managing the high temperatures that the aircraft is subjected to. When a chemical reaction occurs there is a unique pathway of reactions that take place to get to the final result. This is called a reaction mechanism and there are several available for the combustion of hydrogen, some mechanisms work well for certain conditions, others have less steps to prevent complexity, and some are complete yet very complex. The purpose of this study was to assess which hydrogen combustion reaction mechanism represents the combustion that occurs in a scramjet most accurately. Additionally determining important features for modeling supersonic combustion in a scramjet was a secondary purpose of this study. Using computational fluid dynamics simulations, the assessment of design considerations and the reaction mechanisms was made. It was found that ensuring accuracy of the flow around the walls of the scramjet known as the boundary layer was critical and that modeling the innate disturbances in the flow known as turbulence at the inlet were very important factors in modeling this case. For problems of this type there is a specific temperature known as the cross-over temperature where the reaction will proceed down different pathways. Some mechanisms account for this and include multiple pathways, for this problem type this preferrable as the conditions include the cross-over temperature. The Baurle mechanism did not include HO2 and H2O2 chemistry which are vital radicals for the combustion pathway below the cross-over temperature, so this mechanism is not the best choice for this case. Validation against the benchmarking case was not achieved so making conclusions is difficult. Future work would include validating the simulation against experiments and comparing more than five mechanisms. (Less)
Please use this url to cite or link to this publication:
http://lup.lub.lu.se/student-papers/record/9177342
- author
- Templeton, Trinity LU
- supervisor
- organization
- course
- MVKM05 20241
- year
- 2024
- type
- H2 - Master's Degree (Two Years)
- subject
- keywords
- Scramjet, Hydrogen Reaction Mechanism, Computational Fluid Dynamics (CFD), Large Eddy Simulations (LES), Supersonic Combustion
- report number
- ISRN LUTMDN/TMHP-24/5603-SE
- ISSN
- 0282-1990
- language
- English
- id
- 9177342
- date added to LUP
- 2024-12-09 10:47:14
- date last changed
- 2024-12-09 10:47:14
@misc{9177342,
abstract = {{The scramjet engine is an air-breathing engine that can be used to travel at supersonic speeds. Research is being done into how these engines can be used as reusable launch vehicles for space travel, missile propulsion, and many hope one day scramjets can be used for commercial flight. Scramjets are highly beneficial in the sense that hydrogen is the primary fuel and that manufacturing is simple compared to other types of engines due to the lack of moving parts. The prospect of supersonic flight that doesn’t have large CO2 emissions is very exciting, but it is not without challenges. The thermal and structural load on both the engine and aircraft presents a heavy challenge in making scramjets viable, flight and combustion occur at supersonic speeds which requires solutions for removing heat and using materials that can withstand such extreme temperatures. The residence time in the combustor for a scramjet is on the order of milliseconds which presents another challenge in ensuring good mixing and achieving combustion in a non-premixed flame environment. Understanding the combustion physics is key to optimizing these engines from both a mixing and combustion standpoint as well as thermal load management. The purpose of this study was to assess which hydrogen combustion reaction mechanism represents diffusion flame supersonic hydrogen combustion most accurately. Additionally determining important features for modeling supersonic diffusion flame was a secondary purpose of this study. Using computational fluid dynamics simulations the assessment of design considerations and the reaction mechanisms was made. It was found that boundary layer development and turbulence at the inlet were very important factors in modeling the case. For problems of this type the cross-over temperature region is an important consideration, mechanisms that have multiple progression paths depending on the temperature are favorable. The Baurle mechanism did not include HO2 and H2O2 chemistry which are vital radicals for combustion below the cross-over temperature. Validation against the benchmarking case was not achieved so making conclusions is difficult. Future work would include validating the simulation against experiments and comparing more than five mechanisms.}},
author = {{Templeton, Trinity}},
issn = {{0282-1990}},
language = {{eng}},
note = {{Student Paper}},
title = {{Evaluation of hydrogen combustion reaction mechanisms in large eddy simulations for supersonic hydrogen combustion}},
year = {{2024}},
}