Periodic Reporting for period 1 - PlasNH3 (Developing Plasma-assisted ammonia technology for decarbonisation of power production)
Période du rapport: 2021-07-27 au 2023-07-26
Ammonia is known as the low-hanging fruit for decarbonising combustion. Unfortunately, the inherent challenge lies in its limited reactivity, which impedes its effective utilisation as a carbon-free fuel. This project, for the first time, introduced an innovative approach to boost ammonia’s reactivity by utilising nanosecond plasma discharges. The adoption of this technique with industrial sectors holds the potential to significantly diminish carbon footprint and greenhouse gas emissions. The overall objectives of this project are encompassed as follows:
Scientific objectives:
1- Develop a new kinetic mechanism by analysing the existing kinetic mechanisms of plasma-assisted combustion, and integrating them into existing ammonia combustion mechanisms.
2- Investigate the effects of plasma on the fundamental characteristics of ammonia flames by employing the developed kinetic mechanism.
3- Observe the effects of plasma on the stabilization and emission behaviour of ammonia/air-premixed flames based on a series of physical experimentations using a novel swirl burner test rig.
4- Improve understanding of the non-linear and multiscale plasma-flame-turbulence interactions by performing unsteady numerical simulations, to optimise the burner design based on the simulation results.
Training objectives:
1- Develop new knowledge and skills in kinetic mechanisms.
2- Develop skills in advanced numerical simulation techniques.
3- Develop skills in physical experimentation.
4- Enhance supervision and interdisciplinary knowledge-transferring skills.
5- Enhance organization and management skills.
6- Enhance academic communication skills.
7- Develop and extend the knowledge and skills obtained in “core skills” to other applications.
Scientific objectives:
1- Develop a new kinetic mechanism by analysing the existing kinetic mechanisms of plasma-assisted combustion, and integrating them into existing ammonia combustion mechanisms.
2- Investigate the effects of plasma on the fundamental characteristics of ammonia flames by employing the developed kinetic mechanism.
3- Observe the effects of plasma on the stabilization and emission behaviour of ammonia/air-premixed flames based on a series of physical experimentations using a novel swirl burner test rig.
4- Improve understanding of the non-linear and multiscale plasma-flame-turbulence interactions by performing unsteady numerical simulations, to optimise the burner design based on the simulation results.
Training objectives:
1- Develop new knowledge and skills in kinetic mechanisms.
2- Develop skills in advanced numerical simulation techniques.
3- Develop skills in physical experimentation.
4- Enhance supervision and interdisciplinary knowledge-transferring skills.
5- Enhance organization and management skills.
6- Enhance academic communication skills.
7- Develop and extend the knowledge and skills obtained in “core skills” to other applications.
The tasks and achievements accomplished during the fellowship in each WP are summarized as follows.
WP1: Development of the kinetic mechanism.
The researcher developed a kinetic mechanism for plasma-assisted ammonia combustion by taking the following tasks. Task 1: Ammonia mechanism improvement and validation. In this initial task, the researcher conducted a thorough evaluation of previously developed chemical mechanisms for ammonia combustion. The goal was to identify the most accurate mechanism capable of predicting the key characteristics of ammonia combustion including ignition delay time, flame speed, flame thickness, and pollutant emissions. Task 2: Combination of the thermal ammonia model with model for plasma process. Following the validation of the selected combustion mechanism against existing experimental data in the literature, the researchers developed a plasma mechanism for NH3/H2/N2/O2/He mixtures. Subsequently, this newly created plasma mechanism was combined with a combustion mechanism for the first time. Task 3: Mechanism reduction. In the final task, the researcher developed a reduced mechanism suitable for implementation in CFD codes. This was accomplished through the implementation of the directed relation graph with error propagation model, ensuring a more computationally efficient and accurate mechanism. The researcher was unable to undergo the secondment to Lund University due to travel restrictions that were in place during the COVID19 outbreak. In response, the researcher proactively acquired the necessary knowledge from the available resources to self-train for this WP.
WP2: Fundamental characteristics of premixed plasma-assisted ammonia flames.
In this WP, first, the researcher developed a numerical code combining Cantera, a high-order open-source chemical software with ZDPlaskin, an open-source software to model plasma chemistry. This code was then used to study plasma-assisted ammonia combustion through two tasks. Task 1: Code evaluation. The developed code was rigorously validated against previously obtained experimental data for plasma-assisted methane-air flames as a benchmark. Task 2: Generating a comprehensive database. In the second task, the researcher created an extensive database encompassed a wide array of plasma-assisted ammonia flame characteristics under various operating conditions and plasma settings. These characteristics included flame speed, flame thickness, extinction strain rate, flammability limits, and pollutant emissions.
WP3: Novel swirl burner experiments.
The researcher was unable to proceed with this WP and the associated secondment due to an unforeseen delay in the delivery of the required plasma generator to Cardiff University.
WP4: Large-eddy simulations (LES) of plasma/ammonia flames in the swirl burner
Relying on LES to investigate complex fluid flows like plasma-assisted ammonia combustion requires extensive validation of LES results against experimental data. Unfortunately, the cancellation of WP3 and the lack of experimental data compelled the researcher to adopt his approach within this WP. As a result, instead of using LES, direct numerical simulations (DNS) were used to study flame-plasma-turbulence interactions. DNS offers the most precise predictions of fluid flows where there is no need for specific validations, as it captures all turbulent scales within the simulations. However, DNS is a computationally intensive approach. Considering such limitations, the researcher shifted his focus from a swirl burner to investigating freely propagating turbulent flames in ammonia/air mixtures stimulated by plasma discharges. These adjustments, while demanding and resource-intensive, have yielded valuable insights into fundamental aspects of plasma-assisted ammonia combustion that were previously unexplored.
The main findings of the project in WP1 and 2 have been published in the top flag journals of the combustion field, namely “Combustion and Flame” and “Fuel”. Additionally, the researcher is currently preparing two papers to present the key research findings from WP4.
WP1: Development of the kinetic mechanism.
The researcher developed a kinetic mechanism for plasma-assisted ammonia combustion by taking the following tasks. Task 1: Ammonia mechanism improvement and validation. In this initial task, the researcher conducted a thorough evaluation of previously developed chemical mechanisms for ammonia combustion. The goal was to identify the most accurate mechanism capable of predicting the key characteristics of ammonia combustion including ignition delay time, flame speed, flame thickness, and pollutant emissions. Task 2: Combination of the thermal ammonia model with model for plasma process. Following the validation of the selected combustion mechanism against existing experimental data in the literature, the researchers developed a plasma mechanism for NH3/H2/N2/O2/He mixtures. Subsequently, this newly created plasma mechanism was combined with a combustion mechanism for the first time. Task 3: Mechanism reduction. In the final task, the researcher developed a reduced mechanism suitable for implementation in CFD codes. This was accomplished through the implementation of the directed relation graph with error propagation model, ensuring a more computationally efficient and accurate mechanism. The researcher was unable to undergo the secondment to Lund University due to travel restrictions that were in place during the COVID19 outbreak. In response, the researcher proactively acquired the necessary knowledge from the available resources to self-train for this WP.
WP2: Fundamental characteristics of premixed plasma-assisted ammonia flames.
In this WP, first, the researcher developed a numerical code combining Cantera, a high-order open-source chemical software with ZDPlaskin, an open-source software to model plasma chemistry. This code was then used to study plasma-assisted ammonia combustion through two tasks. Task 1: Code evaluation. The developed code was rigorously validated against previously obtained experimental data for plasma-assisted methane-air flames as a benchmark. Task 2: Generating a comprehensive database. In the second task, the researcher created an extensive database encompassed a wide array of plasma-assisted ammonia flame characteristics under various operating conditions and plasma settings. These characteristics included flame speed, flame thickness, extinction strain rate, flammability limits, and pollutant emissions.
WP3: Novel swirl burner experiments.
The researcher was unable to proceed with this WP and the associated secondment due to an unforeseen delay in the delivery of the required plasma generator to Cardiff University.
WP4: Large-eddy simulations (LES) of plasma/ammonia flames in the swirl burner
Relying on LES to investigate complex fluid flows like plasma-assisted ammonia combustion requires extensive validation of LES results against experimental data. Unfortunately, the cancellation of WP3 and the lack of experimental data compelled the researcher to adopt his approach within this WP. As a result, instead of using LES, direct numerical simulations (DNS) were used to study flame-plasma-turbulence interactions. DNS offers the most precise predictions of fluid flows where there is no need for specific validations, as it captures all turbulent scales within the simulations. However, DNS is a computationally intensive approach. Considering such limitations, the researcher shifted his focus from a swirl burner to investigating freely propagating turbulent flames in ammonia/air mixtures stimulated by plasma discharges. These adjustments, while demanding and resource-intensive, have yielded valuable insights into fundamental aspects of plasma-assisted ammonia combustion that were previously unexplored.
The main findings of the project in WP1 and 2 have been published in the top flag journals of the combustion field, namely “Combustion and Flame” and “Fuel”. Additionally, the researcher is currently preparing two papers to present the key research findings from WP4.
This project introduced a novel method to stably and efficiently burn low-reactive carbon-free fuels such as ammonia, aligning closely with European policy objectives and strategies aimed at reducing carbon footprint and tackling the pressing issues of climate change. This technique has the potential to introduce new markets and can be effectively integrated into a broad range of industries, spanning from power generation to iron making, thereby making substantial contributions to sustainability efforts.
Moreover, this project provided the researcher with cutting-edge knowledge and comprehensive training in a multidisciplinary topic in clean combustion: plasma-assisted carbon-free combustion. Throughout the course of this project, the researcher improved his supervision and leadership skills by supervising two MSc students working on industrial decarburization. Furthermore, the researcher enhanced his organizational skills by conducting group and individual meetings, contributing to proposal developments, and effectively managing the financial aspects of the project. PlasNH3 project also helped the researcher to enhance his academic communication and writing skills, through active participation in public engagements, attendance at conferences, and presentation of research papers in reputable journals. The acquisition of the aforementioned knowledge and skills has positioned the researcher as an internationally-leading scientist working on plasma-assisted ammonia combustion. It is expected that the researcher will secure a permanent academic position in the very near future.
Moreover, this project provided the researcher with cutting-edge knowledge and comprehensive training in a multidisciplinary topic in clean combustion: plasma-assisted carbon-free combustion. Throughout the course of this project, the researcher improved his supervision and leadership skills by supervising two MSc students working on industrial decarburization. Furthermore, the researcher enhanced his organizational skills by conducting group and individual meetings, contributing to proposal developments, and effectively managing the financial aspects of the project. PlasNH3 project also helped the researcher to enhance his academic communication and writing skills, through active participation in public engagements, attendance at conferences, and presentation of research papers in reputable journals. The acquisition of the aforementioned knowledge and skills has positioned the researcher as an internationally-leading scientist working on plasma-assisted ammonia combustion. It is expected that the researcher will secure a permanent academic position in the very near future.