Updated on 2025/06/30

Information

 

写真a

 
OKAFOR CHIJIOKE EKENECHUKWU
 
Organization
Faculty of Engineering Department of Mechanical Engineering Associate Professor
School of Engineering （Concurrent）
Graduate School of Engineering Department of Mechanical Engineering（Concurrent）
Title
Associate Professor
Contact information
メールアドレス
Tel
0928023147
Homepage
External link

Degree

  • Doctor of Engineering （Kyushu University、Japan） （ 2015.9 Kyushu University ）

Research History

  • Kyushu University  Associate Professor 

    2022.1 - Present

  • National Institute of Advanced Industrial Science and Technology  Visiting Researcher 

    2022.1 - Present

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  • National Institute of Advanced Industrial Science and Technology  Researcher 

    2019.4 - 2021.12

  • Tohoku University  Postdoc Researcher 

    2015.10 - 2019.3

Education

  • Kyushu University   Graduate School of Engineering, Department of Mechanical Engineering  

    2012.10 - 2015.9

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    Country：Japan

  • Kyushu University   Graduate School of Engineering, Department of Mechanical Engineering  

    2010.10 - 2012.9

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    Country：Japan

  • University of Nigeria, Nsukka   Department of Mechanical Engineering  

    2001.10 - 2008.9

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    Country：Nigeria

Research Interests・Research Keywords

  • Research theme： Development of a data-driven model for liquid ammonia spray

    Keyword： Spray, Liquid Ammonia, Machine learning

    Research period： 2024.3 - 2027.3

  • Research theme： Investigation of a novel strategy for emissions control in swirl combustors fueled with ammonia-hydrogen mixtures

    Keyword： Combustion,　hydrogen,　Ammonia, Flame stabilization,　Gas turbine, emissions

    Research period： 2023.4 - 2025.3

  • Research theme： Laminar and turbulent buring velocities of oxygen enriched ammonia flames.

    Keyword： Ammonia, oxygen-enriched combustion, burning velocity,

    Research period： 2022.4 - 2023.3

  • Research theme： Research and development of an ammonia-natural gas cofired furnace burner

    Keyword： Industrial furnace, Burner, Ammonia, Natural gas

    Research period： 2022.4

  • Research theme： Research and development of liquid ammonia spray combustion technology for gas turbines

    Keyword： Spray combustion, Liquid Ammonia, Flame stabilization, Gas turbine, emissions

    Research period： 2019.4 - 2025.9

  • Research theme： Development and validation of chemical kinetics for ammonia combustion

    Keyword： Combustion, Ammonia, Chemical Kinetics, Laminar burning velocity

    Research period： 2015.10 - 2019.3

  • Research theme： Ammonia Direction Combustion in a Swirl Combustor

    Keyword： Combustion,　Ammonia, Flame stabilization,　Gas turbine, Swirl burner, emissions

    Research period： 2015.10 - 2019.3

  • Research theme： Study of the effects of pressure and hydrogen concentration on the laminar and turbulent burning velocity of outwardly propagating CH4-H2-air flames.

    Keyword： Combustion, Hydrogen, Methane, flames speeds, burning velocity, flame stretch, Markstein length, Markstein number, Lewis number

    Research period： 2010.10 - 2015.9

Awards

  • 2023 Best Paper Award

    2023.11   Combustion Society of Japan  

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    In this study, we investigated the effect of pressure on the characteristics of spherically propagating ammonia-methane-air premixed flames. A reduced reaction mechanism was developed based on the detailed reaction model developed in our previous study and optimized for conditions up to 0.5 MPa. At the time of this study, ammonia was beginning to attract attention again as a fuel, and there was a need to develop chemical reaction models for co-combustion of ammonia and hydrocarbons, however there were few measured data on ammonia flame properties under high pressure, which was necessary for optimization of the reaction models. In this study, the laminar burning velocity and Markstein length of ammonia-methane-air premixed flames containing more than 5% ammonia were measured for the first time under high pressure. In this article we present an extensive set of measured data obtained using a constant volume combustion chamber. These data and speciation data measured by other researchers were used to optimize the reduced reaction model in this study.
    The paper reveals the effect of pressure on the response of the laminar burning velocity to flame stretch rate. The Lewis number is insensitive to changes in pressure, however it was clarified that an increase in pressure enhances thermos-diffusive effects through the influence of an increase in the Zel'dovich number. On the other hand, it was shown that an accurate prediction of the laminar burning velocity and NO concentrations in ammonia flames through numerical simulations strongly depends on the prediction accuracy of O, H, and OH radical concentrations. The reduced reaction model has been optimized to accurately predict the laminar burning velocity and concentrations of OH, NO, and NH for ammonia-air and ammonia-methane-air flames over a wide range of conditions.

  • ASPACC 2021 Young Investigator Award

    2021.12   Asia-Pacific section of the Combustion Institute  

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    Award type：Award from international society, conference, symposium, etc. 

  • 2021 Incentive Award

    2021.11   Combustion Society of Japan  

  • 2020 Best Paper Award

    2020.12   Combustion Society of Japan  

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    Low-NOx NH3-air combustion power generation technology was developed by using a 50-kWe class micro gas-turbine system at the National Institute of Advanced Industrial Science and Technology (AIST), Japan, for the first time. Based on the global demand for carbon-free power generation as well as recent advances involving gas-turbine technologies, such as heat-regenerative cycles, rapid fuel mixing using strong swirling flows, and two-stage combustion with equivalence ratio control, we developed a low-NOx NH3-air non-premixed combustor for the gas-turbine system. Considering a previously performed numerical analysis, which proved that the NO reduction level depends on the equivalence ratio of the primary combustion zone in a NH3-air swirl burner, an experimental study using a combustor test rig was carried out. Results showed that eliminating air flow through primary dilution holes moves the point of the lowest NO emissions to the lesser fuel flow rate. Based on findings derived by using a test rig, a rich-lean low NOx combustor was newly manufactured for actual gas-turbine operations. As a result, the NH3 single fueled low-NOx combustion gas-turbine power generation using the rich-lean combustion concept succeeded over a wide range of power and rotational speeds, i.e., below 10–40 kWe and 75,000–80,000 rpm, respectively. The NO emissions were reduced to 337 ppm (16% O2), which was about one-third of that of the base system. Simultaneously, unburnt NH3 was reduced significantly, especially at the low electrical power output, which was indicative of the wider operating range with high combustion efficiency. In addition, N2O emissions, which have a large Global Warming Potential (GWP) of 298, were reduced significantly, thus demonstrating the potential of NH3 gas-turbine power generation with low environmental impacts.

  • 2019 Best Paper Award

    2019.11   Combustion Society of Japan  

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    This paper focuses on the potential use of ammonia as a carbon-free fuel, and covers recent advances in the development of ammonia combustion technology and its underlying chemistry. Fulfilling the COP21 Paris Agreement requires the de-carbonization of energy generation, through utilization of carbon-neutral and overall carbon-free fuels produced from renewable sources. Hydrogen is one of such fuels, which is a potential energy carrier for reducing greenhouse-gas emissions. However, its shipment for long distances and storage for long times present challenges. Ammonia on the other hand, comprises 17.8% of hydrogen by mass and can be produced from renewable hydrogen and nitrogen separated from air. Furthermore, thermal properties of ammonia are similar to those of propane in terms of boiling temperature and condensation pressure, making it attractive as a hydrogen and energy carrier. Ammonia has been produced and utilized for the past 100 years as a fertilizer, chemical raw material, and refrigerant. Ammonia can be used as a fuel but there are several challenges in ammonia combustion, such as low flammability, high NOx emission, and low radiation intensity. Overcoming these challenges requires further research into ammonia flame dynamics and chemistry. This paper discusses recent successful applications of ammonia fuel, in gas turbines, co-fired with pulverize coal, and in industrial furnaces. These applications have been implemented under the Japanese ‘Cross-ministerial Strategic Innovation Promotion Program (SIP): Energy Carriers’. In addition, fundamental aspects of ammonia combustion are discussed including characteristics of laminar premixed flames, counterflow twin-flames, and turbulent premixed flames stabilized by a nozzle burner at high pressure. Furthermore, this paper discusses details of the chemistry of ammonia combustion related to NOx production, processes for reducing NOx, and validation of several ammonia oxidation kinetics models. Finally, LES results for a gas-turbine-like swirl-burner are presented, for the purpose of developing low-NOx single-fuelled ammonia gas turbine combustors.

  • Best Poster and Presentation Award

    2014.9   Kyushu University/KAIST   Best Poster and Presentation Award

  • Excellence in Oral Presentation

    2013.10   Society of Automotive Engineers. International   Excellence in Oral Presentation

  • Best Science Student Award, University of Nigeria Secondary School Nsukka

    2001.9   University of Nigeria Secondary School, Nsukka   Best Science Student Award, University of Nigeria Secondary School Nsukka

  • Best Graduating Student Award, University of Nigeria Secondary School Nsukka

    2001.9   University of Nigeria Secondary School, Nsukka   Best Graduating Student Award, University of Nigeria Secondary School Nsukka

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Papers

  • Chemical kinetics of Lean − Rich − Lean fuel-air staged NH3/H2-air combustion for emission control Reviewed International coauthorship

    Y. Vijrumbana, M. Srinivasarao, E.C. Okafor, B.R. Giri, V. M. Reddy

    Fuel   383   133813   2025.3

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    Language：English   Publishing type：Research paper (scientific journal)  

    DOI： https://doi.org/10.1016/j.fuel.2024.133813

    DOI： https://doi.org/10.1016/j.fuel.2024.133813

    Other Link： https://doi.org/10.1016/j.fuel.2024.133813

  • Flame stabilization and emission characteristics of ammonia combustion in lab-scale gas turbine combustors: Recent progress and prospects Reviewed International coauthorship International journal

    Meng Zhang, Xutao Wei, Zhenhua An, Ekenechukwu C. Okafor, Thibault F. Guiberti, Jinhua Wang, Zuohua Huang

    Progress in Energy and Combustion Science   106   101193   2025.1

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    Language：English   Publishing type：Research paper (scientific journal)  

    DOI： https://doi.org/10.1016/j.pecs.2024.101193

    Other Link： https://doi.org/10.1016/j.pecs.2024.101193

  • Achieving High Flame Stability with Low NO And Zero N2O And NH3 Emissions During Liquid Ammonia Spray Combustion with Gas Turbine Combustors Reviewed International journal

    Okafor E.C., Kurata O., Yamashita H., Iki N., Inoue T., Jo H., Shimura M., Tsujimura T., Hayakawa A., Kobayashi H.

    Proceedings of the Combustion Institute   40   105340   2024.11

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    Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)  

    Liquid ammonia spray direct injection is more desirable than gaseous ammonia injection in large scale gas turbine combustors because it enables a larger volumetric energy density and allows a reduction in cost and size of the fuel supply system. However, previous studies have shown that the large evaporative cooling effects of liquid ammonia droplets vaporization impair flame stabilization, and inhibit efficient control of emissions such as NO, N2O and unburned fuels. This article reports the development and testing of a novel two-stage gas turbine combustor for pure liquid ammonia spray, which achieves approximately zero N2O and unburned fuel emissions with NO emissions as low as 282 ppmv (@16% O2) in a 50 kW micro gas turbine combustor test rig. The combustor design focused on optimization of the secondary injection holes to prevent the dilution of the primary zone (PZ) by air injected into the secondary zone; improving mixture formation using a multi-nozzle twin-fluid atomizer; and elongation of the combustor length to allow sufficient fluid residence time for N2O reduction as well as droplets vaporization and combustion. It was found that the mitigation of PZ dilution resulted in a significant increase in the combustion temperature thereby encouraging efficient combustion of the liquid droplets. On the other hand, the multi-nozzle twin fluid atomizer resulted in a more uniform combustor wall temperature, a more efficient combustion and lower NOx emissions than a single-nozzle pressure swirl atomizer. It is considered that the multi-nozzle injector allowed for an improved droplets dispersion, which is necessary to mitigate large local heat extraction from the flame. These features of the combustor enabled a substantial improvement in liquid ammonia spray flame stability and a better simultaneous control of NO, N2O and unburned fuel emissions never reported before

    DOI： https://doi.org/10.1016/j.proci.2024.105340

    Other Link： https://doi.org/10.1016/j.proci.2024.105340

  • Enhancement of liquid ammonia combustion by a twin-fluid atomizer Reviewed

    Kurata O., Okafor E.C., Yamashita H., Inoue T., Tsujimura T., Iki N., Hayakawa A., Kobayashi H.

    International Journal of Gas Turbine, Propulsion and Power Systems   15 ( 4 )   2024.7

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    Language：English   Publishing type：Research paper (scientific journal)   Publisher：ASME International  

    The effects of atomizer type on flame stabilization and emissions from a liquid ammonia gas-turbine combustor were studied to explore the impact of enhanced fuel-air mixing. A twin-fluid atomizer is expected to enhance the mixing of atomized fuel and air, which may decrease the amount of unburnt fuel at the combustor outlet owing to improved combustion efficiency. Liquid ammonia was used as fuel, and the combustor pressure was 0.25 MPa abs. A low combustor pressure tends to encourage the partial vaporization of liquid ammonia in the mixing chamber of the twin-fluid atomizer. When the pressure of the mixing chamber was below the design value, a lower pressure, which may encourage flash boiling and hence rapid atomization, enabled a decrease in the emission of unburnt NH3 compared with that of the pressure-swirl atomizer. However, higher levels of unburned ammonia emissions were observed when the mixing chamber pressure reached the design value, suggesting that flash boiling, which promotes atomization, may enhance combustion efficiency.

    DOI： https://doi.org/10.38036/jgpp.15.4_v15n4tp02

  • Combustion and Emission Characteristics of an Ammonia Microgas Turbine Combustor With a Twin-Fluid Atomizer Reviewed International journal

    Hyun Jo, Masayasu Shimura, Osamu Kurata, Ekenechukwu Chijioke Okafor, Hirofumi Yamashita, Takahiro Inoue, Taku Tsujimura, Norihiko Iki, Yong Fan

    Journal of Engineering for Gas Turbines and Power   146 ( 11 )   2024.6   （ ISSN:0742-4795 eISSN:1528-8919 ）

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    Language：English   Publishing type：Research paper (scientific journal)   Publisher：ASME International  

    Abstract

    In this study, combustion and emission characteristics in the test rig of microgas turbine with liquid ammonia fuel injection using the twin-fluid atomizers (TFAs) are investigated and compared with the previous result using the pressure-swirl atomizer (PSA). The combustion situation was simulated using the test rig of microgas turbine, and experiments were conducted by controlling the ratio of ammonia and methane to create a pure ammonia combustion situation. The TFA has spray cone angles of 60 deg, 90 deg, and 120 deg, and its combustion characteristics were analyzed and compared with the PSA. At 60 deg TFA, the blow-off of ammonia flame occurred before the pure ammonia combustion stage, and the flame blow-off occurred after the pure ammonia combustion at the 90 deg and 120 deg TFAs. This means that the blow-off of ammonia flame easily occurred when the spray cone angle of the atomizer is small, because the recirculation flow to the upstream of ammonia flame is weak. In addition, the 90 deg and 120 deg TFAs showed significantly reduced emissions of NO, N2O, and unburned NH3 compared to the 60 deg TFA and PSA. This can be concluded that a large spray cone angle forms a strong recirculation flow within the combustor, and emissions are reduced because the high-temperature zone sufficiently stays in the primary combustion zone.

    DOI： 10.1115/1.4065715

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  • Visualization of liquid ammonia spray using 2p-SLIPI and comparison of liquid ammonia spray and gaseous ammonia combustion in a swirl combustor at atmospheric pressure Reviewed International journal

    Hirofumi Yamashita, Akihiro Hayakawa, Kohei Oku, Sophie Colson, Gauthier Reibel, Yi-rong Chen, K. D. Kunkuma A. Somarathne, Ekenechukwu C. Okafor, Taku Tsujimura, Shintaro Ito, Masahiro Uchida, Taku Kudo, Hideaki Kobayashi

    Fuel   371   131833   2024.5

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    Language：English   Publishing type：Research paper (scientific journal)  

    DOI： https://doi.org/10.1016/j.fuel.2024.131833

    Other Link： https://www.sciencedirect.com/science/article/pii/S0016236124009815

  • Optimum primary equivalence ratio for rich-lean two-stage combustion of non-premixed ammonia/methane/air and ammonia/hydrogen/air flames in a swirling flow Reviewed International journal

    Hirofumi Yamashita, Akihiro Hayakawa, Ekenechukwu C. Okafor, Sophie Colson, K. D. Kunkuma A. Somarathne, Taku Tsujimura, Shintaro Ito, Masahiro Uchida, Taku Kudo, Hideaki Kobayashi

    Fuel   368   131598   2024.4

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    Language：English   Publishing type：Research paper (scientific journal)  

    DOI： https://doi.org/10.1016/j.fuel.2024.131598

    Other Link： https://www.sciencedirect.com/science/article/pii/S0016236124007464

  • Towards the development of liquid ammonia/air spray combustion in a gas turbine-like combustor at moderately high pressure Reviewed International journal

    Somarathne K.D.K.A, Yamashita H., Colson S., Oku K., Honda K., Okafor E.C., Hayakawa A., Kudo T., Kobayashi H.

    Applications in Energy and Combustion Science   16   100215   2023.10

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    Language：English   Publishing type：Research paper (scientific journal)  

    DOI： https://doi.org/10.1016/j.jaecs.2023.100215

  • Numerical Investigation of the Diluting Effects of Secondary Air on the Primary Combustion Zone of Two-Stage Rich-Lean Ammonia Gas Turbine Combustors Reviewed International journal

    Okafor E.C., Yamashita H., Kurata O., Inoue T., Tsujimura T., Iki N., Hayakawa A., Ito S., Uchida M., Kobayashi H.

    Proceedings of the 14th Asia-Pacific Conference on Combustion   2023.5

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    Authorship：Lead author   Language：English   Publishing type：Research paper (international conference proceedings)  

  • The Impact of Soret Diffusion on the Product Gas Characteristics of Premixed Laminar Ammonia/Hydrogen/Air Flames Stabilised in a Stagnation Flow Reviewed International coauthorship International journal

    M. Kovaleva, G.J. Gotama, A. Hayakawa, E.C. Okafor, S. Colson, A. Crayford, T. Kudo, H. Kobayashi

    Proceedings of the 14th Asia-Pacific Conference on Combustion   2023.5

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    Language：English   Publishing type：Research paper (international conference proceedings)  

  • Experimental and numerical study of product gas and N2O emission characteristics of ammonia/hydrogen/air premixed laminar flames stabilized in a stagnation flow Reviewed International coauthorship International journal

    Akihiro Hayakawa, Masao Hayashia, Marina Kovaleva, Gabriel J.Gotama, Ekenechukwu C.Okafor, SophieColson, Syed Mashruk, Agustin Valera-Medina, Taku Kudo, Hideaki Kobayashi

    Proceedings of the Combustion Institute   39   1625 - 1633   2022.12

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    Language：English   Publishing type：Research paper (scientific journal)  

    DOI： https://doi.org/10.1016/j.proci.2022.08.124

  • Nitrogen oxide emissions analyses in ammonia/hydrogen/air premixed swirling flames Reviewed International coauthorship International journal

    Syed Mashruk; Marina Kovaleva; Ali Alnasif; Cheng Tung Chong; Akihiro Hayakawa; @Ekenechukwu C.Okafor; AgustinValera-Medina

    Energy   260   125183   2022.8

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    Language：English   Publishing type：Research paper (scientific journal)  

    DOI： https://doi.org/10.1016/j.energy.2022.125183

  • Evolution of N2O production at lean combustion condition in NH3/H2/air premixed swirling flames Reviewed International coauthorship International journal

    Mashruk S.; Okafor E.C.; Kovaleva M.; Alnasif A.; Pugh D.; Hayakawa A.; Valera-Medina A.

    Combustion and Flame   244   112299   2022.8

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    Language：English   Publishing type：Research paper (scientific journal)  

    DOI： https://doi.org/10.1016/j.combustflame.2022.112299

  • Numerical and experimental study of product gas characteristics in premixed ammonia/methane/air laminar flames stabilised in a stagnation flow Reviewed International coauthorship

    Marina Kovaleva, Akihiro Hayakawa, Sophie Colson, Ekenechukwu C. Okafor, Taku Kudo, Agustin Valera-Medina, Hideaki Kobayashi

    Fuel Communications   10   100054 - 100054   2022.3

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    Language：English   Publishing type：Research paper (scientific journal)  

    DOI： https://doi.org/10.1016/j.jfueco.2022.100054

  • Effects of initial mixture temperature and pressure on laminar burning velocity and Markstein length of ammonia/air premixed laminar flames Reviewed International journal

    Kanoshima R.; Hayakawa A.; Kudo T.; Okafor E.C.; Colson S.; Ichikawa A.; Kudo T.; Kobayashi H.

    FUEL   310 ( B )   - 122149   2022.2

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    Language：English   Publishing type：Research paper (scientific journal)  

    DOI： 10.1016/j.fuel.2021.122149

  • Measurement of the laminar burning velocity and kinetics study of the importance of the hydrogen recovery mechanism of ammonia/hydrogen/air premixed flames Reviewed International journal

    Gotama G.J.; Hayakawa A.; Okafor E.C.; Kanoshima R.; Hayashi M.; Kudo T.; Kobayashi H.

    COMBUSTION AND FLAME   236   - 111753   2022.2

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    Language：English   Publishing type：Research paper (scientific journal)  

    DOI： 10.1016/j.combustflame.2021.111753

  • Nitrogen Oxides as a By-product of Ammonia/Hydrogen Combustion Regimes Invited Reviewed International journal

    Mashruk S.; Kovaleva M.; Chong C.T.; Hayakawa A.; Okafor E.C.; Valera-Medina A.

    CHEMICAL ENGINEERING TRANSACTIONS   89   613 - 618   2021.12

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    Language：English   Publishing type：Research paper (scientific journal)  

    DOI： 10.3303/CET2189103

  • Optimum Equivalence Ratio for Low NO and Unburned NH3 Emissions in Gaseous Ammonia Flames Co-fired with Methane or Hydrogen in a Swirling Flow Reviewed International journal

    Yamashita H., Hayakawa A., Okafor E.C., Colson S., Somarathne K.D.K.A, Tsujimura T., Ito S., Uchida M., Kudo T., Kobayashi H.

    Proceedings of the 13th Asia-Pacific Conference on Combustion   2021.12

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    Language：English   Publishing type：Research paper (international conference proceedings)  

  • On Simultaneous Flame Enhancement and NOx Control in Liquid Ammonia Spray Combustion in a Micro Gas Turbine Combustor Reviewed International journal

    Okafor E.C., Kurata O., Yamashita H., Inoue T., Tsujimura T., Iki N., Hayakawa A., Ito S., Uchida M., Kobayashi H.

    Proceedings of the 13th Asia-Pacific Conference on Combustion   2021.11

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    Language：English   Publishing type：Research paper (international conference proceedings)  

  • Liquid Ammonia Spray Combustion and Emission Characteristics with Gaseous Hydrogen/air Co-firing Reviewed International journal

    Somarathne K.D.K.A, Yamashita H., Colson S., Okafor E.C., Hayakawa A., Kudo T., Kobayashi H.

    Proceedings of the 13th Asia-Pacific Conference on Combustion   2021.11

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    Language：English   Publishing type：Research paper (international conference proceedings)  

  • N2O Production Characteristics of Ammonia/Hydrogen/Air Premixed Laminar Flames Stabilized in Stagnation Flows at Lean Conditions Reviewed International journal

    Hayakawa A., Hayashi M., Gotama G.J., Kovaleva M., Okafor E.C., Colson S., Kudo T., Mashruk S., Valera-Medina A., Kobayashi H.,

    Proceedings of the 13th Asia-Pacific Conference on Combustion   2021.11

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    Language：English   Publishing type：Research paper (international conference proceedings)  

  • Liquid Ammonia Spray Combustion in Two-Stage Micro Gas Turbine Combustors at 0.25 MPa; Relevance of Combustion Enhancement to Flame Stability and NOx Control Reviewed International journal

    Okafor E.C.; Kurata O.; Yamashita H.; Inoue T.; Tsujimura T.; Iki N.; Hayakawa A.; Ito S.; Uchida M.; Kobayashi H.

    APPLICATIONS IN ENERGY AND COMBUSTION SCIENCE   7   - 100038   2021.9

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    Language：English   Publishing type：Research paper (scientific journal)  

    DOI： 10.1016/j.jaecs.2021.100038

  • Start-up process of 50kW-class gas turbine firing ammonia gas Invited Reviewed International journal

    Kurata, O., Iki, N., Fan, Y., Matsunuma, T., Inoue, T., Tsujimura, T., Furutani, H., Kawano, M., Arai, K., Okafor, E. C., Hayakawa, A., Kobayashi, H

    Proceedings of ASME Turbo Expo 2021:Turbomachinery Technical Conference and Exposition   2021.6

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    Language：English   Publishing type：Research paper (scientific journal)  

    DOI： 10.1115/GT2021-59448

  • Influence of wall heat loss on the emission characteristics of premixed ammonia-air swirling flames interacting with the combustor wall Invited Reviewed International journal

    Okafor Ekenechukwu C .; Tsukamoto Masaaki; Hayakawa Akihiro; Somarathne KD Kunkuma A .; Kudo Taku; Tsujimura Taku; Kobayashi Hideaki

    PROCEEDINGS OF THE COMBUSTION INSTITUTE   38 ( 4 )   5139 - 5146   2021.1

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    Language：English   Publishing type：Research paper (scientific journal)  

    DOI： 10.1016/j.proci.2020.06.142

  • Effects of OH concentration and temperature on NO emission characteristics of turbulent non-premixed CH4/NH3/air flames in a two-stage gas turbine like combustor at high pressure Invited Reviewed International journal

    Somarathne Kapuruge Don Kunkuma Amila; Okafor Ekenechukwu C .; Sugawara Daiki; Hayakawa Akihiro; Kobayashi Hideaki

    PROCEEDINGS OF THE COMBUSTION INSTITUTE   38 ( 4 )   5163 - 5170   2021.1

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    Language：English   Publishing type：Research paper (scientific journal)  

    DOI： 10.1016/j.proci.2020.06.276

  • Experimental and numerical study of product gas characteristics of ammonia/air premixed laminar flames stabilized in a stagnation flow Invited Reviewed International journal

    Hayakawa Akihiro; Hirano Yuta; Okafor Ekenechukwu C.; Yamashita Hirofumi; Kudo Taku; Kobayashi Hideaki

    PROCEEDINGS OF THE COMBUSTION INSTITUTE   38 ( 2 )   2409 - 2417   2021.1

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    Language：English   Publishing type：Research paper (scientific journal)  

    DOI： 10.1016/j.proci.2020.07.030

  • Flame stability and emissions characteristics of liquid ammonia spray co-fired with methane in a single stage swirl combustor Reviewed

    Ekenechukwu C. Okafor, Hirofumi Yamashita, Akihiro Hayakawa, K. D. Kunkuma A. Somarathne, Taku Kudo, Taku Tsujimura, Masahiro Uchida, Shintaro Ito, Hideaki Kobayashi

    FUEL   287   2020.10

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    Language：English   Publishing type：Research paper (scientific journal)  

    DOI： 10.1016/j.fuel.2020.119433

  • Laminar Burning Velocity and Markstein Length of CH4/CO2/Air Premixed Flames at Various Equivalence Ratios and CO2 Concentrations Under Elevated Pressure Reviewed

    Willyanto Anggono, Akihiro Hayakawa, Ekenechukwu C. Okafor, Gabriel Jeremy Gotama, Stevan Wongso

    COMBUSTION SCIENCE AND TECHNOLOGY   2020.3

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    Language：English   Publishing type：Research paper (scientific journal)  

    DOI： 10.1080/00102202.2020.1737032

  • Control of NOx and other emissions in micro gas turbine combustors fuelled with mixtures of methane and ammonia Invited Reviewed International journal

    Okafor Ekenechukwu C .; Somarathne KD Kunkuma A .; Ratthanan Rattanasupapornsak; Hayakawa Akihiro; Kudo Taku; Kurata Osamu; Iki Norihiko; Tsujimura Taku; Furutani Hirohide; Kobayashi Hideaki

    COMBUSTION AND FLAME   211   406 - 416   2020.1

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    Language：English   Publishing type：Research paper (scientific journal)  

    DOI： 10.1016/j.combustflame.2019.10.012

  • Emission characteristics of turbulent non-premixed ammonia/air and methane/air swirl flames through a rich-lean combustor under various wall thermal boundary conditions at high pressure Invited Reviewed International journal

    Somarathne Kapuruge Don Kunkuma Amila; Okafor Ekenechukwu C.; Hayakawa Akihiro; Kudo Taku; Kurata Osamu; Iki Norihiko; Kobayashi Hideaki

    COMBUSTION AND FLAME   210   247 - 261   2019.12

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    Language：English   Publishing type：Research paper (scientific journal)  

    DOI： 10.1016/j.combustflame.2019.08.037

  • Product Gas Characteristics of Strain Stabilized Ammonia/air Premixed Laminar Flames Reviewed International journal

    Hayakawa, A. Hirano, Y., Okafor, E.C., Kudo, T., Kobayashi, H.

    Proceedings of the 12th Asia-Pacific Conference on Combustion   2019.7

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    Language：English   Publishing type：Research paper (international conference proceedings)  

  • On the control of NOx emission from a micro gas turbine combustor fueled with mixtures of methane and ammonia Reviewed International journal

    Okafor, E.C., Rattanasupapornsak, R., Somarathne, K.D.K.A., Hayakawa, A., Kudo, T., Kurata, O, Iki, N, Tsujimura, T., Kobayashi, H.

    Proceedings of the 12th Asia-Pacific Conference on Combustion   2019.7

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    Language：English   Publishing type：Research paper (international conference proceedings)  

  • Emission Characteristics of Turbulent Non-premixed CH4/NH3/air Swirl Flames through a Rich-Lean Gas Turbine-like Combustor at High Pressure Reviewed International journal

    Somarathne, K.D.K.A., Okafor, E.C., Hayakawa, A., Kobayashi, H.

    Proceedings of the 12th Asia-Pacific Conference on Combustion   2019.7

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    Language：English   Publishing type：Research paper (international conference proceedings)  

  • Measurement and modelling of the laminar burning velocity of methane-ammonia-air flames at high pressures using a reduced reaction mechanism Invited Reviewed International journal

    Okafor Ekenechukwu C.; Naito Yuji; Colson Sophie; Ichikawa Akinori; Kudo Taku; Hayakawa Akihiro; Kobayashi Hideaki

    COMBUSTION AND FLAME   204   162 - 175   2019.6

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    Language：English   Publishing type：Research paper (scientific journal)  

    DOI： 10.1016/j.combustflame.2019.03.008

  • Rich-lean combustor for a 50kW class micro gas turbine firing ammonia Reviewed International journal

    Iki, N., Kurata, O., Inoue, T., Matsunuma, T., Tsujimuira, T., Furutani, H., Kawano, M., Arai, K., Kobayashi, H., Hayakawa, A., Okafor, E. C.

    Proceedings of Global Power and Propulsion Society   2019.6

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    Language：English   Publishing type：Research paper (international conference proceedings)  

    Other Link： https://gpps.global/wp-content/uploads/2021/02/GPPS-BJ-2019_paper_74.pdf

  • Towards the development of an efficient low-NOx ammonia combustor for a micro gas turbine Invited Reviewed International journal

    Okafor Ekenechukwu C .; Somarathne KD Kunkuma A .; Hayakawa Akihiro; Kudo Taku; Kurata Osamu; Iki Norihiko; Kobayashi Hideaki

    PROCEEDINGS OF THE COMBUSTION INSTITUTE   37 ( 4 )   4597 - 4606   2019.1

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    Language：English   Publishing type：Research paper (scientific journal)  

    DOI： 10.1016/j.proci.2018.07.083

  • Development of a wide range-operable, rich-lean low-NOx combustor for NH3 fuel gas-turbine power generation Invited Reviewed International journal

    Kurata Osamu; Iki Norihiko; Inoue Takahiro; Matsunuma Takayuki; Tsujimura Taku; Furutani Hirohide; Kawano Masato; Arai Keisuke; Okafor Ekenechukwu Chijioke; Hayakawa Akihiro; Kobayashi Hideaki

    PROCEEDINGS OF THE COMBUSTION INSTITUTE   37 ( 4 )   4587 - 4595   2019.1

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    Language：English   Publishing type：Research paper (scientific journal)  

    DOI： 10.1016/j.proci.2018.09.012

  • Science and technology of ammonia combustion Invited Reviewed International journal

    Kobayashi Hideaki; Hayakawa Akihiro; Somarathne KD Kunkuma A .; Okafor Ekenechukwu C.

    PROCEEDINGS OF THE COMBUSTION INSTITUTE   37 ( 1 )   109 - 133   2019.1

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    Language：English   Publishing type：Research paper (scientific journal)  

    DOI： 10.1016/j.proci.2018.09.029

  • NOx reduction of a swirl combustor firing ammonia for a micro gas turbine Reviewed International journal

    Iki, N., Kurata, O., Inoue, T., Matsunuma, T., Tsujimuira, T., Furutani, H., Kobayashi, H., Hayakawa, A., Okafor, E. C.

    Proceedings of ASME Turbo Expo 2018: Turbomachinery Technical Conference and Exposition   2018.8

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    Language：English   Publishing type：Research paper (international conference proceedings)  

    DOI： 10.1115/GT2018-75993

  • Experimental and numerical study of the laminar burning velocity of CH4-NH3-air premixed flames Invited Reviewed International journal

    Okafor Ekenechukwu C .; Naito Yuji; Colson Sophie; Ichikawa Akinori; Kudo Taku; Hayakawa Akihiro; Kobayashi Hideaki

    COMBUSTION AND FLAME   187   185 - 198   2018.1

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    Language：English   Publishing type：Research paper (scientific journal)  

    DOI： 10.1016/j.combustflame.2017.09.002

  • Stabilization and emission characteristics of ammonia flames in a micro gas turbine combustor Reviewed International journal

    Okafor, E.C., Sakai, K., Akihiro, H., Kudo, T., Kurata, O, Iki, N, Kobayashi, H.

    Proceedings of the 11th Asia-Pacific Conference on Combustion   2017.12

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    Language：English   Publishing type：Research paper (international conference proceedings)  

  • Experimental and theoretical analysis of cellular instability in lean H-2-CH4-air flames at elevated pressures Invited Reviewed International journal

    Okafor Ekenechukwu C .; Nagano Yukihide; Kitagawa Toshiaki

    INTERNATIONAL JOURNAL OF HYDROGEN ENERGY   41 ( 15 )   6581 - 6592   2016.4

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    Language：English   Publishing type：Research paper (scientific journal)  

    DOI： 10.1016/j.ijhydene.2016.02.151

  • Turbulent Burning Velocities of Stoichiometric Hydrogen-Carbon Monoxide-Air Flames at Elevated Pressures Reviewed

    Ekenechukwu C. Okafor, Yosuke Fukuda, Yukihide Nagano, Toshiaki Kitagawa

    SAE Technical Papers   2014-October   2014.10

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    Language：English   Publishing type：Research paper (other academic)  

    DOI： 10.4271/2014-01-2701

  • Effects of hydrogen concentration on premixed laminar flames of hydrogen-methane-air Reviewed

    Ekenechukwu C. Okafor, Akihiro Hayakawa, Yukihide Nagano, Toshiaki Kitagawa

    INTERNATIONAL JOURNAL OF HYDROGEN ENERGY   39 ( 5 )   2409 - 2417   2014.2

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    Language：English   Publishing type：Research paper (scientific journal)  

    DOI： 10.1016/j.ijhydene.2013.11.128

  • Effects of hydrogen concentration on stoichiometric H2/CH4/Air premixed turbulent flames Reviewed International journal

    Okafor, E.C., Nagano, Y., Kitagawa T.

    SAE/KSAE Powertrain Fuel and Lubricants Meeting   2013.10

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    Language：English   Publishing type：Research paper (international conference proceedings)  

    DOI： doi.org/10.4271/2013-01-2563

  • Experimental and numerical studies on burning velocities and Markstein numbers of lean laminar H2/CH4/air flames Reviewed International journal

    Okafor, E.C., Toyoda, M., Hayakawa, A., Nagano, Y., Kitagawa, T.

    Proceedings of the 9th Asia-Pacific Conference on Combustion   2013.7

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    Language：English   Publishing type：Research paper (international conference proceedings)  

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Books

  • Techno-Economic Challenges of Green Ammonia as an Energy Vector; Chapter 7: Applications

    De Vries N.; Okafor E. C.; Woo Y.; Giles A.; Valera-Medina A.（Role：Joint author）

    2021.10 

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    Language：English   Book type：Scholarly book

    DOI： 10.1016/B978-0-12-820560-0.00007-2

  • Techno-Economic Challenges of Green Ammonia as Energy Vector; Chapter 6:Use of Ammonia for Heat, Power and Propulsion

    De Vries N.; Okafor E. C.; Guesta-Bozo M.; Xiao H.; Valera-Medina A.（Role：Joint author）

    Academic Press  2021.10 

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    Language：English   Book type：Scholarly book

    DOI： 10.1016/B978-0-12-820560-0.00006-0

Presentations

  • A Study on the Elucidation of NOx Formation Pathways in Oxygen-Enriched Ammonia Combustion

    Shunnosuke ABE, Toshiaki KITAGAWA, Ekenechukwu C. OKAFOR

    第35回内燃機関シンポジウム  2023.12 

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    Event date： 2024.12

    Language：English  

    Venue：福岡   Country：Japan  

  • The effects of swirl number on the flow field and the lean stability limits of ammonia/hydrogen flames in a swirl burner

    KASAI Koki, HASEBE Tomohiro, TAGASHIRA Masahiko, KITAGAWA Toshiaki, OKAFOR Ekenechukwu C

    第62回燃焼シンポジウム  2024.11 

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    Event date： 2024.11

    Language：English   Presentation type：Oral presentation (general)  

    Venue：Osaka   Country：Japan  

  • Experimental and Numerical Investigation of the Effects of an Uncontrolled Primary Zone Dilution on Liquid Ammonia Spray Combustion International conference

    Ekenechukwu C. Okafor, Osamu Kurata, Hirofumi Yamashita, Norihiko Iki, Takahiro Inoue, Hyun Jo, Masayasu Shimura, Taku Tsujimura, Akihiro Hayakawa, Hideaki Kobayashi　

    Twenty-first International Conference on Flow Dynamics  2024.11 

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    Event date： 2024.11

    Language：English   Presentation type：Oral presentation (general)  

    Venue：Sendai   Country：Japan  

  • Combustion characteristics of hydrogen/oxygen/argon mixtures

    ＃Yuichi Shirayama, #Mizuki Sakuma, @Ekenechukwu C. OKAFOR, @Toshiaki KITAGAWA

    第34回内燃機関シンポジウム  2023.12 

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    Event date： 2023.12

    Language：English  

    Venue：東京   Country：Japan  

  • Effects of light olefins, ethanol and ETBE on the laminar burning velocity and the Markstein lengths of premixed flames of multicomponent fuels consisting of gasoline components

    @Ekenechukwu C. OKAFOR, ＃Tsuyoshi Ohama、#Takato Kataoka, @Toshiaki KITAGAWA

    第34回内燃機関シンポジウム  2023.12 

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    Event date： 2023.12

    Language：English  

    Venue：東京   Country：Japan  

  • The Development of Ammonia Combustion Technology for Gas Turbine Power Generation Invited International conference

    Ekenechukwu C. Okafor

    30th Korea Gas Saftey Seminar  2023.11 

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    Event date： 2023.11

    Language：English   Presentation type：Oral presentation (general)  

    Venue：Seoul   Country：Korea, Republic of  

  • Laminar burning velocity of hydrogen/oxygen/argon premixed laminar flames

    ＠OKAFOR Ekenechukwu C, ＃SHIRAYAMA Yuichi, ＃NAGAI Tatsushi, ＃SAKUMA Mizuki, ＠KITAGAWA, Toshiaki

    第61回燃焼シンポジウム  2023.11 

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    Event date： 2023.11

    Language：English  

    Venue：秋田アトリオン （秋田県・秋田市）   Country：Japan  

  • Development of Liquid Ammonia Spray Combustion Technology for Gas Turbines Invited

    Ekenechukwu C. Okafor

    第32回微粒化シンポジウム  2023.9 

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    Event date： 2023.9

    Language：English   Presentation type：Oral presentation (invited, special)  

    Venue：京都   Country：Japan  

  • 多孔型水素バーナNOx排出特性解明

    #イム ギョンウク, @Okafor Ekenechukwu, @内田 正弘, @辻村 拓, @北川 敏明

    日本機械学会2023年度年次大会  2023.9 

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    Event date： 2023.9

    Language：Japanese  

    Venue：東京   Country：Japan  

  • 乱れのスケールが化学量論及び希薄における水素火炎の燃焼速度に及ぼす影響

    #白山 雄一 , #岡本 雄飛, #永井 達士, @Okafor Ekenechukwu, @北川 敏明

    日本機械学会2023年度年次大会  2023.9 

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    Event date： 2023.9

    Language：Japanese  

    Venue：東京   Country：Japan  

  • Minimizing Uncertainties in Laminar Burning Velocity Measurement Using Constant Volume Combustion Chamber(CVCC) Invited International conference

    Ekenechukwu C Okafor

    Workshop on Ammonia Combustion Chemistry  2023.9 

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    Event date： 2023.9

    Language：English   Presentation type：Symposium, workshop panel (public)  

    Venue：Cardiff University   Country：United Kingdom  

  • Laminar Burning Velocity and Markstein Lengths of Premixed Flames of C5 – C8 Hydrocarbon Fuels

    @Ekenechukwu C. OKAFOR, #Tomoki IKEDA, #Yusuke KUBOTA, #Yuji TAGUCHI, #Yuhi OKAMOTO, #Toya TAKAHASHI, @Toshiaki KITAGAWA

    自動車技術会2023年春季大会  2023.5 

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    Event date： 2023.5

    Language：English  

    Venue：パシフィコ横浜 神奈川県横浜市西区   Country：Japan  

  • Liquid Ammonia Spray Combustion in Swirl Combustors； Studies on Flame Stabilization and Emissions Control Invited International conference

    Ekenechukwu C. Okafor

    2nd Ammonia Combustion Meeting  2023.5 

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    Event date： 2023.5

    Language：English   Presentation type：Oral presentation (general)  

    Country：Taiwan, Province of China  

  • 過濃イソオクタン球状伝播火炎におけるすす生成過程

    #田口祐治, #池田孝, @OKAFOR Ekenechukwu Chijioke, #渡邊裕章, #黒瀬良, @北川敏明

    第60回燃焼シンポジウム  2022.11 

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    Event date： 2022.11

    Language：Japanese  

    Country：Japan  

  • Laminar Burning Velocity of Premixed Flames of C5H10 Mixtures

    @Ekenechukwu C. OKAFOR, #Tomoki IKEDA, #Yusuke KUBOTA, #Yuji TAGUCHI, #Yuhi OKAMOTO, #Toya TAKAHASHI, @Toshiaki KITAGAWA

    第33回内燃機関シンポジウム  2022.11 

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    Event date： 2022.11

    Language：English  

    Country：Japan  

  • Studies on flame stabilization and emission control in ammonia-fueled gas turbine combustors Invited International conference

    Ekenechukwu C. Okafor

    KAUST-Tohoku University-Orléans core-to-core workshop  2022.9 

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    Event date： 2022.9

    Language：English   Presentation type：Symposium, workshop panel (public)  

    Venue：KAUST   Country：Saudi Arabia  

  • Investigation of flame stabilization and emission control in turbulent swirling ammonia flames Invited International conference

    Ekenechukwu C. Okafor

    2022 International Conference on Sustainable Energy Development  2022.8 

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    Event date： 2022.8

    Language：English   Presentation type：Oral presentation (general)  

    Venue：オンライン   Country：China  

  • アンモニア・メタン混焼火炎の排気ガス特性解明に関する研究 Invited

    Ekenechukwu C. Okafor

    自動車技術会 第1回ガス燃料エンジン部門委員会  2022.7 

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    Event date： 2022.7

    Language：Japanese   Presentation type：Symposium, workshop panel (public)  

    Venue：オンライン   Country：Japan  

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MISC

  • カーボンフリーアンモニア燃料の製造及び利用技術 : 福島再生可能エネルギー研究所における取り組み (特集 水素・脱炭素燃料の最新動向(その1))

    壹岐 典彦, 難波 哲哉, 倉田 修, Okafor Ekenechukwu, 辻村 拓

    日本ガスタービン学会誌   2021.3

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    Language：Japanese  

    Synthesis and Utilization Technology of Carbon Free Ammonia : Ammonia Initiative in Fukushima Renewable Energy Institute, AIST

Professional Memberships

  • Combustion Institute

  • Gas Turbine Society of Japan

  • 日本燃焼学会

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  • 日本機会学会

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Research Projects

  • Data-Driven Surrogate Modelling for Liquid Ammonia Direct Injection Spray Characteristics International coauthorship

    2024.3 - 2027.3

    Royal Society, London  

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    Authorship：Coinvestigator(s) 

    液体アンモニア噴霧燃焼技術の開発は、カーボンニュートラル社会の実現に関連する。この国際共同研究は、機械学習に基づく液体アンモニア噴霧特性の費用対効果の高いモデリング・アプローチを開発することを目的としている。シングルノズルおよびマルチノズル噴射弁からの液体アンモニア噴霧の特性を測定し、数値解析を用いてモデル化する。これらのデータは、液体アンモニア噴霧特性を予測するための高度な機械学習モデルの学習に使用される。

  • Investigation of a novel lean-lean two-stage combustion strategy for the control of NOx from swirl combustors fueled with mixtures of ammonia and hydrogen.

    Grant number：23K13263  2023.4 - 2025.3

    Japan Society for the Promotion of Science  Grants-in-Aid for Scientific Research  Early-Career Scientists

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    Authorship：Principal investigator  Grant type：Scientific research funding

  • アンモニア・天然ガス用工業炉のバーナに関する研究開発

    2022.4 - 2024.6

    Joint research

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    Authorship：Coinvestigator(s)  Grant type：Other funds from industry-academia collaboration

FD Participation

  • 2025.6   Role：Participation   Title：【SIAG FD】Towards a More Inclusive Kyushu University: On-Campus, Off-Campus, and Beyond

    Organizer：University-wide

  • 2025.5   Role：Participation   Title：【機械系FD開催】研究費の獲得について

    Organizer：[Undergraduate school/graduate school/graduate faculty]

  • 2025.2   Role：Participation   Title：【機械系FD開催】研究費の獲得について

    Organizer：[Undergraduate school/graduate school/graduate faculty]

  • 2024.10   Title：【機械系FD開催】学生とのかかわり方や学生の不登校に関すること

  • 2024.1   Role：Participation   Title：【機械系FD開催】科研申請について気を付けていること

    Organizer：[Undergraduate school/graduate school/graduate faculty]

  • 2023.1   Role：Participation   Title：【シス情FD】若手教員による研究紹介⑦

    Organizer：[Undergraduate school/graduate school/graduate faculty]

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Visiting, concurrent, or part-time lecturers at other universities, institutions, etc.

  • 2023  Jiangsu University, China  Classification:Affiliate faculty  Domestic/International Classification:Overseas 

    Semester, Day Time or Duration：2023年1月から2023年12月

  • 2022  産業技術総合研究所  Classification:Affiliate faculty  Domestic/International Classification:Japan 

    Semester, Day Time or Duration：2022年1月から2026年1月まで

Social Activities

  • 流れを知る・流れを操る

    Role(s)：Lecturer

    機械工学部門2024年度公開講座　  2024.10