Periodic Reporting for period 1 - HYGAS (Predictive tools for turbulent combustion of hydrogen-enriched natural gas through carefully reduced kinetic mechanisms)
Reporting period: 2022-01-17 to 2024-01-16
The growing crisis of environmental degradation necessitates the demand for alternative fuels. Hydrogen is seen as a promising energy carrier in the future energy landscape. However, the transition to a full hydrogen economy will be lengthy and requires significant R&D. Natural gas is seen as the transition fuel for hydrogen. Particularly, Hydrogen and Natural Gas (HyGAS) integration is regarded as a bridging technology to ease the transition towards a deep decarbonization. Injecting hydrogen into the natural gas network can contribute significantly to solving the problem of transporting and storing surplus electricity generated from renewable resources . The promising solution of Power-to-Gas (P2G) plants can convert locally generated electricity from wind and solar into hydrogen , which will be fed directly into gas distribution grids within permissible limits and be used by the customers to reduce carbon dioxide (CO2) emissions from household appliances and industrial processes . Besides the foreseeable advantage of reduction in CO2 emission, hydrogen enrichment is also a useful way to significantly enhance the combustion and flame dynamics by overcoming the drawbacks of natural gas such as local flame extinction, combustion instability and lower power output .
HyGAS was proposed against the above background with the aim to develop and validate a robust CFD based predictive tool for hydrogen-enriched natural gas with adequate chemistry. The specific research objectives include:
⁃ Improve detailed kinetic mechanism HP-Mech for hydrogen-enriched natural gas and validate the mechanism with available laminar flame speed, ignition delay time, and species profile, etc. in the ER’s work and literature;
⁃ Develop reduced kinetic mechanism using the PFA method and perform validations through comparison with the predictions of the detailed mechanism and the available experimental data;
⁃ Conduct CFD simulations using the newly developed reduced mechanism for small scale scenarios where test data are available for validation;
⁃ Extend CFD simulations to medium and large-scale scenarios for validation as well as applications.
HyGAS was proposed against the above background with the aim to develop and validate a robust CFD based predictive tool for hydrogen-enriched natural gas with adequate chemistry. The specific research objectives include:
⁃ Improve detailed kinetic mechanism HP-Mech for hydrogen-enriched natural gas and validate the mechanism with available laminar flame speed, ignition delay time, and species profile, etc. in the ER’s work and literature;
⁃ Develop reduced kinetic mechanism using the PFA method and perform validations through comparison with the predictions of the detailed mechanism and the available experimental data;
⁃ Conduct CFD simulations using the newly developed reduced mechanism for small scale scenarios where test data are available for validation;
⁃ Extend CFD simulations to medium and large-scale scenarios for validation as well as applications.
We systematically reevaluated the rates and corresponding uncertainties of H + O2 = O + OH (R1) based on our latest H2-O2 kinetic mechanism [named as Yang’s mech, Xueliang Yang et al., Journal of Physical Chemistry A, 2021, 125, 10223-10234] using reported shock tube experimental data from Ryu et al. (1995), Yuan et al. (1991), Masten et al. (1991) and Hong et al. (2011). The response of matching was altered to be the parameters like the maximum slope of the radical profile which was more robust with interference of the impurities regardless of the initial process. The chain-termination reaction of H + O2 ( + M ) =HO2 ( + M ) (R2) was reevaluated as well using Yang's mech for further constraint of the uncertainty of data interpretation. The weighted least-square fitting on all the experimental data with the updates on specific rates and uncertainties was conducted, which came up with new rate expressions of R1 and R2 and updated Yang's mech.
Simulations with above updated kinetic mechanism were performed to obtain the fundamental combustion characteristics, e.g. laminar flame speed (Mass burning rate), ignition delay time, profiles of species, etc. The results were compared with the experiments and the predictions of other mechanism, like HP Mech, Aramco Mech 3.0 and FFCM-1. The predictions of the updated mechanism at the same conditions are mostly within the error range of experimental data of mass burning rate.
The experiments at cryogenic temperatures were performed by the Fellow’s students at his home institution. The tests not only extend the observation of hydrogen explosion at extreme conditions, but also give broader targets for numerical model validation. Strong flame acceleration (FA), fast flame and the subsequent galloping detonation of hydrogen-oxygen mixtures in tube are investigated with different initial pressures at cryogenic temperature of 77 K.
Both 2D and 3D numerical model of flame propagating in closed tubes were built on the open-source platform OpenFOAM. The combustion solver XiFoam developed based on the flame wrinkling combustion model was selected. The large eddy simulation (LES) model can be computationally inexpensive while reproducing well the size and velocity of the annular vortex created before the propagating flame front and the evolution of the flame shape and structure. For large eddy simulation (LES), XiFoam solves the Navier-Stokes conservation equations of mass, momentum, and energy for unsteady compressible and reactive flows. The time integral was the first-order Euler format. For the gradient term, diffusion term, and Laplace, the Gaussian second-order linear scheme was used. The interpolation Schemes sub-dictionary contains terms that are interpolations of values typically from the grid body center to the grid front face center. The setting of Interpolation Schemes was linear as default in OpenFOAM. The PIMPLE algorithm was used to solve the discretization equation. The pressure equation and the velocity correction equation were iterated 20 times, and the pressure residual (tolerance) was 1×10-6.
Simulations with above updated kinetic mechanism were performed to obtain the fundamental combustion characteristics, e.g. laminar flame speed (Mass burning rate), ignition delay time, profiles of species, etc. The results were compared with the experiments and the predictions of other mechanism, like HP Mech, Aramco Mech 3.0 and FFCM-1. The predictions of the updated mechanism at the same conditions are mostly within the error range of experimental data of mass burning rate.
The experiments at cryogenic temperatures were performed by the Fellow’s students at his home institution. The tests not only extend the observation of hydrogen explosion at extreme conditions, but also give broader targets for numerical model validation. Strong flame acceleration (FA), fast flame and the subsequent galloping detonation of hydrogen-oxygen mixtures in tube are investigated with different initial pressures at cryogenic temperature of 77 K.
Both 2D and 3D numerical model of flame propagating in closed tubes were built on the open-source platform OpenFOAM. The combustion solver XiFoam developed based on the flame wrinkling combustion model was selected. The large eddy simulation (LES) model can be computationally inexpensive while reproducing well the size and velocity of the annular vortex created before the propagating flame front and the evolution of the flame shape and structure. For large eddy simulation (LES), XiFoam solves the Navier-Stokes conservation equations of mass, momentum, and energy for unsteady compressible and reactive flows. The time integral was the first-order Euler format. For the gradient term, diffusion term, and Laplace, the Gaussian second-order linear scheme was used. The interpolation Schemes sub-dictionary contains terms that are interpolations of values typically from the grid body center to the grid front face center. The setting of Interpolation Schemes was linear as default in OpenFOAM. The PIMPLE algorithm was used to solve the discretization equation. The pressure equation and the velocity correction equation were iterated 20 times, and the pressure residual (tolerance) was 1×10-6.
All of the updates of R1~R4 in the kinetic mechanisms were incorporated into the Yang’s mech, which will be used directly or reduced by PFA method for multi-scale simulations of combustion and explosion in other WPs.
Due to the rapid development of liquid hydrogen and the scarce data in the literature, our cryogenic works have resulted in significant advances beyond the state of the art. The work has attracted great attentions from Shanghai Jiaotong University, National University of Singapore, Peking University, CNRS etc.
The project publications have been widely cited by the researchers from Beijing University of Technology, Changzhou University, Federal University of Rio Grande do Sul.
Due to the rapid development of liquid hydrogen and the scarce data in the literature, our cryogenic works have resulted in significant advances beyond the state of the art. The work has attracted great attentions from Shanghai Jiaotong University, National University of Singapore, Peking University, CNRS etc.
The project publications have been widely cited by the researchers from Beijing University of Technology, Changzhou University, Federal University of Rio Grande do Sul.