Simulation of DME-O₂ Combustion in a Hollow Cone Impinging Jet Combustor for Direct-Fired Supercritical CO₂ Power Cycle

ABSTRACT

Combustion is critical in the direct-fired supercritical CO₂ power cycle. A hollow cone impinging jet combustor is designed. Instead of methane, dimethyl ether is used as the fuel for the direct-fired supercritical CO₂ cycle, with a higher hydrocarbon ratio and oxygen. The dimethyl ether combustion process is simulated by Fluent, based on the k-ε turbulence model and Eddy-Dissipation Concept combustion model, combined with the dimethyl ether combustion mechanism. The effects of the CO₂ recycling ratio, the excess oxygen coefficient, and in-combustor pressure are investigated to support improving combustion performance. The results indicate that the recycled CO₂ intensifies the movement of the mixture in the combustor, reduces the peak temperature, and makes temperature distribution more uniform. As the excess oxygen coefficient increases, the peak temperature is enhanced, and the combustion is more sufficient. The effect of in-combustor pressure is complex. On the one hand, increasing in-combustor pressure reduces the jet penetration and inhibits the contact between dimethyl ether and O₂, leading to a lower peak temperature. On the other hand, it prolongs the residence time of the high-temperature exhaust, making the reaction between dimethyl ether and O₂ more sufficient. The optimal operating condition of the combustor is a CO₂ recycling ratio of 0.95, an excess oxygen coefficient of 1.20, and an in-combustor pressure of 30 MPa. Moreover, the obtained combustion products parameters, such as temperature, component concentration, and mass flow rate, can guide the performance analysis for the direct-fired supercritical CO₂ power cycle.

KEYWORDS:

• Direct-fired supercritical CO₂ power cycle
• dimethyl ether (DME)
• combustion
• Eddy-Dissipation Concept (EDC)

Disclosure statement

No potential conflict of interest was reported by the author(s).

Author contribution

Zhenchang Fang: Conceptualization; Methodology; Data curation; Formal analysis; Writing – original draft.

Xinyu Dong: Methodology; Data curation; Formal analysis; Writing – review & editing.

Zhao Lyu: Writing – review and editing.

Xinqi Qiao: Funding acquisition, Writing – review and editing.

Xinling Li: Writing – review and editing.

Kang Yang: Writing – review and editing.

Lintao Wang: Writing – review and editing.

Additional information

Funding

This study was financially supported by the National Natural Science Foundation of China [Grant Nos. 52006136] and the National Key R&D Program Intergovernmental International Cooperation in Science and Technology Innovation [2017YFE0130800].