To reduce CO2 emissions from thermal power plants, increasing attention has been directed toward ammonia as an effective hydrogen energy carrier and as a fuel. A major technical challenge associated with ammonia combustion is the suppression of nitrogen oxides (NOx) emissions formed from fuel-bound nitrogen. The authors have developed a 20% ammonia/coal co-firing (on an energy basis) combustion technology that achieves emission levels comparable to those of single coal combustion in burner combustion tests. To confirm applicability to an actual coal-fired power plant, an ammonia co-firing test was conducted at a 1000 MW commercial power plant under actual operating conditions. As a result, approximately 20% reduction in direct CO2 emissions at the preheater inlet (per unit electricity generated), consistent with the carbon balance of the fuel mixture, was confirmed under actual 1000 MW commercial-scale operating conditions. NOx emissions were maintained at levels equal to or lower than those under single coal combustion, and no significant increase of unburnt carbon in ash was detected. Furthermore, plant operability under load-changing conditions was confirmed to be equivalent to that of conventional coal-fired operation. These results clearly indicated that ammonia co-firing can be applied to a 1000 MW-class opposed-firing boiler under uniform multi-burner co-firing conditions.
A novel autoignition-assisted, high-temperature High-Pressure Well-Stirred Turbulent Combustor (HP-WSTC) has been developed for detailed kinetic studies of fuels under gas-turbine conditions that were difficult to obtain with conventional reactors and flame chemistry facilities. It is designed for operations at 1–20 atm, 1200–2200 K, and residence times of 1–100 ms, enabling treatment as a zero-dimensional premixed-combustion system. Methane combustion experiments at 1–10 atm were compared with 0D simulations, showing good agreement for major species across a wide equivalence-ratio range, demonstrating the reliability of the HP-WSTC. Although methane combustion kinetics are well established, NO predictions still show large discrepancies, even at atmospheric pressure. Sensitivity analyses identify CH-pool reactions, including CH2 + O2 = CH2O + O and CH + CO2 = HCO + CO, as key uncertain reactions. The developed HP-WSTC provides a new platform for fuel kinetic investigations and bridges the gap between reactor and flame facilities for high-temperature kinetic studies under gas-turbine conditions.
While gradually varying fin sizes can significantly enhance heat dissipation compared to uniform fins, the prohibitive computational cost of full-scale analysis makes their efficient design unrealizable. To address this limitation, this study develops a topology optimization method for pin fin heat sinks which effectively reduces the prohibitive computational cost through a surrogate-based multiscale analysis. The proposed multiscale approach combines a three-dimensional microscale analysis of individual fins and a pseudo-three-dimensional macroscale analysis. First, microscale thermal-fluid analyses are conducted to construct a surrogate model based on radial basis function interpolation. Then, this surrogate model is utilized for the macroscale thermal-fluid analysis by providing effective thermal-fluid properties corresponding to local fin geometries. Based on this multiscale framework, topology optimization is performed to minimize the base plate temperature under energy loss constraints, using fin pitch and channel-to-pitch ratio as continuous design variables. Finally, a novel geometry reconstruction method is developed to bridge the gap between continuous optimization variables and discrete manufacturable geometries, enabling a direct translation to manufacturing-ready fin layouts without the geometric ambiguities present in existing approaches.
