The DENOX project implementation was originally planned in three consecutive stages:
• Stage 1: Fundamental studies of NOx generation and decomposition mechanisms
• Stage 2: Numerical and experimental studies of DENOX low emission concepts
• Stage 3: Proof-of-concept of DENOX low emission concepts combined application
During Stage 1, extensive studies encompassing theoretical kinetics, quantum chemistry, combustion gas dynamics, and gaseous discharges were conducted. A data bank of main parameters of species excited states was compiled to facilitate modelling and experiments involving stimulating electric discharge and electromagnetic fields. Specific analytical research, utilizing high-level CAE models, filled gaps in knowledge regarding abnormal excited states of key intermediate reagents in hydrocarbon-air flames and interaction between metastable terms of nitrogen-oxygen chemical bonds and external electromagnetic fields.
To address the complexity of total reaction general balance, an advanced filtration mechanism was developed and applied to electrochemical flame studies, significantly reducing reaction numbers, and making mathematical models practical for contemporary computational bases. Advanced sensitivity analysis and control methods excluded typical mistakes during reaction scheme simplification and ensured model accuracy for tasks involving abnormal quantum level distribution and transient speed-defining reaction bases.
Quantum chemistry analysis of nitrogen-oxygen, nitrogen-nitrogen, oxygen-oxygen, carbon-oxygen, carbon-hydrogen and oxygen-hydrogen bonds in various chemical species was performed using state-of-the-art software and mathematical models, guiding the exclusion of irrelevant excitation mechanisms and laying the groundwork for development of accurate multi-stage excitation mechanisms in regards of the existing oscillation generators and physically realistic parameters of electromagnetic fields in the dense environment.
Also, thorough design of experimental lab equipment was undertaken by engineer team in collaboration with theoretical and analytical researchers to develop sketches, blueprints and principal schematics for vertical atmospheric single burner test bench, mini-engine test bench, high-pressure test bench for 2 – 10 atm kerosene flames studies, electrical discharge system, measuring and control systems.
Following successful development and testing of the filtration method for simplifying the general balance of hydrocarbon flames, at the Stage 2, it was applied to diverse chemical kinetics scenarios in close correlation with the experimental data obtained within various experiments. The obtained results covered several research areas: (1) generation of intermediate radicals in high-temperature zones of flames; (2) macro and micro scale non-stationary gas dynamic effects in the primary combustion zone; (3) gas dynamic and electromagnetic parameters of discharge body and attached zone; (4) free electron energy distribution for three discharge types (arc, high frequency spark, corona); (5) generation of excited states of radicals, atoms, and molecules in the discharge body; (6) negative and positive ions generation in various stimulated flames; (7) mechanisms of NOx suppression and decomposition by abnormal particles and ions; etc.
Numerical experiments and mathematical modeling yielded important data on regular and stimulated flow structure, discharge-flow interaction, electromagnetic field propagation, and characteristics of electrochemical flames. This led to updates and corrections to the previously developed mathematical model.
Three discharge types (arc, high frequency spark, and corona) were studied through both numerical and physical experiments. Corona discharge, chosen for its significant positive impact on high-temperature combustion, emerged as most promising for the DENOX project. High frequency spark showed ambivalent, concentration-dependent stimulating nature, with some potential for NOx emission suppression. Arc discharge, while increasing NOx raw production, provided insights into discharge-flow interaction not observed with other discharge types.
Quantum chemistry numerical modeling facilitated the development of 6-stage terahertz excitation of nitrogen-oxygen chemical bonds in NO molecules across a range of temperatures. External consecutive axis-symmetrical fields were replaced by corona cascade excitation. Physical studies were interrupted due to the Russian invasion and ongoing war.
Stage 3, in fact, hadn’t started because of Russian aggression, but some numerical studies with experimentally approved main combustion zone electrochemical corona stimulation and developed during Stage 2 6-stages post-exhausting corona cascade excitation of NO were performed. According to obtained data, the combined influence of discharge stimulation and resonance excitation can provide the declared level of NOx reduction for gas turbine engine.
