Understanding lean premixed hydrogen combustion under moderate pressures

• Applicant: Dr.-Ing. Tao Li
• Subject Area: Energy Process Engineering ; Technical Thermodynamics
• Term: since 2025
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 556960810

This project aims to experimentally investigate lean premixed hydrogen/air combustion under turbulent and pressurized conditions by developing and applying advanced laser optical diagnostics. The primary scientific objectives are to determine turbulent flame speeds and understand thermo-diffusive instabilities impacting turbulent lean premixed hydrogen flames at elevated pressure. To achieve these goals, a novel optically accessible pressure vessel for operating a turbulent jet burner, and optical diagnostics capable of measuring 3D flame surfaces and quantifying temperature distributions will be developed. The proposed research program pursues five overarching objectives: 1. Establish a Pressurized Hydrogen Combustion Test Rig: A test rig will be developed that includes a piloted turbulent premixed hydrogen/air jet burner and an optically accessible pressure vessel. This setup will target a maximum pressure of 10 bar. 2. Characterize Macroscopic Flame and Flow Dynamics: Simultaneous single-shot Particle Image Velocimetry (PIV) and OH-Laser-Induced Fluorescence (OH-LIF) measurements will be used to study the macroscopic characteristics of the flame and flow. These measurements will be conducted under various conditions, including different effective Lewis numbers (by varying the equivalence ratio), turbulent velocities (by varying the bulk velocity), and pressures. 3. Develop Methodology for Measuring 3D Flame Surface Area: To accurately measure the 3D flame surface area, which is critical for determining turbulent flame speeds, a novel rapid scanning SO2-LIF technique will be developed. 4. Measure Turbulent Flame Speed: The turbulent flame speed of premixed H2/air and N2-diluted H2/air mixtures (i.e. assuming H2 is from NH3 cracking) will be quantified for varying effective Lewis numbers, turbulence intensities, and pressures. This effort will provide a comprehensive database to derive empirical power-law scaling relations. 5. Analyze Thermo-Diffusive Instabilities: Using simultaneous OH-LIF for flame front detection and Rayleigh scattering for gas phase thermometry, the thermo-diffusive nature of lean premixed hydrogen flames will be studied in detail. This analysis will focus on the influences of pressure, turbulence, and Lewis number. The experimental results will be interpreted in collaboration with external numerical partners. The obtained data aims to enhance our understanding of the dynamics and structure of premixed hydrogen flames under pressure and provide a valuable database for validating numerical models used in large-scale simulations of practical combustors.

• DFG Programme: Research Grants