Hydrogen-Based Intrinsic-Flame-Instability-Controlled Clean and Efficient Combustion

Introduction

Chemical energy carriers will play an essential role for future energy systems, where harvesting and utilization of renewable energy occur not necessarily at the same time or place. Hence, long-time storage and long-range transport of energy are needed.

Hydrogen-based Energy Carriers

For this, hydrogen-based energy carriers, such as hydrogen and ammonia, hold great promise. Their utilization by combustion-based energy conversion has many advantages, including:

• Versatile use for heat and power
• Robust and flexible technologies
• Suitability for a continuous energy transition

Challenges in Combustion

However, combustion of both hydrogen and ammonia is very challenging. For technically relevant conditions, both form intrinsic, so-called thermo-diffusive instabilities (very different from the often-discussed thermo-acoustic instabilities), which can increase burn rates by a stunning factor of three to five! Without considering this, computational design is impossible.

Current Understanding

While linear theories exist, little is understood for the more relevant non-linear regime. Beyond some data and observations, virtually nothing is known about the interactions of intrinsic flame instabilities (IFI) with turbulence.

Research Approach

Here, rigorous analysis of new data for neat H2 and NH3/H2-blends from simulations and experiments will lead to a quantitative understanding of the relevant aspects. From this, a novel modeling framework with uncertainty estimates will be developed.

Key Hypothesis

The key hypothesis is that combustion processes of hydrogen-based fuels can be improved by targeted weakening or promotion of IFI. This kind of instability-controlled combustion can jointly improve:

1. Efficiency
2. Emissions
3. Stability
4. Fuel flexibility in different combustion devices, such as:
   • Spark-ignition engines
   • Gas turbines
   • Industrial burners

Demonstration

Guided by the developed knowledge and tools, this intrinsic-flame-instability-controlled combustion concept will be demonstrated computationally and experimentally for two sample applications.