Additive manufacturing for hydrogen turbines
Micromix burners and effusion cooling: How AM prevents H2 flameback.
1. Introduction: The decarbonization of energy
In order to achieve the energy transition, power plant operators worldwide (such as Siemens Energy or Ansaldo Energia) are converting their huge gas turbines from natural gas to green hydrogen. But hydrogen (H2) is not an ordinary fuel gas. It is extremely reactive, burning almost three times as fast as methane and producing much hotter flames.
When you ignite hydrogen in a classic gas burner, the flame often burns back against the gas flow so quickly that it hits the inside of the burner (flame flashback) and destroys it. In order to burn hydrogen safely, you need highly complex burner geometries (micromix burners), which cannot be produced conventionally. Here 3D printing (PBF-LB) is the only savior.
How does 3D printing prevent flashback?
In micromixing, the hydrogen is not injected from a large nozzle, but rather mixed into the air stream through hundreds to thousands of microscopic, aerodynamically shaped channels. These miniature nozzles accelerate the hydrogen-air mixture so much that the flow speed is higher than the flame speed. The flame can no longer physically fight back.
2. The magic of cooling channels (effusion cooling)
Because hydrogen flames are extremely hot (up to 2,100°C), the walls of the combustion chamber would melt instantly (even if they were made of superalloys such as Hastelloy X or Inconel 718).
Through metal 3D printing, the wall of the combustion chamber is printed double-walled with complex lattice structures inside. Cold air is forced through this inner layer. But that's not all: the wall is permeated by microscopic, conical-shaped pores. The air escapes through these pores and forms a protective “cold film” (effusion cooling) over the metal. The component burns in hellfire, but remains structurally intact inside.
3. Avoidance of hydrogen embrittlement
Hydrogen is the smallest atom in the universe. It diffuses (creeps) through solid steel walls, deposits on the grain boundaries of the metal and builds up extreme pressure there. The result: The steel becomes hard, loses its toughness and suddenly breaks (hydrogen embrittlement).
In 3D printing, this risk can be minimized metallurgically.
- Optimized structure: The rapid cooling in the laser process creates an extremely fine-grained structure with homogeneously distributed precipitates.
- Porosity Control: Each internal pore is a potential “reservoir” for hydrogen gas. Additively manufactured burners for H2 turbines are therefore necessarily hot isostatically pressed (HIP) in order to completely eliminate any internal cavities and not provide any surface for the hydrogen atoms to attack.
4. Rapid prototyping for flame dynamics
Burner design is high-end flow simulation (CFD). What the computer calculates must be physically tested on the test bench. Conventionally, casting a prototype burner often took six months. With 3D printing, engineers can print five slightly modified burner designs in a week, flame test them on Friday, and release the optimized design for series production on Monday.
5. Conclusion: No energy transition without AM
Without the geometric freedom of additive manufacturing, there would be no modern hydrogen burners. The extremely delicate micromixing channels and the conformal wall cooling that are necessary to tame H2 flames can neither be cast nor milled. 3D printing made of high-performance nickel alloys is the technological backbone that enables fossil-free electricity generation of the future.