NH3 marine engine — one cylinder research engine has successfully started combustion process development

The subpro­ject CF08_2 will realize the demons­tra­tion of the propul­sion system for an inland waterway vessel, which is operated with ammonia as fuel. For stable igni­tion of the ammonia-air-mixture in the engine, as a novelty in this project, a partial stream of the ammonia is passed over a cracker before the engine, where it is dispersed into hydrogen and nitrogen. The addi­tion of a certain amount of hydrogen helps in the combus­tion chamber of the engine to ignite and comple­tely burn the slug­gish-igni­table ammonia.

Funda­mental rese­arch into this combined ammonia-hydrogen combus­tion process is an important compo­nent of the CF08_2 subpro­ject. For this purpose, a single-cylinder rese­arch engine was set up in Karls­ruhe at KIT, which repres­ents the process of one cylinder in the future ship propul­sion system under labo­ra­tory condi­tions. The expe­ri­mental setup makes it possible to vary the mixing of air with ammonia and hydrogen in various ways and to study the effects on combus­tion and pollutant forma­tion. The ammonia can be supplied either in liquid or gaseous form.

For the expe­ri­mental set-up in the labo­ra­tory, simi­larly complex safety conside­ra­tions have been estab­lished as those that have to be made in an inland waterway vessel. Protec­ting people and the envi­ron­ment when hand­ling ammonia is also a new chall­enge for the rese­ar­chers. Important pionee­ring work has already been done here for the test setups at the further test sites within CF08_2 and for use onboard a ship, too.

After inten­sive prepa­ra­tion, the test setup was successfully commis­sioned in February 2023 and the engine operated for the first time with a combined hydrogen-ammonia combus­tion for several hours. Vari­ants and conver­sions will follow in the coming weeks and months to answer the follo­wing questions:

• What is the minimum hydrogen content required, and what is the maximum H2 content that can be tole­rated for all opera­ting points rele­vant for ship opera­tion? This is an important para­meter for the design of the upstream cracker, whose dyna­mics are diffe­rent from those of the engine.
• Which loca­tions on the engine are optimum to supply the hydrogen and the ammonia? Which aggre­gate state of the ammonia is best? Which injec­tion pres­sures are most suitable?
• Which compres­sion ratio and which amount of air repre­sent the best compro­mise in terms of maximum effi­ci­ency and minimum pollutant emissions?
• Which design has to be applied to the engine compon­ents to with­stand the demands of the multi-cylinder-engine-tests in Rostock?

The results of the work on the rese­arch single-cylinder engine will be conti­nuously commu­ni­cated within the subpro­ject and will be incor­po­rated into the expe­ri­mental setup and rese­arch test runs in Duis­burg and Rostock.