Experimental study on the effect of temperature and pressure on the stability of methane in rocket nozzle cooling channels

Background

Around the world, several organizations are researching and developing rocket engines using liquid methane and oxygen as propellants. This propellant combination, sometimes called “methalox”, has gained interest over the last years due to its favorable specific gravity, storage temperature, and thermal stability, which allow for the design of efficient and compact launch vehicles. Moreover, methane can be obtained from various sources including biogas and natural gas, but it can also be synthesized from water and hydrogen using the Sabatier process. This makes methane an interesting fuel for missions to e.g. Mars where these components are locally available.

As part of the European effort to develop methane-based rocket engines, KTH’s division of Heat and Power Technology (HPT) and industrial partner GKN Aerospace formed the MERiT project. In this research project, we are investigating the characteristics of methane when used as a coolant in additively manufactured cooling channels for rocket nozzles. One of the main aspects under investigation is the thermo-catalytic decomposition of methane in such channels. This so-called pyrolysis results in the deposition of solid carbon on the cooling channel walls, which acts as a thermal insulator. This deposition therefore leads to higher wall temperatures and reduced engine lifetime. The pyrolysis of methane depends, amongst others, on the flow properties temperature, pressure and residence time but also on the catalytic properties of the channel wall material and the purity of the fuel. These aspects are currently the focus of the investigation at HPT and an experimental setup, called the MERiT Small Pyrolysis Setup (SPS) has been developed with which the effects of these variables can be studied.

Thesis objectives

The aim of the thesis project is to design and implement an experimental campaign using the Small Pyrolysis Setup (SPS), with the objective of mapping the pyrolysis effect for methane at different pressure and temperature conditions. The project work will also include taking measurements of methane pyrolysis for different wall materials, as well as explaining and reporting the observed effects.

The specific objectives of this thesis are:

• To perform a literature review on the catalytic properties of relevant materials on methane pyrolysis
• To familiarize with
  • The SPS and previous developments
  • The requirements for gas analysis of other MERiT facility as well as existing measurement results
• To propose and implement improvements for the SPS, where necessary.
• To prepare an experimental plan for material testing with the goal of reaching the pyrolysis inception conditions
• To run experiments, collect and interpret data, and report this information.
• To work together with researchers at HPT to validate the measurement system for the operating conditions found in real rocket nozzle cooling channels.

Deliverables

The main deliverables of the project include but are not limited to:

• Final thesis report and presentation of the project
• Design and technical specification of the improved small pyrolysis setup
• Material measurement results

Duration

The project should start in Jan-Feb 2024 at the latest, with a duration of up to 6 months.

Contact persons

• Jens Fridh, MERiT research lead, lab manager at ITM/EGI/HPT

• Taras Koturbash, thesis supervisor, post-doctoral researcher at ITM/EGI/HPT

• Jules Heldens, thesis supervisor, PhD student at ITM/EGI/HPT