Additives to Improve Methane Combustion

Liquefied methane is a promising fuel for space launch vehicles because it has a high specific impulse, excellent cooling capacity, and is very resistant to coking and soot formation. Unfortunately, it is also a very stable molecule and therefore ignition delay times can exceed combustor residence times. Shock tube measurements show that methane must be about 200 K hotter than n dodecane (a representative jet fuel compound) to achieve similar ignition delay times. Therefore, in order to utilize methane effectively, combustors must be larger, increasing the drag and weight of the vehicle. However, additives may significantly reduce methane ignition delay times. Additives can be designed to reduce ignition delay by lowering the activation energy of the combustion process after being injected directly into the combustion chamber. Alternatively, other additives such as hydrogen and acetylene, which can be produced from methane cracking reactions, ignite at lower temperatures and reduce ignition delay times when they are mixed with methane. In this phase I Project TDA Research, Inc. will synthesize and test several additives that function either by reducing ignition delay times when injected directly into a combustor or increase the rate of methane cracking when mixed with the fuel upstream of the combustor.