Vooruitgang op het gebied van hygiëne en naleving

Materials for top performance

The students also needed special materials that are  able  to  withstand  extreme stress. Yves Riedo reached deep into the vaults: “One of the materials we used was Kalrez^® with a selling price of several thousand euros per kilogramme.” The material allowed the students to carry out the maximum number of tests – without having to replace the seals and dismantle the engine every time. “If you want to win, you have to be better than the competition,” says Yves Riedo with a twinkle in his eye. The engine required a complete sealing system of 17 O-rings in six different dimensions, and a combination of five different materials. There had to be seals between the injector and combustion chamber, the combustion chamber and outlet nozzle, for the cooling system within the nozzle with the connections to the casing and the plenum chamber, as well as for diverse sensors within the injector (see illustration). In addition to the Kalrez^® (FFKM) already mentioned, an ethylene propylene diene monomer elastomer (EPDM), a fluoroelastomer (FKM) and a fluoroelastomer (FKM) with a seamless FEP lining (FEP-O-SEAL^®) were used.

The engine will be filled with an explosive oxidising agent that is warmed to reach a pressure of around seventy bar. In operation minus temperatures are encountered briefly in the injector and also temperatures up to +2800 degrees in the combustion chamber. Consequently, the sealing system will be confronted with conditions of extreme chemical and thermal  stress  and  needs  to function reliably several  times.  “We use nitrous oxide as the oxidising agent combusted with sorbitol. It also contains paraffin and aluminium,” says the ETHZ student. “The special material that we selected to use gives us a clean seal on the copper outlet nozzles no matter how high the temperatures or size of expansion gap. The seals on the injector, meanwhile, fulfil the requirements of nitrous oxide fully.” With New Mexico clearly in sight: It’s not going to be a matter of the materials.

 

Kalrez^® is a DuPont™ brand. DuPont™, the DuPont Oval Logo, and all trademarks and service marks denoted with ™ or ^® are owned by affiliates of DuPont de Nemours, Inc. 

Engine cross-section
On the left is the injector plate for the liquid oxidising agent that on injection is atomised and vapourised. The injector has to remain sealed for both physical states. The oxidising agent then reacts with the gradually vapourising fuel (grain) in the combustion chamber. Pressure is generated by combustion of the gas mixture, which is transformed into kinetic energy by means of the copper Laval nozzles. And in accordance with the rocket principle produces the thrust of the engine.

The engine will be filled with an explosive oxidising agent that is warmed to reach a pressure of around seventy bar. In operation minus temperatures are encountered briefly in the injector and also temperatures up to +2800 degrees in the combustion chamber. Consequently, the sealing system will be confronted with conditions of extreme chemical and thermal  stress  and  needs  to function reliably several  times.  “We use nitrous oxide as the oxidising agent combusted with sorbitol. It also contains paraffin and aluminium,” says the ETHZ student. “The special material that we selected to use gives us a clean seal on the copper outlet nozzles no matter how high the temperatures or size of expansion gap. The seals on the injector, meanwhile, fulfil the requirements of nitrous oxide fully.” With New Mexico clearly in sight: It’s not going to be a matter of the materials...