Heat Exchanger Development at Reaction Engines Ltd.
- Paper number
IAC-08.C4.5.2
- Author
Mr. Richard Varvill, Reaction Engines Ltd., United Kingdom
- Year
2008
- Abstract
Hybrid airbreathing rocket engines for SSTO launch vehicles require sophisticated thermodynamic cycles with heat transfer between the fluid streams. The SABRE engine is liquid hydrogen fuelled and features a closed helium loop between the ‘hot’ airflow and the ‘cold’ hydrogen. To minimise compression work requirements and enable high Mach flight the intake airflow is initially cooled in a precooler involving up to 400MW of heat transfer. The helium loop powers the main turbocompressor but due to varying recovered air temperature with Mach number requires a top cycle heat exchanger (HX3) to deliver a constant inlet temperature to the main turbine. The precooler is an efficient counterflow design, consisting of many thousand small bore thin wall tubes arranged in involute spirals and wrapped into a cylindrical drum. Precooler manufacturing technology has been under investigation at REL for a number of years with the result that flightweight matrix modules can now be produced. High quality tubes drawn in Inconel 718 1mm diameter with 40 micron walls are capable of withstanding over 250 bar internal pressure. Various techniques for tube machining, forming, testing and cutting have been developed. Also brazing research into surface preparation, furnace cycles and assembly methods have led to pressure tight repeatable joints. A major difficulty with cooling the airflow to sub-zero temperatures at low altitude is the problem of frost formation which can block the matrix in a few seconds unless active measures are taken. Frost control technology has been developed which enables steady state operation and results of this program will be presented. The precooler research is culminating in the construction of a demonstration precooler to be run in front of a Viper jet engine at REL’s B9 test facility in 2009. This precooler will incorporate full frost control to enable steady state operation at sea level conditions. The precooler will be built from full size SABRE engine modules (same tube diameter and length) but will incorporate only 9 percent as many modules, reflecting the reduced airflow of the Viper. The facility will incorporate a high pressure helium loop which rejects the absorbed heat to a bath of liquid nitrogen. Research is also ongoing into the high temperature heat exchanger HX3. This is constructed in silicon carbide and the feasibility of manufacturing various matrix geometries have been investigated along with suitable joining techniques.
- Abstract document
- Manuscript document
IAC-08.C4.5.2.pdf (🔒 authorized access only).
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