Characterization of paraffin-based fuels and paraffin waxes for hybrid rocket engines

Abstract

This thesis develops an investigation on the rheological and mechanical properties of a class of paraffin-based fuels for hybrid rocket engines. They are obtained by mixing a paraffin wax and a polymer (SEBS, EVA and PE). Mixtures have a content of polymer equal to a 2,5%, 5%, 7,5% and 10%. Viscosity and surface tension obtained allows discovering the behaviour of fuels when different types of polymer are added. The main reason of taking these two properties is that they have a big influence in the combustion process. Surface tension tests were carried out using a tensiometer in order to obtain the surface tension for each fuel at 4 different temperatures, to know: 65ºC, 75ºC, 85ºC and 90ºC. Viscosity test were carried out using a rheometer with parallel-plates. All the paraffin-based fuels have been tested at many temperatures between 65ºC and 155ºC. This property has a strong influence in the regression rate, so it is a good option to characterize all these fuels. Besides, this thesis studies new paraffin waxes to be used as a base for new paraffin-based fuels. Polymers added to the paraffin wax change it properties. Finding new paraffin waxes with different properties can be interesting because at the end the paraffin-based fuels created can have other characteristics. Surface tension and tensile strength are obtained for 4 paraffin waxes, to know: JW50, JW62, JW58P and JWX. Surface tension experiments were carried out in the same way than experiments for paraffin-based fuels. The same instrument has been used and tests have been done at the same temperature. Tensile strength test carried out in order to obtain the Young’s modulus, stressstrain curve and the strain and stress values to the maximum stress point and to the break point.