Kinetics parameters evaluation of paraffin-based fuel

Resumo

In recent years, Hybrid Propulsion is turning into a significant alternative to Liquid and Solid Propulsion Systems, it presents attractive features and good balance between performance and environmental impact. Thus, paraffin based propellant grains are indicated as a substitute for hydroxyl-terminated polybutadiene (HTPB), the actual solid propellant fuel grain. Despite being a wellknown material, scarce data on the relation of activation energy (Ea) and molecular weight (WC H ) of paraffin is available. In this work, the kinetic parameters (activation energy and pre-exponential factor) of microcrystalline 140/1450F paraffin have been raised through Thermo Gravimetric Analysis in conjunction with the Arrhenius kinetic mechanism, according to ASTM-E1461 and the dependence of molecular weight with melting point from Etessam and Sawyer approach. The 140/1450F paraffin activation energy calculated in this study was compared with different activation energy from alkanes and substances used as fuel in the propulsion systems field. The analysis indicated that the microcrystalline 140/1450F paraffin, manufactured by Petrobras, presents activation energy of 224 KJ.mol-1 and pre-exponential factor of 5.48x1022 min-1. Ignition was achieved with a 50 W pyrotechnic igniter. The firing test with 140/1450F paraffin fuel and gaseous oxygen (GOX) mass flux of 130 Kg.s- 1m-2 at pressure above 0.80 MPa, was easily sustained. Copyright © 2012 by ASME.