Combustion of Bio-derived Fuels With Additives and Research on the Losses of Unburned Fuel in Hybrid Propellant Rocket Engines

Centrifugal Casting of Paraffin and Beeswax for Hybrid Rockets

“…The field of beeswax-fueled hybrid chemical propulsion is considerably underdeveloped compared to paraffin. An extensive search of literature related to beeswax hybrid rocket fuels yields a series of initial studies at the University of Tennessee, Knoxville culminating in two postgraduate theses [10,34,35], a series of annual senior design projects at Central Connecticut State University [36][37][38][39][40][41][42][43][44], and the lone peer reviewed article in the field of beeswax propulsion by the Egyptian Space Technology Centre [45]. Most of these works generally investigated a broad range of bioderived hybrid rocket fuels, but beeswax consistently proved most practical as a hybrid rocket fuel.…”

“…A series of studies by Naoumov et al from 2013 to 2020 attempted to establish regression rate comparisons between paraffin, beeswax, and each of these with up to 10% micron-sized aluminum powder added for fuel grain port diameters of 12.7, 25.4, and 38.1 mm at combustion chamber pressures of 0.448 to 0.965 MPa [36][37][38][39][40][41][42][43][44]. Over 150 hot fires were conducted with gaseous oxygen alongside theoretical thermodynamic calculations which showed (1) little influence of aluminum addition on regression rate, (2) experimentally-determined regression rates of beeswax above those for paraffin reported by Karabeyoglu [3] but below those for beeswax reported by Putnam [35] at similar conditions; namely, oxidizer mass fluxes between 0.7 and 1.75 g/cm 2 s. Experimental efforts in these studies were plagued with low oxidizer mass flow rates (0.5-0.95 equivalence ratios), though in the most recent work attempts at increasing the mass flow rate of gaseous oxygen proved successful [44].…”

“…Over 150 hot fires were conducted with gaseous oxygen alongside theoretical thermodynamic calculations which showed (1) little influence of aluminum addition on regression rate, (2) experimentally-determined regression rates of beeswax above those for paraffin reported by Karabeyoglu [3] but below those for beeswax reported by Putnam [35] at similar conditions; namely, oxidizer mass fluxes between 0.7 and 1.75 g/cm 2 s. Experimental efforts in these studies were plagued with low oxidizer mass flow rates (0.5-0.95 equivalence ratios), though in the most recent work attempts at increasing the mass flow rate of gaseous oxygen proved successful [44]. An idiosyncrasy of this series of studies is the novel attempt to estimate unburned fuel losses using thermocouples placed downstream of the nozzle exit, predominantly discussed in Naoumov 2015 [39]. The publication most focused on beeswax and beeswax with aluminum additive results is that of Naoumov 2016a [40].…”