Combustion Characteristics of a Swirl-Radial-Injection Composite Fuel Grain with Applications in Hybrid Rockets

Abstract

The combustion characteristics of a swirl-radial-injection composite fuel grain were experimentally and numerically investigated. This composite grain permits swirl-radial oxidizer injection based on three hollow helical blades, each having a constant hollow space allowing uniform oxidizer injection into the main chamber along the axial direction. The oxidizer enters from channel inlets located along a hollow outer wall. This wall, together with the three blades, is fabricated as one piece from acrylonitrile-butadiene-styrene using three-dimensional printing. Paraffin-based fuel is embedded in the spaces between adjacent blades. Firing tests were conducted with gaseous oxygen as the oxidizer, using oxidizer mass flow rates ranging from 7.45 to 30.68 g/s. Paraffin-based fuel grains using conventional fore-end injection were used for comparison. Regression rate boundaries were determined taking into account the erosion of the oxidizer channels. The data show that the regression rate was significantly increased even at the lower limit. Images of the combustion chamber flame and of the exhaust plume were also acquired. The flame was found to be concentrated in the main chamber and a smoky plume was observed, consistent with the high regression rate. A three-dimensional simulation was employed. The present design was found to improve fuel/oxidizer mixing and combustion efficiency compared with a fuel grain using fore-end injection. Both the experimental results and numerical simulations confirmed the potential of this swirl-radial-injection fuel grain.

Combustion Characteristics of Vat-Photopolymerized Fuels with a Spiral Star Port for Hybrid Propulsion

“…As combustible gas C 2 H 4 is continuously introduced into the computational domain through wall mass addition and the initial value of the CO 2 mass fraction in the computational domain is patched to 0.01 for the successful ignition, the rate of C 2 H 4 consumption and the rate of CO 2 generation cannot be directly used to determine the combustion efficiency. On the basis of eq , 1 kmol (18 kg) of H 2 O is produced from 1.5 kmol (48 kg) of oxygen, , written as η combustion , H 2 O = ṁ H 2 O , x ṁ O 2 , inlet × 2 3 M W H 2 O = true[ prefix∫ 8 3 α normalH 2 normalO ρ u d A true] inlet x true[ prefix∫ α normalO 2 ρ u d A true] oxidizer,inlet x where α H 2 O and α O 2 are the mass fractions of water vapor and oxygen, respectively, ρ (kilograms per cubic meter) is the mixed gas density, u (meters per second) is the axial velocity, A (square meters) is the cross-sectional area at point x , and MW H 2 O and MW O 2 (kilograms per kilomole) are the molecular weights of H 2 O and O 2 , respectively.…”

“…As combustible gas C 2 H 4 is continuously introduced into the computational domain through wall mass addition and the initial value of the CO 2 mass fraction in the computational domain is patched to 0.01 for the successful ignition, the rate of C 2 H 4 consumption and the rate of CO 2 generation cannot be directly used to determine the combustion efficiency. On the basis of eq 5, 1 kmol (18 kg) of H 2 O is produced from 1.5 kmol (48 kg) of oxygen, 47,48 written as ) of 3.00 g/s, and Figure 12b illustrates the combustion efficiency for different ratios of oxidant to fuel in S60. The combustion efficiency of all grains is higher toward the rear end compared to the head end and increases with an increase in axial distance.…”