N2O-HTPB Hybrid Rocket Combustion Modeling with Mixing Enhancement Designs

Abstract

One main physical feature of hybrid rocket combustion is its diffusion flame structure that requires excessively long solid grain port which often leads to undesirable large slenderness of a rocket configuration. The diffusion flame also results in generally low combustion efficiency of hybrid rockets. Some remedial designs have used liquefying solid grain, such as paraffin, or mixing enhancement mechanisms to boost the overall combustion efficiency. Thus, shortened combustion chamber can be used to deliver reasonable thrust performance of hybrid rockets. In addition to the study of multi-stage mixing enhancer effects, a compact hybrid rocket motor design concept is also proposed in the present study to provide better form factors for hybrid rocket engine designs. This design concept features in vertical-flow structures such that greatly improved combustion efficiency is obtained. A 3D computational model with finite-rate chemistry and radiative heat transfer capabilities is employed to assess the mixing effectiveness and combustion efficiency of the new design concept. The present computational model is validated for a wide range of rocket propulsion design problems, including a single-port hybrid rocket motor with and without using a mixing enhancement mechanism. The internal ballistics and flame structures in the hybrid rocket engine with mixing enhancement designs are analyzed. Nomenclature C 1 ,C 2 ,C 3 ,C  = turbulence modeling constants, 1.15, 1.9, 0.25, and 0.09. C p = heat capacity D = diffusivity F yz, F y, F z = integrated force, and component forces in the lateral direction Joint Propulsion Conferences 2 H = total enthalpy K = thermal conductivity or stiffness k = turbulent kinetic energy Q = heat flux T = temperature t = time, sec u = mean velocities V 2 =  u 2 x = Cartesian coordinates or nondimensional distance  = species mass fraction  = turbulent kinetic energy dissipation rate μ = viscosity μ t = turbulent eddy viscosity (=C  k 2 /) Π = turbulent kinetic energy production ρ = density  = turbulence modeling constants, 0.9, 0.9, 0.89, and 1.15 for Eqs. (2), (4-6). τ = shear stress ω = chemical species production rate or natural frequency Subscripts r = radiation t = turbulent flow

Thermal decomposition of N2O near 900 K studied by FTIR spectrometry: Comparison of experimental and theoretical O(3P) formation kinetics

“…Furthermore, motivated by the critical finding of Davidson et al 27 on the rate constant for O + N 2 O → N 2 + O 2 , k 3 = 10 12.15 exp[−(10.8 kcal mol −1 /RT)] cm 3 mol −1 s −1 , measured in the temperature range 1940-3340 K by direct O 2 UV absorption spectrometry, we carried out kinetic modeling for k 3 using the measured NO formed in reaction (2) in the temperature range 988-1083 K based on the competitive nature of reactions (2) and (3). With our k 1 and Davidson's k 2 , the result of the modeling gave rise to values of k 3 which are fully consistent with those of Davidson et al 27 A least-squares analysis of both sets of data points gives k 3 = 10 12.22 ± 0.04 exp[−(11.65 ± 0.24 kcal mol −1 /RT)] cm 3 mol −1 s −1 , covering the broad temperature range of 988-3340 K. This very significant finding deserves a thorough exploration for the mechanism of the reaction in the near future.…”

“…1 It is also a major initial decomposition product of ADN, NH 4 N(NO 2 ) 2 . 2 N 2 O has recently become a favored oxidant used in hybrid rocket propulsion 3,4 because of its favorable properties mentioned above. Theoretically, there have been numerous studies on the nonadiabatic dissociation process since the early work of Stearn and Eyring in 1935, combining the Landau-Zener theory for the forbidden transition with Eyring's transition state theory.…”

Multifunction Rocket System Development based on Advanced Hybrid Propulsion

“…Figures 1 and 2 show the computed flowfields for the ME and DVF hybrid rocket engines, respectively. The simulated thrust data of these engines were validated using measured data of hot-fire experiments [8,9]. Recent hot-fire tests of a 250 kgf DVF subscale N 2 O/HDPE engine have shown averaged sea-level Isp of 280 sec, which has provided a good technical guideline for scaling up designs to 3,500 kgf and 10,000 kgf thrust levels in the near future.…”

“…In the present line of research, innovative designs have been introduced in the past few years by employing mixing enhancement concepts with vortex generators and dual-vortical-flow (DVF) chambers [8,9]. In these studies, a high fidelity numerical model [10], with validations by hot-fire experiments, is employed in the study of the internal ballistics of hybrid combustion.…”

Variations and Control of Thrust and Mixture Ratio in Hybrid Rocket Motors

“…This solution has been tremendously successful in liquid propulsion as demonstrated by the Moon Landings [79]. On the opposite, in the hybrid field it has been proposed sometimes [80] but little activity has been performed, particularly in regard to throttling behaviour.…”