Fundamentals of hybrid boundary layer combustion

Marxman, G. A.; Muzzy, R. J.; Wooldridge, C. E.

doi:10.2514/6.1963-505

Cited by 57 publications

(47 citation statements)

References 3 publications

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“…Following an approach similar to the one presented by Marxman et al, 29 it is possible to formulate an analytical representation of the average regression rate down the fuel port.…”

Section: Appendix: Average Regression Rate Equationmentioning

confidence: 99%

Influence of a Conical Axial Injector on Hybrid Rocket Performance

Carmicino

Sorge

2006

Journal of Propulsion and Power

103

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This paper analyzes the results obtained from a series of static firings of a lab-scaled hybrid rocket in which gaseous oxygen was supplied into axial-symmetric polyethylene cylindrical grains through two different injector configurations: an axial conical subsonic nozzle and a radial injector. The axial injector is interesting because of its relatively easy design, the higher regression rates, and the noticeably stable motor operation. To exploit its qualities, not only the assessment of the regression rate but rather the entire behavior of the motor is required. For the investigated set of operating conditions, the instantaneous regression rates exhibit a time dependence caused by the impinging jet zone dynamics, while the average regression rates are higher and less mass flux dependent than those achieved with the radial injection motor and expected from the classical turbulent-boundary-layer diffusionlimited theory. A comparison to the data from the radial injector was further drawn in terms of combustion efficiency and fuel regression uniformity. Concerning combustion stability, some observations are made. The radial injector, at the same mass flux and pressure, produces lower regression rates, high pressure oscillations, and worse combustion efficiency, but more uniform fuel consumption. Nomenclatureof ultrasounds in reference conditions c * = characteristic exhaust velocity c * 0 = theoretical characteristic exhaust velocity calculated at O/F c * = theoretical characteristic exhaust velocity calculated at OF D = space average port diameter D 0 = port initial diameter D 2 = average port final diameter D 2x = local port final diameter d = diameter E a = activation energy F = motor thrust G = mass flux H v = effective heat of vaporization I m = mixing index L = grain length L c = prechamber length L * = chamber characteristic length l = exponent of the Reynolds number in the mixing index definition m = exponent of the geometrical ratio in the mixing index definitioṅ m f = fuel mass flow ratė m ox = oxidizer mass flow rate = isentropic one-dimensional mass flow rate through the nozzle N = number of data points in the port diameter profiles n = exponent of mass flux OF = spatially averaged oxidizer-to-fuel ratio OF = mean value of spatially averaged oxidizer-to-fuel ratios O/F = average oxidizer to average fuel mass ratio p a = ambient pressure p e = nozzle-exit pressure R = gas constant Re = Reynolds numbeṙ r = space average regression ratė r x = local regression rate s = fuel grain thickness T w = fuel surface temperature t = time V e = isentropic one-dimensional velocity at nozzle exit x = axial abscissa z = nondimensional axial abscissa (x/L) α = nozzle divergence cone half-angle M f = measured solid fuel mass loss M f = computed solid fuel mass loss t = time step t o = ultrasounds time of flight η = c * efficiency, ratio between the actual and theoretical c * th η 0 = c * efficiency calculated at O/F λ = momentum-thrust reduction coefficient μ = gas viscosity ρ f = solid fuel density σ = standard deviation...

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“…Following an approach similar to the one presented by Marxman et al, 29 it is possible to formulate an analytical representation of the average regression rate down the fuel port.…”

Section: Appendix: Average Regression Rate Equationmentioning

confidence: 99%

Influence of a Conical Axial Injector on Hybrid Rocket Performance

Carmicino

Sorge

2006

Journal of Propulsion and Power

103

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“…The well-known blowing effect induced by the radial flow of this ablated fuel material generally results in low overall fuel regression rates. 3 Hybrid motors which are based on ablating fuel grains typically produce regression rates that are significantly lower than solid fuel motors in the same thrust and impulse class. Increasing the oxidizer mass flux increases fuel regression rates; unfortunately, the resulting combustion instabilities at high flux rates limit the effectiveness of this option.…”

Section: B Technical Limitations Of Hybrid Rocket Systemsmentioning

confidence: 99%

“…18 The fundamental assumption made by Marxman and his colleagues was that regression rates in a hybrid rocket are dominated by thermal diffusion and not chemical kinetics. 3 Consequently the fuel surface regression is strongly a function of turbulent boundary-layer heat transfer. Boundary layer mixing creates a region where oxidizer flow from the center of the motor combustion port mixes with vaporizing solid fuel leaving the fuel wall.…”

Section: A Hybrid Motor Fuel Regressionmentioning

confidence: 99%

Design and Testing of FDM Manufactured Paraffin-ABS Hybrid Rocket Motors

McCulley¹,

Bath²,

Whitmore³

2012

48th AIAA/ASME/SAE/ASEE Joint Propulsion Conference &Amp;amp; Exhibit

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This research investigates techniques for fabricating hybrid rocket fuel grains composed of porous Acrylonitrile-butadiene-styrene impregnated with paraffin wax. The ABS substrate provides mechanical support for the paraffin fuel material and serves as an additional fuel component. The embedded paraffin provides an enhanced regression rate while having no detrimental effect on the thermodynamic burn properties of the fuel grain. Fused Deposition Modeling manufacturing techniques are used to fabricate the ABS substrate that supports the paraffin fuel. Multiple fuel grains with various ABS-to-Paraffin mass ratios were fabricated and burned with nitrous oxide. Analytical predictions for end-to-end motor performance and fuel regression are compared against static test results. Baseline fuel grain regression calculations use an enthalpy balance energy analysis with the material and thermodynamic properties based on the mean paraffin/ABS mass fractions within the fuel grain. In support of these analytical comparisons, a novel method for propagating the fuel port burn surface was developed. In this modeling approach the fuel cross section grid is modeled as an image with white pixels representing the fuel and black pixels representing empty or burned grid cells. A suite of standard MATLAB image-processing techniques is used to regress the fuel grain geometry.

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“…When the proportion of soot and metal oxide particles is small, the contribution of the radiative heat flux can usually be neglected as shown in [13]. Then, one haṡ…”

Section: Boundary Layer Combustion and Heat Transfer Modelsmentioning

confidence: 99%