scholarly journals Nano-Sized and Mechanically Activated Composites: Perspectives for Enhanced Mass Burning Rate in Aluminized Solid Fuels for Hybrid Rocket Propulsion

Aerospace ◽  
2019 ◽  
Vol 6 (12) ◽  
pp. 127 ◽  
Author(s):  
Paravan
Keyword(s):  
Burning Rate ◽  
Solid Fuel ◽  
Mass Flux ◽  
High Speed ◽  
Rate Data ◽  
Mass Burning Rate ◽  
Diffusion Distance ◽  
Metal Combustion ◽  
Rate Enhancement ◽  
Regression Rate

This work provides a lab-scale investigation of the ballistics of solid fuel formulations based on hydroxyl-terminated polybutadiene and loaded with Al-based energetic additives. Tested metal-based fillers span from micron- to nano-sized powders and include oxidizer-containing fuel-rich composites. The latter are obtained by chemical and mechanical processes providing reduced diffusion distance between Al and the oxidizing species source. A thorough pre-burning characterization of the additives is performed. The combustion behaviors of the tested formulations are analyzed considering the solid fuel regression rate and the mass burning rate as the main parameters of interest. A non-metallized formulation is taken as baseline for the relative grading of the tested fuels. Instantaneous and time-average regression rate data are determined by an optical time-resolved technique. The ballistic responses of the fuels are analyzed together with high-speed visualizations of the regressing surface. The fuel formulation loaded with 10 wt.% nano-sized aluminum (ALEX-100) shows a mass burning rate enhancement over the baseline of 55% ± 11% for an oxygen mass flux of 325 ± 20 kg/(m2∙s), but this performance increase nearly disappears as combustion proceeds. Captured high-speed images of the regressing surface show the critical issue of aggregation affecting the ALEX-100-loaded formulation and hindering the metal combustion. The oxidizer-containing composite additives promote metal ignition and (partial) burning in the oxidizer-lean region of the reacting boundary layer. Fuels loaded with 10 wt.% fluoropolymer-coated nano-Al show mass burning rate enhancement over the baseline >40% for oxygen mass flux in the range 325 to 155 kg/(m2∙s). The regression rate data of the fuel composition loaded with nano-sized Al-ammonium perchlorate composite show similar results. In these formulations, the oxidizer content in the fuel grain is <2 wt.%, but it plays a key role in performance enhancement thanks to the reduced metal–oxidizer diffusion distance. Formulations loaded with mechanically activated ALEX-100–polytetrafluoroethylene composites show mass burning rate increases up to 140% ± 20% with metal mass fractions of 30%. This performance is achieved with the fluoropolymer mass fraction in the additive of 45%.

scholarly journals Effects of aluminum composites on the regression rates of solid fuels

2019 ◽  
Author(s):  
C. Paravan ◽  
S. Penazzo ◽  
S. Dossi ◽  
M. Stocco ◽  
L.T. DeLuca ◽  
...  
Keyword(s):  
Burning Rate ◽  
Ammonium Perchlorate ◽  
Solid Fuel ◽  
Data Reduction ◽  
Mass Flux ◽  
Performance Enhancement ◽  
Solid Fuels ◽  
Mass Burning Rate ◽  
Time Resolved ◽  
Ptfe Composites

Innovative, mechanically activated Al–polytetrafluoroethylene (PTFE) composites and ammonium perchlorate (AP) coated nano-sized aluminum (C-ALEX) were produced, characterized, and tested as solid fuel additives. The ballistics of fuel formulations based on hydroxylterminated polybutadiene (HTPB) was investigated in a microburner by a time-resolved technique for regression rate (rf) data reduction. Both Al-composites show promising results in terms of rf and mass burning rate enhancement. In particular, the C-ALEX showed a percent rf increase over the baseline (HTPB) of 27% at an oxidizer mass flux of 350 kg/(m2s), without requiring dedicated dispersion procedures. This performance enhancement was nearly constant over the whole investigated range.

Numerical investigation on operation characteristic of ramjet projectile

2019 ◽  
Vol 91 (7) ◽  
pp. 967-976
Author(s):  
Chang-Fei Zhuo ◽  
Ming-Xiao Wang ◽  
Wen-Jin Yao ◽  
Wen-ke Xu
Keyword(s):  
Mach Number ◽  
Kinetic Energy ◽  
Numerical Investigation ◽  
Solid Fuel ◽  
High Speed ◽  
Combustion Characteristic ◽  
Regression Rate ◽  
Content Type ◽  
Fuel Surface ◽  
Attachment Point

Purpose The purpose of this paper is to study the operation performance of the high-speed ramjet kinetic energy projectile using solid fuel ramjet as power plant that is a new short-range and small caliber projectile. Design/methodology/approach The numerical investigation on combustion characteristic of polyethylene in high-speed ramjet kinetic energy projectile is carried out in this paper. The flow characteristics’ differences are analyzed when ramjet works or do not work, and both the combustion characteristics and propulsive performance are analyzed when ramjet works. Findings The results show that with the increase of the abscissa x, the flame front is close to solid fuel surface at first and then keeps away from solid fuel surface. With the increase of the abscissa x, the temperature of solid fuel surface and regression rate of solid fuel continues to increase before re-attachment point and then decreases, which a maximum locate at the re-attachment point. Both the average temperature and the regression rate on the surface of the solid fuel tend to rise as the increase of inflow Mach number. As the inflow of Mach number increases, the mass flow rate of gaseous fuel increases. Practical implications The research results can provide useful database for the subsequent research on high-speed ramjet kinetic energy projectile. Originality/value This paper studies the operation characteristics of the ramjet projectile, especially the effect of the change of the flight velocity on the performance of high-speed ramjet projectile.

Mass Burning Rate of Syngas/Air Mixtures and Gas to Liquid Fuel Auto-Ignition at High Temperatures and Pressures

2016 ◽  
Author(s):  
Mimmo Elia ◽  
Matthew Ferrari ◽  
Omid Askari ◽  
Hameed Metghalchi
Keyword(s):  
Burning Rate ◽  
High Temperatures ◽  
High Speed ◽  
Equivalence Ratio ◽  
Initial Pressure ◽  
Mass Burning Rate ◽  
System Effect ◽  
Auto Ignition ◽  
Wide Range ◽  
Gas To Liquid

Mass burning speed and onset of auto-ignition of premixed syngas/air and gas to liquid (GTL)/air mixtures respectively, have been determined at high temperatures and pressures over a wide range of fuel-air equivalence ratios. The experimental facilities consist of two spherical and cylindrical vessels. The spherical vessel was used to collect pressure data to measure the burning speed, mass burning rate and determine the onset of auto-ignition and cylindrical vessel was used to take pictures of flame propagation with a high speed CMOS camera up to 40,000 frame per second located in a Schlieren system. Effect of cellular flames on mass burning rate have been determined. Critical pressures and temperature for different fuel air equivalence ratios at which auto-ignition takes place have been measured. In this paper, mass burning rate of syngas is calculated for a wide range of equivalence ratio from 0.6 to 2, unburned temperature from 400 to 680 K and initial pressure from 2 to 25 atm. A power law correlation has been developed as a function of equivalence ratio, temperature and pressure. The onset of auto-ignition for GTL/air mixture has been identified for equivalence ratio of 0.8 to 1.2.

scholarly journals Critical Review of the Methods to Measure the Condensed Systems Transient Regression Rate

2018 ◽  
Vol 20 (1) ◽  
pp. 45
Author(s):  
Vladimir Zarko
Keyword(s):  
Burning Rate ◽  
Critical Review ◽  
Energetic Materials ◽  
High Speed ◽  
Measurement Problem ◽  
Theoretical Models ◽  
Gas Generator ◽  
Regression Rate ◽  
High Speed Cinematography ◽  
Transient Burning Rate

Accurate knowledge of steady state and transient burning rate of solid fuels and energetic materials is very important for evaluating the performance of different propulsion and/or gas generator systems. The practical demands imply accuracy of available burning rate data on the level of 1% or better and proper temporal resolution. Unfortunately, existing theoretical models do not allow predicting the magnitude of the burning (regression) rate with needed accuracy. Therefore, numerous burning rate measurement methods have been developed by various research groups over the world in the past decades. This paper presents a critical review of existing techniques, including basic physical principles utilized for burning rate determination, an estimate of the temporal and spatial resolutions of the methods as well as their specific merits and limitations. There are known the methods for measuring linear regression rate via high speed cinematography, X-ray radiography and ultrasonic wave reflection technique. Actually, none of those methods could satisfy the practical demands. As an alternative is the microwave reflection method, which potentially possesses high spatial and temporal resolutions and may solve the measurement problem. In addition, there exist methods for measuring transient mass or weight of the burning material. They are based on recording the frequency of oscillations of elastic element with attached specimen or a cantilevered rod with a strain gauge pasted to the base. Practically, these methods could not provide needed accuracy. Much better parameters can be obtained when using the recoil force or microwave resonator techniques. Recommendations for special applications of certain methods are formulated.

Solid Fuel Fire Behavior Under Fixed Pressure in a Low-Pressure Chamber

2015 ◽  
Author(s):  
Rui Feng ◽  
Quanyi Liu ◽  
Runhe Tian ◽  
Kewei Chen ◽  
Rui Yang ◽  
...  
Keyword(s):  
Burning Rate ◽  
Solid Fuel ◽  
Fire Behavior ◽  
Low Pressure ◽  
Pressure Chamber ◽  
Fire Tests ◽  
Mass Burning Rate ◽  
Base Dimension ◽  
The Difference ◽  
Fire Characteristics

To comprehensively reveal the difference of solid fuel fire characteristics at different altitudes, fire experiments of cardboard boxes at multiple static pressures with two configurations filled with shredded office paper were conducted in a low-pressure chamber. The measured parameters are mass burning rate, radiative heat flux, oxygen concentration and heat release rate (HRR) etc. The mass burning rate divided by fire base dimension ṁ/D is correlated against the production of pressure-squared times length-cubed (P2L3) to the power of 0.29 based on current cardboard boxes fire test data. HRR of two boxes fire tests are higher than that of one box fire tests under fixed pressures. However, there are a higher peak of HRR under a fixed higher pressure for one-box fire tests while a lower peak of HRR under a higher pressure for two-box fire tests. The HRR would decrease sharply after reaching the peak.

scholarly journals Regression rate response in spin-stabilized solid fuel ramjets

2020 ◽  
Vol 37 ◽  
pp. 37-43
Author(s):  
Amir Mahdi Tahsini
Keyword(s):  
Burning Rate ◽  
Solid Fuel ◽  
Conjugate Heat Transfer ◽  
Rapid Change ◽  
Regression Rate ◽  
Convective Heat Flux ◽  
Burning Behavior ◽  
Steady State Operation ◽  
Unsteady Operation ◽  
Peak Value

ABSTRACT The regression rate of the solid fuel in the spinning solid fuel ramjet is investigated here using numerical simulations. The finite volume solver of the reacting turbulent flow is developed to study the flow field in the back-step combustion chamber where the burning rate of the solid fuel is computed using the conjugate heat transfer. The dependence of the burning rate on the circumferential velocity of the ramjet is studied, and it is shown that the spin augments the burning rate due to the enhancement of the convective heat flux along the fuel grain. So, the spin can be used to improve the performance of the solid fuel ramjets. In addition, the effect of rapid change in spin velocity on the regression rate of the fuel is investigated, which shows the transient-burning behavior. The results show that although the spin may increase the burning rate by ∼10% in steady-state operation of the ramjet, the spin acceleration may cause the overshoot in burning rate with the peak value &gt;30% in the unsteady operation.

Burning rate augmentation in solid fuel ramjets by swirling inlet air stream

2021 ◽  
pp. 095441002110014
Author(s):  
Amir Mahdi Tahsini
Keyword(s):  
Flow Field ◽  
Burning Rate ◽  
Solid Fuel ◽  
Swirling Flow ◽  
Reacting Flow ◽  
Linear Distribution ◽  
Regression Rate ◽  
Inlet Stream ◽  
Air Stream ◽  
Transfer Method

The influence of the inlet swirling flow on the regression rate of the fuel in the combustion chamber of the solid fuel ramjet is investigated in this study using numerical simulations. The finite-volume solver of the compressible turbulent reacting flow is developed to study the flow field where the burning rate is computed using the conjugate heat transfer method for the solid fuel. The correlation is found for the maximum regression rate versus an imposed inlet swirl when the linear distribution of the circumferential velocity is applied at the inlet stream. Although the regression rate augmentation is considerable due to the swirling flow field in the combustor, it is shown that the swirl is effective if is applied near the shear layer of the backstep flow in the combustor. The modified swirler with short blades is suggested to be used in solid fuel ramjets to increase the regression rate of the fuel and improve the performance, but with lower pressure loss.

scholarly journals Challenges of Ablatively Cooled Hybrid Rockets for Satellites or Upper Stages

Aerospace ◽  
2021 ◽  
Vol 8 (7) ◽  
pp. 190
Author(s):  
Francesco Barato
Keyword(s):  
Combustion Chamber ◽  
Solid Fuel ◽  
Diameter Ratio ◽  
Propulsion System ◽  
Burning Time ◽  
Regression Rate ◽  
Hybrid Propulsion ◽  
Deep Impact ◽  
Time Ratio ◽  
Hybrid Rockets

Ablative-cooled hybrid rockets could potentially combine a similar versatility of a liquid propulsion system with a much simplified architecture. These characteristics make this kind of propulsion attractive, among others, for applications such as satellites and upper stages. In this paper, the use of hybrid rockets for those situations is reviewed. It is shown that, for a competitive implementation, several challenges need to be addressed, which are not the general ones often discussed in the hybrid literature. In particular, the optimal thrust to burning time ratio, which is often relatively low in liquid engines, has a deep impact on the grain geometry, that, in turn, must comply some constrains. The regression rate sometime needs to be tailored in order to avoid unreasonable grain shapes, with the consequence that the dimensional trends start to follow some sort of counter-intuitive behavior. The length to diameter ratio of the hybrid combustion chamber imposes some packaging issues in order to compact the whole propulsion system. Finally, the heat soak-back during long off phases between multiple burns could compromise the integrity of the case and of the solid fuel. Therefore, if the advantages of hybrid propulsion are to be exploited, the aspects mentioned in this paper shall be carefully considered and properly faced.

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