An energetic binder based on hydroxyl-terminated polybutadiene(HTPB),doped with different ratios of nitrocellulose(NC)(10%,20%,30%,and 50%),was developed to study the effect of NC doping on the thermal decomposition b...An energetic binder based on hydroxyl-terminated polybutadiene(HTPB),doped with different ratios of nitrocellulose(NC)(10%,20%,30%,and 50%),was developed to study the effect of NC doping on the thermal decomposition behavior of a composite propellant(CP)comprising ammonium nitrate(AN)as an oxidizer and magnesium(Mg)as a fuel.Optimization of the propellant formulation was conducted using Chemical Equilibrium with Applications-National Aeronautics and Space Administration(CEA-NASA)software,which demonstrated an increase in specific impulse by 12.09 s when the binder contained 50%NC.Fourier-transform infrared spectroscopy(FTIR)analysis confirmed the excellent compatibility between the components,and density measurements revealed an increase of 6.4%with a higher NC content.Morphological analysis using optical microscopy showed that NC doping improved the uniformity and compactness of the surface,reduced cavities,and achieved a more homogeneous particle distribution.Differential scanning calorimetry(DSC)analysis indicated a decrease in the decomposition temperature of the propellant as the NC content increased,while kinetic studies revealed a 48.68%reduction in the activation energy when 50%NC was incorporated into the binder.These findings suggest that the addition of NC enhances combustion efficiency and improves overall propellant performance.This study highlights the potential of the new HTPB-NC energetic binder as a promising approach for advancing solid propellant technology.展开更多
When older stocks of ammunition are fielded for use, propellant degradation may be of concern.Degraded propellants may result in either increased or decreased chamber pressures, depending on formulation(thus deviating...When older stocks of ammunition are fielded for use, propellant degradation may be of concern.Degraded propellants may result in either increased or decreased chamber pressures, depending on formulation(thus deviating from expected performance), or in the worst-case scenario, auto-ignition.Data is sparse regarding propellants aged naturally in manufactured ammunition. Propellant harvested from 1953 U S. military 30-06 M2 AP rifle cartridges and from 2012 U S. military M855A1 rifle cartridgs was evaluated using thermochemical techniques and field testing. Thermochemical results were also compared with two 2022-era ball propellants(Winchester 748 and Hodgdon BL-C(2)). Thermal analysis demonstrated similar energy densities between the 1953, 2012, and ca. 2022-era propellants,with minor changes in activation energy, suggesting slightly decreased propellant thermal stability in the1953 propellant. Chemical analysis supported this observation, with slightly decreased levels of stabilizer(still above accepted minimums) and increased levels of stabilizer byproducts in the 1953 propellant. For field testing, 0.223 Remington rifle cartridges were prepared for the 1953 and 2012 propellants utilizing the same match-grade components and a volume of the respective propellant to result in a muzzle velocity around 800 m/s. Accuracy characteristics and variation in projectile velocity were evaluated in a standardized competition course of fire. For each propellant, 20 rounds were shot from one bolt action rifle with a 1 in 8 inches twist, and 20 rounds were shot from another with a 1 in 7 inches twist. Results showed that the 1953-era propellant demonstrated comparable standard deviations in velocity and ontarget precision to the 2012-era propellant, and both resulted in comparable standard deviations in velocity and on-target performance to a modern extruded commercial reloading propellant.展开更多
Feasible and accurate acoustic modeling of external and internal aircraft environments is essential for designing low-noise multi-propeller aircraft.This work proposes a novel sound source equivalent approach using Li...Feasible and accurate acoustic modeling of external and internal aircraft environments is essential for designing low-noise multi-propeller aircraft.This work proposes a novel sound source equivalent approach using Lighthill's sound sources(monopole and dipole point sources)for simulating propeller noise.It establishes data transmission interfaces between aerodynamic acoustics and acoustic-solid coupling.Equations are expanded from acoustic pressure to monopole amplitude and dipole moment vector.The basic assumption is that the propeller noise has similar spatial radiation directivity as the sound point source.The radiation relationships are explicitly built between harmonic propeller noise and dipole sources at cabin cross-sections,and between harmonic propeller noise and monopole sources along cabin longitudinal sections.External acoustic pressure distributions of cabin noise are calculated using Unsteady Reynolds-Averaged Navier-Stokes(URANS)and Ffowcs Williams-Hawkings(FW-H)approach.Interior noise is calculated using frequency domain acoustic-solid coupling.Sound source equivalent approach is used to calculate the equivalent intensity of monopole or dipole point sources for external excitation.To assess accuracy of the proposed approach,both external and interior noise of a turboprop aircraft with four sixbladed propellers are calculated and compared against flight trial results of a C-130J-30 Hercules.The turboprop aircraft adopts the same size parameters as the C-130J-30 Hercules.The present frequency domain acoustic approach is accurate for interior cabin noise.It is beneficial for enhancing the design of the low-noise turboprop aircraft.展开更多
In this study,we introduce a deep generative model,named Multi-Species Generative Adversarial Network(MS-GAN),which is developed to extract the low-dimensional manifold of three-dimensional multi-species surfaces.In t...In this study,we introduce a deep generative model,named Multi-Species Generative Adversarial Network(MS-GAN),which is developed to extract the low-dimensional manifold of three-dimensional multi-species surfaces.In the development of MS-GAN,we extend the freeform deformation by incorporating principal component analysis to increase the non-linear deformation ability while maintaining geometric smoothness.The implicit information of multiple baselines is embedded in the feature extraction layers,to enhance the diversity and parameterization of multi-species dataset.Furthermore,Wasserstein GAN with a gradient penalty is used to ensure the stability and convergence of the training networks.Two experiments,ruled surfaces and propeller blade surfaces,are performed to demonstrate the advantages and superiorities of MS-GAN.展开更多
Numerical simulations were conducted on a 10-blade Sevik rotor ingesting wake downstream of two turbulence-generating grids.These simulations were based on implicit large-eddy simulation(ILES)and the boundary data imm...Numerical simulations were conducted on a 10-blade Sevik rotor ingesting wake downstream of two turbulence-generating grids.These simulations were based on implicit large-eddy simulation(ILES)and the boundary data immersion method(BDIM)for compressible flows,which were solved using a fully self-programmed Fortran code.Results show that the predicted thrust spectrum aligns closely with the experimental measurements.In addition,it captures the thrust dipole directivity of the noise around the rotating propeller due to random pressure pulsations on the blades,as well as the flow structures simultaneously.Furthermore,the differences in the statistical characteristics,flow structures,and low-frequency broadband thrust spectra due to different turbulence levels were investigated.This analysis indicates that the interaction between the upstream,which is characterized by a lower turbulence level and a higher turbulent length of scale,and the rotating propeller results in a lower amplitude in force spectra and a slight increase in the scale of tip vortices.展开更多
Polar marine equipment plays an important role in Arctic engineering,especially in the development of polar ships and ice-class propellers.When polar ships navigate in brash ice channels,the brash ice not only increas...Polar marine equipment plays an important role in Arctic engineering,especially in the development of polar ships and ice-class propellers.When polar ships navigate in brash ice channels,the brash ice not only increases resistance but also has adverse effects on their propulsion performance.On the basis of coupled computational fluid dynamics(CFD)and the discrete element method(DEM),this paper aims to numerically investigate the resistance and propulsion performance of a polar in a brash ice channel while considering the rotation status of the propeller by both experimental and numerical methods.Both ship resistance and ice motion under Froude numbers of 0.0557,0.0696,0.0836,0.975,and 0.1114 are studied when the propeller does not rotate.The influences of the rotating propeller on the ice brash resistance and flow are discussed.The thrust due to the propeller and ice resistance in the equilibrium state are also predicted.The errors between the thrust and total resistance are approximately 1.0%,and the maximum error between the simulated and predicted total resistance is 3.7%,which validates the CFD-DEM coupling method quite well.This work could provide a theoretical basis for the initial design of polar ships with low ice class notation and assist in planning navigation for merchant polar ships in brash ice fields.展开更多
Understanding the behaviour of composite marine propellers during operating conditions is a need of the present era since they emerge as a potential replacement for conventional propeller materials such as metals or a...Understanding the behaviour of composite marine propellers during operating conditions is a need of the present era since they emerge as a potential replacement for conventional propeller materials such as metals or alloys.They offer several benefits,such as high specific strength,low corrosion,delayed cavitation,improved dynamic stability,reduced noise levels,and overall energy efficiency.In addition,composite materials undergo passive deformation,termed as“bend-twist effect”,under hydrodynamic loads due to their inherent flexibility and anisotropy.Although performance analysis methods were developed in the past for marine propellers,there is a significant lack of literature on composite propellers.This article discusses the recent advancements in experimental and numerical modelling,state-of-the-art computational technologies,and mutated mathematical models that aid in designing,analysing,and optimising composite marine propellers.In the initial sections,performance evaluation methods and challenges with the existing propeller materials are discussed.Thereafter,the benefits of composite propellers are critically reviewed.Numerical and experimental FSI coupling methods,cavitation performance,the effect of stacking sequence,and acoustic measurements are some critical areas discussed in detail.A two-way FSI-coupled simulation was conducted in a non-cavitating regime for four advanced ratios and compared with the literature results.Finally,the scope for future improvements and conclusions are mentioned.展开更多
Aluminum-water(Al-H_(2)O)propellants represent an innovative class of solid propellants characterized by low cost and minimal signal signature.However,conventional formulations are hindered by significant aluminum(Al)...Aluminum-water(Al-H_(2)O)propellants represent an innovative class of solid propellants characterized by low cost and minimal signal signature.However,conventional formulations are hindered by significant aluminum(Al)agglomeration,leading to reduced combustion efficiency and substantial residues.This study introduces a method for modifying Al powder with Polyvinylidene Fluoride(PVDF)to enhance the performance of Al-H_(2)O propellants by mitigating agglomeration during combustion.Experimental methodologies,including thermogravimetric analysis under ambient-pressure nitrogen atmosphere and laser ignition tests,were employed to investigate the influence of varying PVDF content on the combustion characteristics of the propellants.Furthermore,the effect of PVDF on motor performance was systematically evaluated through laboratoryscale Solid Rocket Motor(SRM)tests.The results demonstrate that the addition of 7.5%PVDF significantly enhances the burning rate from 1.12 mm/s to 3.78 mm/s and reduces the mean particle size of condensed combustion products from 699μm to 527μm.Combustion efficiency rises from88.57%to 94.51%,while injection efficiency improves significantly from 30.45%to 70.45%.SRM tests further demonstrate an increase in combustion chamber pressure from 0.17 MPa to 0.58 MPa.A dynamic agglomeration model explains these improvements,attributing reduced agglomeration to enhanced aerodynamic forces and a thinner melting layer,while increased gas yield improves injection performance.This study highlights PVDF's potential in advancing Al-H_(2)O propellants by improving combustion and injection efficiency.展开更多
Propeller design is a highly intricate and interdisciplinary task that necessitates careful trade-offs between radiated noise levels and aerodynamic efficiency.To achieve efficient trade-off designs,an enhanced on-the...Propeller design is a highly intricate and interdisciplinary task that necessitates careful trade-offs between radiated noise levels and aerodynamic efficiency.To achieve efficient trade-off designs,an enhanced on-the-fly unsteady adjoint-based aerodynamic and aeroacoustic optimization methodology is developed,which maintains the fidelity of the Navier-Stokes solution for unsteady flow and of the moving-medium Ffowcs Williams-Hawkings(FW-H)formulation for capturing tonal noise.Furthermore,this on-the-fly approach enables a unified architecture for discreteadjoint sensitivity analysis encompassing both aerodynamics and aeroacoustics,facilitating effective multi-objective weighted optimizations.Subsequently,this proposed methodology is applied to perform trade-off optimizations between aerodynamics and aeroacoustics for a propeller by employing varying weighting factors to comprehend their influence on optimal configurations.The results demonstrate a positive correlation between efficiency and noise sensitivities,and thus indicate an inherent synchronicity where pursing noise reduction through purely aeroacoustic optimization inevitably entails sacrificing aerodynamic efficiency.However,by effectively incorporating appropriate weighting factors(recommended to range from 0.25 to 0.5)into the multi-objective function combined with both aerodynamics and aeroacoustics,it becomes feasible to achieve efficiency enhancement and noise reduction simultaneously.Key findings show that reducing blade planform size and equipping“rotated-S”shaped airfoil profiles in the tip region can effectively restrain noise levels while maintaining aerodynamic performance.展开更多
Bonding quality at the interface of solid propellant grains is crucial for the reliability and safety of solid rocket motors.Although bonding reliability is influenced by numerous factors,the lack of quantitative char...Bonding quality at the interface of solid propellant grains is crucial for the reliability and safety of solid rocket motors.Although bonding reliability is influenced by numerous factors,the lack of quantitative characterization of interface debonding mechanisms and the challenge of identifying key factors have made precise control of process variables difficult,resulting in unpredictable failure risks.This paper presents an improved fuzzy failure probability evaluation method that combines fuzzy fault tree analysis with expert knowledge,transforming process data into fuzzy failure probability to accurately assess debonding probabilities.The predictive model is constructed through a general regression neural network and optimized using the particle swarm optimization algorithm.Sensitivity analysis is conducted to identify key decision variables,including normal force,grain rotation speed,and adhesive weight,which are verified experimentally.Compared with classical models,the maximum error margin of the constructed reliability prediction model is only 0.02%,and it has high stability.The experimental results indicate that the main factors affecting debonding are processing roughness and coating uniformity.Controlling the key decision variable as the median resulted in a maximum increase of 200.7%in bonding strength.The feasibility of the improved method has been verified,confirming that identifying key decision variables has the ability to improve bonding reliability.The proposed method simplifies the evaluation of propellant interface bonding reliability under complex conditions by quantifying the relationship between process parameters and failure risk,enabling targeted management of key decision variables.展开更多
AP(Ammonium Perchlorate)and HMX(Octogen)are the two oxidizers most often used in Nitrate-Ester-Plasticized Polyether(NEPE)rocket propellants.How the AP–HMX ratio influences the agglomeration of NEPE propellants remai...AP(Ammonium Perchlorate)and HMX(Octogen)are the two oxidizers most often used in Nitrate-Ester-Plasticized Polyether(NEPE)rocket propellants.How the AP–HMX ratio influences the agglomeration of NEPE propellants remains unclear.We experimentally investigated the effect of the AP–HMX ratio on the combustion and agglomeration of NEPE propellants using burning rate test,quenched surface analysis,microscopic observations,and the collection of condensed combustion products.It was found that with the decrease in AP content from 40wt%to 10wt%,the burning rate decreased from 14.2 mm/s to 9.2 mm/s because the adiabatic flame temperature of NEPE propellants decreased from 3828 K to 3736 K.Pockets bounded by AP particles appeared on the surface when AP content was 40wt%;however,the accumulations grew and covered the burning surface eventually as the AP–HMX ratio decreased.The time required for the accumulation to coalesce into agglomerates increased with decreasing AP content.Even with similar agglomerate sizes,the coalescence time increased by 83%when the AP content decreased from 40wt%to 30wt%.The agglomerate size in the Condensed Combustion Products(CCPs)increased from 100μm to 200μm,and the fraction of large agglomerations increased from 6.4%to 24.7%when the AP content decreased from 40wt%to 10wt%.Overall,the high flame temperature of the AP particles enhanced the decomposition of the surrounding binder,resulting in the rapid ejection of the aluminum particles into the gas,which had a separating effect on the accumulation,thus weakening the agglomeration.展开更多
This study represents an important step forward in the domain of additive manufacturing of energetic materials.It presents the successful formulation and fabrication by 3D printing of gun propellants using Fused Depos...This study represents an important step forward in the domain of additive manufacturing of energetic materials.It presents the successful formulation and fabrication by 3D printing of gun propellants using Fused Deposition Modeling(FDM)technology,highlighting the immense potential of this innovative approach.The use of FDM additive manufacturing technology to print gun propellants is a significant advancement due to its novel application in this field,which has not been previously reported.Through this study,the potential of FDM 3D-printing in the production of high-performance energetic composites is demonstrated,and also a new standard for manufacturability in this field can be established.The thermoplastic composites developed in this study are characterized by a notably high energetic solids content,comprising 70%hexogen(RDX)and 10%nitrocellulose(NC),which surpasses the conventional limit of 60%energetic solids typically achieved in stereolithography and light-curing 3D printing methods.The primary objective of the study was to optimize the formulation,enhance performance,and establish an equilibrium between printability and propellant efficacy.Among the three energetic for-mulations developed for 3D printing feedstock,only two were suitable for printing via the FDM tech-nique.Notably,the formulation consisting of 70%RDX,10%NC,and 20%polycaprolactone(PCL)emerged as the most advantageous option for gun propellants,owing to its exceptional processability,ease of printability,and high energetic performance.展开更多
Low erosion high-energy propellant is one of the research directions to extend the weapon’s life and improve the weapon’s capability.In this study,energetic propellants containing different corrosion inhibitors were...Low erosion high-energy propellant is one of the research directions to extend the weapon’s life and improve the weapon’s capability.In this study,energetic propellants containing different corrosion inhibitors were designed and prepared.Close bomb tests and semi-confined bomb experiments were used to investigate the burning and erosion properties of the propellants.The mechanism of erosion-reducing of titanium dioxide(titania,TiO_(2)),talc,and octaphenylsilsesquioxane(OPS)on the propellant was comparatively analyzed.The results show that OPS has the lowest burning rate and the longest burning time,and a minimized loss of fire force,with the best effect of explosion heat reduction.The erosion reduction efficiency of OPS is twice that of TiO_(2) and talc.The mechanism analysis shows that the decomposition and heat absorption of OPS can effectively reduce the thermal erosion effect and carbon erosion,and the gas produced can reduce the loss of chamber pressure and form a uniformly distributed nano-SiO_(2) protective layer.This solid-state high-efficiency organosilicon erosion inhibitor is an important guide for designing high-energy low-erosion gun propellants.展开更多
Distributed ducted propellers hold significant promise for propulsion systems in Advanced Air Mobility(AAM) due to their high efficiency, low noise, and enhanced redundancy and safety. However, a standardized benchmar...Distributed ducted propellers hold significant promise for propulsion systems in Advanced Air Mobility(AAM) due to their high efficiency, low noise, and enhanced redundancy and safety. However, a standardized benchmark for comparing the aerodynamic characteristics of different ducted propeller configurations remains lacking. Including additional ducted propellers can further complicate the flow field. This paper proposes an equivalent design method for ducted propellers based on the momentum theorem and similarity criteria, introducing three equivalent ducted propeller cases. Transient numerical simulations are conducted using the sliding mesh model. The three cases produce comparable thrust while consuming the same power, with the volume of distributed ducted propellers being reduced by over 29% compared to the single ducted propeller. This study investigates the effect of rotational frequency on aerodynamic performance under hovering conditions. While propeller performance demonstrates low sensitivity to variations in rotational frequency, duct performance exhibits high sensitivity. The research further examines how rotational frequency changes the pressure difference between the duct leading edge and trailing edge. Based on a sensitivity analysis of aerodynamic performance, the flow field mechanisms under different rotational consistency are examined for the case with one duct and two propellers. Differences in aerodynamic performance are attributed to the airflow velocity gradient differences at the duct leading edge and the flow separation characteristics on the crossing side. These findings are significant for enhancing the performance of distributed ducted propellers and improving aircraft controllability.展开更多
Combustion catalyst is a key modifier for the performance of composite solid propellant.To exploit highefficiency combustion catalyst,a fascinating bimetallic metal-organic framework[MnCo(EIM)_(2)(DCA)_(2)]n(1)was con...Combustion catalyst is a key modifier for the performance of composite solid propellant.To exploit highefficiency combustion catalyst,a fascinating bimetallic metal-organic framework[MnCo(EIM)_(2)(DCA)_(2)]n(1)was constructed by an active dicyandiamide(DCA)linker,Mn^(2+),Co^(2+)centers,and an 1-ethylimidazole(EIM)ligand.1 possesses good thermal stability(Tp=205℃),high energy density(Eg=24.34 kJ/g,Ev=35.93 kJ/cm^(3)),and insensitivity to impact and frictional stimulus.The catalytic effects of 1 contrasted to monometallic coordination compounds Mn(EIM)_(4)(DCA)_(2)(2)and Co(EIM)_(4)(DCA)_(2)(3)on the thermal decomposition of AP/RDX composite were investigated by a DSC method.The decomposition peak temperatures of AP and RDX of the composite decreased to 335.8℃ and 206.4℃,respectively,and the corresponding activation energy decreased by 27.3%and 43.6%,respectively,which are better than the performances of monometallic complexes 2 and 3.The gas products in the whole thermal decomposition stage of the sample were measured by TG-MS and TG-IR,and the catalytic mechanism of 1 to AP/RDX was further analyzed.This work reveal potential application of bimetallic MOFs in the composite solid propellants.展开更多
The simultaneous integration of high energy density,low sensitivity,and thermal stability in energetic materials has constituted a century-long scientific challenge.Herein,we address this through a dualzwitterionic el...The simultaneous integration of high energy density,low sensitivity,and thermal stability in energetic materials has constituted a century-long scientific challenge.Herein,we address this through a dualzwitterionic electronic delocalization strategy,yielding TYX-3,the first bis-inner salt triazolo-tetrazine framework combining these mutually exclusive properties.Uniformπ-electron distribution and elevated bond dissociation energy confer exceptional thermal stability(T_(d)=365℃)with TATB-level insensitivity(impact sensitivity IS>40 J,friction sensitivity FS>360 N).Engineeredπ-stacked networks enable record density(1.99 g·cm^(-3))with detonation performance surpassing HMX benchmarks(detonation velocity 9315 m·s^(-1),detonation pressure 36.6 GPa).Practical implementation in Poly(3-nitratomethyl-3-methyloxetane)(PNMMFO)solid propellants demonstrates 5.4-fold safety enhancement over conventional HMX-based formulations while maintaining equivalent specific impulse.This work establishes a new design paradigm for energetic materials,overcoming the historical trade-offs between molecular stability and energy output through rational zwitterionic engineering.展开更多
The efficacy of spacecraft propulsion systems significantly depends on the choice of propellant.This study utilized laser-induced breakdown spectroscopy(LIBS)to investigate the impact of different fuel types,fuel rati...The efficacy of spacecraft propulsion systems significantly depends on the choice of propellant.This study utilized laser-induced breakdown spectroscopy(LIBS)to investigate the impact of different fuel types,fuel ratios,and laser energies on the plasma parameters of ammonium dinitramide(ADN)-based liquid propellants.Our findings suggest that 1-allyl-3-methylimidazolium dicyanamide(AMIMDCA)as a fuel choice led to higher plasma temperatures compared to methanol(CH_3OH)and hydroxyethyl hydrazine nitrate(HEHN)under the same experimental conditions.Optimization of the fuel ratio proved critical,and when the AMIMDCA ratio was 21wt.%the propellants could achieve the best propulsion performance.Increasing the incident laser energy not only enhanced the emission spectral intensity but also elevated the plasma temperature and electron density,thereby improving ablation efficiency.Notably,a combination of 100 mJ laser energy and 21wt.%AMIMDCA fuel produced a strong and stable plasma signal.This study contributes to our knowledge of pulsed laser micro-ablation in ADN-based liquid propellants,providing a useful optical diagnostic approach that can help refine the design and enhance the performance of spacecraft propulsion systems.展开更多
As core components of precision-guided projectiles,projectile-borne components are highly susceptible to failure or even damage in complex high-overload environments,thereby significantly compromising launch reliabili...As core components of precision-guided projectiles,projectile-borne components are highly susceptible to failure or even damage in complex high-overload environments,thereby significantly compromising launch reliability and safety.However,accurately characterizing the mechanical behavior of propellants remains challenging due to the limitations in the current internal ballistic theory and the constraints of large-scale artillery firing experiments.This complicates the high-precision numerical modeling of projectile launch,and obstructs investigations into the failure mechanisms of projectile-borne components.Therefore,this paper identifies propellant parameters using the computational inverse method under uncertainty,further establishes high-precision numerical models of projectile launch,and explores the failure mechanisms of projectile-borne components in complex high-overload environments.First,a projectile launching experiment is meticulously designed and executed to obtain the breech pressure and muzzle velocity.Then,a general simulation model is built,and the powder burn model is used to simulate the ignition and combustion.Subsequently,the propellant parameters are effectively identified with the computational inverse method by the combination of the experiments and simulations.A high-precision numerical model of projectile launch is modified with the parameters validated by another experiment,and the high-overload characteristics during projectile launch are thoroughly analyzed based on this model.Finally,the high-overload characteristics of projectile-borne components are analyzed to elucidate the stress variation laws and to reveal the failure mechanisms influenced by time and spatial locations.This research provides an effective method for perfectly identifying propellant parameters and building high-precision numerical models of projectile launch.Additionally,it provides significant guidance for the anti-high overload design and analysis of projectile-borne components.展开更多
With the development of high energy solid propellants,it is critical to evaluate the safety and power performance of solid propellants in the face of threats such as unmanned aerial vehicles(UAVs)when transporting and...With the development of high energy solid propellants,it is critical to evaluate the safety and power performance of solid propellants in the face of threats such as unmanned aerial vehicles(UAVs)when transporting and using them in contemporary warfare.An electric probe-type cylinder test measured the displacement-time behavior of NEPE high-energy solid propellant,and the parameters of the Jones-Wilkins-Lee(JWL)equation of state(EOS)were derived using particle swarm optimization(PSO)with the Gurney energy model.Further,the parameters of JWL-Miller EOS,determined through AUTODYN simulations,were validated by comparing airburst process simulations with experimental overpressure data.The study established a method for determining EOS parameters of high-energy propellants,achieving a high degree of accuracy.The derived parameters ensure precise modeling of propellant behavior,offering a reliable foundation for future applications in solid rocket motor performance optimization and safety assessment.展开更多
In designing modern vessels, calculating the propulsion performance of ships in ice is important, including propeller effective thrust, number of revolutions, consumed power, and ship speed. Such calculations allow fo...In designing modern vessels, calculating the propulsion performance of ships in ice is important, including propeller effective thrust, number of revolutions, consumed power, and ship speed. Such calculations allow for more accurate prediction of the ice performance of a designed ship and provide inputs for designers of ship power and automation systems. Preliminary calculations of ship propulsion and thrust characteristics in ice can enable predictions of full-scale ice resistance without measuring the propeller thrust during sea trials. Measuring propeller revolutions,ship speed, and the power delivered to propellers could be sufficient to determine the propeller thrust of the vessel. At present, significant difficulties arise in determining the thrust of icebreakers and ice-class ships in ice conditions. These challenges are related to the fact that the traditional system of propeller/hull interaction coefficients does not function correctly in ice conditions. The wake fraction becomes negative and tends to minus infinity starting from a certain value of the propeller advance coefficient. This issue prevents accurate determination of the performance characteristics, thrust, and rotational speed of the propulsors. In this study, an alternative system of propeller/hull interaction coefficients for ice is proposed. It enables the calculation of all propulsion parameters in ice based on standard hydrodynamic tests with selfpropulsion models. An experimental method is developed to determine alternative propeller/hull interaction coefficients. A prediction method is suggested to determine propulsion performance in ice based on the alternative interaction coefficient system. A case study applying the propulsion prediction method for ice conditions is provided. This study also discusses the following issues of ship operation in ice: the scale effect of icebreaker propellers and the prospects for introducing an ice interaction coefficient.展开更多
文摘An energetic binder based on hydroxyl-terminated polybutadiene(HTPB),doped with different ratios of nitrocellulose(NC)(10%,20%,30%,and 50%),was developed to study the effect of NC doping on the thermal decomposition behavior of a composite propellant(CP)comprising ammonium nitrate(AN)as an oxidizer and magnesium(Mg)as a fuel.Optimization of the propellant formulation was conducted using Chemical Equilibrium with Applications-National Aeronautics and Space Administration(CEA-NASA)software,which demonstrated an increase in specific impulse by 12.09 s when the binder contained 50%NC.Fourier-transform infrared spectroscopy(FTIR)analysis confirmed the excellent compatibility between the components,and density measurements revealed an increase of 6.4%with a higher NC content.Morphological analysis using optical microscopy showed that NC doping improved the uniformity and compactness of the surface,reduced cavities,and achieved a more homogeneous particle distribution.Differential scanning calorimetry(DSC)analysis indicated a decrease in the decomposition temperature of the propellant as the NC content increased,while kinetic studies revealed a 48.68%reduction in the activation energy when 50%NC was incorporated into the binder.These findings suggest that the addition of NC enhances combustion efficiency and improves overall propellant performance.This study highlights the potential of the new HTPB-NC energetic binder as a promising approach for advancing solid propellant technology.
文摘When older stocks of ammunition are fielded for use, propellant degradation may be of concern.Degraded propellants may result in either increased or decreased chamber pressures, depending on formulation(thus deviating from expected performance), or in the worst-case scenario, auto-ignition.Data is sparse regarding propellants aged naturally in manufactured ammunition. Propellant harvested from 1953 U S. military 30-06 M2 AP rifle cartridges and from 2012 U S. military M855A1 rifle cartridgs was evaluated using thermochemical techniques and field testing. Thermochemical results were also compared with two 2022-era ball propellants(Winchester 748 and Hodgdon BL-C(2)). Thermal analysis demonstrated similar energy densities between the 1953, 2012, and ca. 2022-era propellants,with minor changes in activation energy, suggesting slightly decreased propellant thermal stability in the1953 propellant. Chemical analysis supported this observation, with slightly decreased levels of stabilizer(still above accepted minimums) and increased levels of stabilizer byproducts in the 1953 propellant. For field testing, 0.223 Remington rifle cartridges were prepared for the 1953 and 2012 propellants utilizing the same match-grade components and a volume of the respective propellant to result in a muzzle velocity around 800 m/s. Accuracy characteristics and variation in projectile velocity were evaluated in a standardized competition course of fire. For each propellant, 20 rounds were shot from one bolt action rifle with a 1 in 8 inches twist, and 20 rounds were shot from another with a 1 in 7 inches twist. Results showed that the 1953-era propellant demonstrated comparable standard deviations in velocity and ontarget precision to the 2012-era propellant, and both resulted in comparable standard deviations in velocity and on-target performance to a modern extruded commercial reloading propellant.
基金supported by the National Natural Science Foundation of China(Nos.51576097,51976089)the Funding for Outstanding Doctoral Dissertation in Nanjing University of Aeronautics and Astronautics,China(No.BCXJ24-05)the Aeronautical Science Foundation of China(No.2023L060052001).
文摘Feasible and accurate acoustic modeling of external and internal aircraft environments is essential for designing low-noise multi-propeller aircraft.This work proposes a novel sound source equivalent approach using Lighthill's sound sources(monopole and dipole point sources)for simulating propeller noise.It establishes data transmission interfaces between aerodynamic acoustics and acoustic-solid coupling.Equations are expanded from acoustic pressure to monopole amplitude and dipole moment vector.The basic assumption is that the propeller noise has similar spatial radiation directivity as the sound point source.The radiation relationships are explicitly built between harmonic propeller noise and dipole sources at cabin cross-sections,and between harmonic propeller noise and monopole sources along cabin longitudinal sections.External acoustic pressure distributions of cabin noise are calculated using Unsteady Reynolds-Averaged Navier-Stokes(URANS)and Ffowcs Williams-Hawkings(FW-H)approach.Interior noise is calculated using frequency domain acoustic-solid coupling.Sound source equivalent approach is used to calculate the equivalent intensity of monopole or dipole point sources for external excitation.To assess accuracy of the proposed approach,both external and interior noise of a turboprop aircraft with four sixbladed propellers are calculated and compared against flight trial results of a C-130J-30 Hercules.The turboprop aircraft adopts the same size parameters as the C-130J-30 Hercules.The present frequency domain acoustic approach is accurate for interior cabin noise.It is beneficial for enhancing the design of the low-noise turboprop aircraft.
基金support of the National Natural Science Foundation of China(No.12372221)is acknowledged.
文摘In this study,we introduce a deep generative model,named Multi-Species Generative Adversarial Network(MS-GAN),which is developed to extract the low-dimensional manifold of three-dimensional multi-species surfaces.In the development of MS-GAN,we extend the freeform deformation by incorporating principal component analysis to increase the non-linear deformation ability while maintaining geometric smoothness.The implicit information of multiple baselines is embedded in the feature extraction layers,to enhance the diversity and parameterization of multi-species dataset.Furthermore,Wasserstein GAN with a gradient penalty is used to ensure the stability and convergence of the training networks.Two experiments,ruled surfaces and propeller blade surfaces,are performed to demonstrate the advantages and superiorities of MS-GAN.
基金Supported by the National Key R&D Program of China(2022YFB3303500).
文摘Numerical simulations were conducted on a 10-blade Sevik rotor ingesting wake downstream of two turbulence-generating grids.These simulations were based on implicit large-eddy simulation(ILES)and the boundary data immersion method(BDIM)for compressible flows,which were solved using a fully self-programmed Fortran code.Results show that the predicted thrust spectrum aligns closely with the experimental measurements.In addition,it captures the thrust dipole directivity of the noise around the rotating propeller due to random pressure pulsations on the blades,as well as the flow structures simultaneously.Furthermore,the differences in the statistical characteristics,flow structures,and low-frequency broadband thrust spectra due to different turbulence levels were investigated.This analysis indicates that the interaction between the upstream,which is characterized by a lower turbulence level and a higher turbulent length of scale,and the rotating propeller results in a lower amplitude in force spectra and a slight increase in the scale of tip vortices.
基金supported by the National Key Research and Development Program of China(Grant No.2022YFE0107000)the Fundamental Research Funds for the Central Universities(Grant No.HYGJXM202319).
文摘Polar marine equipment plays an important role in Arctic engineering,especially in the development of polar ships and ice-class propellers.When polar ships navigate in brash ice channels,the brash ice not only increases resistance but also has adverse effects on their propulsion performance.On the basis of coupled computational fluid dynamics(CFD)and the discrete element method(DEM),this paper aims to numerically investigate the resistance and propulsion performance of a polar in a brash ice channel while considering the rotation status of the propeller by both experimental and numerical methods.Both ship resistance and ice motion under Froude numbers of 0.0557,0.0696,0.0836,0.975,and 0.1114 are studied when the propeller does not rotate.The influences of the rotating propeller on the ice brash resistance and flow are discussed.The thrust due to the propeller and ice resistance in the equilibrium state are also predicted.The errors between the thrust and total resistance are approximately 1.0%,and the maximum error between the simulated and predicted total resistance is 3.7%,which validates the CFD-DEM coupling method quite well.This work could provide a theoretical basis for the initial design of polar ships with low ice class notation and assist in planning navigation for merchant polar ships in brash ice fields.
基金Supporting by the project‘FILE NO.CRG/2022/001718’.
文摘Understanding the behaviour of composite marine propellers during operating conditions is a need of the present era since they emerge as a potential replacement for conventional propeller materials such as metals or alloys.They offer several benefits,such as high specific strength,low corrosion,delayed cavitation,improved dynamic stability,reduced noise levels,and overall energy efficiency.In addition,composite materials undergo passive deformation,termed as“bend-twist effect”,under hydrodynamic loads due to their inherent flexibility and anisotropy.Although performance analysis methods were developed in the past for marine propellers,there is a significant lack of literature on composite propellers.This article discusses the recent advancements in experimental and numerical modelling,state-of-the-art computational technologies,and mutated mathematical models that aid in designing,analysing,and optimising composite marine propellers.In the initial sections,performance evaluation methods and challenges with the existing propeller materials are discussed.Thereafter,the benefits of composite propellers are critically reviewed.Numerical and experimental FSI coupling methods,cavitation performance,the effect of stacking sequence,and acoustic measurements are some critical areas discussed in detail.A two-way FSI-coupled simulation was conducted in a non-cavitating regime for four advanced ratios and compared with the literature results.Finally,the scope for future improvements and conclusions are mentioned.
基金supported by the National Natural Science Foundation of China(Nos.U2441284 and 22375164)the Innovation Foundation for Doctor Dissertation of Northwestern Polytechnical University,China(No.CX2024042)。
文摘Aluminum-water(Al-H_(2)O)propellants represent an innovative class of solid propellants characterized by low cost and minimal signal signature.However,conventional formulations are hindered by significant aluminum(Al)agglomeration,leading to reduced combustion efficiency and substantial residues.This study introduces a method for modifying Al powder with Polyvinylidene Fluoride(PVDF)to enhance the performance of Al-H_(2)O propellants by mitigating agglomeration during combustion.Experimental methodologies,including thermogravimetric analysis under ambient-pressure nitrogen atmosphere and laser ignition tests,were employed to investigate the influence of varying PVDF content on the combustion characteristics of the propellants.Furthermore,the effect of PVDF on motor performance was systematically evaluated through laboratoryscale Solid Rocket Motor(SRM)tests.The results demonstrate that the addition of 7.5%PVDF significantly enhances the burning rate from 1.12 mm/s to 3.78 mm/s and reduces the mean particle size of condensed combustion products from 699μm to 527μm.Combustion efficiency rises from88.57%to 94.51%,while injection efficiency improves significantly from 30.45%to 70.45%.SRM tests further demonstrate an increase in combustion chamber pressure from 0.17 MPa to 0.58 MPa.A dynamic agglomeration model explains these improvements,attributing reduced agglomeration to enhanced aerodynamic forces and a thinner melting layer,while increased gas yield improves injection performance.This study highlights PVDF's potential in advancing Al-H_(2)O propellants by improving combustion and injection efficiency.
基金supported by the National Science and Technology Major Project,China(No.Y2019-I-0018-0017)the National Natural Science Foundation of China(No.11602200)+1 种基金Hunan Innovative Province Construction Special Fund,China(No.2021GK1020)the Priority Academic Program Development of Jiangsu Higher Education Institutions,China。
文摘Propeller design is a highly intricate and interdisciplinary task that necessitates careful trade-offs between radiated noise levels and aerodynamic efficiency.To achieve efficient trade-off designs,an enhanced on-the-fly unsteady adjoint-based aerodynamic and aeroacoustic optimization methodology is developed,which maintains the fidelity of the Navier-Stokes solution for unsteady flow and of the moving-medium Ffowcs Williams-Hawkings(FW-H)formulation for capturing tonal noise.Furthermore,this on-the-fly approach enables a unified architecture for discreteadjoint sensitivity analysis encompassing both aerodynamics and aeroacoustics,facilitating effective multi-objective weighted optimizations.Subsequently,this proposed methodology is applied to perform trade-off optimizations between aerodynamics and aeroacoustics for a propeller by employing varying weighting factors to comprehend their influence on optimal configurations.The results demonstrate a positive correlation between efficiency and noise sensitivities,and thus indicate an inherent synchronicity where pursing noise reduction through purely aeroacoustic optimization inevitably entails sacrificing aerodynamic efficiency.However,by effectively incorporating appropriate weighting factors(recommended to range from 0.25 to 0.5)into the multi-objective function combined with both aerodynamics and aeroacoustics,it becomes feasible to achieve efficiency enhancement and noise reduction simultaneously.Key findings show that reducing blade planform size and equipping“rotated-S”shaped airfoil profiles in the tip region can effectively restrain noise levels while maintaining aerodynamic performance.
基金supported in part by the Equipment Development Pre-research Project funded by Equipment Development Department,PRC under Grant No.50923010501Fundamental Research Program of Shenyang Institute of Automation(SIA),Chinese Academy of Sciencess under Grant No.355060201。
文摘Bonding quality at the interface of solid propellant grains is crucial for the reliability and safety of solid rocket motors.Although bonding reliability is influenced by numerous factors,the lack of quantitative characterization of interface debonding mechanisms and the challenge of identifying key factors have made precise control of process variables difficult,resulting in unpredictable failure risks.This paper presents an improved fuzzy failure probability evaluation method that combines fuzzy fault tree analysis with expert knowledge,transforming process data into fuzzy failure probability to accurately assess debonding probabilities.The predictive model is constructed through a general regression neural network and optimized using the particle swarm optimization algorithm.Sensitivity analysis is conducted to identify key decision variables,including normal force,grain rotation speed,and adhesive weight,which are verified experimentally.Compared with classical models,the maximum error margin of the constructed reliability prediction model is only 0.02%,and it has high stability.The experimental results indicate that the main factors affecting debonding are processing roughness and coating uniformity.Controlling the key decision variable as the median resulted in a maximum increase of 200.7%in bonding strength.The feasibility of the improved method has been verified,confirming that identifying key decision variables has the ability to improve bonding reliability.The proposed method simplifies the evaluation of propellant interface bonding reliability under complex conditions by quantifying the relationship between process parameters and failure risk,enabling targeted management of key decision variables.
基金supported by the National Natural Science Foundation of China(Nos.U2241250 and U2441284)。
文摘AP(Ammonium Perchlorate)and HMX(Octogen)are the two oxidizers most often used in Nitrate-Ester-Plasticized Polyether(NEPE)rocket propellants.How the AP–HMX ratio influences the agglomeration of NEPE propellants remains unclear.We experimentally investigated the effect of the AP–HMX ratio on the combustion and agglomeration of NEPE propellants using burning rate test,quenched surface analysis,microscopic observations,and the collection of condensed combustion products.It was found that with the decrease in AP content from 40wt%to 10wt%,the burning rate decreased from 14.2 mm/s to 9.2 mm/s because the adiabatic flame temperature of NEPE propellants decreased from 3828 K to 3736 K.Pockets bounded by AP particles appeared on the surface when AP content was 40wt%;however,the accumulations grew and covered the burning surface eventually as the AP–HMX ratio decreased.The time required for the accumulation to coalesce into agglomerates increased with decreasing AP content.Even with similar agglomerate sizes,the coalescence time increased by 83%when the AP content decreased from 40wt%to 30wt%.The agglomerate size in the Condensed Combustion Products(CCPs)increased from 100μm to 200μm,and the fraction of large agglomerations increased from 6.4%to 24.7%when the AP content decreased from 40wt%to 10wt%.Overall,the high flame temperature of the AP particles enhanced the decomposition of the surrounding binder,resulting in the rapid ejection of the aluminum particles into the gas,which had a separating effect on the accumulation,thus weakening the agglomeration.
基金supported by a grant from the Ministry of Research, Innovation and Digitization, UEFISCDI, Grant Nos. PN-IIIP2-2.1-PED-2021-1890, PN-IV-P6-6.3-SOL-2024-2-0254 and PNIV-P7-7.1-PTE-2024-0517, within PNCDI Ⅳ.
文摘This study represents an important step forward in the domain of additive manufacturing of energetic materials.It presents the successful formulation and fabrication by 3D printing of gun propellants using Fused Deposition Modeling(FDM)technology,highlighting the immense potential of this innovative approach.The use of FDM additive manufacturing technology to print gun propellants is a significant advancement due to its novel application in this field,which has not been previously reported.Through this study,the potential of FDM 3D-printing in the production of high-performance energetic composites is demonstrated,and also a new standard for manufacturability in this field can be established.The thermoplastic composites developed in this study are characterized by a notably high energetic solids content,comprising 70%hexogen(RDX)and 10%nitrocellulose(NC),which surpasses the conventional limit of 60%energetic solids typically achieved in stereolithography and light-curing 3D printing methods.The primary objective of the study was to optimize the formulation,enhance performance,and establish an equilibrium between printability and propellant efficacy.Among the three energetic for-mulations developed for 3D printing feedstock,only two were suitable for printing via the FDM tech-nique.Notably,the formulation consisting of 70%RDX,10%NC,and 20%polycaprolactone(PCL)emerged as the most advantageous option for gun propellants,owing to its exceptional processability,ease of printability,and high energetic performance.
基金supported by the China Postdoc-toral Science Foundation(No.2023M732495)the Shanxi Provincial Basic Research Program(Nos.202103021223180 and 202203021221120)the Deanship of Scientific Research at Northern Border University,Arar,KSA for funding this research work through the project number“NBU-FPEJ-2024-1261-02”.
文摘Low erosion high-energy propellant is one of the research directions to extend the weapon’s life and improve the weapon’s capability.In this study,energetic propellants containing different corrosion inhibitors were designed and prepared.Close bomb tests and semi-confined bomb experiments were used to investigate the burning and erosion properties of the propellants.The mechanism of erosion-reducing of titanium dioxide(titania,TiO_(2)),talc,and octaphenylsilsesquioxane(OPS)on the propellant was comparatively analyzed.The results show that OPS has the lowest burning rate and the longest burning time,and a minimized loss of fire force,with the best effect of explosion heat reduction.The erosion reduction efficiency of OPS is twice that of TiO_(2) and talc.The mechanism analysis shows that the decomposition and heat absorption of OPS can effectively reduce the thermal erosion effect and carbon erosion,and the gas produced can reduce the loss of chamber pressure and form a uniformly distributed nano-SiO_(2) protective layer.This solid-state high-efficiency organosilicon erosion inhibitor is an important guide for designing high-energy low-erosion gun propellants.
基金supported by the Research Funding of Hangzhou International Innovation Institute of Beihang University,China(No.2024KQ143).
文摘Distributed ducted propellers hold significant promise for propulsion systems in Advanced Air Mobility(AAM) due to their high efficiency, low noise, and enhanced redundancy and safety. However, a standardized benchmark for comparing the aerodynamic characteristics of different ducted propeller configurations remains lacking. Including additional ducted propellers can further complicate the flow field. This paper proposes an equivalent design method for ducted propellers based on the momentum theorem and similarity criteria, introducing three equivalent ducted propeller cases. Transient numerical simulations are conducted using the sliding mesh model. The three cases produce comparable thrust while consuming the same power, with the volume of distributed ducted propellers being reduced by over 29% compared to the single ducted propeller. This study investigates the effect of rotational frequency on aerodynamic performance under hovering conditions. While propeller performance demonstrates low sensitivity to variations in rotational frequency, duct performance exhibits high sensitivity. The research further examines how rotational frequency changes the pressure difference between the duct leading edge and trailing edge. Based on a sensitivity analysis of aerodynamic performance, the flow field mechanisms under different rotational consistency are examined for the case with one duct and two propellers. Differences in aerodynamic performance are attributed to the airflow velocity gradient differences at the duct leading edge and the flow separation characteristics on the crossing side. These findings are significant for enhancing the performance of distributed ducted propellers and improving aircraft controllability.
基金supported by the National Natural Science Foundation of China(Grant No.22175025)State Key Laboratory of Explosion Science and Safety Protection(Grant No.YBKT22-03)+1 种基金the Natural Science Foundation of Chongqing(Grant No.CSTB2023 NSCQ-LZX0098)the Chongqing Municipal Education Commis-sion(Grant No.KJZD-M202301404).
文摘Combustion catalyst is a key modifier for the performance of composite solid propellant.To exploit highefficiency combustion catalyst,a fascinating bimetallic metal-organic framework[MnCo(EIM)_(2)(DCA)_(2)]n(1)was constructed by an active dicyandiamide(DCA)linker,Mn^(2+),Co^(2+)centers,and an 1-ethylimidazole(EIM)ligand.1 possesses good thermal stability(Tp=205℃),high energy density(Eg=24.34 kJ/g,Ev=35.93 kJ/cm^(3)),and insensitivity to impact and frictional stimulus.The catalytic effects of 1 contrasted to monometallic coordination compounds Mn(EIM)_(4)(DCA)_(2)(2)and Co(EIM)_(4)(DCA)_(2)(3)on the thermal decomposition of AP/RDX composite were investigated by a DSC method.The decomposition peak temperatures of AP and RDX of the composite decreased to 335.8℃ and 206.4℃,respectively,and the corresponding activation energy decreased by 27.3%and 43.6%,respectively,which are better than the performances of monometallic complexes 2 and 3.The gas products in the whole thermal decomposition stage of the sample were measured by TG-MS and TG-IR,and the catalytic mechanism of 1 to AP/RDX was further analyzed.This work reveal potential application of bimetallic MOFs in the composite solid propellants.
基金supported by the National Natural Science Foundation of China(Grant Nos.22105156,22175139,22171136,and 22302156)the China National Science Fund for Distinguished Young Scholars(Grant No.22325504)。
文摘The simultaneous integration of high energy density,low sensitivity,and thermal stability in energetic materials has constituted a century-long scientific challenge.Herein,we address this through a dualzwitterionic electronic delocalization strategy,yielding TYX-3,the first bis-inner salt triazolo-tetrazine framework combining these mutually exclusive properties.Uniformπ-electron distribution and elevated bond dissociation energy confer exceptional thermal stability(T_(d)=365℃)with TATB-level insensitivity(impact sensitivity IS>40 J,friction sensitivity FS>360 N).Engineeredπ-stacked networks enable record density(1.99 g·cm^(-3))with detonation performance surpassing HMX benchmarks(detonation velocity 9315 m·s^(-1),detonation pressure 36.6 GPa).Practical implementation in Poly(3-nitratomethyl-3-methyloxetane)(PNMMFO)solid propellants demonstrates 5.4-fold safety enhancement over conventional HMX-based formulations while maintaining equivalent specific impulse.This work establishes a new design paradigm for energetic materials,overcoming the historical trade-offs between molecular stability and energy output through rational zwitterionic engineering.
文摘The efficacy of spacecraft propulsion systems significantly depends on the choice of propellant.This study utilized laser-induced breakdown spectroscopy(LIBS)to investigate the impact of different fuel types,fuel ratios,and laser energies on the plasma parameters of ammonium dinitramide(ADN)-based liquid propellants.Our findings suggest that 1-allyl-3-methylimidazolium dicyanamide(AMIMDCA)as a fuel choice led to higher plasma temperatures compared to methanol(CH_3OH)and hydroxyethyl hydrazine nitrate(HEHN)under the same experimental conditions.Optimization of the fuel ratio proved critical,and when the AMIMDCA ratio was 21wt.%the propellants could achieve the best propulsion performance.Increasing the incident laser energy not only enhanced the emission spectral intensity but also elevated the plasma temperature and electron density,thereby improving ablation efficiency.Notably,a combination of 100 mJ laser energy and 21wt.%AMIMDCA fuel produced a strong and stable plasma signal.This study contributes to our knowledge of pulsed laser micro-ablation in ADN-based liquid propellants,providing a useful optical diagnostic approach that can help refine the design and enhance the performance of spacecraft propulsion systems.
基金Project supported by the National Natural Science Foundation of China (No. 12302435)。
文摘As core components of precision-guided projectiles,projectile-borne components are highly susceptible to failure or even damage in complex high-overload environments,thereby significantly compromising launch reliability and safety.However,accurately characterizing the mechanical behavior of propellants remains challenging due to the limitations in the current internal ballistic theory and the constraints of large-scale artillery firing experiments.This complicates the high-precision numerical modeling of projectile launch,and obstructs investigations into the failure mechanisms of projectile-borne components.Therefore,this paper identifies propellant parameters using the computational inverse method under uncertainty,further establishes high-precision numerical models of projectile launch,and explores the failure mechanisms of projectile-borne components in complex high-overload environments.First,a projectile launching experiment is meticulously designed and executed to obtain the breech pressure and muzzle velocity.Then,a general simulation model is built,and the powder burn model is used to simulate the ignition and combustion.Subsequently,the propellant parameters are effectively identified with the computational inverse method by the combination of the experiments and simulations.A high-precision numerical model of projectile launch is modified with the parameters validated by another experiment,and the high-overload characteristics during projectile launch are thoroughly analyzed based on this model.Finally,the high-overload characteristics of projectile-borne components are analyzed to elucidate the stress variation laws and to reveal the failure mechanisms influenced by time and spatial locations.This research provides an effective method for perfectly identifying propellant parameters and building high-precision numerical models of projectile launch.Additionally,it provides significant guidance for the anti-high overload design and analysis of projectile-borne components.
基金supported by"the Fundamental Research Funds for the Central Universities",No.30924010503.
文摘With the development of high energy solid propellants,it is critical to evaluate the safety and power performance of solid propellants in the face of threats such as unmanned aerial vehicles(UAVs)when transporting and using them in contemporary warfare.An electric probe-type cylinder test measured the displacement-time behavior of NEPE high-energy solid propellant,and the parameters of the Jones-Wilkins-Lee(JWL)equation of state(EOS)were derived using particle swarm optimization(PSO)with the Gurney energy model.Further,the parameters of JWL-Miller EOS,determined through AUTODYN simulations,were validated by comparing airburst process simulations with experimental overpressure data.The study established a method for determining EOS parameters of high-energy propellants,achieving a high degree of accuracy.The derived parameters ensure precise modeling of propellant behavior,offering a reliable foundation for future applications in solid rocket motor performance optimization and safety assessment.
基金supported by a grant No. 23-19-00039 of Russian Research Fund “Theoretical basis and application tools for developing a system of intellectual fleet planning and support of decisions on Arctic navigation”。
文摘In designing modern vessels, calculating the propulsion performance of ships in ice is important, including propeller effective thrust, number of revolutions, consumed power, and ship speed. Such calculations allow for more accurate prediction of the ice performance of a designed ship and provide inputs for designers of ship power and automation systems. Preliminary calculations of ship propulsion and thrust characteristics in ice can enable predictions of full-scale ice resistance without measuring the propeller thrust during sea trials. Measuring propeller revolutions,ship speed, and the power delivered to propellers could be sufficient to determine the propeller thrust of the vessel. At present, significant difficulties arise in determining the thrust of icebreakers and ice-class ships in ice conditions. These challenges are related to the fact that the traditional system of propeller/hull interaction coefficients does not function correctly in ice conditions. The wake fraction becomes negative and tends to minus infinity starting from a certain value of the propeller advance coefficient. This issue prevents accurate determination of the performance characteristics, thrust, and rotational speed of the propulsors. In this study, an alternative system of propeller/hull interaction coefficients for ice is proposed. It enables the calculation of all propulsion parameters in ice based on standard hydrodynamic tests with selfpropulsion models. An experimental method is developed to determine alternative propeller/hull interaction coefficients. A prediction method is suggested to determine propulsion performance in ice based on the alternative interaction coefficient system. A case study applying the propulsion prediction method for ice conditions is provided. This study also discusses the following issues of ship operation in ice: the scale effect of icebreaker propellers and the prospects for introducing an ice interaction coefficient.
