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Measurements of Water-Air flow Phenomena in a Chamber with a Rotating Shaft

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Journal of Thermal Science 2021年第1期30卷 242-247页

作者： TIUTIURSKI Paweł HERCEL Paulina TELEGA Janusz KARDAŚDariusz flow and combustion department Renewable Energy FacultyInstitute of Fluid Flow Machinery Polish Academy of SciencesFiszera 1480-231GdańskPoland flow and combustion department Experimental Aerodynamics FacultyInstitute of Fluid Flow Machinery Polish Academy of SciencesFiszera 1480-231GdańskPoland

The paper concerns the phenomena of the fluid film that occurs in the bearing chamber of an aircraft *** geometry of the system includes two concentric cylinders,between which there is a mixture of oil and *** fluid circulates in a closed *** rotary movement of the inner cylinder causes creation of the fluid film on the walls of the *** article proposes a measurement method that is allowing observation of this fluid film and,in particular,analysis of the movement of the air bubbles occurring in the *** own model of the bearing chamber with transparent walls was constructed for the *** the investigation,water was used instead of *** of the behaviour of the flow was possible thanks to video recordings made with the use of a fast-capture *** results presented in the paper include velocity magnitudes of the air bubbles in the fluid film in dependence on the rotational speed of the shaft and water volume fraction and with a range from 0.37 to 0.91 m/*** results presented in this article can be used for the bearing chamber numerical models validation.

关键词： bearing chamber measurements fluid film velocity two-phase flow

Storage life of silicone rubber sealing ring used in solid rocket motor

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Chinese Journal of Aeronautics 2014年第6期27卷 1469-1476页

作者： Liu Weikai He Guoqiang Science and Technology on combustion Internal Flow and Thermal-structure Laboratory Northwestern Polytechnical University

It is urgent to carry out detailed research on storage performance of rubber sealing ring to get the criterion for its storage life. This paper acquires material ageing regularity by theoretical analysis and experimental confirmation. On this condition, failure mode and failure criterion of typical sealing structure is studied, and the failure mechanism is found. Thus by analyzing the stress distribution, the relationship between ageing state and sealing condition is established. Rationalization proposal is put forward and storage life of sealing ring is evaluated. The research mentionedabove has special reference to the design of sealing structures and can provide reference for prolonging their service life.

关键词： Failure criterion Sealing ring Silicone rubber Solid rocket motor Storage life

Transition Modelling with the k-Ω Turbulence Model and an Intermittency Transport Equation

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Journal of Thermal Science 2004年第3期13卷 220-225页

作者： Koen LODEFIER Bart MERCI Chris De LANGHE Erik DICK Ghent University Dept. of Flow Heat and Combustion Mechanics Sint-Pietersnieuwstraat 41 B-9000 Gent BelgiumGhent University Dept. of Flow Heat and Combustion Mechanics Sint-Pietersnieuwstraat 41 B-9000 Gent BelgiumGhent University Dept. of Flow Heat and Combustion Mechanics Sint-Pietersnieuwstraat 41 B-9000 Gent BelgiumGhent University Dept. of Flow Heat and Combustion Mechanics Sint-Pietersnieuwstraat 41 B-9000 Gent Belgium

In gas turbine engines, laminar-turbulent transition occurs. However, generally, the turbulence models to describe such transition results in too early and too short transition. Combining a turbulence model with a description of intermittency, i.e. the fraction of time the flow is turbulent during the transition phase, can improve it. By letting grow the intermittency from zero to unity, start and evolution of transition can be imposed. In this paper, a method where a dynamic equation of intermittency combining with a two-equation k-ωturbulence model is described. This intermittency factor is a premultiplicator of the turbulent viscosity computed by the turbulence model. Following a suggestion by Menter et al.[1], the start of transition is computed based on local variables.

关键词： bypass transition intermittency SST turbulence model.

Application of a k-ε Model to Heat Transfer in Impinging flows

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Journal of Thermal Science 2004年第1期13卷 62-66页

作者： Bart Merci Chris De Langhe Koen Lodefier Erik Dick Ghent University Dept.of FlowHeat and Combustion MechanicsSint-Pietersnieuwstraat 41B-9000 GentBelgiumGhent UniversityDept.of FlowHeat and Combustion MechanicsSint-Pietersnieuwstraat 41B-9000 GentBelgiumGhent UniversityDept.of FlowHeat and Combustion MechanicsSint-Pietersnieuwstraat 41B-9000 GentBelgiumGhent UniversityDept.of FlowHeat and Combustion MechanicsSint-Pietersnieuwstraat 41B-9000 GentBelgium

Local heat transfer is predicted in turbulent axisymmetric jets, impinging onto a flat plate. A non-linear k-e model is used, in which both the constitutive law for the turbulent stresses and the transport equation for the turbulent dissipation rate e have an important contribution in the improved heat transfer predictions. The shape of the Nusselt number profiles, expressing dimensionless heat transfer, as well as the stagnation point value, are well predicted for different distances between the nozzle exit and the plate. Accurate flow field predictions are the basis for good heat transfer predictions. For a fixed Reynolds number, the influence of the nozzle-plate distance is well captured. For a fixed distance, the influence of the Reynolds number is correctly reproduced. Comparisons are made to a low-Reynolds standard k-e model and the v2-f model. A thorough discussion is found in [4]. Only a summary of those results is discussed here, while some new results are also presented.

关键词： local heat transfer impinging jets non-linear k-ε model.

Anti-sintering behavior and combustion process of aluminum nano particles coated with PTFE:A molecular dynamics study

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Defence Technology（防务技术） 2023年第6期24卷 46-57页

作者： Jun-peng Liu Hao-rui Zhang Qi-Long Yan Science and Technology on combustion Internal Flow and Thermostructure LaboratoryNorthwestern Polytechnical UniversityXi'an 710071China

The characteristic of easy sintering of aluminum nanoparticle(ANP)limits its application in solid *** ANP with fluoropolymer could effectively improve its combustion *** find out how the coating layer inhibits sintering and promotes complete combustion of particles from an atomic view,a comparative study has been done for bare ANP and PTFE coated ANP by using reactive molecular dynamics *** sintering process is quantified by shrinkage ratio and gyration *** results show that,at the same heating rate and combustion temperatures,bare ANPs are sintered together after the temperature exceeds the melting point of aluminum but the decomposition of PTFE coating layer pushes particles away and increases reaction surface area by producing small Al-F *** sintering of ANPs which are heated in PTFE is alleviated compared with particles heated in oxygen,but particles still sinter together due to the lack of intimate contact between PTFE and alumina *** effect of temperature on the combustion of PTFE coated ANPs is also studied from 1000 to3500 *** number density analysis shows the particles will not be sintered at any *** fluoride prefers diffusing to the external space and the remained particles are mainly composed of Al,C and *** ignition simulations are performed by adopting micro canonical *** the expansion of aluminum core and the melting of alumina shell,bare ANPs are sintered into a liquid particle *** PTFE coated ANPs,the volatilization of gaseous aluminum fluoride products continually endows particles opposite momentum.

关键词： Aluminum nanoparticle Sintering combustion Molecular dynamics simulation

Development of EPDM composites reinforced by CNTs@SiO_(2)for thermal protection systems of aerospace propulsion:Significant improvement in oxidation and ablation resistance properties

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Chinese Journal of Aeronautics 2024年第2期37卷 471-481页

作者： Li WANG Jiang LI Kang LI Yiwei WANG Chenyang MA Science and Technology on combustion Internal Flow and Thermal-Structure LaboratoryNorthwestern Polytechnical UniversityXi’an 710072China

Carbon Nanotubes(CNTs)reinforced Polymer-Matrix Composites(PMCs)is widely used as insulation materials in thermal protection system of aerospace ***,CNTs are prone to oxidation and have high thermal conductivities,which makes it difficult to improve the ablation resistance of insulation materials that contain ***_(2)was encapsulated onto the surface of CNTs(CNTs@SiO_(2)),which were then added to Ethylene Propylene Diene Monomer(EPDM)rubber to prepare the insulation *** analysis and ablation test were used to evaluate the resistance of the insulation materials to thermal oxidation and ***,scanning electron microscopy was performed to analyze their *** revealed that the addition of CNTs@SiO_(2)could visibly reduce the effects of hot corrosion and ablation on insulation *** C-CNTs@SiO_(2)-1 formulation had the best ablative ***,compared with the unencapsulated formulation(C-CNTs-10),the C-CNTs@SiO_(2)-1 formulation reduced the line ablation rate by 51%to 0.0130 mm/s after oxygen-acetylene ***,the ablation mechanism was investigated based on the effects of the CNTs@SiO_(2)additive on their ***,the improvement in ablation performance may be attributed to CNTs@SiO_(2)-induced decreases in thermal conductivity,improvement in the hot corrosion resistance in the char layer,and changes in the microstructure.

关键词： Polymer-Matrix Composites(PMCs) Carbon Nanotubes(CNTs) Thermal properties Ablation Oxidation

Characterization of an ionic liquid electrospray thruster with a porous ceramic emitter

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Plasma Science and Technology 2020年第9期22卷 66-74页

作者： Chong CHEN Maolin CHEN Haohao ZHOU combustion Internal Flow and Thennal-Structure LaboratoryNorthwestern Polytechnical UniversityXi’an 710072People’s Republic of China

An ionic liquid(IL)electrospray thruster was developed for application in micro-nano satellites or gravitational wave *** thruster employed a porous ceramic emitter with seven emitter strips located on its emission *** any liquid-supply device,IL was delivered through porous media to emitter strips via capillary *** emission sites then formed at the tip of each strip.A charged beam of up to 350μA(with a current density of 540μA cm^(-2))was stably produced in the negative ***,in the positive mode,a corona was observed which could prevent the thruster from emitting larger current.A time-of-flight mass spectrometer with significantly improved signal-to-noise ratio was built,which was used to obtain the mass distribution of the beam of the thruster.A retarding potential analysis was also *** test results showed that the thruster worked in the pure-ion regime,and delivered a maximum thrust of 67.1μN with specific impulses of 3952 s and 3117 s in the positive and negative modes,respectively.

关键词： electrospray thruster time-of-flight(TOF) retarding potential analysis(RPA)

The regulation of ferrocene-based catalysts on heat transfer in highpressure combustion of ammonium perchlorate/hydroxyl-terminated polybutadiene/aluminum composite propellants

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Defence Technology（防务技术） 2024年第5期35卷 174-186页

作者： Jinchao Han Songqi Hu Linlin Liu Science and Technology on combustion Internal Flow and Thermo-Structure LaboratoryNorthwestern Polytechnical UniversityXi'an 710072ShaanxiChina

The regulation of the burning rate pressure exponent for the ammonium perchlorate/hydroxylterminated polybutadiene/aluminum(AP/HTPB/Al)composite propellants under high pressures is a crucial step for its application in high-pressure solid rocket *** this work,the combustion characteristics of AP/HTPB/Al composite propellants containing ferrocene-based catalysts were investigated,including the burning rate,thermal behavior,the local heat transfer,and temperature profile in the range of 7-28 *** results showed that the exponent breaks were still observed in the propellants after the addition of positive catalysts(Ce-Fc-MOF),the burning rate inhibitor((Ferrocenylmethyl)trimethylammonium bromide,Fc Br)and the mixture of Fc Br/catocene(GFP).However,the characteristic pressure has increased,and the exponent decreased from 1.14 to 0.66,0.55,and 0.48 when the addition of Ce-FcMOF,Fc Br and Fc Br/GFP in the *** addition,the temperature in the first decomposition stage was increased by 7.50℃ and 11.40℃ for the AP/Fc Br mixture and the AP/Fc Br/GFP mixture,respectively,compared to the pure *** the other hand,the temperature in the second decomposition stage decreased by 48.30℃ and 81.70℃ for AP/Fc Br and AP/Fc Br/GFP mixtures,*** was also found that Fc Br might generate ammonia to cover the AP *** this case,a reaction between the methyl in Fc Br and perchloric acid caused more ammonia to appear at the AP surface,resulting in the suppression of ammonia *** addition,the coarse AP particles on the quenched surface were of a concave shape relative to the binder matrix under low and high pressures when the catalysts were *** the process,the decline at the AP/HTPB interface was only exhibited in the propellant with the addition of *** ratio of the gas-phase temperature gradient of the propellants containing catalysts was reduced significantly below and above the characteristic pressure,rather than 3.6 times of the di

关键词： AP/HTPB/Al propellants Heat transfer High-pressure combustion Ferrocene-based catalysts Pressure exponent

Investigation on plume interference effect of solid propellant micro-thruster

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航空动力学报 2011年第9期26卷 2027-2031页

作者： ZHANG Bin MAO Gen-wang HU Song-qi CHEN Mao-lin （National Key Laboratory of combustion Flow and Thermo-Structure College of Astronautics Northwestern Polytechnical University Xi＇an 710072 China

The three-dimensional numerical simulation of two-phase plume flow of solid propellant micro-thrusters was *** it was used to investigate the plume interference effect by combining the direct simulation Monte Carlo(DSMC) method for multi-component gas flow with the two-way coupling model for two-phase rarefied *** different space between the two micro-thrusters and different wall temperature,the plume interference effect was analyzed *** results show that under the plume interference effect the gas is compressed and the flow direction is changed,which resulted in the increasing of gas pressure and temperature;solid phase made no significant effect on the flow parameters of gas phase;with the rising of the space between the two micro-thrusters,the maximum pressure decreased and the maximum temperature increased in the domain under the plume interference effect;the wall temperature could influence the temperature of the gas which is extremely close to the wall,but not the gas pressure.

关键词： solid propellant micro-thruster plume interference effect two-phase plume flow catalytic decomposition specific impulse