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Dynamic flight stability of a model dronefly in vertical flight

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Acta Mechanica Sinica 2014年第6期30卷 828-838页

作者： Chong Shen Mao Sun institute of Fluid Mechanics Beijing University of Aeronautics & Astronautics

The dynamic flight stability of a model dronefly in hovering and upward flight is *** method of computational fluid dynamics is used to compute the stability derivatives and the techniques of eigenvalue and eigenvector used to solve the equations of *** major finding is as *** flight of the model dronefly is unstable because of the existence of an unstable longitudinal and an unstable lateral natural mode of *** flight of the insect is also unstable,and the instability increases as the upward flight speed *** force generated by the upward flight velocity coupled with the disturbance in pitching angular velocity is responsible for the enhancement of the instability.

关键词： Insect vertical flight Flight stability Natural modes of motion

Design and Optimization of 3D Radial Slot Grain Configuration

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Chinese Journal of aeronautics 2010年第4期23卷 409-414页

作者： Ali Kamran School of astronautics Beijing University of Aeronautics and Astronautics

Upper stage solid rocket motors （SRMS） for launch vehicles require a highly efficient propulsion system. Grain design proves to be vital in terms of minimizing inert mass by adopting a high volumetric efficiency with minimum possible sliver. In this arti- cle, a methodology has been presented for designing three-dimensional （3D） grain configuration of radial slot for upper stage solid rocket motors. The design process involves parametric modeling of the geometry in computer aided design （CAD） software through dynamic variables that define the complex configuration. Grain bum back is achieved by making new surfaces at each web increment and calculating geometrical properties at each step. Geometrical calculations are based on volume and change-in-volume calculations. Equilibrium pressure method is used to calculate the internal ballistics. Genetic algorithm （GA） has been used as the optimizer because of its robustness and efficient capacity to explore the design space for global optimum solution and eliminate the requirement of an initial guess. Average thrust maximization under design constraints is the objective function.

关键词： solid rocket motors 3D grains radial slot configuration internal ballistics computer aided design heuristic optimization genetic algorithm

Influence of fuel injection position and equivalent mixture ratio on chemical non-equilibrium effects of single expansion ramp nozzle

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航空动力学报 2013年第9期28卷 2100-2111页

作者： CHENG Cheng WANG Yi-bai LIU Yu QIN Li-zi School of astronautics Beijing University of Aeronautics and Astronautics

Chemical non-equilibrium flow was investigated for the scramjet single expansion ramp nozzle(SERN)with a strut-based liquid-kerosene-fueled ***-dimensional Reynolds-averaged NavierStokes(RANS)equations were solved with the species conservation equation for continuous phase and the renormalization group(RNG)k-εturbulence *** discrete-phase model was analyzed for liquidkerosene droplets behavior in the supersonic *** was simulated by kerosene surrogate fuel's10-species and 13-step reduced reaction kinetics mechanism with use of Arrhenius's laminar finite rate *** studies were carried out to estimate the influence of different fuel injection positions and equivalent mixture ratios on the SERN chemical non-equilibrium *** calculation results show that the strutbased combustor enables convenient modeling of various SERN entry conditions,which is similar with many preceding investigations,by changing the injector strut position and controlling the mass flow rate of each *** non-equilibrium effects function in the whole SERN,especially in the initial flow expansion region,leads to obviously higher SERN performance of the non-equilibrium flow than that of the frozen ***,the distributed fuel injection pattern plays a significant role in enhancing the combustion efficiency in combustor,but weakening the chemical non-equilibrium effects funciton in ***,while the equivalent mixture ratio increases,the SERN thrust coefficient and lift coefficient rise gradually,and the increment of non-equilibrium flow in relation to frozen flow becomes higher as *** be specific,the equivalent mixture ratio is 0.6,the maximum increment of thrust coefficient and lift coefficient are 11.6% and 25% respectively.

关键词： scramjet engine single expansion ramp nozzle chemical non-equilibrium fuel injection position equivalent mixture ratio

Scaling of the flowfield in a combustion chamber with a gas-gas injector

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Chinese Physics B 2010年第1期19卷 575-588页

作者：汪小卫蔡国飙金平 School of astronautics Beijing University of Aeronautics and Astronautics

The scaling of the flowfield in a gas gas combustion chamber is investigated theoretically, numerically and experimentally. To obtain the scaling criterion of the gas-gas combustion flowfield, formulation analysis of the threedimensional （3D） Navier-Stokes equations for a gaseous multi-component mixing reaction flow is conducted and dimensional analysis on the gas gas combustion phenomena is also carried out. The criterion implies that the size and the pressure of the gas gas combustion chamber can be changed. Based on the criterion, multi-element injector chambers with different geometric sizes and at different chamber pressures ranging from 3 MPa to 20 MPa are numerically simulated. A multi-element injector chamber is designed and hot-fire tested at five chamber pressures from 1.64 MPa to 3.68 MPa. Wall temperature measurements are used to understand the similarity of combustion flowfields in the tests. The results have verified the similarities between combustion flowfields under different chamber pressures and geometries, with the criterion applied.

关键词： scaling similarity gas gas combustion experiment

Internal ballistic simulation of multi-burning-rate solid rocket motor based on parameterized feature CAD modelInternal ballistic simulation of multi-burning-rate solid rocket motor based on parameterized feature CAD model

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航空动力学报 2015年第12期30卷 3017-3028页

作者： CHEN Wei LIANG Guo-zhu School of astronautics Beijing University of Aeronautics and Astronautics

Internal ballistic simulation(IBS)method of multi-burning-rate solid rocket motor(SRM)was developed based on 3-D burning regression method by parameterized feature CAD model(PFCADM)and lumped parameter,in consideration of time-dependent,erosive-burning-effect from internal ballistic numerical *** driving multi-parameter CAD model based on PFCADM,the approach is capable of conducting the geometric regression simulation of various grain combinations of complex configurations with different burning *** suitably simplifying the internal ballistic numerical algorithm,the problems of coupling geometric regression simulation of sub-grains of different burning rates and high computational consumption of internal ballistic calculation were *** tri-burning-rate grain motor,which had been firing-tested,was used as the validation case of *** results show that,with the 3-D grain regression model and sufficient accurate internal ballistic algorithm,the method realizes IBS of the case in low computationalconsumption prediction of its performance within the accuracy of 2% during *** application of the method provides a practical approach to aid SRM design of multi-burning-rate grain.

关键词： solid rocket motor internal ballistic simulatio multi-burning-rate grain design unsteady flow

Experiments on film cooling with sonic injection into a supersonic flow

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航空动力学报 2015年第5期30卷 1084-1091页

作者： ZHANG Jia SUN Bing School of astronautics Beijing University of Aeronautics and Astronautics

Film cooling experiments with sonic injection were conducted to investigate the effects of the number of the injection holes,the mass flow ratio,and the hole spacing on the film cooling *** mainstream was obtained by the hydrogen-oxygen combustion,entering the experimental section at a Mach number of *** nitrogen with ambient temperature was injected into the experimental section at a sonic *** measured mainstream recovery temperature was approximately *** mass flow ratio was regulated by varying the nitrogen injection *** experimental results show that for the investigated cooling surface,the cooling effectiveness increases with the increase in the number of the injection holes with other parameters held *** a fixed cooling configuration,the cooling effectiveness increases with the increase in the mass flow *** from the subsonic film cooling,the optimal mass flow ratio is not *** the hole spacing is less than 4,no obvious difference is observed on the cooling effectiveness and lateral *** the mass flow ratio increasing further,this difference becomes much *** shock wave also has an effect on the cooling *** the incident point of the shock wave,the cooling effectiveness is lower than that in the case without the shock wave.

关键词： supersonic film cooling discrete hole film cooling effectiveness mass flow ratio hole spacing

Numerical simulation of axial liquid film cooling in rocket combustor

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航空动力学报 2013年第2期28卷 459-465页

作者： YANG Wei SUN Bing ZHENG Li-ming School of astronautics Beijing University of Aeronautics and Astronautics

Numerical simulation has been done for liquid film cooling in liquid rocket *** species of axial Navier-Stokes equations have been solved for liquid-film / hot-gas flow field,and k-εequations have been used for compressible turbulent *** results of the model agree well with the results of software *** results show that :(1) Liquid film can decrease the wall heat flux and temperature effectively,and the cold border area formed by the film covers the whole combustor and nozzle wall.(2) The turbulent viscosity is higher than the physical viscosity,and its biggest value is in the border area of the convergent area in *** effect of turbulent flow on the whole simulation field can not be ignored.(3) The mass fraction of kerosene at the film inlet is 1,but it decreases along the nozzle wall and achieves its lowest value at the ***,the mass fraction of kerosene near the wall is the biggest at any axial location.

关键词： liquid rocket engine liquid film cooling heat flux numerical simulation turbulent flow

Multi-phase flow effect on SRM nozzle flow field and thermal protection materials

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航空动力学报 2009年第10期24卷 2372-2378页

作者： SHAFQAT Wahab School of astronautics beijing University of aeronautics and astronautics

Multi-phase flow effect generated from the combustion of aluminum based composite propellant was performed on the thermal protection material of solid rocket motor(SRM) *** of alumina(Al2O3) particles from 5% to 10% was tried on SRM nozzle flow field to see the influence of multiphase flow on heat transfer computations.A coupled,time resolved CFD(computational fluid dynamics) approach was adopted to solve the conjugate problem of multi-phase fluid flow and heat transfer in the solid rocket motor *** governing equations are discretized by using the finite volume ***-Allmaras(S-A) turbulence model was *** computation was executed on the different models selected for the analysis to validate the temperature variation in the throat inserts and baking material of SRM *** for temperatures variations were also carried out at different expansion ratios of *** paper also characterized the advanced SRM nozzle composites material for their high thermo stability and their high thermo mechanical capabilities to make it more reliable simpler and lighter.

关键词： solid rocket motor nozzle multiphase flow thermal protection material temperature distribution finite volume method

Experimental investigations on separation control and flow structure around a circular cylinder with synthetic jet

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Science China(Technological Sciences) 2007年第5期50卷 550-559页

作者： WANG JinJun FENG LiHao XU ChaoJun Fluid Mechanics institute Beijing University of Aeronautics and Astronautics Beijing 100083 China Fluid Mechanics Institute Beijing University of Aeronautics and Astronautics Beijing 100083 China Fluid Mechanics Institute Beijing University of Aeronautics and Astronautics Beijing 100083 China

Circular cylinder separation control and flow structure influenced by the synthetic jet have been experimentally investigated in a water channel. The synthetic jet is- sues from a slot and ejects toward upstream from the front stagnation point of the cylinder. It has been found that, similar to the traditional synthetic jet which is po- sitioned near the separation point or inside the separation region, the present synthetic jet arrangement constitutes an efficient way to control flow separation of the circular cylinder, but with a different control mechanism. The present synthetic jet leads to an upstream displacement of the front stagnation point and the forma- tion of a vortex pair near both sides of the exit orifice. When ReU based on the synthetic jet average exit orifice velocity is about lower than 43, a closed envelope forms in front of the windward side of the cylinder during the blowing cycle of syn- thetic jet, which acts as an apparent modification for the cylinder configuration. When ReU is high enough, an open envelope forms upstream of the cylinder, and the flow around the cylinder becomes much energetic. Thus, regardless of ReU, the present synthetic jet can improve separation for flow around a circular cylinder. With regard to the leeward side, as ReU increases, the flow separation region be- hind the cylinder gradually disappears. The flow over cylinder may be fully attached when the open envelope forms upstream of the cylinder and ReU is greater than 344. Then, the flow past the cylinder will converge near the back stagnation point of the cylinder, where a new vortex pair shedding periodically is generated due to the high shear layer.

关键词： flow control, synthetic jet, flow around a cylinder, vortex structure