Showing papers in "Journal of Propulsion Technology in 2012"

Design of Nonlinearly Compressed SERN Profile

Abstract: A procedure of nonlinearly compressed Single Expansion Ramp Nozzle(SERN) profile to cut down nozzle length was described.Comparisons were made among perfect nozzle,linearly compressed perfect nozzle and nonlinearly compressed perfect nozzle.The results show that the performance of nonlinearly compressed perfect nozzle is superior to linearly compressed perfect nozzle,and is inferior little to perfect nozzle.Another comparison is made between nonlinearly compressed truncated perfect nozzle and RAO nozzle,which shows that thrust ratio of RAO nozzle is 0.7% superior when flow is fully expanded.Under seriously over-expanded conditions(NPR=40),thrust ratio of nonlinearly compressed truncated perfect nozzle is 15.6% higher than that of RAO nozzle.

Sensibility Analysis of the Heat Flux in the Rotating Cavity

Abstract: Fluid-Structure-Interaction numerical method was applied to investigate the effects of the heat flux,which is presented as Chebyshev number,on the cooling of the rotating cavity.The cooling effect was also evaluated in accordance with an engineering evaluation system,which includes resistance evaluation,heat transfer evaluation and stress distribution evaluation,in order to ensure the safety of the turbine disk.The results show that the heat flux and the temperature distribution of the disk exhibited the influence of the variation of the heat flux on the outer rim of the disk which has no effect on the fluid structure of the rotating cavity and the flow resistance.Meanwhile,the thermal stress related to the temperature gradient can be affected.The stress level of the disk rises as increasing the Chebyshev number.The stress on the outer rim of the disk grows greater than it on the inner rim.The peak stress transfers from the centre to the disk rim while the Chebyshev number exceeds the critical value.Therefore,the change of the Chebyshev number has an effect on the failure probability of the turbine disk from both the material affordability and the working stress.

Development and Application of Hybrid Rocket Motor Technology: Overview and Prospect

Abstract: The characteristics,development history and current situation of hybrid rocket motor were presented.The potential application of hybrid rocket motor was analyzed based on the astronautic development in China.The hybrid rocket motor can be used in sounding rockets,low cost target drones and missiles,suborbital vehicles,large launch boosters,advanced upper stages and orbital transfer systems.Thus,the application prospect of hybrid rocket motor is extensive.The design method for hybrid sounding rocket in Beijing University of Aeronautics and Astronautics was summarized.The key technologies which affect the developments and applications of hybrid rocket motors were analyzed.

Multi-Model Predictive Sliding Mode Control for Aero-Engine

Abstract: A method of multi-model predictive sliding mode control was put forward for aero-engine with uncertainty and strong nonlinearity.The method drew lessons from the ideology of multi-model and predictive control.Firstly,the flight envelope of a certain aero-engine was plotted,and the state space multi-models were established.Secondly,predictive sliding mode controller was separately designed for each model.The algorithm predicted future sliding mode values and made rolling optimization and feed-back correction to get the control value.The current controller was chosen based on the match degree of outputs between the models and the aero-engine.Lastly,the stability condition was deduced.Simulation results show that the devised controller has good effect and restrains the influence of parameters perturbation and interfere.

Ablation Model of Silicon Insulator in Ramjet Combustion Chamber

Abstract: In order to evaluate the performance of silicon insulator in the second combustion chamber in ramjet,the ablation mechanics of silicon insulator was analyzed.A model considered fluid field of ramjet combustion has been established.The insulator ablation is due to air blowing,particle impingement and chemical reaction.The results of numerical simulation show that air blowing is the main factor causing insulator ablation.According to experimental data,the simulation results are acceptable.Part of insulator,downstream the inlet and on the two sides of the inlet are seriously ablated.To reduce insulator ablation in ramjet,it is needed to reduce the gas stream blowing-off impact.

Design of an Active Disturbance Rejection Decoupling Multivariable Control Scheme for Aero-Engine

Abstract: The way to design multivariable decoupling control scheme for aero-engine is mainly discussed.A new active disturbance rejection decoupling multivariable control algorithm is proposed based on the basic Active Disturbance Rejection Control(ADRC) principle.Firstly,a necessary static decoupling process is carried out to diminish static coupling among the controlled loops,and then the dynamic decoupling is realized to compensate each other by the nonlinear Extended System Observer(ESO).Then,an ADRC decoupling controller for turbofan engines is implemented and designed.It is compared with ALQR controller in full flight envelope through nonlinear simulation tests.Simulation results show clearly that the decoupling controller ADRC has good dynamic tracking performance and decoupling properties.

Experimental Verification of Aero-Engine Performance Seeking Control Based on the Hybrid Model and FSQP Algorithm

Abstract: The application of an onboard hybrid steady-state model and feasible sequential quadratic programming(FSQP) algorithm to aero-engine performance seeking control(PSC) was studied.On the one hand,the hybrid model was established to perform PSC instead of the component-level engine model,which was favorable for the reduction of time cost during optimization process.On the other hand,FSQP algorithm was used to find the global optimal solution in PSC,which could enhance optimization precision.Finally,through both digital simulation and semi-physical simulation,the minimum fuel-consumption mode and the maximum thrust mode were testified.The simulation results prove that the proposed method takes the real-time advantage with the acceptable optimization effectiveness in PSC.

Quantitative Analysis of Mixing and Combustion in the Scramjet Multi-Cavity Combustor

Abstract: In order to determine the influence of multi-cavity on mixing and combustion quantitatively,numerical investigation is carried out in a multi-cavity scramjet chamber with fuel equivalence ratio 0825 by large eddy simulation and flamelet modelMixing efficiency,combustion efficiency,and total pressure loss are comparedIn addition,wall pressure distribution and numerical schlieren are given to explain the observed resultsThe analysis shows that the mixing and combustion are improved for cavities mounted in both tandem and parallelThe maximum increase in mixing efficiency can be up to 2095% and 952%,while the combustion efficiency can increase up to 14% and 1694%Cavity mounting in tandem has the least total pressure loss in reacting case,while cavity mounting in parallel has the fast heat release,which is good for shortening chamber length

Numerical Investigation for Rotating Detonation Engine

Abstract: A reduced kinetic mechanism based on 19-step reaction and 9 species for mixtures of 2H2+O2+4N2 was used to simulate two-dimensional rotating detonation engine.The transport processes such as thermal conduction,diffusion and viscosity were omitted in the study.A method of piecewise fill was used to initiate rotating detonation wave.Results show that the method of forming detonation wave along one direction propagation was effective.Detailed analysis was given.Rotating detonation wave can make the flow field change periodically.Oblique shock wave and contact discontinuity are the main reason of flow field fluctuation at exit plane.Rotating detonation engine has high specific impulse and the fuel-based average specific impulse is 49131.5 N·s/kg.

Numerical Study on the Pre-Swirl Flow and Heat Transfer Characteristics of a Small Gas Turbine Blade

Abstract: Numerical study of flow and heat transfer characteristics in a rotating cascade of a small gas turbine,which adopted direct-transfer pre-swirl cooling system,was conducted by using ANSYS CFX 12.0.The effects of pre-swirl angle,cooling air Reynolds number and non-dimensional mass flow rate on the total pressure loss,cooling effectiveness and turbine efficiency were analyzed.The results show that total pressure losses of pre-swirl system and temperature distributions on blade are nearly same under various pre-swirl angles.Both cooling efficiency of blade and turbine efficiency increase with the diminishing of pre-swirl angle and non-dimensional mass flow rate or increasing of cooling air Reynolds number.

Numerical Study of Co-Axial Pilot and Main Module Combustor

Abstract: For combustion organization problems of the new high temperature rise combustor,a scheme including advanced effusion cooling structure and co-axial pilot and main module dome burning organization is designed.By solving the N-S equations,combined with non-premixed of PDF model,the computation is performed for the idle and design condition.The velocity and temperature field characteristics are obtained by numerical study,and the results show good partition burning organizational characteristics.

Numerical Study on the Impact of Fouling on Axial Compressor Stages

Abstract: Three-dimensional numerical method has been used in an investigation of NASA stage 35 which was a typically realistic compressor stage.Firstly,the numerical model was validated against the experimental data available from literature to check accuracy of the commercially computational fluid dynamic code.Computed performance maps showed good agreement with experimental data.Then,the model was used to simulate the effect of fouling on compressor stage in terms of imposing different combinations of added thickness and surface roughness levels.As a result,with surface roughness increasing,the compressor isentropic efficiency and total pressure ratio significantly reduced,mass flow rate decreased at both choked and near stall region,and surface roughness had little effect on compressor stable operating range.When the adding thickness increased,mass flow rate had a great drop at a choked point,but different at near stall point,and compressor stable operating range reduced obviously.The augment of surface roughness on rotor passage is the main fact of performance deterioration and it needs to be investigated.

Combined Model Based Nonlinear Predictive Control for Turboshaft Engine

Abstract: Aimed at turboshaft engine,in order to better satisfy the requirements of real-time control system and improve the control performance,a numerical-ARX combined model is constructed.The combined model has two parts,one is numerical steady-state nonlinear model and another is ARX dynamical linear model.By employing the combined model as prediction model,the nonlinear predictive controller is designed.Since the nonlinear programming problem is avoided,the real time of engine control system is guaranteed.Simulation results illustrated that with the change of collective pitch,power turbine speed can converge fast with high precision,and the overshooting is small.

Research on Hyperelastic Constitutive Model for HTPB Crosslinked Specimen

Abstract: HTPB crosslinked characteristic is the basis of the mechanical properties of composite propellantTo describe the properties of HTPB crosslinked specimen,by means of uniaxial tension test,the stress response characteristics under loading were studied,and hyperelastic constitutive model was establishedExperimental data was fitted to acquire hyperelastic constitutive parameters,and then compared Mooney-Rivlin with Ogden strain energy functionThe results show that the constitutive parameters of Mooney-Rivlin and more than second-order Ogden model can effectively characterize the mechanical behavior of HTPB crosslinked specimenOgden model can be used to predict the slight compression mechanical properties of HTPB crosslinked specimen

Aero-Engine State Variable Modeling Based on the Improved Particle Swarm Optimization

Abstract: For overcoming some insufficiencies of establishing the state variable model of aero-engine,the state variable model of aero-engine was proposed based on improved Particle Swarm Optimization(PSO).Firstly,the improvements of PSO were proposed.Each particle could adjust inertia coefficient dynamically based on own fitness value to balance search performance.The best position of the colony was updated in each generation real time.The random search was carried out near by the best individual to avoid plunging into local optima.Secondly,the improved algorithm was used to establish the aero-engine state variable model.The fitness function of PSO was established according to the principle that the aero-engine responses of the linear model should be in accordance with that of the nonlinear model at the same steady working point.The simulation results show that the established state variable model has the same responses as the nonlinear model for both the steady process and the dynamic process,and has high accuracy.And the established process for the model is simple and convenient.

Design Optimization for a Transonic Compressor with Implementation of Non-axisymmetric Endwall Contouring

Abstract: In order to explore whether non-axisymmetric end wall can effectively improve the performance of transonic compressor,a transonic compressor rotor was optimized with the implementation of non-axisymmetric hub endwall contouring by three dimension numerical simulation optimization platform.And this paper described how the compressor flow field was influenced by the non-axisymmetric endwall.The investigation reveals that the non-axisymmetric hub endwall can improve both the efficiency and pressure ratio of the transonic compressor.At the highest efficiency condition,the efficiency increases by 0.31% and the pressure ratio increases by 0.31%.The off-design performance of the compressor is improved.

Effects of Relative Geometry Position of Forward and Aft Blades on Performance of Tandem Rotor

Abstract: With transonic tandem rotor technology,fan stage rotor was accomplished,which produced total pressure ratio of 2.25 and responding loading coefficient(ψ=ΔH*/U2tip) of 0.55 at corrected tip speed of 381m/s.Based on the simulation results,the relative circumferential and axial position from forward blade to aft blade was analyzed in terms of the aerodynamic influence on tandem rotor performance and flow mechanism.The result indicates that the relative geometry position has great impact on blockage factor of aft blade as well as its axial velocity and relative flow angle at the inlet and outlet section,which changed the velocity triangle and results in the performance change of tandem rotor and respective blades.For the optimum choice of relative geometry,the tandem rotor would attain higher performance if there is 0.1~0.15 chord length overlap at chord-wise direction of forward blade and aft blade is closer to the forward blades pressure side.

Charring Model of Heat Transfer for Pulse Separation Device of Pulse Motor

Abstract: To investigate the heat transfer for pulse separation device(PSD)of pulse solid rocket motor,formulae of two charring models were developed and the results were compared with the actual engine test results.Charring model 1 has a 20% error,and charring model 2 has a 6.7% error,charring model 2 has a better accuracy.The heat conduction for PSD is computed and the results were compared for the depth and the temperature distribution of the PSD.The results does not consider charring has a 14.3% error,and the results consider charring has a 10% error.The results show that the charring model 2 gives a preferable explanation,and the simulated results agree well with the theoretical value when the charring is considered.The conclusions are helpful for designing pulse solid rocket motor configuration.

Application of Particle Swarm Optimization in Obtaining Solution of Aeroengine Component-Level Model

Abstract: The convergence of conventional solutions to nonlinear equation and component matching equations of aeroengine component model depends on the initial valuesBased on the peculiarity of nonlinear equation of the model,a hybrid Particle Swarm Optimization(PSO) algorithm HPSO1 is proposed,which integrates constriction factor,passive congregation factor and adaptive inertia weight on the basis of neighbor PSOAs for component matching equations,another hybrid Particle Swarm Optimization(PSO) algorithm HPSO2 is proposed,which integrates constriction factor,passive congregation factor on the basis of basic PSOThe simulation results demonstrate that both HPSO1 and HPSO2 overcome the dependence on initial values and they are effective in obtaining solution of aeroengine component-level model

Three-Dimensional Computation of the Interactions Between Shock Waves and Flame in a Confined Space

Abstract: The interaction between shock wave and flame occurs frequently in supersonic combustion and deflagration-to-detonation.To further understand the phenomenon,a computational study of the interactions between a planar incident shock wave and its reflected shock wave with a spherical flame was carried out by using the three-dimensional Navier-Stokes equations coupled with a chemical reaction,in which the combustion process was described by a single-step chemistry model.It can be found that the numerical simulation of the interactions between shock waves and flame agrees well with the experimental results in a confined space which embodies the three-dimensional effect of the numerical simulation.When the flame interacts with the incident shock wave,it deforms through Richtmyer-Meshkov instability.In this case,the physical process takes an important role and the flame expansion is relatively not obvious.While the deformed flame interacts with the reflected shock wave again,the flame expands rapidly,and maintains the heat release rate at a high level,which suggests that the chemistry reaction plays an important role in this stage.With the action of reflected shock wave,formation of complicated vortex structure of deformed flame can enhance the transport of heat and mass,and therefore can raise the burning rate.

Method of Rotor Vibration Fault Diagnosis from Process Power Spectrum Entropy and SVM

Abstract: For the complexity of rotor vibration process and the randomization of vibration fault generated,and difficulty for getting vibration fault samples,a fault diagnosis method based on power spectrum entropy and Support Vector Machine(SVM) with the SVM advantages of small sample,generalization and overall under information entropy was put forward.Four typical failures of rotor vibration was simulated based on rotor experiment and vibration fault data under more points and multi-speed is collected.The power spectrum entropy has been calculated through analyzing and processing the datum as fault vector,and the SVM model has been gained.And the validity of this method for distinguishing fault types,fault severity and fault location is proved to be effective by calculation and analysis of rotor vibration fault signals.

Integrated Design Methods and Performance Analyses of Osculating Inward Turning Cone Waverider Forebody Inlet(OICWI)

Abstract: The basic inward turning cone was designed by Methods of Characteristics which has straight initial shock wave and inner compression section shock wave canceled,flow parameters controllable and uniformity exit inner compression section.The intergrated Osculating Inward turning Cone Waverider Inlet(OICWI) design methods were developed based on the Osculating Inward turning Cone(OIC) waverider design methods.Based on the designed basic inward turning cone flow field and OICWI design methods,an OICWI was designed.The OICWI's performances were analyzed by numerical ways.The inviscid results show that numerical simulation results agree well with design results and flow field structures are consistent with basic inward turning cone flow field.The viscous results show that OICWI has high pressure recovery and flow capture characteristics.The flow field parameters are uniform in the inlet exit plane.

Aero-Engine Fault Diagnosis by a New Fast Multi-Class Support Vector Algorithm

Abstract: A new fast multi-class support vector algorithm was presented to solve the multi-class fault diagnosis problem for aero-engine at the condition of large-scale training set.According to the fast algorithm,a hierarchical support vector machine(H-SVM) was chosen for multi-class fault classification.Before SVM training,the training data are first clustered according to their class center Euclid distances with self-organizing feature mapping(SOFM) neural networks.The patterns which have close distances are divided into the same sub-classes to train.This ensures the H-SVM reasonable hierarchical construction and better generalization performance.The relative boundary vectors(RBVs) instead of all the original training samples are used for the training of the binary SVM fault classifiers in H-SVM.This pruning strategy decreases the number of final training sample significantly and can keep classification accuracy almost invariable.Accordingly,the training time is shortened greatly,compared with basic SVM classifier.Meanwhile,owing to the reduction of support vector number,the classification time is also reduced.When a serious sample aliasing exists,the aliasing sample points which are not the same class are eliminated before the relative boundary vectors are computed.Besides,the samples near the relative boundary vectors are selected for SVM training in order to prevent the loss of some key sample points resulted from aliasing.This can improve classification accuracy effectively.A simulation example to classify 5 classes of combination fault of a turbojet engine is finished: the total fault classification accuracy reaches 91.2% and the maximum training time of all the binary SVMs is only 16.20% of basic SVM classifier.When the original training sample number is increased to 7500,the final training sample number after pruning is reduced to 3.05% of basic SVM.Simulation results show that this fast multi-class support vector algorithm is effective,reliable and easy to be implemented for engineering application.

Effects of Rotational Speed Ratio on Stability Boundary of Contra-Rotating Compressor

Abstract: The effects of rotational speed ratio on stability of two-stage contra-rotating compressors with the numeral method were studied.The effect law of rotational speed ratio on stall boundary and block boundary was analyzed.The stability of rotors in different rotational speed ratio was studied.The results show that:(1) when the rotational speed ratio R2:R11.0,the stall boundary and block boundary will deflect to low flow direction with increasing the rotational speed ratio.(2) When the rotational speed ratio R2:R11.0,the stall boundary will not change,but the block boundary will deflect to low flow direction with increasing the rotational speed ratio.(3) The variation of rotational speed of the first rotor has strong effect on the performance of the second rotor.But the speed variation of the second rotor has little effect on the performance of the first rotor.(4)The factors resulting in destabilization of contra-rotating compressor will differ with different rotational speed ratio.

Development and Reduction of N-Decane Detailed Combustion Reaction Mechanism

Abstract: The n-decane combustion mechanism containing 388 species and 2226 reactions was developed based on the combustion mechanism automating generation program ReaxGen.The ignition delay time obtained under different pressure and temperature was compared with the experimental value.Finally,different skeletal mechanisms were generated through Direct Relation Graph(DRG).It demonstrated that the detailed combustion mechanism of n-decane can well simulate the ignition process,and the ignition delay data agreed well with experimental results if temperature exceeded 1000K.It proved that the Reaxgen-Combustion program was credible for alkane Hydrocarbon.The 62-species 422-reactions skeletal mechanism generated by DRG gave good results with detailed mechanism,and the species and reaction number was decreased by 84% and 81%,respectively.The calculational time was reduced vastly,and the skeletal mechanism can be used for further CFD application and reduction.

Experimental Study on Vortex-Cooled Thrust Chamber

Abstract: The vortex-cooled thrust chamber is an alternative cooling approach that can potentially offer additional benefits and design flexibility for liquid propellant thrust chambers.Based on the theoretical analysis and numerical simulation,a vortex-cooled thrust chamber for experiment using GH2/GO2 was designed.Cold flow and hot-fire tests were conducted.Without using other cooling methods,a 20-second hot-fire test was accomplished.The results of the investigation indicate that the vortex-cooled thrust chamber operates in steady-state and the GO2 forms the effective cooling vortex.The temperature increase of exterior surface of the chamber wall is 5K.In addition,the nozzle is protected effectively by cold gas film introduced by a portion of GO2.

Experiment of the Algorithm of Detecting the Stall Inception for the Subsonic Compressor

Abstract: To study an effective algorithm of detecting the stall inception signal for the axial compressor,the subsonic axial-flow isolated rotor was gradually pushed to stall at the different rotor speed to measure dynamic pressure signal at the different axial position of blade tips.Then the test data with the autocorrelation analysis and the variance analysis was studied.Test data presented show that the compressor stall is caused by the spike and the stall inception signal can be detected obviously near the rotor leading edge.Finally,the reaction time of autocorrelation analysis is longer than that of the variance analysis for the compressor.Thus,autocorrelation analysis is more effective to detect the stall inception.

Response Analysis on Aero-Engine Dual-Rotor System Under Random Excitation

Abstract: Aero-engine dual-rotor system is subject to unpredictable excitation,resulting in the random vibration.In order to study this phenomenon,the motion equation of the unbalanced dual-rotor system subjected to random excitation is established.Using pseudo-excitation method,the power spectral density(PSD) of displacement of the dual-rotor system subjected to random excitation is calculated,and the dynamic characteristics of the structure are studied.The researches show that with the increasing of the stiffness coefficient of the intershaft bearing,the natural frequency of the system increases and tend to a constant value.At the same time,the peak of the PSD of displacement caused by external random force decreases and tends to an infinitesimal,while the peak of the PSD of displacement caused by the system coupling effect increases to a peak,then decreases and tends to an infinitesimal after a certain stiffness.From the research,some measures are made for protecting dual-rotor aircraft engines from random vibration.

Carbon-Based Nozzle Thermochemical Erosion Characteristics in Solid Rocket Motors

Abstract: Based on the thermochemical erosion theory,a two-dimensional axisymmetric,coupled gas-solid-thermal numerical framework was established to predict the carbon-based nozzle erosion in solid rocket motorsNumerical simulations were carried out using the Wall Surface Reaction model of the commercial code FLUENT and the assumption whether the erosion process was chemical kinetics or diffusion controlled was not neededThe method was introduced to simulate the 70-lb BATES motor nozzle erosion and examine the effects of propellant composition,oxidizing species and chamber pressureThe calculated results agree well with experimental dataThe erosion rate follows the trend exhibited by the heat flux distribution,and peaks slightly upstream of the throatThe erosion rate decreases with increasing aluminum content and increases almost linearly with chamber pressureH2O is the dominant oxidizing species in dictating nozzle erosion

Investigation on a New Hypersonic Curved Shock 2-Dimensional Inlet Under Non-Uniform Coming Flow

Abstract: Based on a two-dimensional hypersonic curved-shock inlet with curved compression surface designed by a new wall pressure distribution,investigation was carried out through numerical simulation about the performance under non-uniform flow developed from 6 flat plates with different length,and compared the capability of tolerance to non-uniform flow with two conventional 2-D inlet.Especially,comparison was performed for the throat section flow distortion degree of three different compression form inlets at the design Mach number.The results indicate that two-dimensional hypersonic curved-shock inlet with curved compression surface designed by new wall pressure distribution is slightly influenced by non-uniform flow.The flow distortion index of throat section is smaller and can adjust the non-uniform flow to certain extent.