Showing papers in "Journal of Propulsion Technology in 2009"

Rotating cavitation of the high-speed rotational inducer of LPRE

Abstract: An inducer as a key component raises suction performance of liquid propellant rocket engine pump.However,rotating cavitation appeared in the high-speed rotational inducer may sometimes significantly influence the normal operation of turbopump.A mixture model based on Rayleigh-Plesset equation is applied to calculate unsteady cavitating flows in an inducer 2D cascade.A rotating cavitation with propagation speed ratio approximately form 1.1 to 1.4,is simulated and its internal mechanism is analyzed.From a hydraulic test,time-frequency spectral analysis technique for non-stationary signal is employed to capture the features of rotating cavitation under different conditions.The occurrence region and other characteristics of this unsteady phenomenon are also observed.

Effect of coated and agglomerated boron on combustion characteristics of boron-based fuel-rich propellants

Abstract: The effects of various factors,such as the content of the agglomerated boron,the types and contents of coating materials on the combustion characteristics of the boron-based fuel-rich propellants were experimentally investigated.The results show that propellants with agglomerated boron give higher burning rate and pressure exponent.Propellant with low AP coating gives higher burning rate at low pressure and poorer pressure exponent.High AP coating gives higher pressure exponent and poorer burning rate at low pressure.Coating of LiF can improve the burning rate of boron-based propellant at low pressure.While higher LiF coating has negative effect on pressure exponent.

Parametric sensitivity analysis of scramjet nozzle configuration

Abstract: The methods of orthogonal latin squares design and variance analysis were introduced to investigate the aero-propulsive performance of nozzle, reviewing the influence of design variables on its performance The results show that the reflection angle of the nozzle upper wall and the length of the lower wall have remarkable influence on nozzle performance Meanwhile, in order to improve the thrust and pitching moment, the reflection angle of the nozzle upper wall should be smaller and the length of the lower wall and the flap angle should be larger In order to improve the lift, the reflection angle of the nozzle upper wall should be larger and the length of the lower should be smaller

Fault diagnosis of aero-engine bearings based on wavelet package analysis

Abstract: Vibration analysis is widely used in the condition monitoring and fault detection of the rolling elernent bearings.When locally scathed,the bearings would bump the other parts periodically with the result that the seasonal impulses come into being.With enough broad band to overcast each connatural frequency of the whole bearings,the impulses necessarily arose each connatural vibrations and thereby the stationary vibrations turn into transients.Although well localized in frequency,the Fourier transform was localized none too well in time which makes it a cumbersome tool for transients.Moreover,a local time-frequency composition as the windowed Fourier transform,the short-time Fourier transform namely,it has the same resolution across the time-frequency plane because of the same spread of the window on which the resolution depends.If using conventional method for the vibration signal analysis,the non-stationary signals are hard to analyze.This paper investigates rolling bearings fault diagnosis based on wavelet analysis method,and the surface damnification fault signals are diagnosed by using the frequency domain analysis method of wavelet package decomposition.Experimental results show that the analysis methods of wavelet transform are reliable and accurate.They are useful for the condition monitoring and fault diagnosis to aero-engine rolling bearings.

Numerical investigation of the flow mechanisms of compressor stall delay through end wall self recirculation

Abstract: End wall self recirculation is known as an active method to control stall in axial compressorsIt is implemented by combining injection and bleed on the compressor shroud and has the characteristic of injection or bleed quantity self adjusting with the compressor work point varyingEffect of end wall self recirculation on the performance of an axial-flow rotor was performed with the help of numerical methodThe numerical results show that end wall self recirculation method can not only suspend the stall effectively but also improve the compressor efficiency appreciablyThe fundamental flow mechanism of end wall self recirculation reforming the compressor performance was obtained by detailed analyzing the flow fieid at the blade tip

Numerical simulation of continuous rotating detonation engine in column coordinate

Abstract: A two-dimensional numerical simulation of the continuous rotating detonation engine (CRDE) was carried out with two-step chimerical kinetic model. Multi-cycle process of continuous rotating detonation(CRDE) was numerically obtained on coaxial cylinder. Some key problems about CRDE, such as fuel injection, pre-combustion, detonation structure and propagating velocity were discussed. The simulation results agree well with the previous experiment results. A detonation wave can continuously propagate around at about 2400 m/s with maximum injection velocity of 1400 m/s. A CRDE keeps a high frequency of about 2300 Hz in this simulated combustor of 7 mm in radius.

Numerical simulation of performance for turbine based combined cycle propulsion system

Abstract: The arrangement of turbine based combined cycle engines were investigatedCo-axial and tandem configuration was selected as a turbofan-ram combined engineThe design parameters of both turbofan engine and ramjet were laid out,and the rules were expounded to explain how to ascertain the transition point of operation modeBased on a modular structure code,the performance characteristic of turbo-ramjet was simulated by numerical method

Interfacial property of the filler/binder matrix for HTPB propellant under constant strain

Abstract: To investigate the main failure reason of HTPB propellant under constant strain,the macroscopical mechanical property,microscosmic interfacial properties and their relationship were studied.The macroscopical mechanical properties were measured by uniaxial tensile testing.The microscosmic interfacial adhesive properties were characterized using Scanning Electron Microscope(SEM) and measuring the contact angle between the test liquids and filler AP or binder matrix.The results show that the maximum elongation are decreased,the interfacial adhesive between the filler and binder matrix are deteriorated,the work of adhesion(Wa) are decreased and the interfacial tension(γsl) increased along with the aging time.The interfacial adhesive property between the filler and binder matrix of HTPB propellant can be characterized by Wa and γsl.The value of the work of adhesion under constant strain is lower,and the interfacial tension is higher than that under zero strain.The existence of the constant strain has influenced the interfacial adhesive between the filler and binder matrix badly.The result shows that there is linear correlation between the maximum elongation and the work of adhesion.The decline of the maximum elongation is caused by the deterioration of the interfacial adhesive property.

Dome structure modification of a high temperature rise combustor based on CFD simulation

Abstract: FLUENT was used to numerically simulate the cold,single phase flow field of a combustor featured with multi-swirler.Based on the numerical results of the origin structure of this combustor,modification was made at the lip of the outer swirler which controls the mixture of oil and air.The Lean-Blow-out(LBO)and smoke features of both the scheme 1 and the scheme 2 combustor were tested on the same rig under same condition.The flow field of the scheme 1 shows that there are huge difference between the numerical result and the expected flow field inside the combustor,especially in the regions near the dome.The air flows radically at the outlet of outer swirler.The recirculation zone in the dome is not obvious,and there is a small recirculation between the outlet of the middle swirler and outer swirler.This flow field structures explain the experiment results of this scheme 1 combustor which has good Lean-Blow-out limit,but poor smoke feature.As for the scheme 2 combustor,the numerical results show that the flow direction near the outlet of the third swirlers changes and there is no longer recirculation zone between the two swirlers.Results of experiment on the two combustors about Lean-Blow-out and smoke features showed that the smoke number was greatly reduced(decreased by 29.4%),with Lean-Blow-Out decrease by 7.3%.

Thermodynamic cycle performance for water ramjet motors

Abstract: Toward water ramjet motors utilizing a multiple water-injection mechanism,corresponding thermodynamic cycle model has been put forwards preliminarily.Cyclic performance was also implemented under several certain working conditions.Making Mg/AP/HTPB mixture as a hydroreactive metal fuel,the rules of thermal efficiency along with some critical influential factors were obtained.In general,increasing either chamber pressure or magnesium mass fraction in basic formation fuel,thermal efficiency shows increasing trend while falling off along with water-fuel ratio.Especially,given a fair water/fuel ratio of order 3.0 while keeping the chamber pressure and navigational depth as 2.5 MPa and 10 m,respectively,thermal efficiencies were obtained as high as 37.78% and 44.38%,with respect to mass fraction of hydroreactive metal fuel with magnesium 50% and 60%,respectively.

Effects of granularity of ammonium perchlorate on thermal decomposition of AP-CMDB propellant

Abstract: The effects of the granularity of Ammonium Perchlorate(AP) on the thermal decomposition of AP-CMDB propellant were experimentally studied by the combination technique of thermal analysis,MS and rapid-scan Fourier transform infrared spectroscopy(Thermal analysis-MS-FTIR) and the pressure differential scanning calorimetry(PDSC).The results show that there are obvious differences in the thermal decomposition of AP-CMDB propellant with AP of different granularities.The decomposition gas products of AP-CMDB propellant consist of NO2,NO,N2O,CO2,CO,O2,N2,H2O,HCHO and HCl.

Large eddy simulation of two-phase mixing layer with droplets

Abstract: To study the mixing course of droplets and gas and the effect of evaporation on mixing in supersonic mixing layer,the two-phase supersonic mixing layer with droplets was simulated by the method of large eddy simulation(LES).The SGS sub-grid model and the k-ω SST turbulence model were adopted to calculate the gas phase of the flow.The track model and the single droplet evaporation model were used to simulate the liquid phase.The droplets were uniformly and continuously put in the flow in the front of the mixing layer at the inlet.The non-period micro-disturbances were added to the flow below the droplets inlet,and the influence of the droplets evaporation on the micro-disturbance were observed.The differences between developments of the micro-disturbance indicated that the course of evaporation would obviously increase the thickness of mixing layer and accelerate the development of mixing layer.The evaporation disturbs the gas phase flow distinctly,which would probably lead to unstable flow and enhance the flow mixing course.

Thermodynamic calculation and analysis for water ramjet

Abstract: In order to obtain specific impulse as great as possible,and meanwhile to guarantee appropriate temperature and pressure,a dual water injection system was utilized in water ramjet.Through analysis on working process,corresponding thermodynamic cycle model was established.To investigate the performance of the engine,combining mass conservation equation,chemical equilibrium equation and energy conservation equation,detailed thermodynamic calculation was implemented.An appropriate chamber pressure is given preliminary.The qualitative relationship of performance parameter,such as specific impulse,thrust,exit temperature,etc,versus water-fuel ratio was obtained respectively.Then,the primal water-fuel ratio is determined between 0.5 and 1.9.Guaranteeing the maximum total water-fuel ratio less than 5.1,the specific impulse could achieve optimal value while total water-fuel ratio is equal to 3.5.

Optimization design of typical blade profile of long blade in ultra-supercritical steam turbine

Abstract: Based on genetic algorithm and neutral network,a multi-segment optimization design method was proposed for the typical blade profile of an ultra-supercritical steam turbineOptimization under multiple operating conditions was performed for the original and optimized blade profilesThe result showed that the concaving design for the suction side of blade profile reduced the energy loss under high Mach number conditionsSynthetically with the subsonic design technique for the blade leading edge and pressure side,the aerodynamic character of the blade profile was increased under conditions from critical to high Mach numberThe optimization method decreased sample number and improved optimization effectiveness

Ignition performance of a single trapped vortex combustor with evaporation tube as fuel supply

Abstract: To investigate the lean ignition performance of a new single rapped vortex combustor,experiments have been employed in variety inlet conditions,different spark positions,and different spark energyThe results indicate that as Ma of inlet conditions varies from 03 to 055,and temperature from 623~723 K,this type combustor can ignite successfullyHigher inlet temperature will be helpful for ignitionThe effect of increasing depth of spark is not as good as expectedThe disciplinary of ignition for different positions is not the same

Coupled heat transfer analysis of air cooling gas turbine

Abstract: Coupled heat transfer simulations with a FDM coupled solver were carried out to study the factors effecting the coupled simulation accuracy.Such factors included numerical grids around the blade wall,the turbulence and transition models,and the variation of Pradtl number.The difference scheme corresponding to the conjugate heat transfer dynamics differential equation and structured grids were employed to ensure the computational accuracy and speed.The comparison between numerical results and the measured ones shows that the grids quality around the blade wall and the transition model are essential for the coupled heat transfer simulations,and that the variation of Prandtl number affects slightly on the numerical results.

Research on boundary-layer suction in the throat of supersonic inlet

Abstract: To investigate shock/turbulent boundary-layer interaction after the throat of the supersonic inlet,the commercial CFD software FLUENT was exploited to simulate the flow field of the single wedge compression supersonic inlet at the design point.By analyzing the flow loss mechanism,boundary layer suction method at the throat of the supersonic inlet was introduced,and the flow fields of inlet with three kinds of suction slot dimension were simulated.The simulation results indicate that boundary layer suction in throat can fix the shock in the throat and it forms a stable flow field.It can improve the inlet performance.Less suction mass flow ratio will not change the structure of the flow field.By increasing suction mass flow,the shock train after the throat will turn to a normal shock.As there is no separation after the normal shock,the flow field is stable.

Atomization and characteristics of gelled propellant with impinging injector

Abstract: The effects of impinging angle and injection velocity on spray property of impinging injector with gelled propellant were studied using the laser holograph and image processing method.The injection impinging angle ranged from 40° to 90° and the injection velocity ranged from 15 m/s to 55 m/s.The test results indicate that increase of injection impinging angle and injection velocity could improve gelled propellant atomization.The decrease of injection orifice diameter is propitious to gelled propellant atomization.The infinite apparent viscosity is the main factor for gelled atomization.The spray characteristic of gelled propellant with impinging injector was analyzed.According to the test result,the spray field could be divided into three areas:inerratic liquid ligaments area,inordinate ligament-net area and ligament-drop sharing area.

Experiment on treating block number of non-axisymmetric casing treatment

Abstract: Traditional axisymmetric casing treatment always reduces the efficiency while improving the stall margin of a compressor.Five non-axisymmetric casing treatments with different circumferential block numbers were designed.It was proved that different numbers of treating blocks influence compressor stall margin little,but obviously change the efficiency and total pressure rise.Both of which rise is followed by a gradual decline at the process of increasing the number of treating blocks.An optimized non-axisymmetric casing treatment can not only increase the stall margin of compressor by 13%,but also raise the max efficiency by 0.8%.The cause for this is analyzed as that non-axisymmetric distributed treating slots change the unsteady exciting signal for the tip flow.Based on the Unsteady Cooperative Flow theory,the low-frequency exciting signal from the optimized non-axisymmetric casing treatment can coupled with the complicated vortex tip flow in the compressor.

Numerical simulation for operation process of ejector/ramjet mode transition of RBCC

Abstract: Four different mode transition scheme integration numerical investigation for combustion flow field of inlet and combustor was carried out. The transformation rule of flow and combustion mode and inlet operation state during the mode transition transient process was investigated. The results show that the main cause of thrust fluctuation is the discontinuity of combustion and heat reaction area along the flow direction and the reserved hot gas of primary rocket plays the role of flame holder and combustion enhancement. Reasonable mass flow rate of the reserved hot gas can not only shorten the mode transition time, but also can improve the specific impulse of RBCC. Based on numerical simulation result the mode smooth transition scheme through modulating the fuel injection scheme and throttling style of primary rocket was brought forward. The mode smooth transition scheme is validated by numerical simulation. The numerical results may provide combustion control method to be used in experiment.

Vibratory mode localization factors of mistuned bladed disk assemblies

Abstract: Based on the vibration mode characteristics of mistuning bladed disk,the definitions of three modal localization factor are presented to assess quantitatively the behavior of the shape localization for the mistuned bladed disk,including the mode displacement factor,mode stress factor and mode strain energy factor.By these three mode factors,an example of mistuning bladed disk is finished by ANSYS.Their main properties are explained.Results indicate that the mode localization factors presented are effective.

Power extraction method of designing starting control law for turbofan engine

Abstract: Power extraction method(PEM)of designing starting control law for turbofan engine was presented,and the computer program was developed.The PEM of designing starting control law is based on the principle of PEM of designing acceleration control law for turbofan engine,combined with the method of extrapolation of component maps.The starting control law for turbofan engine at single flight state and in whole starting envelope was designed by using the program.Computing results were analyzed.It shows that PEM is accurate and effective for designing starting control law for turbofan engine.

Experiments of discharge coefficient of film cooling holes under adverse pressure gradient

Abstract: To study the influence of geometries and aerodynamic parameters on discharge coefficient in the presence of the mainstream adverse pressure gradient,experiments were carried out in a scaled up low speed wind tunnel.The discharge coefficient of the expanded holes is compared with that of the cylindrical holes firstly and then the investigation is focused on the discharge coefficient of the expanded holes.The results show that the discharge coefficient of the expanded holes is larger than those of the cylindrical holes.Both the large plane angles and the small radial angles provide the greater discharge coefficient.Discharge coefficient increases when the momentum flux ratios increase,especially at the momentum flux ratios lower than 4.The high turbulence intensity produces the large discharge coefficient,especially at the low momentum flux ratios.Density ratios have weak influence on the discharge coefficient,except at the large inclination angles of the film cooling holes.

Effect of aspect ratio on 2-D hypersonic inlet performance

Abstract: CFD simulations were performed on four 2-D hypersonic inlets with different aspect ratios in constant areaEffects of aspect ratio were analyzed at designed Mach 6 and other Mach numbers with different back pressuresThe investigation suggest that with the reducing of length and wetted area while rising of aspect ratio,total pressure recovery coefficient of external compress ramp,mass flow ratio and coefficient of internal drag decrease;Inlet with low aspect ratio,as the huge area of three-dimensional-flow near the side wall,performance of inlet is affected notable and the starting ability become worse;When the inlets work in peak back pressure with design Mach number,the pressure that the 2-D hypersonic inlets can endure would reduce with the rising of aspect ratios

Effects of plasma on the combustion of H_2/Air mixture under different initial temperatures

Abstract: Plasma assisted combustion process is a non-equilibrium,non-uniform and transient physical chemistry process. Active particle is a key problem in the calculation of plasma assisted combustion. The combustion chemical kinetic model of H2/Air is established. The non-equilibrium plasma conditions which the active particle(O,H) and (OH) produced by gas discharge influence the components, temperature and pressure in the combustion process under different initial temperature were calculated and analysed. It provides theoretical base for the experiment and application of plasma assisted combustion in aircraft engine combustion chamber. The results show that plasma assisted combustion can improve reaction efficiency, reduce combustion rise time, increase combustion temperature and flame propagation velocity and strongly influence H2/Air mixture combustion.

Optimized design on a new type thermal structure of scramjet combustor

Abstract: In order to study some methods of scramjet engineering design,an active cooling thermal structure scheme based on ceramic matrix composite(CMC) is designed for scramjet combustor.Models of thermal structure design and inert mass calculation of scramjet combustor have been built up.Base on Genetic Algorithms,single-objective optimization and multi-objectives optimization have been done for thermal structure;optimized parameters include each layer thickness,trough width,rib width and rib height.According to the results of single-objective optimization,combustor mass is decreased by 21.7% and the thermal structure dimensions under minimum mass are also obtained.According to the results of multi-objectives optimization,a Pareto front is got.

Experimental investigation on the relation between micro-thrust and impinging force

Abstract: If micro-thrust is measured directly by mounting the micro-thruster on the test stand,the fluid supplying pipes,power cords,thermocouple wires and so on,which connect the thruster with equipments outside the test stand,often disturb micro-thrust test signal severely and cause large error,even failure.To overcome this problem,it is proposed to test the impinging force produced by the jet from the micro-cold gas thruster impinging on the test probe,instead of testing the thrust force directly and study the relation between impinging and real thrust forces.It is found that if the test probe area is large enough,the profile of the impinging force with respect to the distance between the nozzle and the test probe will turn out a plateau area.The impinging force within the plateau area changes little and is almost equal to the real thrust force.

Investigation on supersonic cold flow and liquid jet over struts

Abstract: The flow pattern in a scramjet combustor with a strut injector and the mixing effect of the fuel are critical aspects of the scramjet performance Characteristics of non-reacting supersonic flows over struts were investigated experimentally and numerically, and the mixing performance of struts with liquid jets in non-reacting flow was studied experimentally Results show that the flow field can be affected by sweepback angle greatly The alternating-wedge struts produce intense vortices, which accelerate the diffusion of fuel in mainstream and enhance the mixing Jets into crossflow make the diffuseness of fuel in mainstream more quickly and achieve better mixing, compared with parallel jets

Effects of swept-curved blade on the performance of the multistage fan

Abstract: Numerical simulations were carried out to investigate the effects of swept-curved blade on the performance of the multistage fanSwept and curved blade were applied to the 2nd and 3rd stator of a three-stage fan to study the mechanism of performance improvementThe results show that swept-curved blade row can affect the others by changing the velocity density distribution along blade heightSwept blade can move not only the end-wall low energy fluid which is similar with the curved blade,but also the main flow fluidThus,the swept blade influence on velocity density distribution is greater than the curved bladeAs the speed of rotation decreases,the effect of fluid migration of the curved blade is strengthened,whereas the swept blade is oppositeIt is found that,the combination of curved and swept blade,which are all effective on improving the performance when used individually,can not get the double profit in performance