Characteristics of Droplets Ejected from Liquid Propellants Ablated by Laser Pulses in Laser Plasma Propulsion

The angular distribution and pressure force of droplets ejected from liquid water and glycerol ablated by nanosecond laser pulses are investigated under different viscosities in laser plasma propulsion. It is shown that with increasing viscosity, the distribution angles present a decrease tendency for two liquids, and the angular distribution of glycerol is smaller than that of water. A smaller distribution leads to a higher pressure force generation. The results indicate that ablation can be controlled by varying the viscosity of liquid propellant in laser plasma propulsion.

Effects of ignition voltage and electrode structure on electric ignition and combustion characteristics of Ammonium Dinitramide(ADN)-based liquid propellants in electric ignition mode in inert gas environment

Hydrazine is toxic and carcinogenic, which greatly increases the difficulty of application and no longer meets the needs of green aerospace. As a green propellant, the Ammonium Dinitramide(ADN)-based liquid propellant has the advantages of higher specific impulse, being non-toxic,pollution-free, and easy storage. However, an ADN-based space engine in orbit has exposed the problems of high-temperature deactivation of catalysts and cold-start failure. An active ignition technology—electric ignition technology was explored in this paper to break through the technical bottleneck of catalyst deactivation and the inability to a cold start. An experimental system of a constant-volume combustor for the ADN-based liquid propellant based on the electric ignition method was established. The electric ignition and combustion characteristics of the ADN-based liquid propellant in a volume combustor with an electric ignition method were studied. The influencing mechanisms of the ignition voltage and the electrode structure on the electric ignition characteristics of the ADN-based liquid propellant were investigated. An elevation of the ignition voltage could facilitate the ignition process of the ADN-based liquid propellant, curtail electric energy input and heating effect, while exerting an adverse impact on the combustion process of the propellant.An increase in the ignition voltage enhanced the ignition process of the propellant while simultaneously suppressing its combustion process when utilizing mesh electrodes. Compared to the strip electrodes, the mesh electrodes increased the contact area between the electrodes and the propellant,increased the electric energy input power in the electric ignition process, and reduced the ignition delay time. The mesh electrodes could promote the combustion process of the propellant to a certain extent.

Dynamic interaction between clustered liquid propellant rocket engines under their asynchronous start-ups

A nonlinear mathematical model of the low-frequency dynamics of the clustered multi-engine rocket propulsion system has been developed and the computations of the engine transient processes during the start-ups of the four-engine propulsion system with a shared feed system have been made applied.Based on propulsion system start-up modeling the influence of the connectivity of engines in a cluster on the starting characteristics of individual engines is shown.In particular,an advanced nonlinear mathematical model of the pump cavitation phenomena is a distinctive feature of the mathematical model.The computation results showed that the asynchronous engines start-ups during rocket lift-off lead to severely nonlinear engine transients and clustered engine thrust misbalance.The influence of the rocket engines asynchronous start-ups on the clustered feed system transients depends on many factors,mainly on from the clustered feed system low-frequency dynamics,the magnitude of the disturbance and the phase difference between disturbances acting on different branches of the feed system.The deep lingering dips in the flow rate and pressure transients are possible due to the nonlinear dynamic interaction of the engines.In case of great pressure dips at the pump inlet(up to the pressure of saturated vapors during significant periods of start-up time)the cavitation breakdowns of the pumps of one or more engines from the cluster are possible.This can disrupt the operation of the entire propulsion system and leads to the failure of the launch vehicle mission.

Cooling process of liquid propellant rocket by means of kerosene-alumina nanofluid

Heat transfer augmentation of kerosene-alumina nanofluid is studied for the possible use in the regenerative cooling channel of semi cryogenic engine.The basic partial differential equations are reduced to oidinary differential equations which are solved using differential transformation method.Velocity and temperature profiles as well as the skin friction coefficient and Nusselt number are determined.The influence of pertinent parameters such as nanofluid volume fraction,viscosity parameter and Eckert number on the flow and heat transfer characteristics is discussed.Tbe results indicate that adding alumina into the fuel of liquid rocket engine(kerosene)can be considered as the way of enhancing cooling process of chamber and nozzle walls.Nusselt number is an increasing function of viscosity parameter and nanoparticle volume fraction while it is a decreasing Junction of Eckert number.

First Systematic Testing Platform for Pressurization Feed System Developed for Liquid Rocket Propellant in China

Beijing Aerospace System Engineering Institute of China Academy of Launch Vehicle Technology (CALT) declared recently that theinstitute has set up a laboratory whichwould operate a newly

Flight Dynamic Analysis of Hypersonic Vehicle Considering Liquid-Solid Coupling

With the liquid propellant making up 60%—70% of the takeoff weight of the hypersonic vehicle,the dynamic load caused by great propellant sloshing interacts with the flexible structure of the aircraft.Therefore,the dynamic model displays characteristics of strong coupling with structure/control and nonlinearity.Based on the sloshing mass dynamic simplified as a spring-mass-damping model,a rigid-flexible-sloshing model is constructed.Moreover,the effect on the dynamic performance of the coupled model is analyzed with changing frequency and damping.The results show that propellant sloshing dynamics significantly affects the rigid body motion modes,especially flexible mode and short mode.The right half plane pole(RHP)moves far from the imaginary axis with the consumption of the propellant.The flexible mode attenuates with the increase of the sloshing damping,and the coupling becomes stronger when sloshing frequency is close to the short mode frequency or the flexible frequency of the beam.

Influence of Surface Radius Curvature on Laser Plasma Propulsion with Ablation Water Propellant

The surface shape of liquid water is well controlled during nanosecond pulse laser ablation plasma propulsion. In this study, we measured the effect of the shape on the coupling coefficient and the specific impulse. We found that the coupling coefficient and specific impulse could be optimized by varying the surface convexity. Based on the analysis of the surface radius curvature, we demonstrate that the convex surface changes the laser focal positions to achieve high efficiency.

Experimental research on rotating detonation with liquid hypergolic propellants

This paper describes experimental research into the initiation and propagation of rotating detonation for liquid Nitrogen TetrOxide(NTO) and liquid MonoMethylHydrazine(MMH).An annular rocket-type combustor without nozzle was designed to investigate detonation combustion. The propellants were injected through unlike impingement injectors. The combustion flame fronts and pressure waves were detected using optical diagnostics and dynamic pressure sensors,respectively. The propagation of rotating detonation was established spontaneously by increasing the mass flow rate of propellants. The velocity of propagation of the flame fronts and pressure waves was nearly equal and reaches supersonic speed. Two different detonation combustion patterns are present, single wave mode and double waves mode. And in double waves mode, the two detonation waves are always counter-rotating. The possibility of rotating detonation initiation in a combustor with nozzle was also checked. Stable rotating detonation can be initialized and sustained at similar operating conditions.

空化诱导轮内流动不稳定性的最大似然估

The article illustrates the application of Bayesian estimation to the identification of flow instabilities,with special reference to rotating cavitation,in a three-bladed axial inducer using the unsteady pressure readings of a single transducer mounted on the casing just behind the leading edges of the impeller blades.The typical trapezoidal pressure distribution in the blade channels is parametrized and modulated in time and space for theoretically reproducing the expected pressure generated by known forms of cavitation instabilities(cavitation auto-oscillations and higher-order surge cavitation modes,n-lobed subsynchronous/synchronous/super-synchronous rotating cavitation).The Fourier spectra of the theoretical pressure so obtained in the rotating frame are transformed in the stationary frame,frequency broadened to better approximate the experimental results,and parametrically fitted by maximum likelihood estimation to the measured auto-correlation spectra.Each form of instability generates a characteristic distribution of sidebands in addition to its fundamental frequency.The identification makes use of this information for effective detection and characterization of multiple simultaneous flow instabilities with intensities spanning over about 20 db down to about 4 db signal-to-noise ratios.The same information also allows for effectively bypassing the aliasing limitations of traditional cross-correlation methods in the discrimination of multiple-lobed azimuthal instabilities from the measurements returned by arrays of equally spaced sensors.The method returns both the estimates of the model parameters and their standard deviations,providing the information needed for the assessment of the statistical significance of the results.The proposed approach represents therefore a promising tool for experimental research on flow instabilities in high-performance turbopumps.

Chebyshev super spectral viscosity method for water hammer analysis

In this paper,a new fast and efficient algorithm,Chebyshev super spectral viscosity(SSV)method,is introduced to solve the water hammer equations.Compared with standard spectral method,the method's advantage essentially consists in adding a super spectral viscosity to the equations for the high wave numbers of the numerical solution.It can stabilize the numerical oscillation(Gibbs phenomenon)and improve the computational efficiency while discontinuities appear in the solution.Results obtained from the Chebyshev super spectral viscosity method exhibit greater consistency with conventional water hammer calculations.It shows that this new numerical method offers an altemative way to investigate the behavior of the water hammer in propellant pipelines.

Numerical investigation of low cycle fatigue life for channel wall nozzles

The thermal-structural response and low cycle fatigue life of a three-dimensional(3D)channel wall nozzle with regenerative cooling were numerically investigated by coupling the finite volume fluid-thermal method,nonlinear finite element thermal-structural analysis and local strain methods.The nozzle had a high area ratio(nozzle exit area divided by throat area)under cyclic working loads.Parametric studies were carried out to evaluate the effects of channel structural parameters such as channel width,channel height,liner thickness and rib width.Results showed that the integrated effects of three-dimensional channel structure and load distribution caused serious strain,which mainly occurred at the intersectant regions of liner wall on the gas side and the symmetric planes of channel and rib.The cooling effect and channel structural strength were significantly improved as the channel width and height decreased,leading to substantial extension of the nozzle service life.On the other hand,the successive decrease in liner thickness and rib width apparently increased the strain amplitude and residual strain of channel wall nozzle during cyclic work,significantly shortening the service life.The present work is of value for design of the channel wall nozzle to prolong its cyclic service life.