1,721,001 research outputs found
Development and Commissioning of the New European Integrated Spacecraft Propulsion Test Facility
No full textMeasurements of Energy Spectra in Weakly Compressible Turbulence
Full text linkAn extensive investigation of velocity fluctuation spectra has been performed in the weakly compressible, decaying turbulent field established in the test section of a small scale hypersonic wind tunnel. The measured one-dimensional spectra exhibits a non-Kolmogorov power-law behavior over a significant wavenumber range, with a -11/3 exponent which is not predicted by available scaling relations for compressible turbulence. On the other hand, such power-law exponent is in agreement with recent EDQNM and LES results for the irrotational component of velocity fluctuations in weakly compressible flows. Based on these result, a new dimensionallybased scaling relation is obtained for the compressible energy spectrum, which is in agreement with the numerically observed radiative behavior for weakly compressible turbulence
Application of Bayesian Techniques to Turbine Condition Monitoring
Full text linkAbstract. The application of a Maximum Likelihood Estimate technique has been implemented in an Engine Condition Monitoring framework for a small turboshaft for power generation purposes. The turboshaft has been modeled in a fully non-linear way, by using actual turbomachine performance maps obtained from the manufacturer: the accuracy of the simulation proved to be very good with respect to real operating data. The model was used both to generate sample synthetic dataset (by adding Gaussian noise to the selected outputs-measurements) and as the core computational engine in the identification process. The results obtain show the very good robustness of the proposed identification process, and its capability of dealing with noisy or even malfunctioning transducers. This capability is provided by the possibility of determining a mathematically sound statistical framework, which is not only capable of identifying the most likely fault configuration but also to indicate the confidence level with which the identification is performed
An Ignition Transient Model for Solid Propellant Rocket Motors
No full textIgnition transients are a very important practical aspect in the design of solid propellant rockets, for the prediction and control of dynamic loads on the motor and on the entire vehicle. The present study is detailing a simple model and the relative numerical solution method for the analysis of ignition transient in solid propellant motors. The model is capable of providing an accurate and reliable prediction of the most significant engineering quantities (pressure and velocity in the thrust chamber) for different rocket configurations, for which currently available methods are yielding relatively unsatisfactory results: this would allow for an effective preliminary design of the motor, minimizing the need for experimental tests. A theoretical quasi-one-dimensional model is derived from basic conservation laws, taking into account the initiation of combustion by the igniter discharge signal, the heat transfer from igniter combustion products to the propellant grain surface, the flame spreading flow field in the chamber and the increase of chamber pressure up to to the quasi-steady operating condition. The set of modeling equations are then solved using a slightly modified Lax-Friedrics method. Sample results are presented for typical solid boosters of the Ariane family (Ariane 4 and Ariane 5)
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