Artikuluak-Ingeniaritza
http://hdl.handle.net/20.500.11984/478
2020-10-31T19:36:59ZPreliminary Study on the Capability of the Novel Near Solidus Forming (NSF) Technology to Manufacture Complex Steel Components
http://hdl.handle.net/20.500.11984/1878
Preliminary Study on the Capability of the Novel Near Solidus Forming (NSF) Technology to Manufacture Complex Steel Components
Plata Redondo, Gorka; Sánchez Fernández, Andrea; Lozares Abasolo, Jokin; Hurtado Hurtado, Iñaki
The benefits of the novel Near Solidus Forming (NSF) process has shown previously in its ability to produce steel components with comparable as-forged mechanical properties but with a cost reduction of 10–15%. This study further pushes the NSF technology to produce parts that are conventionally diffcult to produce via conventional methods. A 2.7 kg 42CrMo4 steel grade component was manufactured into a complex geometry using only a 400t press.
Different manufacturing parameters were evaluated to show their influence on the process and final component. A combination of X-ray fluorescence (XRF), optical microscopy and SEM analysis of the microstructure was also conducted revealing the deformation pattern of the material and shedding some light on how the material evolves during the process. The successful forging of these components shows the capability to produce previously deemed diffcult geometries, with much a
lower specification forging press, in a single deformation.
2020-01-01T00:00:00ZPower Capability Boundaries for an Inverter Providing Multiple Grid Support Services
http://hdl.handle.net/20.500.11984/1865
Power Capability Boundaries for an Inverter Providing Multiple Grid Support Services
Unamuno Ruiz, Eneko; Bilbao Ortega, Aitor
It is getting more common every day to install inverters that o er several grid support services in parallel. As these services are provided, a simultaneous need arises to know the combined limit of the inverter for those services. In the present paper, operational limits are addressed based on a utility scale for a real inverter scenario with an energy storage system (ESS) (1.5 MW). The paper begins by explaining how active and reactive power limits are calculated, illustrating the PQ maps depending on the converter rated current and voltage. Then, the ellect of the negative sequence injection, the phase shift of compensated harmonics and the transformer de-rating are introduced step-by-step. Finally, inverter limits for active filter applications are summarized, to finally estimate active and reactive power limits along with the harmonic current injection for some example cases.
The results show that while the phase shift of the injected negative sequence has a significant ellect in the available inverter current, this is not the case for the phase shift of injected harmonics. However, the amplitude of the injected negative sequence and harmonics will directly impact the power capabilities of the inverter and therefore, depending on the grid-side voltage, it might be interesting to design an output transformer with a different de-rating factor to increase the power capabilities.
2020-01-01T00:00:00ZStability analysis under thermogravitational effect
http://hdl.handle.net/20.500.11984/1863
Stability analysis under thermogravitational effect
Bou-Ali, M. Mounir
In the present work, an interferometric unsteady analysis of the thermogravitational technique was for the first time attempted in a paralelepipedic microcolumn
using binary mixtures with negative Soret coefficients. In particular, water/ethanol and toluene/methanol were considered, as they have significantly different
thermophysical properties and relaxation times. Experiments were run with different temperature gradients in order to understand their impact on the stability of
separation. Experimental results were compared with theoretical ones, predicted by Fury-Jones-Onsager theory, and by OpenFOAM 3D numerical simulations.
Correlations between the separation and the flow in the third dimension perpendicular to the thermal gradient of the thermogravitational microcolumn were
analysed. Numerical simulations were also conducted in traditional cylindrical columns in order to compare the results with those previously reported. In these cases,
the impact on separation stability was correlated with the azimuthal component of velocity. Thus, in both configurations, the disturbing convective current, always
generated in the direction perpendicular to the thermal gradient applied, was shown to be vital for flow stability analysis.
2020-01-01T00:00:00ZEfficient Calculation of Stabilization Parameters in RF Power Amplifiers
http://hdl.handle.net/20.500.11984/1861
Efficient Calculation of Stabilization Parameters in RF Power Amplifiers
Mori Carrascal, Libe
This paper proposes an efficient method for the calculation of the stabilization parameters in RF power amplifiers operating in periodic large-signal regimes. Stabilization is achieved by applying the principles of linear control theory for Periodic Linear Time-Varying (PLTV) systems. A numerical method is proposed to obtain the Harmonic Transfer Function that represents the system linearized around the large-signal steady state. Then, a feedback analysis is performed to calculate the closed-loop poles of the PLTV system. The proposed approach is demonstrated with two examples. Firstly, a three-stage amplifier that exhibits a low-frequency oscillation for increasing values of input power is correctly stabilized. Next, the stabilization of an unstable design that exhibits an odd-mode parametric oscillation is presented. The results of the proposed technique are compared to those obtained with the conventional parametric stability simulation. These examples serve to illustrate the capability and efficiency of the proposed approach.
2020-01-01T00:00:00Z