1,720,972 research outputs found
An Electropneumatic Control and Actuation System for the Vanes of the Variable Geometry Turbine of a Turbocharged Diesel Engine
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Comparison between mechanical and pneumatic spring effects on valve train dynamics
No full textEdited CT2005 CD-Volume on Cam Transmissions: functional and dynamical aspect
Analisi delle prestazioni di sistemi di trasmissione a camme con dispositivi di richiamo pneumatici
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Mechanical Spring ReplacementWith Pneumatic Return Device ina Valve Train: Effects onDynamics and Preload Tuning
No full textThe paper presents a comparison of performance for a cam transmission of an engine valve train operating with a mechanical spring and with a return spring device that uses a pneumatic spring. Dynamic analysis of the cam mechanism is performed in the frequency and time domains employing a combined lumped-distributed parameter model capable of predicting the effects of the higher harmonics of the cam lift profile on system performance, in particular of the return spring device. Dynamic stiffness of the transmission in the frequency domain and time history of the contact force between cam and follower are evaluated. The limits of the traditional mechanical spring-closing system at high-speed camshaft operations are investigated, highlighting that they are mainly imposed by the internal resonances of the spring. The pneumatic spring is an improved replacement of the steel spring, because of better dynamic behavior. Furthermore, the pneumatic return device allows preload tuning of the spring, which may increase transmission efficiency through proper control of the fluid pressure. Study of the pressure control circuit is also presente
Modal Approximation Time-Domain Models for Pneumatic Transmission Lines
No full textThe simulation of time-varying flow in fluid transmission lines can be based on a modal approximation of the frequency domain irrational transfer matrix. The obtained rational approximation can be used in variable time step simulators to evaluate the influence of the line on fluid servosystems dynamics. In this work the application of a numerical approximation technique (Vector Fitting) is proposed, with particular attention to physical causality, stability and passivity of the model. This approach is applied to the study of pressure transients in pneumatic lines. Simulation results are compared with results furnished by Pichè and Ellman's variational method and with experimental data obtained on test bench, showing a good agreemen
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