Results 1 - 10 of 3270
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[en] Some general features of a new class of thermodynamic device combining a thermodynamic cycle with the externally applied steady flow of an open thermodynamic process are discussed and experimentally demonstrated in the context of a thermoacoustic refrigerator. copyright 1998 The American Physical Society
[en] It is shown that in theories of gravity where the cosmological constant is considered a thermodynamic variable, it is natural to use black holes as heat engines. Two examples are presented in detail using AdS charged black holes as the working substance. We notice that for static black holes, the maximally efficient traditional Carnot engine is also a Stirling engine. The case of negative cosmological constant supplies a natural realization of these engines in terms of the field theory description of the fluids to which they are holographically dual. We first propose a precise picture of how the traditional thermodynamic dictionary of holography is extended when the cosmological constant is dynamical and then conjecture that the engine cycles can be performed by using renormalization group flow. We speculate about the existence of a natural dual field theory counterpart to the gravitational thermodynamic volume. (paper)
[en] Highlights: ► A vibration analysis of an internal combustion engine was carried out. ► Sound intensity and surface vibration velocity measurements have been employed. ► The radiation factor of the engine vibrating surfaces was determined. ► The radiation factor can be applied for diagnostic scopes. -- Abstract: The present work deals with the problem of monitoring and diagnosis, through non-intrusive methodologies, of stationary internal combustion engine, with particular attention to the cogenerative 1 MW unit installed at the Engineering Faculty of the University of Perugia. Specifically, acoustic and vibrational measurements have been performed to correlate the engine functional status (and therefore the vibration of mechanical surfaces) with the acoustic emissions features through the characteristic radiation factor. The ISO/TS 7849 normative for the correlation of vibration and acoustic measurement has been employed.
[en] In the paper, the structure, working principle, functions and characteristics of an data acquisition and analysis system for internal combustion engines (I.C. engine) based on DSP is introduced. The DSP can not only acquire and analyze the data alone, also can work with the PC together to form data acquisition and analysis system with high speed and large memory. The system takes advantages of TMS320F2812's plenty of peripherals on chip, becomes small and easy for installation. USB technique is used to translate data between DSP and PC in high speed, so the system's real time processing is proved very much. It is proved that the designed system can acquire and analyze the steady and transient parameters of the I.C. engine very well
[en] An engine coolant pre-heater is adopted to raise the temperature of a coolant for the proper operation of the engine at a harsh environment. We evaluate the performance of a pre-heater operating at a specified condition using LMTD and ε-NTU methods, and select critical design variables for optimization. The reference pre-heater model is a simple cross-flow heat-exchanger with a single path for both coolant and heating water. The results indicate that the pre-heater exhibits better performance than the reference model when it has four paths for the coolant and two paths for the heating water. The final model for optimization has a volume 45% smaller than the maximum size allowed while satisfying given design requirements
[en] The damping decrements of pressure fluctuations in the combustion chambers of liquid-propellant rocket engines may be estimated on the basis of hard excitation of acoustic vibrations of a specific mode. A device for hard excitation of high-frequency pressure fluctuations has been developed. This device prevents damage to the components of the combustion chamber by flying metal fragments. Recommendations are made regarding the calculation of the acoustic characteristics for complex channels.
[en] In this article, a chronological analysis of the technologies and events that any way influenced in the evolution of the internal combustion engine is done everything it through the observation of the works carried out for scientific empiric and engineers whose technical and conceptual value meant the motivation of other people for the search of a better development in this engineering field
[en] We analyse the two-dimensional motions of the rockets for various types of rocket thrusts, the air friction and the gravitation by using a suitable representation of the rocket equation and the numerical calculation. The slope shapes of the rocket trajectories are discussed for the three types of rocket engines. Unlike the projectile motions, the descending parts of the trajectories tend to be gentler and straighter slopes than the ascending parts for relatively large launching angles due to the non-vanishing thrusts. We discuss the ranges, the maximum altitudes and the engine performances of the rockets. It seems that the exponential fuel exhaustion can be the most potent engine for the longest and highest flights