ABSTRACT
In the process of vehicle development, the unsteady simulation of thermal management system is very important. A 3D-CFD calculation model of vehicle thermal management is established, and simulations were undertaken for uphill with full loads operations condition. The steady results show that the surface heat transfer coefficient increases to the quadratic parabolic relationship. The unsteady results show that the pulsating temperatures of exhaust and external airflow are higher than about 50°C and lower than 10°C, respectively, and the heat dissipating capacities are higher than about 11%. Accordingly, the conversion equivalent exhaust velocity increased by 1.67%, and the temperature distribution trend is basically the same as unsteady results. The comparison results show that the difference in the under-hood should be not noted, and that the predicted exhaust system surface temperatures using steady velocity equivalent method are low less 10°C than the unsteady results. These results show the steady velocity equivalent method can be used to predict the unsteady heat transfer effect of vehicle thermal management system, and the results obtained by this method are basically consistent with the unsteady results. It will greatly save computing resources and shorten the cycle in the early development of the vehicle thermal management system.
ABSTRACT
We experimental demonstrate stable, simple and pulse width-tunable 40 GHz short time window generation using a dual parallel Mach-Zehnder modulator (DPMZM) driven simply by an electrical clock. The pulse widths are measured to be tunable continuously from 5.6 ps to 12.6 ps by simply adjusting the DC bias voltage of DPMZM. The timing jitter, extinction ratio (ER), optical signal-to-noise ratio (OSNR) and insertion loss (IL) of the generated width-tunable time window are measured to be better than 50 fs, 18 dB, 50 dB and 16 dB respectively.
