Tai Jin

Simulations of Cellular Detonation Interaction with Turbulent Flows

Comparative studies of different inflow turbulent forcing effects on detonation front dynamics and the flow statistics are conducted through direct numerical simulations of turbulence–detonation/shock interactions. High-resolution bandwidth-optimized weighted essentially nonoscillatory scheme of spatial discretization and total variation diminishing temporal integration are used to solve the three-dimensional chemically reactive Navier–Stokes equations. The turbulent inflow vertical and entropic forcing effects on the three-dimensional detonation front and cellular structures are first analyzed. The influence of the inflow forcing on the generated regular cell patterns with diamond shape is compared. The vortex behind the detonation is quite different from that behind shock waves with the same inflow fluctuations. This also results in the larger increase of velocity variances downstream of detonation than the turbulence–shock case. The similar trend can also be found for the Taylor microscales. Effects of...

Experimental Investigation of Thermoacoustically Driven Pulse Tube Refrigerator Using Noble Gas Mixtures

Based on the estimation of thermophysical properties of binary noble gas fluids, He-Ar mixtures are used as working fluids to improve the performance of a pulse tube refrigerator driven by a thermoacoustic engine. Computed and experimental results are reported in detail, and some discussion is given. With 20% molar fraction of Ar the refrigeration temperature was lowered by 3 K as compared to pure He.

Thermoacoustically driven pulse tube refrigeration below 90K

Publisher Summary This chapter focuses on the matching between thermoacoustic prime mover and pulse tube refrigerator, especially the frequency matching. Recent modification has been made to improve the refrigeration performance of thermoacoustically driven pulse tube refrigerator, and a refrigeration temperature as low as 88.6K, with helium filling of 2.1MPa as the working fluids, is achieved. The onset temperature is reduced about 200oC (from 550oC to 340oC) by the simple operation of the double inlet valve which would broaden the utilization of low-grade heat energy. With helium as working fluid (filling pressure of 2.1MPa), an 8 m resonant tube results in a resonance frequency of 44 Hz (the input power is 2200 Watts), and a refrigeration temperature of 88.6K is obtained in self-made thermoacoustically driven pulse tube refrigerator system while the mean pressure and the pressure ratio are 2.64MPa and 1.128, respectively. The simple operation on the double inlet valve, which was closed before the onset of acoustic oscillation and turned to the optimal value as soon as the oscillation started, could decrease the onset temperature of the system greatly. It would broaden the access of utilizing the low-grade heat energy.