Characteristics of steady and oscillating flows through regenerator

Regenerator is one of heat exchangers (heater, regenerator and cooler) in a Stirling engine, whose flow characteristics are very important for developing Stirling engine design methodology. A combined experimental and simulation study is carried out to investigate characteristics of regenerator in an oscillating flow, using steady flow as reference. It is found that the oscillating flow can share the same correlation equations of steady flow for friction factor within the measured kinetic Reynolds number range (2.59 × 10−2-2.04 × 10−1 for 100 mesh, 6.60 × 10−3-5.22 × 10−2 for 200 mesh, 2.74 × 10−3-2.16 × 10−2 for 300 mesh and 1.43 × 10−3-1.13 × 10−2 for 400 mesh) and dimensionless fluid displacement, and the maximum deviation between the experimental data and simulation results is found less than 9.6%. It is also found that the effect of gas compression can't be ignored for the steady and oscillating flows through a regenerator with the increase of mass flow, and the pressure drop per unit length decreases as the length of regenerator increases. The velocities at both ends of regenerator are also affected by the compression of gas, and it is found that theoretical velocity based on piston velocity can be used if the dimensionless pressure drop of the whole system is less than 4.22 × 10−2 in this experiment. After all, it should be noted that oscillating flow has its own characteristics, and obvious flow perturbations are found at downstream of regenerator, which are exactly detected by a hot wire anemometer. The effect of mesh size, frequency and mean pressure on the perturbation is investigated, and a correlation equation for the duration of perturbation is proposed based on dimensionless pressure drop of regenerator.