Numerical investigation into the compression characteristics of a multi-stage Knudsen pump with rectangular channels

In the rarefied gas, thermal creep flows are induced by temperature gradients along the walls. The Knudsen pumps based on thermal creep flows have great application potential in the micro-power systems. In this paper, the performance of the compression system comprised of a cascading multi-stage Knudsen pump for rarefied gas mixtures is numerically researched using the direct simulation Monte Carlo (DSMC) method. The results demonstrate that, in the transition and free-molecular regimes, the gas compression effects of the device are observed, and the maximum compression effect occurs when Knudsen number is approximately at 0.2. In addition, with an increase in the cascading number of Knudsen pump, the replication characteristics of the flow fields can be observed, and the compression ratio (effect) increases significantly. Specifically, in the free-molecular regime, the dependence of compression ratio on the stage number is almost linear. However, in the transition regime with strong thermal creep flows, the dependence of compression ratio on the stage number is nonlinear. Lastly, according to the results of mass flow rates returned by different compression ratios, a dimensionless linear function correlation is proposed for practical purposes.