Here we report a series of molecular dynamics simulations to confirm the feasibility of a molecule-rectifying mechanism which can continuously induce a net particle flow but has to work with an external electric field. Here we also propose an optimized model that can work without the external electric field. The results of a series of simulations show that our new model can also continuously induce net flows without any external forces. The new model can generate a considerable vapor pressure difference of up to 7.073kPa at a temperature of 370K. The new model will be easier to be verified by physical experiments and can be used to develop useful nanodevices. It is generally believed that it is impossible to exploit the kinetic energy of molecules in thermal motion at equilibrium state, but our simulation results may change this view.