DYNAMIC-RESPONSE OF REGENERATOR IN CYCLIC FLOW SYSTEM

The dynamic response of isothermal and cyclic flow in a regenerator is investigated. A basic transfer-function model for the regenerator is derived and used to study the system dynamics of a regenerator connecting a reciprocating piston and a reservoir using two models, G(mm)(s) and Gmp(s). The frequency response of the mass flow rate at the reservoir side of the regenerator induced by pressure or mass flow rate waves at the piston side is shown to approach zero at high frequency, but to approach a constant value of gain at low frequencies. The cut-off frequency f(cut) and bandwidth depend on the regenerator design (wire mesh size, porosity, length, diameter, etc.). The criteria for the use of a quasi-steady approximation in regenerator modelling can then be determined by comparing the operating frequency with the regenerator bandwidth. It is also shown that attenuation of the mass flow rate fluctuation induced by the pressure waves is stronger for regenerators with a larger void volume and that the use of air or nitrogen as the working fluid will induce a stronger attenuation effect than helium.