Theoretical and Experimental Study on Flow Characteristics of a Diaphragm Pump for Urea-SCR Systems

Urea selective catalytic reduction (SCR) is the primary technology used to reduce the nitrogen oxides (NO x ) of diesel engine exhaust. To meet the requirements of an SCR system, a novel type of miniature diaphragm pump was designed. Based on the theory of large deflection of annular plates, the equilibrium equations of a diaphragm with a rigid inclusion were established, and the equations were solved by the nondimensional method and the finite difference method. Theoretical and approximated flow model for this pump were proposed. A theoretical relationship between back pressure, rigid inclusion size and volumetric efficiencies were calculated. To verify the validity of theoretical model, a prototype pump was fabricated and tested. Experimental results demonstrated that the flow is proportional to the pump speed. The deviation between theoretical, approximated flow and experimental flow was less than 4 % and 9.4 %, respectively. The difference between theoretical and experimental volumetric efficiency was varied from 2.7 % to 6.1 % when back pressure changed from 0 to 0.9 MPa. The volumetric efficiency was growing with the increasing of the rigid inclusion size. The pressures in the working chamber showed almost the same overall trends between the theoretical results and experimental values. The experimental results show that the proposed theoretical model is effective.