Design of diffuser (reducing stage assembly) for superheater and reheater start up vent silencer in super critical once through boilers

In supercritical boiler Startup Vent diffuser is to manage the instant release of huge amounts high pressure of steam to low pressure into atmosphere while cutting of the noise produced while venting the steam in different temperature and pressure conditions. The upstream pressure of startup vent is around 81 kg/sq.cm. so for reducing pressure from 81 kg/cm2 to 3kg/cm2 with constant flow one diffusers (reducing stage assy.) will introduce which will diffuse the pressure. Startup Vent diffuser is a design a reducing stage assembly (called a multistage diffuser) along with study of hydrodynamic parameter like Beta ratio, Mach number, and numerical calculation of orifice plate thickness, size of orifice hole & Bending stress evaluation, reducer etc.