Design and Analysis of Diffuser for Helium Turboexpander

Abstract

Cryogenic process gained tremendous growth due to the rapid industrial use of gases such as oxygen, nitrogen and inert gases like argon. Their consumption is now the indicator of technological growth. Nitrogen is used in many industrial processes, such as ammonia based fertilizer production, semiconductor industry and low temperature processes like cryosurgery which consumes liquid nitrogen as a cooling medium. Argon finds application in TIG welding and high temperature furnaces. Oxygen is the most important input in processes like steel making, welding, and sewage treatment and as rocket propellant. These gases are in huge demand throughout the world. Air separation is the well-known process of producing these gases from the only source: Atmosphere. Now a day’s membrane separation and adsorption processes are the emerging technique, but low temperature distillation is still popular for the bulk production. This cryogenic process leads to production of rare gases (xenon, neon) and argon, economical in bulk production, gives liquid and gaseous product as output. At Present, Turbo expander is the major part of every cryogenic Liquefaction plant. Its efficiency greatly affects the cost effectiveness of the plant. Turboexpander house different parts such as Shaft, Turbine wheel, Brake compressor, nozzle, diffuser and many more. Diffuser finds application in converting kinetic energy of fluid leaving the rotor into potential energy. This results in pressure gain with relative cold production. Efficiency and reliability of diffuser greatly affects the cost parameters and working range of Turboexpander. This makes the design of diffuser important. Diffuser, providing the desired pressure recovery is designed based on turbine dimensions, velocity profiles and working fluids. Design should be followed by analysis in order to optimize the performance. The purpose of the paper is to throw light on the design methodology and analysis of diffuser.