AN EXPANDER, AN ORGANIC RANKINE CYCLE SYSTEM COMPRISING SUCH AN EXPANDER AND A METHOD OF PRODUCING AN ORGANIC RANKINE CYCLE SYSTEM COMPRISING SUCH AN EXPANDER

摘要

Expander (4) for use at a maximum internal operating temperature of less than or about 180°C, comprising a stationary shroud (25), a plurality of blades (10) or shrouded blades (10') arranged circumferentially about a rotor (30) and extending substantially radially from the rotor towards a first surface (31) of the stationary shroud (30). In a pre-operating condition a substantially radial gap (r) is formed between a surface of a radially outermost tip of the blades (10) or the shrouded blades (10') and the first surface (31) of the stationary shroud (25). The material of the blades (10), or shrouded blades (10'), and alternatively also the stationary shroud (25) comprises at least 80 at.% aluminum, and the blades (10) or shrouded blades (10') and at least the first surface (31) of a stationary shroud (30) if of at least 80 at.% aluminum presents a surface layer (20) having a thickness (d) of from 1 to 1000!-1m and an average Vickers hardness of 400 HV or more, such that the gap (r) is defined between two surfaces wherein at least one of the surfaces presents said surface layer. Corresponding organic Rankine cycle and method of producing such a cycle are also provided.