COMPRESSOR

Compressors are either the axial design (with up to 19 stages) or the centrifugal design (with one or two impellers). In the axial compressor designs, beam and cantilever style stator vanes are utilized. Cantilever style stator vanes are used in compressors where stage loading is relatively light. Compressor pressure ratios have increased signifi cantly over the past forty years with the aero-derivative consistently leading the way to higher levels. Pressure ratios, which were 5:1 at the start of World War II have increased to 12:1 for the newer industrial gas turbines. Through the use of increased stage loading (variable geometry and dual-spool techniques), compressor pressure ratios of most recent aero-derivatives have been increased to greater than 30:1 (Figure 1). This advancement in the state of the art is a prime contributor in the overall increase in simple-cycle thermal efficiency to 35% for aero-derivative gas turbines. To achieve similar efficiencies the industrial gas turbines have had to use regenerators and other forms of waste heat recovery. Typical materials used in the compressor are listed in Table 1.

Figure 1. Courtesy of United Technologies Corporation, Pratt & Whitney Aircraft. A pictorial summary portraying the history of compressor blades from the early JT3 turbojet compressor blade on the left through to the most recent PW4084 blade on the right. This photograph represents a three-fold increase in  Compressor pressure ratios.

Tabel 1 Typical materials used in the compressor

COMPONENT	MAETRIAL	TRADE NAMES
Air Inlet Housing	Aluminum
Forward Bearing Support	Aluminum	RR350, L51
	Iron	Nodular
	Stainless Steel	Jethete M.152, 17-4 Ph, 410
Housing	Aluminum	RR350, RR390, L51
	Titanium	6A1-4V
	Iron	MSRR6078, FV 448, FV 507
	Stainless Steel	Jethete M.152, Chromally
	Precipitation Hardening Super Alloy	Inco 718
Exit Housing Diffuser	Aluminum
Rear Bearing Support	Aluminum	RR350, L51
	Iron	Nodular
	Stainless Steel	310, 321, FV 448, Chromally 410, Jethete M.152, MSRR 6078
	Precipitation Hardening Super Alloy	Inco 718
Stator Vanes	Aluminum	RR 58
	Titanium	6A1-4V
	Stainless Steel	A286, Chromally, Jethete M. 152, Greek Ascoloy, FV 535, FV500, 18/8,
	Precipitation Hardening Super Alloy	Nimonic 75, Nimonic 105
Rotor Blades	Aluminum	RR 58
	Titanium	6A1-4V, TBB
	Stainless Steel	A286, Greek Ascoloy, FV 535, FV520, 17-4 Ph, 403
	Precipitation Hardening Super Alloy	Inco 718, Nimonic 901
D iscs, Spool, Drum	Titanium	6A1-4V, TBA (IMI 679), IMI 381
	Steel	4340, FV 448, B5-F5, 9310
	Stainless Steel	410, 17-4 Ph, Jethete M. 152, Chromally (FV 535)
	Precipitation Hardening Super Alloy	Incoloy 901, Inco 718, Nimonic 901
Shafts, Hubs	Steel	Hykoro, 4340, 9310, B5-F5
	Precipitation Hardening Super Alloy	Inco 718