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Microturbines 173
For example, United Technology Corporation, in partnership with DTE
Technologies, Kyocera and others has developed a microturbine derived
from the Pratt & Whitney ST5 helicopter engine. The ST5 engine was
derived from the PWA200 (Figure 11-2), which in turn was derived from
the PT6 (Figure 2-3) turboprop engine. These engines use a combination
of centrifugal and axial components. Conversely, the Ingersoll-
Rand’s PowerWorks 250 was scaled down from the Ingersoll-Rand KG2,
a 1.7-megawatt gas turbine, which employs centrifugal designs for both
the compressor and turbine components (Figure 11-3).
Figure 11-2. Courtesy of United Technologies Corporation, Pratt &
Whitney Aircraft. The PW206 turboprop engine is a 700 shaft horsepower
engine used primarily in helicopter applications. Current
applications include the Agusta A109E Power, Bell M427, Eurocopter
EC135P1/P2, and the MDHI MD900/902.
The compressor component, turbine component and in some
designs the electric generator rotor are fixed to the main shaft (Elliot
Energy Systems TA 100 inertia weld these components onto the main
shaft). The compressor and main shaft (see Figure 11-4) are typically
made of stainless steel. Specific materials used in microturbine air
inlets and compressors are similar to materials used in the larger
gas turbines and are listed in Table 3-2.
Turbine
The majority of microturbines employ the radial inflow turbine
wheel design. The design looks much like the compressor
component (except of course the geometry is reversed). There are
some designs that combine an axial stage (as in multi-megawatt