Handbook of Turbomachinery Second Edition Revised - Ventech!

e well matched with the engine. The effect of upstream wakes was
sometime included as in the work of Doorley et al. [14], where a moving
wake simulator was used. Matching the gas properties and temperature
effects with those of the engine were often ignored or assumed to be of
secondary importance.
Nevertheless, because of the usually medium to large size of the
facilities (&1–106 engine scale), high-quality steady flow data could be
obtained that demonstrated the complexity of the turning flow in cascades.
Such features as the passage vortex and separation near the end walls were
observed and their influence on heat transfer measured. For example, the
work by Langston et al. showed the importance of three-dimensional
separation in cascades and demonstrated that end walls could not be well
modeled by the existing design methods.
Around the middle of the 1980s, there began to appear large-scale
(equal to or greater than engine-scale) facilities that added rotation to the
experiments. Anoted large-scale rotating turbine facility is shown in Fig. 4.
The motivation for building large-scale facilities shows the importance to
the gas turbine industry of better defined heat-transfer information.
To give a sense of the scale of the facility, the turbine tip diameter is
about 60 in. (2 m) and a typical blade might be 12 in. (30 cm) long. The
capability of the GE facility to measure boundary-layer properties may be
seen in the very detailed data given by Dorney et al. [15]. A facility of similar
scale exists at United Technologies Research Center [16], and a number of
others may be found in Europe.
The large size and slower speed of these test ‘‘rigs’’ allow more detailed
surface measurement and the easier use of some advanced measurement
techniques such as Laser Doppler Velocimetry (LDV) and Particle Image
Velocimetry (PIV) for in-passage flow velocity measurements.
Exploring variable fluid properties, high Mach numbers, and strong
rotational effects still would have to wait, however, for further developments.
CALCULATIONS USING QUASI-3D AND BOUNDARY-LAYER
METHODS
Figure 5shows the results of astudy of the performance of several 2D
boundary-layer codes used with a 2D inviscid main flow solution by
Harasgama et al. [17]. The experimental plots are heat-transfer coefficient, h,
versus distance along a surface streamline from the leading edge for a vane.
These boundary-layer codes were executed using the same initial, freestream,
and surface conditions, but with different turbulence models, in this
Copyright © 2003 Marcel Dekker, Inc.