Handbook of Turbomachinery Second Edition Revised - Ventech!

3. Need for better understanding of the economics needed to justify
changes in turbine design, materials, and operating practice. Throughout
this chapter it is noted that economic analysis is needed in order to properly
weigh run/repair/replace options when steam path damage is found.
Ultimately, the constraints of a particular economic analysis are ownerspecific.
However, there is need for more comprehensive models that can
perform sensitivity studies quickly to key variables [134–141].
4. Need for better understanding of the fundamentals of the
deposition process. Control of deposition would lead to significant benefit,
most notably improvements to the efficiency in all turbine stages. Control of
deposition may be achieved by several methods including improved surface
finish and improvements in steam chemistry (Fig. 70) [136].
5. Modification of the processes of nucleation, condensation, and
formation of liquid films and deposition. Significant benefits will be achieved
if these basic processes can be controlled. Efficiency improvements will be
realized by better control over moisture levels (such as through moisture
removal techniques) and slowing down the dynamics of droplet formation.
6. Improving flow-path design, particularly in the last stage of the LP
and in exhausts hoods. It is ironic that despite the recent advances in threedimensional
aerodynamic analysis design, the last LP stage in fossil fired
units remains the least thermodynamically efficient row in the steam path,
even though it has the largest available energy. Programs to use advanced
tools such as three-dimensional CFD codes to optimize the design of the
Figure 70 Rankine cycle deposition and corrosion sites.
Copyright © 2003 Marcel Dekker, Inc.