Handbook of Turbomachinery Second Edition Revised - Ventech!

number of design variables, robust optimization algorithms that are capable
of addressing multiple disciplines and design objectives simultaneously, and
low computational turnaround time so that the design changes can be
addressed in a reasonable time need to be addressed. A robust and efficient
optimization procedure that is capable of addressing all these concerns will
be a very valuable tool for the designer. Improvements in existing designs
for better-performance, new designs that, in addition to optimum
performance, also involve low design cycle cost, the ability to investigate
the impact of new concepts on the overall design, and material cost savings
associated with cooler blade temperatures are some of the capabilities of
such a procedure.
The main areas that need to be addressed in establishing a
multidisciplinary optimization procedure for gas turbine application are
(1) disciplines to be addressed, (2) appropriate design objectives, (3) relevant
design variables, (4) constraints, (5) optimization algorithm(s), (6) analysis
tools (available or to be developed), (7) geometry specifications (e.g., Bezier–
Bernstein polynomials for blade geometry), (8) computational resources and
strategy, (9) sensitivity analysis, and (10) validation of the procedure.
Usually, the disciplines that need to be addressed will be dictated by the
design objectives.
One of the best means of achieving higher efficiency in gas turbine
engines is to raise the temperature of the gas flow entering the turbine. Since
the high-temperature environment in the turbine affects the life of the blade
and its structural integrity, the efficient removal of heat from the blade
interior is very important. Also, the geometry of the blade and the choice of
appropriate materials that are capable of withstanding the high temperatures
will be affected by manufacturability and structural integrity concerns.
A method to alleviate this problem is to use effective turbine blade-cooling
mechanisms and blade geometry such that the temperatures stay within
acceptable levels in the blade. Since the cooling air is supplied by the
compressor, it is essential to maintain the coolant air-flow rate low so that
overall engine performance is not degraded. Another area of interest is the
need to minimize aerodynamic losses in order to improve overall
performance. Thus, the design of gas turbine blades is a multidisciplinary
problem that requires the integration of several disciplines such as
aerodynamics, heat transfer, structures, vibration, etc. For an efficient and
comprehensive design, these disciplines need to be addressed simultaneously.
In general, such an optimization problem is nonlinear and has
several objective functions, constraints, and design variables. Many of the
existing optimization procedures can address only a single objective function
and multiple constraints at a time. A multidisciplinary design optimization
Copyright © 2003 Marcel Dekker, Inc.