Turbomachinery: Fundamentals, Selection and Preliminary Design

400 Pages·2021·11.248 MB·English

by  Marco Gambini, Michela Vellini

Springer Tracts in Mechanical Engineering
Marco Gambini
Michela Vellini
Turbomachinery
Fundamentals, Selection and
Preliminary Design
Springer Tracts in Mechanical Engineering
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Marco Gambini Michela Vellini
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Turbomachinery
Fundamentals, Selection and Preliminary
Design
123
MarcoGambini Michela Vellini
Department ofIndustrial Engineering Department ofIndustrial Engineering
University of RomeTor Vergata University of RomeTor Vergata
Rome, Italy Rome, Italy
ISSN 2195-9862 ISSN 2195-9870 (electronic)
SpringerTracts inMechanical Engineering
ISBN978-3-030-51298-9 ISBN978-3-030-51299-6 (eBook)
https://doi.org/10.1007/978-3-030-51299-6
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Preface
Turbomachines are extremely important from a technological point of view: they
are the basis of most energy conversion systems for electricity generation (steam
cycles,gasturbines,combinedsteam-gascycles,aswellashydroelectricandwind
power plants) and for heat and power production (cogeneration plants), for aero-
nautical propulsion (gas turbines), for fluid transport and compression (compres-
sors, fans and pumps) in both industrial and civil applications.
For several decades, academic and industrial studies have extensively investi-
gated turbomachines, favoring their formidable technological evolution. One
example of this technological evolution is gas turbines for aeronautical and sta-
tionary applications: aeronautical gas turbines are the most technologically
sophisticatedandbestperformingenginesthatthemarketcanoffer.Similarly,also
the technological evolution of gas turbines for stationary applications has been
remarkable:togetherwiththemostadvancedsteamturbines,theyrealizenowadays
combined steam-gas cycles that attain efficiencies of above 60%, becoming the
most efficient and clean energy conversion systems available on the market.
The design of a turbomachinery is complex and laborious: it starts with the
choice of the appropriate turbomachinery stage (radial, mixed flow, axial),
including rotational speed and number of stages; it continues with the preliminary
design of each stage and ends with the detailing design, conducted with three-
dimensional computational fluid-dynamic analysis (CFD) techniques, including
sophisticated structural, acoustic and mechanical analyses.
In the preliminary design, a one-dimensional performance evaluation of each
single stage is carried out (mean-line analysis): in this phase, kinematic (velocity
triangles),thermodynamic (fluidconditionsupstreamanddownstreamofthestator
androtor)andgeometricparameters(inlet/outletdiameters,statorandrotorlength,
blade heights, chord, pitch and solidity, etc.) are defined. If these parameters are
calculatedinthemosteffectiveway,byusing themostadvancedlosscorrelations,
thentheturbomachineryefficiencycanbepredictedwithreasonableaccuracyand,in
most cases, in good agreement with the CFD calculations. This means that the
subsequentdetailedaerodynamicdesignphase,conductedwithadvancedcalculation
vii
viii Preface
tools that require a significant commitment of resources in economic and temporal
terms,canbesignificantlyreduced.
Precisely for these reasons, to reduce design costs and time, it is essential to
perform these first design phases (selection and preliminary design of turboma-
chinery) correctly and realistically. In the subsequent phases, indeed, although
greater levels of details are reached, any changes to the basic configuration would
beparticularlycomplicatedandexpensive,alsotakingintoaccountthatmanyother
disciplines are involved in the detailed design of turbomachinery (structural,
aerodynamic, acoustic, mechanical).
For over thirty years, the authors of this book have lectured, investigated and
designedturbomachinesandenergysystemsinwhichtheyareinstalled:conventional
steam power plants, gas turbines and combined cycles for power production,
cogenerationplants,advancedpowerplantswithlowCO emissions,etc.Inrecent
2
years,significantchangeshavebeentakingplaceinthissector,especiallyinorderto
limitCO emissionsandtodevelopnewconversionsystemsintegratedwithrenew-
2
ableenergysources:newthermodynamiccyclesintegratedwithpre-combustionCO
2
removalsystemsorpost-combustionones,newthermodynamiccyclesusingsuper-
criticalCO (sCO ),mixturesofCO -basedfluidsandothernon-conventionalfluids
2 2 2
tobeintegratedinCSPplants(concentratingsolarpower),OrganicRankineCycle
(ORCs)coupledwithrenewablesources(solar,geothermal)andwithlowtemperature
thermal sources, to name the most promising. In essence, these are mostly
turbomachinery-based conversion systems operated with unconventional fluids
(different from air, exhaust gases, water and water vapor); these fluids cannot be
treatedwiththeschematizationvalidforperfectgasesorwiththeclassicequationsof
state valid for water–water vapor. Historically, however, correlations used in the
preliminarydesignofaturbomachineryarereferredtoconventionalfluids(gastur-
binesandsteamturbines,compressorsoperatingwithgasessimilartoperfectgases).
Basedontheabove,thisbookaimstoprovideuserswithaselectionprocessand
a preliminary design procedure of turbomachinery with the following features:
(cid:129) optimize the stage kinematics, thermodynamics and geometry already in the
preliminary design phase, using geometric correlations and loss models, pro-
posedinthemostrecentliteratureofthesector,abletopredicttheturbomachine
efficiency with good accuracy and, in most cases, in excellent agreement with
CFD calculations;
(cid:129) be applicable to both conventional and non-conventional fluids;
(cid:129) analyze homogeneously all the turbomachine types taken into consideration
(axialandradialturbines,axialandcentrifugalcompressors,centrifugalpumps);
this procedure calculates the kinematics, thermodynamics, geometry and stage
losses in sequence, after identifying exactly the input parameters necessary to
develop these numerical calculations;
(cid:129) guide the user in choosing the sets of input parameters according to the most
recent design developments.
Preface ix
Given itspeculiarities, thisbook isaddressed tobachelor’sandmaster’sdegree
students in industrial, mechanical and energy engineering, and to researchers,
professionalsandtechniciansoftheenergysystemsandturbomachinerysector.For
alltheseusers,thisbookcanbecomeaninstrumenttoguidethemeffectively“step
by step” in the first sizing of turbomachines and in the verification of their tech-
nological feasibility when these turbomachines are conceived for new conversion
systems operated with unconventional fluids.
The book is divided into eight chapters.
Chapter1isanintroductorychapterandisasynthesisofthebooktitledLecture
notes on Fluid Machines—M. Gambini, M. Vellini (in Italian), 2007, adopted for
the Turbomachinery and Energy Systems courses for students of the bachelor’s
Degree in Mechanical and Energy Engineering of the University of Rome Tor
Vergata. This chapter intends to provide a summary of the basic principles
of thermodynamics and fluid-dynamics applied to turbomachinery necessary to
define all the performance parameters (work transfer, isentropic and polytropic
efficiency,nozzlesanddiffusersefficiency,degreeofreactionandsoon)usedinthe
proposed procedures of turbomachinery selection and design.
Chapter 2 concerns the selection process of the turbomachine configuration
(radial, mixed flow, axial) to be used in a specific application defined by the
operating conditions (type offluid, mass flow rate, pressure and inlet temperature,
outletpressure).Thisselectionprocessisbasedontheapplicationofthesimilitude
theory, which allows to “capitalize” all previous experience in the turbomachinery
sector by transferring the results obtained for an existing machine, considered as a
model, to another machine, to be designed, which is “similar” to the model one,
used as a reference.
The following chapters, from Chaps. 3 to 7, explain the preliminary design
procedures of the five turbomachinery configurations here considered: axial tur-
bines (Chap. 3), axial compressors (Chap. 4), radial turbines (Chap. 5), centrifugal
compressors (Chap. 6) and centrifugal pumps (Chap. 7).
The book ends with a chapter (Chap. 8) entirely dedicated to numerical appli-
cations of the proposed procedures for the selection and preliminary design of
turbomachines. In particular, the concentrating solar power (CSP) sector has been
chosen as a case study, for which several unconventional conversion cycles are
proposed: closed Brayton cycles operated with helium, argon, supercritical CO
2
(sCO ), also in combined arrangements with bottoming cycles operated with
2
organic fluids (ORC). When defining the thermodynamic cycle of each power
block, preliminary hypotheses on the turbomachinery efficiencies must be made.
These hypotheses must necessarily be verified through the calculation of the tur-
bomachine losses, which, in turn, requires assessing of the kinematics, thermody-
namics and geometry of the turbomachine (Chaps. 3–7). In fact, only if these
hypotheses are validated, the reliability of the calculation of the cycles’ perfor-
mance is ensured.
x Preface
Therefore, the organization of the book is the following:
It is evident that the preliminary design procedures (Chaps. 3–7) are developed
inparallel.So,somerepetitionsofsimilartopicsforeachtypeofturbomachinecan
occur, but the preliminary design procedure becomes homogeneous for all turbo-
machinesandexhaustivefor eachofthem;therefore,thereadercanstudyindepth
only one type of turbomachine without having to analyze all the other ones. For
example, one interested in radial compressor can read through Chaps. 1–2–6–8
only.
The authors hope that the efforts made in the elaboration of an organic and
homogeneous textbook on turbomachinery principles and design will be beneficial
for the cultural and professional enrichment of a wide audience of users who,
whether for study,researchorwork,will investigate newenergy systems andtheir
related turbomachines.
Rome, Italy Marco Gambini
May 2020 Michela Vellini