Efficient and robust rotating machines: Design innovations and international standards
Submitting Institution
University of BathUnit of Assessment
Aeronautical, Mechanical, Chemical and Manufacturing EngineeringSummary Impact Type
TechnologicalResearch Subject Area(s)
Engineering: Electrical and Electronic Engineering, Mechanical Engineering, Interdisciplinary Engineering
Summary of the impact
Rotating machines are ubiquitous key elements for power generation.
Research has led to impacts
that have improved the design and performance of rotating machinery for
component vendors,
original equipment manufacturers and end-users:
(a) Siemens has adopted new designs of interstage turbine disc rim seals
that reduce gas
leakage paths and hence increase power efficiency/fuel savings in power
based gas
turbines. The impacts have protected 4-5 R&D jobs, improved seal
product design, and
enabled reallocation of corporate budgets.
(b) Integrated dynamic/thermal analysis has enabled preventive design
against unstable shaft
thermal bending, known as the Morton Effect in the field of
turbomachinery.
(c) Research into the functionality of active magnetic bearings has been
transferred into the
standard ISO 14839 1-4 that has brought technology normalisation,
involving changes to
company design practices, to the field. Part 4 was published in 2012.
(d) An oil-free experimental facility has been delivered to GE Global
Research (Munich) to aid in
their compressor designs for subsea machines. GE has benefitted through
knowledge
transfer and the training of engineers for the design of new machines.
Underpinning research
Key researchers
Sustained research activity has been driven for more than twenty years in
the rotating machines
field by Professor CR Burrows (Professor from 1987, emeritus since 2007),
Professor PS Keogh
(Lecturer 1990-1996, Senior Lecturer 1996-2003, Reader 2003-2007,
Professor since 2007), Gary
Lock (Lecturer 1995-2001, Senior Lecturer 2001-2008, Reader 2008-2012,
Professor since 2012),
Mike Owen (Professor from 1989, emeritus since 2008), Necip Sahinkaya
(Reader since 2001)
and Mike Wilson (Lecturer 1996-2003, Senior Lecturer since 2003). Their
activities cover gas
turbine fluid flow and heat transfer, motion induced shaft heat transfer,
and the functionality of
active magnetic bearing and touchdown bearings for high speed machines.
Their effort is focused
in the Gas Turbine Research Unit and the Centre for Power Transmission and
Motion Control.
Key insights and projects
Fundamental research has been funded mainly by the EPSRC in collaboration
with industrial
partners. Insights into the research and associated EPSRC projects (with
project codes, dates, and
collaborating industrial partners) are provided in the following text.
Owen led projects on heat transfer and cooling within turbine stage
cavities (GR/J07907/01 from
1993-1996; GR/K27360/01 from 1994-1997 with European Gas Turbines; and
GR/M08868/01 from
1999-2002 with European Gas Turbines). Lock provided a focus on turbine
leakage/cooling/flows
by leading projects GR/L48034/01 from 1997-2000 with European Gas
Turbines; and
GR/N33980/01 from 2000-2004 with Alstom/Rolls-Royce. This led to the
formulation of two
research projects on gas ingestion and ingress through novel designs of
rim seals (EP/G069107/1
from 2009-2012; EP/J014826/1 from 2012-2015), both in collaboration with
Siemens Industrial
Turbomachinery, previously European Gas Turbines.
Keogh investigated the heat transfer from fluid film bearings to rotating
shafts under dynamic
motions (GR/J15568/01 from 1993-1997) to highlight the particular
conditions under which a shaft
may experience asymmetric heating that leads to runaway thermal bending.
Burrows and Keogh
led activities relating to the design of modern control strategies for
magnetic bearing levitated
rotors (GR/J15575/01 from 1993-1996; GR/L62238/01 from 1998-2001; and
GR/R45277/01 from
2001-2005, both with Edwards High Vacuum). Research into high speed
rotor/touchdown bearing
contact control was led by Keogh through EP/D031389/1 from 2006-2009 in
collaboration with
Goodrich, now part of Rolls-Royce as Aero Engine Controls.
Key outputs
Research embraces thermofluidic influences on the dynamics and control of
rotating machines.
The group embodies one of the world centres for experimental research in
rotating-disc systems,
particularly in the theory, calibration and application of thermal imaging
techniques to measure the
heat transfer on rotating surfaces [1]. The prediction and measurement of
flows/ingress through
turbine disc rim seals is exemplified in [2, 3], which has had important
implications for gas turbine
efficiency.
The first identification of the phenomenon of runaway thermal bending of
a shaft within a
hydrodynamic bearing, requiring machine shutdown, is given in [4]. This is
now known as the
Morton Effect to designers of turbomachinery. This can be negated through
passive machine
design. Studies on the active control of magnetic bearings and their
associated touchdown
bearings have realised contributions to enable system design and optimised
rotating machine
performance under contact-free levitation. An understanding of
rotor/touchdown bearing contact
modes has also been established in [5, 6]. When rotor/touchdown contact
events occur, the
mechanical and thermal integrity of the system may be compromised, hence
these research
outputs have provided a basis for preventative design.
References to the research
(* references that best indicate quality)
1. VU Kakade, GD Lock, M Wilson, JM Owen and JE Mayhew. Accurate heat
transfer
measurements using thermochromic liquid crystals. Part 2: Application to
rotating disc,
2008, International Journal of Heat and Fluid Flow, 30, 950-959.
DOI: 10.1016/j.ijheatfluidflow.2009.04.005
2. JM Owen, OJ Pountney and GD Lock, Prediction of ingress through
turbine rim seals.
Part 2: Combined ingress, 2012, ASME Journal of Turbomachinery, 134,
031013.
DOI: 10.1115/1.4003071 (First published as a conference paper in 2010)
3*. CM Sangan, OJ Pountney, K Zhou, M Wilson, JM Owen and GD Lock.
Experimental
measurements of ingestion through turbine rim seals. Part 1:
Externally-induced ingress,
2012, 135, ASME Journal of Turbomachinery, 021012. DOI:
10.1115/1.4006609
[Received a Best Paper Award from the Heat Transfer Committee of the ASME
Turbo
Expo 2011]
4*. PS. Keogh and PG Morton, The dynamic nature of rotor thermal bending
due to unsteady
lubricant shearing within a bearing, 1994, Proceedings of the Royal
Society:
Mathematical and Physical Sciences, 445, 273-290. DOI:
10.1098/rspa.1994.0061
5*. PS Keogh, MOT Cole, MN Sahinkaya and CR Burrows. On the control of
synchronous
vibration in rotor/magnetic bearing systems involving auxiliary bearing
contact, 2004,
ASME Journal of Engineering for Gas Turbines and Power, 126,
366-372.
DOI: 10.1115/1.1689362
6. IS Cade, PS Keogh and MN Sahinkaya. Transient rotor/active magnetic
bearing control
using sampled wavelet coefficients, 549-555, ASME Journal of Engineering
for Gas
Turbines and Power, 129, 2007. DOI: 10.1115/1.2436570 [Received a
Best Paper Award
from the Structures and Dynamics Committee of the ASME Turbo Expo 2006]
Details of the impact
The specific cases (a) — (d) of section 1 fall under the general
categories of `Economic impacts'
and `Impacts on practitioners and professional services'.
(a) Gas turbine rim seal design advances
Siemens is a large global company with an Energy product group. It has a
vested interest in
manufacturing more efficient power generation products so as to increase
market share. Siemens
Industrial Turbomachinery employs 1,600 people in Lincoln for the design,
manufacture and
maintenance of gas turbines in the power ranges from 5 MW to 15 MW.
Research and design
innovations at Bath have had significant economic and environmental impact
at Siemens. The
impact has contributed significantly to the company's current level of
technology and
competitiveness in the power generation industry has helped to protect
jobs in Lincoln, supported
the local and wider UK economy, and has created greener technology with a
reduction in CO2
through improved engine efficiency. The knowledge transfer of the research
from Bath to Siemens
has been facilitated by a Knowledge Transfer Associate (Teuber).
(i) New rim seal components and improved thermal efficiency
The Bath research [2, 3] has led directly to new rim seal components.
These patented component
designs ([A] and patent applications from Siemens: 2013P00020EP and
2013P00483EP, currently
embargoed) evolved through a carefully organised programme of interaction
between Siemens
and Bath, via a Knowledge Transfer Partnership. Economic impacts
have been evidenced
through improved products, jobs protected, and reallocation of
corporate budgets as the
Director of Future Technology within Siemens (Lincoln) states that an
improvement in thermal
efficiency of 0.4% has been confirmed [B]. Furthermore:
`Internal funding directly from Technology looking at the development
of seals and improved
secondary air systems analysis will be in the region of €1M-1.5M over
five years. To this I
would add the indirect effort that comes about through related engine
design and concept
development activity. Here we have ~4 to 5 people full time equivalent @
approx €1M/annum.'
(ii) Changing and improving the design methods at Siemens
The research at Bath has achieved impact on practitioners/engineers
through changed and
improved design practices used at Siemens. Specifically, a
new theoretical model for rim seal
ingress has been developed at Bath and translated into a practical design
tool (used in 2nd Flow)
for the Siemens' secondary air system (SAS) [C]. It is stated in [B] that:
`Avoidance of a single instrumented engine test has reduced the engine
development budget by
over £250k and the development programme by 3 months. Reduced lead times
for engine
development can be equated to additional opportunity for engine sales.'
and
`Increasing the life of these parts therefore makes the company's
service plans more attractive
to the customer and secures the jobs in its service organisation. Each
additional long term
service agreement secured is a sale valued at between £250k and £500k
per year for 5 to 10
years.'
Each additional sale of a 15 MW class engine represents a sale valued at
over £5M. Siemens
branches in the USA, Sweden and Germany have validated their own SAS tools
and have
assessed 2nd Flow as the major SAS design tool [D]. This has
enabled Siemens to reallocate
corporate budgets towards research in the Energy sector.
(b) Design against runaway shaft thermal bending in rotating machines
The dynamic process of runaway shaft thermal bending, known as the Morton
Effect, was first
explained in reference [4]. Since that publication, design and field
engineers have reported
numerous instances of problematic turbomachines that were not meeting
specification due to
excessive vibration. These engineers now design against occurrence of the
Morton Effect by
reducing a thermal-orbit loop gain system parameter below a definable
threshold value. Impact of
this research is therefore evident through traceable references
from practitioners (engineers)
to reference [4]. Cases of the Morton Effect have been
reported through the
Pump/Turbomachinery Symposia, organised by the Turbomachinery Laboratory,
Texas A&M
University, and held annually in Houston. The Director of the
Turbomachinery Laboratory, who has
extensive industrial engagement with the oil and gas sector, comments [E]:
`After their work, a stream of papers appeared involving case studies
of real machines with
"synchronously unstable" vibration characteristics. The outcome was
comparable to the
discovery of a previously undiagnosed disease that — once recognized —
was found to be
widely distributed and now predictable, avoidable, and curable.'
(c) International standards for Active Magnetic Bearing (AMB) based
rotating machines
The group has led research into the rigorous design of active magnetic
bearing (AMB) control
strategies for the stable levitation of flexible rotors, and has addressed
the understanding of the
dynamics of rotor drop onto touchdown bearings [5, 6]. The impact of this
research is now evident
through its incorporation into new and modified professional
standards.
A degree of standardization was required following the early industrial
application of AMBs over the
1980s and 1990s, when failures were reported. Recognition of the Bath
research became evident
through invitations to serve on the International Organization for
Standardization (ISO)
TC108/SC2/WG7 AMB Project committee (Burrows, 1996; Keogh, 1998;
Sahinkaya, 2003) with
other academic researchers and industrial technologists from the USA,
Switzerland, Germany,
France, and Japan. Bath is now the only institution with three
representatives. This committee has
encouraged the expansion of applications from vacuum pumps, motors,
generators, flywheel
energy storage, to compressors for the oil and gas sector. The Bath group
pioneered the technique
of automatic balancing of levitated flexible rotors and has been central
to the understanding of
AMB touchdown dynamics that arise from rotor de-levitation. The Bath input
has been embedded
into the standard, ISO 14839 (Parts 1-4) [F]. Since 2009, Keogh has led
ISO/TC108/SC2/WG7 as
Convenor and Part 4 was published in 2012. Beneficiaries include vendors
(S2M, MECOS,
Calnetix, Waukesha), original equipment manufacturers (Siemens, GE, Solar
Turbines, Edwards)
and end-users (Shell, Total, Statoil, Exxon). The Director of Technology,
Calnetix, states [G]:
`As Director of Technology of Calnetix, an innovation led company
based near Los Angeles,
USA, I know well that important technical issues must be overcome to
ensure that high
performance machines operate reliably and safely in their intended
environments. The input
from the Bath team has contributed significantly to the development of
rigorous standards for
AMB operation in a range of industrial applications. The performance
metrics required by the
standard are very useful and practical, enabling Calnetix to advance the
robustness of its
machine designs. This has helped Calnetix increase market penetration -
in fact, annual
revenues of Calnetix have tripled over the past five years.'
(d) Oil-free compressor design
International recognition of the Bath input is attested by the invitation
of GE Global Research
(Munich) in 2012 for the Bath team to design and deliver an experimental
facility for oil-free
compressor dynamic investigations. The research from Bath has also
underpinned collaboration
and impact with GE through knowledge transfer. The
Principal Engineer: Electric Drivetrain, GE
Global Research, states [H]:
`I was aware of the previous Bath AMB research into the control of
levitated flexible rotors. Such
rotors are pertinent to the oil and gas compressor rotors manufactured
by GE. A contract was
therefore arranged for Bath to design and deliver an experimental
rotor/AMB facility to GE
Global Research (Munich) to enable investigation of the system
requirements for compressors,
particularly in subsea applications. Professor Keogh and Dr Sahinkaya
have since interacted
with and guided the GE engineering team from April 2012 to July 2013
through knowledge
transfer of the principles that are embedded within ISO 14839
guidelines.'
The experimental facility has been used to train five practitioners
(design engineers) for the
development of oil-free compressors.
Sources to corroborate the impact
A. Finned seal for gas turbine, Patent 2012P08852, JM Owen, CM
Sangan, GD Lock, KM
Tham, VP Laurello and CP Lee, 2012.
B. Corroborative statement from Director of Future Technology Siemens
(Lincoln), 12 April
2013.
C. Implementation of rim sealing Orifice Model in 2nd
Flow, R Teuber, Siemens Technical
Report TR 12/124, July 2012.
D. Corroborative statement from Siemens (Core Competence Owner Secondary
Air
System), 4 October 2013.
E. Corroborative statement from Director of Turbomachinery Laboratory,
Texas A&M
University, 13 September 2013.
F. ISO 14839 Mechanical vibration — Vibration of Rotating Machinery
Equipped with Active
Magnetic Bearings: Part 1: Vocabulary (2002); Part 2: Evaluation of
vibration (2004);
Part 3: Evaluation of stability margin (2006); Part 4: Technical
guidelines (2012).
G. Corroborative statement from Director of Technology, Calnetix
Technologies LLC (Los
Angeles), 16 August 2013.
H. Corroborative statement from Principal Engineer: Electric Drivetrain,
GE Global
Research Centre (Munich), 8 August 2013.