Page 40 - NAVAL FORCES 03/2017

Protection & Mobility

The guided-missile destroyer USS “Zumwalt” (DDG 1000)
is one of the US Navy’s most technologically-advanced surface ships.
Features

The generators powered by these engines the combustion process, in turn enabling the the UK Parliament’s Defence Select Commit-
feed two main high-voltage switchboards that engine to produce more power. Recuperation tee were told this, they were not impressed.
distribute Alternating Current (AC) power to uses a separate heat exchanger system to re- “It is astonishing that the specification for
all the consumers, either at 4,160V to the GE turn heat energy (but not gas) from the exhaust the Type 45 did not include the requirement
Power Conversion VDM 25000 propulsion to the combustion chamber so that less fuel for the ships to operate at full capacity – and
converters, or via transformers at 440V and has to be burned to produce a given amount for sustained periods – in hot regions such as
115V to the weapons and ship services. of power. the Gulf. The UK’s enduring presence in the
For propulsion, the power is fed to air a pair The problem, according to testimony before Gulf should have made it a key requirement
of 20 MW Advanced Induction Motors (AIM) the UK Parliament’s Defence Select Commit- for the engines. The fact that it was not was
via Pulse Width Modulated (PWM) power tee, is that the intercooler, which ultimately an inexcusable failing and one which must
converters that control their speed. The AIMs uses seawater to cool the intake charge, is not not be repeated in the Type 26 and GPFF pro-
drive two shafts directly, without a gearbox. up to the job in the high water temperatures grammes” (The GPFF is the simpler, more
The WR-21 gas turbine is an ambitious and encountered in the Gulf. This has triggered to- export friendly general purpose frigate that is
advanced design that uses a combination of tal power failures because when the two WR- to make up the remainder of the Royal Navy’s
intercooling and recuperation to enable fuel 21s failed to keep up with the power demands, frigate fleet alongside the ships of the curtailed
efficient operation over a much wider range of extra load would be automatically placed on Type 26 programme.)
power settings than is possible with conven- the ship’s diesel generators and, because they In the view of two retired Royal Navy en-
tional gas turbines. Intercooling uses a heat were not designed to handle it, they would gineers providing written evidence to the
exchanger to reduce the temperature of the then trip out leaving the ship effectively dead com mittee, the failure to correct the WR-21’s
airflow between the compressor and the com- in the water. problems before service entry can be put
bustor, increasing the air density so that there Yet the Type 45’s powerplant met the MoD’s down to the closure of the Naval Marine
is more oxygen in a given volume available to operational temperature specifications. When Wing of the National Gas Turbine Establish-
ment at Pyestock, which carried out testing of
British naval gas turbines independently of the
manufacturers.
Project Napier Fixes

Fixing the problems is the purpose of Project
Napier, which centres on improvements to the
WR-21’s intercooling system, some changes
to the electrical distribution system and extra
diesel generators.
Project Napier started in 2014 and com-
prises a near term Equipment Improvement
Plan (EIP) and a longer term Power Improve-
ment Plan (PIP).
The EIP is intended to increase reliability
and meet the original design intent. To this end,
incremental introduction of improvements to
system integration plus modifications to the
converters and converter cabinets have been
implemented, along with experience-driven

f A dedicated Rolls-Royce facility in Bristol,
UK to test the gas turbines on the Royal Navy’s
Type 45 fleet will support the destroyers’
demanding schedules.
38 NAVAL FORCES III/2017