CVF - Integrated Power & Propulsion System

The combined turbine diesel propulsion system consists of two Rolls-Royce Marine 36MW MT30 gas turbine alternators, providing over 70MW and four diesel engines providing approximately 40MW, with the total installed power approaching 110MW. Should they require replacing, they can be easily removed from the vessel, even on deployment, eliminating the need for extensive maintenance.

The Aircraft Carrier Alliance (ACA) is a single integrated team formed from Babcock, BAE Systems, Thales UK and the MOD (which acts as both partner and client.) It is responsible for delivering the Queen Elizabeth class ships to time and cost. The Power and Propulsion Sub-Alliance comprises of Thales UK (acting on behalf of the Main Alliance), Rolls-Royce, GE (formerly Converteam) and L3, and is responsible for the design, procurement, manufacture, integration, test and delivery of the Integrated Power & Propulsion System.

In 2008, General Electric won a contract to deliver the major elements of the Integrated Full Electric Propulsion (IFEP) systems for the new Queen Elizabeth class (QEC) carriers. The IFEP comprises all shipboard electrical power generation and propulsion systems and features GE’s Advanced Induction Motor (AIM) technology, which delivers increased fuel efficiency plus high levels of survivability.

The all-electrical power and propulsion approach improves ship survivability by decoupling the placement of the turbines and the generators from the propellers’ mechanical drive. Power generation and propulsion equipment is instead distributed across several independent compartments rather than concentrated into a single space or small number of spaces.

Rolls-Royce pioneered the use of aero-derivative gas turbines in marine propulsion, primarily for naval vessels. The MT30 Gas turbines that power the Queen Elizabeth class aircraft carriers, at 36 MW (around 50,000 hp), are the most powerful in-service gas turbines in the world. Designed for the 21st century navies, the MT30 integrates the very latest in gas turbine technology to give efficiency and reliability with a market leading power to weight ratio. It has been designed to minimise maintenance costs and first entered service in 2008 powering the US Navy’s first littoral combat ship – USS Freedom. Produced in Bristol, the MT30 Gas turbine and alternator sets are each located under one of the ships islands:

• MT30 Gas turbine derived from the highly successful Trent engine programme
• Alternator supplied by GE (formerly Converteam)
• Hydraulic start skid
• Fire protection system
• UPS (Uninterruptible power supply)

The prime movers selected for the generating sets are two 12-cylinder and two 16-cylinder Wärtsilä 38 engines for each ship. They supply 40 MW of the total installed power of over 100 MW, the remainder coming from two gas turbine alternators. Wärtsilä engines were selected for their durability, reliability, cost-efficiency, extended interval time between maintenance, and full compliance with current and foreseen emission regulations.

The four diesel engines are directly coupled to the 2 × 12V38 8.7 MW / 11,700 hp and 2 × 16V38 11.6 MW / 15,600 hp generating sets. Together, each power unit weighs approximately 200 tonnes - the weight of two medium size passenger jets. The diesel generator sets provide sufficient electrical power to drive the ship at cruise speeds, but when higher speed is required, two Gas Turbine Alternators would also be used. Together they produce 109MW of power, enough to power a medium-sized town.

Rolls-Royce supplies a complete range of steering gear – suitable for all ship sizes and types. For the QE class, we designed and manufactured the complete steering gear system, integrating two steering gear rotary vane actuators. All steering gears are delivered as a complete system, including hydraulic power units, control and alarm systems.

Rotary vane steering gears are very compact – they include integrated rudder carrier bearings (lubricated by the hydraulic system oil) and are typically 50 – 60 per cent of the weight of some competing designs, with low noise and vibration. Operationally RR rotary vane design ensures full torque is available at all rudder angles. It gives more flexibility, as the steering gear is optimised for the type of rudder it will be used with. Units come in 2, 3 and 4 vane variants with 70°, 45° and 35° rudder angles respectively:

• Rolls-Royce Marine RV2600-3 Vane Unit developing a maximum 1845 kNm of torque per unit
• Lightweight: typically 50-60 per cent of a RAM-type steering gear
• Bespoke design based on the Type 45 hull cartridge methodology
• Two independent rudders per vessel
• Twisted design rudder blade to minimise cavitation effects

Four Neptune retractable fins are installed on the QE class, manufactured at the RR Dunfermline facility. The Neptune range uses a retractable fin that folds into slots in the hull, flush with the vessel’s side, and is also used for cruise ships and larger ferries. The one-piece fin is designed to maximise lift properties and minimise drag:

• Neptune 400 type with a 11.5m2 fin area
• Four fins per vessel mounted as pairs Forward and Aft
• 79 per cent roll reduction @ 18 Knots
• Fins retract when not required improving vessel safety when manoeuvring

Rolls-Royce is a world leader in propeller design and supplies controllable pitch propellers, fixed pitch propellers, and the innovative adjustable bolted propeller. Our propellers deliver good fuel economy, low vibration and noise levels and minimal cavitation. The adjustable bolted propeller (ABP) - two per ship - allows the most efficient blade matching for optimum efficiency while simplifying installation. It uses a hollow hub with five blades bolted from the inside. Slotted holes in the hub allow the blade pitch angle to be adjusted in service to compensate for variations in hull resistance through-life. The propellers’ overall weight is reduced for easier shipment, handling and mounting. Individual blades can be replaced without dry docking.

The propellers, manufactured in Sweden, each deliver around 50,000 hp - the highest power propeller ever produced by Rolls-Royce:

• 7m in diameter and weighs 33 tonnes
• Made from nickel aluminium bronze
• Stepless blade pitch adjustment
• Individual underwater blade replacement if damaged