TEIGNBRIDGE UNVEILS RESULTS OF EFFICIENT PROPULSION PROJECT
Teignbridge Propellers shared the results of a 2.5 year, UK-funded demonstration project into efficient propulsion systems in September. The HEPS project was funded and developed as a partnership with the Energy Technologies Institute (ETI) - a public-private partnership between global energy and engineering companies and the UK government with the mission to accelerate the development of close-to-market, low carbon technologies.
During the course of the £3 million project, Teignbridge Propellers has investigated three innovative areas of propeller performance improvement, targeted at the reduction of fuel and associated greenhouse gas (GHG) emissions from the large fleet Handysize bulk carriers and product tankers, ferries, offshore service vessels and container feeders that operate in UK waters. The innovations and associated learning however, can be applied to almost all commercial, leisure and military vessels. The three areas of innovation in the project include:
1) Development of an integrated ‘ship as a system’ design process to enable optimisation of the blade geometry for maximum hydrodynamic efficiency followed by testing of the optimised performance in the context of a realistic representation of the vessel’s mission profile. The process typically delivers a 3.5% to 4.0% increase in hydrodynamic efficiency over a baseline performance of the equivalent Wageningen B-Series propeller +1.0% (typical representation of the vessels operating in this fleet).
2) Development of a replaceable blade concept – the Clamp on Blade (CoB) propeller. The CoB has a smaller hub to diameter ratio than any other replaceable blade propeller on the market. The innovative design also enables a bolt head free blade palm. This pair of features improves efficiency by more than 2.0% over competing designs.
3) Development of a pitch modification system – currently in proof of concept scale prototyping phase. Watch this space!
Hydrodynamic efficiency gains vary with vessel type and mission profile, but confidence in the performance levels detailed above have been established through validated numerical simulations in CFD and scale model testing; employing Teignbridge’s test vessel – HRV1 for the purpose. The methodology used and results collected have been scrutinised by the ETI, its partner members and industry experts.
Propeller designs often suffer from imperfect visibility on the exact performance of a new design at full-scale and in a real-world deployment. Teignbridge has developed a floating prototype propulsion system laboratory – HRV1 (Hydrodynamic Research Vessel 1) - for the purpose of physical model testing and rapid prototyping of new ideas.
HRV1 provides the facility to sea trial propellers of up to 1200m in diameter, reducing scaling effects by establishing fully turbulent flow over the model propellers (compared to laminar or transitional flow associated with typical smaller scale models of between 200m to 400m diameter) and reducing the mathematical jump from model to full scale by a factor of 17 to a factor of 4 for a 5000mm propeller.In order to accurately capture and evaluate propeller performance, HRV1 is fitted with a sophisticated array of sensors - the heart of which is a propeller shaft mounted fibre optic thrust and torque sensor array developed by a partnership between Teignbridge and City, University of London. This piece of equipment is essential to establishing the hydrodynamic performance (thrust and torque) of a propeller and is necessarily sensitive in order to accurately capture propeller thrust (notoriously difficult to measure), measuring changes in propeller shaft geometry down to 10 picometres (0.00000001mm). The graph below shows the results of a slow speed, high torque propeller test completed on HRV1 alongside performance prediction data simulated by Teignbridge using computation fluid dynamics (CFD).
In addition to the HRV1’s fibre optic strain gauge system, data is also captured from a pair of Doppler Velocity Logs to measure speed through water, accurate on-shaft RPM sensors, six degree-of-freedom motion measurement and various CAN bus data feeds including environmental and engine data. LabVIEW data collection software is used to collate and pre-process performance data live onboard before communicating through a wireless link with Teignbridge HQ back on dry land. HRV1 operates out of Torquay harbour in South Devon, UK, and uses the sheltered waters of Torbay as a test ground.
ALGORITHM DRIVE DESIGN OPTIMISATION
In order to complement physical testing onboard HRV1, Teignbridge has significantly upgraded its numerical design tool capability over the course of the last four years and now offers transient computational fluid dynamics (CFD) simulation work, finite element analysis (FEA) for structural analysis and even fully coupled fluid structure interaction (FSI) simulation. Teignbridge uses industry leading Star CCM+ software on in-house hardware, although this can be supplemented with cloud computing resource to provide additional power when required.
In inexperienced hands and with the wrong software and/or methodologies, CFD can be a dangerous black box design tool. Teignbridge has worked closely with Siemens, the developer of Star CCM+ to establish robust, validated simulation methods. This work includes development of CFD integrated, parametric geometry optimisation methodology - an artificial intelligence based routine which takes the best efforts of the human brain for a given propeller design and then automatically and incrementally explores the design space around that point to look for improvements within constraints such as cavitation and thrust provision. Each incremental design is evaluated in CFD, then used to drive the design space exploration for the next increment.
This methodology was used to provide a theoretical percentage increase of 3.9% in the hydrodynamic efficiency of a modern Handysize bulk carrier propeller by 3.9%. Physical tests on HRV1 estimate the increase at even greater than this but test data needs further work before a firm conclusion can be drawn. The optimisation process can be seen in the figure below which shows the investigation of 500 designs during the optimisation process.
Teignbridge has also developed CFD routines for hull flow simulation including enabling accurate hull resistance calculation and wakefield characterisation to ensure propeller designs can be fully wake adapted where required.
These tools and the skills of the engineers behind them ensure that Teignbridge’s propellers and underwater equipment designs are fully optimised to deliver the prime combination of performance, fuel economy and reduced emissions.
NEW CLAMP ON BLADE PRODUCT
One of the first outputs of the HEPS project is the innovative ‘Clamp on Blade’ (CoB) propeller, which was awarded a UK patent in July 2019. Teignbridge is in the process of developing further patents associated with the CoB as well as international coverage for the concept. The modular propeller has been designed for use on commercial vessels, and offers several advantages compared to existing mono-bloc and detachable blade designs.
The CoB has a smaller hub to diameter ratio than any other replaceable blade propeller on the market and, coupled with its bolt free blade palm connection system, increases hydrodynamic efficiency over competing designs. This pair of features improves efficiency by more than 2.0% over competing replaceable blade designs and can be offered with enhanced blade designs and additional performance improvements associated with the propeller optimisation discussed above.
Teignbridge expects to obtain classification society approvals for the propeller before the end of 2019.
The CoB also offers significant operational benefits compared with existing replaceable blade designs. The blades can be replaced without dry docking and the vessel operator can carry individual spares for emergency replacement taking up significantly less deck space than a spare mono-bloc propeller.
The unit can be retrofitted to any shaft (hydraulic or keyed) while its modular construction enables ease of transportation in a container. The low component weight of each part of the system increases ease of fitting. The CNC precision machined components are designed to facilitate ease of transportation, storage, installation, repair and replacement, while individual blades will also be CNC machined to ensure accuracy and balance.
The ease and speed of blade replacement also opens up the possibility of changing propeller blades for different operating conditions or expected engine loads.
The company reports that the product has already attracted commercial interest from prospective buyers, with ship owners with vessels operating in waters with significant volumes of debris accounting for a significant proportion of enquiries.
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