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Rotron Awarded NATEP Grant to Develop High Endurance Heavy Fuel Engine

Rotron Awarded NATEP Grant to Develop High Endurance Heavy Fuel Engine


October 07 2015

Rotron Power Ltd has been honoured with a prestigious grant from the National Aerospace Technology Exploitation Programme (NATEP) to develop a high endurance heavy fuel rotary engine for Unmanned Aerial Vehicle (UAV) applications.

Since NATO’s announcement of the single fuel policy in 1997, the military has made an extraordinary effort to convert all of its gas-powered equipment to operate on one fuel. It’s an initiative termed as “One Fuel Forward”. There are a few different types of fuels that fall in the category of “Heavy Fuel”, and were developed to provide additional safety margins over gasoline and can sit in storage containers for longer periods without degrading. Jet A1 and JP8 are the primary fuels used for this initiative, along with JP5 which has been developed for use in shipboard service. These high density fuels have a higher volumetric energy content that maximises the energy that can be stored in a fixed volume and thus provides the longest flight range. However, more suited to compression ignition engines, the use of heavy fuel within a rotary engine represents a number of substantial engineering challenges.

Heavy fuel’s higher density is due to its composition; a complex mixture of hydrocarbons containing alkanes, naphthenes and aromatic hydrocarbons. This chemistry causes an increase in small carbonaceous particles (coke) to be formed during the combustion process. These particles continue to burn as they pass through the flame and can become incandescent under the high temperature and pressure conditions of the combustion section. This causes an augmentation to the normal heat footprint received by heat transfer from the combustion gases. These high housing wall temperatures or hot spots can lead to cracks and premature engine failures.

Within the spark-ignition combustion cycle, unburned heavy fuel has a tendency to ignite spontaneously (autoignites) and burns very rapidly. This undesirable combustion phenomena results in precipitous pressure rises which can result in the uncontrolled release of significant quantities of the fuel’s energy; energy which may be transferred harmfully to engine components. To aid control of the pre-ignition the compression ratio is reduced but this allows for less of the carbonaceous particles to be consumed during combustion. The remaining carbonaceous particles can become harmful to the engine through impingement of critical components, erosion and carbon deposits that can disrupt the flow pattern of the combustion cycle and increase engine temperatures.

Heavy fuel is largely a kerosene-based fuel and has a much higher flashpoint than gasoline-based fuel. The flashpoint is used to estimate at what temperature the vaporised liquid has reach its flammability limit. The flashpoint of gasoline is about minus 43 degrees Celsius. JP8 and JP5 share common composition characteristics, with the principal difference being their flashpoint minimum limit. JP8 has a 38 degrees Celsius minimum limit and JP5 a 60 degrees Celsius minimum limit. Therefore due to the low compression ratios being used, the fuel air mixture needs to be heated above that temperature to ignite.

Over the 18-month research and development project Rotron will carry out quantitative fuel analysis and combustion tests to further understand the limitations and ignition characteristics of heavy fuel. The output data will then be used for the implementation of a remodelled pre-heat and multipoint injection system to achieve more effective and consistent engine starting. ECU hardware and software development will be carried out in partnership with General Engine Management Systems Ltd. (GEMS).

Further research into coke characterisation and morphology will aim to determine new strategies to achieve more efficient combustion and particle burn. Analysis of materials and manufacturing processes will provide strategies for the implementation of preventative actions for autoignition, surface ignition and coke deposit and build up.

Jim Edmondson, CEO Rotron Power, said “While development of a heavy fuel engine represents a substantial engineering challenge, the research supported by this NATEP Grant will confirm the feasibility to further develop our existing HFE architecture to produce a high endurance engine capable of 150 hours before overhaul. Working with GEMS, we aim to develop an improved ignition system which will allow a more consistent start procedure, combined with improvement in the design and manufacture of critical components. The engine will have some unique advantages and presents a significant opportunity for Rotron to become the leading supplier of heavy fuel engines for small and medium UAVs.”

Kevin Baker, the sponsoring NATEP Technology Manager, added “Companies such as Rotron already have some impressive technology. NATEP is pleased to be able to help them take this on to the next stage, so that they stay at the forefront of the technology. The heavy fuel UAV market will grow in the future and we want to help British companies to have the biggest share of this.”

The National Aerospace Technology Programme (NATEP) is aimed at aerospace supply chain companies including SMEs to help them develop innovative technologies while enhancing their technology management capabilities, increasing their ability to win new business with higher tier companies anywhere in the world. NATEP is a £40m three-year programme funded by the Advanced Manufacturing Supply Chain Initiative (AMSCI) – its objective is to deliver 100 novel technologies through collaborative projects within the UK aerospace supply chain. NATEP is managed by ADS, actively supported by the regional aerospace alliances and sponsored by the UK aerospace Primes and Tier 1s.

About WEAF
The West of England Aerospace Forum (WEAF) is a membership trade association that champions and supports the interests of the aerospace and defence industry in the South West of England. The forum leads the sector in delivering national supply chain initiatives, including NATEP, which connect the SME community to the Primes.

AMSCI supports manufacturing supply chains in England to reshore in the UK and improve global competitiveness by encouraging innovative, collaborative projects which established strong, sustainable and balanced growth. Complementing the Regional Growth Fund, AMSCI offers flexible funding support for R&D, skills, training, capital finance and leveraging private sector investment.