Overview

Aircraft combustion emissions account for about 6% of total emissions in the UK. As most aircraft fly in the earth’s stratosphere, the dispersal of combustion emissions are contributing to climate change. This dispersal in the atmosphere is expected to increase severely as the air transport is forecasted to double by 2040. Hence, novel technologies and sustainable fuels are needed to significantly reduce the environmental impact of aircraft. As first-generation biofuels are based on food crops, there is a concern that food prices could rise and shortages might occur. Second-generation biofuels, which are based on non-food crops, have potential to meet the high demands of jet fuel supply sustainably, affordably and in an eco-friendly way (Fig. 1). The project will also realise the potential of second generation biofuels as sustainable alternative fuels by enhancing their turbulent mixing with air, which will improve combustion and reduce emissions. The project will explore the possibilities of direct usage of second-generation biofuels in existing aircraft engines. The objectives are:

[1] Enhance the mixing of second-generation biofuels with air through novel flow control methods

[2] Evaluate the atomisation properties of second-generation biofuels in comparison with fossil fuels

[3] Study the interactions between mixing-enhancement methods and biofuel-atomisation processes

[4] Develop a physics-based model for designing and optimising the fuel injectors for future aircraft

[5] Estimate the dispersal of combustion pollutants in the earth’s atmosphere, mainly stratosphere

Timeliness: The findings will offer practical adaptations that could be made on existing aircraft now, thus significant impact sooner, rather than only in the next generation of aircraft. Hence, the project must be conducted now as its findings will develop greener aircraft.

Novelty: The project will investigate the true potential of second-generation biofuels as sustainable alternative fuels for aircraft engines. The project will estimate the dispersal of combustion pollutants from these biofuels in the atmosphere to determine their real benefit. For experimental research, a jet rig and engine test cells at Cranfield will be used. For computational research, a high performance computer at Cranfield will be used. The project will be performed in active collaboration with both Loughborough and Aston Universities.

Project Highlights:

  •  Apply novel flow control techniques to enhance the turbulent mixing of second-generation biofuels with air, which will improve combustion and reduce emissions
  •  Use the new knowledge that is gained from measurements to further enhance physics-based models for optimising the geometry of fuel injectors for future aircraft
  •  Explore the possibilities of direct usage of second-generation biofuels in existing aero engines for a noticeable reduction in emissions and thus making an impact sooner
  •  Estimate the dispersal of combustion pollutants (of second-generation biofuels compared to those of fossil fuels) in the earth’s atmosphere, particularly stratosphere
Fig. 1: Biofuels for Aviation: from trash to take off (Courtesy: United Airlines)

Methodology

Second-generation biofuels such as pyrolysis oils, jatropha and karanj oils will be used in this study. These biofuels will be cleaned using sock filters and then will be preheated and/or blended to reduce their viscosity to enhance the combustion process in aircraft engines. Novel flow control methods will be implemented to enhance turbulent mixing of second-generation biofuels with air, which will improve combustion and reduce emissions. State-of-the-art measurement techniques will be used to measure the jet flow turbulence characteristics and quantify the mixing performance of optimised injectors. To further our physical understanding, the atomisation process of these biofuels will be compared with that of fossil fuels. In addition, the interactions between biofuel-atomisation processes and mixing-enhancement methods will be investigated. The measured data will be used to further develop physics-based models for optimising fuel injectors. Finally, the dispersal of combustion pollutants in the earth’s stratosphere will be estimated.

Additional Information: A LabVIEW data acquisition system will be used to log temperatures at many locations of aircraft engines, which will be operated at different loads and speeds. Performance parameters such as thermal efficiency and specific fuel consumption will be calculated. Combustion characteristics will be evaluated using a Kistler combustion analyser. A pressure sensor and amplifier will be used to measure the fuel line injection pressure. Amplifiers and the encoder electronics are connected to the ‘KiBox’ for data logging. KiBoxCockpit software will also be used to measure and analyse various engine combustion parameters. The components of exhaust gases that are released from aircraft engines will be measured using an emission analyser.

Training and Skills

The project is a great opportunity for students to gain expertise in experimental (LDA; PIV; HWA) and computational (RANS; URANS; LES) methods in fluid mechanics. Collaborations include placements, which will enable students to have a wider experience. Students will have opportunities to attend relevant workshops (Measurement Techniques in Fluid Mechanics; Computational Fluid Dynamics; programming languages; transferable skills) and present their research at international conferences (Biofuels Congress; UK Fluids Conference; European Fluid Mechanics Conference) and publish their findings in leading journals (Fuel; Energy & Fuels; Physics of Fluids). The project will enable students to advance their skillset and enhance their employability.

Timeline

0-6 months: Perform literature review and attend relevant trainings and workshops

4-10 months: Experimental rig design and set up and perform preliminary measurements

8-14 months: Evaluate the performance, emission and combustion characteristics of biofuels

12-18 months: Compare active and passive flow control methods for enhanced turbulent mixing

16-22 months: Determine the atomisation properties of biofuels in comparison with fossil fuels

20-26 months: Compare the mixing enhancement potential of pulsated jets to that of steady jets

24-30 months: Interactions between mixing enhancement methods and fuel atomisation processes

26-34 months: Modelling of the biofuel-air mixture dynamics and biofuel combustion processes

30-34 months: Estimate the dispersal of combustion pollutants in the earth’s stratosphere

32-36 months: Consolidate the research findings and write up the PhD thesis and publications

Partners and collaboration (including CASE)

The project will be primarily performed at Cranfield University. The project will include an internal collaboration with the Met/NERC Facility for Airborne Atmospheric Measurements and Aerospace Integration Research Centre at Cranfield University. The computational research will be performed in collaboration with Loughborough University (which is home to the Rolls-Royce University Technology Centre in Combustion System Aerothermal Processes) as part of the CENTA2 DTP programme. The experimental research will be performed in collaboration with Aston University (which is home to the European Bioenergy Research Institute) through a strategic partnership.

Further Details

Research Facilities:

https://www.faam.ac.uk/index.php

https://www.cranfield.ac.uk/centres/aerospace-integration-research-centre

http://www.lboro.ac.uk/research/rolls-royce-utc/

http://www.aston.ac.uk/eas/research/groups/ebri/

The student will be based at the Cranfield University CDS campus at Shrivenham in Wiltshire - https://www.cranfield.ac.uk/About/How-to-find-Cranfield/How-to-find-Shrivenham