The FINCAP project has developed a series of experimental data sets, and modelling capabilities to assess the formation of fuel break down deposits in fuel injectors with application specifically to lean burn fuel injectors required for the UHBR engine.
The lowest scale assessments of fuel performance were made in static reactors and permitted the generation of validation data for the expansion of the available chemical kinetic models for fuel autoxidation in FINCAP WP3 and WP5. The FINCAP project developed improvements to the available models in the literature, covering a wider range of application temperatures and chemistries, specifically: improvement to the Basic Autoxidation Mechanism (BAS) through the addition of hydroperoxide reactions, sulphur speciation and the impact of metal contamination on the fuel behaviour. This model development has been continued in a follow on UK funded programme, PINES, and is increasing the level of reaction steps to include the agglomeration phase of deposit formation. A PhD studentship has been externally funded in relation to this work also. This work has been published in two journal papers and presented at the CRC aviation fuels meetings in Washington, US. The strategy adopted within FINCAP is to generate the best available chemical kinetic model at key milestone points in the project.
Laboratory investigations into the impact of fuel chemistry and surface roughness on deposition have taken place in FINCAP WP2 using available small scale facilities at the University of Sheffield. The analysis of fuel chemistry has included the impact of 100%SAF on thermal stability behaviour of fuels, along with a number of blending studies to provide important guidance of the relative improvement in performance by changing the fuel chemistry. The HiReTS rig was used to develop a dataset investigating the impact of surface roughness at a small scale. Experimental data on the deposit formation from TRL5, AFTSTU rig studies were used as validation data for the kinetic model developed when used with CFD codes developed in WP4.
This work was expanded to include additive layer manufactured (ALM) sub sections of the full lean burn injector geometry which were tested on a TRL5 level rig in conjunction with the topic manager. These studies involved working closely with the topic manager, and the ALM manufacturing specialists within the organisation.
The WP4 work involved the upgrading of the Topic Manager in-house CFD code, PRECISE to include mesh morphing, conjugate heat transfer and multi step chemistry reactions to allow the developed kinetic model for deposition to be coupled with the CFD solutions for flow and thermal fields in the injector design. A post processing tool to predict deposit growth rates has been developed and was compared against the results from WP2 at TRL5 scale.
Finally, WP6 designed and built a new rig facility and has generation of experimental results studying the effect of ingress into the tertiary cavity of the fuel injector.
The conclusion of this work provides evidence to support a root cause for the ingress into the tertiary cavity and a new test capability, flexible enough to handle a range of injector designs.
