Ice accretion and release in fuel systems

Abstract

Following the B777 accident at Heathrow in 2008, the certification authorities required Boeing, Airbus, and Rolls-Royce to conduct icing analysis and tests of their Rolls-Royce Trent engined aircraft fuel systems. The experience and the test data gained from these activities were distilled and released by Airbus to the EASA ICAR project for research and analysis. This paper provided an overview of the Airbus ice accretion and release tests. Brief narratives on the test rigs, the test procedure and methodology were given and key findings from the ice release investigations were presented. The accreted ice thickness was non-uniform; however, it is found typically c. $\mathrm{2\;\mathrm{m}\mathrm{m}}$thick. Analysis of the accreted ice collected from the rig tests showed the ice was very porous. The porosity is very much dependant on how the water was introduced and mixed in the icing test rigs. ThestandardAirbus method produced accreted ice of higher porosity compared to that produced by theinjectionmethod. The porosity of the accreted ice from Airbus icing investigations was found to be c. 0.90. The relationship of permeability with porosity was inferred from published data and models for freshly fallen snow in the atmosphere. Derived permeability$\mathrm{7.0\times 10^{-9}\;\mathrm{\mathrm{\mathrm{m}}^{\mathrm{2}}}}$was then applied in the CFD analysis of pipe flow with a porous wall lining to determine the shear stress on the accreted ice. It showed that 25%, 50% and 75% of the accreted ice has interface shear strength of less than$\mathrm{15.3\;\mathrm{Pa}}$,$\mathrm{20.7\;\mathrm{Pa}}$and$\mathrm{26.1\;\mathrm{Pa}}$, respectively.

The impact of sustainable aviation fuels on aircraft fuel line ice formation and pump performance

“…The standard Airbus water introduction method is described by Ref. (17) and was adopted with slight modifications for this project. This method requires thorough mixing of calculated volumes of water and fuel at room temperature using an ultrasonic bath, and eventually introducing it into the system before cooling begins; at this stage, the bulk fuel temperature was set to 28 • C. No water was added after cooling commenced.…”

“…Water solubility, water settling and ice formation, amongst others, are some such properties of interest [10,11]. The behaviour of water and ice in AFS has been studied from different perspectives [3,[12][13][14][15][16][17][18]. This has resulted in a large number of systems being employed for preventing the build-up of ice in AFS [19][20][21].…”

“…Most OEMs protect their fuel feed pumps with mesh strainers, and pressure relief bypasses on the fine fuel system filters and fuel oil heat exchangers (FOHE). The latter ensures uninterrupted fuel flow to the engine in the event of ice build-up and filter or FOHE blockage [17]. Ice formation will occur when an aircraft is at altitude for a prolonged period.…”

Complexities associated with nucleation of water and ice from jet fuel in aircraft fuel systems: A critical review

“…Maloney et al explained that stainless steel accumulated more ice than roughened aluminium and Teflon, as seen in figure 10 [12]. Similarly, a recent study by Airbus on the ice accretion/release test in a large scale flowing fuel system indicated the non-uniformity of ice thickness and porosity and suggested that it is a result of water injection/mixing method [146]. Therefore, it can be concluded that the variation in reported data throughout the literature can be attributed to different testing conditions and experimental techniques.…”

Review for State-of-the-Art Health Monitoring Technologies on Airframe Fuel Pumps

“…The microbial fungus appears as sludge that restricts flow at not only the fuel pump filters, but other components in the fuel system, such as valves and pipelines. More information on blockages caused by ice for aircraft can be found in the work by Lam & Woods (2018) and by Lawson, Baena & Lam (2012). More information on blockages caused by microbial growth can be found on the book by Langton et al (2009).…”