The Development of an Aviation Fuel Thermal Stability Test Unit

Abstract

A test unit has been developed by Rolls-Royce for the U.S. Navy to use in evaluating fuel thermal deposition typically found in various aircraft engine components. Although the current Jet Fuel Thermal Oxidation Tester (JFTOT) provides a qualitative thermal stability evaluation, it may not be able to predict in-service problems. Conditioning and testing of the fuel under realistic conditions is crucial if one is to predict deposit formations accurately. Engine fuel deposit evaluations and evidence from unpublished Rolls-Royce laboratory rig tests were used to help design a test unit that would address fuel stability problems in current or future aircraft. The Aviation Fuel Thermal Stability (AFTS) test unit embodies test modules that were selected with extensive fuel systems experience to enable the evaluation of thermal deposition in various fuel components using properly conditioned fuel. The test modules are controlled and results are recorded by a computer. This paper includes a review of the AFTS test unit design and preliminary test results thereof.

Comparison of Vibrations and Emissions of Conventional Jet Fuel with Stressed 100% SPK and Fully Formulated Synthetic Jet Fuel

“…This is done in regimes presenting accurately the thermal loading of fuel on its pathway from the fuel tank to the combustion chamber. These regimes are considered important in achieving concentrations of deposit precursors formed in service upstream of the heated section [21]. The fuel used is conditioned while the test specimens closely reflect the dynamic, thermal and material properties of actual aircraft fuel components.…”

“…The Aviation Fuel Thermal Stability test Unit (AFTSU) was developed by Daggett et al [21] following criticisms of the Jet Fuel Thermal Oxidation Tester (JFTOT) which is, the standard test method used to estimate the thermal oxidation stability of aviation turbine fuels [22,23]. The JFTOT was criticized for the following [21][22][23][24]; its design is for laminar flow and not the turbulent flow regime in aircraft propulsion systems, it is a non-quantitative approach to grade the fuels and the magnesium impurities present in Aluminum-6061 used for the heater can prevent thermal deposition.…”

Experimental Analysis on Emission Production and Performance of Stressed 100 % SPK, Stressed Fully Formulated Synthetic Jet Fuel, Jet A-1 in a Small Gas Turbine Engine

“…To study the thermal stability of jet fuels, the principle method for comparison of the thermal stability performance of jet fuel measures, or observes the build-up of carbon on pipework and fuel wetted surfaces. The Aviation Fuel Thermal Stability AFTSU, test Unit was developed by Daggett et al 19 following criticisms of Jet Fuel Thermal Oxidation Tester (JFTOT) the standard test method used to estimate the thermal oxidation stability of aviation turbine fuels [20][21] . The JFTOT have been criticized for the following 19,22 ; its design for laminar flow and not the turbulent flow regime in aircraft propulsion systems; a non-quantitative approach to grade the fuels and the migration magnesium impurities present in 6061 aluminium used for the heater which can prevent thermal deposition.…”

Investigation of surface deposition in a simulated fuel injector feed arm with sudden expansion/contraction

“…Previous works on the impact of both laminar [5,6] [7,8] and turbulent fluid flow [4,9,10] on jet fuel autoxidative deposition have been published using a simple straight cylindrical tubing of a constant diameter. However, in many current and future fuel injector deigns, the fuel passageways of the burner feed arm and the injector are far from this simple case and include geometric features such as: bends, annular regions, multiple parallel paths, features to introduce swirlers and large expansions and contractions in the flow.…”

“…The work presented here provides a novel set of experimental data corresponding to the surface deposit formation in two different designs of jet engine burner feed arms; a pipe with a sudden expansion/contraction and for comparison, a straight tube, under engine representative conditions, simulated by AFTSTU. The rig is a pilot scale experimental unit [9] capable of assessing the interaction of a simulated engine fuel system and a representative fuel. The AFTSTU simulates conditions in a range of current and future aero engines ensuring that the fuel arrives at a simplified burner feed arm in a representative condition to that in service, which is critical in assessing the likely interaction with hot surfaces and flowing fuel.…”