Fuel-cooled thermal management, including endothermic cracking and reforming of hydrocarbon fuels, is an enabling technology for advanced aero engines and offers potential for cycle improvements and pollutant emissions control in gas turbine engine applications. The successful implementation of this technology is, however, predicated on the use of conventional multicomponent hydrocarbon fuels and an understanding of the combustion characteristics of the reformed fuel mixture. The objective of this research is to develop and demonstrate the technologies necessary for utilizing conventional multicomponent hydrocarbon fuels for fuel-cooled thermal management, including the development of the endothermic potential of JP-7 and JP-8 +100, a demonstration of the combustion of supercritical/endothermic fuel mixtures, and conceptual design of a fuel-air heat exchanger. The ability to achieve high heat sinks with existing jet fuels (e.g., JP-7 and JP-8 +100) was demonstrated with a bench-scale test rig operating under flow conditions and passage geometries simulative of practical heat exchangers for aircraft and missile applications. Key measurements included fuel heat sink, reaction products, and extent of conversion: Full-scale sector rig tests were conducted to characterize the combustion and emissions of supercritical jet fuel, and demonstrate the safety and operability of the fuel system, including a fuel-air heat exchanger.

Fuel-Cooled Thermal Management for Advanced Aeroengines

Trends in increasing aircraft speeds and engine efficiencies are increasing vehicle and engine heat loads. Especially at higher Mach numbers, fuel is an attractive heat sink. For many vehicle applications, utilization of this heat sink would increase fuel temperatures beyond critical values, typically 370–400°C (700–750°F). As temperatures increase beyond about 480°C (900°F), this heat addition can lead to thermal/catalytic cracking of the fuel, leading to an “endothermic” fuel. The principal barrier to the use of high temperature fuels is the deposition of carbonaceous material on heat exchanger passages, filters, fuel injectors, and other fuel system components. This paper will review progress in understanding and mitigating the thermal instability/deposition problem.

Cracking and deposition behavior of supercritical hydrocarbon aviation fuels

The first provisional jet fuel specifications were published in 1943 in England (RDE/F/ KER/210) and 1944 in the U.S. (AN-F-32a). Jet fuel has undergone many changes in subsequent years, with current specifications for JP-5 and JP-8 for the military in the U.S. and Jet A/Jet A-1 for commercial use worldwide. Jet fuel specifications are subject to constant tension between performance requirements and availability/cost considerations. In this paper we will discuss how jet fuels have evolved over the years from the first engines to current gas turbine engines. Jet fuels derived from nonpetroleum sources will also be discussed.

Advancements in Gas Turbine Fuels From 1943 to 2005

Large investments have already been made in Europe and the US through R&T programmes and collaborations to reduce the negative environmental effects of aircraft use. Research is therefore providing the technologies to improve the performance of existing engine components.

New Environmental Friendly Aero Engine Core Concepts

The isobaric specific heat capacity of kerosene RP-3 was experimentally measured using a vacuum flow-calorimeter in the near-critical and supercritical regions. During the experiments, the qualitative temperature changed from (292.1 to 823.9) K, and the operation pressure changed from (2.40 to 5.98) MPa. The operation pressure, fuel inlet and outlet bulk temperatures, mass flow rate, and heat power were measured using a pressure gauge transducer, K-type sheathed thermocouples, a Coriolis-force flow meter, and current and voltage meters, respectively. The estimated uncertainty of the measurement was lower than 2.11 %. The expanded accuracy of the measured method for the low temperature region was verified by the water at the pressure of 3.01 MPa; the high-temperature region was verified by comparing the temperatures calculated from Cp integrating enthalpy with the temperatures measured in the experiments.

Isobaric Specific Heat Capacity Measurement for Kerosene RP-3 in the Near-Critical and Supercritical Regions

This paper evaluates the feasibility and potential impact on overall engine performance when utilizing the heat sink sources available in a gas turbine engine for improved turbine thermal management. A study was conducted to assess the application of a heat exchanger to cool the compressor bleed air normally used air for cooling turbine machinery. The design tradeoffs of this cooled cooling air approach as we’ll as the methodology used to make the performance assessment will be addressed.The results of this study show that the use of a cooled cooling air (CCA) system can make a positive impact on overall engine performance. Minimizing the complexity and weight of the CCA system, while utilizing advanced, high temperature materials currently under development provide the best overall solution in terms of design risk and engine performance.Copyright © 1999 by ASME

Greg B. Bruening

Papers

Cooled Cooling Air Systems for Turbine Thermal Management