Browsing by Author "Bosak, David"

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    Effects of more electric systems on fuel tank thermal behaviour
    (Société de l'Electricité, de l'Electronique et des Technologies de l'Information et de la Communication, 2019-12-31) van Heerden, Stevan; Judt, David M.; Lawson, Craig;; Bosak, David
    With the advent of more electric airframe systems and ultra-high bypass ratio turbofan engines, there is growing interest in the associated thermal implications. In this research project, an aircraft level model that is appropriate to enable investigations into novel thermal management solution on future aircraft is developed. In this paper, an investigation into the effects of more electric systems on the thermal behaviour of fuel tanks in civil transport aircraft is presented.Specifically, the influence of the heat generated by conventional and more electric systems on the fuel tank was modelled and simulated. A fuel thermal model was developed, which consists of a tank geometry representation, coupled to a module that calculates remaining mission fuel mass. The systems architectures are represented by connected thermal component models. Standard approaches were then employed to estimate convection and conduction heat transfer coefficients at the tank interfaces. The model solves 1-D transient heat equations, coupling heat transfer and material heat capacity via heat flux balances. The thermal and systems models were integrated into a baseline aircraft performance model, which was used to dynamically simulate the tank thermal behaviour during representative missions. The initial results indicate that switching to more electric environmental control and iceprotection systems likely have negligible thermal impact on the bulk fuel temperature. However, some benefits may be obtained regarding safety and certification, but this requires further study.
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    Exchange rate analysis for ultra high bypass ratio geared turbofan engines
    (MDPI, 2020-11-09) Nikolaidis, Theoklis; Jafari, Soheil; Bosak, David; Pilidis, Pericles
    This paper investigates the impact of thermal management methods on the design point and synthesis exchange rates of an ultra-high bypass ratio geared turbofan engine. In a typical thermal management system, where heat is managed by means of heat exchangers that transfer engine waste heat into oil, air, or fuel. However, the utilization of air–oil and fuel–oil heat exchangers has an adverse impact on engine performance. This paper investigates the impact on and engine’s specific fuel consumption and summarizes it into common exchange rates for different thermal management configurations. The results show that any pressure loss in the bypass duct results in a severe specific fuel consumption penalty (an increase of 1% pressure loss in the bypass duct causes a 2% specific fuel consumption increase at cruise conditions). In addition, quite severe is the impact of extracting air from the gas path, particularly when the bleed location is in the bypass duct or the high-pressure compressor. It is also found that the utilization of a fuel–oil heat exchanger improves the specific fuel consumption at a higher rate than an air–oil heat exchanger. For the performance characteristics of the examined engine, the specific fuel consumption benefit with the former is 1.33%, while for the latter it is 0.38%
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    Framework for integrated dynamic thermal simulation of future civil transport aircraft
    (AIAA, 2020-01-05) van Heerden, Albert S. J.; Judt, David M.; Lawson, Craig P.; Jafari, Soheil; Nikolaidis, Theoklis; Bosak, David
    The development of increasingly more electric systems and ultra high bypass ratio turbofan engines for civil transport aircraft is projected to bring forth critical challenges regarding thermal management. To address these, it is required that the thermal behavior of the complete propulsion-airframe unit is studied in an integrated manner. To this purpose, a simulation framework for performing integrated thermal and performance analyses of the engines, airframe, and airframe systems, is presented. The framework was specifically devised to test novel integrated thermal management solutions for future civil aircraft. In this paper, the discussion focuses mainly on the thermal modeling of the wing and fuel. A highly flexible approach for creating wing thermal models by means of assembling generic thermal compartments is introduced. To demonstrate some of the capabilities, a case study is provided that involves thermal analysis of a single-aisle airplane with ultra high bypass ratio engines. Results are provided for fuel temperatures across flights in standard, hot, and cold days and for different airframe materials. Engine heat sink temperatures and input power to the engine gearboxes, both important parameters needed to design thermal management systems, are also presented.
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    Physics-based thermal model for power gearboxes in geared turbofan engines
    (ASME, 2021-01-11) Jafari, Soheil; Nikolaidis, Theoklis; van Heerden, Albert S. J.; Lawson, Craig P.; Bosak, David
    Ultra-High Bypass Ratio Geared (UHBRG) turbofan technology allows a significant reduction in fuel burn, noise and emissions — key metrics for aircraft engine performance. However, one of the main challenges in this technology is the large amount of waste heat generated by the Power Gearbox (PGB). Therefore, having a practical tool for precise prediction of the PGB-generated thermal loads in UHBRGs is becoming a necessity. Such a tool would assist in analyzing engine performance, as well as ensuring that engine physical limitations/restrictions are not breached (e.g. over-temperature in fuel and oil, cocking, etc.). This paper presents a methodological approach to mathematically model the waste heat generated by a PGB on a UHBRG for different points on a typical flight profile. To do this, the total power loss in a PGB system is firstly defined as the summation of load-dependent and load-independent losses. Physics-based equations for each heat loss mechanism are introduced and, through a combination of the associated equations, a simulation model for the thermal loads calculation in PGBs is developed. In addition, the heat losses and efficiency of the PGB has been analyzed across a simulated flight. The developed PGB model calculates the main power losses generated in a gear reduction system of a turbofan engine. It is found that in a typical flight, the heat loss generated by the PGB can reach about 80% of the total waste heat generated by the engine. The values of the mechanical efficiency calculated by the tool at different flight points are above 97% which is in good agreement with publicly available data for planetary gearboxes. This tool is intended to be utilized by engine thermal management system designers to predict and analyze the heat loads generated by the PGB at different flight conditions