Browsing by Author "Ghelani, Raj"

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    Design methodology and mission assessment of parallel hybrid electric propulsion systems
    (American Society of Mechanical Engineers, 2022-09-16) Ghelani, Raj; Roumeliotis, Ioannis; Saias, Chana Anna; Mourouzidis, Christos; Pachidis, Vassilios; Norman, Justin; Bacic, Marko
    An integrated engine cycle design methodology and mission assessment for parallel hybrid electric propulsion architectures are presented in this paper. The aircraft case study considered is inspired by Fokker 100, boosted by an electric motor on the low-pressure shaft of the gas turbine. The fuel burn benefits arising from boosting the low-pressure shaft are discussed for two different baseline engine technologies. A three-point engine cycle design method is developed to redesign the engine cycle according to the degree of hybridization. The integrated cycle design and power management optimization method is employed to identify potential fuel burn benefits from hybridization for multiple mission ranges. The sensitivity of these mission results has also been analyzed for different assumptions on the electric powertrain. With 1 MW motor power and a battery pack of 2307 kg, a 3% fuel burn benefit can be obtained by retrofitting the gas turbine for 400 nm range. Optimizing the power management strategy improves this fuel burn benefit by 0.2-0.3%. Redesigning the gas turbine and optimizing the power management strategy, provides a 4.2% fuel benefit on 400 nm. The results suggest that a high hybridization by power, low hybridization by energy, and ranges below 700 nm are the only cases where the redesigned hybrid electric aircraft has benefits in fuel burn and energy consumption relative to the baseline aircraft. Finally, it is found that the percentage of fuel burn benefits from the hybrid electric configuration increases with the improvement in engine technology.
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    Integrated assessment of parallel hybrid electric aircraft propulsion architectures
    (Cranfield University, 2023-10) Ghelani, Raj; Roumeliotis, Ioannis; Pachidis, Vassilios; Mourouzidis, Christos; Bacic, Marko; Norman, Justin
    Advisory Council for Aeronautical Research in Europe (ACARE) has published ambitious goals for reduction in emissions from aircraft applications by the year 2050. Hybrid-electric and alternative fuelled powerplants have been proposed as one of the major solutions to resolve this problem. There has been significant industrial push to build and test viable hybrid-electric propulsion systems onboard aircraft and certify them for flight, with Rolls-Royce ACCEL, Airbus E-Fan X and Boeing SUGAR VOLT being some recent examples. Despite this, there exists significant uncertainty around the potential fuel burn benefits from these architectures across the different aircraft classes, the impact on gas turbine design, thermal management and aircraft integration, as well as fleet technology penetration. The work in open literature has focussed on individual aspects mentioned above but no study was found considering all these aspects in a common design and optimization loop. The aim of this thesis is to develop robust integrated design and optimization methods, to help industry examine future application scenarios in a more objective, systematic and therefore, more cost-effective manner. The regional to single aircraft design space is explored with ATR 72, Fokker 100 and A320 being the baseline aircraft platforms. Initially, a design space exploration is performed for the Fokker 100 style airframe utilizing lithium ion batteries in a parallel hybrid configuration. The impact of hybrid gas turbine cycle redesign strategies are benchmarked and compared to retrofit hybrid gas turbine. A power management optimization loop is set up to optimize the power split for varying battery pack sizes and motor powers on different mission ranges. This sweep is also performed for varying technology levels on gas turbine, motor power density and battery energy density. It is demonstrated that the benefit from electrification improves with improvement in gas turbine technology level. The integrated hybrid gas turbine cycle design and power management optimization ANN method is applied to all three aircraft platforms for EIS 2035 time frame. The optimal power management strategies favour take-off and initial climb for redesigned gas turbines while they favour cruise for retrofit gas turbines. Incorporation of direct operating cost modules show retrofit hybrid systems having a lower direct operating cost as compared to redesigned hybrid systems owing to reduced gas turbine maintenance cost. The multi-mission method is applied to the test cases showing the penalty paid in carrying a fixed battery pack. Two thermal management architectures, ram air-liquid coolant heat exchanger and vapour compression cycles are utilized to reject the heat load from the electrical systems. The design space of both the systems are first explored for varying levels on quantity of heat load, quality of heat load and flight mission conditions. The method to integrate optimal combinations of thermal management architectures in terms of, coolant mass flow rate, condenser pinch, condenser geometry and compressor pressure ratio is utilized and applied to different propulsion configurations. The full framework is also expanded to include proton exchange membrane fuel cells and hydrogen-powered gas turbines. A final technological assessment is performed for the regional ATR 72 style aircraft platform for both thermal management architectures. A pure electric, battery and fuel cell powered aircraft with an optimal power split is identified as a suitable candidate against kerosene and hydrogen powered gas turbines to power EIS 2035 regional turboprop. While for single-aisle applications, there is a case for mild hybridization to reduce NOx and improve gas turbine operability at part load settings.
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    ItemOpen Access
    Integrated hybrid engine cycle design and power management optimization
    (American Society of Mechanical Engineers, 2023-09-28) Ghelani, Raj; Roumeliotis, Ioannis; Saias, Chana Anna; Mourouzidis, Christos; Pachidis, Vassilios; Bacic, Marko; Norman, Justin
    A novel integrated gas turbine cycle design and power management optimization methodology for parallel hybrid electric propulsion architectures is presented in this paper. The gas turbine multi-point cycle design method is extended to turboprop and turbofan architectures, and several trade studies are performed initially at the cycle level. It is shown that the maximum degree of electrification is limited by the surge margin levels of the booster in the turbofan configuration. An aircraft mission-level assessment is then performed using the integrated optimization method initially for an A320 Neo style aircraft case. The results indicate that the optimal cycle redesigned hybrid electric propulsion system (HEPS) favors take-off and climb power on-takes while optimal retrofit HEPS favor cruise power on-takes. It is shown that for current battery energy density (250 Wh/Kg), there is no fuel burn benefit. Furthermore, even for optimistic energy density values (750 Wh/kg) the maximum fuel burn benefit for a 500 nm mission is 5.5% and 4% for redesigned and retrofit HEPS, respectively. The power management strategies for HEPS configurations also differ based on gas turbine technology with improvement in gas turbine technology showing greater scope for electrification. The method is then extended to ATR 72 style aircraft case, showing greater fuel burn benefits across the flight mission envelope. The power management strategies also change depending on the objective function, and optimum strategies are reported for direct operating cost or fuel burn. The retrofit case studies show a benefit in direct operating cost compared to redesigned case studies for ATR 72. Finally, a novel multimission approach is shown to highlight the overall fuel burn and direct operating cost benefit across the aircraft mission cluster.
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    ItemOpen Access
    A scalable hydrogen propulsion system for civil transport aircraft
    (ICAS, 2022-11-28) van Heerden, Albert S. J.; Sasi, Sarath; Ghelani, Raj; Sanders, Drewan S.; Roumeliotis, Ioannis
    The aim of this research was to explore the application of engineering systems evolvability analysis techniques in devising potential scalable hydrogen propulsion systems for future civil transport aircraft. Baseline and derivative aircraft concepts were generated for a medium-sized long-range aircraft, with the derivative options having different levels of hydrogen incorporated in a dual-fuel arrangement (with separate hydrogen and kerosene turbofans), as well as potential turboelectric propulsion with boundary layer ingestion. Commonality between each baseline-derivative pair was then estimated, which could be used to predict the derivative development cost savings that could potentially be obtained when working from a specific baseline. The performance and cost results enabled different future scenarios to be explored. It was shown that developing the future concepts based on an existing state-of-the aircraft as baseline can offer considerable cost savings, as opposed to designing a clean sheet version. The importance of the baseline configuration selection in reducing the development cost for the different hydrogen configurations was also highlighted.