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Ultra Low emission Technology Innovations for Mid-century Aircraft Turbine Engines

Periodic Reporting for period 2 - ULTIMATE (Ultra Low emission Technology Innovations for Mid-century Aircraft Turbine Engines)

Reporting period: 2017-03-01 to 2018-08-31

The ULTIMATE project investigated gas turbine aero-engine concepts for year-2050 targeting the reductions in CO2 and NOx emissions set forth by the EC in Flightpath 2050, Europe’s Vision for Aviation. The proposed concepts rely on conventional gas turbine technology and to synergistically explore the combination of radical technologies to minimize the major losses occurring in state-of-the-art gas turbine engines. The studied architectures included:

• Geared turbofan (GTF) with intercooled (IC) core and pulsed detonation combustion (PDC)
• Geared counter rotating open-rotor (CROR) with a Boxprop front propeller and IC gas generator with PDC
• CROR with nutating disc core modules driving the intermediate-pressure compressor
• GTF with a supercritical-CO2 bottoming cycle
• GTF with IC, secondary combustion, nutating disc topping cycle modules and air bottoming cycle
• GTF with IC core and piston topping cycle (CCE)
• GTF with IC and secondary fluid recuperation core

The propulsive efficiency was maximized by incorporating open-rotor technology and geared fans. A mix of selected novel integration and low-noise technologies was also investigated:
• Slotted inlet nacelle for GTF application
• Variable pitch fan for GTF
• Retractable nacelle concept for CROR noise shielding
• Novel Boxprop high-speed propeller for CROR applications

The engine studies at TRL2 revealed that the ULTIMATE engines are capable of delivering a 3% to 17% reduction in fuel-burn, relative to the year-2050 state-of-the-art reference engines. If compared to the year 2000 reference engines, a 47% to 62% fuel burn reduction is to be expected. The project have successfully demonstrated that significant improvements in performance are to be expected if the major losses, which are not in reach with conventional technology, are minimized. The most substantial impact on fuel burn occurred when combining constant volume combustion and intercooling technologies. Regarding NOx emissions, the concepts provided a reduction between 10% - 35% in LTO cycle NOx, relative to year-2050 combustor technology, which in some cases translates into a reduction superior to 90% relative to the year 2000 reference combustor. The noise estimation revealed that for some configurations a reduction of 15 dB in cumulative noise, relative to year-2000 is within reach.
The ULTIMATE project started by predicting the gas turbine technology levels at year 2050. Reference engine architectures for 2050 (not including ULTIMATE technology) were developed to support the integration studies and to allow the quantification of the benefits arising from the radical core technology. The reference engines for 2050 included an ultra-high bypass ratio GTF, for long range applications, and a CROR for intra-European operation. The aforementioned engines were developed to meet the specifications of the advanced tube and wing aircraft models, also developed in the project for the year 2050 time-frame. The main tasks during the first 18 months, revolved around the development of performance models for the different core technologies including: intercooling, recuperation, inter-turbine combustion, constant volume combustion and bottoming cycles. The project also investigated low-pressure and integration technology, aiming to comply with the anticipated noise regulations and to provide the necessary variability to enable ultra-low specific thrust and associated improvements in propulsive efficiency. The preferred configurations, which include the best combinations of the aforementioned technologies, were down-selected and ranked against fuel burn improvements relative to the reference 2050 engine architectures. This was supported by qualitative assessments on noise and NOx emissions. To support the engine assessment, a multi-disciplinary evaluation platform for the 2050 time-frame was developed including engine performance; engine conceptual design and weight; noise and gas emissions; aircraft performance and operation cost.

The conceptual designs were matured to TRL2 in the second half of the project. Different selected enabling technologies were also refined using CFD and chemistry modeling. During the technology maturation process, the engines were optimized to minimize fuel-burn and NOx emissions. The impact of the new engine core technology on emissions was quantified for ICAO certification, LTO cycles and in-flight operation. In parallel, the selected low-pressure and integration technologies were also further developed and refined. Computational aeroacoustics (CAA) simulations were performed to investigate the noise generation mechanism of conventional open-rotor technology. The CAA computations allowed for the creation of an open-rotor noise benchmark, against which the novel Boxprop propeller noise reduction potential could be compared. The entire process was supported with technical advice provided by each close industry partner.

Several actions were undertaken in industry and academia to promote technologies identified in the project and to establish long-term development partnerships. Interactive work seminar were carried out at the partnering industries to promote technologies maturation and to facilitate that project results end up in technology development of aero engine companies. In addition the project participated at the Farnborough International Airshow 2018. Five 3D printed mock-ups of aircraft-engine and technology concepts have been displayed at the ULTIMATE stand, together with technical datasheets, A0 Posters, and project flyers. The event provided the opportunity to meet and discuss with different specialists in the aeronautic sector and to promote the technologies to a broader audience. The event also rendered several publications in popular science magazines promoting results from the project.
ULTIMATE brought together five experienced research groups and four major European engine manufactures to foster the development of systems that contribute beyond the limits of conventional technology, therefore enhancing European aviation industry competitiveness at long term. These systems rely on the incorporation of radical concepts into proven technology aiming to bring step like improvements in the thermal and propulsive efficiencies of state of the art gas turbine aero-engines. Reductions on CO2, NOx, and noise emissions were investigated and demonstrated at TRL2 and their contribution on future global emissions, was quantified for different scenarios. ULTIMATE have successfully demonstrated that a two digit improvement in fuel-burn, relative to year-2050 more conventional gas turbine engines, is within reach with the inclusion of constant volume combustion technologies. Such improvement is not possible if the present gas turbine development strategy is kept. Historically entry into service engines are at least 10% more efficient than previous best in class. With the anticipated increase in fuel price, it is expected that the same level of improvement is required by the airliners when acquiring new engines in the future. Hence ULTIMATE results, if implemented, pave the way for another aircraft generation driven largely by propulsion technology improvements.

The core work performed across all work packages allowed for the development of original scientific work, 5 new PhDs to be finalized, and more than 30 scientific publications to be submitted in journals and conferences.