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Efficient Systems and Propulsion for Small Aircraft

Periodic Report Summary 2 - ESPOSA (Efficient Systems and Propulsion for Small Aircraft)

Project Context and Objectives:
The ESPOSA project will develop and integrate novel design and manufacture technologies for a range of small gas turbine engines up to approx. 1000 kW to provide aircraft manufacturers with better choice of modern propulsion units. It will also deal with engine related systems which contribute to the overall propulsion unit efficiency, safety and pilot workload reduction. Through the newly developed design tools and methodologies for the engine/airframe integration the project will also contribute to the improved readiness for new turbine engines installation into aircraft.

New technologies and knowledge gained through the ESPOSA project will provide European general aviation industry with substantially improved ability to develop and use affordable and environmentally acceptable propulsion units and reliable aircraft systems minimizing operating costs, while increasing the level of safety. The new engine systems and engine technologies gained from ESPOSA should deliver 10-14% reduction in direct operating costs (DOC) and reduce significantly the pilot workload. The ESPOSA project is oriented on turbine engine technologies tailored for a small aircraft up to 19 seats (under CS-23/FAR23 regulations) operated on the scheduled and non-scheduled flights.

Research work comprises performance improvements of key engine components, their improved manufacture in terms of costs and quality. New engine component technologies will be backed by novel modern electronic engine control based on COTS, pioneering the engine health monitoring for small engines and providing advanced more electric solutions for fuel and propeller control systems. The project also addresses problematic design areas connected with turboprop/turboshaft engine installation into airframe structure, including the use of composite materials. The work will be conducted taking into account specifics of different aircraft configurations.

Project activities will include extensive validation on the test rigs. The most appropriate technologies according to value/cost benefit will be selected and integrated into functional complexes and further evaluated on the engine test beds. The functionality of certain project outcomes will also be demonstrated and validated in flight conditions to reach higher proves level.

The ESPOSA project will also employ those technologies already developed for larger aircraft or those outside of aeronautics to provide affordable technology solutions for small aircraft. The project encourages both aircraft and engine producers in using new technologies for gas turbine engines, in demonstrating their feasibility and in proving their advantages for operators.

The content of RTD work of ESPOSA is complementary to the activities and technology domains addressed by the JTI Clean Sky. The ESPOSA project will fully employ results gained in propulsion area from the integrated project CESAR (Cost-Effective Small AiRcraft - AIP5-CT-2006-030888) and several other FP projects.
Project Results:
Brief summary of achievements of the first project year follows.

Part of the work in the second project year in SP1 was the prediction of technological and economic challenges and analysis of possible trends in the airworthiness. The activities in general requirements and constraints on the new future propulsion unit for small aircraft are in process and were finished during the Common Vision meeting in December 2013. The enhanced tools and modelling capabilities to perform effective trade-off studies for new propulsion systems were prepared. Final evaluation results for BE1 will be validated according to the results from the testing in SP5 and SP7 during next periods.

Concerning the new engine components design, optimizations and thermal calculations of high pressure compressors were performed. Part of the work is compressor outlet system optimization. Unsteady calculations confirmed improvement of performances of compressor with new outlet system designed by using of “steady-state” solver. Work related to gaps measurement system and tip clearance monitoring proceeded according to plans.

For advanced cooled small turbine unsteady interactions in small cooled high pressure turbine were investigated in order to better understand the physical processes within the turbine and improve the accuracy of aerodynamic and heat loads predictions. Determination of the baseline turbine geometry as well as specifications and constraints for optimization were performed. Complex computational optimization and related experimental work for new high and low pressure turbines have been carried out. Investigation and design of a high efficiency inter-turbine duct were also part of work. Primary design and numerical simulation on the efficient combustion concept based on unconventional JETIS and more conventional RQL were accomplished including testing rig preparation. Manufacturing work of testing components and some experimental combustion testing has been commenced in the second project year. As for a new gearbox concept complex guideline were elaborated and gearbox dynamic loads and inputs were calculated. Work in component area is supported by advanced dynamic modelling of high speed turbomachinery, where parameterized solid model of the GTE’s blade profile and analysis of dynamic models for components of a GTE rotor system (rotors, disks, bearings, seals, and dampers) were carried out. Dynamic characteristics of BE1 and BE2 and recommendations for improvement are now available. The preparatory work has been started for engine and system validation and integration.
New lean manufacture technologies concentrated on the definition of processes low cost machining of compressor wheels and diffuser using titanium machining tools.

Optimization of reference process for BE1 impeller, which was defined in the first year of the project, using elaborated knowledge of the first year was performed. It meant the implementation of different analogy tests (high pressure cooling, benchmark of different cutting tools, plunge milling investigation and other tests) for turning and milling process of titanium material Ti6Al4V, as preparatory work for process design of radial compressor. Implementation of different analogy tests (Experimental studies of tool coating impact for different work piece material); Machining tests on compressor geometry using new tool-path programming software; Elaboration of mathematical supported software for designing cutting tools with optimal geometries according to the present work piece geometry.

The definition of blisk (turbine wheels) geometry for precise and low-cost casting using new superalloys was elaborated. During last year we have accomplished a number of the efforts that helped establish a quality stability of the nicked – based super alloys of in-house production, collect statistical data per the produced melts. The possibility of recycling the expensive alloys made possible by the refining re-melting techniques gave a very high cost – effectiveness benefits in the manufacture of aero engine parts. Work covered also application of the high-gradient directional solidification technique for the turbine blade production and optimization of the process parameters of the hot isostatic pressing of critical part castings from the nickel base heat resistant alloys for the production of high quality parts by using the HIP press Quintus QIH 0.9x1.5-2.

In this respect study and definition of thermal barrier coatings (TBCs) and its adaptation for turbine vanes and combustion chamber were performed. It concerned the development of nanostructured ceramic powders and advanced coating solutions for TBC applications. Thermo-mechanical testing of candidate base materials and manufacture of coated test specimens for the combustor (lab scale testing). Development of coating solutions and manufacture of test specimens (lab scale testing) completed for: bearing mounting areas on engine shaft (tearing resistant coating), compressor blade roots (anti-fretting coating), GTE turbines (rubbed sealing coating) and nozzle guide vanes (TBC). Set-up and validation of thermo-shock test rigs for the characterization of new TBCs under reference conditions.

Deposition process parameters developed for bearing seats, nozzle guide vanes and anti-fretting wear coatings for compressor blade root. For low-cost gearbox manufacturing test article geometry was defined and a benchmark on materials for induction hardening and superfinishing techniques concluded. Test procedure defined for single tooth bending, pitting and scuffing. Design of test articles (Z56 and Z20 gears) and CIH simulation completed; manufacturing drawings released. Test samples manufacturing in process. Test plans for Single Tooth Bending Fatigue, Pitting and Scuffing defined. New FZG test rig design for Z20 test article geometry completed. Hardware and installations (test cell) review for endurance test ongoing. Definition of a mathematic model for spur gear cutting concluded. Determination of tools for turning/milling operations for Curvic couplings with a focus on a real geometry completed.
Area of systems addresses advanced automatic control system for small engines, smart health monitoring system and affordable more electric solution for fuel/ propeller control systems. The major work of the period concentrated on analyses and adoption of technical requirements defined by airframers and engine producers. Work on advanced automatic control system for small engines concentrated on Preliminary design review (PDR), reliability analysis and engine control modelling and simulation.

The performed activities comprised feasibility study of applied technologies, development methodologies and system architecture concepts. Activities on equipment preliminary concept designs started. Activities on smart health monitoring system were oriented on the accomplishment of PDR, hardware and software design and simulations.
Work on affordable more electric solution for fuel and propeller control was oriented mainly on building the demonstrators of low cost fuel metering device and control electronics and electrically driven fuel pump.

Advanced design methods for engine/airframe integration are aiming at development of the best practice for turbine engine installation to different types of aircrafts (tractor, pusher, helicopter). SP6 addresses structural design aspects, aeroacoustic optimization, and thermal management of nacelles structures. The work of the second period comprised mainly PDR for different aircraft configurations, computer and wind tunnel aeroacustic investigations, thermal and heat management models. For composite nacelles design and technology tuning work was performed.

Preparatory work in work packages related to the engine ground tests and qualifications of the engine for flight has started. The work covers preparation of ground test rigs and preparation of tests in the altitude chamber.

Potential Impact:
Perspective technologies developed within ESPOSA will be exploited industrially. Engine producers and component manufacturers will get technologies and knowledge for their new products (family of new gas turbine engines for small aircraft). The project delivers new design concepts of engine components (optimized parts of flow path – compressors, turbines, ducts / cooled vanes / clearance management systems, new systems like innovative EECU, engine health monitoring, COTS parts usage, novel more electric solution for fuel and propeller control systems. As for manufacturing technologies for engines parts production ESPOSA aims at delivering new technologies for cutting, casting, TBCs, induction hardening of gear wheels, gear finishing processes and at new material application.

Aircraft manufacturers will benefit from comprehensive design knowledge and methodologies (best practices) for turbine engine installation and for nacelle design made of composites and from availability of new turboprop/turboshaft propulsion for aircraft and rotorcraft application.

Impact of ESPOSA can be divided into technical, industrial and societal. These three areas are timely dependent as the research and technology results from ESPOSA must firstly be implemented to new products which show added value for aircraft operators and consequently to the society as a whole.

The consortium has grown on business roots with significant industrial background. There is quite a realistic ambition to open completely new market segment of small turbine engines and to ripple standing waters of 400-500 kW turboprop market. ESPOSA will bring a possibility of establishing new supply chains between traditional western EU countries and eastern European countries such as new member states and even non-EU countries. The European aviation industry can use ESPOSA for establishing cooperation with the huge eastern European markets, namely in Ukraine and Russia.

Some of the ESPOSA results may also be applied outside the aeronautic sector, especially for rapidly growing market of ground gas power plant stations. The engine class addressed by the ESPOSA and component technologies have very good premises to be possible to convert on ground power unit (GPU) used broadly in other industrial applications.

ESPOSA can significantly contribute to more efficient air transport operated by small aircraft through the reduction of operating costs (DOC). The project can deliver combination of higher profitability for small aircraft operators and/or more affordable and accessible small aircraft transport (including aero-taxi). The small aircraft transport forms only minor part of the overall aviation business, however, for countries or areas with low road density and long distances between towns or in rural areas the small aircraft transport can be sometimes the best transport option. Some of these aircraft are also employed as business aircraft and for cargo delivery incl. postal services.

Safety increase in General Aviation is one of the major challenges for further development of this sector, which is known by high rate of aircraft accidents. In general, the pilot errors cause about half of all aircraft accidents. In case of General Aviation the rate will be even higher. ESPOSA´s technologies for modern electronic engine control systems will reduce the pilot workload and diminish the probability of pilot’s failure.

The general and business aviation industry is a large source of employment, expertise, technology and revenues. ESPOSA will contribute to the European employment policy in the industrial sector with high added value and high technology level.

Jet fuel and other fuels used in aviation belong to the scarce natural resources. ESPOSA technologies contribute to rational use of limited fossil fuels by the lower fuel consumption of aircraft engines and overall efficiency of air transport system.
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