Corso di Motori Aeronautici Mauro Valorani Laurea Magistrale in Ingegneria Aeronautica (MAER) Sapienza, Università di Roma Anno Accademico 2011-12
Sett. 13: Conclusioni 1 FP7 Aero Engine Scenario ERS Strategy Targets CO 2 &NO X Reduction VITAL Concepts COUNTER-ROTATING FAN DIRECT DRIVE TURBOFAN GEARED TURBOFAN SP 1: Whole Engine Integration SP 2: Intecooled Recuperative Core Concept SP 3: Intecooled Core Concept SP 4: Active Core Concept SP 5: Flow Controlled Core Concept SP 6: Innovative Combustor
Lez. 26: Conclusioni
FP7 Aero Engine Scenario
ERS Strategy ERS Strategy FP-5: EEFAE (Efficient and Environmentally Friendly Aero Engine) and SILENCER (Significantly Lower Community Exposure to Aircraft Noise) were in preparation towards the ACARE targets on engine level. The CLEAN (Component Validator for Environmentally-friendly Aero-Engine) demonstrator aimed at the validation of components for the future concepts. FP-6: two integrated projects have been set-up: VITAL focused on technologies for low pressure system improvements to reduce CO 2 and noise. New combustor technologies and new engine core configurations will be developed to find a significant and durable reduction of pollution within the NEWAC (NEW Aero engine Core concepts) programme
Targets CO 2 &NO X Reduction Targets CO 2 &NO X Reduction
VITAL Concepts VITAL Concepts Technologies developed in VITAL will be incorporated in three basic configurations involving the low-pressure section including the fan. The improvements expected from each of these layouts will be evaluated against the requirements of the type of flight (short or long-haul). Three basic architectures are investigated: Direct Drive Turbofan (DDTF), a re-optimized tradeoff between fan and turbine requirements considering the low weight technologies introduced in VITAL. Geared Turbofan (GTF), combining a fan with a reduction gear train, to allow different rotating speeds for the fan, and the booster and turbine. Contra Rotating Turbofan (CRTF), with two fans turning in opposite directions, allowing even lower rotation speeds, since the two fans split theloadsinvolved.
VITAL Concepts COUNTER-ROTATING FAN The counter-rotating turbofan (CRTF) concept developed by Snecma is particularly innovative. This layout simply means that there are two independent shafts, rotating in opposite directions. At the other end of the low-pressure section, they are joined to a low-pressure turbine with several stages of counter-rotating blades. For a given aerodynamic load, this configuration will reduce the fan rotating speed by 30 percent or more. This fan concept is a great leap by offering the same performance as a conventional fan it manages the same airflow -, but with slower tip speeds, reducing fan noise. Therefore, engines development would be able to follow a new trend enabling a higher bypass ratio with lower fuel burn. Acoustic tests will be carried out at different speeds, with different blade configurations. Each rotor will have significantly fewer blades than a conventional fan. Tests will be performed on a 1/4-scale model at the Russian research center CIAM (Central Institute of Aviation Motors), already a partner to Snecma on several initiatives.
VITAL Concepts DIRECT DRIVE TURBOFAN The Direct Drive Turbofan (DDTF), concept developed by Rolls-Royce, remains on a similar configuration as engines of today, but would contain the increase of weight of the engine through novel lightweight materials and structures. The targeted high bypass ratio is 10 to 12. As a result of the higher bypass ratio the fan speed and pressure ratio will be reduced. Acoustic and aerodynamic tests of a fan rig will be performed at Anecom in Germany. Designs for low weight and noise LP turbines will be aerodynamically and acoustically tested in Germany, Italy and Spain. Mechanical tests of the novel fan blade, casings and structures will also be carried out.
VITAL Concepts GEARED TURBOFAN The Geared Turbofan (GTF), concept developed by MTU, is also based on a standard technology but targeting higher bypass ratios (12-15). The GTF which revivals through the use of a gear placed on the engine axe, needs that VITAL teams to develop new technologies for compressors and the low-pressure turbine. The GTF evaluations will use the same fan technology as the DDTF, both aerodynamic and mechanical.
NEWAC SP 1: Whole Engine Integration For all core concepts the requirements and objectives are defined, starting with whole engine performance cycle data. The programme compares, assess and ranks the benefits of the advanced concepts, ensuring consistency of the results and monitoring progress towards the ACARE technical and economic objectives. The new enginedesignswillbe assessed in typical aircraft applications as indicated in figure 1. Environmental Risk Analysis), previously created in the VITAL programme, in order to compare the environmental and economic impacts of the new designs. Issues to be addressed include performance, weight, engine installation, NO X and CO 2 emissions, noise, fuel costs, maintenance cost and aircraft flight path and altitude. The socio-economic model will identify engines with minimum global warming potential and lowest cost of ownership as shown in figure 2.
NEWAC SP 2: Intecooled Recuperative Core Concept This concept exploits the heat of the engines exhaust gas and maximises the heat pick up capacity of the combustor inlet air by intercooling in front of the HP compressor. EEFAE-CLEAN results showed potential in the optimisation of therecuperator arrangement (innovative duct design, radial compressor in anewdesignarea). Centrifugal HP Compressor Centrifugal compressor efficiency improvement and high hub-tip-ratio Optimisation of radial compressor/ducting interface Radial/axial compressor comparison Recuperator Improved heat exchanger and nozzle arrangement Low loss heat exchanger integration Structural and overall IRA integration aspects Future innovative core configuration Variable core cycle Innovative combustion Contra-rotating core Unconventional heat management
NEWAC SP 3: Intecooled Core Concept To utilise the CO 2 benefits of a high overall pressure ratio cycle for a given NO X level and material technology, an intercooler is included in front ofthehpcompressor.two key technologies of the intercooled core concept will be investigated in detail. One key technology is the intercooler and the related ducting, which hastohandlethefullcore mass flow and will be validated by rig tests. Then, specific HPC technologies are needed to react on the increased operability needs due to the added volumes in the compression system (intercooler, ducting) and the high OPR. These HPC technologies will be validated with rig tests. Intercooler an related ducting Design and test advanced cross-corrugated plate heat exchanger Design and validation of low pressure loss ducts Advanced OGV/diffuser Improved HPC (higher overall pressure ratio) Stability enhancement for intercooled core operability needs Improved blading and secondary flow path Improved tip clearance design
NEWAC SP 4: Active Core Concept Active systems offer the possibility to adapt the core engine to each operating condition of the mission and, therefore, the potential to optimise component and cycle behaviour. The active cooling air cooling system will be investigated for reduced cooling air consumption. To increase the effiency and the operability, the HPcompressorwillbe equipped with a active clearance control system for the rear stages and a active surge control system for the front stages. Active clearance control system (rear stages) Improved tip clearance with active clearance control system (thermalor mechanical) Comparison with alternative technologies for tip clearance improvement Active surge control (front stages) Development of an active surge control with air injection Comparison to the passive alternative multi stage casing treatment Active air cooling Gerneral concept Air cooler and control system Combustor case cooling air flow path HPC rear cone cooling
NEWAC SP 5: Flow Controlled Core Concept High BPR direct driven turbofan engines require a compact HP compressor with very high PR, which has to compensate for the low booster PR. Flow control technologies are investigated in NEWAC, which help in the specific field of very high aerodynamic loaded HPC to strongly increase efficiency and stall margin. Tip flow control and advanced aero Advanced casing concepts (Casing treatment, casing aspiration, tip injection) 3D optimised aerodynamic Stall active control integration Aspiration concept on blade profiles Aspiration concept on blade profiles Evaluation and optimisation of aspiration technology on stator vane/hubs or blade Identification of potential benefits Rub management
NEWAC SP 6: Innovative Combustor All promising approaches for significant NO X emission reduction are on the basis of lean premixing combustion technology. Lean combustion technology operates with an excess of air to significantly lower flame temperatures and consequently significantly reduce NO X formation. The optimisation of homogeneous fuel-air mixtures is the key to achieve lower flame temperatures and hence lower thermal NO X formation. However, this homogenisation has a strongly adverse effect on combustion lean stability, drastically narrowing the operating and stability range. Low NO X technology is difficult to scale to various engine sizes. As a consequence, dependingontheoverall pressure ratio of the particular engine application, different injector and combustor technologies have to be considered.