Developments in Modern Aero-Engines to minimize the Impact of Bleed Air

Transcription

1 Developments in Modern Aero-Engines to minimize the Impact of Bleed Air Dr. Dieter Peitsch Rolls-Royce Deutschland Ltd. & Co. KG Dahlewitz, Germany Contact:

2 Outline Why is Customer Bleed Air an issue for the engine? What can be done to minimize the impact onto the engine? Engine Performance Hardware Design (Compressor) Safety

3 Rolls-Royce Civil engine range Trent 800 (95,000lb thrust) Trent 8104 (104,000lb thrust) Trent 700 (72,000lb thrust) RB (60,000lb thrust) RB (43,000lb thrust) BR715 (18,500-22,000lb thrust) Tay (14,000lb thrust) AE2100 (6,000 shp) T800 (1,350 shp) Trent 500 (56,000lb thrust) V2500 (25-33,000lb thrust) BR710 (14,750lb thrust) Trent 900 (80,000lb thrust) Trent 600 (65,000lb thrust) AE3007 (7,000lb thrust) FJ44 (2,000lb thrust) Model 250 (600 shp) RR Deutschland

4 Bleed Air for Cabin Air Pressurization Bleed Air taken from High Pressure Compressor (HPC) Two Offtakes to cover Pressure and Temperature Requirements of ECS over Operating Range Rolls-Royce Deutschland BR715 Core Engine Low High HPC

5 Impact of Bleed Air on Engine Performance Increase in Fuel Consumption 3 Fuel Consumption Increase (%) 2 Bypass Ratio 9:1 Bypass Ratio 5:1 1 Bypass Ratio 2:1 0 No Bypass Bleed Air taken from engine (% of total circulating Air in Cabin)

6 Impact of Bleed Air on Compressor Design Two Offtakes affect Compressor Design concerning: Casing Stiffness / Tip Clearance / Load Path along Casing Compressor Stability Low Pressure Stage High Pressure Stage

7 Minimize Impact of Bleed Air - Compressor Offtake Optimize Customer Bleed Offtakes in Compressors Divorce Customer Bleed Offtake from any other Offtake, e.g. for Secondary Air System to avoid negative Impact onto Engine Safety in Case of Customer Bleed Pipe Rupture Design Offtakes such, that Pressure Losses in the System are at a minimum level to achieve required Air Flows Target: Move Offtake to the most upstream location possible to minimize negative effect on engine performance

8 Optimization of Compressor Offtakes - Research Institute for Jet Engines (ISA), University of the German Armed Forces, Munich `Simple` Wind Tunnel with Pre-Swirl Stator and flexible offtake configurations Offtake Stator Distributor Channel Offtake Slot

9 Flow Visualization in Distributor Channel Top Wall Bottom Wall Line of Attachment Line of Detachment Line of Detachment ISA, Munich Line of Attachment

10 Derivation of Flow Model in Distributor Channel Lines of Detachment Lines of Attachment

11 Mach Number Distribution in Offtake Direction of Swirl Ma E Direction of Main Flow ISA, Munich

12 Optimization of Compressor Offtakes - Research z Computational Fluid Dynamics to assess flow paths of air flowing from compressor annulus to customer bleed port z Multiple Configurations Y X z Loss Assessment and Validation against Experiments Z ISA, Munich (Rolls-Royce Deutschland 2003)

13 Impact on Aircraft Safety Assessment Any oil leaking from an engine, entering the aircraft customer bleed offtake, is classified as HAZARDOUS Customer Bleed Offtake

14 Minimize Impact of Bleed Air Bearing Chamber Ensure reliable Sealing of Bearing Chambers Advanced Concepts and Technologies Replace Labyrinth Seals: Reduce sealing air req ments Reduce Number of Parts Less Design Complexity Prediction Capabilities for Air and Oil System Operation during transient Engine Manoeuvres Numerical Simulation: Reduce req`d safety margins Increase Accuracy for Component Specification

15 Bearing Chamber Sealing Major Design Changes Old Design (Labyrinths): Scavenge and Vent required High Air Flow Requirements for Sealing Deterioration of Seals New Design (Carbons): Combined Scavenge-Vent Less Complexity Seal Deterioration at minimum Level

16 Improve Transient Prediction Capabilities for Air and Oil System Performance Simulation of Components using MATLAB/Simulink Software Component Characteristics dependent on Engine Powersetting, e.g. Feed and Scavenge Pumps driven by Accessory Gearbox Mass Flows, Pressures and Temperatures Prediction of Time-accurate behaviour crucial to predict and avoid Oil Leakage from the Bearing Chamber

17 Result from Transient Calculation during acceleration and deceleration of the Engine Delta Pressure across air/oil seal Acceleration Deceleration Time (s)

18 Avoid negative Pressure Difference by better Scavenge Pump Delta Pressure across air/oil seal Increased Flow Capacity of Pump Time (s)

19 Avoid Oil Leakage during Transients by Introduction of a new scavenge pump control concept Air Mass Flow through carbon seal (kg/s) Time (s)

20 Finally, where is Aircraft Propulsion going to? Thank You!