标题: On Condition Maintenance [打印本页] 作者: 航空 时间: 2011-4-24 12:17:30 标题: On Condition Maintenance
作者: 航空 时间: 2011-4-24 12:17:43
On Condition Maintenance • Modern commercial turbofan engines are designed for, and usually maintained using on condition maintenance plans – The engine is serviceable when is installed – Periodic inspections are done, using several methods • Borescope inspections • External inspections • Magnetic Chip Detector inspection • Trend Monitoring and Analysis – Results are compared to limits in Maintenance Manuals – The engine is serviceable, or unserviceable, based upon the results of these inspections On-Condition Maintenance Program • On wing maintenance (Flight line maintenance) – Scheduled on wing inspection programs • Engine hardware inspections • Borescope inspections • MCD inspections – Troubleshooting and fault correction (Unscheduled) • On-condition workscoping and performance restoration – Performance removal decision • Trend Monitoring Data (SAGE) • Results of on-wing inspections – On condition workscope planning • Life Limit Parts (LLP) control Engine Thrust is Found via the Conservation of Axial Momentum, i.e. Momentum Balance Po Wo, Vo PS8 FN W8, V8 CONTROL VOLUME FN = W8 * V8 + A8 (PS8-P0) - W0 * V0 NOZZLE RAM GROSS THRUST DRAG Thrust is produced by accelerating a mass of air Core Versus Booster Airflow N2K25 Airflow Versus Corrected Core Speed Airflow - lb/sec Booster Flow Core Flow 60 70 80 90 100 CFM56-7B Thrust increase 10 20 30 40 50 60 Ambient temperature 7B18 7B26 7B24 7B22 7B20 7B27 7B26/B1 7B24/B1 7B22/B1 7B27 Bump according to N1, EGT, N2 Versus TAT Thrust increase versus 7B27 10 20 30 40 50 60 Ambient temperature 4 3 2 1 5 N1 limited EGT limited N2 limited % Typical T/O condition: Sea level / 0.25 Mn CFM56-7B27 Thrust increase Engine Performance Principles (1) • CF6 and CFM56 engines are controlled with N1 as the power setting parameter. For any flight condition: as N1 is increased, engine thrust is increased. • The increased N1 and thrust are achieved by adding energy to the system in the form of fuel. • As thrust and fuel flow are increased, engine exhaust gas temperature (EGT) increases. Fuel Flow Thrust or N1 EGT Thrust or N1 Thrust Fan Speed (N1) Engine Performance Principles (2) • As an engine deteriorate or damage occurs: the efficiency of the engine cycle is decreased. • Lower efficiency results in more fuel and higher temperature being required to achieve the same N1 or thrust. • Engine Performance Monitoring” involves monitoring the change in these parameters (EGT, Fuel Flow, N2, etc.) at constant fan speed NI. Thrust or N1 EGT Fuel Flow Thrust or N1 Takeoff EGT Margin and OATL EGT FRT TAT EGT Redline EGT Margin OATL Engine Performance Deterioration OATL Takeoff EGT Characteristics Constant Thrust Decreasing Thrust N1 TAT FRT Constant Thrust Decreasing Thrust Thrust TAT FRT EGT TAT FRT Increasing EGT Constant EGT To meet aircraft performance requirements, the engine is designed to provide a given thrust level to some “flat rate” temperature (FRT). At temperature above FRT, thrust decreases and aircraft performance is adjusted accordingly N1 for power management schedule increases with TAT (up to FRT) to maintain constant thrust. After FRT, power management N1 (and thrust) decreases EGT increases with TAT to FRT, then remains constant. 09.04.11 CFMI Proprietary Data - Unauthorized disclosure prohibited 11 Flat Rated Concept - Thrust Rating Versus Ambient Temperature -10 0 10 20 30 40 Rated Thrust at Sea Level Standard Full Throttle not to be used below Flat Rated Temperature Range Part Throttle Range Full Throttle Range “Part Throttle” Flat Rated Engine Flat Rated Temperatur e Full Throttle Below Std. Day Temp. - Thrust Exceed Rated Level Full Throttle Above Std. Day Temp. - Thrust Drops Below Rated Level Rigged to Rated Thrust at Full Throttle Under Sea Level Standard Conditions “Full Throttle” Engine -10 0 10 20作者: kinran 时间: 2011-6-4 22:55:44
