Implications of Turbine Erosion for an Aero-Engine’s High-Pressure-Turbine Blade’s Low-Cycle-Fatigue Life-Consumption

2009 ◽  
Vol 131 (5) ◽  
Author(s):  
Muhammad Naeem
Keyword(s):  
High Pressure ◽  
Fatigue Life ◽  
Low Cycle Fatigue ◽  
Life Cycle Costs ◽  
Cycle Fatigue ◽  
Mechanical Device ◽  
High Pressure Turbine ◽  
Aero Engine ◽  
Life Consumption ◽  
Mission Profile

Some in-service deterioration in any mechanical device, such as a military aero-engine, is inevitable. As a result of experiencing any deterioration, an aero-engine will seek a different steady operating point thereby resulting in a variation in the high-pressure spool speeds in order to provide the same thrust to keep aircraft’s performance invariant. Any increase in the high-pressure spool speed results in greater low-cycle fatigue damage for the hot-end components and thereby higher engine’s life-cycle costs. Possessing better knowledge (of the impacts of high-pressure turbine’s erosion upon the low-cycle fatigue life-consumption of aero-engine’s hot-end components) helps the users to take wiser management decisions. For a military aircraft’s mission profile, using bespoke computer simulations, the impacts of turbine erosion for high-pressure turbine-blade’s low-cycle fatigue life-consumption have been predicted.

Impacts of low-pressure (LP) compressor’s deterioration upon an aero-engine’s high-pressure (HP) turbine blade’s life consumption

2006 ◽  
Vol 110 (1106) ◽  
pp. 227-238 ◽  
Author(s):  
M. Naeem
Keyword(s):  
High Pressure ◽  
Low Pressure ◽  
Life Cycle Costs ◽  
Military Aircraft ◽  
Mechanical Device ◽  
Operating Characteristics ◽  
Performance Simulation ◽  
Computer Performance ◽  
Aero Engine ◽  
Life Consumption

AbstractSome in-service deterioration in any mechanical device, such as an aero-engine, is inevitable. As a result of experiencing a deterioration of efficiency and/or mass flow, an aero-engine will automatically adjust to a different set of operating characteristics; thereby frequently resulting in changes of rpm and/or turbine entry temperature in order to provide the same thrust. Rises in the turbine entry-temperatures and the high-pressure turbine’s rotational speed result in greater rates of creep and fatigue damage being incurred by the hot-end components and thereby higher engine’s life cycle costs. Possessing a better knowledge of the effects of engine deterioration upon the aircraft’s performance, as well as fuel and life usages, helps the users to take wiser management decisions and hence achieve improved engine utilisation. For a military aircraft, using a computer performance simulation, the consequences of low-pressure (LP) compressor’s deterioration upon an aero-engine high-pressure (HP) turbine blade’s life-consumption have been predicted.

A Novel Experimental Method for LCF Measurement of Nickel Base Super Alloys in High Pressure High Temperature Supercritical CO2

2017 ◽  
Author(s):  
Azam Thatte ◽  
Etienne Martin ◽  
Tim Hanlon
Keyword(s):  
High Pressure ◽  
High Temperature ◽  
Fatigue Life ◽  
Crack Initiation ◽  
Conversion Efficiency ◽  
Supercritical Co2 ◽  
Low Cycle Fatigue ◽  
Total Power ◽  
Cycle Fatigue ◽  
High Pressure High Temperature

CSP plants using supercritical CO2 (sCO2) power cycle can potentially achieve high thermal conversion efficiency at low capital cost due to compact turbomachinery and other components. An sCO2 expander and improved heat exchanger is expected to provide a major stepping stone for achieving CSP power at $0.06/kW-hr LCOE, energy conversion efficiency > 50%, and total power block cost < $1,200/kW installed. However the life limiting mechanisms of these turbomachines in high pressure, high temperature sCO2 environment are not well understood. To understand the effect of high pressures, high temperatures and sCO2 chemical kinetics on crack initiation, crack propagation and low cycle fatigue (LCF) life of these turbomachines, a novel experimental setup is developed. Advanced microstructure and spectroscopic analyses are conducted that shed light on some key differences between various Ni base alloys in terms of oxidation morphology, chemical species diffusion and trapping, the formation of protective corrosion resistant layers and changes in surface properties. An experimental technique for low cycle fatigue experiments in high pressure, high temperature supercritical CO2 environment is developed. The test setup allows for pressurized LCF testing of alloys being considered for MW scale sCO2 turbine development. Results show that the LCF life remains the same (within the scatter band) irrespective of the location of crack initiation site whether at the OD (non shot-peened bars in air and sCO2), or at the ID (shot peened bars). Total fatigue life, for all conditions, lie within the normal variation in LCF results (± 2X life variation). No significant LCF life debit is observed in IN718 by sCO2 at 550 °C, 0.7% max strain, 20 cpm. Similar conclusion is reached during 0.6% max strain tests. The effect of sCO2 is found not to be significantly more damaging than air at these strain levels. However, the results can be different for lower % max strains due to longer exposure times involved, resulting from larger number of cycles to failure. Similarly at higher temperatures and/or longer hold-times, sCO2 environment may be more aggressive, resulting in lower total fatigue life.

Influence of Surface Anomalies Following Hole Making Operations on the Fatigue Performance for a Nickel-Based Superalloy

2014 ◽  
Vol 136 (5) ◽  
Author(s):  
C. Herbert ◽  
D. A. Axinte ◽  
M. Hardy ◽  
P. Withers
Keyword(s):  
Free Surface ◽  
Fatigue Life ◽  
Surface Integrity ◽  
Low Cycle Fatigue ◽  
White Layer ◽  
Fatigue Performance ◽  
Cycle Fatigue ◽  
Nickel Based Superalloy ◽  
Aero Engine ◽  
Hole Making

Aero-engine manufacturers are continuously striving to improve component performance and reliability while seeking to increase the efficiency of manufacturing to reduce costs. Efficiency gains by using higher rates of material removal, however, can be counter-productive if they give rise to surface anomalies that distort the material microstructure and reduce the resistance of the material to fatigue crack nucleation. This paper investigates the effect of hole making processes and parameters on surface integrity and the initiation of cracks from low-cycle fatigue (LCF). It reports the dependence of elevated temperature (600 °C) low-cycle fatigue performance of nickel alloy RR1000 from surfaces produced from hole making and subsequent surface conditioning. As-machined surfaces include a reference “damage-free” surface, and two distorted microstructures: (i) a white layer, produced to a depth of 5 and 10 μm and (ii) a distorted gamma prime (γ') structure, produced to a depth of 10 and 15 μm. The effect of shot peening damage-free and 10 μm deep white layer surfaces was also evaluated. It was found that the presence of white layer significantly reduced fatigue performance compared with that shown by the damage-free surface, regardless of whether the white layer was subsequently shot peened or not. In contrast, surfaces showing distorted γ' structures produced much less debit in fatigue life and only from a depth of 15 μm. These results have been rationalized from an examination of fracture surfaces and from measurement of residual stresses before and after fatigue testing. This research is of particular importance as it is among the few reports that quantify the effect of different levels of work piece surface integrity on the fatigue life of a nickel-based superalloy that has been developed for critical rotating components in aero-engine applications.

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