Abstract
The micro-turbine unit is intended to provide 100 kW of electric supply. The turbine is small size (turbine wheel diameter 150 mm), high speed (65,000 rpm), and should have big enough durability (60,000 hours). Creep in stationary regime and cyclic inelastic deformation due thermal stresses at start up and stop restricts the turbine lifetime. Numerical analysis of temperatures, the creep strains and cyclic strain range shows that points with maximum creep damage and cyclic damage are different. This fact allows estimating the structure lifetime without exact knowledge of summation rule for the damages.
Highlights
Designed micro-turbine unit is intended for de-centralised electrical supply, output electric power is 100 kW
Strength and lifetime of the turbine disc in these conditions is restricted by a number of limit states: - creep strain accumulation and quasi-static damages caused by the creep; - accumulation of cyclic damages caused by variable thermal stresses at "start-stop" cycles; - possible residual displacement accumulation due to nonisochronic character of inelastic deformation in differrent parts of the structure (“incremental collapse” or ”ratcheting”); - vibrations and high-cycle fatigue, material degradation in aggressive gas environment, etc
The paper deals with the limit states connected with the inelastic strains and their influence on the structure durability
Summary
Designed micro-turbine unit is intended for de-centralised electrical supply, output electric power is 100 kW. Estimated parameters of the turbine are [1]: nominal rotational speed 65000 rpm, life 60,000 hours, the gas temperature at the turbine inlet 1173K, outlet – 873K. One of the most stressed parts of the unit is turbine disc, subjected to high temperatures, centrifugal forces, and variable thermal fields during the turbine start-stop. Strength and lifetime of the turbine disc in these conditions is restricted by a number of limit states: - creep strain accumulation and quasi-static damages caused by the creep; - accumulation of cyclic damages caused by variable thermal stresses (and inelastic strains) at "start-stop" cycles; - possible residual displacement accumulation due to nonisochronic character of inelastic deformation in differrent parts of the structure (“incremental collapse” or ”ratcheting”); - vibrations and high-cycle fatigue, material degradation in aggressive gas environment, etc. The paper deals with the limit states connected with the inelastic strains (including creep) and their influence on the structure durability
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