Fraunhofer Chalmers Research Centre for Industrial Mathematics
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Progression of Hot Corrosion in Ni-base Superalloys for Industrial Gas Turbines
No full textSiemens Industrial Turbomachinery AB is a world leading company that is dedicated to the manufacture of industrial gas turbines for energy generation. Industrial gas turbines are one of the most efficient and popular methods for providing energy to various sectors. Over the years, the use of these turbines has been extended due to
the development of new materials and manufacturing methods that have improved their high temperature performance allowing them to operate at higher temperatures and leading to an increase in efficiency. Aircraft engines have benefited from these advances since they operate in a similar form as industrial gas turbines. Due to the larger market size of the aircraft engine sector in comparison to that of the gas
turbine sector and the perception that both applications operate under similar conditions, the development of new materials for industrial gas turbine applications has
been neglected in favour of the development of materials for the aircraft engine market.
However, the current environmental issues have led to a diversification of fuels used in the gas turbines making them more susceptible to corrosion damage at their
current working temperatures (1350°C) in addition to working in salt-containing environments like coasts, offshore and desserts. Therefore, it is imperative that gas turbine manufacturers develop alloys that can withstand such hazardous conditions.
In this project, the progression of hot corrosion in Ni-base superalloys is evaluated in six different materials. Three of them are commercial alloys: CM247, CMSX-4 and
Inconel 792; while the other three are alloys developed by Siemens, two of which are polycrystalline and the other one is a single crystal. Samples of all of the six alloys were exposed to a mixed-sulphur atmosphere at two different temperatures (700 and 850°C) for several cycles and their corrosion products were analysed using stereomicroscopy, scanning electron microscopy and energy-dispersive X-ray spectroscopy.
At 700°C, the alloys underwent type II hot corrosion, and at 850°, they underwent type I hot corrosion. Based on a literature study and the results of the experiment,
a reaction mechanism was proposed for each case. In terms of performance, alloys CM247 and CMSX-4 suffered the most damage, followed by a polycrystalline variation
of a Siemens alloy. Inconel 792 and the single crystal variation of the Siemens alloys performed better
Project Integration Strategies to Achieve High Performance Buildings - An interview study concerning Integrated Delivery Methods in the AEC industry
No full textLow Impact Living - reducing the footprint of built environment through small home design
No full textMaintenance and operational patterns in thermal power generation
No full textWith increasing shares of solar and wind generation in the power system, the understanding
of power generation system as we know it today, needs to be reassessed.
Wind and solar power, known as the non-dispatchable generation, are likely to impact
the net load on the grid and dispatchable power production, typically thermal
power plants, will face more frequent starts and stops and volatile operational patterns.
This is expected to cause tougher conditions for the plant and result in more
critical wear on the equipment, which must be considered and accounted for.
This master’s thesis develops a method to evaluate maintenance costs depending on
the operational pattern - in terms of the number and types of start-ups - of a steam
cycle. The work focus on the steam turbine rotor but could be applied also to other
critical components of the plant. The method includes a rotor model to perform
transient simulations of the rotor temperature during start-ups. The rotor temperature
was then related to thermal stresses and life expenditure of the rotor, which are
typical input parameters to estimate maintenance costs from an LCC-perspective.
The method may be applied to evaluate the influence of energy system scenarios,
process designs, and maintenance policies.
To exemplify, this work evaluates the maintenance cost of the rotor for six defined
scenarios, four maintenance policies, i.e. failure-based, time-based, condition-based
and opportunity-based maintenance, and three types of labour services, internal,
external and contract service. The examples illustrate how the maintenance costs
may be related to the number of starts and that the proposed method may be provide
initial support to the initial discussions on the maintenance of thermal power plant
components
