This paper discusses the Ultimate Elastic Wall Stress (UEWS) test for GRE pipes under pure hydrostatic loading. UEWS appears to provide an attractive alternative to the currently used procedure laid down in ISO 14692, which involves an expensive series of long term constant pressure tests, as described in ASTM 2992, running for a period in excess of 10,000 hours.
The pipes were subjected to biaxial loading, which was attained by combinations of hoop and axial stress. Loads were applied as groups of cycles which, were gradually increased until the UEWS had been determined. UEWS test has proved to be one of the most effective in terms of accuracy and speed. Moreover, it has been found to be sensitive to changes in key manufacturing and raw material parameters.
Modelling results are also showed a harmonic approach and accepted to that obtained experimentally. This encourages to apply the proposed modelling for further biaxial load ratios.
This paper investigates the effect of type and level of degradation in industrial gas turbine components on its performance under flexible operation due to working as a back-up to renewable energy sources (RES). This investigation was carried out for a 2-shaft 100MW aero-derivative gas turbine with intercooler. Due to the influence of unpredictable nature of power produced by RES, power plants are now operating in a flexible manner, which will require the operator to either stop operation during high feed-in from renewables or reducing the power output from the power plant to a certain percentage. This in turn has an impact on the gas turbine performance and thermal efficiency, which is also affected by the type and level of degradation of their components compared to the non-degraded gas turbines. In-House performance simulation software (TURBOMATCH), which was developed in Cranfield University, was used to carry out gas turbine performance modelling according to daily flexible operation scenarios for all seasons. These daily operating scenarios, which describe the power settings and ambient conditions for a period of 24 hours, were developed from data obtained from the UK national grid and the meteorology office data base. Different levels of degradation in mass flow and efficiency for low-pressure compressor and high-pressure turbine were applied in this study. Results illustrate an obvious impact of degradation type and level on fuel flow, turbine entry temperature, blade cooling temperature, shaft rotational speed and thermal efficiency for different seasons. This study has resulted in a tool which may be useful to power plant operators in understanding the various operating scenarios according to the criteria they wish to choose.
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