Similarity tests used to analyze field tests of state-of-the-art gas turbine engines: introducing power parameter

BACKGROUND: With the increasing complexity of gas turbine units, processing of gas turbine engine (GTE) test results have become a frequent practice. However, the methods are mostly based on mathematical GTE models and climatic reference maps rather than the principles of similarity. In this case, it is believed that that methods based on the specified parameters are outdated or their application is limited to only the simplest gas turbine engine designs. This paper shows that the similarity theory of modes can be successfully applied to solve some real-life engineering problems for state-of-the-art gas turbine units. AIM: To consider application of similarity theory methods to process test results and analyze the operation of state-of-the-art gas turbine units and to propose advanced dimensionless groups. METHODS: To analyze the possible use of the reduced gas turbine unit (GTU) parameters, we calculated the corresponding variable modes using a thermodynamic GTU model with a free power turbine developed and verified based on field tests at various outside air temperatures. RESULTS: Calculations of variable modes based on a mathematical GTU model were used to analyze the applicability of existing standard reduced GTU parameters and the corresponding dimensionless groups. The authors propose an advanced dimensionless group (a power parameter) and show its possible engineering applications. CONCLUSIONS: Variant calculations based on a mathematical GTU model show that it is possible to present the outcomes of tests in arbitrary conditions in a convenient representable form based on the power parameter, even if the conventional similarity of modes is not achieved. The power parameter allows for continuous testing of the rated GTU power in any actual operating mode for continuous monitoring of its status.