Abstract
This paper discusses the change of cooling characteristics encountered in the cascade test of the first stage cooled blade for 1700℃ class turbine on the hot gas tunnel driven by the hydrogen oxygen combustion gas. The cooling effectiveness of the blade deteriorated with time during the test. Therefore, inspection of the blade surface was carried out after the test and foreign materials was found to have deposited supposedly flying from upstream parts of the test system. Heat transfer coefficient was calculated considering the roughness of the blade, and the metal temperature variation was estimated. This estimation agreed well with the test result and the factor causing the change of cooling characteristics was made clear. These phenomena are to be took into consideration as one of the development themes in case of closed internal combustion system.
