Method of coordinating joint operation of air starter and auxiliary power unit and determining the gas turbine engine starting time

The article describes the method developed by the authors to coordinate the working process of the auxiliary power plant (APP) and the starter air turbine (SAT) used for starting a gas turbine engine (GTD). This method is used to test the possibility of joint operation of the APP and the air turbine in the gas turbine engine starting system in given operating modes. The method is based on combining the APP and turbine characteristics shown in the same coordinates on the same field and checking for intersection points. The condition of joint operation is fulfilled in them. Non-crossing graphs indicate the impossibility of joint work in the selected operating mode. The developed method takes into account losses and leaks in the engine starting system pipes. The data obtained using the developed method are source data for calculating and optimizing the air turbine's working process and for  determining the time required to start the GTE, as well as for testing the operability of the GTE system by strength and other criteria. An algorithm for calculating the time required to start the GTE was also developed by the authors and implemented as a computer program. The obtained data can be used to analyze the possibility of starting the engine and to calculate its main parameters for specific elements of the engine starting system, to select the APP and SAT to meet the specifications.