Black-box modelling of gas turbine engine’s electrohydraulic fuel metering system.

Document Type : Original Article

Authors

Military Technical College, Cairo, Egypt.

10.1088/1757-899X/610/1/012051

Abstract

The fuel and air flow rates are the main parameters affecting the gas turbine engine performance. The burned fuel in the combustor is the main source of heat energy. The fuel metering system (FMS) provide these engines with precise fuel mass flow rates required for regulation process. One of the most important and challenging concerns of engine design and control is, driving a valid model for the FMS. Physics-based models require well identification of the electrical and hydraulic system parameters. Measuring these parameters for the system under study, like the internal dimensions of these system components is very hard because of the system complicity and integrity. In this case it is preferred to treat the system as a black box. In this paper a transfer function model for an electrohydraulic FMS has been estimated and validated using MATLAB system identification toolbox (SIT). FMS closed loop measurements have been done for data set preparation process. Linear Variable Differential Transformer (LVDT) integrated in this system has been used for measuring the metering valve displacement which is proportionally represents the output mass flow rate. Linear variable differential transformer (LVDT) signal conditioning circuit has been designed and implemented to provide DC output voltage, proportional to the system output volume flow rate. Another conditioning circuit has been designed for output current amplification process required for electrical solenoid driving. The driven transfer function model has been validated using a different measured data set to insure a good representation of the physical system. Results show that the obtained model follows the real system with good accuracy and demonstrate the effectiveness of the transfer function modelling for the FMS.

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