Mathematical Model of a High-bypass Turbofan with Coolant Fluid Injection into its Compressor

The paper studies a two spool-type aircraft high-bypass turbofan, equipped with a coolant injection system into its compressor (as temporarily thrust increasing method), considered as controlled object. The author has presented turbofan’s motion equations, has established the new gas-dynamic and fluid mechanics conditions when the coolant injection operates and has determined all new equation forms. Based on the finite differences method, turbofan’s mathematical model was linearized and new forms for equations’ coefficients were established. After bringing its equations to a dimensionless form and after Laplace transformation applying, mathematical model’s suitable form for studies was obtained. Turbofan’s quality study, for different possible architectures, was performed (step responses for both spools’ speeds and combustor temperature parameters); based on these studies the author has presented the conclusions regarding turbofan’s new operation mode and highlighted both the advantages and disadvantages.