Increasing the Turbine Inlet Temperature (TIT) has been used as a means of obtaining substantial performance improvements for both aeronautical and land-based gas turbines. However, TIT is limited by environmental issues and material life requirements. In current engines, TIT far away exceeds the melting point of the blade material. Operating at this elevated temperature without causes severe damage to the hot gas-path components is only possible using cooling techniques and thermal barrier coating (TBC). This condition ensures a safe engine operation, while satisfies performance and component life requirements. Generally, a portion of air is bled from the compressor for cooling purposes. The amount of cooling air to be bleed depends on many factors, such as gas temperature, compressor pressure ratio, cooling technique, and component material. The objective is to use the minimal amount of cooling air to keep the component temperature at an acceptable level, while it produces the smallest negative impact on the engine performance. The turbine blade cooling decreases the engine performance when compared with the uncooled engine at the same operating condition. It must be emphasized that this comparison is related to an ideal case because the real engine cannot operate at a gas temperature higher than the allowed material temperature without using cooling or TBC. Since the actual gas turbines operate at elevated cycle temperature, the cooling effects must be considered for all engine performance estimation phase. In this work, it is proposed to develop a computational tool able to estimate the performance of an engine with turbine blade cooling, regardless of the cooling technique used and operating conditions. Different methodologies were proposed for parametric study, design point calculation, at off-design estimation. Besides, methodologies were developed and implemented to give support to these simulations. For instance, the methodology developed to assist the user in selecting the cooling technique for each blade row. A simulation was carried out for a single spool turbojet engine to demonstrate the program's capability to simulate the cooling effects at different phases of engine performance estimation. The results highlighted the importance of considering the cooling effects on the calculations. In another study, Consonni's model was used to investigate how the cooling parameters are affected by changes in the mainstream gas properties. Four fuel compositions were used in the simulations: kerosene; diesel; methane; and residual oil. Results demonstrated that the values of coolant to gas specific heat ratio (cpc/cpg) and Reynolds number (Re) strongly affect the cooling parameters, such as the cooling mass flow ratio (?c/?g). At off-design, three approaches for cooling airflow predictions were implemented. A two-spool turbofan engine with turbine blade cooling was simulated at off-design using the three approaches. The results demonstrated that the modulated model requires a lower cooling airflow to keep blade metal temperature operating below its limit temperature.