This paper investigates the dynamic behavior of an Ultra-High Efficiency Gas Turbine Engine (UHEGT) with Stator Internal Combustion. The UHEGT-technology was introduced for the first time to the gas turbine design community at the Turbo Expo 2015. In developing the UHEGT-technology, the combustion process is no longer contained in isolation between the compressor and turbine, rather distributed in the first three HP-turbine stator rows. Noticeable improvement in the engine thermal efficiency and power along with other performance advantages are brought by this technology. In the current paper, dynamic simulation is performed on the entire gas turbine engine (UHEGT) using the nonlinear dynamic simulation code GETRAN. The simulations are in 2 D (space-time) and include the majority of the engine components including rotor shaft, turbine and compressor, fuel injectors, diffuser, pipes, valves, controllers, etc. The thermo-fluid conservation laws are applied to the flow in each component which create a system of nonlinear partial differential equations that is solved numerically. Two different fuel schedules (steep rise and Gaussian) are applied to all injectors and the engine response is studied in each case. The results show that fluctuations in the fuel flow lead to fluctuations in most of the system parameters such as temperatures, power, shaft speed, etc. However, the shapes and amplitudes of the fluctuations are different and there is a time lag in the response profiles relative to the fuel schedules. It is shown that an increase in average fuel flow in the system leads to a small drop in efficiency due to the cycle change from the design point. Moreover, it is seen that the temperatures usually rise fast with increase of fuel flow, but the system tends to cool down at a slower rate as the fuel is reduced.

In the Ultra-High Efficiency Gas Turbine Engine, UHEGT (introduced in our previous studies) the combustion process is no longer contained in isolation between the compressor and turbine, rather distributed within the axial gaps before each stator row. This technology substantially increases the thermal efficiency of the engine cycle to above 45%, increases power output, and reduces turbine inlet temperature. Since the combustion process is brought into the turbine stages in UHEGT, the stator blades are exposed to high-temperature gases and can be overheated. To address this issue and reduce the temperature on the stator blade surface, two different approaches are investigated in this paper. The first is indexing (clocking) of the fuel injectors (cylindrical tubes extended from hub to shroud), in which the positions of the injectors are adjusted relative to each other and the stator blades. The second is film cooling, in which cooling holes are placed on the blade surface to bring down the temperature via coolant injection. Four configurations are designed and studied via computational fluid dynamics (CFD) to evaluate the effectiveness of the two approaches. Stator blade surface temperature (as the main objective function) along with other performance parameters such as temperature non-uniformity at rotor inlet, total pressure loss over the injectors, and total power production by rotor are evaluated for all configurations. The results show that indexing presents the most promising approach in reducing the stator blade surface temperature while producing the least amount of total pressure loss.

The Ultra-High Efficiency Gas Turbine Engine (UHEGT) was introduced in our previous studies. In UHEGT, the combustion process is no longer contained in isolation between the compressor and turbine. It is rather distributed in multiple stages and integrated within the high-pressure turbine stator rows. Compared to the current most advanced conventional gas turbines, UHEGT considerably improves the efficiency and output power of the engine while reducing its emissions and size. In this study, a six-stage UHEGT turbine with three stages of stator internal combustion is designed and analyzed. The design represents a single spool turboshaft system for power generation using gaseous fuels. The preliminary flow path for each turbine stage is designed by the meanline approach and modified using Computational Fluid Dynamics (CFD). Unsteady CFD calculation (via commercial software ANSYS CFX) is used to simulate and optimize the flow and combustion process through high-pressure turbine stages. The results show a base thermal efficiency of above 45% is achieved. It shows a successful integration of the multi-stage combustion process into the high-pressure turbine stages and a highly uniform temperature distribution at the inlet of each rotor row. High temperatures in some areas on the stator blade surfaces are controlled using indexing of fuel injectors and stator blades.

The paper investigates the dynamic behavior of an Ultra-High Efficiency Gas Turbine Engine (UHEGT) with Stator Internal Combustion. The UHEGT-technology was introduced for the first time to the gas turbine design community at the Turbo Expo 2015. In developing the UHEGT-technology, the combustion process is no longer contained in isolation between the compressor and turbine, rather distributed in the first three HP-turbine stator rows. Noticeable improvement in the engine thermal efficiency and power along with other performance advantages are brought by this technology. In the current paper, a dynamic simulation is performed on the entire gas turbine engine (UHEGT) using the nonlinear dynamic simulation code GETRAN. The simulations are in 2D (space-time) and include the majority of the engine components including rotor shaft, turbine and compressor, fuel injectors, diffuser, pipes, valves, controllers, etc. The thermo-fluid conservation laws are applied to the flow in each component which create a system of nonlinear partial differential equations that is solved numerically. Two different fuel schedules (steep rise and Gaussian) are applied to all injectors and the engine response is studied in each case. The results show that fluctuations in the fuel flow lead to fluctuations in most of the system parameters such as temperatures, power, shaft speed, etc. However, the shapes and amplitudes of the fluctuations are different and there is a time lag in the response profiles relative to the fuel schedules. It is shown that an increase in average fuel flow in the system leads to a small drop in efficiency due to the cycle change from the design point. Moreover, it is seen that the temperatures usually rise fast with increase of fuel flow, but the system tends to cool down with a slower rate as the fuel is reduced.