A Performance Study of a Super-Cruise Engine with Isothermal Combustion Inside the Turbine

Abstract

Current thinking on the best propulsion system for a next-generation supersonic cruising (Mach 2 to Mach 4) aircraft is a mixed-flow turbofan engine with afterburner. This study investigates the performance increase of a turbofan engine through the use of isothermal combustion inside the high-pressure turbine (High-Pressure Turburner, HPTB) as an alternative form of thrust augmentation. A cycle analysis computer program is developed for accurate prediction of the engine performance and a supersonic transport cruising at Mach 2 at 60,000 ft is used to demonstrate the merit of using a turburner. When assuming no increase in turbine cooling flow is needed, the engine with HPTB could provide either 7.7% increase in cruise range or a 41% reduction in engine mass flow when compared to a traditional turbofan engine providing the sane thrust. If the required cooling flow in the turbine is almost doubled, the new engine with HPTB could still provide a 4.6% increase in range or 33% reduction in engine mass flow. In fact, the results also show that the degradation of engine performance because of increased cooling flow in a turburner is less than half of the degradation of engine performance because of increased cooling flow in a regular turbine. Therefore, a turbofan engine with HPTB will still easily out-perform a traditional turbofan when even more cooling than currently assumed is introduced. Closer examination of the simulation results in off-design regimes also shows that the new engine not only satisfies the thrust and efficiency requirement at the design cruise point, but also provides enough thrust and comparable or better efficiency in all other flight regimes such as transonic acceleration and takeoff. Another finding is that the off-design bypass ratio of the new engine increases slower than a regular turbofan as the aircraft flies higher and faster. This behavior enables the new engine to maintain higher thrust over a larger flight envelope, crucial in developing faster air-breathing aircraft for the future. As a result, an engine with HPTB provides significant benefit both at the design point and in the off-design regimes, allowing smaller and more efficient engines for supersonic aircraft to be realized.

Study on aero engine thermal performance analysis using a new mathematical model of isentropic expansion (compression) process

“…At present, research on the mathematical model [14,21,23,24] of the isentropic compression/expansion process is based on the energy balance formula. Figure 2 lists the current main mathematical models (taking the isentropic expansion process as an example), including the isentropic expansion process mathematical model based on the Φ function which is derived from the definition of process efficiency.…”

“…It is quite common to study the complete aero engine overall performance analysis and calculation program [1][2][3][4][5][6] in the world. In the general aero-engine overall performance analysis and calculation program, a lot of research has been carried out on the isentropic expansion (compression) process mathematical model [7][8][9][10][11][12][13][14][15].…”

Control strategy for turbo-shaft engine with Inter-stage Turbine Burner

“…Recently, gas turbine scientists and engineers seem to encounter a bottleneck to further enhance the engine cycle parameters because of critical engine thermal limit and stress level [I,2]. In such conditions, a innovative solution called inter-stage turbine burner(ITB) was proved to have significant potentials for jet engines performance enhancement under the conditions of the same engine total pressure ratio and turbine entry total temperature [3][4][5][6].…”

Performance evaluation of a novel re-cooled mixed-flow turbofan cycle for aviation power application

“…For these reasons, Liew et al [17][18][19] added an inter-turbine burner between high-pressure turbine and low-pressure turbine. Chiu et al [20] proposed a turbine inter-vane burner, in which the gas was burned directly between two vanes without a chamber. This new design was introduced into the engines of F101 and TF34.…”