Turbine-based Combined Cycle Propulsion System Research Articles

Multi-fidelity simulation of inlet mode transition with smooth thrust of turbine based combined cycle

A multi-fidelity simulation method of external and internal flow has been developed using commercial software to achieve a smooth thrust of the turbine-based combined-cycle (TBCC) propulsion system. This platform enables the investigation of the flow field and performance of the TBCC propulsion system at different mode transition schemes. The integrated multi-fidelity simulation includes the inlet, turbojet engine, ramjet engine, and nozzle, providing insights into the operation process of the TBCC propulsion system during the transition from turbojet mode to ramjet mode. Three mode transition schemes are proposed: critical mode transition, constant aerodynamic interface plane (AIP) Mach number mode transition, and linear mode transition. From the perspective of TBCC inlet, the performance of the critical mode transition exhibits the best performance among these mode transition schemes, while the linear mode transition performs the worst. However, from the viewpoint of the TBCC propulsion system and the hypersonic vehicle, the performance of constant AIP Mach number mode transition is the best. The non-dimensional thrust increases almost linear from 1.0 to 1.2, enabling hypersonic vehicle to accelerate steadily during the transition from turbojet mode to ramjet mode.

Simple model of turbine-based combined cycle propulsion system and smooth mode transition

Abstract Turbine-based combined cycle (TBCC) propulsion system is becoming one of the most promising propulsion systems for two-stage-to-orbit reusable launch vehicle. Mathematic model of this combined cycle engine is helpful for the basic understanding of performance analysis of this propulsion system. We developed mathematic model of TBCC propulsion system based on C++ platform in this paper. Firstly, turbojet engine was built on component level and ramjet engine was calculated through stream thrust function. Then, performance of turbine-based combined cycle propulsion system along a specific flight trajectory was investigated. According to the thrust of this combined cycle engine, mode transition point was suggested at Ma 2.5, which may achieve smooth mode transition from turbine mode to ramjet mode. Finally, mode transition based on smooth mass flow and smooth thrust criteria were studied. The thrust gap arises during smooth mass flow mode transition, particularly when the turbojet engine afterburner is powered off at the start of the mode transition, and it meets 34 % of the total thrust. Smooth thrust mode transition may be achieved by delaying the turbojet engine afterburner power off and injecting additional fuel into ramjet burner.

Research of parameters and characteristicsof the turbine-based combined cycle propulsion system of an advanced high-speed aircraft

Research of parameters and characteristicsof the turbine-based combined cycle propulsion system of an advanced high-speed aircraft

Modeling and mode transition simulation of over-under turbine based combined cycle (TBCC) propulsion system based on inlet/engine matching

Abstract The over-under turbine based combined cycle (TBCC) propulsion system dynamic model is established, including the engine model and inlet model. A dual-channel inlet is designed to match the engine and the inlet performance parameters are obtained by computational fluid dynamics (CFD) calculation, which provides original data for the integrated Inlet/Engine matching model. Control plan is designed to ensure that the engine is not over-temperature, over-rotation or surging based on correlation analysis. The simulation results show that the designed control plan can keep the TBCC propulsion system continuous in thrust during the mode transition, and the thrust fluctuation is about 10%.

The design and validation of over/under turbine-based combined cycle inlet

The design constraints including capture area and mode transition point of turbine-based combined cycle (TBCC) inlet are determined by the performance analysis of combined cycle propulsion system. According to the mass flow and thrust requirement of the combined cycle engine, the capture area of 1.0 m2 and mode transition between Ma 2.2 and 2.5 are recommended. Based on these two quantities an over/under TBCC inlet which can operate from takeoff to Ma 4.0 is designed. The variable geometry scheme of TBCC inlet is shown at different flight Mach number. Three dimensional numerical simulations of full-scale model and wind tunnel test of 8-percent scale model are explored to verify this inlet design method. The results from the numerical simulations and experimental tests indicate that the TBCC inlet could work properly during this Mach number range. The mass flow captured by the inlet and total pressure recovery at turbine/ramjet aerodynamic interface planes (AIP) meet the requirement of the TBCC propulsion system.

Research on Integrated Design of Multi-variable Combination Adjusting Laws of Inlet/TBCC Engine

One of the most critical challenges for the turbine-based combined cycle (TBCC) propulsion system utilized in the next generation hypersonic aircraft lies in the efficient operation from Mach 0 to Mach 5. This results in a need to investigate the well matching of the hypersonic inlet and the TBCC engine along the wide flight regime. In order to get better installed performance of Mach 5 TBCC engine, Newton-Raphson algorithm is adopted to investigate the integrated optimization design of the multi-variable combination adjusting laws of inlet/TBCC engine in different flight sections which include the hypersonic cruise section, the climbing section of ramjet mode and the climbing section of turbofan mode. How to guarantee the variable geometries function of the inlet/engine efficiently along the wide flight regime is one of the most critical technology challenges. The innovation point of the paper lies in that it affords an integrated optimization design of the adjustable geometries of inlet and the control laws of TBCC engines, using the multi-dimensional Newton-Raphson algorithm, which can achieve lower fuel consumption and better installed performance along the wide operating range, which is beneficial for the conceptual design and performance research of Mach 5 TBCC propulsion system. Meanwhile, the integrated optimization design method could also be applied to the power systems of multiple adjustable mechanisms, in order to increase the energy efficiency.

Performance uncertainty propagation analysis for control-oriented model of a turbine-based combined cycle engine

Uncertainty sources in an integrated turbine-based combined cycle propulsion system considered in this study are located at the air intake system, containing a forebody, a splitter and a cowl. These components endure aerothermodynamic loading and variational pressure distribution due to oblique shocks, which cause them to deform and vibrate. Those deformations and vibrations are largely determined by the local flow field and structural characteristics of the propulsion system in real time, which are hardly to be modeled. The unanticipated uncertainties bring in fluctuations on performance, and may even lead to inlet unstart, compressor surge, or combustor overtemperature, and bring about difficulties in designing control systems that can meet certain requirements on performance. Therefore, uncertainty propagation is made to figure out the effects of uncertainties associated with the three components on control-oriented performance analysis of a turbine-based combined cycle engine. A control-oriented loosely coupled aircraft/propulsion integrated turbine-based combined cycle engine model is built. Monte Carlo Method is utilized to propagate the uncertainties. The results reveal that uncertain sources may bring about failure in mode transition because of the possibility that the gross thrust with uncertainties exceeds the limits. Further analyses indicate that the principal contributor to the uncertainties of outputs in low speed flow path varies from the forebody to the splitter as transition process goes on.

Preliminary research of terminal shock motion in tandem configuration turbine-based combined cycle inlet

ABSTRACTThe pressure oscillation and terminal shock motion in a two dimensional inlet, which was designed for tandem configuration turbine-based combined cycle propulsion systems was investigated experimentally and numerically, respectively. The inlet was characterised by a bleed cavity upstream the inlet throat, an S-shape rectangular-to-circular diffuser and flowpaths for a turbine and a ramjet engine. The terminal shock motion was calculated through a second-order unsteady Reynolds-averaged Navier-Stokes scheme. The pressure and the terminal shock were unsteady when the combined cycle inlet operated at different conditions. With the terminal shock located in the throat and at the shoulder of the third ramp of the TBCC inlet, the pressure oscillation was significant and the shock exhibited unsteady streamwise motion with an oscillatory pattern. The amplitude of shock oscillation at these two conditions was 6mm and 12mm, respectively. When the shock was located downstream of the throat and upstream of the cowl lip, it oscillated in a small range. We defined this motion as the “shake” of the shock. This unsteady behaviour of the shock was caused by flow separation in the combined cycle inlet diffuser.

Turbine-based combined cycle propulsion system integration concept design

One of the most critical challenges for turbine-based combined cycle propulsion systems utilized in hypersonic civil aircrafts (Mach 0 to Mach 5) lies in guaranteeing the propulsion system to operate efficiently and stably along a very wide operating range. This has resulted in a need to investigate the matching restraints between the inlet and turbine-based combined cycle engine and nozzle from the integration point of view at the early stage of design. To get a good understanding of this integration concept design process, in this article, several basic design principles were first put forward. Next, a fast, versatile and trusted modular analysis tool for this concept design was developed and implemented. Third, several issues on this concept were analyzed including the design issues, the mechanisms of the variable geometries as well as the control schedules. Finally, a solution for the turbine-based combined cycle propulsion system was carried out and discussed. The results show that at least 11 total variables were required to be adopted in the variable cycle propulsion system to meet the basic mission requirements for Mach 5 civil airplane. How to guarantee these variable geometries function efficiently and reliably along the wide flight regime is one of the most critical technology challenges to make this concept feasible. The uniqueness of the developed analysis tool lies in that it affords a platform capable of investigating the design constraints and the matching relationships between the various propulsion components along a wide operating range, which is beneficial to predict the potential critical technological barriers at the early design stage.