TBCC Engine Integrated Combustor Nozzle Aerodynamic Choke
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Solution Overview
Problem
Conventional Dual Mode Ramjet (DMRJ) engines struggle to produce thrust at low speeds due to limited ram pressure and premature thermal choking, while turbine engines face challenges operating beyond Mach 2.5 due to high air temperatures, leading to reduced thrust and increased engine weight and drag in hypersonic vehicles.
Innovation Solution
A turbine-based combined cycle (TBCC) engine integrates a turbine and DMRJ with primary ejector thrusters for low-speed thrust augmentation and a common nozzle with an aerodynamic choke to enhance thrust and efficiency, using underexpanded booster exhaust to create additional combustor area and reduce overexpansion losses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If a conventional DMRJ is used, then it cannot produce thrust to accelerate itself to supersonic speeds, but adding a turbojet booster increases the complexity of the propulsion system
Solution Approach 1:
The patent combines the turbojet and DMRJ into a single integrated propulsion system with shared airflow paths and common nozzle, allowing the turbojet to provide thrust at low speeds while the DMRJ activates at supersonic speeds, eliminating the need for separate propulsion systems and reducing overall complexity
Solution Approach 2:
The integrated system allows the same airflow path to serve dual functions: subsonic flow through the turbojet and supersonic flow through the DMRJ, with the airflow path configured to automatically transition between modes based on flight speed, reducing the need for multiple specialized components
2Speed
If the turbine engine operates as the sole propelling means during acceleration, then it can provide thrust from takeoff, but it places a great demand on turbine technologies and cannot operate efficiently beyond Mach 2.5
Solution Approach 1:
The propulsion system is segmented into two distinct operational phases: subsonic phase powered by the turbojet and supersonic phase powered by the DMRJ, with each component optimized for its specific speed range, allowing the turbojet to operate within its efficient regime without the burden of supersonic operation
Solution Approach 2:
The system dynamically transitions between turbojet and DMRJ operation based on flight speed, with the airflow path automatically reconfiguring to route air through the appropriate propulsion mode, enabling seamless operation across the full speed range from static to hypersonic
3Object-generated harmful factors
If the DMRJ flowpath is present at speeds below Mach 5, then it increases vehicle drag, but removing it eliminates the ability to produce thrust during acceleration
Solution Approach 1:
The DMRJ flowpath is designed to be dynamically active only when needed for thrust production during acceleration, with the airflow path automatically transitioning to bypass or minimize drag at cruise speeds, allowing the system to provide thrust when required while minimizing drag during steady-state flight
4Force
If the TBCC nozzle is over-expanded at speeds below Mach 5, then it reduces net thrust, but increasing the nozzle size to compensate increases vehicle empty weight
Solution Approach 1:
The nozzle is designed with variable geometry or adaptive expansion characteristics that allow it to optimize its expansion ratio based on flight speed, providing appropriate thrust at both low and high speeds without requiring a permanently oversized nozzle, thereby avoiding unnecessary weight penalties
Data Source
AI summary
An engine that operates and produces the entire required vehicle thrust below Mach 4 is useful for a Hypersonic combined cycle vehicle by saving vehicle and engine development costs. One such engine is a combined cycle engine having both a booster and a dual mode ramjet (DMRJ). The booster and the DMRJ are integrated to provide effective thrust from Mach 0 to in excess of Mach 4. As the booster accelerates the vehicle from Mach 0 to in excess of Mach 4, from Mach 0 to about Mach 2 incoming air delivered to the DMRJ is accelerated by primary ejector thrusters that may receive oxidizer from either on-board oxidizer tanks or from turbine compressor discharge air. As the TBCC further accelerates the vehicle from about Mach 0 to in excess of Mach 4 exhaust from the turbine and exhaust from the DMRJ are combined in a common nozzle disposed downstream of a combustor portion of said DMRJ functioning as an aerodynamic choke.