Auxiliary Power Unit Heat Recuperation for Turbine Startup
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Solution Overview
Problem
Externally-heated gas turbine engines face challenges in achieving sufficient startup temperatures due to slow heat generation from nuclear reactors, which can result in inadequate power production until the reactor reaches steady-state operation.
Innovation Solution
A power-generation system incorporating a heat recuperating system that includes an auxiliary power unit and a recuperating heat exchanger, which supplements the heat from the nuclear reactor by transferring waste heat from the auxiliary power unit's exhaust air to the compressed air, ensuring the turbine engine operates at the required temperature for startup.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If heat is supplied only from the nuclear reactor heat exchanger during startup, then the system structure remains simple, but the turbine inlet temperature rises too slowly to achieve required power levels
Solution Approach 1:
The auxiliary power unit is activated before the main turbine to pre-heat the compressed air through the recuperating heat exchanger. This preliminary heating action ensures that when the reactor comes online, the air is already at a higher temperature, reducing the time to reach turbine startup conditions.
Solution Approach 2:
The recuperating heat exchanger serves as an intermediary device that transfers heat from the auxiliary power unit's exhaust to the compressed air stream. This mediator enables efficient heat transfer between the auxiliary system and the main turbine inlet, accelerating the heating process without direct combustion in the main turbine path.
2Productivity
If an auxiliary power unit with recuperating heat exchanger is added to accelerate heating, then the startup temperature is achieved faster, but the system complexity increases
Solution Approach 1:
The auxiliary power unit serves multiple functions: it generates electrical power during startup to run system equipment, provides heat through its exhaust to pre-heat the compressed air via the recuperating heat exchanger, and can be shut down once the reactor is operational. This multi-functionality justifies the added complexity by providing both power and thermal support during the critical startup phase.
Solution Approach 2:
The system recovers waste heat from the auxiliary power unit's exhaust that would otherwise be discarded. By capturing this thermal energy through the recuperating heat exchanger and transferring it to the compressed air, the system converts what would be waste into a useful resource for accelerating turbine startup, improving overall efficiency despite the added complexity.
3Reliability
If the auxiliary power unit operates continuously, then sufficient heat is always available, but energy waste increases when reactor heat is sufficient
Solution Approach 1:
The controller continuously monitors the temperature of the compressed air and the operational status of the reactor heat exchanger. Based on this feedback, it automatically activates or deactivates the auxiliary power unit. When the reactor provides sufficient heat, the controller shuts down the auxiliary unit, preventing energy waste while ensuring heat availability is maintained through responsive control.
Solution Approach 2:
The auxiliary power unit's operation is made dynamic rather than static. It operates only when needed during startup or when reactor heat is insufficient, and is deactivated when the reactor can meet the thermal requirements. This dynamic operation optimizes the balance between heat supply reliability and energy efficiency based on real-time system conditions.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The system effectively increases the inlet temperature of the turbine engine during startup, reducing the power required for initiating the power-generation system and ensuring consistent energy production by activating the auxiliary power unit until the nuclear reactor reaches sufficient heat levels.
Implementation Method 1
The reactor heat exchanger may be in fluid communication with and between the compressor and the turbine. The reactor heat exchanger may be configured to transfer heat from the nuclear reactor to the compressed air to heat the compressed air.
Implementation Method 2
The recuperating heat exchanger may be fluidly connected with the auxiliary power unit and configured to transfer heat from the heated exhaust air to the compressed air.
Data Source
AI summary
A power generation system for a nuclear reactor includes an externally-heated turbine engine, a reactor heat exchanger, and a heat recuperating system. The externally-heated turbine engine produces compressed air that is heated by the reactor heat exchanger. The heat recuperating system includes a heat exchanger thermally connected to the externally-heated turbine engine to transfer heat to the compressed air to supplement the reactor heat exchanger.