Cryogenic Bottoming Cycle Loop Split for Adaptive Heat Rejection
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Solution Overview
Problem
Existing gas turbine engines waste a significant amount of thermal energy in the exhaust, and the capability of working fluids in bottoming cycles to absorb heat is limited, restricting energy recovery.
Innovation Solution
Incorporating a cryogenic fuel system with a bottoming cycle that includes a primary and secondary compressor loop, exhaust gas heat exchangers, and recuperative heat exchangers, along with a controller to adjust fluid flow through these loops based on the cryogenic fuel's thermal capacity, allowing for efficient heat absorption and power generation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If a single compressor loop is used in the bottoming cycle, then the system structure is simple, but the energy recovery capability is limited due to fixed heat absorption capacity
Solution Approach 1:
The bottoming cycle is divided into two separate compressor loops (primary and secondary) with independent flow paths. Each loop can be independently controlled to optimize heat absorption under different operating conditions, thereby increasing overall energy recovery capability without creating a single point of failure
Solution Approach 2:
The system incorporates flow control valves and switching mechanisms that dynamically adjust the distribution of working fluid between the primary and secondary compressor loops based on real-time thermal capacity requirements of the cryogenic fuel system, enabling adaptive energy recovery
2Productivity
If the bottoming cycle is designed for maximum heat absorption, then energy recovery is maximized, but the system becomes inflexible when cryogenic fuel thermal capacity varies
Solution Approach 1:
The dual compressor loop system with flow control valves enables dynamic adjustment of working fluid distribution. When cryogenic fuel thermal capacity is high, more flow is directed through the primary loop; when thermal capacity is low, flow is redirected to the secondary loop or reduced, maintaining optimal energy recovery while adapting to varying thermal conditions
Solution Approach 2:
The system changes operational parameters (flow rates, pressure levels, temperature gradients) in the compressor loops based on the thermal capacity state of the cryogenic fuel system, allowing the bottoming cycle to maintain high productivity across different operating conditions rather than being fixed at a single design point
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
Enhances energy recovery by adapting the bottoming cycle to varying thermal capacities, improving efficiency and power generation in gas turbine engines.
Implementation Method 1
an exhaust gas heat exchanger where heat from the exhaust gas flow heats the working fluid of the bottoming cycle
Implementation Method 2
a fuel/working fluid heat exchanger for cooling the working fluid within the primary compressor loop
Implementation Method 3
a working fluid is heated and expanded through a bottom turbine to generate shaft power
Data Source
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Figure 2
AI summary
An aircraft propulsion system (20) includes a core engine (24) that includes a main compressor (26) where an inlet airflow (40) is compressed and communicated to a combustor (28) to generate an exhaust gas flow (42) that is expanded through a main turbine section (30) to generate power that is used to drive the main compressor (26) and a propulsive fan (22), a bottoming cycle (60) where a working fluid is heated and expanded through a bottoming turbine (66) to generate shaft power, the bottoming cycle (60) includes a primary compressor loop (68) that includes a first bottoming compressor (62) and a secondary compressor loop (70) that includes a second bottoming compressor (64) and the flow of working fluid (74) is adjusted to flow through at least one of the primary compressor loop (68) and the secondary compressor loop (70), an exhaust gas heat exchanger (44) where heat from the exhaust gas flow (42) heats the working fluid of the bottoming cycle (60), a cryogenic fuel system (48) that includes a cryogenic fuel storage tank (50), a fuel flow path for routing the cryogenic fuel (56) to the combustor (28) of the core engine (24), and a fuel/working fluid heat exchanger (54) for cooling the working fluid within the primary compressor loop (68). The secondary compressor loop (70) bypasses the fuel/working fluid heat exchanger (54).