Cryogenic Fuel Startup Heating for Low-Energy Engine Vaporization
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Solution Overview
Problem
Cryogenic fuels stored in a liquid state require significant energy to vaporize without access to heat generated during engine operation, posing a challenge in starting gas turbine engines efficiently.
Innovation Solution
A two-stage engine start system is employed, where a first stage generates a first quantity of thermal energy to heat a portion of fuel, and a second stage uses the heated fuel to generate a higher second quantity of thermal energy, which is used to vaporize the fuel, supplemented by a bottoming cycle that recovers thermal energy from the core engine for further fuel heating during steady-state operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If cryogenic fuel is heated without access to engine-generated heat, then fuel vaporization can be achieved, but significant energy consumption is required
Solution Approach 1:
The system performs preliminary heating of a first portion of the cryogenic fuel using an electric heater or blower before the engine is operational. This pre-heated fuel is then used in the second stage to generate thermal energy that heats the second portion of fuel, eliminating the need for continuous high-energy input once the engine starts.
Solution Approach 2:
The system transitions to self-service mode once the engine is running, where the engine's own exhaust heat is captured and used to vaporize the remaining cryogenic fuel. The heat recovery system automatically captures thermal energy from the exhaust gases and uses it to heat the fuel, making the system self-sustaining without external energy input.
2Productivity
If a two-stage heating system is implemented, then fuel vaporization efficiency is improved, but system complexity increases
Solution Approach 1:
The heating system is divided into two distinct stages: a first stage using an electric heater or blower to heat an initial portion of fuel, and a second stage using the heated fuel to generate thermal energy for heating the remaining fuel. This segmentation allows each stage to be optimized for its specific function while working together to achieve complete fuel vaporization.
Solution Approach 2:
The system changes the thermal parameters of the fuel in two distinct phases. The first stage raises the temperature of the first portion of fuel from cryogenic conditions to a usable temperature range. The second stage then uses this heated fuel to raise the temperature of the second portion of fuel to the required vaporization temperature, achieving efficient phase change through controlled parameter transitions.
3Loss of energy
If thermal energy is recovered from core engine, then additional fuel heating capability is achieved, but system complexity increases
Solution Approach 1:
The system converts the waste thermal energy in the engine exhaust into a useful resource for heating cryogenic fuel. The heat recovery system captures thermal energy that would otherwise be lost to the environment and uses it to vaporize remaining fuel in the fuel tank, turning a harmful waste product into a beneficial heating source that improves overall system efficiency.
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
Efficient vaporization of cryogenic fuels is achieved, reducing energy consumption and ensuring reliable engine start-up, with the system transitioning to core engine heat for steady-state operation.
Implementation Method 1
a first stage that generates a first quantity of thermal energy for heating a first portion of fuel
Implementation Method 2
a second stage that utilizes the heated first portion of fuel to generate a second quantity of thermal energy for heating a second portion of fuel
Implementation Method 3
a second stage that utilizes the heated first portion of fuel to generate a second quantity of thermal energy
Implementation Method 4
a bottoming cycle where thermal energy from the core engine is recovered and utilized to heat a portion of fuel flow within the primary fuel path
Data Source
AI summary
An aircraft propulsion system includes a core engine that includes a combustor where a cryogenic fuel is mixed with compressed air and ignited to generate an exhaust gas flow, a propulsive fan that is driven by shaft power generated by the core engine, a cryogenic fuel system that includes a cryogenic fuel storage tank and a fuel flow path for routing fuel to the combustor of the core engine, an engine start system that includes a first stage that generates a first quantity of thermal energy for heating a first portion of fuel and a second stage that utilizes the heated first portion of fuel to generate a second quantity of thermal energy for heating a second portion of fuel, the second quantity of thermal energy is greater than the first quantity of thermal energy and the second portion of fuel is communicated to the core engine.