Boost Spool Gas Turbine Engine Cruise Efficiency
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Solution Overview
Problem
Gas turbine engines face efficiency limitations due to restricted overall pressure ratio (OPR) to prevent temperature exceedance, which reduces performance during cruise power operations while maintaining thermal limits, especially under varying ambient conditions.
Innovation Solution
Incorporating a boost spool that can be selectively engaged to increase OPR during cruise power, allowing the engine to operate within thermal limits and enhance efficiency by compressing air downstream of the last compressor stage and directing it to the boost spool inlet, thereby increasing the engine's OPR from 40 to 75.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If OPR is increased to improve thermodynamic efficiency and reduce fuel consumption, then engine efficiency improves, but turbine temperatures exceed permissible material and structural limits
Solution Approach 1:
The compression system is segmented into two independent parts: the main compressor and the boost spool compressor. This allows the boost spool to provide additional compression during cruise conditions without increasing the temperature in the main compressor section beyond material limits, thereby enabling higher OPR for improved efficiency while maintaining thermal safety.
Solution Approach 2:
The boost spool acts as an intermediary compression device that receives air from the main compressor and provides additional compression. This intermediary system enables the engine to achieve higher overall pressure ratios during cruise without subjecting the primary compressor and turbine to temperatures that would exceed material limits.
2Reliability
If OPR is limited to maintain acceptable turbine temperatures for hot day takeoff, then thermal limits are maintained, but engine efficiency is reduced during cruise power operations
Solution Approach 1:
The boost spool is dynamically engaged during cruise power operations and disengaged during takeoff operations. This dynamic configuration allows the engine to optimize OPR for each operating condition: maintaining thermal compliance during takeoff while achieving high efficiency during cruise, thereby resolving the contradiction between reliability and energy efficiency.
Solution Approach 2:
The system changes the operating parameters (OPR) based on flight conditions by selectively engaging the boost spool. During cruise, the boost spool increases OPR to improve efficiency; during hot day takeoff, the boost spool remains disengaged to maintain acceptable turbine temperatures, thus adapting parameters to resolve the contradiction between thermal compliance and efficiency.
3Use of energy by moving object
If a boost spool is added to increase OPR during cruise, then engine efficiency improves, but device complexity increases
Solution Approach 1:
The boost spool is designed to serve multiple functions: it provides additional compression during cruise to improve efficiency, can be disengaged during takeoff to maintain thermal compliance, and integrates with the existing compressor system. This multi-functionality justifies the added complexity by delivering multiple benefits from a single added component.
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
This solution enables the gas turbine engine to maintain acceptable turbine temperatures during takeoff while achieving higher OPR at cruise, improving thrust specific fuel consumption and overall engine efficiency without exceeding thermal limits.
Implementation Method 1
a boost spool that can be selectively engaged to increase OPR during cruise power, allowing the engine to operate within thermal limits and enhance efficiency by compressing air downstream of the last compressor stage
Data Source
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AI summary
A gas turbine engine (10) includes a first spool (14,16), a second spool (12), a primary combustor (70), and a diffuser (68). The first spool (14,16) includes a first compressor (18,24) rotationally driven by a first turbine (20,26) via a first shaft (22,28). The second spool (12) includes a second compressor (74) driven by a second turbine (76) via a second shaft (78). The first compressor (18,24), the diffuser (68), and the primary combustor (70) are arranged in series to provide a compressed airflow discharged from the first compressor (18,24) to the primary combustor (70) via the diffuser (68), which includes walls that diverge towards the primary combustor (70). The second compressor (74) is fluidly coupled to the diffuser (68) to receive at least a portion of the compressed airflow from the diffuser (68). The second turbine (76) is fluidly coupled to the diffuser (68) to discharge an expanded airflow to the diffuser (68).