Geared Turbine Thrust Measurement via Annulus Gear Force
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Solution Overview
Problem
Current methods for measuring the thrust of geared gas turbine engines are inaccurate due to the dependence on engine pressure ratio and turbofan power ratio, which can lead to errors in thrust setting, especially with engine deterioration affecting the low-pressure system and air system.
Innovation Solution
An apparatus and method using force sensors, rotational speed sensors, and a processor to measure the force applied by the annulus gear and planet carrier on a static structure, determining the restoring torque and torque applied to the fan, allowing for precise calculation of thrust based on rotational speeds of the core and fan shafts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If engine pressure ratio (EPR) is used to control thrust setting, then thrust control is simplified, but measurement errors lead to unacceptable thrust setting accuracy
Solution Approach 1:
The patent replaces the traditional pressure-based measurement system (EPR) with a direct force measurement system using load cells. The load cells are integrated into the exhaust nozzle structure to directly measure the thrust force, substituting indirect pressure ratio measurements with direct mechanical force measurement, thereby eliminating the accumulation of errors from multiple pressure sensors and calculations.
Solution Approach 2:
The patent introduces load cells as intermediary elements between the exhaust nozzle and the engine structure. These load cells act as mediators that directly sense the thrust force generated by the engine and transmit this information to the control system, providing an accurate intermediate measurement that bridges the gap between engine operation and thrust output.
2Measurement precision
If turbofan power ratio (TPR) is used for high bypass ratio engines, then thrust control is improved, but deterioration of low pressure system and air system affects accuracy
Solution Approach 1:
The patent replaces the complex TPR calculation system (which depends on multiple rotating component parameters) with a direct force measurement system. The load cells directly measure thrust without relying on the rotational speeds or conditions of the low pressure turbine, compressor, or air system, making the measurement immune to deterioration of these systems.
Solution Approach 2:
The patent extracts the thrust measurement function from the rotating engine components (turbine, compressor, shafts) and relocates it to the stationary exhaust nozzle structure. By taking out the measurement function from the deteriorating rotating systems and placing it in the stable nozzle structure, the measurement becomes independent of component deterioration.
3Measurement precision
If direct force measurement is implemented in the exhaust nozzle, then thrust measurement accuracy is improved, but device complexity increases
Solution Approach 1:
The patent merges the thrust measurement function with the existing exhaust nozzle structure. The load cells are integrated into the nozzle assembly, combining the propulsive function of the nozzle with the measurement function of the load cells. This merging eliminates the need for separate measurement equipment and reduces overall system complexity.
Solution Approach 2:
The exhaust nozzle structure is given dual functionality: it serves both as a propulsive component and as a mounting structure for the thrust measurement system. The load cells mounted on the nozzle serve the universal purpose of both supporting the nozzle structure and measuring the thrust force, reducing the need for dedicated measurement hardware.
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 approach provides accurate thrust measurement and control, reducing errors associated with engine deterioration and improving thrust setting precision in geared gas turbine engines.
Implementation Method 1
at least one force sensor to measure the force applied by the other one of the annulus gear and the planet carrier on the static structure
Implementation Method 2
a first rotational speed sensor arranged to measure the rotational speed of the core shaft, a second rotational speed sensor arranged to measure the rotational speed of the fan shaft
Implementation Method 3
the processor being arranged to determine the restoring torque on the other one of the annulus gear and the planet carrier from the measurement of the force applied by the other one of the annulus gear and the planet carrier on the static structure
Implementation Method 4
a gearbox that receives an input from the core shaft and outputs drive to the fan shaft so as to drive the fan at a lower rotational speed than the core shaft
Implementation Method 5
the core shaft being arranged to drive the sun gear and one of the planet carrier and the annulus gear being arranged to drive the fan via a fan shaft
Data Source
Figure 1~2
Figure 3~4
Figure 5~6
AI summary
An apparatus (50) for measuring the thrust of an aircraft gas turbine engine (10) comprising a core shaft (26) connecting a turbine (19) to a compressor (14), a fan (23) and a gearbox (30) comprising a sun gear (28), a plurality of planet gears (32), an annulus gear (38) and a planet carrier (34). The core shaft (26) drives the sun gear (28) and the planet carrier (34) drives the fan (23) via a fan shaft (25). The annulus gear (38) is mounted in a static structure (24, 40). The apparatus (50) comprises a force sensor (52) to measure the force applied by the annulus gear (38) on the static structure (24, 40), a first rotational speed sensor (54) to measure the rotational speed of the core shaft (26), a second rotational speed sensor (56) to measure the rotational speed of the fan shaft (25). A processor (58) is arranged to determine the restoring torque on the annulus gear (38) from the measurement of the force applied by the annulus gear (38) on the static structure (24, 40). The processor (58) is arranged to determine the torque applied to the fan (23) by the planet carrier (34) using the rotational speed of the core shaft (26), the rotational speed of the fan shaft (25) and the restoring torque on the annulus gear (38). The processor (58) is arranged to determine the thrust of the fan (23) from the torque applied to the fan (23) and the rotational speed of the fan (23).