The purpose of this paper is to present an acoustics-based method for measuring turbofan nozzle exhaust thrust, while assessing the potential of scaling the methods for in-flight measurements.
Although many methods proposed for achieving in-flight thrust measurements involve complicated, sensitive and expense instruments, an acoustics-based approach is discussed that greatly simplifies the technology development pathway to in-flight applications.
Results are provided for a minimum set of sensors applied in the exhaust of a research turbofan engine at Virginia Tech, showing the difference in acoustics-measured thrust and nozzle thrust found by integrating thermocouple and Kiel probe measurements to be less than 6 per cent at the maximum fan speed examined.
Measuring accurate thrust values in flight will prove immediately valuable for installed thrust validation and engine health monitoring. Acoustics-based methodologies are attractive because of the robustness and low cost of sensors and sources. The value of in-flight thrust measurements, along with the benefits of acoustic approaches, makes the current topic of great interest for further development.
This paper presents unique applications of a time-of-flight acoustic thrust sensor, while providing an original assessment of technological challenges involved with the progression of the technique for in-flight measurements.
