Modern commercial aircraft rely on powerful turbofan engines to provide the high thrust needed to get airborne and travel long distances economically. Thrust is a result of the engine’s ability to efficiently breath in air, compress it, and burn fuel. This process produces high-temperature pressurized gas that expands through the engine. The high-speed rush of hot air spins the engine’s turbines, which extract energy from the gas stream to power the compressor, and the gas expands rearward in the engine to produce the thrust that propels the jet forward.
With all this activity, it’s no surprise that engine cores are hostile environments where high temperatures and pressures exist that require continuous monitoring by the engine controller. Having reliable engine core data is critical for the engine to maintain desired operating conditions while monitoring engine combustion and compressor stability.
Current engine pressure monitoring systems work around the harsh conditions inside the engine’s core by obtaining pressure data using sensors mounted outside of the core on the engine fan casing. With the current technology, real-time, close-coupled core pressure measurement simply cannot be reliably achieved. Striving to advance aircraft engine pressure monitoring, the Fluid Systems Division of Parker Aerospace has entered into an exclusive technology license agreement with Oxsensis Ltd., a manufacturer of optical sensors used in harsh environments, to develop a unique optical-based system that can be installed on the engine’s core to deliver true, next-generation engine pressure monitoring capabilities for tomorrow’s aircraft.
Current monitoring approach: relying on transducers located away from the data source
Currently, aircraft engine pressure measurement is accomplished through the use of electrical pressure transducers, such as silicon-based micro-electromechanical systems (MEMS). The transducers measure pressure and convert it into an electrical signal that is interpreted and transmitted to the engine controller. The pressure transducers reside in a single manifold block, typically located in a relatively cool location on the engine fan casing to avoid being damaged by the high temperatures occurring inside the engine core where the data must be collected.
The transducers sense engine pressure data via thin, air-filled pipes – or sense lines – routed to pressure ports on the engine core wall. The transducers measure pressure variations in the sense lines, which follow the pressure variations in the core. However, the long, air-filled pipes introduce errors and changes to the pressure signal dynamics, meaning that the measured data does not provide the controller with a high-fidelity representation of what is happening inside the engine core. In addition to providing less-than-optimal data, the sense lines have the potential to gather humidity and form ice during flight, causing operational disruption.
New optical gas turbine sensors provide a higher-fidelity way to measure engine pressure inside the engine core
The latest collaboration between Parker Aerospace and Oxsensis will deliver the next-generation engine pressure monitoring system that uses passive, optical pressure sensors that can be directly mounted in the engine core to provide true and real-time engine pressure information. An interrogator is mounted on the fan casing and uses optical fibers to provide optical energy to the sensors and analyze their reflected light as absolute pressure, time-varying pressure term, and sensor head temperature.
The concept is similar to both companies’ joint silica-based optical high-accuracy pressure sensor (SOHAPS) systems being actively developed as a major advancement in aircraft fuel quantity measurement.
“When investigating new technologies, Parker Aerospace looks at the implications a shift will have on aircraft years from now. We also look for opportunities to partner with other leading companies that bring unique capabilities and excitement to shared projects. Working with Oxsensis to deliver our optical-based direct engine pressure measurement solution to market in this decade demonstrates a mutual commitment to advance aircraft engine monitoring.”
– Dr. Lewis Boyd, principal investigator of fuel gauging and sensors, Parker Aerospace Fluid Systems Division
Significant benefits over MEMS
Using optical sensors that perform direct measurement in an engine’s core results in significant benefits that current engine pressure monitoring systems cannot deliver, including:
- Withstanding harsh, high-temperature conditions, gas turbine optical sensors eliminate the need for sense lines.
- Eliminating the need for sense lines removes the associated scheduled maintenance costs and failure modes that cause disruptions.
- By generating higher fidelity measurements, engine controllers can operate aircraft engines closer to their limits, resulting in better fuel-burn efficiency.
- Direct engine core measurement enables monitoring of unsteady pressures in the core, improving the time before overhaul.
- Using fiber optics results in a system that is immune to EMI while offering reduced installation costs and system weight.
The future is now
Parker Aerospace expects the new engine pressure monitoring system to be fully tested and ready for service by the mid-2020s to support the next generation of engines powering business jets and commercial aircraft.
This innovative technology has the potential to be applied to other aircraft engine applications as well. Optical sensors can be used to monitor engine exit temperatures to better inform engine controllers of engine performance and health, enabling more efficient engine operations and signaling a shift from current thermocouple-based measuring systems that can “drift” and provide inaccurate information over time.
Optical sensors can improve the accuracy of systems that require pressure and volume measurement such as engine oil lubrication systems, presenting an opportunity for optical sensors to replace current methods. Parker is investigating these and future possibilities as part of our ongoing commitment to customer success.
To learn more about Parker’s involvement in optical-based sensors for aircraft engine measurement and monitoring, contact the Parker Aerospace Fluid Systems Division at +1 (949) 851-3500.
This post was contributed by Dr. Lewis Boyd, principal investigator of fuel gauging and sensors, Parker Aerospace Fluid Systems Division.