We report here the first implementation of chemically specific imaging in the exhaust plume of a gas turbine typical of those used for propulsion in commercial aircraft. The method used is chemical species tomography (CST) and the target species is CO2, absorbing in the near-infrared at 1999.4 nm. A total of 126 beams propagate transverse to the plume axis, along 7 m paths in a coplanar geometry, to probe a central region of diameter ≈1.5m. The CO2 absorption spectrum is measured using tunable diode laser spectroscopy with wavelength modulation, using the second harmonic to first harmonic (2f/1f) ratio method. The engine is operated over the full range of thrust, while data are recorded in a quasi-simultaneous mode at frame rates of 1.25 and 0.3125 Hz. Various data inversion methodologies are considered and presented for image reconstruction. At all thrust levels a persistent ring structure of high CO2 concentration is observed in the central region of the measurement plane, with a raised region in the middle of the plume assumed to be due to the engine's boat tail. With its potential to target various exhaust species, the CST method outlined here offers a new approach to turbine combustion research, turbine engine development, and aviation fuel research and development.

COUNTERFOG® has been proposed as a rapid decontamination and disinfection technology that uses dynamic submicrometric-disinfecting fog cones. When projected onto surfaces, they create a micrometre-thick film of disinfectant minimizing the use of liquids and the impact on environment. The extremely thin film is intended to be enough to cover and kill microorganisms and simultaneously thin enough to evaporate in a few minutes—depending on the environmental conditions. In the present work, experimental tests were carried out to verify this hypothesis. These include a physical characterization of the fog in the cone, a measurement of the liquid flow projected on surfaces as well as disinfection tests with a series of microorganisms. In addition to these results, operational recommendations are derived to ensure disinfection reliability.

Very high bypass ratio (VHBR) engines will realize significant environmental benefits as lower fuel consumption contributes to a reduction in CO2, NOx and non-volatile particulate matter (nvPM)/soot emission. VHBR engine performance tests will require representative CO2 measurement, and here we propose the use of a chemical species tomography (CST) measurement system to fully map the output CO2 from the engine core exhaust. In addition, we propose a technique allowing the 2D measurement of exhaust nvPM concentration that will provide an increased understanding of the complex injector-to-injector fuel flow variation, which impacts the temperature distribution through the turbine. This combined technological development in the CIDAR programme will produce an innovative step change in aircraft engine diagnostics, based on real-time, in-situ photonic technologies. This will increase the EU’s competitiveness in non-intrusive engine exhaust measurement systems for both engine performance evaluation and emissions quantification.

Quantification of aero-engine emission is typically carried out using etfractive sampling resulting in poor spatio-temporal resolution. Here we present recent images obtained using non-intrusive chemical species tomography on a large-scale commercial aero-engine.

Emissions from aircraft have adverse effects on the air quality in and around airports, contributing to public health concerns within neighbouring communities. AVIATOR will adopt a multi-level measurement, modelling and assessment approach to develop an improved description and quantification of the relevant aircraft engine emissions, and their impact on air quality under different climatic conditions. Particulate and gaseous emissions in a test cell and on-wing from an in-service aircraft will be measured to determine pollutant plume evolution from the engine and APU exhaust. This will provide an enhanced understanding of primary emitted pollutants, specifically the nvPM and vPM (down to 10nm), and the scalability between the regulatory test cell and real environments. AVIATOR will develop and deploy a proof-of-concept low cost sensor network for monitoring UFP, PM and gaseous species across multiple airports and surrounding communities. Campaigns will be complemented by high-fidelity modelling of aircraft exhaust dynamics, microphysical and chemical processes within the plume. CFD, box, and airport air quality models will be applied, providing validated parameterisations of the relevant processes, applicable to standard dispersion modelling on the local scale. Working with the regulatory community, AVIATOR will develop improved guidance on measuring and modelling the impact of aircraft emissions, and will provide airports and regulators with tools and guidance to improve the assessment of air quality in and around airports.

We report on the installation and commissioning of two systems for the measurement of cross-sectional distributions of pollutant species in jet exhaust, within the engine ground test facility at INTA, Madrid. These systems use optical tomography techniques to estimate the cross-sectional distributions of CO2 and soot immediately behind the engine. The systems are designed to accommodate the largest civil aviation engines currently in service, without obstruction of the exhaust or bypass flows and with negligible effect upon the entrained flow behavior. We describe the physical construction and installation status of each system. In the case of the CO2 system, we examine the challenges of achieving the structural rigidity necessary for adequate suppression of pointing error within 126 laser-based transmittance measurements, each utilizing a 7 m overall path length. We describe methods developed for efficient implementation of co-planarity and 4-degree- of-freedom alignment of individual paths within this beam array. We also present laboratory performance data for three alternative optical designs that differ in their approach to the management of pointing error and turbulence-induced beam wander and spread. The FLITES soot monitoring capability is based on laser induced incandescence (LII) and uses a short-pulse fiber laser and two CCD cameras, in an autoprojection arrangement. We describe the measurement geometry currently being implemented in the test cell and discuss optical design issues, including once again the effect of the plume itself.

We present a tomographic system tailored to the measurement and study of aero-engine plume dynamics, exhaust chemistry and novel engine or fuel design. This aims to address aviation pollutant emission reductions. As the testing environment is not ideal for instrumentation and must not interfere with the operation or air flow of the engine, this data acquisition (DAQ) system utilises tunable-diode laser absorption spectroscopy (TDLAS) with wavelength modulation. Dithering increases SNR despite plume scintillation, but prompts exploration of accurate, at detector, real-time, digital lock-in (DLI) techniques. The readout options are restricted, forcing a custom, distributed architecture, embedded microprocessor control and Ethernet connectivity. The multi-channel chemical species tomography (CST) electronics performs simultaneous detection and is scalable for increased numbers of beams, sample rates and laser dither rates. The system uses 12 digitisation hubs around the imaging space, each with 16 parallel channels. These operate at 40MS/s, 14bit, giving a system capacity of 192 channels and input rates exceeding 107Gbit/s. To meet the future needs of spectroscopy, gas species or beam extensions, the diagnostic tool allows software control over many signal processing and acquisition parameters. This paper presents the design of the DAQ system through the entire custom electrical signal chain. Results are presented for a data interleaving approach aimed at reducing the impact of network packet loss when using UDP Ethernet protocols and high network utilisation. We also present gain and bandwidth results for all 192 analogue front-end circuits on the DAQ hubs, along with preliminary results for the optical detector and pre-amplifier circuits.

The complexity of Very High Bypass Ratio (VHBR) lean burn combustion systems requires careful fuel control and optimised staging to minimise non-volatile particulate matter (nvPM) emissions. Fuel flow variation across injectors will impact the temperature distribution through the turbine and thus influences rates of nvPM formation and consumption. Through Clean Sky 2, Rolls-Royce are developing technologies required for VHBR engines. CIDAR (Combustion species Imaging Diagnostics for Aero-Engine Research) supports this initiative.