Measurement of black carbon emissions from multiple engine and source types using laser-induced incandescence: Sensitivity to laser fluence

A new regulatory standard for non-volatile particulate matter (nvPM) mass concentration emissions from aircraft engines has been adopted by the International Civil Aviation Organisation. One of the instruments used for the regulatory nvPM mass emissions measurements in aircraft engine certification tests is the Artium Technologies LII 300, which is based on laser-induced incandescence. The LII 300 has been shown in some cases to demonstrate a variation in response to the type of black carbon particle measured. Hence it is important to identify a suitable black carbon emission source for instrument calibration. In this study, the relationship between the nvPM emissions produced by different engine sources and the response of the LII 300 instrument utilising auto-compensating laser-induced incandescence (AC-LII) method was investigated. Six different sources were used, including a turboshaft helicopter engine, a diesel generator, an intermediate pressure test rig of a single sector combustor, an auxiliary power unit gas turbine engine, a medium-sized diesel engine, and a downsized turbocharged direct injection gasoline engine. Optimum LII 300 laser fluence levels were determined for each source and operating condition evaluated. It was found that an optimised laser fluence can be valid for real-time measurements from a variety of sources, where the mass concentration was independent of laser fluence levels covering the typical operating ranges for the various sources. However, it is important to perform laser fluence sweeps to determine the optimum fluence range, as differences were observed in the laser fluence required, between sources and fuels. We discuss the measurement merits, variability, and best practices in the real-time quantification of nvPM mass concentration using the LII 300 instrument, and compare that with other diagnostic techniques, namely absorption–based methods such as photoacoustic spectroscopy using a photoacoustic extinctiometer (PAX) and a Micro Soot Sensor (MSS), and thermal-optical analysis (TOA). Particle size distributions were also measured using a scanning mobility particle sizer (SMPS). Overall, the LII 300 provides robust and consistent results when compared with the other diagnostic techniques across multiple engine sources and fuels. The results https://doi.org/10.5194/amt-2021-209 Preprint. from this study will inform the development of updated calibration protocols to ensure repeatable and reproducible measurements of nvPM mass emissions from aircraft engines using the LII 300

Rapid assessment of jet engine-like soot from combustion of conventional and sustainable aviation fuels using flame spray pyrolysis

Black carbon, or soot, is one of the highest contributors to global warming. The International Civil Aviation Organization (ICAO) has adopted regulatory standards for soot from aircraft engines, also referred to as a nonvolatile particulate matter (nvPM), to limit or reduce the harmful impacts of nvPM on the environment. Sustainable aviation fuels (SAF) offer advantages to reduce soot emissions and overall environmental impact but require extensive testing and evaluation before wider adoption. Typical measurements of soot produced by combustion of aviation fuels require full-sized jet engines and large volumes of fuel, which can be prohibitively expensive. This study investigates flame spray pyrolysis (FSP) as a simple bench-top tool for comparison of soot emissions from the combustion of different liquid jet fuels. A sampling assembly is designed for soot collection and analysis. Morphological analysis follows from transmission electron microscopy (TEM) image analysis and mobility (differential mobility analyzer) classification. Morphologies are compared to previous measurements from aircraft turbines. Soot agglomerate size distributions and elemental to total carbon ratios (EC/TC) are measured for three liquid fuels and flame conditions with Reynolds numbers and burner equivalence ratios ranging from 6100 to 9100 and 7 to 13, respectively. Day-to-day variations in the dilution ratio resulted in up to 20% variability in the measured total agglomerate number-based concentration and mobility diameter. Geometric mean primary particle and mobility diameter values are below 21 and 104 nm, respectively, in excellent agreement with those emitted from jet engines and prior work using FSP. EC/TC remains >0.75 for most flame conditions and fuels and increases with burner equivalence ratio, but values as low as 0.63 are measured from SAF combustion. Copyright © 2024 American Association for Aerosol Research</p

Response of real-time black carbon mass instruments to mini-CAST soot

<p>Soot is a climate forcer and a dangerous air pollutant that has been increasingly regulated. In aviation, regulatory measurements of soot mass concentration in the exhaust of aircraft turbine engines are to be based on measurements of black carbon (BC) calibrated to elemental carbon (EC) content of diffusion flame soot. The calibration soot must currently meet only one criterion: minimum EC to total carbon (TC) ratio of 0.8. However, not including soot properties other than the EC/TC ratio may potentially lead to discrepancies between different BC measurements. We studied the response of two instruments, the AVL Micro-Soot Sensor (MSS) and the Artium Laser-Induced Incandescence 300 (LII), to soot from two miniature combustion aerosol standard (mini-CAST) burners. By changing the air-fuel ratio, premixing nitrogen into the fuel, and using a catalytic stripper to remove volatile compounds, we produced a wide range of particle morphologies and EC contents. As the EC content decreased, both the instruments underreported the EC mass, but the LII diverged more severely. Upon closer investigation of eight conditions with EC/TC > 0.8, the LII underreporting was found independent of primary particle size, but increased with decreasing geometric mean diameter of the soot agglomerates. As the geometric mean diameter decreased from 160 nm to 50 nm, the differences between the LII and MSS increased from 15% to 50%. The results suggest that in addition to EC content, calibration procedures for the regulatory BC measurements may need to take particle size distributions into account.</p> <p>© 2016 American Association for Aerosol Research</p

Impact of Alternative Fuels on Emissions Characteristics of a Gas Turbine Engine – Part 2: Volatile and Semivolatile Particulate Matter Emissions

The work characterizes the changes in volatile and semivolatile PM emissions from a gas turbine engine resulting from burning alternative fuels, specifically gas-to-liquid (GTL), coal-to-liquid (CTL), a blend of Jet A-1 and GTL, biodiesel, and diesel, to the standard Jet A-1. The data presented here, compares the mass spectral fingerprints of the different fuels as measured by the Aerodyne high resolution time-of-flight aerosol mass spectrometer. There were three sample points, two at the exhaust exit plane with dilution added at different locations and another probe located 10 m downstream. For emissions measured at the downstream probe when the engine was operating at high power, all fuels produced chemically similar organic PM, dominated by C_<i>x</i>H_<i>y</i> fragments, suggesting the presence of long chain alkanes. The second largest contribution came from C_<i>x</i>H_<i>y</i>O_<i>z</i> fragments, possibly from carbonyls or alcohols. For the nondiesel fuels, the highest loadings of organic PM were from the downstream probe at high power. Conversely, the diesel based fuels produced more organic material at low power from one of the exit plane probes. Differences in the composition of the PM for certain fuels were observed as the engine power decreased to idle and the measurements were made closer to the exit plane

Impact of Alternative Fuels on Emissions Characteristics of a Gas Turbine Engine – Part 1: Gaseous and Particulate Matter Emissions

Growing concern over emissions from increased airport operations has resulted in a need to assess the impact of aviation related activities on local air quality in and around airports, and to develop strategies to mitigate these effects. One such strategy being investigated is the use of alternative fuels in aircraft engines and auxiliary power units (APUs) as a means to diversify fuel supplies and reduce emissions. This paper summarizes the results of a study to characterize the emissions of an APU, a small gas turbine engine, burning conventional Jet A-1, a fully synthetic jet fuel, and other alternative fuels with varying compositions. Gas phase emissions were measured at the engine exit plane while PM emissions were recorded at the exit plane as well as 10 m downstream of the engine. Five percent reduction in NO<i>_x</i> emissions and 5–10% reduction in CO emissions were observed for the alternative fuels. Significant reductions in PM emissions at the engine exit plane were achieved with the alternative fuels. However, as the exhaust plume expanded and cooled, organic species were found to condense on the PM. This increase in organic PM elevated the PM mass but had little impact on PM number