Nonintrusive systems for the measurement on test rigs of aeroengine exhaust emissions required for engine certification (CO, NO(x), total unburned hydrocarbon, and smoke), together with CO(2) and temperature have been developed. These results have been compared with current certified intrusive measurements on an engine test. A spectroscopic database and data-analysis software has been developed to enable Fourier-transform Infrared measurement of concentrations of molecular species. CO(2), CO, and NO data showed agreement with intrusive techniques of approximately ?30%. A narrow-band spectroscopic device was used to measure CO(2) (with deviations of less than ?10% from the intrusive measurement), whereas laser-induced incandescence was used to measure particles. Future improvements to allow for the commercial use of the nonintrusive systems have been identified and the methods are applicable to any measurement of combustion emissions.
A procedure to calibrate a Fourier transform spectrometer is presented. Blackbody sources of three different temperatures are used to eliminate errors in the calibration that result from the limited accuracy of the temperature measurement of the calibration sources. With three spectra of blackbodies it is possible to assume that the temperatures are unknown variables as are the parameters of the functions that describe the spectrometer. A nonlinear Gaussian balancing calculation is used to determine these unknown variables and to minimize the influence of noise. A comparison between the results obtained with this method and a conventional calibration procedure is presented.
Ground-based high spectral resolution measurements of downwelling radiances from 800 to 1200 cm −1 were conducted between 20 January and 6 February 2008 within the scope of the SAMUM-2 field experiment. We infer the spectral signature of mixed biomass burning/mineral dust aerosols at the surface from these measurements and at top of the atmosphere from IASI observations. In a case study for a day characterized by the presence of high loads of both dust and biomass we attempt a closure with radiative transfer simulations assuming spherical particles. A detailed sensitivity analysis is performed to investigate the effect of uncertainties in the measurements ingested into the simulation on the simulated radiances. Distinct deviations between modelled and observed radiances are limited to a spectral region characterized by resonance bands in the refractive index. A comparison with results obtained during recent laboratory studies and field experiments reveals, that the deviations could be caused by the aerosol particles' non-sphericity, although an unequivocal discrimination from measurement uncertainties is not possible. Based on radiative transfer simulations we estimate the aerosol's direct radiative effect in the atmospheric window region to be 8 W m −2 at the surface and 1 W m −2 at top of the atmosphere.
Abstract. Emission indices were derived from in-flight measurements of CO, nonmethane hydrocarbons (NMHCs), H20 , and nonvolatile condensation nuclei in the exhaust plumes of the Deutsches Zentrum far Luft-und Raumfahrt VFW 614 (ATTAS) and NASA DC-8 experimental aircraft. CO emission indices, EIs(CO), of the ATTAS Rolls Royce M 45H Mk501 engines were determined concurrently by two independent techniques: monitoring of exhaust emissions using a customized Fourier transform infrared spectrometer (FTIR) and by simultaneous continuous fast CO and CO2 measurements. The EIs(CO) determined by FTIR were systematically 28% lower than those derived from the CO/CO2 concentration ratios. The EIs(CO) of the newer and larger CFM 56-2C1 engines, used on DC-8, were substantially smaller than those of the ATTAS engines. The emission behavior of CFM 56-2C1 engines is very similar to CFM 56-3 engines frequently used on Boeing 737 aircraft. In-flight derived EIs(CO) of the ATTAS engines were strongly dependent on the fuel flow rate and agreed well with those calculated from ground-based measurements. Emission indices for individual NMHCs were determined from the concentration ratios of NMHC/CO in the plume of ATTAS and DC-8 and from the EIs(CO) determined by FTIR or derived from the concentration ratios of CO/CO2. The EIs(NMHC) are highest for alkenes and alkynes generated by a cracking of larger fuel molecules and for benzene from unburnt fuel, and they depend strongly on the power setting of the engines. As with EIs(CO), the EIs(NMHC) of the CFM 56-2C1 engine tend to be smaller than those of the Rolls Royce M 45H Mk501.
A customized Fourier transform infrared spectrometer on board an aircraft performs in-flight measurements of the jet engine's exhaust emissions. For this purpose the instrument is mounted in the aircraft's cabin receiving infrared radiation emitted by the hot jet about 1 rn downstream from the nozzle exit. From the measured infrared spectra the concentrations and emission indices of the gas species NO, CO, H:O, and CO: and the gas temperature are calculated. The estimated accuracy of the measurements is in the range of 5 to 20%. The results reveal the high precision of the acquired data which are compared to model calculations. Different methods have been developed in the past to measure emission indices at cruise altitudes for NOx and most of the other exhaust components. They can be divided into two categories: The first method is to measure directly in the exhaust plumes of aircrafts, often guided by visible contrails. This is performed by chasing selected airliners [Arnold et al., 1992] or crossing the own flight path [Fahey et al., 19954, b]. The latter procedure benefits from the exact knowledge of all flight, engine, and fuel parameters. Data from different plume ages in the vortex and dispersion regimes are collected. As a second strategy, the immissions at cruise altitudes are determined by measuring at frequently used flight levels in areas with high traffic density (e.g., the North Atlantic corridor). This is realized either by traversing the flight tracks [Schlager et al., 1994] or by observations along the flight corridors [Brunner et al., 1994; Marenco et al., 1994]. For the first time the presented system uses a third strategy. The emissions are measured by means of a remote sensing arrangement. Contrary to in situ methods, no sampling of gas probes is necessary. The hot gas components are detected by a spectrometer as described in the following. In a first phase the instrument observes the exhaust of the aircraft's own jet engines [Haschberget, 1994b]. Detailed information on the emissions as functions of different flight and engine parameters can be obtained as all relevant data are available and may be varied on demand. Observation time which is often a problem for in situ instruments can be extended until the signal-to-noise ratio is satisfactory. This paper gives an overview of the developed measurement system, that is, the customized Fourier transform spectrometer, the data evaluation procedure (calculation of gas concentrations and emission indices from measured infrared spectra), and the first quantitative results from a measurement campaign. The realized setup as well as the application (spectrometric in-flight measurement and quantitative analysis of aircraft exhaust) is unique although similar proposals were made by other groups recently [Arnold et al., 1995]. 25,995 25,996 HASCHBERGER AND LINDERMEIR: AIRCRAFT EXHAUST EMISSIONS
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