Peter Haschberger

Nonintrusive optical measurements of aircraft engine exhaust emissions and comparison with standard intrusive techniques

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.

Laser-Induced Chlorophyll Fluorescence Measurements for Detecting the Nitrogen Status of Wheat (Triticum aestivum L.) Canopies

Abstract.The objective of this study was to assess the suitability of laser-induced chlorophyll fluorescence measurements to detect the nitrogen (N) supply of wheat (Triticum aestivum L.) at canopy level under ambient conditions. In 2002, a plot trial was carried out as a randomised block design. Increasing amounts of N fertiliser were applied to induce variations in the N uptake of the canopies. Different cultivars with varying growth habit and leaf colour were chosen to cover a wide range of canopy characteristics. Biomass was harvested at characteristic growth stages to determine aboveground dry matter yield, N concentration in dry matter and N uptake. Measurements with a hand-held chlorophyll sensor showed a strong correlation between the sensor signal and the N uptake thus indicating that the system is suitable for assessing the nutritional status of the plants. A clear differentiation between the N treatments was evident even at the beginning of stem elongation. The cultivar and the growth stage significantly influenced the sensor signal. Both factors need to be considered when predicting the N uptake of the canopy using laser-induced chlorophyll fluorescence measurements.

In-flight measurement of aircraft non-methane hydrocarbon emission indices

Concentrations of non-methane hydrocarbons (NMHC) and CO were measured in exhaust plumes of the DLR experimental aircraft ATTAS equipped with Rolls Royce M 45H Mk501 engines. The emission indices (EI) of individual light NMHC were determined from ratios of NMHC and CO concentration enhancements measured in grab samples and the concurrent in-flight measurements of EI of CO by FTIR emission spectroscopy. Alkenes and alkynes generated by cracking of larger NMHC molecules and aromatic compounds originating from unburnt fuel constituted a larger and a smaller fraction of the NMHC emissions, respectively.

Optimization of a Michelson interferometer with a rotating retroreflector in optical design, spectral resolution, and optical throughput

A newly designed Michelson interferometer for Fourier spectroscopy [ J. Opt. Soc. Am. A8, 1991 ( 1991)] utilizes a nutating retroreflector (cube corner mirror) to generate alterations in geometrical and optical paths. The practical optomechanical design of a Fourier-transform spectrometer incorporating a rotating retroreflector for path-length alteration is considered. [The instrument has been given the name MIROR, for Michelson Interferometer with a Rotating Retroreflector.] Two parameters of the instrument are essential: the maximum optical path difference, which yields the spectral resolution of the instrument, and the diameter of the transmitted beam, which determines the throughput and hence the achievable signal-to-noise ratio. The maximum allowable beam diameter is calculated as a function of the geometry and the orientation of the rotating retroreflector and the other optical components. The geometrical configuration and the orientation of all the optical components with respect to one another are also optimized for the maximum transmitted beam diameter when the required path difference is given. A principal investigation of different possible configurations of the optical components is presented. Then a quantitative optimization for an interferometer employing a retroreflector having a 5-in. (12.7-cm) aperture diameter requiring an optical path difference of more than 10 cm (spectral resolution better than 0.1 cm−1) is performed. Finally a simplified but enhanced design is described.

ARES: A new reflective / emissive Imaging Spectrometer for Terrestrial Applications

A new airborne imaging spectrometer introduced: the ARES (Airborne Reflective Emissive Spectrometer) to be built by Integrated Spectronics, Sydney, Australia, financed by DLR German Aerospace Center and the GFZ GeoResearch Center Potsdam, Germany, and will be available to the scientific community from 2003/2004 on. The ARES sensor will provide 160 channels in the solar reflective region (0.45-2.45 μm) and the thermal region (8-13 μm). It will consists of two separate coregistered optical systems for the reflective and thermal part of the spectrum. The spectral resolution is intended to be between 12 and 15 nm in the solar wavelength range and should reach 150nm in the thermal. ARES will be used mainly for environmental applications in terrestrial ecosystems. The thematic focus is thought to be on soil sciences, geology, agriculture and forestry. Limnologic applications should be possible but will not play a key role in the thematic applications. For all above mentioned key application scenarios the spectral response of soils, rocks, and vegetation as well as their mixtures contain the valuable information to be extracted and quantified. The radiometric requirements for the instrument have been modelled based on realistic application scenarios and account for the most demanding requirements of the three application fields: a spectral bandwidth of 15 nm in the 0.45-1.8 μm region, and 12 nm in the 2 - 2.45 μm region. The required noise equivalent radiance is 0.005, 0.003, and 0.003 mWcm-2sr-1μm-1 for the spectral regions 0.45-1 μm, 1 - 1.8 μm, and 2 - 2.45 μm, respectively.

Observation of NO and NO2 in the young plume of an aircraft jet engine

For the first time the emission indices of NO and NO2 were measured simultaneously in-flight by a non-intrusive spectrometric measurement setup. Moreover the method described here is capable of determining the (static) temperature of the exhaust gas and emission indices for H2O and CO at the same time with a precision of 1–4%. After a very brief description of the experimental setup, results of measurements are shown. They reveal mean emission indices for EI(NO2) of 1 g/kg and 3–5 g/kg for EI(NO) (estimated accuracy: 20–25%). The ratio of concentrations [NO2]/[NOx] of 12–22% is by a factor of approximately two higher than most values cited for other engines. Based on the bulk mean properties of the plume it is shown that the temperature determination is accurate to several Kelvin.

INFRARED SENSOR FOR THE DETECTION AND PROTECTION OF WILDLIFE

A new application of IR sensors for the detection of game is presented. The device detects wildlife (mammals, birds) by using the difference in IR radiation of wildlife and its.

Evaluation procedure for nonintrusive exhaust gas analysis of jet engines using FTIR spectroscopy

A method for the non-intrusive determination of temperature and concentrations of the exhaust gases of aeroengines will be presented. A MIROR-type FTIR spectrometer is used to measure spectra of the IR radiation emitted by the hot gases in the exhaust. New evaluation software, specially developed for this application, is described. The software permits line-by-line radiative transfer modeling of the radiance emitted by the exhaust of these engines. Least squares fitting routines are then used to match the measured with the modeled spectrum, thereby determining the unknown quantities, i.e., temperature and species concentrations. Results of measurements aboard aircraft are presented. The achieved accuracy in temperature is estimated to be better than 1 percent. Comparison of the values determined for the NOx emission index with results from correlation models show deviations of 15 to 20 percent and are thus within the accuracy limits claimed for both methods.

Spektroskopische Fernmessung von Luftschadstoffen unter Einsatz eines Michelson Interferometers mit rotierenden Retroreflektoren

Vorgestellt wird ein neuartiges Michelson Interferometer fur die Fourierspektroskopie, das mit rotierenden Retroreflektoren anstelle eines translatorisch bewegten Planspiegels arbeitet. Die Eignung des Gerats speziell fur den mobilen Einsatz auf dem Gebiet der Umweltmestechnik wird anhand der Forschungsarbeiten beschrieben.

Spectral infrared transmittance of haze and fog: its measurement and influence on FTIR open-path monitoring

Fourier transform infrared (FTIR) open path monitoring OPM is expected to work as a monitoring system for gaseous emissions and imissions within the open atmosphere. As such it is exposed to the dynamics of the atmosphere. Its methods, originating from laboratory spectroscopy, have to be adapted to the conditions of this specific operational area. Among other effects haze and fog influence the radiation transfer of the atmosphere and hence also FTIR- OPM. Model investigations have been performed to investigate the possible influence of haze and fog on common open path monitoring methods. These methods do not account for radiation emitted and scattered by the atmosphere.It is shown that the effects should not be neglected in certain wavelength bands under haze and fog conditions. As a result a new transmittance measurement method has been developed. It allows to completely cancel out the effects of emission and scattering of the transmitting medium. Furthermore it eliminates the influence of the spectrometers inner radiation on the measured spectra, hence yielding pure transmittance spectra. From these then absorption coefficients can be derived and gas parameters like temperature and concentration. The method has been applied to determine the spectral transmittance of haze and fog and been compared to reference measurements.