Laser based measurement of water film thickness for the application in exhaust after-treatment processes

Schmidt, Anna; Kühnreich, Benjamin; Kittel, Hannah; Tropea, Cameron; Roisman, Ilia V.; Dreizler, Andreas; Wagner, Steven

doi:10.1016/j.ijheatfluidflow.2018.04.013

Cited by 13 publications

(7 citation statements)

References 13 publications

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“…Spectra in the wavenumber range from around 2000 cm −1 to 15,000 cm −1 were recorded with a thermoelectrically cooled Indium Gallium Arsenide (TE InGaAs) detector. A calibration cell [16] was used to enable transmission measurements with predefined parameter variations (see Figure 1). The UWS is placed within the stainless steel spacer ring, which is then clamped between two wedged calcium fluoride (CaF 2 ) windows, two O-seals and the top and body plates of the cell.…”

Section: Experimental Setup and Methodologymentioning

confidence: 99%

“…In this work, we propose the extension of the film measurement laser absorption spectroscopy (FMLAS) method, which has previously been validated and implemented for film thickness measurements, for the determination of temperatures and concentrations of a thin UWS film [15][16][17]. The FMLAS method provides some significant advantages: it is 2 of 11 non-intrusive, allows for a high temporal resolution and has a cost-effective setup based on readily available near-infrared laser diodes.…”

Section: Introductionmentioning

confidence: 99%

“…where the detected light intensity I ν is a function of the incident light I 0,ν and the absorbance α ν at the wavenumber ν. In turn, α ν is a function of the absorption coefficient κ ν and the film parameters of film thickness δ, concentration c and temperature T. With the FMLAS approach, δ can be determined by intensity measurements at two suitable wavenumbers through quotient formation after calibration (see [16]). The aim of this work is to find optimized wavenumber combinations that allow for the determination of δ as well as the additional film parameters of T and c (concentration %mass of urea in water).…”

Section: Introductionmentioning

confidence: 99%

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Multiparameter Determination of Thin Liquid Urea-Water Films

et al. 2021

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In this work, wavelengths were determined for the robust and simultaneous measurement of film thickness, urea concentration and fluid temperature. Film parameters such as film thickness, film temperature and the composition of the film are typically dynamically and interdependently changing. To gain knowledge of these quantities, a measurement method is required that offers a high temporal resolution while being non-intrusive so as to not disturb the film as well as the process conditions. We propose the extension of the FMLAS method, which was previously validated for the film thickness measurement of thin liquid films, to determine temperatures and concentrations using an adapted evaluation approach.

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Section: Experimental Setup and Methodologymentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Multiparameter Determination of Thin Liquid Urea-Water Films

et al. 2021

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“…The gas temperature covers the range typical for SCR systems, with 180 • C representing the lower limit for the hydrolysis of isocyanic acid [38]. In addition, ammonium nitrate is deposited in the catalyst at temperatures well below 200 • C [2].…”

Section: Operating Pointsmentioning

confidence: 99%

Experimental Investigation of AdBlue Film Formation in a Generic SCR Test Bench and Numerical Analysis Using LES

et al. 2021

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In this work, an experimental investigation of AdBlue film formation in a generic selective catalytic reduction (SCR) exhaust gas test bench is presented. AdBlue is injected into a generic SCR test bench resulting in liquid film formation on the lower wall of the channel. The thickness of this liquid film is measured using a film thickness sensor based on absorption spectroscopy. Simultaneously, the wall temperature at the measurement point is monitored, which allows for examining correlations between the evolution of the film thickness and the temperature of the wetted wall. The velocity of the airflow in the channel and the initial wall temperature are varied in the experiments. Correspondingly, the measurements are performed during different thermodynamic regimes, including liquid film deposition and boiling. Repeated measurements have also shown that the film thicknesses are reproducible with a standard deviation of 3.4 %. LES-based numerical simulations are compared to the experimental results of the film thickness during the early injection stage. Finally, a numerical analysis is performed to analyze the AdBlue droplet impingement and subsequent film-formation dynamics.

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“…Lubnow implemented near-infrared imaging using four wavelengths with a filter wheel, increasing the image acquisition time. Schmidt et al investigated the dynamic changing of fluid thickness by using an absorptionbased laser sensor and the near-infrared spectra of liquid water for film thickness up to 440 µm [55]. Film thickness measurements in evaporation and flow processes of the refrigerant R1233zd by absorption spectroscopy in the near-infrared area were studied by Kong et al [56].…”

Section: Introductionmentioning

confidence: 99%

Film Thickness and Glycerol Concentration Mapping of Falling Films Based on Fluorescence and Near-Infrared Technique

2022

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Falling film evaporation processes involve high fluid velocities with continuous variations in local film thickness, fluid composition, and viscosity. This contribution presents a parallel and complementary film thickness and concentration mapping distribution in falling films using a non-invasive fluorescence and near-infrared imaging technique. The experiments were performed with a mixture of glycerol/water with a mass fraction from 0 to 0.65 gglycgtotal−1 and operating ranges similar to evaporation processes. The measurement system was designed by integrating two optical measurement methods for experimental image analysis. The film thickness was evaluated using a VIS camera and high-power LEDs at 470 nm. The local glycerol concentration gglycgtotal−1 was determined using a NIR camera and high-power LEDs at 1050, 1300, 1450 and 1550 nm. A multiwavelength analysis with all NIR wavelengths was implemented with a better correlation for falling films at low flow velocity. The results show an improvement in the analysis of falling films with high flow velocities up to almost 500 mm/s by using only the 1450 nm wavelength and the fluorescence measurement. Simultaneous imaging analysis of film thickness and concentration in falling films provides further insight into understanding mass and heat transport and thus supports the optimization of falling film evaporators.

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Laser based measurement of water film thickness for the application in exhaust after-treatment processes

Cited by 13 publications

References 13 publications

Multiparameter Determination of Thin Liquid Urea-Water Films

Multiparameter Determination of Thin Liquid Urea-Water Films

Experimental Investigation of AdBlue Film Formation in a Generic SCR Test Bench and Numerical Analysis Using LES

Film Thickness and Glycerol Concentration Mapping of Falling Films Based on Fluorescence and Near-Infrared Technique

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