Validation and sensitivity analysis of an in-flow water condensation model for 3D-CFD simulations of humid air streams mixing

In recent years, many engine manufacturers have turned to downsizing and boosting of gasoline engines in order to meet the ever more stringent fuel economy and emissions regulations. With an increase in the number of turbocharged gasoline engines, solutions are required to manage knock under a range of operating conditions. The charge air cooler has been introduced to mitigate knock. Moreover, the engine is required to operate with spark retard and/or boost reduction to provide knock reduction leading to reduced fuel economy. Under some operating conditions water can condense in the charge air cooler (CAC). Corrugated plate separators have been widely used in gas-water separation and oil-water separation in many industries including marine diesel engines. However, this sort of separator has not been applied to gasoline engines in vehicles to separate the condensation in the charged air. In this paper, a 1-D condensation model to estimate the potential amount of water condensation and entrainment from the charge air coolers is presented. An approach to designing a unit to separate condensation in the flow from the charge air cooler while maintaining a low pressure drop is described. The design approach provides correlations of separator geometries versus separation and pressure drop performance. The study is developed using a 3-D computational model for analyzing charge air and condensation flow. The model results of the 1-D condensation model and the 3-D computational model have been validated by experiments on an engine-dynamometer based test cell. The set-up incorporates a 4 cylinder gasoline direct injection (GDI) turbocharged engine. An air-to-air charge air cooler is mounted under the engine. The intake air for the engine is supplied using a combustion air unit which enables the operators to control the temperature and humidity. Test conditions have been identified to demonstrate the phenomenon of CAC water condensation. Measurements of water condensation and motion through the system confirm the results of models. A separator has been designed that achieves high separation efficiency and low pressure drop.

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Development and Validation of a Reduced Toluene/N-Heptane/N-Butanol Mechanism for Combustion and Emission Prediction in IC Engine

Volume 1: Large Bore Engines; Fuels; Advanced Combustion ◽

10.1115/icef2015-1157 ◽

2015 ◽

Author(s):

Zhengxin Xu ◽

Mianzhi Wang ◽

Jie Hou ◽

Saifei Zhang ◽

Jingping Liu ◽

...

Keyword(s):

Sensitivity Analysis ◽

Soot Formation ◽

Laminar Flame ◽

Reaction Pathway ◽

Injection Timing ◽

Soot Emission ◽

Formation Processes ◽

Cfd Simulations ◽

Ic Engine ◽

Soot Emissions

The present study proposed a reduced mechanism for a fuel blend of toluene reference fuel (TRF, toluene/n-heptane) and n-butanol for modeling the combustion and soot formation processes of n-butanol/diesel blend fuel. A detailed reaction mechanism for n-butanol, consisting of 243 species and 1446 reactions, and a reduced TRF mechanism, containing 158 species and 468 reactions, were reduced separately and then combined to create a new TRF/n-butanol mechanism. The new TRF/n-butanol mechanism contained 107 species and 413 reactions. A multi-technique reduction methodology was used which included directed relation graph with error propagation and sensitivity analysis (DRGEPSA), unimportant reaction elimination, reaction pathway analysis, and sensitivity analysis. In addition, a reduced 12-step NOx mechanism was combined with the TRF/n-butanol mechanism to predict NOx emissions. The proposed mechanism was also coupled with a multi-step soot model to predict the combustion and soot formation processes. The proposed mechanism was validated using available ignition delay times, laminar flame speeds and species concentration profiles from shock tubes, flat flame burner and jet stirred reactors. Good agreements were found for the above comparisons and with results from detailed mechanisms. Furthermore, multi-dimensional CFD simulations were conducted by using the KIVA-3V R2 code coupled with the preconditioned Krylov method. The effects of exhaust gas recirculation (EGR), injection timing and blending ratio of n-butanol on combustion and NOx formation were analyzed and validated experimental data. The pressure, heat release rate, NOx, and soot emissions with respect to fuel blends, EGR rates and start of injection (SOI) timings agreed well with the experimental results. With increasing n-butanol content, both experimental and calculated soot emission decreased, demonstrating that butanol additive was capable of reducing soot emission compared to pure diesel. Both experiments and models revealed that soot emissions peak occurred at SOI close to TDC. The proposed mechanism can readily be used to predict the combustion and soot formation processes of butanol-diesel blends fuel in combustion CFD simulations.

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Accurate measurements of carbon monoxide in humid air using the cavity ring-down spectroscopy (CRDS) technique

Atmospheric Measurement Techniques Discussions ◽

10.5194/amtd-5-6493-2012 ◽

2012 ◽

Vol 5 (5) ◽

pp. 6493-6517 ◽

Cited By ~ 4

Author(s):

H. Chen ◽

A. Karion ◽

C. W. Rella ◽

J. Winderlich ◽

C. Gerbig ◽

...

Keyword(s):

Carbon Monoxide ◽

Water Vapor ◽

Near Infrared ◽

Infrared Region ◽

Humid Air ◽

Cavity Ring Down Spectroscopy ◽

Carbon Dioxide Co2 ◽

Air Streams ◽

Line Interference ◽

Cavity Ring Down

Abstract. Accurate measurements of carbon monoxide (CO) in humid air have been made using the cavity ring-down spectroscopy (CRDS) technique. The measurements of CO mole fractions are determined from the strength of its spectral absorption in the near infrared region (∼1.57 μm) after removing interferences from adjacent carbon dioxide (CO2) and water vapor (H2O) absorption lines. Water correction functions that account for the dilution and pressure-broadening effects as well as absorption line interferences from adjacent CO2 and H2O lines have been derived for CO2 mole fractions between 360–390 ppm. The line interference corrections are independent of CO mole fractions. The dependence of the line interference correction on CO2 abundance is estimated to be approximately −0.3 ppb/100 ppm CO2 for dry mole fractions of CO. Comparisons of water correction functions from different analyzers of the same type show significant differences, making it necessary to perform instrument-specific water tests for each individual analyzer. The CRDS analyzer was flown on an aircraft in Alaska from April to November in 2011, and the accuracy of the CO measurements by the CRDS analyzer has been validated against discrete NOAA/ESRL flask sample measurements made on board the same aircraft, with a mean difference between integrated in situ and flask measurements of −0.6 ppb and a standard deviation of 2.8 ppb. Preliminary testing of CRDS instrumentation that employs new spectroscopic analysis (available since the beginning of 2012) indicates a smaller water vapor dependence than the models discussed here, but more work is necessary to fully validate the performance. The CRDS technique provides an accurate and low-maintenance method of monitoring the atmospheric dry mole fractions of CO in humid air streams.

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