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Simulation and Experimental Measurement of CO2*, OH* and CH2O* Chemiluminescence from an Optical Diesel Engine Fueled with n-Heptane

Wayne State University-Xin Yu, Kan Zha, Xi Luo, Dinu Taraza, Marcis Jansons
Published 2013-09-08 by SAE International in United States
A means of validating numerical simulations has been developed which utilizes chemiluminescence measurements from an internal combustion engine. By incorporating OH*, CH2O* and CO2* chemiluminescence sub-mechanisms into a detailed n-heptane reaction mechanism, excited species concentration and chemiluminescence light emission were calculated. The modeled line-of-sight chemiluminescence emission allows a direct comparison of simulation results to experimentally measured chemiluminescence images obtained during combustion in an optically accessible compression ignition engine using neat n-heptane fuel. The spray model was calibrated using in-cylinder liquid penetration length Mie scattering measurements taken from the jets of the high-pressure piezo injector. The experimental, two dimensional images of CH2O* and OH* chemiluminescence during the low and high temperature heat release period were recorded with an intensified CCD camera in a wavelength range covering emission from these species. By interpreting the color content of the images taken from a CMOS high speed camera, crank-angle resolved two dimensional CO2* chemiluminescence distributions were obtained. All the chemiluminescence images taken at the same crank angle degrees were used to generate probability density function (PDF) distributions which can…
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Estimation of Main Combustion Parameters from the Measured Instantaneous Crankshaft Speed

Wayne State University-Florin Mocanu, Dinu Taraza
Published 2013-04-08 by SAE International in United States
The increased interest for using alternative fuels in modern diesel engines requires better combustion control to achieve safe and efficient operation with fuels characterized by different physical and chemical properties. Knowing the ignition delay and the cylinder peak pressure will allow adapting the injection strategy, mainly injection timing to maintain good engine efficiency when operating with different alternative fuels. The use of the measured instantaneous crankshaft speed to estimate peak cylinder pressure and ignition delay is very attractive because speed is already a parameter in the ECU of the engine. Based on models using powertrain dynamics, the paper presents the development of several techniques using the measured speed to estimate the main combustion parameters for single cylinder and four cylinder diesel engines.
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Ethanol/N-Heptane Dual-Fuel Partially Premixed Combustion Analysis through Formaldehyde PLIF

SAE International Journal of Engines

Wayne State University-Radu Florea, Kan Zha, Xin Yu, Marcis Jansons, Dinu Taraza, Naeim Henein
  • Journal Article
  • 2012-01-0685
Published 2012-04-16 by SAE International in United States
As a result of recent focus on the control of Low Temperature Combustion (LTC) modes, dual-fuel combustion strategies such as Reactivity Controlled Compression Ignition (RCCI) have been developed. Reactivity stratification of the auto-igniting mixture is thought to be responsible for the increase in allowable engine load compared to other LTC combustion modes such as Homogenous Charge Compression Ignition (HCCI). The current study investigates the effect of ethanol intake fuel injection on in-cylinder formaldehyde formation and stratification within an optically accessible engine operated with n-heptane direct injection using optical measurements and zero-dimensional chemical kinetic models. Images obtained by Planar Laser Induced Fluorescence (PLIF) of formaldehyde using the third harmonic of a pulsed Nd:YAG laser indicate an increase in formaldehyde heterogeneity as measured by the fluorescence signal standard deviation. The experimental observations are complemented by a discussion regarding definitions of “reactivity”.
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Effect of Swirl Ratio and Wall Temperature on Pre-lnjection Chemiluminescence During Starting of an Optical Diesel Engine

SAE International Journal of Engines

Wayne State University-Marcis Jansons, Kan Zha, Radu Florea, Dinu Taraza, Naeim Henein, Walter Bryzik
  • Journal Article
  • 2009-01-2712
Published 2009-11-02 by SAE International in United States
Fuel wall impingement commonly occurs in small-bore diesel engines. Particularly during engine starting, when wall temperatures are low, the evaporation rate of fuel film remaining from previous cycles plays a significant role in the autoignition process that is not fully understood. Pre-injection chemiluminescence (PIC), resulting from low-temperature oxidation of evaporating fuel film and residual gases, was measured over 3200 μsec intervals at the end of the compression strokes, but prior to fuel injection during a series of starting sequences in an optical diesel engine. These experiments were conducted to determine the effect of this parameter on combustion phasing and were conducted at initial engine temperatures of 30, 40, 50 and 60°C, at swirl ratios of 2.0 and 4.5 at 1000 RPM. PIC was determined to increase and be highly correlated with combustion phasing during initial cycles of the starting sequence. This suggests that under starting conditions, combustion phasing is determined by wall film evaporation rates and residual concentrations rather than the fuel injection event. As surface temperatures rise further, wall film evaporation accelerates, and increasing…
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Optical and Numerical Investigation of Pre-Injection Reactions and Their Effect on the Starting of a Diesel Engine

US Army TARDEC-Laura Hoogterp
Wayne State University-Marcis Jansons, Radu Florea, Kan Zha, Fadi Estefanous, Elena Florea, Dinu Taraza, Walter Bryzik, Naeim Henein
Published 2009-04-20 by SAE International in United States
Ultraviolet chemiluminescence has been observed in a diesel engine cyclinder during compression, but prior to fuel injection under engine starting conditions. During a portion of the warm-up sequence, the intensity of this emission exhibits a strong correlation to the phasing of the subsequent combustion. Engine exhaust measurements taken from a continuously misfiring, motored engine confirm the generation of formaldehyde (HCHO) in such processes. Fractions of this compound are expected to be recycled as residual to participate in the following combustion cycle. Spectral measurements taken during the compression period prior to fuel injection match the features of Emeleus' cool flame HCHO bands that have been observed during low temperature heat release reactions occurring in lean HCCI combustion. That the signal from the OH* bands is weak implies a buildup of HCHO during compression. To investigate the combined effects of wall temperature, equivalence ratio and HCHO concentration on combustion phasing, a two-zone CFD-kinetics model was employed utilizing the second version of the Lawrence Livermore National Laboratory detailed n-heptane mechanism [1,2]. The effect of these three parameters was…
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Experimental Investigation of Single and Two-Stage Ignition in a Diesel Engine

US Army TARDEC-Walter Bryzik
Wayne State University-Marcis Jansons, Amandeep Brar, Fadi Estefanous, Radu Florea, Dinu Taraza, Naeim Henein
Published 2008-04-14 by SAE International in United States
This paper presents an experimental investigation conducted to determine the parameters that control the behavior of autoignition in a small-bore, single-cylinder, optically-accessible diesel engine. Depending on operating conditions, three types of autoignition are observed: a single ignition, a two-stage process where a low temperature heat release (LTHR) or cool flame precedes the main premixed combustion, and a two-stage process where the LTHR or cool flame is separated from the main heat release by an apparent negative temperature coefficient (NTC) region. Experiments were conducted using commercial grade low-sulfur diesel fuel with a common-rail injection system. An intensified CCD camera was used for ultraviolet imaging and spectroscopy of chemiluminescent autoignition reactions under various operating conditions including fuel injection pressures, engine temperatures and equivalence ratios. The chemiluminescent spectra were measured to confirm the presence of excited-state formaldehyde, (HCHO*), CH* and OH*, the spatial distribution of which were subsequently observed during the ignition period by filtered imaging. Experiment results based on the apparent rate of heat release (ARHR), indicate that ignition at lower engine temperatures and injection pressure of…
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Transient Fluid Flow and Heat Transfer in the EGR Cooler

SAE International Journal of Engines

US Army, TARDEC-Walter Bryzik
Wayne State University-Radu Florea, Dinu Taraza, Naeim A. Henein
  • Journal Article
  • 2008-01-0956
Published 2008-04-14 by SAE International in United States
EGR is a proven technology used to reduce NOx formation in both compression and spark ignition engines by reducing the combustion temperature. In order to further increase its efficiency the recirculated gases are subjected to cooling. However, this leads to a higher load on the cooling system of the engine, thus requiring a larger radiator. In the case of turbocharged engines the large variations of the pressures, especially in the exhaust manifold, produce a highly pulsating EGR flow leading to non-steady-state heat transfer in the cooler. The current research presents a method of determining the pulsating flow field and the instantaneous heat transfer in the EGR heat exchanger. The processes are simulated using the CFD code FIRE (AVL) and the results are subjected to validation by comparison with the experimental data obtained on a 2.5 liter, four cylinder, common rail and turbocharged diesel engine.
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Engine Friction Model for Transient Operation of Turbocharged, Common Rail Diesel Engines

U.S. Army, TARDEC-Walter Bryzik
Wayne State University-Dinu Taraza, Naeim A. Henein, Radu Ceausu
Published 2007-04-16 by SAE International in United States
The simulation of I.C. Engines operation, especially during transients, requires a fairly accurate estimation of the internal mechanical losses of the engine. The paper presents generic friction models for the main friction components of the engine (piston-ring-liner assembly, bearings and valve train), considering geometry of the engine parts and peculiarities of the corresponding lubrication processes. Separate models for the mechanical losses introduced by the injection system, oil and water pumps are also developed. All models are implemented as SIMULINK modules in a complex engine simulation code developed in SIMULINK and capable to simulate both steady state and transient operating conditions. Validation is achieved by comparison with measurements made on a four cylinder, common rail diesel engine, on a test bench capable to run controlled transients.
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Simplified Elasto-Hydrodynamic Friction Model of the Cam-Tappet Contact

U.S. Army, TARDEC-Walter Bryzik
Wayne State University-Mircea Teodorescu, Dinu Taraza, Naeim A. Henein
Published 2003-03-03 by SAE International in United States
The paper analyses the particularities of the lubricating conditions at the contact between the cam and a flat tappet in the valve train of an internal combustion engine and develops a method for the calculation of the friction force. The existing lubrication models show the predominance of the entraining speed and oil viscosity on the thickness of the oil film entrapped between cam and tappet, predicting a very small value (less than 0.1 μm) of the oil film thickness (OFT). The oil viscosity increases exponentially with pressure in the Hertzian contact, determining non-Newtonian behavior of the oil in the contact zone. Using the model developed by Greenwood and Tripp [11] for the contact of two rough surfaces and the Eyring model [2] for the oil it is shown that non-Newtonian behavior of the oil prevails and that the OFT plays a secondary role on the friction force. The simplified friction model developed according to these assumptions is experimentally validated by measurements made on a single cylinder diesel engine. An original technique was developed to permit…
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Accuracy Limits of IMEP Determination from Crankshaft Speed Mesurements

Wayne State University-Dinu Taraza
Published 2002-03-04 by SAE International in United States
The paper presents a method of determining the Indicated Mean Effective Pressure (IMEP) and the gas pressure torque of a multi-cylinder engine using data obtained from the measurement of the crankshaft's speed variation. At steady state operating conditions a Fourier series describe the gas pressure torque of a cylinder and the resultant torque may be obtained by adding the harmonic components corresponding to all cylinders. Only the major harmonic orders, having the same phase for all cylinders add algebraically appearing with large contributions in the spectrum of the resultant torque. The lowest major component has a low frequency and, at this frequency, the crankshaft behaves dynamically like a rigid body. In this situation it is possible to correlate the amplitude of this harmonic order of the gas pressure torque to the same harmonic order of the crankshaft speed. The statistical nature of the cycle-to-cycle variation in the engine operation determines limits of the accuracy by which the IMEP and the gas pressure torque may be calculated by this method. The errors are fairly low at…
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