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Applying Advanced CFD Analysis Tools to Study Differences between Start-of-Main and Start-of-Post Injection Flow, Temperature and Chemistry Fields Due to Combustion of Main-Injected Fuel

SAE International Journal of Engines

Univ. of Wisconsin-Randy Hessel, Rolf D. Reitz, Zongyu Yue
Pennsylvania State University-Jacqueline O'Connor
  • Journal Article
  • 2015-24-2436
Published 2015-09-06 by SAE International in United States
This paper is part of a larger body of experimental and computational work devoted to studying the role of close-coupled post injections on soot reduction in a heavy-duty optical engine. It is a continuation of an earlier computational paper. The goals of the current work are to develop new CFD analysis tools and methods and apply them to gain a more in depth understanding of the different in-cylinder environments into which fuel from main- and post-injections are injected and to study how the in-cylinder flow, thermal and chemical fields are transformed between start of injection timings.The engine represented in this computational study is a single-cylinder, direct-injection, heavy-duty, low-swirl engine with optical components. It is based on the Cummins N14, has a cylindrical shaped piston bowl and an eight-hole injector that are both centered on the cylinder axis. The fuel used was n-heptane and the engine operating condition was light load at 1200 RPM.The in-cylinder processes investigated are typical and include fuel injection and the subsequent growth of a largely non-combusting fuel-rich vapor jet, pre-mixed burn…
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Effects of Fuel Physical Properties on Auto-Ignition Characteristics in a Heavy Duty Compression Ignition Engine

SAE International Journal of Fuels and Lubricants

Univ. of Wisconsin-Michael A. Groendyk, David Rothamer
  • Journal Article
  • 2015-01-0952
Published 2015-04-14 by SAE International in United States
The effect of fuel physical properties on the ignition and combustion characteristics of diesel fuels was investigated in a heavy-duty 2.52 L single-cylinder engine. Two binary component fuels, one comprised of farnesane (FAR) and 2,2,4,4,6,8,8-heptamethylnonane (HMN), and another comprised of primary reference fuels (PRF) for the octane rating scale (i.e. n-heptane and 2,2,4-trimethylpentane), were blended to match the cetane number (CN) of a 45 CN diesel fuel. The binary mixtures were used neat, and blended at 25, 50, and 75% by volume with the baseline diesel. Ignition delay (ID) for each blend was measured under identical operating conditions. A single injection was used, with injection timing varied from −12.5 to 2.5 CAD. Injection pressures of 50, 100, and 150 MPa were tested. Observed IDs were consistent with previous work done under similar conditions with diesel fuels. The shortest IDs were seen at injection timings of −7.5 CAD. The largest difference in ID between all fuels of 75 ± 18 μs was observed at the earliest injection timing with an injection pressure of 50 MPa. The…
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Numerical Study of RCCI and HCCI Combustion Processes Using Gasoline, Diesel, iso-Butanol and DTBP Cetane Improver

SAE International Journal of Engines

Univ. of Wisconsin-Dan DelVescovo, Rolf D. Reitz
Univ. of Wisconsin, Tianjin Univ.-Hu Wang
  • Journal Article
  • 2015-01-0850
Published 2015-04-14 by SAE International in United States
Reactivity Controlled Compression Ignition (RCCI) has been shown to be an attractive concept to achieve clean and high efficiency combustion. RCCI can be realized by applying two fuels with different reactivities, e.g., diesel and gasoline. This motivates the idea of using a single low reactivity fuel and direct injection (DI) of the same fuel blended with a small amount of cetane improver to achieve RCCI combustion. In the current study, numerical investigation was conducted to simulate RCCI and HCCI combustion and emissions with various fuels, including gasoline/diesel, iso-butanol/diesel and iso-butanol/iso-butanol+di-tert-butyl peroxide (DTBP) cetane improver. A reduced Primary Reference Fuel (PRF)-iso-butanol-DTBP mechanism was formulated and coupled with the KIVA computational fluid dynamic (CFD) code to predict the combustion and emissions of these fuels under different operating conditions in a heavy duty diesel engine. The results show that RCCI combustion is achievable by applying a single low reactivity fuel combined with small amount of DTBP cetane improver over wide operating conditions, and that the performance of the iso-butanol-DTBP fuel is comparable to that of gasoline-diesel and iso-butanol-diesel…
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Use of Multiple Injection Strategies to Reduce Emission and Noise in Low Temperature Diesel Combustion

Univ. of Wisconsin-Wonah Park, Youngchul Ra, Rolf D. Reitz
Ford Forschungszentrum Aachen GmbH-Werner Willems
Published 2015-04-14 by SAE International in United States
The low temperature combustion concept is very attractive for reducing NOx and soot emissions in diesel engines. However, it has potential limitations due to higher combustion noise, CO and HC emissions. A multiple injection strategy is an effective way to reduce unburned emissions and noise in LTC. In this paper, the effect of multiple injection strategies was investigated to reduce combustion noise and unburned emissions in LTC conditions. A hybrid surrogate fuel model was developed and validated, and was used to improve LTC predictions. Triple injection strategies were considered to find the role of each pulse and then optimized. The split ratio of the 1st and 2nd pulses fuel was found to determine the ignition delay. Increasing mass of the 1st pulse reduced unburned emissions and an increase of the 3rd pulse fuel amount reduced noise. It is concluded that the pulse distribution can be used as a control factor for emissions and noise.
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The Effect of Operating Parameters on Soot Emissions in GDI Engines

SAE International Journal of Engines

Univ. of Wisconsin-Qi Jiao, Rolf D. Reitz
  • Journal Article
  • 2015-01-1071
Published 2015-04-14 by SAE International in United States
Due to the upcoming regulations for particulate matter (PM) emissions from GDI engines, a computational fluid dynamic (CFD) modeling study to predict soot emissions (both mass and solid particle number) from gasoline direct injection (GDI) engines was undertaken to provide insights on how and why soot emissions are formed from GDI engines. In this way, better methods may be developed to control or reduce PM emissions from GDI engines. In this paper, the influence of engine operating parameters was examined for a side-mounted fuel injector configuration in a direct-injection spark-ignition (DISI) engine. The present models are able to reasonably predict the influences of the variables of interest compared to available experimental data or literature. For a late injection strategy, effects of the fuel composition, and spray cone angle were investigated with a single-hole injector. For an early injection strategy, the effects of multi-component fuel surrogates for gasoline, SOI timings and wall temperatures were studied with a six-hole injector. The investigations confirmed the necessity to consider the multi-component fuel composition and also demonstrate how and why…
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Development of a Miller Cycle Powersports Engine

Univ. of Wisconsin-Jeffrey Blair, Glenn Bower
Published 2014-11-11 by SAE International in United States
Operation of snowmobiles in national parks is restricted to vehicles meeting the Best Available Technology standard for exhaust and noise emissions as established by the National Parks Service. An engine exceeding these standards while operating on a blend of gasoline and bio-isobutanol has been developed based on a production four-stroke snowmobile engine. Miller cycle operation was achieved via late intake valve closing and turbocharging. The production Rotax ACE 600cc 2 cylinder engine was modeled using Ricardo WAVE. After this model was validated with physical testing, different valve lift profiles were evaluated for brake specific fuel consumption and brake power. The results from this analysis were used to determine a camshaft profile for Miller cycle operation. This was done to reduce part load pumping losses and increase engine efficiency while maintaining production power density. A catalytic converter was added to reduce exhaust gas emissions, as measured by the EPA 40 CFR Part 1051 5-mode emissions test cycle. Laboratory testing was conducted on the engine using a water brake dynamometer and in-cylinder pressure transducers. The result is…
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Experimental and Computational Assessment of Inlet Swirl Effects on a Gasoline Compression Ignition (GCI) Light-Duty Diesel Engine

Univ. of Wisconsin-Paul Loeper, Youngchul Ra, David E. Foster, Jaal Ghandhi
Published 2014-04-01 by SAE International in United States
The light-medium load operating regime (4-8 bar net IMEP) presents many challenges for advanced low temperature combustion strategies (e.g. HCCI, PPC) in light-duty, high speed engines. In this operating regime, lean global equivalence ratios (Φ<0.4) present challenges with respect to autoignition of gasoline-like fuels. Considering this intake temperature sensitivity, the objective of this work was to investigate, both experimentally and computationally, gasoline compression ignition (GCI) combustion operating sensitivity to inlet swirl ratio (Rs) variations when using a single fuel (87-octane gasoline) in a 0.475-liter single-cylinder engine based on a production GM 1.9-liter high speed diesel engine.For the first part of this investigation, an experimental matrix was developed to determine how changing inlet swirl affected GCI operation at various fixed load and engine speed operating conditions (4 and 8 bar net IMEP; 1300 and 2000 RPM). Here, experimental results showed significant changes in CA50 due to changes in inlet swirl ratio. For example, at the 4 bar net IMEP operating condition at 1300 RPM, a reduction in swirl ratio (from 2.2 to 1.5) caused a 6…
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Computational Investigation of Low Load Operation in a Light-Duty Gasoline Direct Injection Compression Ignition [GDICI] Engine Using Single-Injection Strategy

Univ. of Wisconsin-Bishwadipa Das Adhikary, Rolf D. Reitz
Argonne National Lab.-Stephen Ciatti, Christopher Kolodziej
Published 2014-04-01 by SAE International in United States
The use of gasoline in a compression ignition engine has been a research focus lately due to the ability of gasoline to provide more premixing, resulting in controlled emissions of the nitrogen oxides [NOx] and particulate matter. The present study assesses the reactivity of 93 RON [87AKI] gasoline in a GM 1.9L 4-cylinder diesel engine, to extend the low load limit. A single injection strategy was used in available experiments where the injection timing was varied from −42 to −9 deg ATDC, with a step-size of 3 deg. The minimum fueling level was defined in the experiments such that the coefficient of variance [COV] of indicated mean effective pressure [IMEP] was less than 3%. The study revealed that injection at −27 deg ATDC allowed a minimum load of 2 bar BMEP. Also, advancement in the start of injection [SOI] timing in the experiments caused an earlier CA50, which became retarded with further advancement in SOI timing. To help explain these behaviors, simulations were carried out using the KIVA3V CFD code coupled with a Jacobian chemistry…
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Design & Evaluation of an Exhaust Filtration Analysis (EFA) System

Univ. of Wisconsin-Sandeep Viswanathan, Stephen Sakai, David Rothamer
Published 2014-04-01 by SAE International in United States
The Diesel Exhaust Filtration Analysis System (DEFA) developed at the University of Wisconsin Madison was modified to perform fundamental filtration experiments using particulate matter (PM) generated by a spark-ignition direct-injection (SIDI) engine fueled with gasoline. The newly modified system, termed the Exhaust Filtration Analysis (EFA) system, enables small-scale fundamental studies of wall-flow filtration processes. A scanning mobility particle sizer (SMPS) was used to characterize running conditions with unique particle size distributions (PSDs). The SMPS and an engine exhaust particle sizer (EEPS) were used to simultaneously measure the PSD downstream of the EFA and the real-time particulate emissions from the SIDI engine, to determine the evolution of filtration efficiency during filter loading. Corrections were developed for each running condition to compare measured PSDs between the EEPS and the SMPS in the raw, as well as, filtered exhaust stream. Background losses in the EFA system (without a filter sample) were quantified for each operating condition. Several steps were taken to minimize these losses using conventional knowledge on Brownian diffusion of particulates. Results from filtration experiments for one…
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Comparison of Measurement Strategies for Light Absorbing Aerosols from Modern Diesel Engines

SAE International Journal of Fuels and Lubricants

Univ. of Wisconsin-Michael Olson, James Schauer
Cummins Emission Solutions-Michael Robinson, Z. Gerald Liu
  • Journal Article
  • 2014-01-1570
Published 2014-04-01 by SAE International in United States
Light absorbing components of aerosols, often called black carbon (BC), are emitted from combustion sources and are believed to play a considerable role in direct atmospheric radiative forcing by a number of climate scientists. In addition, it has been shown that BC is associated with adverse health effects in a number of epidemiological studies. Although the optical properties (both absorbing and scattering) of combustion aerosols are needed in order to accurately assess the impact of emissions on radiative forcing, many models use radiative properties of diesel particulate matter that were determined over two decades ago. In response to concerns of the human health impacts of particulate matter (PM), regulatory bodies around the world have significantly tightened PM emission limits for diesel engines. These requirements have resulted in considerable changes in engine technology requiring updated BC measurements from modern engines equipped with aftertreatment systems. In this study, a variety of common ambient monitoring techniques were used to characterize the light absorbing properties of diesel aerosol. Aerosol optical properties were directly measured with an Aethalometer and Photoacoustic…
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