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Journal Article

Evaluation of Diesel Oxidation Catalyst Conversion of Hydrocarbons and Particulate Matter from Premixed Low Temperature Combustion of Biodiesel

2011-04-12
2011-01-1186
Premixed low temperature combustion (LTC) in diesel engines simultaneously reduces soot and NOx at the expense of increased hydrocarbon (HC) and CO emissions. The use of biodiesel in the LTC regime has been shown to produce lower HC emissions than petroleum diesel; however, unburned methyl esters from biodiesel are more susceptible to particulate matter (PM) formation following atmospheric dilution due to their low volatility. In this study, the efficacy of a production-type diesel oxidation catalyst (DOC) for the conversion of light hydrocarbons species and heavier, semi-volatile species like those in unburned fuel is examined. Experimental data were taken from a high speed direct-injection diesel engine operating in a mid-load, late injection partially premixed LTC mode on ultra-low sulfur diesel (ULSD) and neat soy-based biodiesel (B100). Gaseous emissions were recorded using a conventional suite of analyzers and individual light HCs were measured using an FT-IR analyzer.
Technical Paper

Bridging the Gap between HCCI and SI: Spark-Assisted Compression Ignition

2011-04-12
2011-01-1179
Homogeneous charge compression ignition (HCCI) has received much attention in recent years due to its ability to reduce both fuel consumption and NO emissions compared to normal spark-ignited (SI) combustion. However, due to the limited operating range of HCCI, production feasible engines will need to employ a combination of combustion strategies, such as stoichiometric SI combustion at high loads and leaner burn spark-assisted compression ignition (SACI) and HCCI at intermediate and low loads. The goal of this study was to extend the high load limit of HCCI into the SACI region while maintaining a stoichiometric equivalence ratio. Experiments were conducted on a single-cylinder research engine with fully flexible valve actuation. In-cylinder pressure rise rates and combustion stability were controlled using cooled external EGR, spark assist, and negative valve overlap. Several engine loads within the SACI regime were investigated.
Journal Article

Comparison of ULSD, Used Cooking Oil Biodiesel, and JP-8 Performance and Emissions in a Single-Cylinder Compression-Ignition Engine

2012-10-23
2012-32-0009
With the rapid growth of biodiesel production, it is prudent to research ways to improve its operation and performance in an engine, especially concerning fuel economy and exhaust emissions. This requires a thorough understanding of both the biodiesel production and engine operating processes. Completion of a published study of the impact of biodiesel fuel properties on engine operation indicated that it is difficult to draw conclusions about the exact causes of increased NOx emissions with respect to biodiesel properties without the capability of measuring engine cylinder pressures. As improvements were made to the authors' laboratory, a system to monitor and record pressure inside a diesel engine during operation was constructed to test dissimilar fuels. In the current work, three different fuels were tested in order to investigate combustion phasing, emissions, and fuel consumption as a function of fuel properties such as density, viscosity, Cetane Number, and energy content.
Journal Article

Organic Rankine Cycles with Dry Fluids for Small Engine Exhaust Waste Heat Recovery

2013-04-08
2013-01-0878
Engine manufacturers are considering the implementation of thermodynamic cycles for Waste Heat Recovery (WHR) in order to increase Internal Combustion Engine (ICE) system thermal efficiency. For these secondary cycles, the literature illustrates the preference of Organic Rankine Cycles (ORC's) due to its simplicity and efficient recovery of the medium grade waste heat found in engine exhaust. This paper simulates the heat recovery capacity of eight dry fluids (butane, pentane, hexane, cyclopentane, benzene, toluene, R245fa, and R123) for an ORC based on the exhaust from a single-cylinder diesel engine-generator operating under five different loading conditions. The model, developed using REFPROP and the Matlab Optimization Toolbox, represents the physical components using isentropic pump and expander efficiencies, along with two-zone heat exchangers. All fluids present cycle efficiencies between 10-15%, with the heaviest hydrocarbons generating the largest amount of work.
Technical Paper

Recommendations for the Next Generation of Hydrocarbon Modeling with Respect to Diesel Exhaust Aftertreatment and Biodiesel Fuels

2013-04-08
2013-01-1348
The modeling of emitted hydrocarbons from internal combustion engines for exhaust aftertreatment devices has remained relatively unchanged since the early 1970s. This older model subdivides the hydrocarbon species into fast, slow, and non-oxidizing components. Current and future regulations from the United States Environmental Protection Agency stretch the abilities of this methodology, necessitating the need for more advanced modeling techniques. To this end, this paper provides a review on the different groups of hydrocarbons in order to provide background and contextual information on the different species expected in diesel emissions. Additionally, this work groups these species into different categories, depending on their chemical make-up, impact on human health, reactivity in the environment, and their prevalence within diesel emissions.
Journal Article

Design and Modeling of a Novel Internal Combustion Engine with Direct Hydraulic Power Take-off

2013-04-08
2013-01-1733
This paper introduces a Hydraulic Linear Engine (HLE) concept and describes a model to simulate instantaneous engine behavior. The United States Environmental Protection Agency has developed an HLE prototype as an evolution of their previous six-cylinder, four-stroke, free-piston engine (FPE) hardware. The HLE design extracts work hydraulically, in a fashion identical to the initial FPE, and is intended for use in a series hydraulic hybrid vehicle. Unlike the FPE, however, the HLE utilizes a crank for improved timing control and increased robustness. Preliminary experimental results show significant speed fluctuations and cylinder imbalance that require careful controls design. This paper also introduces a model of the HLE that exhibits similar behavior, making it an indispensible tool for controls design. Further, the model's behavior is evaluated over a range of operating conditions currently unobtainable by the experimental setup.
Technical Paper

Efficiency and Emissions Mapping for a Single-Cylinder, Direct Injected Compression Ignition Engine

2014-04-01
2014-01-1242
A timing sweep to correlate the location of Maximum Brake Torque (MBT) was completed on a single-cylinder, direct injected compression ignition engine that was recently upgraded to a high-pressure rail injection system for better engine control. This sweep included emissions monitoring for carbon dioxide, carbon monoxide, particulate matter, hydrocarbons, and oxides of nitrogen for the calibration of a heat release model, as well as the opportunity to relate MBT timing to brake-specific emissions production. The result of this timing sweep was a relatively linear correlation between injection delay and peak pressure timing. In addition, a number of other MBT timing methodologies were tested indicating their applicability for immediate feedback upon engine testing, particularly mass fraction burned correlations. Emissions were either strongly correlated to MBT timing (with emissions being minimized in the vicinity of MBT), or were completely independent of MBT.
Technical Paper

Development of a Simplified Diesel Particulate Filter Model Intended for an Engine Control Unit

2014-04-01
2014-01-1559
Diesel Particulate Filters (DPFs) have become a required aftertreatment device for Compression Ignition engine exhaust cleanup of Particulate Matter (PM). Moreover, with the increased prevalence of Spark Ignition Direct Injection (SIDI) systems, discussions are currently underway regarding the need of Gasoline Particulate Filters to handle the PM emanating from their combustion process. In this area, the two-channel DPF model has been widely successful in predicting the temperature, pressure drop, and species conversion in these devices. Because of the need to simulate compressible flow through the channels and a porous wall, these models have a difficult time achieving real-time predictive results suitable for an Engine Control Unit (ECU). As a result, this effort describes the creation of a lumped DPF model intended for an ECU. Model formulation was based on the standard governing equations, but simplified in order to remove as much computational overhead as possible.
Journal Article

A Cost-Effective Alternative to Moving Floor Wind Tunnels in Order to Calculate Rolling Resistance and Aerodynamic Drag Coefficients

2014-04-01
2014-01-0620
This study investigates the practicality of vehicle coast down testing as a suitable replacement to moving floor wind tunnel experimentation. The recent implementation of full-scale moving floor wind tunnels is forcing a re-estimation of previous coefficient of drag determinations. Moreover, these wind tunnels are relatively expensive to build and operate and may not capture concepts such as linear and quadratic velocity dependency along with the influence of tire pressure on rolling resistance. As a result, the method elucidated here improves the accuracy of the fundamental vehicle modeling equations while remaining relatively affordable. The trends produced by incorporating on road test data into the model fit the values indicated by laboratory tests. This research chose equipment based on a balance between affordability and accuracy while illustrating that higher resolution frequency equipment would further enhance the model accuracy.
Technical Paper

Combining a Diesel Particulate Filter and Heat Exchanger for Waste Heat Recovery and Particulate Matter Reduction

2014-04-01
2014-01-0673
Significant progress towards reducing diesel engine fuel consumption and emissions is possible through the simultaneous Waste Heat Recovery (WHR) and Particulate Matter (PM) filtration in a novel device described here as a Diesel Particulate Filter Heat Exchanger (DPFHX). This original device concept is based on the shell-and-tube heat exchanger geometry, where enlarged tubes contain DPF cores, allowing waste heat recovery from engine exhaust and allowing further energy capture from the exothermic PM regeneration event. The heat transferred to the working fluid on the shell side of the DPFHX becomes available for use in a secondary power cycle, which is an increasingly attractive method of boosting powertrain efficiency due to fuel savings of around 10 to 15%. Moreover, these fuel savings are proportional to the associated emissions reduction after a short warm-up period, with startup emissions relatively unchanged when implementing a WHR system.
Technical Paper

Construction, Instrumentation, and Implementation of a Low Cost, Single-Cylinder Compression Ignition Engine Test Cell

2014-04-01
2014-01-0817
In order to perform cutting-edge engine research that applies to modern Compression Ignition (CI) engines, a sophisticated test cell is needed that allows control of the engine and its auxiliary systems. The primary obstacle to the completion of such a test cell is the up-front expense. This paper covers the construction of a low cost, single-cylinder engine test cell while demonstrating the type of research that can be accomplished along the way. The components necessary for the construction, instrumentation, and operation of such a test cell, neglecting emissions analysis equipment, can be obtained for less than $150,000. The engine utilized, a naturally-aspirated single-cylinder Yanmar L100V, was purchased as an engine-generator package.
Technical Paper

Turbulence Intensity Calculation from Cylinder Pressure Data in a High Degree of Freedom Spark-Ignition Engine

2010-04-12
2010-01-0175
The number of control actuators available on spark-ignition engines is rapidly increasing to meet demand for improved fuel economy and reduced exhaust emissions. The added complexity greatly complicates control strategy development because there can be a wide range of potential actuator settings at each engine operating condition, and map-based actuator calibration becomes challenging as the number of control degrees of freedom expand significantly. Many engine actuators, such as variable valve actuation and flow control valves, directly influence in-cylinder combustion through changes in gas exchange, mixture preparation, and charge motion. The addition of these types of actuators makes it difficult to predict the influences of individual actuator positioning on in-cylinder combustion without substantial experimental complexity.
Technical Paper

Turbocharger Matching for a 4-Cylinder Gasoline HCCI Engine Using a 1D Engine Simulation

2010-10-25
2010-01-2143
Naturally aspirated HCCI operation is typically limited to medium load operation (∼ 5 bar net IMEP) by excessive pressure rise rate. Boosting can provide the means to extend the HCCI range to higher loads. Recently, it has been shown that HCCI can achieve loads of up to 16.3 bar of gross IMEP by boosting the intake pressure to more than 3 bar, using externally driven compressors. However, investigating HCCI performance over the entire speed-load range with real turbocharger systems still remains an open topic for research. A 1 - D simulation of a 4 - cylinder 2.0 liter engine model operated in HCCI mode was used to match it with off-the-shelf turbocharger systems. The engine and turbocharger system was simulated to identify maximum load limits over a range of engine speeds. Low exhaust enthalpy due to the low temperatures that are characteristic of HCCI combustion caused increased back-pressure and high pumping losses and demanded the use of a small and more efficient turbocharger.
Journal Article

Comparison of Different Boosting Strategies for Homogeneous Charge Compression Ignition Engines - A Modeling Study

2010-04-12
2010-01-0571
Boosted Homogeneous Charge Compression Ignition (HCCI) has been modeled and has demonstrated the potential to extend the engine's upper load limit. A commercially available engine simulation software (GT-PowerÖ) coupled to the University of Michigan HCCI combustion and heat transfer correlations was used to model a 4-cylinder boosted HCCI engine with three different boosting configurations: turbocharging, supercharging and series turbocharging. The scope of this study is to identify the best boosting approach in order to extend the HCCI engine's operating range. The results of this study are consistent with the literature: Boosting helps increase the HCCI upper load limit, but matching of turbochargers is a problem. In addition, the low exhaust gas enthalpy resulting from HCCI combustion leads to high pressures in the exhaust manifold increasing pumping work. The series turbocharging strategy appears to provide the largest load range extension.
Journal Article

Review of Soot Deposition and Removal Mechanisms in EGR Coolers

2010-04-12
2010-01-1211
Exhaust gas recirculation (EGR) coolers are commonly used in diesel engines to reduce the temperature of recirculated exhaust gases in order to reduce NOX emissions. Engine coolant is used to cool EGR coolers. The presence of a cold surface in the cooler causes fouling due to particulate soot deposition, condensation of hydrocarbon, water and acid. Fouling experience results in cooler effectiveness loss and pressure drop. In this study, possible soot deposition mechanisms are discussed and their orders of magnitude are compared. Also, probable removal mechanisms of soot particles are studied by calculating the forces acting on a single particle attached to the wall or deposited layer. Our analysis shows that thermophoresis in the dominant mechanism for soot deposition in EGR coolers and high surface temperature and high kinetic energy of soot particles at the gas-deposit interface can be the critical factor in particles removal.
Technical Paper

The Effects of CO, H2, and C3H6 on the SCR Reactions of an Fe Zeolite SCR Catalyst

2013-04-08
2013-01-1062
Selective Catalytic Reduction (SCR) catalysts used in Lean NOx Trap (LNT) - SCR exhaust aftertreatment systems typically encounter alternating oxidizing and reducing environments. Reducing conditions occur when diesel fuel is injected upstream of a reformer catalyst, generating high concentrations of hydrogen (H₂), carbon monoxide (CO), and hydrocarbons to deNOx the LNT. In this study, the functionality of an iron (Fe) zeolite SCR catalyst is explored with a bench top reactor during steady-state and cyclic transient SCR operation. Experiments to characterize the effect of an LNT deNOx event on SCR operation show that adding H₂ or CO only slightly changes SCR behavior with the primary contribution being an enhancement of nitrogen dioxide (NO₂) decomposition into nitric oxide (NO). Exposure of the catalyst to C₃H₆ (a surrogate for an actual exhaust HC mixture) leads to a significant decrease in NOx reduction capabilities of the catalyst.
Journal Article

Understanding the Dynamic Evolution of Cyclic Variability at the Operating Limits of HCCI Engines with Negative Valve Overlap

2012-04-16
2012-01-1106
An experimental study is performed for homogeneous charge compression ignition (HCCI) combustion focusing on late phasing conditions with high cyclic variability (CV) approaching misfire. High CV limits the feasible operating range and the objective is to understand and quantify the dominating effects of the CV in order to enable controls for widening the operating range of HCCI. A combustion analysis method is developed for explaining the dynamic coupling in sequences of combustion cycles where important variables are residual gas temperature, combustion efficiency, heat release during re-compression, and unburned fuel mass. The results show that the unburned fuel mass carries over to the re-compression and to the next cycle creating a coupling between cycles, in addition to the well known temperature coupling, that is essential for understanding and predicting the HCCI behavior at lean conditions with high CV.
Technical Paper

A Visualization Test Setup for Investigation of Water-Deposit Interaction in a Surrogate Rectangular Cooler Exposed to Diesel Exhaust Flow

2012-04-16
2012-01-0364
Exhaust gas recirculation (EGR) coolers are commonly used in diesel engines to reduce the temperature of recirculated exhaust gases in order to reduce NOx emissions. The presence of a cool surface in the hot exhaust causes particulate soot deposition as well as hydrocarbon and water condensation. Fouling experienced through deposition of particulate matter and hydrocarbons results in degraded cooler effectiveness and increased pressure drop. In this study, a visualization test setup is designed and constructed so that the effect of water condensation on the deposit formation and growth at various coolant temperatures can be studied. A water-cooled surrogate rectangular channel is employed to represent the EGR cooler. One side of the channel is made of glass for visualization purposes. A medium duty diesel engine is used to generate the exhaust stream.
Technical Paper

Macroscopic Study of Projected Catalytic Converter Requirements

2013-04-08
2013-01-1286
Software packages including Argonne National Lab's Greenhouse Gases, Regulated Emissions, and Energy Use in Transportation (GREET) model and the EPA's Motor Vehicle Emissions Simulation (MOVES) model are useful in analyzing the emission profiles of light-duty vehicles. In particular, GREET performs a detailed life cycle fuel energy and emissions analysis, while MOVES focuses on energy and emissions during vehicle operation. This study uses MOVES2010b in the creation of emission trends in order to predict future emissions regulations and the subsequent aftertreatment device areas of improvement required to meet these standards. A second objective was to create four time sheet tables in order to update the base vehicle operation emission profiles used in GREET. The simulation results depict the balance between nitrous oxide and hydrocarbon emissions, the dependency upon climate effects, and areas for potential improvement given recent engine design trends.
Technical Paper

Optical and Infrared In-Situ Measurements of EGR Cooler Fouling

2013-04-08
2013-01-1289
The use of exhaust gas recirculation (EGR) in internal combustion engines has significant impacts on combustion and emissions. EGR can be used to reduce in-cylinder NOx production, reduce emitted particulate matter, and enable advanced forms of combustion. To maximize the benefits of EGR, the exhaust gases are often cooled with on-engine liquid to gas heat exchangers. A common problem with this approach is the build-up of a fouling layer inside the heat exchanger due to thermophoresis and condensation, reducing the effectiveness of the heat exchanger in lowering gas temperatures. Literature has shown the effectiveness to initially drop rapidly and then approach steady state after a variable amount of time. The asymptotic behavior of the effectiveness has not been well explained. A range of theories have been proposed including fouling layer removal, changing fouling layer properties, and cessation of thermophoresis.
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