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Increasing interest in biofuels—specifically, biodiesel as a pathway to energy diversity and security—have necessitated the need for research on the performance and utilization of these fuels and fuel blends in current and future vehicle fleets. One critical research area is related to achieving a full understanding of the impact of biodiesel fuel blends on advanced emission control systems. In addition, the use of biodiesel fuel blends can degrade diesel engine oil performance and impact the oil drain interval requirements. There is limited information related to the impact of biodiesel fuel blends on oil dilution. This paper assesses the oil dilution impacts on an engine operating in conjunction with a diesel particle filter (DPF), oxides of nitrogen (NOx) storage, a selective catalytic reduction (SCR) emission control system, and a 20% biodiesel (soy-derived) fuel blend.

This paper describes the set-up and testing of a single cylinder 25cc, air cooled, 4-stroke Spark Ignition (SI) engine converted to run in Homogeneous Charge Compression Ignition (HCCI) mode with the aid of various combustion control systems. The combustion control systems were investigated regarding their effects on combustion stability and heat release phasing. Engine operation was compared with unique findings from previous work done on a very small 2-stroke HCCI engine. HCCI engine operation was possible between 1000 - 4000 rpm when using Diethyl Ether (DEE) as the test fuel. Maximum operational fuel-air equivalence ratio (Φ) was 0.75 when operating without Exhaust Gas Recirculation (EGR). This relatively high equivalence ratio was attainable due to thermal gradients induced by the high surface area to volume ratio of the small engine combustion chamber, resulting in high chamber heat transfer.

Controlled Autoignition (CAI) is a very promising technology for simultaneous reduction of fuel consumption and engine-out emissions [3, 4, 9, 16]. But the operating range of this combustion mode is limited on the one hand by high pressure gradients with the subsequent occurrence of knocking, increasing NOX-emissions and cyclic variations, and on the other hand by limited operating stability due to low mixture temperatures. At higher loads the required amount of internal EGR decrease to reach self-ignition conditions decrease and hence the influence of the ignition spark gain. The timing of the ignition spark highly influence the combustion process at higher loads. With the ignition spark, pre-reactions are initialized with a defined heat release. Thus the location of inflammation and flame propagation can be strongly influenced and cyclic variations at higher loads can be reduced.

The continual reduction of diesel engine heavy-duty nitrous oxides and particulate matter emissions due to Environmental Protection Agency (EPA) regulations has resulted in significant changes to engine hardware since 1998. Such changes have included use of cooled exhaust gas recirculation, clean gas induction, oxidation catalysts, variable geometry turbochargers, lean nitrous oxide traps, urea selective catalytic reduction, passive and catalyzed particulate matter filters, and engine design changes to reduce oil consumption while allowing use of low sulfur diesel fuel (DF-2) and maintaining oil change intervals and subsystem durability levels of previous model years. The net result from a propulsion system perspective is increased heat rejection, additional induction and exhaust system volume, increased system weight, and less tolerance to military fuels and lubricants.

It is generally accepted that emissions of nitrogen oxides (NOx) increase as the volume fraction of bio diesel increases in blends with conventional diesel fuel. While many mechanisms based on bio diesel effects on in-cylinder processes have been proposed to explain this observation, a clear understanding of the relative importance of each has remained elusive. To gain further insight into the cause(s) of the bio diesel NOx increase, experiments were conducted in a single-cylinder version of a heavy-duty diesel engine with extensive optical access to the combustion chamber. The engine was operated using two bio diesel fuels and two hydrocarbon reference fuels, over a wide range of loads, and using undiluted air as well as air diluted with simulated exhaust gas recirculation.

Hydrogen has been largely proposed as a possible alternative fuel for internal combustion engines. Its wide flammability range allows higher engine efficiency with leaner operation than conventional fuels, for both reduced toxic emissions and no CO2 gases. Independently, Homogenous Charge Compression Ignition (HCCI) also allows higher thermal efficiency and lower fuel consumption with reduced NOX emissions when compared to Spark-Ignition (SI) engine operation. For HCCI combustion, a mixture of air and fuel is supplied to the cylinder and autoignition occurs from compression; engine is operated throttle-less and load is controlled by the quality of the mixture, avoiding the large fluid-dynamic losses in the intake manifold of SI engines. HCCI can be induced and controlled by varying the mixture temperature, either by Exhaust Gas Recirculation (EGR) or intake air pre-heating.

The paper will discuss the design and development of heavy-duty diesel engines to meet the US EPA 2010 on-highway standards - 0.2 g/HP-hr NOx and 0.01 g/HP-hr particulate matter (PM). In meeting these standards a combination of in-cylinder control and aftertreatment control for both NOx and particulate has been used. For NOx control, a combination of cooled exhaust gas recirculation (EGR) and selective catalytic reduction (SCR) is used. The SCR catalyst uses copper zeolite to achieve high levels of NOx conversion efficiency with minimal ammonia slip and unparalleled thermal durability. For particulate control, a diesel particulate filter (DPF) with upstream oxidation catalyst (DOC) is used. While the DPF may be actively regenerated when required, it operates predominantly with passive regeneration - enabled by the high NOx levels between the engine and the DPF, associated with high efficiency SCR systems and NO₂ production across the DOC.

Diesel exhaust aftertreatment systems are required for meeting both EPA 2010 and final Tier 4 emission regulations while meeting the stringent packaging constraints of the vehicle. The aftertreatment system for this study consists of a fuel dosing system, mixing elements, fuel reformer, lean NOx trap (LNT), diesel particulate filter (DPF), and a selective catalytic reduction (SCR) catalyst. The fuel reformer is used to generate hydrogen (H₂) and carbon monoxide (CO) from injected diesel fuel. These reductants are used to regenerate and desulfate the LNT catalyst. NOx emissions are reduced using the combination of the LNT and SCR catalysts. During LNT regeneration, ammonia (NH₃) is intentionally released from the LNT and stored on the downstream SCR catalyst to further reduce NOx that passed through the LNT catalyst. This paper addresses system packaging and exhaust flow optimization for heavy-duty line-haul and severe service applications.

The removal of soot in the lubricating sumps of diesel engines is a formidable task, further compounded by the introduction of Exhaust Gas Recirculation (EGR). Efficient removal of soot would help ensure engine durability and engine performance while increasing oil drain intervals thus reducing maintenance costs. This paper describes a method by which soot can be separated from the oil with the application of an electric field by utilizing the small electrical charge on the soot particles. The electric field is applied to a network of electrodes that support an open porous network which stabilizes the weakly bound soot cake. Significantly higher filtration efficiency was achieved as compared to mechanical particulate filtration and centrifugation. The paper also discusses the controlling conditions while detailing the performance testing at both a bench scale level and pilot scale level.

The soot distribution as function of ambient O₂ mole fraction in a heavy-duty diesel engine was investigated at low load (6 bar IMEP) with laser-induced incandescence (LII) and natural luminosity. A Multi-YAG laser system was utilized to create time-resolved LII using 8 laser pulses with a spacing of one CAD with detection on an 8-chip framing camera. It is well known that the engine-out smoke level increases with decreasing oxygen fraction up to a certain level where it starts to decrease again. For the studied case the peak occurred at an O₂ fraction of 11.4%. When the oxygen fraction was decreased successively from 21% to 9%, the initial soot formation moved downstream in the jet. At the lower oxygen fractions, below 12%, no soot was formed until after the wall interaction. At oxygen fractions below 11% the first evidence of soot is in the recirculation zone between two adjacent jets.

An experimental study was performed to develop a more fundamental understanding of the effects of secondary air injection (SAI) on exhaust gas emissions and catalyst light-off characteristics during cold start of a modern SI engine. The effects of engine operating parameters and various secondary air injection strategies such as spark retardation, fuel enrichment, secondary air injection location and air flow rate were investigated to understand the mixing, heat loss, and thermal and catalytic oxidation processes associated with SAI. Time-resolved HC, CO and CO₂ concentrations were tracked from the cylinder exit to the catalytic converter outlet and converted to time-resolved mass emissions by applying an instantaneous exhaust mass flow rate model. A phenomenological model of exhaust heat transfer combined with the gas composition analysis was also developed to define the thermal and chemical energy state of the exhaust gas with SAI.

The introduction of alternative fuels is crucial to limit greenhouse gases. CNG is regarded as one of the most promising clean fuels given its worldwide availability, its low price and its intrinsic properties (high knocking resistance, low carbon content...). One way to optimize dedicated natural gas engines is to improve the CNG slow burning velocity compared to gasoline fuel and allow lean burn combustion mode. Besides optimization of the combustion chamber design, hydrogen addition to CNG is a promising solution to boost the combustion thanks to its fast burning rate, its wide flammability limits and its low quenching gap. This paper presents an investigation of different methane/hydrogen blends between 0% and 40 vol. % hydrogen ratio for three different combustion modes: stoichiometric, lean-burn and stoichiometric with EGR.

A spark-assist homogeneous charge compression ignition (SA-HCCI) operating strategy is presented here that allows for stoichiometric combustion from 1000-3000 rpm, and at loads as high as 750 kPa net IMEP. A single cylinder gasoline engine equipped with direct fuel injection and fully variable hydraulic valve actuation (HVA) is used for this experimental study. The HVA system enables negative valve overlap (NVO) valve timing for hot internal EGR. Spark-assist stabilizes combustion over a wide range of engine speeds and loads, and allows for stoichiometric operation at all conditions. Characteristics of both spark-ignited combustion and HCCI are present during the SA-HCCI operating mode, with combustion analysis showing a distinctive spark ignited phase of combustion, followed by a much more rapid HCCI combustion phase. At high load, the maximum cylinder pressure rise rate is controlled by a combination of spark timing and retarding the intake valve closing angle.

Turbulent Jet Ignition is an advanced spark-initiated pre-chamber combustion system for an otherwise standard spark ignition engine found in current on-road vehicles. This next-generation pre-chamber design simply replaces the spark plug in a conventional spark ignition engine. Turbulent Jet Ignition enables very fast burn rates due to the ignition system producing multiple, widely distributed ignition sites, which consume the main charge rapidly. This high energy ignition system results from the partially combusted (reacting) prechamber products initiating main chamber combustion. The fast burn rates allow for increased levels of dilution (lean burn and/or EGR) when compared to conventional spark ignition combustion, with dilution levels being comparable to other low temperature combustion technologies (HCCI) without the complex control drawbacks.

Initial results are presented for the production of hydrogen from waste lubricating oil using a chemical looping reforming (CLR) process. The development of flexible and sustainable sources of hydrogen will be required to facilitate a "hydrogen economy." The novel CLR process presented in this paper has an advantage over hydrogen production from conventional steam reforming because CLR can use complex, low value, waste oils. Also, because the process is scalable to small and medium size, hydrogen can be produced close to where it is required, minimizing transport costs. Waste lubricating oil typically contains 13-14% weight of hydrogen, which through the steam reforming process could produce a syngas containing around 75 vol% H₂, representing over 40 wt% of the fuel. The waste oil was converted to a hydrogen-rich syngas in a packed bed reactor, using a Ni/ Al₂O₃ catalyst as the oxygen transfer material (OTM).

To meet increasingly stringent diesel exhaust emissions requirements, original equipment manufacturers (OEMs) have introduced common rail fuel injection systems that develop pressures of up to 2000 bar (30,000 psi). In addition, fuel delivery schemes have become more complicated, often involving multiple injections per cycle. Containing higher pressures and allowing for precise metering of fuel requires very tight tolerances within the injector. These changes have made injectors more sensitive to fuel particulate contamination. Recently, problems caused by internal diesel injector deposits have been widely reported. In this paper, the results of an investigation into the chemical nature and probable sources of these deposits are discussed. Using an array of techniques, internal deposits were analyzed from on a number of sticking injectors from the field and from OEM test stands in North America.

Prior technical work by various OEMs and lubricant formulators has identified lubricant-derived phosphorus as a key element capable of significantly reducing the efficiency of modern emissions control systems of gasoline-powered vehicles ( 1 , 2 , 3 , 4 , 5 , 6 , 7 , 8 , 9 , 10 , 11 , 12 , 13 ). However, measuring the exact magnitude of the detriment is not simple or straightforward exercise due to the many other sources of variation which occur as a vehicle is driven and the catalyst is aged ( 1 ). This paper, the second one in the series of publications, examines quantitative sets of results generated using various vehicle and exhaust catalyst testing methodologies designed to follow the path of lubricant-derived phosphorous transfer from oil sump to exhaust catalytic systems ( 1 ).

Turbulent Jet Ignition is an advanced spark-initiated pre-chamber combustion system for an otherwise standard spark ignition engine found in current on-road vehicles. This next-generation pre-chamber design simply replaces the spark plug in a conventional spark ignition engine. Turbulent Jet Ignition enables very fast burn rates due to the ignition system producing multiple, widely distributed ignition sites, which consume the main charge rapidly. This high energy ignition system results from the partially combusted (reacting) pre-chamber products initiating main chamber combustion. The fast burn rates allow for increased levels of dilution (lean burn and/or EGR) when compared to conventional spark ignition combustion, with dilution levels being comparable to other low temperature combustion technologies (HCCI) without the complex control drawbacks.

Lean NOx Trap (LNT) catalysts can effectively reduce NOx from lean engine exhaust. Significant research for LNTs in diesel engine applications has been performed and has led to commercialization of the technology. For lean gasoline engine applications, advanced direct injection engines have led to a renewed interest in the potential for lean gasoline vehicles and, thereby, a renewed demand for lean NOx control. To understand the gasoline-based reductant chemistry during regeneration, a BMW lean gasoline vehicle has been studied on a chassis dynamometer. Exhaust samples were collected and analyzed for key reductant species such as H₂, CO, NH₃, and hydrocarbons during transient drive cycles. The relation of the reductant species to LNT performance will be discussed. Furthermore, the challenges of NOx storage in the lean gasoline application are reviewed.

The application of accelerated catalyst aging procedures on an engine dynamometer test bed for the purpose of demonstrating catalyst durability is examined. A proof-of-principle approach is followed using catalysts from vehicles certified to U.S. Tier 2 Bin 4 and California SULEV 2 levels. Accelerated durability demonstration methods based upon conventional fuel cut cycles were employed to age catalysts to levels predicted by quantification of thermal catalyst bed severity on the Standard Road Cycle (SRC) relative to the fuel cut aging cycle using the Bench Aging Time (BAT) equation. Emissions deterioration on the accelerated aging cycle is compared to the automobile manufacturers' certification values and to whole vehicle emissions performance results from several different in-use vehicle fleets. The influence of technology on whole vehicle emissions levels and deterioration characteristics is also evaluated.