Search Results

Alternative and renewable fuels show tremendous promise for addressing concerns of energy security, energy supply, and CO₂ emissions. However, the new fuels have the potential to produce non-regulated exhaust components that may be as detrimental or worse, than currently regulated emissions components. For the 2009 SAE Clean Snowmobile Challenge (CSC), a commercially available Fourier Transform Infrared (FTIR) spectrometer was used to sample raw exhaust from eight student teams' snowmobiles for comparative analysis with a conventional emissions bench. The levels of CO₂, CO, NO , O₂, and THC were compared for the five operating modes, which included both gasoline- and diesel-powered snowmobiles. The fuel was either an ethanol blend for spark-ignition engines or a biodiesel for compression-ignition engines. Final emissions result scores varied by less than 2% between the conventional emissions bench and the FTIR.

An operational scheme with fuel-lean and exhaust gas dilution in spark-ignited engines increases thermal efficiency and decreases NOx emission, while these operations inherently induce combustion instability and thus large cycle-to-cycle variation in engine. In order to stabilize combustion variations, the development of an advanced ignition system is becoming critical. To quantify the impact of spark-ignition discharge, ignitability tests were conducted in an optically accessible combustion vessel to characterize the flame kernel development of lean methane-air mixture with CO₂ simulating exhaust diluent. A shrouded fan was used to generate turbulence in the vicinity of J-gap spark plug and a Variable Output Ignition System (VOIS) capable of producing a varied set of spark discharge patterns was developed and used as an ignition source. The main feature of the VOIS is to vary the secondary current during glow discharge including naturally decaying and truncated with multiple strikes.

This paper studies the bi-directional power flow control between Plug-in Electric Vehicles (PEVs) and an electrical grid. A grid-tied charging system that enables both Grid-to-Vehicle (G2V) and Vehicle-to-Grid (V2G) charging/discharging is modeled using SimPowerSystems in Matlab/Simulink environment. A bi-directional AC-DC converter and a bi-directional DC-DC buck-boost converter are integrated to charge and discharge PEV batteries. For AC-DC converter control, Predictive Current Control (PCC) strategy is employed to enable grid current to reach a reference current after one modulation period. In addition, Phase Lock Loop (PLL) and a band-stop filter are designed to lock the grid voltage phase and reduce harmonics. Bi-directional power flow is realized by controlling the mode of the DC-DC converter. Simulation tests are conducted to evaluate the performance of this bi-directional charging system.

Interest in natural gas as an alternative fuel source to petroleum fuels for light-duty vehicle applications has increased due to its domestic availability and stable price compared to gasoline. With its higher hydrogen-to-carbon ratio, natural gas has the potential to reduce engine out carbon dioxide emissions, which has shown to be a strong greenhouse gas contributor. For part-load conditions, the lower flame speeds of natural gas can lead to an increased duration in the inflammation process with traditional port-injection. Direct-injection of natural gas can increase in-cylinder turbulence and has the potential to reduce problems typically associated with port-injection of natural gas, such as lower flame speeds and poor dilution tolerance. A study was designed and executed to investigate the effects of direct-injection of natural gas at part-load conditions.

The vehicle driving cycles affect the performance of a hybrid vehicle control strategy, as a result, the overall performance of the vehicle, such as fuel consumption and emission. By identifying the driving cycles of a vehicle, the control system is able to dynamically change the control strategy (or parameters) to the best one to adapt to the changes of vehicle driving patterns. This paper studies the supervised driving cycle recognition using pattern recognition approach. With pattern recognition method, a driving cycle is represented by feature vectors that are formed by a set of parameters to which the driving cycle is sensitive. The on-line driving pattern recognition is achieved by calculating the feature vectors and classifying these feature vectors to one of the driving patterns in the reference database. To establish reference driving cycle database, the representative feature vectors for four federal driving cycles are generated using feature extraction method.

Diesel combustion and emissions formation is spray and mixing controlled and understanding spray parameters is key to determining the impact of fuel injector operation and nozzle design on combustion and emissions. In this study, both spray visualization and computational fluid dynamics (CFD) modeling were undertaken to investigate key mechanisms for liquid length fluctuations. For the experimental portion of this study a common rail piezoelectric injector was tested in an optically accessible constant volume combustion vessel. Liquid penetration of the spray was determined via processing of images acquired from Mie back scattering under vaporizing conditions by injecting into a charge gas at elevated temperature with a 0% oxygen environment. Tests were undertaken at a gas density of 34.8 kg/m₃, 2000 bar injection pressure, and at ambient temperatures of 900, 1100, and 1300 K.

Recent increases in emissions regulations within the snowmobile industry have led to significant advancements in fuel, exhaust, and control systems on snowmobiles. However, particulate matter is currently an unregulated exhaust component of snowmobile engines. The measurement of dry soot as well as particulate matter from snowmobiles is the focus of this paper. Two industry-representative snowmobiles were chosen for this research which included a 2006 Yamaha Nytro carbureted four-stroke and a 2009 Ski-Doo MX-Z direct-injected two-stroke. Measurements for each snowmobile included gaseous emissions (CO₂, CO, NOx, O₂, and THC), particulate matter collected on quartz filters, and dry soot measured using an AVL Micro Soot Sensor. Each snowmobile was tested over the industry-standard five-mode emissions certification test cycle to determine the emissions, dry soot, and particulate matter levels from idle to wide open throttle (full-load).

Reactivity Controlled Compression Ignition (RCCI) is a promising dual-fuel Low Temperature Combustion (LTC) mode with significant potential for reducing NOx and particulate emissions while improving or maintaining thermal efficiency compared to Conventional Diesel Combustion (CDC) engines. The large reactivity difference between diesel and Natural Gas (NG) fuels provides a strong control variable for phasing and shaping combustion heat release. In this work, the Brake Thermal Efficiencies (BTE), emissions and combustion characteristics of a light duty 1.9L, four-cylinder diesel engine operating in single fuel diesel mode and in Diesel-NG RCCI mode are investigated and compared. The engine was operated at speeds of 1300 to 2500 RPM and loads of 1 to 7 bar BMEP. Operation was limited to 10 bar/deg Maximum Pressure Rise Rate (MPRR) and 6% Coefficient of Variation (COV) of IMEP.

Low Temperature Combustion (LTC) engines are promising to improve powertrain fuel economy and reduce NOx and soot emissions by improving the in-cylinder combustion process. However, the narrow operating range of LTC engines limits the use of these engines in conventional powertrains. Extended range electric vehicles (EREVs), by decoupling the engine from the drivetrain, allows the engine to operate in a limited operating range; thus, EREVs offer an ideal platform for realizing the advantages of LTC engines. In this study, the global optimum fuel economy improvement of an experimentally developed 2-liter multi-mode LTC engine in a series EREV is investigated. The engine operation modes include Homogeneous-Charge Compression Ignition (HCCI), Reactivity Controlled Compression Ignition (RCCI), and conventional Spark Ignition (SI).

The medium and heavy duty vehicle industry has fostered an increase in emissions research with the aim of reducing NOx while maintaining power output and thermal efficiency. This research describes a proof-of-concept numerical study conducted on a Caterpillar single-cylinder research engine. The target of the study is to reduce NOx by taking a unique approach to combustion air handling and utilizing enriched nitrogen and oxygen gas streams provided by Air Separation Membranes. A large set of test cases were initially carried out for closed-cycle situations to determine an appropriate set of operating conditions that are conducive for NOx reduction and gas diffusion properties. Several parameters - experimental and numerical, were considered. Experimental aspects, such as engine RPM, fuel injection pressure, start of injection, spray inclusion angle, and valve timings were considered for the parametric study.

This paper presents results on how the Equivalent Consumption Minimization Strategy (ECMS) penalty factor effects Lithium ion battery aging. The vehicle studied is the Honda Civic Hybrid. The battery used is A123 Systems’. Vehicle simulation using multiple combinations of highway and city drive cycles. For each combination of drive cycles, six ECMS penalty factor values are used. Battery aging is evaluated using a semi-empirical model combined with accumulated Ah-throughput method which uses, as an input, the battery state of charge trajectory from the vehicle simulations. The tradeoff between fuel cost and battery aging cost is explicitly displayed. In addition, the results provide insight into how driving behavior affects battery aging. The paper concludes with a discussion of the optimal balance between fuel cost and battery aging.

The catalyzed particulate filter (CPF), used in conjunction with a diesel oxidation catalyst (DOC) is an important aftertreatment device used to meet Environmental Protection Agency (EPA) heavy-duty diesel emission standards for particulate matter (PM). Numerical modeling of these exhaust after-treatment devices decreases the time and cost of development involved. Modeling CPF active regeneration gives insight into the PM oxidation kinetics, which helps in reducing the regeneration fuel penalty. As seen from experimental data, active regeneration of the CPF results in a significant temperature increase into the CPF (up to 8°C/sec) which affects the oxidation rate of particulate matter (PM). PM oxidation during active regeneration was determined to be a function of filter PM loading, inlet temperature and inlet hydrocarbon concentration.

When testing dynamic structures, it is important to note that the dynamic system in question may be submerged into a fluid during operation and to properly test the structure under the same condition in order to understand the true dynamic parameters of the system. In this way, the mass and stiffness coupling to the particular fluid, for the case of this study, automatic transmission fluid, may be taken into account. This is especially important in light structures where the coupling between the fluid mass and the structural mass may be great. A structure was tested with a laser vibrometer using several impact methods in open air to determine which impact method would be most suitable for submerged testing. The structure was then submerged in transmission fluid with an accelerometer attached and subsequently tested and compared to the previous results.

An experimental study and analysis was conducted to investigate cold start robustness of an ethanol flex-fuel spark ignition (SI) direct injection (DI) engine. Cold starting with ethanol fuel blends is a known challenge due to the fuel characteristics. The program was performed to investigate strategies to reduce the enrichment requirements for the first firing cycle during a cold start. In this study a single-cylinder SIDI research engine was used to investigate gasoline and E85 fuels which were tested with three piston configurations (CR11F, CR11B, CR15.5B - which includes changes in compression ratio and piston geometry), at three intake cam positions (95, 110, 125 °aTDC), and two fuel pressures (low: 0.4 MPa and high: 3.0 MPa) at 25°C±1°C engine and air temperature, for the first cycle of an engine start.

This paper focuses on the development of an Extended Kalman Filter for estimating internal species concentration and storage states of an SCR using NOX and NH₃ sensors. The motivation for this work was twofold. First, knowledge of internal states may be useful for onboard diagnostic strategy development. In particular, significant errors between the outlet NOX or NH₃ sensors, reconstructed from estimated states, and the measured NOX or NH₃ concentrations may aid OBD strategies that attempt to identify particular system failure modes. Second, the EKF described estimates not only stored ammonia but also NO, NO₂ and NH₃ gas concentrations within and exiting the SCR. Exploiting knowledge of the individual species concentrations, instead of lumping them together as NOX, can yield improved closed loop urea controller performance in terms of reduced urea consumption and better NOX conversion.

In this paper, we develop a method for optimizing urea dosing to minimize the downstream readings from a production NOx sensor that has cross-sensitivity to ammonia. This approach favors high NOx conversion and reduced ammonia slip. The motivation for this work is to define a process to identify the maximum selective catalytic reduction SCR performance bounds for a given drive cycle. The approach uses a model structure that has a closed-form optimal solution for the urea injection. Every aftertreatment system has its own, unique model, which must be identified and validated. To demonstrate the approach, a model is identified and validated using experimental SCR input/output NOx sensor data from a 2010 Cummins 6.7L ISB production engine. The optimal control law is then simulated and its performance compared against the simulated performance of the SCR using experimental data for its inlet conditions.

Estimating internal residual during engine operation is essential to robust control during startup, steady state, and transient operation. Internal residual has a significant effect on combustion flame propagation, combustion stability and emissions. Accurate residual estimate also provides a better foundation for optimizing open loop fuel control during startup, while providing a basis for reducing emissions during closed loop control. In this paper we develop an improved model to estimate residual gas fraction by means of isolation and characterization of the physical processes in the gas exchange. Examining existing residuals model as the base, we address their deficiencies making changes to appropriate terms to the model. Existing models do not work well under wide angle dual independent cam phasing. The improved residual estimation model is not limited by the initial data set used for its calibration and does not need cylinder pressure data.

Water spray characterization of a multi-hole injector under pressures and temperatures representative of engine-relevant conditions was investigated for naturally aspirated and boosted engine conditions. Experiments were conducted in an optically accessible pressure vessel using a high-speed Schlieren imaging to visualize the transient water spray. The experimental conditions included a range of injection pressures of 34, 68, and 102 bar and ambient temperatures of 30 - 200°C, which includes flash-boiling and non-flash-boiling conditions. Transient spray tip penetration and spray angle were characterized via image processing of raw Schlieren images using Matlab code. The CONVERGE CFD software was used to simulate the water spray obtained experimentally in the vessel. CFD parameters were tuned and validated against the experimental results of spray profile and spray tip penetration measured in the combustion vessel (CV).

Particular matter (PM) has been greatly concerned over the recent decades due to the constantly increasing restriction on its effect on environmental aspect. Oxygenated fuel such as dimethyl ether (DME) has been known to have beneficial impact on diesel engine emissions in terms of zero soot formation. In current study, under several ambient conditions including surrounding gas temperature and oxygen percentages, soot and emission formation of DME spray is investigated to provide a comparison with other diesel surrogate (n-heptane) and JP-8 surrogate fuels. One important work is to develop a number of chemical kinetic mechanisms with soot chemistry including the growth of polycyclic aromatic hydrocarbon (PAH) and nitro oxides (NOx) formation. Using the developing detailed mechanisms, several numerical approaches were introduced to provide an integrated picture of emission formations.

The effect of fuel changes on diesel oxidation catalyst performance was studied by comparing the physical, chemical and biological character of the particulate emissions using three different fuels. Baseline (uncatalyzed) emissions were also compared for these same fuels. The fuels used for this study were: a typical No. 2 fuel, a No. 1 fuel, and a shale oil-derived diesel fuel. Comparisons of NOX, NO, NO2, HC and particulate mass emissions using each fuel were made using selected modes from the EPA 13 mode cycle. Changes in the chemical and biological character of the soluble organic fraction (SOF) were also studied. Fuel properties, most notably fuel sulfur content, were found to affect the performance of the oxidation catalyst used. Fuel sulfur content should be kept as low as possible if catalytic converters are used on diesel powered equipment.