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Journal Article

Transient Operation and Over-Dilution Mitigation for Low-Pressure EGR Systems in Spark-Ignition Engines

Abstract Low-Pressure cooled Exhaust Gas Recirculation (LP-cEGR) is proven to be an effective technology for fuel efficiency improvement in turbocharged spark-ignition (SI) engines. Aiming to fully exploit the EGR benefits, new challenges are introduced that require more complex and robust control systems and strategies. One of the most important restrictions of LP-cEGR is the transient response, since long air-EGR flow paths introduce significant transport delays between the EGR valve and the cylinders. High dilution generally increases efficiency, but can lead to cycle-by-cycle combustion variation. Especially in SI engines, higher-than-requested EGR dilution may lead to combustion instabilities and misfires. Considering the long EGR evacuation period, one of the most challenging transient events is throttle tip-out, where the engine operation shifts from a high-load point with high dilution tolerance to a low-load point where EGR tolerance is significantly reduced.
Journal Article

A Misfire Detection Index for Four-Stroke Single-Cylinder Motorcycle Engines—Part II: Gap Distance and Gap Slope

Abstract Two new misfire detection indexes for single-cylinder motorcycle engines—dubbed gap distance (GD) and gap slope (GS)—are proposed in this study. GD and GS quantify the change in engine angular acceleration using the tooth time measured by the crankshaft position sensor (CKPS). GD is defined as the product of the spacing distance I (the distance from the top dead center at the explosion stroke [TDC2] to the engine speed trend line parallel to the engine speed axis) and spacing distance II (the distance from the bottom dead center at the expansion stroke [BDC2] to the engine speed trend line parallel to the engine speed axis). GS is defined as the difference between the two slopes between the engine speed inclination line and the engine speed trend line. Here the engine speed trend line connects two engine speeds at the top dead center at the intake stroke (TDC1) of the current and subsequent cycles.
Journal Article

Optimization of a High-Speed Dual-Fuel (Natural Gas-Diesel) Compression Ignition Engine for Gen-sets

Abstract The goal of this study is to develop a clean and efficient thermal unit for a generator set (gen-set) rated at 80 kW, exploring the potential of Dual-Fuel (DF) combustion (Natural Gas-Diesel) on high-speed Compression Ignition (CI) engines. Typically, the most comparable commercial gen-sets are made up of Heavy-Duty (HD) Diesel engines, whose cost and complexity will probably increase to meet more stringent emissions standards. The conversion of a light-duty Diesel engine may permit to match the high efficiency of Diesels with the low emissions of DF combustion at an affordable cost. Moreover, the new thermal unit would be more compact and lighter. Running on Natural Gas (NG) is less expensive than using Diesel fuel, and it offers more opportunities to reduce the environmental impact (e.g., NG can be easily obtained from biomass, in the same site where the gen-set is installed).
Journal Article

Homogeneous Charge with Direct Injection Strategy to Achieve High Efficiency and Clean Combustion in Diesel Engines

Abstract Reactivity-Controlled Compression Ignition (RCCI) has emerged as the most promising strategy to achieve high efficiency and clean combustion in diesel engines without any compromise on the achievable load range. Nevertheless, the complexity of the system hardware due to dual fueling and higher unburned fuel emissions are the major challenges to be addressed in RCCI. Although various approaches are proposed in the literature to reduce higher unburned emissions in RCCI, single-fuel strategies without any reactivity stratification that result in higher thermal efficiency and lower unburned emissions are not available. In the present work, a single-fuel novel Homogeneous Charge with Direct Injection (HCDI) strategy is proposed to address the limitations of RCCI in terms of higher unburned emissions.
Journal Article

A Novel Durability Analysis Approach for High-Pressure Die Cast Aluminum Engine Block

Abstract Lightweight and high-strength high-pressure die casting (HPDC) aluminum has been widely used in automotive components such as the cylinder block, lower crankcase extension, transmission case, and drive unit. Die cast parts have good surface finishes with relatively higher material strength in the casting skin than the center core material, maintain consistent features and tolerance, and maximize metal yield, therefore making it the most cost-effective casting process for mass production of aluminum parts. However, due to the rapid filling rates, the HPDC process tends to form large porosity and oxides because of the entrapped gas and solidification shrinkage, thereby deteriorating the mechanical properties of the casting parts.
Journal Article

The Synergies of Valve Overlap Reduction and External Exhaust Gas Recirculation Dilution at Boosted Loads of a Downsized Gasoline Turbo Direct Injection Engine

Abstract Uncertainty of fuel reserves, environmental crisis, and health concerns arise from transport demands and reliance on fossil fuels. Downsized gasoline turbocharged direct injection (GTDI) engines have been developed and applied to most modern gasoline vehicles, delivering superior efficiency in high-load operation, reduced friction, and weight. But fuel enrichment and late combustion phasing to mitigate knocking combustion have hindered the efficiency benefits at higher loads with high boost. Furthermore, the wide valve-overlap with a three-cylinder setup for the maximum scavenging efficiency produces bursts of short-circuit (SC) air to cause underestimation of the equivalence ratio by the oxygen sensor, resulting in higher tailpipe nitrogen oxides (NOx) emissions with three-way catalyst (TWC) exhaust aftertreatment. Reducing the valve overlap to limit short-circuiting and enrichment will recover the combustion efficiency and the engine ER, but at the cost of high knock onset.
Journal Article

Indoor Measurements of Tire and Road Data—Applications to Durability Loads Prediction

Abstract Road test is hitherto the most common approach to assess vehicle durability and structural performance. Moreover, the measurements serve as the final validation of the road load simulation, which is currently widely used in vehicle development cycles. The virtual simulation requires digitized road surfaces, a suitable tire model, and suspension model. The whole procedure is time consuming for outdoor measurements and costly to automotive OEMs for road modeling, tire model parametrization, and the like. However, the respective error from each subsystem model keep uncertain during the whole vehicle simulation. Meanwhile, quantitative evaluation of the simulation quality is always tough to conduct due to variability of measurements and limited test configurations. To overcome such challenges, a new approach with higher operational feasibility for the acquisition of durability loads at wheel rim was proposed.
Journal Article

Permanent Magnet Direct Current Motor Thermal Simulation to Predict Its Temperature Rise during Eaton Automotive Rear Axle Differential Operation

Abstract Eaton’s automotive rear axle differential is used in vehicles to improve stability while experiencing variable road conditions. It adjusts the power ratio between wheels to reduce wheel spin and add understeer. A Permanent Magnet Direct Current (PMDC) motor is used to develop hydraulic pressure, which is converted into a bias torque across the axle. Heat generated in a PMDC motor during transient operation can affect its torque output due to changes in current. The variation in motor torque can impact the rate at which hydraulic pressure is developed. Because of this, the differential performance can be affected. A three-dimensional (3D) transient numerical simulation methodology has been developed to predict temperature rise at critical PMDC motor locations when subjected to a transient duty cycle. Heat load required for simulation is calculated using motor current and efficiency curve, thereby eliminating multi-physics simulation.
Journal Article

A Comparative Study of Directly Injected, Spark Ignition Engine Combustion and Energy Transfer with Natural Gas, Gasoline, and Charge Dilution

Abstract This article presents an investigation of energy transfer, flame propagation, and emissions formation mechanisms in a four-cylinder, downsized and boosted, spark ignition engine fuelled by either directly injected compressed natural gas (DI CNG) or gasoline (GDI). Three different charge preparation strategies are examined for both fuels: stoichiometric engine operation without external dilution, stoichiometric operation with external exhaust gas recirculation (EGR), and lean burn. In this work, experiments and engine modelling are first used to analyze the energy transfer throughout the engine system. This analysis shows that an early start of fuel injection (SOI) improves fuel efficiency through lower unburned fuel energy at low loads with stoichiometric DI CNG operation.
Journal Article

Gear Shift Quality Parameters Optimization for Critical to Quality Dimensions

Abstract Gear Shift Quality (GSQ) in passenger cars is one of the sensitive touch points, which has a direct effect on driver fatigue and drivability. In the following article, an attempt has been made to study the variance in Critical to Quality (CTQ) dimensions and their influence on GSQ parameters. CTQ matrix that shows relation between CTQ parameters and GSQ parameters is formed and is analyzed to study process capability. Impact of variance in CTQs on GSQ parameters is studied and finally has resulted intoaTolerance revisionbRemoval of C of C symbol from drawing wherever is required In an automobile transmission, the driver’s comfort of smooth shifting and selection of gears is a major concern for the transmission designer. Apart from smoother shifting and selection of gears while driving, the overall gearshift quality is also important for the transmission designer, which has a direct impact on customer delight.
Technical Paper

CFD Numerical Reconstruction of the Flash Boiling Gasoline Spray Morphology

The numerical reconstruction of the liquid jet generated by a multi-hole injector, operating in flash-boiling conditions, has been developed by means of a Eulerian- Lagrangian CFD code and validated thanks to experimental data collected with schlieren and Mie scattering imaging techniques. The model has been tested with different injection parameters in order to recreate various possible engine thermodynamic conditions. The work carried out is framed in the growing interest present around the gasoline direct-injection systems (GDI). Such technology has been recognized as an effective way to achieve better engine performance and reduced pollutant emissions. High-pressure injectors operating in flashing conditions are demonstrating many advantages in the applications for GDI engines providing a better fuel atomization, a better mixing with the air, a consequent more efficient combustion and, finally, reduced tailpipe emissions.
Technical Paper

Surrogate Fuel Formulation to Improve the Dual-Mode Dual-Fuel Combustion Operation at Different Operating Conditions

Dual-mode dual-fuel combustion is a promising combustion concept to achieve the required emissions and CO2 reductions imposed by the next standards. Nonetheless, the fuel formulation requirements are stricter than for the single-fuel combustion concepts as the combustion concept relies on the reactivity of two different fuels. This work investigates the effect of the low reactivity fuel sensitivity (S=RON-MON) and the octane number at different operating conditions representative of the different combustion regimes found during the dual-mode dual-fuel operation. For this purpose, experimental tests were performed using a PRF 95 with three different sensitivities (S0, S5 and S10) at operating conditions of 25% load/950 rpm, 50%/1800 rpm and 100%/2200 rpm. Moreover, air sweeps varying ±10% around a reference air mass were performed at 25%/1800 rpm and 50%/1800 rpm. Conventional diesel fuel was used as high reactivity fuel in all the cases.
Technical Paper

Narrow-Throat Pre-Chamber Combustion with Ethanol, a Comparison with Methane

With increasingly stringent emissions regulations, the use of pre-chamber combustion systems is gaining popularity in Internal Combustion Engines (ICE). The advantages of pre-chambers are well established, such as improving fuel economy by increasing the lean limit and reducing emissions, particularly NOX. In pre-chamber combustion, flame jets shoot out from the pre-chamber orifices into the main chamber, generating several ignition points that promote a rapid burn rate of the lean mixture (excess-air ratio (λ) >1) in the main chamber. This work studies the effects of using two different fuels in the main chamber and assesses the lean limit, the combustion efficiency (ηc), and the emissions of a single-cylinder heavy-duty engine equipped with a narrow-throat active pre-chamber. Ethanol (C2H5OH) was tested in the main chamber while keeping the pre-chamber fueled with methane (CH4), and the results were then compared to using methane as the sole fuel.
Journal Article

Automated Diagnosis of Engine Misfire Faults Using Combination Classifiers

Abstract Existing on-board diagnostics vehicle systems can detect the existence of faults, but their diagnostic (fault isolation) capabilities are rather low. Extensions to on-board diagnostics are needed in order to provide a high degree of automated diagnostic support. In this context, we study in this article the problem of internal combustion engine misfires, which constitute a class of automotive faults known to be difficult to diagnose, and present a combination classifier that has excellent performance in classifying the various root causes of misfire faults. We first obtained real-life data and built a database consisting of 2,299 time instances of actual misfire and misfire-free cases. Fault data were captured on several different vehicle makes and models, with each misfire fault belonging to one of three different categories (air-intake, coil-ignition, and fuel-injection), further subdivided into a total of seven subcategories.
Journal Article

Fueling an Engine by Ultrasonic Atomization, and Its Control

Abstract This article presents work carried out on a small, 4-stroke, SI engine, incorporated with an ultrasonic atomizer-based fueling system. A disc-type ultrasonic atomizer having good atomization characteristics was incorporated in the air intake path of a single cylinder, two-wheeler engine, replacing the conventional carburetor. This new fueling system was introduced with the aim of reducing the engine fuel consumption, while looking for a possible reduction in exhaust emissions. An electronic control mechanism was devised to change the atomization rate, in order to set the desired equivalence ratio for optimum engine operation. Test results indicate a significant improvement in fuel consumption and brake thermal efficiency, with a good control over the equivalence ratio. The system also allows engine operation at equivalence ratios as low as 0.5, and hence could be adopted for ultra-lean engines.
Technical Paper

Simulation-Based Evaluation of Spark-Assisted Compression Ignition Control for Production

Spark-assisted compression ignition (SACI) leverages flame propagation to trigger autoignition in a controlled manner. The autoignition event is highly sensitive to several parameters, and thus, achieving SACI in production demands a high tolerance to variations in conditions. Limited research is available to quantify the combustion response of SACI to these variations. A simulation study is performed to establish trends, limits, and control implications for SACI combustion over a wide range of conditions. The operating space was evaluated with a detailed chemical kinetics model. Key findings were synthesized from these results and applied to a 1-D engine model. This model identified performance characteristics and potential actuator positions for a production-viable SACI engine. This study shows charge preparation is critical and can extend the low-load limit by strengthening flame propagation and the high-load limit by reducing ringing intensity.
Technical Paper

Analytical Approach to Characterize the Effect of Engine Control Parameters and Fuel Properties on ACI Operation in a GDI Engine

Advanced compression ignition (ACI) operation in gasoline direct injection (GDI) engines is a promising concept to reduce fuel consumption and emissions at part load conditions. However, combustion phasing control and the limited operating range in ACI mode are a perennial challenge. In this study the combined impact of fuel properties and engine control strategies in ACI operation are investigated. A design of experiments method was implemented using a three level orthogonal array to determine the sensitivity of engine control parameters on the engine load, combustion noise and stability under low load ACI operation for three RON 98 gasoline fuels, each exhibiting disparate chemical composition. Furthermore, the thermodynamic state of the compression histories was studied with the aid of the pressure-temperature framework.
Journal Article

Method to Compensate Fueling for Individual Firing Events in a Four-Cylinder Engine Operated with Dynamic Skip Fire

Cylinder deactivation in multicylinder spark-ignition (SI) engines leads to increased fuel efficiency at part load by allowing fired cylinders to operate closer to their peak thermal efficiency compared to all-cylinder operation. Unlike traditional cylinder deactivation strategies that are limited to deactivating only certain cylinders, Dynamic Skip Fire (DSF) is an advanced cylinder deactivation control strategy that makes deactivation decisions for every cylinder on an individual firing opportunity basis to best meet driver torque demand while saving fuel and mitigating noise, vibration, and harshness (NVH). During DSF operation, inducted charge air mass can vary for each firing event due to the firing sequence history. To maximize efficiency, cylinder fueling should be adjusted for each firing event in DSF based on the inducted charge air mass for that event.
Technical Paper

Simultaneous Control Optimization of Variable-Geometry Turbocharger and High Pressure EGR on a Medium Duty Diesel Engine

This research examines the interdependence of the control strategies of a high-pressure exhaust gas recirculation (HP-EGR) and a variable geometry turbocharger (VGT) on a medium-duty diesel engine in transient load operation. The effect on fuel economy, particulate and NO production were investigated through multiple tests of synchronously controlled VGT and EGR positions. An optimal steady-state strategy of the above determinants was defined as a function of the VGT’s boost pressure and EGR percent mass. The optimal steady-state strategy was then used to investigate the interdependence of the VGT and HP-EGR in transient load acceptence events which occurred over a range of 2 to 10 seconds. The faster transients increased deviations of boost and EGR levels from steady-state calibration values which consequently led to corresponding fuel consumption and particulate matter emission increases.
Technical Paper

A High Efficiency Small Internal Combustion Engine for the Production of Electricity Onboard Electric Vehicles

A combustion fuel tank, an internal combustion engine (ICE), and a generator provide the best opportunity to store extra energy onboard battery electric vehicles (BEV). This energy may be used for on-demand electricity production when needed, for example, rural or interstate driving. Specific to this work, the design of a high-efficiency ICE that works at a single speed and a single load, continuously, during the operation of this series hybrid vehicle is considered. The ICE and generator provide a fuel conversion efficiency chemical to electric η~50%. The series hybrid vehicle may deliver miles-per-gallon-of-gasoline (MPG) 13% better than current production plug-in hybrid electric vehicles (PHEV), and miles-per-gallon-of-gasoline-equivalent (MPGe) 12% better than the BEV of the same platform with a larger battery pack to permit capital cities commuting.