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This study outlines an approach for speeding up the simulation of the dynamic response of vehicle models that include hysteretic nonlinear tire components. The method proposed replaces the hysteretic nonlinear tire model with a surrogate model that emulates the dynamic response of the actual tire. The approach is demonstrated via a dynamic simulation of a quarter vehicle model. In the proposed methodology, training information generated with a reduced number of harmonic excitations is used to construct the tire hysteretic force emulator using a Neural Network (NN) element. The proposed approach has two stages: a learning stage, followed by an embedding of the learned model into the quarter car model. The learning related main challenge stems from the attempt to capture with the NN element the behavior of a hysteretic element whose response depends on its loading history.

Reactivity Controlled Compression Ignition (RCCI) is an engine combustion strategy that utilizes in-cylinder fuel blending to produce low NOx and PM emissions while maintaining high thermal efficiency. Previous RCCI research has been investigated in single-cylinder heavy-duty engines [1, 2, 3, 4, 5, 6]. The current study investigates RCCI operation in a light-duty multi-cylinder engine over a wide number of operating points representing vehicle operation over the US EPA FTP test. Similarly, previous RCCI engine experiments have used petroleum based fuels such as ultra-low sulfur diesel fuel (ULSD) and gasoline, with some work done using high percentages of biofuels, namely E85 [7]. The current study was conducted to examine RCCI performance with moderate biofuel blends, such as E20 and B20, as compared to conventional gasoline and ULSD.

NVH simulations for an automotive component industry represent a convenient mean to compare different solutions and make decisions on design choices based on the predictions of the component vibro-acoustic behavior. This paper presents the vibro-acoustic characterization and comparison of two fuel rail assemblies (FRAs) by mean of simulations in Ansys Workbench & LMS Virtual.Lab. These simulations required a preliminary finite element (FE) modal analysis on the FRAs. To verify the reliability of the FE models, an experimental modal analysis was performed on one of the two fuel rails in free-free condition. The correlation between FE and test models highlighted some differences: a sensitivity study proved that the differences depend on the modeling of some brazed joints. The results of the following NVH simulations were checked by performing an acoustic impact test on the two FRAs in free-free condition inside an anechoic chamber.

An investigation of the permeability evolution of a diesel particulate filter channel wall as a function of soot loading was conducted. This investigation examined the effects of varying particle characteristics and two filtration velocities (4 and 8 cm/s) on the wall permeability throughout a 1 g/L soot loading. This study was possible using the Diesel Exhaust Filtration Analysis (DEFA) system that was modified to perform temperature controlled in-situ flow tests. The DEFA system allows for isolation of the pressure drop due to the filter wall and soot cake layer greatly simplifying the permeability calculation. Permeability evolution fundamentals and the effects of loading conditions were studied by filling 18 filters with the DEFA system. The filters were loaded using one of four operating conditions of a single-cylinder heavy-duty diesel engine. These operating conditions were comprehensively characterized giving insight into the effects of varying particle characteristics.

The focus of this paper is to discuss the modeling and control of intake plenum pressure on the Powertrain Control Research Laboratory's (PCRL) Single-Cylinder Engine (SCE) transient test system using a patented device known as the Intake Air Simulator (IAS), which dynamically controls the intake plenum pressure, and, subsequently, the instantaneous airflow into the cylinder. The IAS exists as just one of many devices that the PCRL uses to control the dynamic boundary conditions of its SCE transient test system to make it “think” and operate as though it were part of a Multi-Cylinder Engine (MCE) test system. The model described in this paper will be used to design a second generation of this device that utilizes both continuously and discretely actuating valves working in parallel.

Premixed charge compression ignition (PCI) strategies offer the potential for simultaneously low NOx and soot emissions with diesel-like efficiency. However, these strategies are generally confined to low loads due to inadequate control of combustion phasing and heat-release rate. One PCI strategy, dual-fuel reactivity-controlled compression ignition (RCCI), has been developed to control combustion phasing and rate of heat release. The RCCI concept uses in-cylinder blending of two fuels with different auto-ignition characteristics to achieve controlled high-efficiency clean combustion. This study explores fuel reactivity stratification as a method to control the rate of heat release for PCI combustion. To introduce fuel reactivity stratification, the research engine is equipped with two fuel systems. A low-pressure (100 bar) gasoline direct injector (GDI) delivers iso-octane, and a higher-pressure (600 bar) common-rail diesel direct-injector delivers n-heptane.

The interaction of fuel sprays with in-cylinder air flow is crucially important for the mixture preparation and subsequent combustion processes in gasoline direct injection (GDI) engines. In the present work, the experimentally validated computational fluid dynamics (CFD) simulations are performed to study the dynamics and physical insight of hollow-cone sprays interacting with a uniform crossflow. The basis of the model is the standard Reynolds-averaged Navier-Stokes (RANS) approach coupled to the Lagrangian treatment for statistical groups (parcels) representing the physical droplet population. The most physically suitable hybrid breakup models depicting the liquid sheet atomization and droplet breakup processes based on the linear instability analysis and Taylor analogy theory (LISA-TAB) are used. Detailed comparisons are made between the experiments and computations in terms of spray structure, local droplet diameter and velocity distributions.

The paper describes the CFD analysis, the arrangement and the first experimental results of a single-cylinder engine that employs an innovative low-pressure hydrogen direct-injection system, characterized by low fuel rail pressure (12 bar) and consequent low residual storage pressure. The injection is split in two steps: at first hydrogen is metered and admitted into a small intermediate chamber by an electroinjector (a conventional one usually employed for CNG), next a mechanically actuated poppet valve, that allows high volumetric flow rates, times hydrogen injection from the intermediate chamber to the cylinder within a short time, despite the high hydrogen volume due to the low injection pressure. Injection must be properly timed to maintain pressure below 6 bar (or little more) in the intermediate chamber and thus keep sonic flow through the electroinjector, to maximize volumetric efficiency and to avoid backfire in the intake pipe.

In-cylinder fuel blending of gasoline with diesel fuel is investigated on a multi-cylinder light-duty diesel engine as a strategy to control in-cylinder fuel reactivity for improved efficiency and lowest possible emissions. This approach was developed and demonstrated at the University of Wisconsin through modeling and single-cylinder engine experiments. The objective of this study is to better understand the potential and challenges of this method on a multi-cylinder engine. More specifically, the effect of cylinder-to-cylinder imbalances and in-cylinder charge motion as well as the potential limitations imposed by real-world turbo-machinery were investigated on a 1.9-liter four-cylinder engine. This investigation focused on one engine condition, 2300 rpm, 5.5 bar net mean effective pressure (NMEP). Gasoline was introduced with a port-fuel-injection system.

Homogeneous-charge, compression-ignition (HCCI) combustion is triggered by spontaneous ignition in dilute homogeneous mixtures. The combustion rate must be reduced by suitable solutions such as high rates of Exhaust Gas Recirculation (EGR) and/or lean mixtures. HCCI is considered a very effective way to reduce engine pollutant emissions, however only a few HCCI engines have entered into production. HCCI combustion currently cannot be extended to the whole engine operating range, especially to high loads, since the use of EGR displaces air from the cylinder, limiting engine mean effective pressure, thus the engine must be able to operate also in conventional mode. This paper concerns an innovative concept to control HCCI combustion in diesel-fuelled engines. This new combustion concept is called Homogenous Charge Progressive Combustion (HCPC). HCPC is based on split-cycle principle.

The spray characteristics are determining factors for the quality of mixture formation respectively for the combustion, when applying GDI. Their variation with load and speed is a basic criterion for the adaptability of an injection system type to an engine with known requirements. CFD models of the fluid flow dynamics, mixture formation and combustion are a determining condition for such adaptation. The paper presents the development results of a GDI four-stroke, four-valve, single cylinder engine. The pressure pulse injection system involved in this application is analyzed and presented from the fluid-dynamic behavior up to the obtained injection spray characteristics. The mixture formation and combustion processes are simulated for different load and speed values, respectively for favorable combinations of parameters, such as the injection system configuration, the opening pressure of the applied mechanical injector and the injection duration.

High-pressure diesel sprays were simulated with an Eulerian-Lagrangian Spray and Atomization (ELSA) model, based on a multidimensional engine computational fluid dynamics (CFD) code KIVA-3V. The atomization of the dense liquid core in the near-nozzle region was modeled with turbulent mixing of the diesel fuel with the ambient gas. Under the continuum assumption of a fuel-air mixture in this region, two transport equations were solved for the liquid mass fraction and liquid surface area density. At a certain downstream location where the spray became dilute, a switch from the Eulerian to the Lagrangian approach was made to benefit from the advantages of the conventional Lagrangian droplet models, such as droplet collision and turbulent dispersion modeling. The droplet size and velocity to be initialized at this switch were determined by the local CFD cell properties.

The normal approach to shifting a manual transmission in a vehicle includes a clutch which connects the engine to the transmission. When shifting, the relative speed of the engine and wheels changes. The transmission is disconnected from the engine with the clutch and the gears in the transmission are pressed together until they engage. There are small friction synchronizers inside the transmission, but these are only designed for the inertia of the gears and the clutch pressure plate. The clutch is required to synchronize the transmission speed with the engine speed after a shift, and to remove the load from the transmission before a shift. Described is a method for automating a manual transmission hybrid-electric powertrain which doesn't require a clutch. A hybrid drivetrain including an electric motor and a combustion engine has the benefit of much better speed and torque control than a combustion engine alone.

An innovative hydrogen DI system was conceived, realized and tested that requires only 12 bar rail pressure, typical value of PFI systems, and does not need special injectors. The purpose is to combine the well-known benefits of DI with the ones of PFI. The injection is accomplished in two steps: at first hydrogen, metered by an electroinjector (a conventional one for CNG application), enters a small intermediate chamber; then it is injected into the cylinder by means of a mechanically actuated valve that allows very high flow rate (compared with the one of electroinjectors). In-cylinder injection starts at intake valve closing (an earlier injection start could lead to backfire) and stops early enough to allow proper charge homogeneity and, in any case, before cylinder pressure rise constrains hydrogen admission. The prototype engine was realized modifying a production single-cylinder 650 cm₃ engine with three intake valves.

In an attempt to increase efficiency and lower critical and highly regulated emissions (i.e., NOx, PM and CO2) many advanced combustion strategies have been investigated. Most of the current strategies fall into the category of low temperature combustion (LTC), which allow emissions mandates to be met in-cylinder along with anticipated reduction in cost and complexity. These strategies, such as homogeneous charge compression ignition (HCCI), premixed charge compression ignition (PCCI), partially premixed combustion (PPC) and reactivity controlled compression ignition (RCCI), use early injection timings, resulting in a highly lean charge with increased specific heat ratios to improve thermal efficiency and reduce PM emissions. Lower combustion temperatures also avoid the activation of NOx formation reactions.

This paper describes numerical simulations that compare the performance of two combustion CFD models against experimental data, and evaluates the effects of combustion and spray model constants on the predicted combustion and emissions under various operating conditions. The combustion models include a Characteristic Time Combustion (CTC) model and CHEMKIN with reduced chemistry models integrated in the KIVA-3Vr2 CFD code. The diesel spray process was modeled using an updated version of the KH-RT spray model that features a gas jet submodel to help reduce numerical grid dependencies, and the effects of both the spray and combustion model constants on combustion and emissions were evaluated. In addition, the performance of two soot models was compared, namely a two-step soot model, and a more detailed model that considers soot formation from PAH precursors.

In automotive industry it has been a challenge to retain diesel-like thermal efficiency while maintaining low emissions. Numerous studies have shown significant progress in achieving low emissions through the introduction of common-rail injection systems, multiple injections and exhaust gas recirculation and by using a high octane number fuel, like gasoline, to achieve adequate premixing. On the other hand, low temperature combustion strategies, like HCCI and PCCI, have also shown promising results in terms of reducing both NOx and soot emissions simultaneously. With the increasing capacity of computers, multi-dimensional CFD engine modeling enables a reasonably good prediction of combustion characteristics and pollutant emissions, which is the motivation behind the present research. The current research effort presents an optimization study of light-duty compression ignition engine performance, while meeting the emission regulation targets.

Many concepts of premixed diesel combustion at reduced temperatures have been investigated over the last decade as a means to simultaneously decrease engine-out particle and oxide of nitrogen (NO ) emissions. To overcome the trade-off between simultaneously low particle and NO emissions versus high "diesel-like" combustion efficiency, a new dual-fuel technique called Reactivity Controlled Compression Ignition (RCCI) has been researched. In the present study, particle size distributions were measured from RCCI for four gasoline:diesel compositions from 65%:35% to 84%:16%, respectively. Previously, fuel blending (reactivity control) had been carried out by a port fuel injection of the higher volatility fuel and a direct in-cylinder injection of the lower volatility fuel. With a recent mechanical upgrade, it was possible to perform injections of both fuels directly into the combustion chamber.

Due to concerns regarding pollutant and CO2 emissions, advanced combustion modes that can simultaneously reduce exhaust emissions and improve thermal efficiency have been widely investigated. The main characteristic of the new combustion strategies, such as HCCI and LTC, is that the formation of a homogenous mixture or a controllable stratified mixture is required prior to ignition. The major issue with these approaches is the lack of a direct method for the control of ignition timing and combustion rate, which can be only indirectly controlled using high EGR rates and/or lean mixtures. Homogeneous Charge Progressive Combustion (HCPC) is based on the split-cycle principle. Intake and compression phases are performed in a reciprocating external compressor, which drives the air into the combustor cylinder during the combustion process, through a transfer duct. A transfer valve is positioned between the compressor cylinder and the transfer duct.

A comprehensive biodiesel combustion model is presented for use in multi-dimensional engine simulations. The model incorporates realistic physical properties in a vaporization model developed for multi-component fuel sprays and applies an improved mechanism for biodiesel combustion chemistry. Previously, a detailed mechanism for methyl decanoate and methyl-9-decenoate was reduced from 3299 species to 85 species to represent the components of biodiesel fuel. In this work, a second reduction was performed to further reduce the mechanism to 69 species. Steady and unsteady spray simulations confirmed that the model adequately reproduced liquid penetration observed in biodiesel spray experiments. Additionally, the new model was able to capture expected fuel composition effects with low-volatility components and fuel blend sprays penetrating further.