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Journal Article

Transient Fluid Flow and Heat Transfer in the EGR Cooler

EGR is a proven technology used to reduce NOx formation in both compression and spark ignition engines by reducing the combustion temperature. In order to further increase its efficiency the recirculated gases are subjected to cooling. However, this leads to a higher load on the cooling system of the engine, thus requiring a larger radiator. In the case of turbocharged engines the large variations of the pressures, especially in the exhaust manifold, produce a highly pulsating EGR flow leading to non-steady-state heat transfer in the cooler. The current research presents a method of determining the pulsating flow field and the instantaneous heat transfer in the EGR heat exchanger. The processes are simulated using the CFD code FIRE (AVL) and the results are subjected to validation by comparison with the experimental data obtained on a 2.5 liter, four cylinder, common rail and turbocharged diesel engine.
Technical Paper

Transient Cavitating Flow Simulations Inside a 2-D VCO Nozzle Using the Space-Time CE/SE Method

Cavitating flows inside a two-dimensional valve covered orifice (VCO) nozzle were simulated by using the Space-Time Conservation Element and Solution Element (CE/SE) method in conjunction with a homogeneous equilibrium cavitation model. As a validation for present model, cavitation over a NACA0015 hydrofoil was predicted and compared with previous simulation results as well as experimental observations. The model was then used to investigate the effects on internal cavitating flows of different nozzle design parameters, such as the hole size, hole aspect-ratio, hydro-erosion radius, and orifice inclination. Under different conditions, cavitating flows through fuel injectors generated hydraulic flip, supercavitation, full cavitation, and cyclical cavitation phenomena, which are commonly observed in experiments.
Technical Paper

The Burning Velocity in a CFR Engine with Different Turbulent Flow Fields Generated by Intake Valves

An equation has been derived to calculate the burning velocity in a CFR engine from the measured flame speed under different turbulent flow fields. The turbulence is generated during the intake stroke as the fresh charge flows through different perforated 360° shrouded intake valves. The shrouds have holes of different sizes, but of the same total flow area. Results show that these valves decrease the cycle-to-cycle variation and produce higher burning velocities than conventional valves, particularly at higher engine speeds. The burning velocity depends on the Reynolds number as well as the turbulence scale.
Technical Paper

Temperature Impact on Modeling and Control of Lean NOx Trap

Gasoline Direct Injection (GDI) engine has a significant fuel economy improvement over the traditional port fuel injection engine. The tradeoff for this benefit is excessive exhaust emissions, especially NOx. Three-way-catalyst (TWC) is inefficient to treat NOx emission during lean operation. So Lean NOx Trap (LNT) is invented for NOx aftertreatment and it has both storage mode and purge mode. Research on modeling and control of LNT has been conducted, but it is still lack of the essential information on the temperature effect. This research focuses on the impact of trap temperature on LNT storage time, purge time and fuel economy. The mechanism of temperature effect on LNT is investigated at first. Then the temperature control strategy based on fuel economy improvement is proposed.
Technical Paper

On the Development of a New Design Methodology for Vehicle Crashworthiness based on Data Mining Theory

This paper represents the development of a new design methodology based on data mining theory for decision making in vehicle crashworthy components (or parts) development. The new methodology allows exploring the big crash simulation dataset to discover the underlying complicated relationships between vehicle crash responses and design variables at multi-levels, and deriving design rules based on the whole vehicle safety requirements to make decisions towards the component and sub-component level design. The method to be developed will resolve the issue of existing design approaches for vehicle crashworthiness, i.e. limited information exploring capability from big datasets, which may hamper the decision making and lead to a nonoptimal design. A preliminary design case study is presented to demonstrate the performance of the new method. This method will have direct impacts on improving vehicle safety design and can readily be applied to other complex systems.
Technical Paper

Numerical Study of Ultra Low Solidity Airfoil Diffuser in an Automotive Turbocharger Compressor

For the application of advanced clean combustion technologies, such as diesel HCCI/LTC, a compressor with high efficiency over a broad operation range is required to supply a high amount of EGR with minimum pumping loss. A compressor with high pitch of vaneless diffuser would substantially improve the flow range of the compressor, but it is at the cost of compressor efficiency, especially at low mass flow area where most of the city driving cycles resides. In present study, an ultra low solidity compressor vane diffuser was numerically investigated. It is well known that the flow leaving the impeller is highly distorted, unsteady and turbulent, especially at relative low mass flow rate and near the shroud side of the compressor. A conventional vaned diffuser with high stagger angle could help to improve the performance of the compressor at low end. However, adding diffuser vane to a compressor typically restricts the flow range at high end.
Journal Article

Iterative Learning Control for a Fully Flexible Valve Actuation in a Test Cell

An iterative learning control (ILC) algorithm has been developed for a test cell electro-hydraulic, fully flexible valve actuation system to track valve lift profile under steady-state and transient operation. A dynamic model of the plant was obtained from experimental data to design and verify the ILC algorithm. The ILC is implemented in a prototype controller. The learned control input for two different lift profiles can be used for engine transient tests. Simulation and bench test are conducted to verify the effectiveness and robustness of this approach. The simple structure of the ILC in implementation and low cost in computation are other crucial factors to recommend the ILC. It does not totally depend on the system model during the design procedure. Therefore, it has relatively higher robustness to perturbation and modeling errors than other control methods for repetitive tasks.
Technical Paper

Investigation of Diesel Spray Primary Break-up and Development for Different Nozzle Geometries

The nozzle configuration for an injector is known to have an important effect on the fuel atomization. A comprehensive experimental and numerical investigation has been performed to determine the influence of various internal geometries on the primary spray breakup and development using the electronically controlled high-pressure diesel injection systems. Different types of multi-hole minisac and VCO nozzles with cylindrical and tapered geometries, and different types of single-hole nozzles with defined grades of Hydro Grinding (HG) were investigated. The global characteristics of the spray, including spray angle, spray tip penetration and spray pattern were measured from the spray images with a high-speed drum camera. A long-distance microscope with a pulsed-laser as the optical shutter was used to magnify the diesel spray at the nozzle hole vicinity. A CFD analysis of the internal flow through various nozzle geometries has been carried out with a commercial code.
Technical Paper

Innovative Graduate Program in Mechatronics Engineering to Meet the Needs of the Automotive Industry

A new inter-disciplinary degree program has been developed at Lawrence Technological University: the Master of Science in Mechatronic Systems Engineering Degree (MS/MSE). It is one of a few MS-programs in mechatronics in the U.S.A. today. This inter-disciplinary program reflects the main areas of ground vehicle mechatronic systems and robotics. This paper presents areas of scientific and technological principles which the Mechanical Engineering, Electrical and Computer Engineering, and Math and Computer Science Departments bring to Mechatronic Systems Engineering and the new degree program. New foundations that make the basis for the program are discussed. One of the biggest challenges was developing foundations for mechanical engineering in mechatronic systems design and teaching them to engineers who have different professional backgrounds. The authors first developed new approaches and principles to designing mechanical subsystems as components of mechatronic systems.
Technical Paper

Implications of 3-D Internal Flow Simulation on the Design of Inward-Opening Pressure-Swirl Injectors

A parametric study on the effects of critical injector design parameters of inwardly-opening pressure-swirl injectors was carried out using 3-D internal flow simulations. The pressure variation and the integrated momentum flux across the injector, as well as the flow distributions and turbulence structure at the nozzle exit were analyzed. The critical flow effects on the injector design identified are the swirler efficiency, discharge coefficient, and turbulence breakup effects on the spray structure. The study shows that as a unique class of injectors, pressure-swirl injectors is complicated in fluid mechanics and not sufficiently characterized or optimized. The swirler efficiency is characterized in terms of the trade-off relationship between the swirl-to-axial momentum-flux ratio and pressure drop across the swirler. The results show that swirl number is inversely proportional to discharge coefficient, and that hole diameter and swirler height is the most dominant parameters.
Technical Paper

Impact of Biodiesel Emission Products from a Multi-Cylinder Direct Injection Diesel Engine on Particulate Filter Performance

As diesel emission regulations continue to increase, the use of exhaust aftertreatment systems containing, for example the diesel oxidation catalyst (DOC) and diesel particulate filter (DPF) will become necessary in order to meet these stringent emission requirements. The addition of a DOC and DPF in conjunction with utilizing biodiesel fuels requires extensive research to study the implications that biodiesel blends have on emissions as well as to examine the effect on aftertreatment devices. The proceeding work discusses results from a 2006 VM Motori four-cylinder 2.8L direct injection diesel engine coupled with a diesel oxidation catalyst and catalyzed diesel particulate filter. Tests were done using ultra low sulfur diesel fuel blended with 20% choice white grease biodiesel fuel to evaluate the effects of biodiesel emission products on the performance and effectiveness of the aftertreatment devices and the effect of low temperature combustion modes.
Technical Paper

GDi Skew-Angled Nozzle Flow and Near-Field Spray Analysis using Optical and X-Ray Imaging and VOF-LES Computational Fluid Dynamics

Improvement of spray atomization and penetration characteristics of the gasoline direct-injection (GDi ) multi-hole injector is a critical component of the GDi combustion developments, especially in the context of engine down-sizing and turbo-charging trend that is adopted in order to achieve the European target CO₂, US CAFE, and concomitant stringent emissions standards. Significant R&D efforts are directed towards optimization of the nozzle designs, in order to improve the GDi multi-hole spray characteristics. This publication reports VOF-LES analyses of GDi single-hole skew-angled nozzles, with β=30° skew (bend) angle and different nozzle geometries. The objective is to extend previous works to include the effect of nozzle-hole skew angle on the nozzle flow and spray primary breakup. VOF-LES simulations of a single nozzle-hole of a purpose-designed GDi multi-hole seat geometry, with three identical nozzle-holes per 120° seat segment, are performed.
Technical Paper

GDi Nozzle Parameter Studies Using LES and Spray Imaging Methods

Development of in-cylinder spray targeting, plume penetration and atomization of the gasoline direct-injection (GDi) multi-hole injector is a critical component of combustion developments, especially in the context of the engine downsizing and turbo-charging trend that has been adopted in order to achieve the European target CO2, US CAFE, and concomitant stringent emissions standards. Significant R&D efforts are directed towards the optimization of injector nozzle designs in order to improve spray characteristics. Development of accurate predictive models is desired to understand the impact of nozzle design parameters as well as the underlying physical fluid dynamic mechanisms resulting in the injector spray characteristics. This publication reports Large Eddy Simulation (LES) analyses of GDi single-hole skew-angled nozzles, with β=30° skew (bend) angle and different nozzle geometries.
Technical Paper

Experimental and Simulation Analysis of PFI-SI Engine for Fuel Economy Improvement

Variable Valve Timing (VVT) strategy on both intake and exhaust valves has a pivotal influence on the specific fuel consumptions and engine performance. In addition to this, fuel economy can also be enhanced by the application of Variable Compression Ratio (VCR) strategy. This paper presents three possible strategies to enhance fuel economy improvement: A possible VVT strategy Early Intake Valve Opening (EIVO) and Late Exhaust Valve Closure (LEVC) that alters the valve overlap to reduce fuel consumption A two-position VCR system that improves fuel conversion factor to realize fuel economy A strategy that combines above two technologies to produce a complementary effect on fuel economy All three strategies have been tested on a 1.8L DOHC four cylinder PFI engine. AVL BOOST a 1D engine gas exchange and cycle simulation code was used to model this engine to get fuel economy gains at part-load points.
Technical Paper

Experimental Analysis of Dynamics and Friction in Valve Train Systems

The paper analyses the friction in the valve train of an internal combustion engine trying to separate the contribution of the different components to the total friction losses in the valve train. The measurements are performed on a running engine in order to avoid extraneous factors introduced by simulating rigs. The experimental engine is instrumented with strain gauge bridges on the rocker arm, the push rod and the camshaft to measure forces and moments acting on these components. Original techniques are developed to isolate and determine the friction forces between the valve stem and its guide, the friction force in the rocker arm bearing and the combined friction between cam/tappet and tappet/bore. It was found that the friction in the rocker arm bearing never reaches hydrodynamic conditions and that the friction coefficient between cam and tappet reduces with an increase in the engine speed.
Technical Paper

Effect of Imposed Faults on a Distributor Injection System

The effects of several faults on different parameters in a distributor injection system are studied both theoretically and experimentally. The faults imposed on a healthy system are: fuel leaks between the pump and injector, improper adjustment of the injector opening pressure, a broken or missing injector spring, plugged nozzle holes, and a stuck-closed needle. The injector parameters examined include maximum fuel pressures reached at different locations in the system, needle lift, injection lag, and injection rate.
Technical Paper

Dynamics of Multiple-Injection Fuel Sprays in a Small-bore HSDI Diesel Engine

An experimental study was conducted to characterize the dynamics and spray behavior of a wide range of minisac and Valve-Covered-Orifice (VCO) nozzles using a high-pressure diesel common-rail system. The measurements show that the resultant injection-rate is strongly dependent on common-rail pressure, nozzle hole diameter, and nozzle type. For split injection the dwell between injections strongly affects the second injection in regards to the needle lift profile and the injected fuel amount. The minisac nozzle can be used to achieve shorter pilot injections at lower common-rail pressures than the VCO nozzle. Penetration photographs of spray development in a high pressure, optical spray chamber were obtained and analyzed for each test condition. Spray symmetry and spray structure were found to depend significantly on the nozzle type.
Technical Paper

Design and Implementation of CRC Module of eCall In-Vehicle System on FPGA

The EU emergency call (eCall) system is used as a vehicle emergency telematic system to reduce the fatalities and save more lives in vehicular incidents. We have designed and implemented the CRC module for the in-vehicle system (IVS) of the EU eCall on an FPGA device. As the CRC is a crucial part of the system to detect bit errors during the transmission, this paper presents the hardware design procedures of the CRC module. The system reads the 1120 serial input bits of the Minimum Set of Data (MSD), calculates the 28-bits of the CRC parity bits, and generates the MSD appended with CRC as the output signal that is consisting of 1148 serial bits. The system is designed in Verilog HDL, compiled, synthesized, and simulated for different MSDs. The results are shown and analyzed for varied applied MSDs. The flowchart of the implemented algorithm is illustrated and discussed.
Technical Paper

Correlating the Diesel Spray Behavior to Nozzle Design

This paper studies the effect of nozzle geometry on the flow characteristics inside a diesel fuel injection nozzle and correlates to the subsequent atomization process under different operating conditions, using simple turbulent breakup model. Two kinds of nozzles, valve covered orifice (VCO) and mini-SAC nozzle, with various nozzle design parameters were studied. The internal flow inside the nozzle was simulated using 3-D computational fluid dynamics software with k-ε turbulence model. The flow field at the nozzle exit was characterized by two parameters: the fuel discharge coefficient Cd and the initial amplitude parameter amp0. The latter parameter represents the turbulence characteristics of the exit flow. The effects of nozzle geometry on the mean velocity and turbulent energy distribution of the exit flow were also studied. The characteristics of the exit flow were then incorporated into the spray model in KIVA-II to study the effect of nozzle design on diesel spray behavior.
Technical Paper

Comparing Cavitation in Diesel Injectors Based on Different Modeling Approaches

Results of Computational Fluid Dynamic (CFD) analyses of different diesel fuel injector nozzle configurations using a commercial CFD code are presented here. The emphasis of this study is on comparing cavitation models available in the commercial code with respect to their mathematical approach. One of the models is a simple single-phase model based on the Barotropic equation of state, while the other model is a two-phase model based on the bubble dynamic considerations. Results are compared for various 3-D diesel injector nozzles using the two cavitation-modeling approaches. Simulation results are observed to substantiate some of the experimentally established facts like; nozzle efficiency improvements by using techniques like rounded orifice inlets and conical orifices. Also, simulation results agree well with the experimental results. Spray characteristics are predicted based on a primary breakup model.