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Technical Paper

Design and Testing of a Prototype Hybrid-Electric Split-Parallel Crossover Sports Utility Vehicle

The University of Wisconsin - Madison Hybrid Vehicle Team has designed, fabricated, tested and optimized a four-wheel drive, charge sustaining, split-parallel hybrid-electric crossover vehicle for entry into the 2006 Challenge X competition. This multi-year project is based on a 2005 Chevrolet Equinox platform. Trade-offs in fuel economy, greenhouse gas impact (GHGI), acceleration, component packaging and consumer acceptability were weighed to establish Wisconsin's Vehicle Technical Specifications (VTS). Wisconsin's Equinox, nicknamed the Moovada, utilizes a General Motors (GM) 110 kW 1.9 L CIDI engine coupled to GM's 6-speed F40 transmission. The rear axle is powered by a 65 kW Ballard induction motor/gearbox powered from a 44-module (317 volts nominal) Johnson Controls Inc., nickel-metal hydride hybrid battery pack. It includes a newly developed proprietary battery management algorithm which broadcasts the battery's state of charge onto the CAN network.
Technical Paper

Modeling Iso-octane HCCI Using CFD with Multi-Zone Detailed Chemistry; Comparison to Detailed Speciation Data Over a Range of Lean Equivalence Ratios

Multi-zone CFD simulations with detailed kinetics were used to model iso-octane HCCI experiments performed on a single-cylinder research engine. The modeling goals were to validate the method (multi-zone combustion modeling) and the reaction mechanism (LLNL 857 species iso-octane) by comparing model results to detailed exhaust speciation data, which was obtained with gas chromatography. The model is compared to experiments run at 1200 RPM and 1.35 bar boost pressure over an equivalence ratio range from 0.08 to 0.28. Fuel was introduced far upstream to ensure fuel and air homogeneity prior to entering the 13.8:1 compression ratio, shallow-bowl combustion chamber of this 4-stroke engine. The CFD grid incorporated a very detailed representation of the crevices, including the top-land ring crevice and head-gasket crevice. The ring crevice is resolved all the way into the ring pocket volume. The detailed grid was required to capture regions where emission species are formed and retained.
Technical Paper

Validation of a Sparse Analytical Jacobian Chemistry Solver for Heavy-Duty Diesel Engine Simulations with Comprehensive Reaction Mechanisms

The paper presents the development of a novel approach to the solution of detailed chemistry in internal combustion engine simulations, which relies on the analytical computation of the ordinary differential equations (ODE) system Jacobian matrix in sparse form. Arbitrary reaction behaviors in either Arrhenius, third-body or fall-off formulations can be considered, and thermodynamic gas-phase mixture properties are evaluated according to the well-established 7-coefficient JANAF polynomial form. The current work presents a full validation of the new chemistry solver when coupled to the KIVA-4 code, through modeling of a single cylinder Caterpillar 3401 heavy-duty engine, running in two-stage combustion mode.
Technical Paper

Nozzle Effect on High Pressure Diesel Injection

Studies of transient diesel spray characteristics at high injection pressures were conducted in a constant volume chamber by utilizing a high speed photography and light extinction optical diagnostic technique. Two different types of nozzle hole entrances were investigated: a sharp-edged and a round-edged nozzle. The experimental results show that for the same injection delivery, the sharp-edged inlet injector needed a higher injection pressure to overcome the higher friction loss, but it produced longer spray tip penetration length, larger spray angle, smaller droplet sizes, and also lower particulate emission from a parallel engine test. For the round-edged and smooth edged tips at the same injection pressure, the sharp-edged inlet tip took a longer injection duration to deliver a fixed mass of fuel and produced larger overall average Sauter Mean Diameter (SMD) droplets.
Technical Paper

Modeling the Effects of Fuel Injection Characteristics on Diesel Engine Soot and NOx Emissions

The three-dimensional KIVA code has been used to study the effects of injection pressure and split injections on diesel engine performance and soot and NOx emissions. The code has been updated with state-of-the-art submodels including: a wave breakup atomization model, drop drag with drop distortion, spray/wall interaction with sliding, rebounding, and breaking-up drops, multistep kinetics ignition and laminar-turbulent characteristic time combustion, wall heat transfer with unsteadiness and compressibility, Zeldovich NOx formation, and soot formation with Nagle Strickland-Constable oxidation. The computational results are compared with experimental data from a single-cylinder Caterpillar research engine equipped with a high-pressure, electronically-controlled fuel injection system, a full-dilution tunnel for soot measurements, and gaseous emissions instrumentation.
Technical Paper

Reducing Particulate and NOx Using Multiple Injections and EGR in a D.I. Diesel

An emissions and performance study was conducted to explore the effects of EGR and multiple injections on particulate, NOx, and BSFC. EGR is known to be effective at reducing NOx, but at high loads there is usually a large increase in particulate. Recent work has shown that multiple injections are effective at reducing particulate. Thus, it was of interest to examine the possibility of simultaneously reducing particulate and NOx with the combined use of EGR and multiple injections. The tests were conducted on a fully instrumented single cylinder version of the Caterpillar 3406 heavy duty truck engine. Tests were done at high load (75% of peak torque at 1600 RPM where EGR has been shown to produce unacceptable increases in particulate emissions. The fuel system used was an electronically controlled, common rail injector and supporting hardware. The fuel system was capable of up to four independent injections per cycle.
Technical Paper

Effects of Injection Pressure and Nozzle Geometry on D.I. Diesel Emissions and Performance

An emissions and performance study was performed to show the effects of injection pressure, nozzle hole inlet condition (sharp and rounded edge) and nozzle included spray angle on particulate, NOx, and BSFC. The tests were conducted on a fully instrumented single-cylinder version of the Caterpillar 3406 heavy duty engine at 75% and 25% load at 1600 RPM. The fuel system consisted of an electronically controlled, hydraulically actuated, unit injector capable of injection pressures up to 160 MPa. Particulate versus NOx trade-off curves were generated for each case by varying the injection timing. The 75% load results showed the expected decrease in particulate and flattening of the trade-off curve with increased injection pressure. However, in going from 90 to 160 MPa, the timing had to be retarded to maintain the same NOx level, and this resulted in a 1 to 2% increase in BSFC. The rounded edged nozzles were found to have an increased discharge coefficient.
Technical Paper

In-Cylinder Diesel Flame Imaging Compared with Numerical Computations

An image acquisition-and-processing camera system was developed for in-cylinder diagnostics of a single-cylinder heavy duty diesel engine. The engine was equipped with an electronically-controlled common-rail fuel injection system that allowed both single and split (multiple) injections to be studied. The imaging system uses an endoscope to acquire luminous flame images from the combustion chamber and ensures minimum modification to the engine geometry. The system also includes an optical linkage, an image intensifier, a CID camera, a frame grabber, control circuitry and a computer. Experiments include both single and split injection cases at 90 MPa and 45 MPa injection pressures at 3/4 load and 1600 rev/min with simulated turbocharging. For the single injection at high injection pressure (90 MPa) the results show that the first luminous emissions from the ignition zone occur very close to the injector exit followed by rapid luminous flame spreading.
Technical Paper

Investigation of Diesel Sprays Using Diffraction-Based Droplet Sizing

The study of combustion in direct injection Diesel engines demands detailed understanding of the behavior of the injection. Understanding the injection involves characterizing the distribution of fuel particle sizes throughout the spray. This work studied the size distributions of sprays from commercial Diesel injectors under a series of conditions. A diffraction-based diagnostic obtained maps of local fuel droplet size information over the full spray field. Most quantitative techniques currently used in spray research provide quantitative time-ranging data at a single point in the spray field. Spatially resolved information proves more useful in studying transient sprays. The spatially resolved maps of particle size obtained in this experiment showed the reliability of the diagnostic, exhibited the transience of the fine structure of these sprays, and demonstrated the evolution of the sprays with time.
Technical Paper

High Temperature Liquid Lubricant Development Part I: Engine Tests

A high horsepower, low heat rejection diesel engine is being developed to meet future Army heavy combat vehicle requirements. This engine features high power output in a compact design that is oil-cooled allowing for a significant reduction in radiator size. This design requires a lubricant which can survive a sump temperature of 160°C, for 300 hours with transient sump temperature surges to over 177°C. A comprehensive high temperature lubricant development program has been initiated to address the need for this new design. A modified Cummins 10 liter diesel engine was used to simulate the operating condition of this low heat rejection engine. The premium commercial lubricant that was tested survived only 58 hours before completely losing oxidative stability. Several of the experimental lubricants completed the 200-hour peak torque endurance test.
Technical Paper

An Analysis on Time Scale Separation for Engine Simulations with Detailed Chemistry

The simulation of combustion chemistry in internal combustion engines is challenging due to the need to include detailed reaction mechanisms to describe the engine physics. Computational times needed for coupling full chemistry to CFD simulations are still too computationally demanding, even when distributed computer systems are exploited. For these reasons the present paper proposes a time scale separation approach for the integration of the chemistry differential equations and applies it in an engine CFD code. The time scale separation is achieved through the estimation of a characteristic time for each of the species and the introduction of a sampling timestep, wherein the chemistry is subcycled during the overall integration. This allows explicit integration of the system to be carried out, and the step size is governed by tolerance requirements.
Technical Paper

Simultaneous Reduction of Soot and NOX Emissions by Means of the HCPC Concept: Complying with the Heavy Duty EURO 6 Limits without Aftertreatment System

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.
Technical Paper

Emissions and Performance of a Small L-Head Utility Engine Fueled with Homogeneous Propane/Air and Propane/Air/Nitrogen Mixture

The objective of this study was to observe and attempt to understand the effects of equivalence ratio and simulated exhaust gas recirculation (EGR) on the exhaust emissions and performance of a L-head single cylinder utility engine. In order to isolate these effects and limit the confounding influences caused by poor fuel mixture preparation and/or vaporization produced by the carburetor/intake port combination, the engine was operated on a premixed propane/air mixture. To simulate the effects of EGR, a homogeneous mixture of propane, air, and nitrogen was used. Engine measurements were obtained at the operating conditions specified by the California Air Resources Board (CARB) Raw Gas Method Test Procedure. Measurements included exhaust emissions levels of HC, CO, and NOx, and engine pressure data.
Technical Paper

Performance and Operational Characteristics of High-Powered Diesel Truck Engines

There has been an accelerated growth in power of diesel engines in United States line haul trucking. This paper analyzes the effect of high power on engine-related operating variables that occur under different highway conditions and dissimilar terrain features. When properly applied, high-powered diesel engines can increase average vehicle speed and/or fuel economy.
Technical Paper

On Simulating Sloshing in Vehicle Dynamics

We present an approach in which we use simulation to capture the two-way coupling between the dynamics of a vehicle and that of a fluid that sloshes in a tank attached to the vehicle. The simulation is carried out in and builds on support provided by two modules: Chrono::FSI (Fluid-Solid Interaction) and Chrono::Vehicle. The dynamics of the fluid phase is governed by the mass and momentum (Navier-Stokes) equations, which are discretized in space via a Lagrangian approach called Smoothed Particle Hydrodynamics. The vehicle dynamics is the solution of a set of differential algebraic equations of motion. All equations are discretized in time via a half-implicit symplectic Euler method. This solution approach is general - it allows for fully three dimensional (3D) motion and nonlinear transients. We demonstrate the solution in conjunction with the simulation of a vehicle model that performs a constant radius turn and double lane change maneuver.
Technical Paper

Selection of the Optimized Aftercooling System for Cummins Premium Diesel Engines

The ongoing need for improved fuel economy, longer engine life, lower emissions, and in some cases, increased power output makes lower charge air temperatures more desirable. In 1983, Cummins introduced the new BCIV engine at 400 H.P. (298 KW) with “Optimized Aftercooling”, and is now introducing this concept to its remaining 10 and 14 Litre premium diesel engines. This Tuned Low Flow Cooling design provides many advantages when compared to the other alternatives studied, which included air-to-air and systems incorporating two radiators. The selection process considered performance, durability, fuel economy, emissions, noise, investment, and total vehicle installed cost. Computer simulations and vehicle tests were used to determine performance for each charge air cooling alternative. The simulations were used to guide prototype development and the selection of production hardware.
Technical Paper

Assessing Product Reliability from Warranty Data

Warranty data can be a useful, accurate, and timely information source for monitoring the reliability of a product. At Cummins Engine Company a warranty based reliability information system was developed for diesel engines that has the capability to 1) evaluate the reliability of engines and their components, 2) compare the reliability performance of engines and components to goals and prioritize those areas needing improvement, and 3) detect changes in the warranty claims pattern of engine components to provide early warning of potential problems. This paper will describe this warranty data system with emphasis on the analytical tools used to perform the above activities. Although many of the examples refer to diesel engines, the general concepts apply to the use of warranty data for many types of products.
Technical Paper

Transient Emissions from an Uncolled Diesel Engine

A Cummins B55 in3 350 bhp heavy-duty, turbocharged diesel engine was tested in fully cooled and uncooled modes over the EPA transient emission test cycles for comparison of gaseous and particulate emissions. The results are presented at the same fuel injection timing and at similar NOx emission levels. Also, steady state emission measurements and analysis of real-time transient emission data of selected runs are discussed. The uncooled engine does not represent an adiabatic (insulated) engine in its emission characateristics, but may indicate some trends. It may be useful in identifying design and/or operating parameters that need optimization.
Technical Paper

Measurement and Analysis of the Effect of Wall Temperature on Instantaneous Heat Flux

Measurements of instantaneous temperature were made at three locations on the cylinder head of a direct injection diesel engine. Changes in calculated instantaneous heat flux with changes in cylinder head surface temperature were assessed. The results were used in an assessment of various approaches to the description of instantaneous heat transfer incorporated in diesel cycle simulations. It was concluded that changes in the thermal boundary layer thickness throughout the cycle could account for some of the observed phenomena. A close correlation was seen between the heat transfer measured here and earlier published studies of measured boundary layer thickness. Some additional indications from the measurements point to a significant thermal capacitance of the boundary layer. Additional work is needed to further understand the potential ramifications of this effect.