Refine Your Search


Search Results

Technical Paper

Material Damping Properties: A Comparison of Laboratory Test Methods and the Relationship to In-Vehicle Performance

This paper presents the damping effectiveness of free-layer damping materials through standard Oberst bar testing, solid plate excitation (RTC3) testing, and prediction through numerical schemes. The main objective is to compare damping results from various industry test methods to performance in an automotive body structure. Existing literature on laboratory and vehicle testing of free-layer viscoelastic damping materials has received significant attention in recent history. This has created considerable confusion regarding the appropriateness of different test methods to measure material properties for damping materials/treatments used in vehicles. The ability to use the material properties calculated in these tests in vehicle CAE models has not been extensively examined. Existing literature regarding theory and testing for different industry standard damping measurement techniques is discussed.
Technical Paper

Advanced Computational Methods for Predicting Flow Losses in Intake Regions of Diesel Engines

A computational methodology has been developed for loss prediction in intake regions of internal combustion engines. The methodology consists of a hierarchy of four major tasks: (1) proper computational modeling of flow physics; (2) exact geometry and high quality and generation; (3) discretization schemes for low numerical viscosity; and (4) higher order turbulence modeling. Only when these four tasks are dealt with properly will a computational simulation yield consistently accurate results. This methodology, which is has been successfully tested and validated against benchmark quality data for a wide variety of complex 2-D and 3-D laminar and turbulent flow situations, is applied here to a loss prediction problem from industry. Total pressure losses in the intake region (inlet duct, manifold, plenum, ports, valves, and cylinder) of a Caterpillar diesel engine are predicted computationally and compared to experimental data.
Technical Paper

Coordinated Control of Multi-Degree-of Freedom Fuel Systems

This paper identifies potential performance benefits and computational costs of applying advanced multivariable control theory concepts to coordinate the control of a general multi-degree-of-freedom fuel system. The control variables are injection duration and pressure. The focus is on the design of a robust multi-input multi-output controller using H-infinity and mu synthesis methodology to coordinate the control of injection duration and pressure; reduce overshoots and system sensitivity to parameter variations caused by component aging. Model reduction techniques are used to reduce the order of the H-infinity controller to make it practically implementable. Computer simulation is used to test the robust performance of a generic engine and fuel system model controlled by the reduced order H-infinity controller and a traditional proportional plus integral controller.
Technical Paper

A Comparison of Time-Averaged Piston Temperatures and Surface Heat Flux Between a Direct-Fuel Injected and Carbureted Two-Stroke Engine

Time-averaged temperatures at critical locations on the piston of a direct-fuel injected, two-stroke, 388 cm3, research engine were measured using an infrared telemetry device. The piston temperatures were compared to data [7] of a carbureted version of the two-stroke engine, that was operated at comparable conditions. All temperatures were obtained at wide open throttle, and varying engine speeds (2000-4500 rpm, at 500 rpm intervals). The temperatures were measured in a configuration that allowed for axial heat flux to be determined through the piston. The heat flux was compared to carbureted data [8] obtained using measured piston temperatures as boundary conditions for a computer model, and solving for the heat flux. The direct-fuel-injected piston temperatures and heat fluxes were significantly higher than the carbureted piston. On the exhaust side of the piston, the direct-fuel injected piston temperatures ranged from 33-73 °C higher than the conventional carbureted piston.
Technical Paper

A 2-D Computational Model Describing the Flow and Filtration Characteristics of a Ceramic Diesel Particulate Trap

A 2-D computational model was developed to describe the flow and filtration processes, in a honeycomb structured ceramic diesel particulate trap. This model describes the steady state trap loading, as well as the transient behavior of the flow and filtration processes. The theoretical model includes the effect of a copper fuel additive on trap loading and transient operation. The convective terms were based on a 2-D analytical flow field solution derived from the conservation of mass and momentum equations. The filtration theory incorporated in the time dependent numerical code included the diffusion, inertia, and direct interception mechanisms. Based on a measured upstream particle size distribution, using the filtration theory, the downstream particle size distribution was calculated. The theoretical filtration efficiency, based on particle size distribution, agreed very well (within 1%) with experimental data for a number of different cases.
Technical Paper

A 2-D Computational Model Describing the Heat Transfer, Reaction Kinetics and Regeneration Characteristics of a Ceramic Diesel Particulate Trap

A 2-D CFD model was developed to describe the heat transfer, and reaction kinetics in a honeycomb structured ceramic diesel particulate trap. This model describes the steady state as well as the transient behavior of the flow and heat transfer during the trap regeneration processes. The trap temperature profile was determined by numerically solving the 2-D unsteady energy equation including the convective, heat conduction and viscous dissipation terms. The convective terms were based on a 2-D analytical flow field solution derived from the conservation of mass and momentum equations (Opris, 1997). The reaction kinetics were described using a discretized first order Arrhenius function. The 2-D term describing the reaction kinetics and particulate matter conservation of mass was added to the energy equation as a source term in order to represent the particulate matter oxidation. The filtration model describes the particulate matter accumulation in the trap.
Technical Paper

The Dimensionless Correlation of Airflow for Vehicle Engine Cooling Systems

An analysis of vehicle engine cooling airflow by means of a one-dimensional, transient, compressible flow model was carried out and revealed that similarity theory could be applied to investigate the variation of the airflow with ambient and operating conditions. It was recognized that for a given vehicle engine cooling system, the cooling airflow behavior could be explained using several dimensionless parameters that involve the vehicle speed, fan speed, heat transfer rate through the radiator, ambient temperature and pressure, and the system characteristic dimension. Using the flow resistance and fan characteristics measured from a prototype cooling system and the computer simulation for the one-dimensional compressible flow model, a quantitative correlation of non-dimensional mass flow rate to three dimensionless parameters for a prototype heavy-duty truck was established. The results are presented in charts, tables, and formulas.
Technical Paper

Numerical Simulation of Quenching Process at Caterpillar

Caterpillar uses heat treatment to enhance the properties of a significant number of parts. Traditional heat treat process optimization is both time consuming and expensive when done by empirical methods. This paper describes a computer simulation of the heat treatment process, developed by Caterpillar, based upon finite element analysis. This approach combines thermal, microstructural, and stress analysis to accurately model material transformation during quenching. Examples are presented to illustrate the program.
Technical Paper

The Application of Boundary Element Analysis to Engine Component Design

Boundary element analysis (BEA) is an effective computer simulation program for certain applications in design engineering. The BEA technique has been used extensively at Caterpillar for structural analysis of engine and vehicle components. The time savings and modeling ease of BEA are illustrated with specific examples of engine component models. These examples represent a variety of modeling techniques, and include comparisons with measured test data.
Technical Paper

A New Validation of Spray Penetration Models for Modern Heavy Duty Diesel Fuel Injectors

The performance of five positive k-factor injector tips has been assessed in this work by analyzing a comprehensive set of injected mass, momentum, and spray measurements. Using high speed shadowgraphs of the injected diesel plumes, the sensitivities of measured vapor penetration and dispersion to injection pressure (100-250MPa) and ambient density (20-52 kg/m3) have been compared with the Naber-Siebers empirical spray model to gain understanding of second order effects of orifice diameter. Varying in size from 137 to 353μm, the orifice diameters and corresponding injector tips are appropriate for a relatively wide range of engine cylinder sizes (from 0.5 to 5L). In this regime, decreasing the orifice exit diameter was found to reduce spray penetration sensitivity to differential injection pressure. The cone angle and k-factored orifice exit diameter were found to be uncorrelated.
Technical Paper

The Effects of a Porous Ceramic Particulate Trap on the Physical, Chemical and Biological Character of Diesel Particulate Emissions

Physical, chemical, and biological characterization data for the particulate emissions from a Caterpillar 3208 diesel engine with and without Corning porous ceramic particulate traps are presented. Measurements made at EPA modes 3,4,5,9,lO and 11 include total hydrocarbon, oxides of nitrogen and total particulate matter emissions including the solid fraction (SOL), soluble organic fraction (SOF) and sulfate fraction (SO4), Chemical character was defined by fractionation of the SOF while biological character was defined by analysis of Ames Salmonella/ microsome bioassay data. The trap produced a wide range of total particulate reduction efficiencies (0-97%) depending on the character of the particulate. The chemical character of the SOF was significantly changed through the trap as was the biological character. The mutagenic specific activity of the SOF was generally increased through the trap but this was offset by a decrease in SOF mass emissions.
Technical Paper

The Design and Testing of a Computer-Controlled Cooling System for a Diesel-Powered Truck

The hardware and software for a prototype computer controlled cooling system for a diesel powered truck has been designed and tested. The basic requirements for this system have been defined and the control functions, previously investigated in a study using the computer simulation model, were incorporated into the software. Engine dynamometer tests on the MACK-676 engine, comparing the conventional cooling system and the computer controlled system, showed the following advantages of the computer controlled system: 1. The temperature level to which the engine warms up to at low ambient temperature, was increased. 2. The faster shutter response reduced the temperature peaks and decreased total fan activity time. 3. The faster fan response reduces fan engagement time which should improve truck fuel economy.
Technical Paper

Development of a 1-D CPF Model to Simulate Active Regeneration of a Diesel Particulate Filter

A quasi-steady 1-dimensional computer model of a catalyzed particulate filter (CPF) capable of simulating active regeneration of the CPF via diesel fuel injection upstream of a diesel oxidation catalyst (DOC) or other means to increase the exhaust gas temperature has been developed. This model is capable of predicting gaseous species concentrations (HC's, CO, NO and NO2) and exhaust gas temperatures within and after the CPF, for given input values of gaseous species and PM concentrations before the CPF and other inlet variables such as time-varying temperature of the exhaust gas at the inlet of the CPF and volumetric flow rate of exhaust gas.
Technical Paper

Experimental Studies of an Advanced Ceramic Diesel Particulate Filter

A Cummins ISB 5.9 liter medium-duty engine with cooled EGR has been used to study an early extrusion of an advanced ceramic uncatalyzed diesel particulate filter (DPF). Data for the advanced ceramic material (ACM) and an uncatalyzed cordierite filter of similar dimensions are presented. Pressure drop data as a function of mass loadings (0, 4, and 6 grams of particulate matter (PM) per liter of filter volume) for various flow rate/temperature combinations (0.115 - 0.187 kg/sec and 240 - 375 °C) based upon loads of 15, 25, 40 and 60% of full engine load (684 N-m) at 2300 rpm are presented. The data obtained from these experiments were used to calibrate the MTU 1-D 2-Layer computer model developed previously at MTU. Clean wall permeability determined from the model calibration for the ACM was 5.0e-13 m2 as compared to 3.0e-13 m2 for cordierite.
Technical Paper

A Methodology to Estimate the Mass of Particulate Matter Retained in a Catalyzed Particulate Filter as Applied to Active Regeneration and On-Board Diagnostics to Detect Filter Failures

A methodology to estimate the mass of particulate retained in a catalyzed particulate filter as a function of measured total pressure drop, volumetric flow rate, exhaust temperature, exhaust gas viscosity and cake and wall permeability applicable to real-time computation is discussed. This methodology is discussed from the view point of using it to indicate when to initiate active regeneration and as an On-Board Diagnostic tool to detect filter failures. Steady-state loading characterization experiments were conducted on a catalyzed diesel particulate filter (CPF) in a Johnson Matthey CCRT® (catalyzed continuously regenerating trap) system. The experiments were performed using a 10.8 L 2002 Cummins ISM heavy-duty diesel engine. Experiments were conducted at 20, 60 and 75% of full engine load (1120 Nm) and rated speed (2100 rpm) to measure the pressure drop, transient filtration efficiency, particulate mass balance, and gaseous emissions.
Technical Paper

Multivariate Regression and Generalized Linear Model Optimization in Diesel Transient Performance Calibration

With stringent emission regulations, aftertreatment systems with a Diesel Particulate Filter (DPF) and a Selective Catalytic Reduction (SCR) are required for diesel engines to meet PM and NOx emissions. The adoption of aftertreatment increases the back pressure on a typical diesel engine and makes engine calibration a complicated process, requiring thousands of steady state testing points to optimize engine performance. When configuring an engine to meet Tier IV final emission regulations in the USA or corresponding Stage IV emission regulations in Europe, this high back pressure dramatically impacts transient performance. The peak NOx, smoke and exhaust temperature during a diesel engine transient cycle, such as the Non-Road Transient Cycle (NRTC) defined by the US Environmental Protection Agency (EPA), will in turn affect the performance of the aftertreatment system and the tailpipe emissions level.
Technical Paper

The Impact of Fuel Properties on Diesel Engine Emissions and a Feasible Solution for Common Calibration

Fuel properties impact the engine-out emission directly. For some geographic regions where diesel engines can meet emission regulations without aftertreatment, the change of fuel properties will lead to final tailpipe emission variation. Aftertreatment systems such as Diesel Particulate Filter (DPF) and Selective Catalytic Reduction (SCR) are required for diesel engines to meet stringent regulations. These regulations include off-road Tier 4 Final emission regulations in the USA or the corresponding Stage IV emission regulations in Europe. As an engine with an aftertreatment system, the change of fuel properties will also affect the system conversion efficiency and regeneration cycle. Previous research works focus on prediction of engine-out emission, and many are based on chemical reactions. Due to the complex mixing, pyrolysis and reaction process in heterogeneous combustion, it is not cost-effective to find a general model to predict emission shifting due to fuel variation.
Technical Paper

Prediction and Measurement of Microstructure and Residual Stresses due to Electron Beam Welding Process

Electron beam (EB) welding process is characterized by an extremely high power density that is capable of producing weld seams which are considerably deeper than width. Unlike other welding process, heat of EB welding is provided by the kinetic energy of electrons. This paper presents a computational model for the numerical prediction of microstructure and residual stress resulting from EB welding process. Energy input is modeled as a step function within the fusion zone. The predicted values from finite element simulation of the EB welding process agree well with the experimentally measured values. The present model is used to study an axial weld failure problem.
Technical Paper

Assessment of CFD Methods for Large Diesel Engines Equipped with a Common Rail Injection System

A KIVA-based CFD tool has been utilized to simulate the effect of a Common-Rail injection system applied to a large, uniflow-scavenged, two-stroke diesel engine. In particular, predictions for variations of injection pressure and injection duration have been validated with experimental data. The computational models have been evaluated according to their predictive capabilities of the combustion behavior reflected by the pressure and heat release rate history and the effects on nitric oxide formation and wall temperature trends. In general, the predicted trends are in good agreement with the experimental observations, thus demonstrating the potential of CFD as a design tool for the development of large diesel engines equipped with Common-Rail injection. Existing deficiencies are identified and can be explained in terms of model limitations, specifically with respect to the description of turbulence and combustion chemistry.
Technical Paper

Thermal and Chemical Aging of Diesel Particulate Filters

The effects of thermal and chemical aging on the performance of cordierite-based and high-porosity mullite-based diesel particulate filters (DPFs), were quantified, particularly their filtration efficiency, pressure drop, and regeneration capability. Both catalyzed and uncatalyzed core-size samples were tested in the lab using a diesel fuel burner and a chemical reactor. The diesel fuel burner generated carbonaceous particulate matter with a pre-specified particle-size distribution, which was loaded in the DPF cores. As the particulate loading evolved, measurements were made for the filtration efficiency and pressure drop across the filter using, respectively, a Scanning Mobility Particle Sizer (SMPS) and a pressure transducer. In a subsequent process and on a different bench system, the regeneration capability was tested by measuring the concentration of CO plus CO2 evolved during the controlled oxidation of the carbonaceous species previously deposited on the DPF samples.