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Technical Paper

Exhaust Manifold Radiated Noise Prediction Methodology

2001-04-30
2001-01-1433
The spark ignition engine is a prime source of vibration energy. NVH disturbances generated by the engine ultimately reach the customer in the form of objectionable noise or NVH. Exhaust Manifolds are one of the many sources of noise contributors among the engine components. Often, the exhaust manifold is identified as a source of objectionable NVH late in the design and development process. Due to the lack of an upfront NVH analysis tool, a new CAE NVH methodology for evaluating new exhaust manifold designs has been investigated and developed by the Ford Motor Company's V-Engine CAE and Exhaust Manifold Design Sections. This new CAE methodology has been developed to compare the NVH performance of current production exhaust manifolds to new design levels. Mechanical induced radiated shell noise is the predominate cause of objectionable NVH in exhaust manifolds.
Technical Paper

Effects of Fuel Injection Pressure in an Optically-Accessed DISI Engine with Side-Mounted Fuel Injector

2001-05-07
2001-01-1975
This paper presents the results of an experimental study into the effects of fuel injection pressure on mixture formation within an optically accessed direct-injection spark-ignition (DISI) engine. Comparison is made between the spray characteristics and in-cylinder fuel distributions due to supply rail pressures of 50 bar and 100 bar subject to part-warm, part-load homogeneous charge operating conditions. A constant fuel mass, corresponding to stoichiometric tune, was maintained for both supply pressures. The injected sprays and their subsequent liquid-phase fuel distributions were visualized using the 2-D laser Mie-scattering technique. The experimental injector (nominally a hollow-cone pressure-swirl design) was seen to produce a dense filled spray structure for both injection pressures under investigation. In both cases, the leading edge velocities of the main spray suggest the direct impingement of liquid fuel on the cylinder walls.
Technical Paper

Fiber Optic Sensor for Crank Angle Resolved Measurements of Burned Gas Residual Fraction in the Cylinder of an SI Engine

2001-05-07
2001-01-1921
A fiber optic infrared spectroscopic sensor was developed to measure the crank angle resolved residual fraction of burned gas retained in the cylinder of a four-stroke SI engine. The sensor detected the attenuation of infrared radiation in the 4.3 μm infrared vibrational-rotational absorption band of CO2. The residual fraction remaining in the cylinder is proportional to the CO2 concentration. The sensor was tested in a single-cylinder CFR spark ignition engine fired on propane at a speed of 700 rpm. The sensor was located in one of two spark plug holes of the CFR engine. A pressure-transducer-type spark plug was used to record the cylinder pressure and initiate the spark. The temporal resolution of the measurements was 540 μs (equivalent to 2.3 crank angle degrees) and the spatial resolution was 6 mm. Measurements were made during the intake and compression stroke for several intake manifold pressures. The compression ratio of the engine was varied from 6.3 to 9.5.
Technical Paper

Air Charge Estimation in Camless Engines

2001-03-05
2001-01-0581
An electromechanically driven valve train offers unprecedented flexibility to optimize engine operation for each speed load point individually. One of the main benefits is the increased fuel economy resulting from unthrottled operation. The absence of a restriction at the entrance of the intake manifold leads to wave propagation in the intake system and makes a direct measurement of air flow with a hot wire air meter unreliable. To deliver the right amount of fuel for a desired air-fuel ratio, we therefore need an open loop estimate of the air flow based on measureable or commanded signals or quantities. This paper investigates various expressions for air charge in camless engines based on quasi-static assumptions for heat transfer and pressure.
Technical Paper

Event-Based Mean-Value Modeling of DI Diesel Engines for Controller Design

2001-03-05
2001-01-1242
Models often use time rather than strokes (crank-angle) as the independent variable to describe engine dynamics despite the fact that the dynamics of an internal combustion engine are intrinsically linked to the combustion events. In this paper, two models are developed in parallel in which not only the independent variable is changed but the notion of mass flows as well: flows are in [g/s] for the time-based model and in [g/st] for the event-based model. Both models are of the same computational complexity and show the same accuracy in validation. The investigation of the model properties shows that variations in the flow-related parameters are reduced by a factor of two to five for the event-based model. However, those of the crankshaft dynamics are increased. It is concluded that the model should be chosen in context of the control system to be designed.
Technical Paper

Quantification of Friction Component Engagement Controllability

2001-03-05
2001-01-1156
Conventional automatic transmissions (AT) use wet friction components, such as plate clutches and band brakes to engage gears or change speed ratios during vehicle operation. The quality of engagements and ratio changes depends greatly on the frictional characteristics of the friction components, which are typically evaluated with industry standard SAE #2 test machines. These inertia absorption-type dynamometer test stands energize a friction component with prescribed level of apply force and load of inertia flywheels rotating at a specified speed until the friction elements are brought to a stop. During the slip, apply force, engagement torque, and rotating speed are digitally recorded for visual evaluation of dynamic engagement behavior. The shape of the dynamic torque curve during the engagement is known to affect AT shift quality. When many curves are generated, it becomes intractable to quantify torque curve shape differences.
Technical Paper

Standard Test Method for Cavitation and Erosion-Corrosion Characteristics of Aluminum Pumps with Engine Coolants

2001-03-05
2001-01-1181
The ASTM D 2809 test method, “Standard Test Method For Cavitation Corrosion and Erosion-Corrosion Characteristics of Aluminum Pumps With Engine Coolants” was first published in 19691. The method involves a copper-pipe circuit through which coolant solution, heated to 113°C, is pumped at 103 kPa for 100 hours. The method was modified to change the pump used in the test in 1989. It was updated in 1994 to accommodate a change in the cleaning procedure and was subsequently reapproved by the ASTM D-15 Committee on Engine Coolants in 1999.2 Tests recently conducted on several modern coolants have produced “failing” results, but the coolants are performing well in the field. Further, the repeatability and reproducibility of the method have been questioned. A round-robin series of tests sponsored by the Ford Motor Company revealed significant variations and cause for concern.
Technical Paper

Effects of Fuel Volatility, Load, and Speed on HC Emissions Due to Piston Wetting

2001-05-07
2001-01-2024
Piston wetting can be isolated from the other sources of HC emissions from DISI engines by operating the engine predominantly on a gaseous fuel and using an injector probe to impact a small amount of liquid fuel on the piston top. This results in a marked increase in HC emissions. In a previous study, we used a variety of pure liquid hydrocarbon fuels to examine the influence of fuel volatility and structure on the HC emissions due to piston wetting. It was shown that the HC emissions correspond to the Leidenfrost effect: fuels with very low boiling points yield high HCs and those with a boiling point near or above the piston temperature produce much lower HCs. All of these prior tests of fuel effects were performed at a single operating condition: the Ford World Wide Mapping Point (WWMP). In the present study, the effects of load and engine speed are examined.
Technical Paper

Flame Temperature Correlation of Emissions from Diesels Operated on Alternative Fuels

2001-05-07
2001-01-2014
Work by Plee, Ahmad, and coworkers in the 1980s [1, 2, 3, 4 and 5] showed that for changes in intake air state, Diesel NOx, soot, soluble organic fraction, and HC emissions could be correlated using the stoichiometric flame temperature calculated at SOC or peak pressure conditions. In the present work, similar flame temperature correlations are obtained for emissions from three test engines; a 1.2L high speed direct injection (HSDI) Diesel, a 2.4L HSDI Diesel, and a 2.34 L single cylinder direct injection (DI) Diesel engine, the first of which was tested using four alternative fuels. Use of the flame temperature correlations presented may reduce the number of engine tests required to evaluate the effects of EGR on emissions of NOx, particulate, and HC, even when alternative fuels are used.
Technical Paper

Experimental Studies on Controlled Auto-ignition (CAI) Combustion of Gasoline in a 4-Stroke Engine

2001-03-05
2001-01-1030
This paper presents results from an experimental programme researching the in-cylinder conditions necessary to obtain gasoline Controlled Auto-ignition (CAI) combustion in a 4-stroke engine. A single-cylinder, variable compression ratio research engine is used for all experiments. Investigations concentrate on establishing the CAI operating range with regard to Air/Fuel ratio and Exhaust Gas Re-circulation (EGR) and their effect on ignition timing, combustion rate and variability, ISFC, and engine-out emissions, such as NOx, CO, and unburned HC. Comprehensive maps for each of the measured variables are presented and in relevant cases, these results are compared to those obtained during normal spark-ignition operation so that the benefits of CAI combustion can be more fully appreciated.
Technical Paper

Modeling of HCCI Combustion and Emissions Using Detailed Chemistry

2001-03-05
2001-01-1029
To help guide the design of homogeneous charge compression ignition (HCCI) engines, single and multi-zone models of the concept are developed by coupling the first law of thermodynamics with detailed chemistry of hydrocarbon fuel oxidation and NOx formation. These models are used in parametric studies to determine the effect of heat loss, crevice volume, temperature stratification, fuel-air equivalence ratio, engine speed, and boosting on HCCI engine operation. In the single-zone model, the cylinder is assumed to be adiabatic and its contents homogeneous. Start of combustion and bottom dead center temperatures required for ignition to occur at top dead center are reported for methane, n-heptane, isooctane, and a mixture of 87% isooctane and 13% n-heptane by volume (simulated gasoline) for a variety of operating conditions.
Technical Paper

Local-Global Finite-Element Analysis for Cam Cover Noise Reduction

2003-05-05
2003-01-1725
Valve covers are a primary source of radiated engine noise. In this paper, we discuss an analytical approach that captures the complicated nonlinear response of the cam cover gaskets and grommets without the need for a prohibitively large finite-element model of the cam cover system. We utilize a detailed local analysis of the gasket and grommet components and abstract their isolation characteristics for later use in a global NVH (Noise-Vibration-Harshness) system analysis.
Technical Paper

PIV Characterization of a 4-valve Engine with a Camshaft Profile Switching (CPS) system

2003-05-19
2003-01-1803
Particle Image Velocimetry (PIV) measurements were performed on a single cylinder optically accesible version of a 3.0L 4-valve engine using a Camshaft Profile Switching (CPS) system. The flow field was investigated at two engine speeds (750 and 1500 rpm), two manifold pressures (75 and 90 kPa) and two intake cam centerlines (maximum lift at 95° and 115° aTDCi respectively). Images were taken in the swirl plane at 10 mm and 40 mm below the deck with the piston at 300° aTDC of intake (60° bTDC compression) and BDC respectively. In the tumble plane, images were taken in a plane bisecting the intake valves with the piston at BDC and 300° aTDC. The results showed that the swirl ratio was slightly lower for this system compared with a SCV system (swirl control valve in the intake port) under the same operating conditions. The swirl and tumble ratios generated were not constant over the range of engine speeds and manifold pressures (MAP) but instead increased with engine speed and MAP.
Technical Paper

Development of Dual Mode Engine Crank Damper

2003-05-05
2003-01-1675
The paper presents development work of dual mode crank dampers implemented on 3.0L V6 engines. The history and the theoretic background of the crank dampers are reviewed. The development starts with measurement of crank bending by modal testing on static condition and by optical decode system on a running engine. Modal analysis theory is also described in the Appendix to explain how the test boundary conditions may greatly affect the measured damper frequencies and a recommended method is presented. The damper frequencies are defined by using transmissibility ratio to simplify the test process and eliminate effects of boundary conditions. To verify the effectiveness of the damper, engine dyno and vehicle road tests are conducted. The results show that the dual mode dampers cannot substantially reduce airborne noise, however they can make engine mount vibrations lower (about 30% in high RPM range) and therefore reduce the structure-borne noise.
Technical Paper

Evaluation of Idle Combustion Stability Using Flywheel Acceleration

2003-05-05
2003-01-1673
Vehicle idle quality has become an increasing quality concern for car manufacturers because of its impact on customer satisfaction. To get better fuel economy the overall trend is to reduce idle speed at both drive and neutral idles. This typically has adverse impact on vehicle idle quality. Lowering the idle rpm generally degrades the engine combustion stability and also makes the engine driving forces more likely to align with vehicle sensitivities (Powertrain rigid body modes, body modes, etc.). To better understand the contribution to the idle quality from different factors and carry out well-planned improvement measures, a quick and easy way to assess engine combustion stability is required.
Technical Paper

Demisting of Vehicle Air Intake Using Plane Baffles

2003-03-03
2003-01-1077
The penetration of rainwater through the heating ventilation and air conditioning system, HVAC, of a vehicle directly affects the provision of thermal comfort within the vehicle passenger compartment. The first element of a typical HVAC system, namely the cowl box is considered. The purpose of the airway from the cowl grille openings to the air filter, immediately before the blower, is to ensure proper water separation from the incoming air stream before entry onto the air filter and onwards into the rest of the HVAC system. This is achieved by ensuring standing water within the cowl is quickly drained and that water rain droplets or water flows from the windshield and body are separated from the air stream, hence minimising the effect on the total system volumetric flow rate. An experimental study is conducted to examine the effect of plane baffles on the airflow filed within a rectangular duct. A set of plane baffle plates is placed within the cowl duct.
Technical Paper

Critical Engine Geometry Generation for Rapid Powertrain Concept Design Assessment

1998-02-23
981090
This paper presents some of the design rules used to calculate critical geometry of engine components, and the object-oriented component hierarchy system in PET. This paper also presents parametric solid model assembling schemes used to dynamically construct an assembly of whole powertrain systems. Some examples of powertrain concept design, such as the estimation of friction, packaging, and moving component clearances, will be presented. The computational efficiency of this concept design method will be compared to traditional methods also.
Technical Paper

Up-Front Prediction of the Effects of Cylinder Head Design on Combustion Rates in SI Engines

1998-02-23
981049
Accurate prediction of engine combustion characteristics, especially burn rates, can eliminate a number of hardware iterations, thus resulting in a significant reduction in design and developmental time and cost. An analytical methodology has been developed which allows the determination of part-load MBT spark timing to within 2 crank-angle degrees. The design methodology employs the in-house-developed steady-state quasi-dimensional engine simulation model (GESIM), coupled with full-field measurement of the in-cylinder fluid motion at bottom dead center (BDC) in the computer-controlled water analog system (AquaDyne). The in-cylinder flow-field measurements are obtained using 3-D Particle Tracking Velocimetry (3-D PTV), also developed in-house. In this methodology, the in-cylinder flow measurement data are used to calibrate both the tumble and swirl models in GESIM.
Technical Paper

Matching Ignition System Multi-Spark Calibration to the Burn-Rate of an Engine to Extend Ignitability Limits

1998-02-23
981046
“Multi-Spark” refers to the charging and discharging of an ignition coil multiple times during a single combustion event. This paper attempts to use multi-sparking to achieve an effect similar to a long duration spark to enhance combustion during slow burn conditions. Although multi-sparking is more typical of capacitive discharge (CDI) ignition systems, this paper discusses the multi-sparking of Kettering ignition systems to achieve the benefits of multi-sparking without CDIs' cost, packaging, complexity and reliability issues. The goal of the multi-spark calibration is to successfully initiate flame kernal development with the first spark discharge and add supplemental energy fast enough through restriking to prevent the flame kernal from quenching.
Technical Paper

Stratified-Charge Engine Fuel Economy and Emission Characteristics

1998-10-19
982704
Data from two engines with distinct stratified-charge combustion systems are presented. One uses an air-forced injection system with a bowl-in-piston combustion chamber. The other is a liquid-only, high-pressure injection system which uses fluid dynamics coupled with a shaped piston to achieve stratification. The fuel economy and emission characteristics were very similar despite significant hardware differences. The contributions of indicated thermal efficiency, mechanical friction, and pumping work to fuel economy are investigated to elucidate where the efficiency gains exist and in which categories further improvements are possible. Emissions patterns and combustion phasing characteristics of stratified-charge combustion are also discussed.
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