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Technical Paper

Flow-Acoustic Coupling in Quarter-Wave Resonators Using Computational Fluid Dynamics

2001-04-30
2001-01-1430
Quarter-wave resonators are commonly used as acoustic silencers in automotive air induction systems. Similar closed side branches can also be formed in the idle air bypass, exhaust gas recirculation, and positive crankcase ventilation systems of engines. The presence of a mean flow across these side branches can lead to an interaction between the mean flow and the acoustic resonances of the side branch. At discrete flow conditions, this coupling between the flow and acoustic fields may produce high amplitude acoustic pressure pulsations. For the quarter-wave resonator, this interaction can turn the silencer into a noise generator, while for systems where a valve is located at the closed end of the side branch the large pressure pulsations can cause the valve to fail. This phenomenon is not limited to automotive applications, and also occurs in natural gas pipelines, aircraft, and numerous other internal and external flows.
Technical Paper

Effects of Vehicle Windshield Defrosting and Demisting Process on Passenger Comfort

2001-05-15
2001-01-1729
This paper describes an investigation into the fluid flow and heat transfer on the windshield as well the effect of the air discharge from the defroster vents on passenger comfort. The investigation is both experimental and computational. Full-scale tests are conducted on a current vehicle model using non-intrusive diagnostic methods. The results presented are from numerical simulations validated by experimental measurements. The numerical predictions compare well with the experimental measurements. The locations of maximum velocity and pressure, as well as width and length of re-circulation regions, are correctly predicted.
Technical Paper

Numerical Modeling of Engine Noise Radiation through the use of Acoustic Transfer Vectors - A Case Study

2001-04-30
2001-01-1514
This paper presents the numerical modeling of noise radiated by an engine, using the so-called Acoustic Transfer Vectors and Modal Acoustic Transfer Vectors concept. Acoustic Transfer Vectors are input-output relations between the normal structural velocity of the radiating surface and the sound pressure level at a specific field point and can thus be interpreted as an ensemble of Acoustic Transfer Functions from the surface nodes to a single field point or microphone position. The modal counter part establishes the same acoustic transfer expressed in modal coordinates of the radiating structure. The method is used to evaluate the noise radiated during an engine run-up in the frequency domain. The dynamics of the engine is described using a finite element model loaded with a rpm-dependent excitation. The effectiveness of the method in terms of calculation speed, compared with classical boundary element methods, is illustrated.
Technical Paper

Experimental Study of Automotive Heat Shield Geometry with Natural Convection and Radiation Boundary Conditions

2001-05-14
2001-01-1746
Shielding a vehicle underbody is becoming a daunting task with increased exhaust temperatures due to emissions regulations and ever-increasing packaging constraints, which place components ever closer to exhaust systems. This experimental study was initiated to evaluate the two dimensional thermal effects of heat shield flange height and shield width in vehicle underbody idle conditions. The ultimate goal of this study is to develop a function to optimize the shape of heat shielding to achieve a specified floorpan temperature during vehicle idle conditions.
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

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

Pressure-Sensitive Paint Technology Applied to Low-Speed Automotive Testing

2001-03-05
2001-01-0626
Pressure-sensitive paint (PSP) technology is a technique used to experimentally determine surface pressures on models during wind tunnel tests. The key to this technique is a specially formulated pressure-sensitive paint that responds to, and can be correlated with the local air pressure. Wind tunnel models coated with pressure-sensitive paint are able to yield quantitative pressure data on an entire model surface in the form of light intensity values in recorded images. Quantitative results in terms of pressure coefficients (Cp) are obtained by correlating PSP data with conventional pressure tap data. Only a small number of surface taps are needed to be able to obtain quantitative pressure data with the PSP method. This technique is gaining acceptance so that future automotive wind tunnel tests can be done at reduced cost by eliminating most of the expensive pressure taps from wind tunnel models.
Technical Paper

Overall Results: Phase I Ad Hoc Diesel Fuel Test Program

2001-03-05
2001-01-0151
The future of diesel-engine-powered passenger cars and light-duty vehicles in the United States depends on their ability to meet Federal Tier 2 and California LEV2 tailpipe emission standards. The experimental purpose of this work was to examine the potential role of fuels; specifically, to determine the sensitivity of engine-out NOx and particulate matter (PM) to gross changes in fuel formulation. The fuels studied were a market-average California baseline fuel and three advanced low sulfur fuels (<2 ppm). The advanced fuels were a low-sulfur-highly-hydrocracked diesel (LSHC), a neat (100%) Fischer-Tropsch (FT100) and 15% DMM (dimethoxy methane) blended into LSHC (DMM15). The fuels were tested on modern, turbocharged, common-rail, direct-injection diesel engines at DaimlerChrysler, Ford and General Motors. The engines were tested at five speed/load conditions with injection timing set to minimize fuel consumption.
Technical Paper

Evaluation of Some Alternative Diesel Fuels for Low Emissions and Improved Fuel Economy

2001-03-05
2001-01-0149
This paper reports on Ford's participation in the PNGV ‘Ad Hoc’ Diesel Fuel Test program - Phase I. The purpose of this program was to assess the potential benefits of various fuel properties aimed at reducing engine-out emissions of NOx and particulates to meet LEV2 and Tier 2 emission standards. Four alternative fuels were evaluated using a Ford 1.2L DIATA diesel engine: 1) California Certification fuel (CARB), 2) low sulfur hydro-cracked fuel (LSHC), 3) LSHC fuel with a 15% Dimethoxy Methane blend (DMM), and 4) neat Fischer-Tropsch (FT100) fuel. Design of Experiments (DOE) and conventional techniques were used to evaluate the fuels at five speed and load conditions. Exhaust gas recirculation (EGR), injection rail pressure, and beginning of injection (BOI) timing were controlled during the tests. Steady-state engine performance, emissions, and cylinder pressure (combustion) data were recorded for each fuel.
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

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

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

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

Design and Development of 25% Post-Industrial Recycled SMC Hood Assembly for the 1998 Lincoln Continental Program

1998-02-23
981019
This paper describes the process of incorporation of 25% post-industrial recycled sheet molded composite (SMC) material in the 1998 Continental Hood inner. 1998 Continental Hood assembly consists of traditional SMC outer and this recycled hood inner along with three small steel reinforcements. BUDD Plastics collects SMC scraps from their manufacturing plants. The scrap is then processed and made into fillers for production of SMC. Strength of SMC comes from glass fibers and fillers are added to produce the final mix of raw materials. This recycled material is approximately 10% lighter and less stiff than the conventional virgin SMC. This presented unique challenges to the product development team to incorporate this material into a production vehicle in order to obtain the desired goal of reducing land fill and improving the environment.
Technical Paper

An Experimental Investigation of Spray Transfer Processes in an Electrostatic Rotating Bell Applicator

1998-09-29
982290
A better understanding is needed of the electrostatic rotating bell (ESRB) application of metallic basecoat paint to automobile exteriors in order to exploit their high transfer efficiency without compromising the coating quality. This paper presents the initial results from experimental investigation of sprays from an ESRB which is designed to apply water-borne paint. Water was used as paint surrogate for simplicity. The atomization and transport regions of the spray were investigated using laser light sheet visualizations and phase Doppler particle analyzer (PDPA). The experiments were conducted at varying levels of the three important operating parameters: liquid flow rate, shaping-air flow rate, and bellcup rotational speed. The results show that bellcup speed dominates atomization, but liquid and shaping-air flow rate settings significantly influence the spray structure. The visualization images showed that the atomization occurs in ligament breakup regime.
Technical Paper

Transient CFD Simulations of a Bell Sprayer

1998-09-29
982291
A methodology is developed that incorporates high resolution CFD flowfield information and a particle trajectory simulation, aimed at addressing Paint Transfer Efficiency (PTE) for bell sprayers. Given a solid model for the bell sprayer, the CFD simulation, through automeshing, determines a high resolution Cartesian volume mesh (14-20 million cells). With specified values of the initial shaping air, transient and steady-state flow field information is obtained. A particle trajectory visualization tool called SpraySIM uses this complicated flowfield information to determine the particle trajectories of the paint particles under the influence of drag, gravity and electrostatic potential. The sensitivity of PTE on shaping air velocity, charge-to-mass ratio, potential, and particle diameter are examined.
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.
Technical Paper

A Fuel Vapor Model (FVSMOD) for Evaporative Emissions System Design and Analysis

1998-10-19
982644
A fuel vapor system model (FVSMOD) has been developed to simulate vehicle evaporative emission control system behavior. The fuel system components incorporated into the model include the fuel tank and pump, filler cap, liquid supply and return lines, fuel rail, vent valves, vent line, carbon canister and purge line. The system is modeled as a vented system of liquid fuel and vapor in equilibrium, subject to a thermal environment characterized by underhood and underbody temperatures and heat transfer parameters assumed known or determined by calibration with experimental liquid temperature data. The vapor/liquid equilibrium is calculated by simple empirical equations which take into account the weathering of the fuel, while the canister is modeled as a 1-dimensional unsteady absorptive and diffusive bed. Both fuel and canister submodels have been described in previous publications. This paper presents the system equations along with validation against experimental data.
Technical Paper

Engine and Aftertreatment Modeling for Gasoline Direct Injection

1998-10-19
982596
Engine and aftertreatment models have been developed in support of gasoline direct injection (GDI) engine development and aftertreatment system design. A brief overview of the engine models that were used to project emissions and fuel economy performance for the GDI engine is presented. Additionally, the construction and validation of a NOx trap aftertreatment model is described in considerable detail. The insights and increased understanding which have been gained regarding the trade-offs between engine out emission targets, aftertreatment performance, and emission constrained fuel economy benefits for direct injection gasoline engines are reviewed and discussed.
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