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Technical Paper

Noise Analysis of Automotive Alternators

1999-05-17
1999-01-1712
An extensive experimental study of noise generating mechanisms of two production models of automotive alternators is presented. It was established that aerodynamic noise (generated by cooling fans) is dominating at high speeds (above 3,000 rpm), while electromagnetic noise is the most intensive at low rpm. Two directions of noise reduction are proposed and validated: reduction of noise levels generated by alternators to be achieved by using axial flow fans for cooling instead of presently used bladed discs, and radical reduction of operating speed of alternators by using variable transmission ratio accessory drives.
Technical Paper

A Mathematical Model for Design and Production Verification Planning

1999-05-10
1999-01-1624
The paper focuses on various important decisions of verification and testing plans of the product during its design and production stages. In most of the product and process development projects, decisions on verification and testing are ad-hoc or based on traditions. Such decisions never guarantee the performance of the product as planned, during its whole life cycle. We propose an analytical approach to provide the concrete base for such crucial decisions of verification planning. Accordingly, a mathematical model is presented. Also, a case study of an automotive Electro-mechanical product is included to illustrate the application of the model.
Technical Paper

Characteristics of Direct Injection Gasoline Spray Wall Impingement at Elevated Temperature Conditions

1999-10-25
1999-01-3662
The direct injection gasoline spray-wall interaction was characterized inside a heated pressurized chamber using various visualization techniques, including high-speed laser-sheet macroscopic and microscopic movies up to 25,000 frames per second, shadowgraph, and doublespark particle image velocimetry. Two hollow cone high-pressure swirl injectors having different cone angles were used to inject gasoline onto a heated plate at two different impingement angles. Based on the visualization results, the overall transient spray impingement structure, fuel film formation, and preliminary droplet size and velocity were analyzed. The results show that upward spray vortex inside the spray is more obvious at elevated temperature condition, particularly for the wide-cone-angle injector, due to the vaporization of small droplets and decreased air density. Film build-up on the surface is clearly observed at both ambient and elevated temperature, especially for narrow cone spray.
Technical Paper

Direct Calculations of Cavitating Flows in Fuel Delivery Pipe by the Space-Time CE/SE Method

1999-10-25
1999-01-3554
In this paper, we report direct calculations of cavitating pipe flows by the method of Space-Time Conservation Element and Solution Element, or the CE/SE method for short. The tenet of the CE/SE method is treating space and time as one entity, and the calculation of flow properties is based on the local and global space-time flux conservation. As a contrast to the modern upwind schemes, no Riemann solver is used, thus the logic of the present scheme for cavitating flows is much simpler. Two numerical examples are reported in this paper: (1) a hydraulic shock problem, and (2) a cavitating pipe flow. For the hydraulic shock problem, we demonstrate the capability of the CE/SE method for capturing contact discontinuities in cavitating fluids. For the pipe flows, a two-phase homogeneous equilibrium cavitation model is employed. In both cases, numerical results compared favorably with the experimental data and analytical solution.
Technical Paper

Correlating the Diesel Spray Behavior to Nozzle Design

1999-10-25
1999-01-3555
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

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

2000-03-06
2000-01-1256
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

A New Ignition Delay Formulation Applied to Predict Misfiring During Cold Starting of Diesel Engines

2000-03-06
2000-01-1184
A new formulation is developed for the ignition delay (ID) in diesel engines to account for the effect of piston motion on the global autoignition reaction rates. A differentiation is made between the IDe measured in engines and IDv, measured in constant volume vessels. In addition, a method is presented to determine the coefficients of the IDe correlation from actual engine experimental data. The new formulation for IDe is applied to predict the misfiring cycles during the cold starting of diesel engines at different low ambient temperatures. The predictions are compared with experimental results obtained on a multi-cylinder heavy-duty diesel engine.
Technical Paper

Combustion Visualization of DI Diesel Spray Combustion inside a Small-Bore Cylinder under different EGR and Swirl Ratios

2001-05-07
2001-01-2005
An experimental setup using rapid compression machine to provide excellent optical access to visualize simulated high-speed small-bore direct injection diesel engine combustion processes is described. Typical combustion visualization results of diesel spray combustion under different EGR, swirl, and injection pressure and nozzle conditions are presented. Different swirl intensities are achieved using an air nozzle with variable orientations and a check valve to connect the compression chamber and the combustion chamber. Different EGR ratios are achieved by pre-injection of diesel fuel prior to the main observation sequence. Clear visualization of the high-pressure fuel injection, ignition, combustion and spray/wall/swirl interactions is obtained. The injection system is a high-pressure common-rail system with either a VCO or a mini-sac nozzle. High-speed movies up to 35,000 frame-per-second are taken using a framing drum camera to record the combustion events.
Technical Paper

Visualization and Analysis of the Impingement Processes of a Narrow-Cone DI Gasoline Spray

2001-05-07
2001-01-2023
The direct injection spray-wall interactions were investigated experimentally using high-speed laser-sheet imaging, shadowgraphy, wetted footprints and phase Doppler interferometry techniques. A narrow-cone high-pressure swirl injector is used to inject iso-octane fuel onto a plate, at three different impact angles inside a pressurized chamber. Heated air and plate conditions were compared with unheated cases. Injection interval was also varied in the heated case to compare dry- and wet- wall impingement behaviors. High-speed macroscopic Mie-scattering images showed that presence of wall and air temperature has only minor effect on the bulk spray structure and penetration speed for the narrow-cone injector tested. The overall bulk motions of the spray plume and its spatial position at a given time are basically unaffected until a few millimeters before impacting the wall.
Technical Paper

Quantitative Measurements of Direct-Injection Gasoline Fuel Sprays in Near-Nozzle Region Using Synchrotron X-Ray

2001-03-05
2001-01-1293
A quantitative and time-resolved technique has been developed to probe the dense spray structure of direct-injection (DI) gasoline sprays in near-nozzle region. This technique uses the line-of-sight absorption of monochromatic x-rays from a synchrotron source to measure the fuel mass with time resolution better than 1 μs. The small scattering cross-section of fuel at x-rays regime allows direct measurements of spray structure that are difficult with most visible-light optical techniques. Appropriate models were developed to determine the fuel density as a function of time.
Technical Paper

Diesel Engine Cold Start Combustion Instability and Control Strategy

2001-03-05
2001-01-1237
Combustion instability and white smoke emissions are serious problems during cold starting of diesel engines. In this investigation, a model has been applied to predict misfiring based on an analysis of the autoignition process. The effect of injection timing on combustion instability during the cold start transient, at different ambient temperatures is investigated, both theoretically and experimentally. Maps have been developed to show the zones where misfiring would occur. The experimental work was conducted on a direct injection heavy-duty diesel engine in a cold room. The room temperature covered a range from 21 ° C to -10 ° C. The cycle-by-cycle data analysis was made and results plotted on the developed maps. The experimental results correlated fairly well with the model prediction. Based on the analysis, a new strategy for cold starting can be developed to reduce combustion instability and white smoke emissions.
Technical Paper

Emissions Trade-Off and Combustion Characteristics of a High-Speed Direct Injection Diesel Engine

2001-03-05
2001-01-0197
The emissions trade-off and combustion characteristics of a high speed, small-bore, direct injection, single cylinder, diesel engine are investigated at three different load conditions. The experiments covered a wide range of parameters including the injection pressure, exhaust gas recirculation (EGR) rate and swirl ratio (Sw). The effects of each parameter on the ignition delay (ID), apparent rate of energy release (ARER), NOx, Bosch smoke unit (BSU), CO and hydrocarbons are investigated. The results show that the NOx emission dropped continuously with the increase in EGR (up to 55%), but with increasing smoke emission in a classical trade-off relationship. The increase in injection pressure generally reduced smoke with NOx penalty; however, the NOx penalty decreased at higher EGR. There also appears to be an increase in the cool flame intensity at the high EGR rates. Applying swirl at high EGR rate and high injection pressure conditions further reduced smoke emissions.
Technical Paper

Active Damping of Engine Idle Speed Oscillation by Applying Adaptive Pid Control

2001-03-05
2001-01-0261
This paper investigates the use of an adaptive proportional-integral-derivative (APID) controller to reduce a combustion engine crankshaft speed pulsation. Both computer simulations and engine test rig experiments are used to validate the proposed control scheme. The starter/alternator (S/A) is used as the actuator for engine speed control. The S/A is an induction machine. It produces a supplemental torque source to cancel out the fast engine torque variation. This machine is placed on the engine crankshaft. The impact of the slowly varying changes in engine operating conditions is accounted for by adjusting the APID controller parameters on-line. The APID control scheme tunes the PID controller parameters by using the theory of adaptive interaction. The tuning algorithm determines a set of PID parameters by minimizing an error function. The error function is a weighted combination of the plant states and the required control effort.
Technical Paper

Frictional Characteristics of Plasma Spray Coated Cylinder Bores

1999-03-01
1999-01-1220
Low cost and solid lubricant containing plasma spray coated cylinder liners have been investigated for their frictional performance under simulated engine conditions. A bench testing system which has high stroke and large contact width has been used to obtain friction data for plasma spray coated cylinder liners. Results are compared with conventional cast-iron samples. Experimental data has been developed as friction coefficient / crank angle degree diagrams. The effects of speed and temperature have been investigated. Plasma spray coated cylinder liners showed lower friction and higher tendency to develop hydrodynamic lubrication compared to conventional cast-iron bores.
Technical Paper

Effect of Cetane Number with and without Additive on Cold Startability and White Smoke Emissions in a Diesel Engine

1999-05-03
1999-01-1476
I The effect of Cetane Number (CN) of the fuel and the addition of cetane improvers on the cold starting and white smoke emissions of a diesel engine was investigated. Tests were conducted on a single-cylinder, four-stroke-cycle, air-cooled, direct-injection, stand-alone diesel engine in a cold room at ambient temperatures ranging from 25 °C to - 5 °C. Five fuels were used. The base fuel has a CN of 49.2. The CN of the base fuel was lowered to 38.7 and 30.8 by adding different amounts of aromatic hydrocarbons. Iso-octyl nitrate is added to the high aromatic fuels in order to increase their CN to 48.6 and 38.9 respectively. Comparisons are made between the five fuels to determine the effect of CN and the additive on cylinder peak pressure, heat release rate, cold start-ability, combustion instability, hydrocarbon emissions and solid and liquid particulates.
Technical Paper

A Simplified Friction Model of the Piston Ring Assembly

1999-03-01
1999-01-0974
This paper presents a simplified piston ring assembly (PRA) friction model accounting for the piston ring pack and the piston skirt. The ring model considers both mixed and hydrodynamic lubrication; the skirt model considers hydrodynamic lubrication only. The Reynold's equation is used as a governing equation for the hydrodynamic regimes of both models. Simplified assumptions are used for the mixed lubrication in the ring model. The ring model generates unique Stribeck curves for a given ring's geometry; the skirt model generates generic relationships between the friction force and skirt geometry, piston speed, oil viscosity, and assumed boundary conditions. Ring starvation effects are introduced by varying the boundary conditions, as appropriate. The results of the models are compared to measurements made on a motored and fired single cylinder diesel engine; the theoretical calculations provide a reasonable estimate of the measured data.
Technical Paper

A Hybrid System Solution of the Interrupt Latency Compatibility Problem

1999-03-01
1999-01-1099
Microprocessors and microcontrollers are now widely used in automobiles. Microprocessor systems contain sources of interrupt and interrupt service routines, which are software components executed in response to the assertion of an interrupt in hardware. A major problem in designing the software of microprocessor systems is the analytical treatment of interrupt latency. Because multiple interrupt service routines are executed on the same CPU, they compete for the CPU and interfere with each other's latency requirements. Here, interrupt latency is defined as the delay between the assertion of the interrupt in hardware and the start of execution of the associated interrupt service routine. It is estimated that 80% of intermittent bugs in small microprocessor software loads are due to improper treatment of interrupts. Until this work, there is no analytic method for analyzing a particular system to determine if it may violate interrupt latency requirements.
Technical Paper

Modeling of Dynamic Responses of Injectors for an Automotive Fuel Rail System

1999-03-01
1999-01-0795
This paper presents a computer model for simulating dynamic responses inside an injector of an automotive fuel rail system. The injector contains a filter at the top, a coil spring in the middle, and a needle and orifices at the bottom. The equations of motion for unsteady one-dimensional flow are derived for the fluid flowing through the injector. The needle motion is described by a second order ordinary differential equation. The forces exerted on the needle include the magnetic force that controls the opening and closing of the injector and the coil spring force. To account for the loss of kinetic energy, we define two loss factors Ka and Kb. The former describes the loss of kinetic energy as fluid enters the injector through the filter at the top, and the latter depicts that as fluid is ejected into a large chamber through the passage between the needle and the needle seat and across four orifices at the bottom of the injector.
Technical Paper

A Visualization Study of Liquid Fuel Distribution and Combustion Inside a Port-Injected Gasoline Engine Under Different Start Conditions

2000-03-06
2000-01-0242
High-speed video of combustion processes and cylinder pressure traces were obtained from a single-cylinder optical-accessible engine with a production four-valve cylinder head to study the mixture formation and flame propagation characteristics at near-stoichiometric start condition. Laser-sheet Mie-scattering images were collected for liquid droplet distributions inside the cylinder to correlate the mixture formation process with the combustion results. A dual-stream (DS) injector and a quad-stream (QS) injector were used to study the spray dispersion effect on engine starting, under different injection timings, throttle valve positions, engine speeds, and intake temperatures. It was found that most of the fuel under open-valve injection (OVI) conditions entered the cylinder as droplet mist. A significant part of the fuel droplets hit the far end of the cylinder wall at the exhaust-valve side.
Technical Paper

A Warpage Measurement System with Large Dynamic Range for Boards with Components

2000-03-06
2000-01-0458
A new algorithm for carrier removal, a key step in the Fourier transform method of fringe pattern analysis, is presented in this paper. The accuracy of frequency estimations is critical to carrier removal to avoid potential significant errors in the recovered phase. A new algorithm on Fourier transform and curve fitting technique is developed. To avoid an ill-conditioned result in solving the least-square problem, an orthogonal polynomial curve fitting algorithm is developed. A new system that combines projected grating moiré (PM) with shadow moiré (SM), recently designed and built with large dynamic range for both component level and board level warpage measurement for the reliability study of electronic packaging materials and structures, is presented and demonstrated.
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