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Technical Paper

Effect of Gas Density and the Number of Injector Holes on the Air Flow Surrounding Non-Evaporating Transient Diesel Sprays

2001-03-05
2001-01-0532
The effect of ambient gas density and the number of injector holes on the characteristics of airflow surrounding non-evaporating transient diesel sprays inside a constant volume chamber were investigated using a 6-hole injector. Particle Image Velocimetry (PIV) was used to measure the gas velocities surrounding a spray plume as a function of space and time. A conical control surface surrounding the spray plume was chosen as a representative side entrainment surface. The positive normal velocities across the control surface of single-hole injection sprays were higher than those of 6-hole injection sprays. An abrupt increase in velocities tangential to the control surface near the chamber wall suggests that the recirculation of surrounding gas is accelerated by spray wall impingement.
Technical Paper

Optimizing the University of Wisconsin's Parallel Hybrid-Electric Aluminum Intensive Vehicle

2000-03-06
2000-01-0593
The University of Wisconsin - Madison FutureCar Team has designed and built a lightweight, charge sustaining, parallel hybrid-electric vehicle for entry into the 1999 FutureCar Challenge. The base vehicle is a 1994 Mercury Sable Aluminum Intensive Vehicle (AIV), nicknamed the “Aluminum Cow,” weighing 1275 kg. The vehicle utilizes a high efficiency, Ford 1.8 liter, turbo-charged, direct-injection compression ignition engine. The goal is to achieve a combined FTP cycle fuel economy of 23.9 km/L (56 mpg) with California ULEV emissions levels while maintaining the full passenger/cargo room, appearance, and feel of a full-size car. Strategies to reduce the overall vehicle weight are discussed in detail. Dynamometer and experimental testing is used to verify performance gains.
Technical Paper

Gas Efficient Liquid Atomization Using Micro-Machined Spray Nozzles

1996-02-01
960859
Improved atomization is important in fuel injection applications since atomization influences fuel-air mixing and vaporization rates. The present paper explores the use of low pressure gas/air injection and methods to achieve a dispersed two-phase flow to enhance the atomization process. Gas-driven twin-fluid atomization has been achieved by combining X-ray lithographic/micro-machining technology to mechanically disperse a driving gas into a liquid to be sprayed. This technique forces the gas through a designed pattern of micron sized holes thereby yielding a field of micro-bubbles immediately upstream of the < I mm. diameter discharge orifice. Precise control of both uniformity of hole diameter and inter-hole spacing is critical to producing a well dispersed bubbly flow. The results show that the method of gas injection influences the liquid breakup process. Results are given for steady-flow atomization with low pressure injection into ambient air.
Technical Paper

Control of Grasping Force in Teleoperation Using Model Reference Adaptive Approach

1994-06-01
941440
The adaptation to changes in human operator dynamics and changes in working environment dynamics can be an important issue in designing high performance telerobotic systems. This paper describes an approach to force control in telerobotic hand systems in which model reference adaptive control techniques are used to adapt to changes in human operator and working environment dynamics. The techniques have been applied to force-reflective control of a single degree-of-freedom telerobotic gripper system at Wisconsin Center for Space Automation and Robotics (WCSAR). This adaptive gripping system is described in the paper along with results of experiments with human subjects in which the performance of the adaptive system was analysed and compared to the performance of a conventional non-adaptive system. These experiments emphasized adaptation to changes in compliance of gripped objects and adaptation to the on-set of human operator fatigue.
Technical Paper

Measurement and Modeling of Thermal Flows in an Air-Cooled Engine

1996-08-01
961731
Control of the flow of thermal energy in an air-cooled engine is important to the overall performance of the engine because of potential effects on engine performance, durability, design, and emissions. A methodology is being developed for the assessment of thermal flows in air-cooled engines, which includes the use of cycle simulation and in-cylinder heat flux measurements. The mechanism for the combination of cycle simulation, the measurement of in-cylinder heat flux and wall temperatures, and comparison of predicted and measured heat flux in the methodology is presented. The methodology consists of both simulation and experimental phases. To begin, a one-dimensional gas dynamics code (WAVE) has been used in conjunction with a detailed in-cylinder flow and combustion model (IRIS) in order to simulate engine operation in a variety of operating conditions. The methods used to apply the model to the air-cooled engine case are described in detail.
Technical Paper

The Effects of Mixture Stratification on Combustion in a Constant-Volume Combustion Vessel

1998-02-01
980159
The role of mixture stratification on combustion rate has been investigated in a constant volume combustion vessel in which mixtures of different equivalence ratios can be added in a spatially and temporally controlled fashion. The experiments were performed in a regime of low fluid motion to avoid the complicating effects of turbulence generated by the injection of different masses of fluid. Different mixture combinations were investigated while maintaining a constant overall equivalence ratio and initial pressure. The results indicate that the highest combustion rate for an overall lean mixture is obtained when all of the fuel is contained in a stoichiometric mixture in the vicinity of the ignition source. This is the result of the high burning velocity of these mixtures, and the complete oxidation which releases the full chemical energy.
Technical Paper

The Effects of Wall Temperature on Flame Structure During Flame Quenching

1994-03-01
940683
The effect of wall temperature on single surface flame quenching and flame structure of an atmospheric premixed methane-air flame was studied. The luminous region of a laminar flame was located at an angle of 45 degrees to a temperature- controlled surface. C2 laser-induced fluorescence was used as an indicator of flame position while Raman spectroscopy was used to determine gas temperature profiles near the surface. These measurements were conducted for wall positions (vertical distance from the surface) ranging from 50 mm to 1.0 mm and wall temperatures ranging from 150 °C to 600 °C. C2 laser-induced fluorescence measurements indicated flame position is affected by the presence of a surface and the surface temperature. Larger C2 fluorescence intensity values were observed for higher wall temperatures at all distances from the surface.
Technical Paper

Predictions of Residual Gas Fraction in IC Engines

1996-10-01
962052
It is well known that the accuracy of simulations of combustion processes in diesel and spark ignited (SI) engines depends on the initial conditions within the cylinder at intake valve closure (IVC). Residual gas affects the engine combustion processes through its influence on charge mass, temperature and dilution. In SI engines, there is little oxygen in the residual gas, and thus the dilution effect on flame propagation is more significant than in compression ignited (CI) engines. However, in CI engines, the ignition delay depends strongly on the in-cylinder gas temperature, which is proportional to the gas temperature at IVC. Furthermore, ignition delay is significantly affected by how much oxygen is present, which is also partly determined by the residual gas fraction. Therefore, it is of extreme importance to determine residual gas concentrations accurately.
Technical Paper

Heat Transfer Measurements in a Motored Engine

1989-02-01
890319
A set of experiments has been performed on a motored four stroke engine measuring the gas phase thermal boundary layer profile adjacent to the cylinder head using speckle interferometry. Speckle interferometry is an optical technique which allows full field, line of sight averaged optical phase shift measurements. These optical phase shift measurements may be interpreted as local temperature values for planar or axisymmetric geometries with ideal gases. For this set of experiments, a small (20 mm diameter) portion of the cylinder head was raised 2 mm above the rest of the surface and used as a test surface. The experiments were performed at two engine speeds, 300 and 750 RPM and at low and high intake swirl levels. Interferograms were obtained at 10 crank angle degree intervals from 70° before top dead center of compression to 60° after top dead center of compression.
Technical Paper

Intake Valve Flow Measurements Using PIV

1993-10-01
932700
Intake valve flow patterns have been measured quantitatively using particle image velocimetry (PIV) for a commercial 4-valve diesel cylinder head and valve system. The measurements have been made for low (600 engine RPM) and higher (1000 engine RPM) speeds, and at several planes in the valve curtain area. The measurements involve double exposure photography of laser light scattered by seed particles (≅1 μm) from a laser light sheet (≅ 0.5 mm by 50 mm) through an imaging system onto silver halide film. Subsequent processing produces the local particle displacement between the two exposures. Combined with the known time interval between exposures, the displacement information can produce velocity vectors at many locations in the field of view. The results of the experiments are shown as vector plots for each operating condition. In the plane of the illuminating laser sheet, velocity vectors representing local gas velocity are produced.
Technical Paper

Modeling Diesel Engine Spray Vaporization and Combustion

1992-02-01
920579
Diesel engine in-cylinder combustion processes have been studied using computational models with particular attention to spray development, vaporization, fuel/air mixture formation and combustion. A thermodynamic zero-dimensional cycle analysis program was used to determine initial conditions for the multidimensional calculations. A modified version of the time-dependent, three-dimensional computational fluid dynamics code KIVA-II was used for the computations, with a detailed treatment for the spray calculations and a simplified model for combustion. The calculations were used to obtain an understanding of the potential predictive capabilities of the models. It was found that there is a strong sensitivity of the results to numerical grid resolution. With proper grid resolution, the calculations were found to reproduce experimental data for non- vaporizing and vaporizing sprays. However, for vaporizing sprays with combustion, extremely fine grids are needed.
Technical Paper

Processing and Characterization of Solid and Microcellular PHBV/Coir Fiber Composites

2010-04-12
2010-01-0422
Poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV)/coir fiber composites were prepared via both conventional and microcellular injection-molding processes. The surface of the hydrophilic coir fiber was modified by alkali and silane-treatment to improve its adhesion with PHBV. The morphology, thermal, and mechanical properties were investigated. The addition of coir fiber (treated and untreated) reduced cell size and increased cell density. Further decrease in cell size and increase in cell density were observed for treated fibers compared with PHBV/untreated fiber composites. Mechanical properties such as specific toughness and strain-at-break improved for both solid and microcellular specimens with the addition of coir fibers (both treated and untreated); however, the specific modulus remained essentially the same statistically while the specific strength decreased slightly.
Technical Paper

High Resolution In-Cylinder Scalar Field Measurements during the Compression and Expansion Strokes

2013-04-08
2013-01-0567
High-resolution planar laser-induced fluorescence (PLIF) measurements were performed on the scalar field in an optical engine. The measurements were of sufficient resolution to fully resolve all of the length scales of the flow field through the full cycle. The scalar dissipation spectrum was calculated, and by fitting the results to a model turbulent spectrum the Batchelor scale of the turbulent flow was estimated. The scalar inhomogeneity was introduced by a low-momentum gas jet injection. A consistent trend was observed in all data; the Batchelor scale showed a minimum value at top dead center (TDC) and was nearly symmetric about TDC. Increasing the engine speed resulted in a decrease of the Batchelor scale, and the presence of a shroud on the intake valve, which increased the turbulence intensity, also reduced the Batchelor scale. The effect of the shrouded valve was less significant compared to the effect of engine speed.
Technical Paper

Effects of EGR Components Along with Temperature and Equivalence Ratio on the Combustion of n-Heptane Fuel

2008-04-14
2008-01-0951
Fundamental simulations in a quiescent cell under adiabatic conditions were made to understand the effect of temperature, equivalence ratio and the components of the recirculated exhaust gas, viz., CO2 and H2O, on the combustion of n-Heptane. Simulations were made in single phase in which evaporated n-Heptane was uniformly distributed in the domain. Computations were made for two different temperatures and four different EGR levels. CO2 or H2O or N2was used as EGR. It was found that the initiation of the main combustion process was primarily determined by two competing factors, i.e., the amount of initial OH concentration in the domain and the specific heat of the mixture. Further, initial OH concentration can be controlled by the manipulating the ambient temperature in the domain, and the specific heat capacity of the mixture via the mixture composition. In addition to these, the pre combustion and the subsequent post combustion can also be controlled via the equivalence ratio.
Technical Paper

Reduced Magnet Designs and Position Self-Sensing Control Methods of Flux-Intensifying Permanent Magnet Synchronous Machines

2012-04-16
2012-01-0345
This paper presents advanced and cost-reducing technologies of a motor drive system with reduced permanent magnets but without a position sensor. The key enabler is the integration of novel designs of flux-intensifying interior permanent magnet synchronous machines (FI-IPMSMs) and position self-sensing control technologies. In this paper, we focus on two advantages of FI-IPMSM over conventional flux-weakening interior permanent magnet synchronous machines (FW-IPMSMs). The first benefit is that thinner magnets are possible and there is less concern for demagnetization because of its significantly smaller flux-weakening current. This paper presents two design examples of FI-IPMSMs, one of which has not only smaller magnets but also similar power conversion capability. The second advantage is reduced saturation and cross-saturation effect, which leads to improved position self-sensing capability.
Technical Paper

In-Cylinder Mixing Rate Measurements and CFD Analyses

1999-03-01
1999-01-1110
Gas-phase in-cylinder mixing was examined by two different methods. The first method for observing mixing involved planar Mie scattering measurements of the instantaneous number density of silicon oil droplets which were introduced to the in-cylinder flow. The local value of the number density was assumed to be representative of the local gas concentration. Because the objective was to observe the rate in which gas concentration gradients change, to provide gradients in number density, droplets were admitted into the engine through only one of the two intake ports. Air only flowed through the other port. Three different techniques were used in analyzing the droplet images to determine the spatially dependent particle number density. Direct counting, a filtering technique, and autocorrelation were used and compared. Further, numerical experiments were performed with the autocorrelation method to check its effectiveness for determination of particle number density.
Technical Paper

Characteristics of Air Flow Surrounding Non-Evaporating Transient Diesel Sprays

2000-10-16
2000-01-2789
Airflow characteristics surrounding non-evaporating transient diesel sprays were investigated using a 6-hole injector. Particle Image Velocimetry (PIV) was used to measure the gas velocities surrounding a spray plume as a function of space and time. A hydraulically actuated, electronically controlled unit injector (HEUI) system was used to supply the fuel into a pressurized constant volume chamber at room temperature. The chamber gas densities in this study were 10 kg/m3, 20 kg/m3 and 30 kg/m3. The injection pressure was 96.5 MPa. Two frequency doubled (532 nm) Nd:YAG lasers were used to create coincident laser sheets to illuminate the test section at two instances after start of injection (ASI). The double exposed images of sprays and Al2O3 seed particles were developed and velocity vectors of the gas surrounding the transient diesel sprays were obtained using a numerical autocorrelation PIV method.
Technical Paper

Development and Experimental Study of a New Diesel Exhaust Particulate Trap System*

2000-10-16
2000-01-2846
Diesel exhaust particulate trap system is one of the most effective means to control diesel particulate emissions from diesel vehicles. In this paper, a recently developed diesel exhaust particulate trap system was described and experimentally studied. This system employed a wall-flow ceramic foam filter, which was made of silicon carbide or chromium oxide. And this system was equipped with a microwave heater for the purpose of filter regeneration. Engine dynamometer testing, vehicle bench testing and on-road evaluation of this system were conducted. The experiments studied on the filtration efficiency of this system, the effectiveness of filter regeneration, the power penalty of the vehicle, the ability of noise suppression of this system, and the durability of this particulate trap system. The experimental results showed that this diesel particulate trap system was effective, reliable, and durable.
Technical Paper

Effects of Oxygen Enhancement on the Emissions from a DI Diesel via Manipulation of Fuels and Combustion Chamber Gas Composition

2000-03-06
2000-01-0512
Oxygen enhancement in a direct injection (DI) diesel engine was studied to investigate the potential for particulate matter and NOx emissions control. The local oxygen concentration within the fuel plume was modified by oxygen enrichment of the intake air and by oxygenating the base fuel with 20% methyl t-butyl ether (MTBE). The study collected overall engine performance and engine-out emissions data as well as in-cylinder two-color measurements at 25% and 75% loads over a range of injection timings. The study found oxygen enhancement, whether it be from intake air enrichment or via oxygenated fuels, reduces particulate matter, the effectiveness depending on the local concentration of oxygen in the fuel plume. Since NOx emissions depend strongly on the temperature and oxygen concentration throughout the bulk cylinder gas, the global thermal and dilution effects from oxygen enrichment were greater than that from operation on oxygenated fuel.
Technical Paper

Ultrasonic Cavitation Based Casting of Aluminum Matrix Nanocomposites for Automobile Structures

2006-04-03
2006-01-0290
The properties of aluminum alloys reinforced by ceramic nanoparticles (less than 100nm) would be enhanced considerably while the ductility is retained over that of the native alloy. The potential of bulk Al-based metal matrix nano-composites (Al MMNCs) cannot be fully developed for industrial applications unless complex structural Al MMNC components can be fabricated cost effectively, such as by casting. Reliable bulk Al MMNCs cannot be cast unless the nanoparticles can be dispersed and distributed uniformly in molten Al alloys. This paper investigates a high volume production method for high performance aluminum matrix nanocomposites, in particular, the application of high intensity ultrasonic cavitation in mixing and dispersing nano-sized ceramic particles in Al melts to cast bulk Al MMNCs for complex automobile structures. Nano-sized SiC particles have been dispersed in molten aluminum alloy A356 for casting.
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