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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

Development of Micro-Diesel Injector Nozzles via MEMS Technology and Effects on Spray Characteristics

2001-03-05
2001-01-0528
Micro-machined planar orifice nozzles have been developed and used with commercially produced diesel injection systems. Such a system may have the capability to improve the spray characteristics in DI diesel engines. The availability of a MEMS (Micro-Electro-Mechanical-Systems) processing sequence supported the construction of micro-planar orifice nozzles, and micro-systems technology was also employed in our macro-instrumentation. To demonstrate this process, fourteen MEMS nozzles were fabricated with deep X-ray lithography and electroplating technology. The circular orifice diameters were varied from 40 to 260 microns and the number of orifices varied from one to 169. Three plates with non-circular orifices were also fabricated to examine the effect of orifice shape on spray characteristics. These nozzles were then attached to commercial injectors and the associated injection systems were used for the spray experiments.
Technical Paper

Exploring PVD Coatings for Cylinder Liner Applications

2001-03-05
2001-01-0573
A number of wear resistant coatings has been developed using physical vapor deposition(PVD) process. However this coating process has not yet been widely used in the automotive industry. The purpose of this work was to evaluate thin PVD coatings such as diamond like carbon doped with tungsten (W-DLC), molybdenum-disulfide doped with aluminum (MoS2-Al), and chrome nitride (CrN). Some of these coatings were previously found to have low friction, high wear resistance, or both when tested in unlubricated conditions. In the present work, the experiments were conducted using a Cameron-Plint apparatus in lubricated conditions. The ring counterfaces used were Cr-plated and gas-nitrided compression rings. Our data also indicated that some PVD coatings with thicknesses in the same order of magnitude as the surface roughness of the liners did show some improvement in liner wear resistance. The suitability of thin coatings for liner applications needs additional study.
Technical Paper

Characteristics of Vaporizing Continuous Multi-Component Fuel Sprays in a Port Fuel Injection Gasoline Engine

2001-03-05
2001-01-1231
Vaporization models for continuous multi-component liquid sprays and liquid wall films are presented using a continuous thermodynamics formulation. The models were implemented in the KIVA3V-Release 2.0 code. The models are first applied to clarify the characteristics of vaporizing continuous multi-component liquid wall films and liquid drops, and then applied to numerically analyze a practical continuous multi-component fuel - gasoline behavior in a 4-valve port fuel injection (PFI) gasoline engine under warm conditions. Corresponding computations with single-component fuels are also performed and presented for comparison purposes. As compared to the results of its single-component counterpart, the vaporizing continuous multi-component fuel drop displays a larger vaporization rate initially and a smaller vaporization rate as it becomes more and more dominated by heavy species.
Technical Paper

Effects of Alternative Fuels and Intake Port Geometry on HSDI Diesel Engine Performance and Emissions

2001-03-05
2001-01-0647
This research explored methods to reduce regulated emissions in a small-bore, direct-injection diesel engine. Swirl was used to influence mixing of the spray plumes, and alternative fuels were used to study the effects of oxygenated and water microemulsion diesel fuels on emissions. Air/fuel mixing enhancement was achieved in the running engine by blocking off a percentage of one of the two intake ports. The swirl was characterized at steady-state conditions with a flowbench and swirl meter. Swirl ratios of 1.85, 2.70, and 3.29 were studied in the engine tests at full load with engine speeds of 1303, 1757, and 1906 rev/min. Increased swirl was shown to have negative effects on emissions due to plume-to-plume interactions. Blends of No. 2 diesel and biodiesel were used to investigate the presence of oxygen in the fuel and its effects on regulated emissions. Pure No. 2 diesel fuel, a 15% and a 30% biodiesel blend (by weight) were used.
Technical Paper

A Sequential Fluid-Mechanic Chemical-Kinetic Model of Propane HCCI Combustion

2001-03-05
2001-01-1027
We have developed a methodology for predicting combustion and emissions in a Homogeneous Charge Compression Ignition (HCCI) Engine. This methodology combines a detailed fluid mechanics code with a detailed chemical kinetics code. Instead of directly linking the two codes, which would require an extremely long computational time, the methodology consists of first running the fluid mechanics code to obtain temperature profiles as a function of time. These temperature profiles are then used as input to a multi-zone chemical kinetics code. The advantage of this procedure is that a small number of zones (10) is enough to obtain accurate results. This procedure achieves the benefits of linking the fluid mechanics and the chemical kinetics codes with a great reduction in the computational effort, to a level that can be handled with current computers.
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

Potato Tuber Formation and Metabolism in the Spaceflight Environment

1996-07-01
961393
Five potato (Solanum tuberosum L.) leaf cuttings were flown on STS-73 in late October, 1995 as part of the 16-day USML-2 mission. Pre-flight studies were conducted to study tuber growth, determine carbohydrate concentrations and examine the developing starch grains within the tuber. In these tests, tubers attained a fresh weight of 1.4 g tuber-1 after 13 days. Tuber fresh mass was significantly correlated to tuber diameter. Greater than 60% of the tuber dry mass was starch and the starch grains varied in size from 2 to 40 mm in the long axis. For the flight experiment, cuttings were obtained from seven-week-old Norland potato plants, kept at 5°C for 12 hours then planted into arcillite in the ASTROCULTURE™ flight hardware. The flight package was loaded on-board the orbiter 22 hours prior to launch.
Technical Paper

Near Wall Interaction in Spray Impingement

1996-02-01
960863
The hydrodynamic details of droplet-droplet and droplet-liquid film interactions on solid surfaces are believed to have a significant role in spray impingement phenomena, yet details of this interaction have not been clearly identified. The interaction among the droplets during impact affects their residence time on the surface, spreading, and droplet and liquid film stability. After impact, droplet interactions affect droplet collisions, coalescence and liquid splashing, This interaction affects secondary atomization and the droplet dispersion characteristics of the impingement process. In this study, details of droplet-droplet and droplet-liquid film interactions in solid surface impingement have been visualized using high speed photography. The effects of these interactions on secondary atomization and droplet dispersion have been quantified.
Technical Paper

High Pressure Multiple Injection Spray Characteristics

1996-02-01
960860
In previous work, high injection pressures and multiple injections per engine stroke were shown to be effective at reducing the NOx and particulate emissions of DI Diesel engine combustion [1, 2]. A series of experiments were performed to study the effects of injection pressure, back pressure, and injection strategy on the spray characteristics for multiple injections. An injection system which was capable of multiple injections was used to introduce diesel fuel into a constant volume cold spray chamber. Parallel engine experiments were conducted using the same injectors as in this work [1, 2, 3]. In these engine tests, emissions (NOx and particulate) were measured. The engine experiments were used to develop the injector and chamber operating conditions for this work. The injection pressure was varied up to 90 MPa.
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

Experimental and Numerical Studies of High Pressure Multiple Injection Sprays

1996-02-01
960861
Characterization of high pressure diesel sprays has been performed both experimentally and numerically. The experimental study was conducted using a fuel injection system which has a capability of producing multiple injection sprays. The fuel sprays were injected from a multi-hole nozzle into a pressurized cylindrical chamber with optical windows. In order to investigate the effects of a multiple injection strategy on spray characteristics, a double injection spray with the mass evenly distributed between the first and second sprays, and a 1 millisecond dwell between sprays was compared with a single injection spray. Both single and double injection cases had nominally the same injection pressure, injection delivery, and ambient gas density. Transient spray tip penetration lengths and spray angles were obtained from high speed photographic spray images. The spray droplet sizes were derived from the images by using a light extinction method.
Technical Paper

Effects of Mixture Preparation Characteristics on Four-Stroke Utility Engine Emissions and Performance

1996-08-01
961738
A laboratory-based fuel mixture system capable of delivering a range of fuel/air mixtures has been used to observe the effects of differing mixture characteristics on engine combustion through measurement and analysis of incylinder pressure and exhaust emissions. Fuel air mixtures studied can be classified into four different types: 1) Completely homogeneous fuel/air mixtures, where the fuel has been vaporized and mixed with the air prior to entrance into the normal engine induction system, 2) liquid fuel that is atomized and introduced with the air to the normal engine induction system, 3) liquid fuel that is atomized, and partially prevaporized but the air/fuel charge remains stratified up to introduction to the induction system, and 4) the standard fuel metering system. All tests reported here were conducted under wide open throttle conditions. A four-stroke, spark-ignited, single-cylinder, overhead valve-type engine was used for all tests.
Technical Paper

Injection and Ignition Effects on Two-Stroke Direct Injection Emissions and Efficiency

1996-08-01
961803
To help understand the fundamental processes involved in direct injection, a research project was conducted using a single-cylinder, two-stroke research engine at a mid-speed, boat load operating condition. A 24 statistical factorial experimental design was applied. Of the factors tested at this operating condition, spray type was the most important factor affecting hydrocarbon emissions, followed by in-cylinder flow-related factors. Injection spray was also most important for nitrogen oxide emissions, carbon monoxide emissions, and efficiency. The dominant mechanism influencing the results was misfire, with other mechanisms present for specific responses.
Technical Paper

A Comparison of Modified Elevated Temperature HFRR Test Data With Scuffing BOCLE Results

1996-10-01
961946
Evolving diesel engine design trends are expected to include fuel systems operating at significantly higher pressures and temperatures than in the past. Accordingly, meaningful laboratory tests are needed to help guide this development. Two candidate test methods were evaluated in this exploratory study. Scuffing Load Ball-on Cylinder Lubricity Evaluator (BOCLE) and Modified High-Frequency Reciprocating Rig (HFRR) test results covering a range of operating temperatures were compared with fuel property data. Correlations of the Modified HFRR test data with BOCLE results were also made.
Technical Paper

Modeling of NOx Emissions with Comparison to Exhaust Measurements for a Gas Fuel Converted Heavy-Duty Diesel Engine

1996-10-01
961967
In previous work the KIVA-II code has been modified to model modem DI diesel engines and their emissions of particulate soot and oxides of nitrogen (NOx). This work presents results from a program to further validate the NOx emissions models against engine experiments with a well characterized modern engine. To facilitate a simplified comparison with experiments, a single cylinder research version of the Caterpillar 3406 heavy duty DI diesel engine was retrofitted to run as a naturally-aspirated, propane-fueled, spark-ignited engine. The retrofit includes installing a low compression ratio piston with bowl, adding a gas mixer, replacing the fuel injector assembly with a spark plug assembly and adding spark and fuel stoichiometry control hardware. Cylinder pressure and engine-out NOx emissions were measured for a range of speeds, exhaust gas residual (EGR) fractions, and spark timing settings.
Technical Paper

Mixture Preparation Effects on Ignition and Combustion in a Direct-Injection Spark-Ignition Engine

1996-10-01
962013
Planar instantaneous fuel concentration measurements were made by laser-induced fluorescence of 3-pentanone in the spark gap just prior to ignition in a direct-injection spark-ignition engine operating at a light load, highly stratified condition. The distribution of the average equivalence ratio in a circle of 1.9 mm diameter centered on the spark plug showed that a large fraction of the cycles had an equivalence ratio below the lean limit, yet acceptable combustion was achieved in those cycles. Further, weak correlation was found between the local average equivalence ratio near the spark plug and the time required to achieved a 100 kPa pressure rise above the motoring pressure, as well as other parameters which characterize the early stages of combustion. The cause for this behavior is assessed to be mixture motion during the spark discharge which continually convects fresh mixture through the spark gap during breakdown.
Technical Paper

Temperature Effects on Fuel Sprays from a Multi-Hole Nozzle Injector

1996-10-01
962005
A study of fuel spray characteristics for diesel fuel from a multi-hole nozzle injector was performed yielding tip penetration length and spray cone angle for each of the spray plumes from a six hole injector. The main feature of the system used was that analysis of all the fuel plumes could occur at one time, as all the plumes were imaged on the same piece of film. Spray behavior was examined for two injection pressures (72 MPa and 122 MPa) and for ambient temperatures up to 523 K (250°C). The results in this paper show how the spray plumes behave as they leave each of the six holes of the injector. The characteristics of each hole differs during injection. The variations of spray cone angle and tip penetration length between holes are small, but significant. These variations in tip penetration and cone angle changed as the temperature of the chamber changed, but the overall characteristics of the spray plumes changed only slightly for the temperatures used in this paper.
Technical Paper

Effect of Injector Nozzle Hole Size and Number on Spray Characteristics and the Performance of a Heavy Duty D.I. Diesel Engine

1996-10-01
962002
An engine emissions and performance study was conducted in conjunction with a series of experiments using a constant volume cold spray chamber. The purpose of the study was to explore the effects of number of holes and hole size on the emissions and performance of a direct injection heavy duty diesel engine. The spray experiments provide insight into the spray parameters and their role in the engine's combustion processes. The fuel system used for both the engine and spray chamber experiments was an electronically controlled, common rail injector. The injector nozzle hole size and number combinations used in the experiments included 225X8 (225 gm diameter holes with 8 holes in the nozzle), 260X6, 260X8, and 30OX6. The engine tests were conducted on an instrumented single cylinder version of the Caterpillar 3400 series heavy duty diesel engine. Data were taken with the engine running at 1600 RPM, 75% load.
Technical Paper

Effects of Injection Timing on Air-Fuel Mixing in a Direct-Injection Spark-Ignition Engine

1997-02-24
970625
Multidimensional modeling is used to study air-fuel mixing in a direct-injection spark-ignition engine. Emphasis is placed on the effects of the start of fuel injection on gas/spray interactions, wall wetting, fuel vaporization rate and air-fuel ratio distributions in this paper. It was found that the in-cylinder gas/spray interactions vary with fuel injection timing which directly impacts spray characteristics such as tip penetration and spray/wall impingement and air-fuel mixing. It was also found that, compared with a non-spray case, the mixture temperature at the end of the compression stroke decreases substantially in spray cases due to in-cylinder fuel vaporization. The computed trapped-mass and total heat-gain from the cylinder walls during the induction and compression processes were also shown to be increased in spray cases.
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