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Technical Paper

Comparing the Operation of an HSDI Engine Using Multiple Injection Schemes with Soybean Biodiesel, Diesel and Their Blends

2009-04-20
2009-01-0719
The KIVA-3V code, developed by Los Alamos National Laboratory, with modifications that improve its capability with biodiesel simulations was used to model the operation of an HSDI engine using blends of soybean biodiesel and diesel. Biodiesel and their blends with diesel are frequently used to reduce emissions from diesel engines, although previous studies showed that biodiesel may increase NOx emission. The paradox may be resolved by running the engine in low temperature combustion mode with biodiesel/diesel blends, as low temperature combustion simultaneously reduced NOx and soot. The modified KIVA code predicts the major combustion characteristics: peak combustion pressure, heat release rate and ignition timing accurately when compared with experimental measurements. It also correctly predicts the trend of NOx emissions. It was observed that the cylinder temperature distribution has a strong effect on emission levels.
Technical Paper

Comparing the Operation of a High Speed Direction Injection Engine Using MVCO Injector and Conventional Fuel Injector

2009-04-20
2009-01-0718
The operation of a small bore high speed direct injection (HSDI) engine with a MVCO injector is simulated by the KIVA 3V code, developed by Los Alamos National Laboratory. The MVCO injector extends the range of injection timings over conventional injectors and it extra flexibility in designing injection schemes. Combustion from very early injection is observed with MVCO injections but not with conventional injection. This improves the fuel economy of the engine in terms of lower ISFC. Even better efficiency can be achieved by using biodiesel, which may be due to extra oxygen in the fuel improving the combustion process. Biodiesel sees a longer ignition delay for the initial injection. It also exhibits a faster burning rate and shorter combustion duration. Biodiesel also lowered both NOx and soot emissions. This is consistent with the general observation for soot emissions.
Technical Paper

Macroscopic and Microscopic Characteristics of Flash Boiling Spray with Binary Fuel Mixtures

2019-04-02
2019-01-0274
Flash boiling has drawn much attention recently for its ability to enhance spray atomization and vaporization, while providing better fuel/air mixing for gasoline direct injection engines. However, the behaviors of flash boiling spray with multi-component fuels have not been fully discovered. In this study, isooctane, ethanol and the mixtures of the two with three blend ratios were chosen as the fuels. Measurements were performed with constant fuel temperature while ambient pressures were varied to adjust the superheated degree. Macroscopic and microscopic characteristics of flash boiling spray were investigated using Diffused Back-Illumination (DBI) imaging and Phase Doppler Anemometry (PDA). Comparisons between flash boiling sprays with single component and binary fuel mixtures were performed to study the effect of fuel properties on spray structure as well as atomization and vaporization processes.
Technical Paper

Spray Characteristics of Gasoline-Ethanol Fuel Blends under Flash-Boiling Conditions

2019-04-02
2019-01-0297
The spray structure and vaporization processes of flash-boiling sprays in a constant volume chamber under a wide range of superheated conditions were experimentally investigated by a high speed imaging technique. The Engine Combustion Network’s Spray G injector was used. Four fuels including gasoline, ethanol, and gasoline-ethanol blends E30 and E50 were investigated. Spray penetration length and spray width were correlated to the degree of the superheated degree, which is the ratio of the ambient pressure to saturated vapor pressure (pa/ps). It is found that parameter pa/ps is critical in describing the spray transformation under flash-boiling conditions. Three distinct stages namely the slight flash-boiling, the transition flash-boiling, and the flare flash-boiling are identified to describe the transformation of spray structures.
Technical Paper

High-Load Compression-Ignition Engine Emissions Reduction with Inverted Phi-Sensitivity Fuel Using Multiple Injection Strategies

2019-04-02
2019-01-0554
Inverted phi (ϕ)-sensitivity is a new approach of NOx reduction in compression-ignition (C.I.) engines. Previously, pure ethanol (E100) was selected as the preliminary test fuel in a single injection compression-ignition engine, and was shown to have good potential for low engine-out NOx emissions under low and medium load conditions due to its inverted ignition sequence. Under high load, however, the near-stoichiometric and non-homogeneous fuel/air distribution removes the effectiveness of the inverted ϕ-sensitivity. Therefore, it is desirable to recover the combustion sequence in the chamber such that the leaner region is burned before the near-stoichiometric region. When the combustion in near-stoichiometric region is inhibited, the temperature rise of that region is hindered and the formation of NOx is suppressed.
Technical Paper

Combustion Characteristics in a Constant Volume Chamber of Diesel Blended with HTL

2019-04-02
2019-01-0578
There are a few different ways in which biofuels can be sourced, with the most popular coming from agricultural sources. An alternative approach is to utilize biowaste. An estimated 20 million dry tons of volatile organic compounds, or biowaste, is annually deposited in US municipal wastewaters. Most of this biowaste energy content is not recovered and, as a result, the biowaste could be a massive potential source of renewable energy. Biocrude diesel is converted from wet biowaste via hydrothermal liquefaction (HTL). Three types of feedstocks (algae, swine manure, and food processing waste) were converted into biocrude oil via HTL. From the previous experiments done in an AVL 5402 single-cylinder diesel engine, it was observed that the presence of 20% of HTL in the blend performed similarly during combustion to pure diesel. By studying these mixtures in a constant volume chamber, these observations could be compared to the results in the diesel engine.
Technical Paper

Improving Energy Efficiency in Automotive Vapor Compression Cycles through Advanced Control Design

2006-04-03
2006-01-0267
This paper presents an experimental analysis of the performance of various control strategies applied to automotive air conditioning systems. A comparison of the performance of a thermal expansion valve (TEV) and an electronic expansion valve (EEV) over a vehicle drive cycle is presented. Improved superheat regulation and minor efficiency improvements are shown for the EEV control strategies. The efficiency benefits of continuous versus cycled compressor operation are presented, and a discussion of significant improvements in energy efficiency using compressor control is provided. Dual PID loops are shown to control evaporator outlet pressure while regulating superheat. The introduction of a static decoupler is shown to improve the performance of the dual PID loop controller. These control strategies allow for system capacity control, enabling continuous operation and achieving significant energy efficiency improvements.
Technical Paper

Computational Analysis of Biodiesel Combustion in a Low-Temperature Combustion Engine using Well-Defined Fuel Properties

2007-04-16
2007-01-0617
Biodiesel fuel can be produced from a wide range of source materials that affect the properties of the fuel. The diesel engine has become a highly tuned power source that is sensitive to these properties. The objectives of this research were to measure and predict the key properties of biodiesel produced from a broad range of source materials to be used as inputs for combustion modeling; and second to compare the results of the model with and without the biodiesel fuel definition. Substantial differences in viscosity, surface tension, density and thermal conductivity were obtained relative to reference diesel fuels and among the different source materials. The combustion model revealed differences in the temperature and emissions of biodiesel when compared to reference diesel fuel.
Technical Paper

Comparisons of Computed and Measured Results for a HSDI Diesel Engine Operating Under HCCI Mode

2006-04-03
2006-01-1519
As engine researchers are facing the task of designing more powerful, more fuel efficient and less polluting engines, a large amount of research has been focused towards homogeneous charge compression ignition (HCCI) operation for diesel engines. Ignition timing of HCCI operation is controlled by a number of factors including intake temperatures, exhaust gas recirculation (EGR) and injection timing to name a few. This study focuses on the computational modeling of an optically accessible high-speed direct-injection (HSDI) small bore diesel engine. In order to capture the phenomena of HCCI operation, the KIVA computational code package has been outfitted with an improved and optimized Shell autoignition model, the extended Zeldovich thermal NOx model, and soot formation and oxidation models. With the above named models in place, several cases were computed and compared to experimentally measured data and captured images of the DIATA test engine.
Technical Paper

Comparison of Linear Roll Dynamics Properties for Various Vehicle Configurations

1992-02-01
920053
The ability to categorize, compare and segregate the roll dynamical behavior of various vehicles from one another is a subject of considerable research interest. A number of comparison paradigms have been developed (static stability index, roll couple methods, etc.), but all suffer from lack of robustness: results developed on the basis of a particular comparison metric are often not able to be generalized across vehicle lines and types, etc., or they simply do not segregate vehicles at all. In addition, most models do not describe vehicle dynamics in sufficient detail, and some contain no dynamics at all (e.g., static stability index = t/2h). In the present work, static stability index, a two-degree-of-freedom roll model and a three-degree-of-freedom roll and handling model were used to locate eigenvalues for a sample of 43 vehicles consisting of (1) passenger cars, (2) light trucks, (3) sport/utility vehicles and (4) minivans.
Technical Paper

Combustion and Emissions of Biodiesel and Diesel Fuels in Direct Injection Compression Ignition Engines using Multiple Injection Strategies

2008-04-14
2008-01-1388
Biodiesel fuels and their blends with diesel are often used to reduce emissions from diesel engines. However, biodiesel has been shown to increase the NOx emissions. Operating a compression ignition engine in low-temperature combustion mode as well as using multiple injections can reduce NOx emissions. Experimental data for biodiesel are compared to those for diesel to show the effect of the biodiesel on the peak pressure, temperature, and emissions. Accurate prediction of biodiesel properties, combined with the KIVA 3V code, is used to investigate the combustion of biodiesel. The volume fraction of the cylinder that has temperatures greater than 2200 K is shown to directly affect the production of oxides of nitrogen. Biodiesel is shown to burn faster during the combustion events, though the ignition delay is often longer for biodiesel compared to diesel.
Technical Paper

Injector Nozzle Coking With Oxygenated Diesel

2001-05-07
2001-01-2016
The use of substances other than petroleum based fuels for power sources is not a new concept. Prior to the advent of petroleum fueled vehicles numerous other substances were used to create mobile sources of power. As the world's petroleum supply dwindles, alternative fuel sources are sought after to replace petroleum fuels. Many industries are particularly interested in the development of renewable fuel sources, or biologically derived fuel sources, which includes ethanol. The use of No. 2 diesel as well as many alternative fuels in compression ignition engines result in injector coking. Injector coking can severely limit engine performance by limiting the amount of fuel delivered to the combustion chamber and altering the spray pattern. Injector tip coking is also one of the most sensitive measures of diesel fuel quality [1]. A machine vision system was implemented to quantify injector coking accumulation when a compression ignition engine was fueled with oxydiesel.
Technical Paper

Low Temperature Combustion within a Small Bore High Speed Direct Injection (HSDI) Diesel Engine

2005-04-11
2005-01-0919
Homogeneous Charge Compression Ignition (HCCI) combustion employing single main injection strategies in an optically accessible single cylinder small-bore High-Speed Direct Injection (HSDI) diesel engine equipped with a Bosch common-rail electronic fuel injection system was investigated in this work. In-cylinder pressure was taken to analyze the heat release process for different operating parameters. The whole cycle combustion process was visualized with a high-speed digital camera by imaging natural flame luminosity. The flame images taken from both the bottom of the optical piston and the side window were taken simultaneously using one camera to show three dimensional combustion events within the combustion chamber. The engine was operated under similar Top Dead Center (TDC) conditions to metal engines. Because the optical piston has a realistic geometry, the results presented are close to real metal engine operations.
Technical Paper

Methane Jet Penetration in a Direct-Injection Natural Gas Engine

1998-02-01
980143
A direct-injection natural gas (DING) engine was modified for optical access to allow the use of laser diagnostic techniques to measure species concentrations and temperatures within the cylinder. The injection and mixing processes were examined using planar laser-induced fluorescence (PLIF) of acetone-seeded natural gas to obtain qualitative maps of the fuel/air ratio. Initial acetone PLIF images were acquired in a quiescent combustion chamber with the piston locked in a position corresponding to 90° BTDC. A series of single shot images acquired in 0.1 ms intervals was used to measure the progression of one of the fuel jets across the cylinder. Cylinder pressures as high as 2 MPa were used to match the in-cylinder density during injection in a firing engine. Subsequent images were acquired in a motoring engine at 600 rpm with injections starting at 30, 20, and 15° BTDC in 0.5 crank angle degree increments.
Technical Paper

Estimating the Expected Effectiveness of Enhanced Ground Proximity Warning Systems in Reducing Controlled Flight Into Terrain by Aircraft Operating under Part-135

2000-04-11
2000-01-2105
In order to reduce “Controlled Flight Into Terrain” (CFIT) accidents the FAA proposed, in 1998, the regulation that Enhanced Ground Proximity Warning Systems (EGPWS) should be installed in all turbine powered aircraft with 6 or more seats for passengers, operating under Federal Aviation Regulation Part-135 (commuter and charter operations). We analyzed all Part-135 crashes of this type using NTSB aviation accident data from 1983 to 1998. There were 15 crashes involving CFIT. We asked 26 experienced pilots to examine the brief narratives of the crashes and to estimate the probability that had the aircraft been equipped with EGPWS, the crews would have avoided the crashes. Based on the ratings, the median probability that Part 135 crashes would be avoided using EGPWS was 59%. We describe the nature of the crashes, the human factors involved and the reasons why the enhanced terrain warning is only partly effective.
Technical Paper

Smokeless Combustion within a Small-Bore HSDI Diesel Engine Using a Narrow Angle Injector

2007-04-16
2007-01-0203
Combustion processes employing different injection strategies in a High-Speed Direct Inject (HSDI) diesel engine were investigated using a narrow angle injector (70 degree). Whole-cycle combustion was visualized using a high-speed digital video camera. The liquid spray evolution process was imaged by the Mie-scattering technique. Different injection strategies were employed in this study including early pre-Top Dead Center (TDC) injection, post-TDC injection, multiple injection strategies with an early pre-TDC injection and a late post-TDC injection. Smokeless combustion was obtained under some operating conditions. Compared with the original injection angle (150 degree), some new combustion phenomena were observed for certain injection strategies. For early pre-TDC injection strategies, liquid fuel impingement is observed that results in some newly observed fuel film combustion flame (pool fires) following an HCCI-like weak flame.
Technical Paper

Two-Photon Laser-Induced Fluorescence of Nitric Oxide in a Diesel Engine

2006-04-03
2006-01-1201
In-cylinder concentrations of nitric oxide (NO) in a diesel engine were studied using a laser-induced fluorescence (LIF) technique that employs two-photon excitation. Two-photon NO LIF images were acquired during the expansion and exhaust portions of the engine cycle providing useful NO fluorescence signal levels from 60° after top dead center through the end of the exhaust stroke. The engine was fueled with the oxygenated compound diethylene glycol diethyl ether to minimize soot within the combustion chamber. Results of the two-photon NO LIF technique from the exhaust portion of the cycle were compared with chemiluminescence NO exhaust-gas measurements over a range of engine loads from 1.4 to 16 bar gross indicated mean effective pressure. The overall trend of the two-photon NO LIF signal showed good qualitative agreement with the NO exhaust-gas measurements.
Technical Paper

Atomization Characteristics of Multi-component Bio-fuel Systems under Micro-explosion Conditions

2008-04-14
2008-01-0937
A numerical study of micro-explosion in multi-component droplets is presented. The homogeneous nucleation theory is used in describing the bubble generation process. A modified Rayleigh equation is then used to calculate the bubble growth rate. The breakup criterion is then determined by applying a linear stability analysis on the bubble-droplet system. After the explosion/breakup, the atomization characteristics, including Sauter mean radius and averaged velocity of the secondary droplets, are calculated from conservation equations. Micro-explosion can be enhanced by introducing biodiesel into the fuel blends of ethanol and tetradecane. Micro-explosion is more likely to occur at high ambient pressure. However, increasing the ambient temperature does not have a significant effect on micro-explosion. There exists an optimal composition in the liquid mixture for micro-explosion.
Technical Paper

Spray and Combustion Visualization in an Optical HSDI Diesel Engine Operated in Low-Temperature Combustion Mode with Bio-diesel and Diesel Fuels

2008-04-14
2008-01-1390
An optically accessible single-cylinder high-speed direct-injection (HSDI) Diesel engine equipped with a Bosch common rail injection system was used to study the spray and combustion processes for European low sulfur diesel, bio-diesel, and their blends at different blending ratio. Influences of injection timing and fuel type on liquid fuel evolution and combustion characteristics were investigated under similar loads. The in-cylinder pressure was measured and the heat release rate was calculated. High-speed Mie-scattering technique was employed to visualize the liquid distribution and evolution. High-speed combustion video was also captured for all the studied cases using the same frame rate. NOx emissions were measured in the exhaust pipe. The experimental results indicated that for all of the conditions the heat release rate was dominated by a premixed combustion pattern and the heat release rate peak became smaller with injection timing retardation for all test fuels.
Technical Paper

Dual-Pump Coherent Anti-Stokes Raman Scattering Measurements in a Direct-Injection Natural Gas Engine

1998-02-23
980144
Single-laser-shot measurements of the fuel/air ratio in the cylinder of a motored direct-injection natural gas (DING) engine were obtained using a dual-pump coherent anti-Stokes Raman scattering (CARS) technique capable of simultaneously probing N2 and CH4. The DING engine was modified for optical access and CARS was used to probe the region near the glow plug. Measurements were acquired at eight different probe volume locations with one crank angle degree resolution for injections starting at 30° and 20° BTDC. The CARS data clearly show the arrival of the fuel jet at the probe volume and, from traversing the probe volume, the location of the centerlines of two fuel jets in the vicinity of the glow plug. The CARS measurements also show large fluctuations in fuel concentration on a shot-to-shot basis indicating the presence of large-scale mixing structures within the fuel jets.
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