Refine Your Search

Topic

Search Results

Technical Paper

Study of Biodiesel Combustion in a Constant Volume Chamber with Different Ambient Temperature and Oxygen Concentration

2011-08-30
2011-01-1931
Biodiesel is a widely used biofuel in diesel engines, which is of particular interest as a renewable fuel because it possesses the similar properties as the diesel fuel. The pure soybean biodiesel was tested in an optical constant volume combustion chamber using natural flame luminosity and forward illumination light extinction (FILE) methods to explore the combustion process and soot distribution at various ambient temperatures (800 K and 1000 K) and oxygen concentrations (21%, 16%, 10.5%). Results indicated that, with a lower ambient temperature, the autoignition delay became longer for all three oxygen concentrations and more ambient air was entrained by spray jet and more fuel was burnt by premixed combustion. With less ambient oxygen concentration, the heat release rate showed not only a longer ignition delay but also longer combustion duration.
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

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

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

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

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

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

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

Adaptive PCCI Combustion Using Micro-Variable Circular-Orifice (MVCO) Fuel Injector – Key Enabling Technologies for High Efficiency Clean Diesel Engines

2009-04-20
2009-01-1528
This paper presents the latest results for a new high efficiency clean diesel combustion system – Adaptive PCCI Combustion (a premixed charge compression ignition mixed-mode combustion) using a micro-variable circular orifice (MVCO) fuel injector. Key characteristics of the new combustion system such as low NOx and soot emissions, high fuel efficiency, increased engine torque are presented through KIVA simulation results. While early premixed charge compression ignition (PCCI) combustion reduces engine-out NOx and soot, it's limited to partial loads by known issues such as combustion control, high HC and CO, and high pressure rise rate, etc. Conventional combustion is well controlled diffusion combustion but comes with high NOx and soot. Leveraging the key merits of PCCI and conventional combustion in a practical engine is both meaningful and challenging.
Technical Paper

Continuous Multicomponent Fuel Film Vaporization Model for Multidimensional Engine Modeling

2005-04-11
2005-01-0209
A multicomponent fuel film vaporization model using continuous thermodynamics is developed for multidimensional spray and wall film modeling. The vaporization rate is evaluated using the turbulent boundary-layer assumption and a quasi-steady approximation. Third-order polynomials are used to model the fuel composition profiles and the temperature within the liquid phase in order to predict accurate surface properties that are important for evaluating the mass and moment vaporization rates and heat flux. By this approach, the governing equations for the film are reduced to a set of ordinary differential equations and thus offer a significant reduction in computational cost while maintaining adequate accuracy compared to solving the governing equations for the film directly.
Technical Paper

An Experimental Investigation of In-Cylinder Processes Under Dual-Injection Conditions in a DI Diesel Engine

2004-06-08
2004-01-1843
Fuel-injection schedules that use two injection events per cycle (“dual-injection” approaches) have the potential to simultaneously attenuate engine-out soot and NOx emissions. The extent to which these benefits are due to enhanced mixing, low-temperature combustion modes, altered combustion phasing, or other factors is not fully understood. A traditional single-injection, an early-injection-only, and two dual-injection cases are studied using a suite of imaging diagnostics including spray visualization, natural luminosity imaging, and planar laser-induced fluorescence (PLIF) imaging of nitric oxide (NO). These data, coupled with heat-release and efficiency analyses, are used to enhance understanding of the in-cylinder processes that lead to the observed emissions reductions.
Technical Paper

Effects of Oxygenated Compounds on Combustion and Soot Evolution in a DI Diesel Engine:Broadband Natural Luminosity Imaging

2002-05-06
2002-01-1631
The detailed mechanisms by which oxygenated diesel fuels reduce engine-out soot emissions are not well understood. The literature contains conflicting results as to whether a fuel's overall oxygen content is the only important parameter in determining its soot-reduction potential, or if oxygenate molecular structure or other variables also play significant roles. To begin to resolve this controversy, experiments were conducted at a 1200-rpm, moderate-load operating condition using a modern-technology, 4-stroke, heavy-duty DI diesel engine with optical access. Images of broadband natural luminosity (i.e., light emission without spectral filtering) from the combustion chamber, coupled with heat-release and efficiency analyses, are presented for three test-fuels. One test-fuel (denoted GE80) was oxygenated with tri-propylene glycol methyl ether; the second (denoted BM88) was oxygenated with di-butyl maleate. The overall oxygen contents of these two fuels were matched at 26% by weight.
Technical Paper

Using R744 (CO2) to Cool an Up-Armored M1114 HMMWV

2005-05-10
2005-01-2024
The US Army uses a light tactical High-Mobility Multi-Purpose Wheeled Vehicle (HMMWV) which, due to the amount of armor added, requires air conditioning to keep its occupants comfortable. The current system uses R134a in a dual evaporator, remote-mounted condenser, engine-driven compressor system. This vehicle has been adapted to use an environmentally friendly refrigerant (carbon dioxide) to provide performance, efficiency, comfort and logistical benefits to the Army. The unusual thermal heat management issues and the fact that the vehicle is required to operate under extreme ambient conditions have made the project extremely challenging. This paper is a continuation of work presented at the SAE Alternate Refrigerants Symposium held in Phoenix last June [1].
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

Analytical Descriptions of Service Loading Suitable for Fatigue Analysis

1997-04-08
971535
Service loading histories have the same general character for an individual route and the magnitudes vary from driver to driver. Both the magnitude and character of the loading history change from route to route and a linear scaling of one loading history does not characterize the variability of usage over a wide range of operating conditions. In this paper a technique for measuring and extrapolating cumulative exceedance diagrams to quantify the distribution of service loading in a vehicle is described. Monte Carlo simulations are coupled with the local stress strain approach for fatigue to obtain distributions of service loading. Fatigue life estimates based on the original loading histories are compared to those obtained from statistical descriptions of exceedance diagrams.
Technical Paper

Effect of Propene on the Remediation of NOx from Engine Exhausts

1999-10-25
1999-01-3683
Plasma treatment of diesel exhausts has been investigated in recent years due to its potential for remediating NOx in emissions. Hydrocarbons in the exhausts have been found to play an important role in the reaction chemistry during remediation. In this paper, we report on a computational study of the plasma treatment of simulated exhausts containing propene to investigate the effects of hydrocarbons on the conversion pathways for NOx.
Technical Paper

Methods for Detection of Lubrication Failure Applied to a Swashplate Compressor

2000-03-06
2000-01-0974
Understanding lubrication failures at the shoe/swashplate contact of automotive swashplate compressors will greatly enhance the reliability of the air conditioning system. Maintaining proper lubrication is not always possible during transient conditions. Therefore, a method for detection of lubricant loss is of great interest to the automotive industry. Three methods for detecting lubrication loss were examined: contact resistance, acoustic emission, and dynamic pressure oscillations. A mobile air conditioning test stand capable of recording many system parameters was used. Oil return to the compressor was monitored using an oil separator and a refrigerant/oil concentration sensor. Data were taken during steady oil return rates and after oil shut off. The electrical contact resistance between the shoe and swashplate was used to indicate changes in the lubrication conditions at this critical interface. Measurements were taken at two oil return rates during steady oil return tests.
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

Modeling of Spray Vaporization and Air-Fuel Mixing in Gasoline Direct-Injection Engines

2000-03-06
2000-01-0537
A numerical investigation of air-fuel mixing in gasoline direct-injection (GDI) engines is presented in this paper. The primary goal of this study is to demonstrate the importance of fuel representation. In the past studies, fuel has been usually modeled as a single component substance. However, most fuels are mixtures of hydrocarbons with diverse boiling points, resulting in mixture vaporization behavior substantially different from single-component behavior. This study presents a newly developed multicomponent vaporization model, which takes into account important mechanisms such as preferential vaporization, internal circulation, surface regression, and non-ideal behavior in high-pressure environments. A sheet spray atomization model was also used to calculate the disintegration of the liquid sheet and the breakup of the subsequent droplets. The results of a single-component fuel representation and a multicomponent fuel representation were compared.
X