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Viewing 1 to 30 of 39
2011-08-30
Technical Paper
2011-01-1765
Haifeng Liu, Peng Zhang, Zheming Li, Zunqing Zheng, Mingfa Yao, Xuan Feng
The influence of different combustion chamber configuration, intake temperature, and coolant temperature on HCCI combustion processes were investigated in a single-cylinder optical engine. Two-dimensional images of the chemiluminescence were captured using an intensified CCD camera in order to understand the spatial distribution of the combustion. N-heptane was used as the test fuel. Three combustion chamber geometries with different squish lip, salient, orthogonal, reentrant shape, referred as V-type, H-type, and A-type respectively, were used in this study. Intake temperature was set to 65°C and 95°C, while coolant temperature was set to 85°C. The experimental data consisting of the in-cylinder pressure, heat release rate, chemiluminescence images all indicated that the different combustion chamber geometries result in different turbulence intensity in the combustion chamber, and thus affect the auto-ignition timing, chemiluminescence intensity, and combustion processes.
2011-08-30
Technical Paper
2011-01-1931
Haifeng Liu, Mingfa Yao, Ming Huo, Chia-fon F. Lee
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.
2006-04-03
Technical Paper
2006-01-0267
Michael Keir, Bryan Rasmussen, Andrew Alleyne
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.
1992-02-01
Technical Paper
920513
T.K. Hayes, R.A. White, J.E. Peters
Combustion chamber deposits in spark ignition engines act as thermal insulators and can lead to octane requirement increase. The thermal properties of deposits are not well documented, the reported thermal diffusivity values vary by two orders of magnitude. Two thermal property measurement techniques were compared, the flash and steady illumination laser methods. The steady laser method was more suitable for deposit property measurement. A comparison was made of the thermal properties of deposits grown with a base fuel with the thermal properties of deposits grown with the base fuel doped with reformer bottoms. For the clean fuel the thermal diffusivity ranged from 3.5 to 3.9-7 m2/s, at various locations around the combustion chamber. For the fuel doped with reformer bottoms the thermal diffusivity ranged from 1.1 to 1.9-7 m2/s at different locations within the combustion chamber.
1993-03-01
Technical Paper
930217
T. K. Hayes, R.A. White, J. E. Peters
Cylinder head combustion chamber and piston temperatures and heat fluxes were measured in a 2.2 L 4 cylinder spark ignition engine. Measurements for the combustion chamber were made at wide open throttle conditions, 1400 rpm to 5000 rpm at 600 rpm increments, additional measurements were made on the combustion chamber at part throttle conditions at 3200 RPM. Piston temperature and heat flux measurements were made at WOT conditions from 1400 to 3200 RPM in 600 RPM increments. Average combustion chamber surface temperatures ranged from 130 deg. C to 248 deg. C, while peak combustion chamber surface temperatures ranged from 142 deg. C to 258 deg. C for WOT conditions. Peak heat flus at the surface for WOT conditions in the combustion chamber ranged from 1.2 MW/m2to 5.0 MW/m2. Central region heat fluxes were 2.3 to 2.8 times greater than those in the end gas regions of the combustion chamber.
1993-04-01
Technical Paper
931181
Panos Tamamidis, Dennis N. Assanis
The finite volume, three-dimensional, turbulent flow code ARIS-3D is applied to the study of the complex flow field through the inlet port and within the cylinder of a uniflow-scavenged engine. The multiblock domain decomposition technique is used to accommodate this complex geometry. In this technique, the domain is decomposed into two blocks, one block being the cylinder and the other being the inlet duct. The effects of inlet duct length, geometric port swirl angle, and number of ports on swirl generating capability are explored. Trade-offs between swirl level and inherent pressure drop can thus be identified, and inlet port design can be optimized.
1993-04-01
Technical Paper
931180
Evangelos Karvounis, Dennis N. Assanis
A novel framework for intelligent design of engine systems is introduced. Existing models of engine components and processes are integrated into a multi-purpose, flexible configuration framework. Fundamental thermodynamic elements, including zero-dimensional control volumes, one-dimensional pulsating fluid lines, and continuous flow machines are identified as the constituting components of engine systems. Models of the behavior of these elements, with various degrees of thermodynamic resolution, have been implemented into the framework. The task of the engine designer is, thus, reduced into selecting appropriate thermodynamic elements to model his engine system based on his design objectives. The applicability of the present framework to a wide range of simulation problems is demonstrated.
1997-10-01
Technical Paper
972945
P. L. Kelly-Zion, J. P. Styron, C.-F. Lee, R. P. Lucht, J. E. Peters, R. A. White
The presence and distribution of liquid fuel within an engine cylinder at cold start may adversely affect the hydrocarbon emissions from port-injected, spark ignition engines. Therefore, high speed videos of the liquid fuel entry into the cylinder of an optical engine were recorded in order to assess the effect of various engine operating parameters on the amount of liquid fuel inducted into the cylinder, the sizes of liquid drops present and the distribution of the fuel within the cylinder. A 2.5L, V-6, port-injected, spark ignition engine was modified so that optical access is available throughout the entire volume of one of the cylinders. A fused silica cylinder is sandwiched between the separated block and head of the engine and a “Bowditch-type” piston extension is mounted to the production piston. The Bowditch piston has a fused silica crown so that visualization is possible through the top of the piston as well as through the transparent cylinder.
1998-02-01
Technical Paper
980143
P. J. Rubas, M. A. Paul, G. C. Martin, R. E. Coverdill, R. P. Lucht, J. E. Peters, K. A. DelVecchio
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.
1998-02-23
Technical Paper
980144
R. E. Foglesong, P. J. Rubas, S. M. Green, R. P. Lucht, J. E. Peters
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.
1998-02-23
Technical Paper
981034
Terrence R. Meyer, Robert A. White
A geometrically accurate, three-dimensional finite element model of a Diesel engine exhaust valve and cylinder head assembly has been developed to analyze the effect of cylinder head interactions on exhaust valve stresses. Results indicate that a multi-lobed stress pattern occurs around the exhaust valve head due to cylinder head deformation, stiffness variations, and thermal asymmetry. Consequently, peak valve bending and hoop stresses from the three-dimensional model are 48% and 40% higher, respectively, than for the two-dimensional, axisymmetric model. These results indicate the degree of model complexity required for more accurate analyses of exhaust valve operating stresses.
1998-02-23
Technical Paper
981029
Mark D. Anderson, Tsu-Chin Tsao, Michael B. Levin
Camless actuation offers programmable flexibility in controlling engine valve events. However, a full range of engine benefits will only be available, if the actuation system can control lift profile characteristics within a particular lift event. Control of the peak value of valve lift is a first step in controlling the profile. The paper presents an adaptive feedback control of valve lift for a springless electrohydraulic valvetrain. The adaptive control maintains peak value of lift in presence of variations in engine speed, hydraulic fluid temperature and manufacturing variability of valve assemblies. The control design includes a reduced-order model of the system dynamics. Experimental results show dynamic behavior under various operating and environmental conditions and demonstrate advantages of adaptive control over the non-adaptive type.
1997-02-24
Technical Paper
970248
Dean H. Kim, Mark D. Anderson, Tsu-Chin Tsao, Michael B. Levin
A dynamic model for the springless electrohydraulic valvetrain has been developed. The model speeds up the valvetrain development process by simulating effects of parameter changes, thus minimizing the number of hardware variations. It includes dynamic characteristics of check valves that enable energy recovery, hydraulic snubbers that limit seating velocity of the engine valves, and leakage in the control solenoids. A good match of the experimental data has been obtained for a single valve system, and the model calibration and validation have been completed. The known parameters are used together with some unknown calibration constants which have been tuned to match the experimental data. The simulation results for a twin valve system are also presented. The model applications for system performance analysis and for the closed-loop control of the engine valve lift are described. The cyclic variability of the experimental data is also discussed.
2006-04-03
Technical Paper
2006-01-1201
Glen C. Martin, Charles J. Mueller, Chia-fon F. Lee
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.
2007-04-16
Technical Paper
2007-01-0203
Tiegang Fang, Robert E. Coverdill, Chia-fon F. Lee, Robert A. White
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.
2007-04-16
Technical Paper
2007-01-0617
Jonathon P. McCrady, Valerie L. Stringer, Alan C. Hansen, Chia-fon F. Lee
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.
2007-04-16
Technical Paper
2007-01-0648
Joshua W. Powell, Chia-fon F. Lee
Laser diagnostics of fuel sprays are often hampered by multiple scattering effects. Planar laser-induced exciplex fluorescence (PLIEF) and Mie scattering images of a spray are presented, and the effects of multiple signal scattering are explored. A hollow-cone spray is cut in half with a spray cutter, and then imaged from either side. In one set, signal passes through the spray to the camera (back-cut images), and in the other set it does not (front-cut images), showing the effect of passing the signal through the spray to the camera. The cut spray is characterized with a phase Doppler anemometer (PDA) and Sauter Mean Diameter (SMD) is seen to range from 10-30 μm. Operational guidelines for using the cutter are presented. It was determined that a film forms on the cutter face 3-5 ms after the start of injection (ASOI) depending on the cutter temperature.
2004-06-08
Technical Paper
2004-01-1843
Charles J. Mueller, Glen C. Martin, Thomas E. Briggs, Kevin P. Duffy
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.
2005-04-11
Technical Paper
2005-01-0919
Tiegang Fang, Robert E. Coverdill, Chia-fon F. Lee, Robert A. White
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.
2005-04-11
Technical Paper
2005-01-0209
Dongyao Wang, Chia-fon F. Lee
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.
2008-04-14
Technical Paper
2008-01-0937
Chia-fon F. Lee, Kuo-Ting Wang, Way Lee Cheng
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.
2008-04-14
Technical Paper
2008-01-0386
Thomas L. McKinley, Andrew G. Alleyne
This paper describes a ‘toolbox’ for modeling liquid cooling system networks within vehicle thermal management systems. Components which can be represented include pumps, coolant lines, control valves, heat sources and heat sinks, liquid-to-air and liquid-to-refrigerant heat exchangers, and expansion tanks. Network definition is accomplished through a graphical user interface, allowing system architecture to be easily modified. The elements of the toolbox are physically based, so that the models can be applied before hardware is procured. The component library was coded directly into MATLAB / SIMULINK and is intended for control system development, hardware-in-the-loop (HIL) simulation, and as a system emulator for on-board diagnostics and controls purposes. For HIL simulation and on-board diagnostics and controls, it is imperative that the model run in real-time.
2008-04-14
Technical Paper
2008-01-1390
Tiegang Fang, Yuan-chung Lin, Tien Mun Foong, Chia-fon F. Lee
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.
2008-04-14
Technical Paper
2008-01-1388
Valerie L. Stringer, Way Lee Cheng, Chia-fon F. Lee, Alan C. Hansen
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.
2006-04-03
Technical Paper
2006-01-0649
Jia X. Zhao, Chia-fon F. Lee
The blow-by phenomenon is seldom acquainted with diesel engines, but for a small bore HSDI optical diesel engine, the effects are significant. A difference in peak pressure up to 25% can be observed near top-dead-center. To account for the pressure differences, a 0-D crevice flow model with a dynamic ring pack model was incorporated into the KIVA code to determine the amount of blow-by. The ring pack model will take into account the forces acting on the piston rings, the position of the piston rings, and the pressure located at each region of the crevice volume at every time step. The crevice flow model takes into consideration the flow through the circumferential gap, ring gap, and the ring side clearance. As a result, the cylinder mass, trapped mass in the crevice regions, and the blow-by values are known. Validation of the crevice model is accomplished by comparing the in-cylinder motoring pressure trace with the experimental motoring data.
2006-04-03
Technical Paper
2006-01-1519
Robert C. Wang, Tiegang Fang, Chia-fon F. Lee
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.
2009-04-20
Technical Paper
2009-01-0719
Valerie L. Stringer, Way Lee Cheng, Chia-Fon F. Lee, Alan C. Hansen
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.
2009-04-20
Technical Paper
2009-01-1528
Deyang Hou, Houshun Zhang, Yury Kalish, Chia-fon F. Lee, Way Lee Cheng
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.
2017-03-28
Technical Paper
2017-01-0572
Mianzhi Wang, Suya Gao, Chia-Fon Lee
Abstract In this work, an efficient and unified combustion model is introduced to simulate the flame propagation, diffusion-controlled combustion, and chemically-driven ignition in both SI and CI engine operation. The unified model is constructed upon a G-equation model which addresses the premixed flame propagation. The concept of the Livengood-Wu integral is used with tabulated ignition delay data to account for the chemical kinetics which is responsible for the spontaneous ignition of fuel-air mixture. A set of rigorously defined operations are used to couple the evolution of the G scalar field and the Livengood-Wu integral. The diffusion-controlled combustion is simulated equivalent to applying the Burke-Schumann limit. The combined model is tested in the simulation of the premixed SI combustion in a constant volume chamber, as well as the CI combustion in a conventional small bore diesel engine.
2017-10-08
Technical Paper
2017-01-2321
Timothy H. Lee, Han Wu, Alan Hansen, Tonghun Lee, Gang Li
Abstract Bio-butanol has been considered as a promising alternative fuel for internal combustion engines due to its advantageous physicochemical properties. However, the further development of bio-butanol is inhibited by its high recovery cost and low production efficiency. Hence, the goal of this study is to evaluate two upstream products from different fermentation processes of bio-butanol, namely acetone-butanol-ethanol (ABE) and isopropanol-butanol-ethanol (IBE), as alternative fuels for diesel. The experimental comparison is conducted on a single-cylinder and common-rail diesel engine under various main injection timings (MIT) and equivalent engine load (EEL) conditions. The experimental results show that ABE and IBE significantly affect the combustion phasing. The start of combustion (SOC) is retarded when ABE and IBE are mixed with diesel. Furthermore, the ABE/IBE-diesel blends are more sensitive to the changes in MIT compared with that of pure diesel.
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