Refine Your Search

Topic

Author

Affiliation

Search Results

Technical Paper

Improved Passage Design for a Spark Plug Mounted Pressure Transducer

2007-04-16
2007-01-0652
Combustion chamber pressure measurement in engines via a passage is an old technique that is still widely used in engine research. This paper presents improved passage designs for an off-set electrode spark plug designed to accept a pressure transducer. The spark plug studied was the Champion model 304-063A. Two acoustic models were developed to compute the resonance characteristics. The new designs have a resonance frequency in a range higher than the fundamental frequency expected from knock so that the signal can be lowpass filtered to remove the resonance and not interfere with pressure signal components associated with combustion phenomena. Engine experiments verified the spark plug resonance behavior. For the baseline engine operating condition approximately 50 of 100 cycles had visible passage resonance in the measured pressure traces, at an average frequency of 8.03 kHz.
Technical Paper

Railplug Ignition Operating Characteristics and Performance:A Review

2007-07-23
2007-01-1832
The basic process of spark ignition in engines has changed little over the more than 100 years since its first application. The rapid evolution of several advanced engine concepts and the refinement of existing engine designs, especially applications of power boost technology, have led to a renewed interest in advanced spark ignition concepts. The increasingly large rates of in-cylinder dilution via EGR and ultra-lean operation, combined with increases in boost pressures are placing new demands on spark ignition systems. The challenge is to achieve strong and consistent ignition of the in-cylinder mixture in every cycle, to meet performance and emissions goals while maintaining or improving the durability of ignitor. The application of railplug ignition to some of these engine systems is seen as a potential alternative to conventional spark ignition systems that may lead to improved ignition performance.
Technical Paper

A Detailed Kinetic Study on the Effect of DTBP on PRF Combustion in HCCI Engines

2007-07-23
2007-01-2002
The effect of Di-tertiary Butyl Peroxide (DTBP) on Primary Reference Fuels (PRFs) in Homogeneous Charge Compression Ignition (HCCI) engines was investigated numerically and was compared with trends from previous experimental observations. A detailed kinetic mechanism for PRF combustion containing more than a thousand species and four thousand reactions was combined with a twenty one species, sixty-nine reaction mechanism for DTBP decomposition. This mechanism predicted the observed experimental trends reasonably well and was used to examine how DTBP addition acts to advance combustion timing and to induce hot ignition for lean and high octane number mixtures. The study suggests that DTBP's predominant mode of action for low Octane Number (ON) fuels is thermal, while for high ON fuels it is chemical. The extended kinetic model compiled for this study and the results obtained can be used to aid in the understanding and development of tailored additives for HCCI engines.
Technical Paper

Effects of Fuel Volatility, Load, and Speed on HC Emissions Due to Piston Wetting

2001-05-07
2001-01-2024
Piston wetting can be isolated from the other sources of HC emissions from DISI engines by operating the engine predominantly on a gaseous fuel and using an injector probe to impact a small amount of liquid fuel on the piston top. This results in a marked increase in HC emissions. In a previous study, we used a variety of pure liquid hydrocarbon fuels to examine the influence of fuel volatility and structure on the HC emissions due to piston wetting. It was shown that the HC emissions correspond to the Leidenfrost effect: fuels with very low boiling points yield high HCs and those with a boiling point near or above the piston temperature produce much lower HCs. All of these prior tests of fuel effects were performed at a single operating condition: the Ford World Wide Mapping Point (WWMP). In the present study, the effects of load and engine speed are examined.
Technical Paper

Particulate Characterization of a DISI Research Engine using a Nephelometer and In-Cylinder Visualization

2001-05-07
2001-01-1976
A nephelometer system was developed to characterize engine particulate emissions from DISI engines. Results were correlated with images showing the location and history of particulates in the cylinder of an optical engine. The nephelometer's operation is based upon the dependence of scattered laser light on particulate size from a flow sampled from the exhaust of an engine. The nephelometer simultaneously measured the scattered light from angles of 20° to 160° from the forward scattering direction in 4° increments. The angular scattering measurements were then compared with calculations using a Mie scattering code to infer information regarding particulate size. Measurements of particulate mass were made based upon a correlation developed between the scattered light intensity and particulate mass samples trapped in a 0.2-micron filter. Measurements were made in a direct injection single-cylinder spark ignition research engine having a transparent quartz cylinder.
Technical Paper

A Skeletal Chemical Kinetic Model for the HCCI Combustion Process

2002-03-04
2002-01-0423
In Homogeneous Charge Compression Ignition (HCCI) engines, fuel oxidation chemistry determines the auto-ignition timing, the heat release, the reaction intermediates, and the ultimate products of combustion. Therefore a model that correctly simulates fuel oxidation at these conditions would be a useful design tool. Detailed models of hydrocarbon fuel oxidation, consisting of hundreds of chemical species and thousands of reactions, when coupled with engine transport process models, require tremendous computational resources. A way to lessen the burden is to use a “skeletal” reaction model, containing only tens of species and reactions. This paper reports an initial effort to extend our skeletal chemical kinetic model of pre-ignition through the entire HCCI combustion process. The model was developed from our existing preignition model, which has 29 reactions and 20 active species, to yield a new model with 69 reactions and 45 active species.
Technical Paper

The Effects of Fuel Volatility and Structure on HC Emissions from Piston Wetting in DISI Engines

2001-03-05
2001-01-1205
Piston wetting can be isolated from the other sources of HC emissions from DISI engines by operating the engine predominantly on a gaseous fuel and using an injector probe to impact a small amount of liquid fuel on the piston top. This results in a marked increase in HC emissions. All of our prior tests with the injector probe used California Phase 2 reformulated gasoline as the liquid fuel. In the present study, a variety of pure liquid hydrocarbon fuels are used to examine the influence of fuel volatility and structure. Additionally, the exhaust hydrocarbons are speciated to differentiate between the emissions resulting from the gaseous fuel and those resulting from the liquid fuel. It is shown that the HC emissions correspond to the Leidenfrost effect: fuels with very low boiling points yield high HCs and those with a boiling point near or above the piston temperature produce much lower HCs.
Technical Paper

Liquid Film Evaporation Off the Piston of a Direct Injection Gasoline Engine

2001-03-05
2001-01-1204
An optical access engine was used to image the liquid film evaporation off the piston of a simulated direct injected gasoline engine. A directional injector probe was used to inject liquid fuel (gasoline, i-octane and n-pentane) directly onto the piston of an engine primarily fueled on propane. The engine was run at idle conditions (750 RPM and closed throttle) and at the Ford World Wide Mapping Point (1500 RPM and 262 kPa BMEP). Mie scattering images show the liquid exiting the injector probe as a stream and directly impacting the piston top. Schlieren imaging was used to show the fuel vaporizing off the piston top late in the expansion stroke and during the exhaust stroke. Previous emissions tests showed that the presence of liquid fuel on in-cylinder surfaces increases engine-out hydrocarbon emissions.
Technical Paper

In-Situ Mapping and Analysis of the Toyota Prius HEV Engine

2000-08-21
2000-01-3096
The Prius is a major achievement by Toyota: it is the first mass-produced HEV with the first available HEV-optimized engine. Argonne National Laboratory's Advanced Powertrain Test Facility has been testing the Prius for model validation and technology performance and assessment. A significant part of the Prius test program is focused on testing and mapping the engine. A short-length torque sensor was installed in the powertrain in-situ. The torque sensor data allow insight into vehicle operational strategy, engine utilization, engine efficiency, and specific emissions. This paper describes the design and process necessary to install a torque sensor in a vehicle and shows the high-fidelity data measured during chassis dynamometer testing. The engine was found to have a maximum thermodynamic efficiency of 36.4%. Emissions and catalyst efficiency maps were also produced.
Technical Paper

Effects of DTBP on the HCCI Combustion Characteristics of SI Primary Reference Fuels

2005-10-24
2005-01-3740
One option for ignition control of Homogeneous Charge Compression Ignition (HCCI) engines is to use small amounts of ignition-enhancing additives to alter the ignition properties. Di-tertiary Butyl Peroxide (DTBP) is one such additive and it has been suggested as a cetane improver in diesel engines. In this study, the effects of DTBP on spark ignition (SI) primary reference fuels (PRFs, n-heptane and iso-octane) and their blends (PRF20, PRF50, PRF63, PRF87 and PRF92) were investigated during HCCI engine operation. Experiments were run in a single cylinder CFR research engine for three inlet temperatures (410, 450 and 500 K) and several equivalence ratios (0.28 - 0.57) at a constant speed of 800 rpm and a compression ratio of 16.0. Experimental results show that ignition delay time, cycle to cycle variation, and stable operating range were all improved with the addition of less than 2.5% DTBP by volume.
Technical Paper

Two Types of Autoignition and Their Engine Applications

2005-04-11
2005-01-0178
The generally accepted explanation of autoignition in engines is that the reactivity is driven by temperature, where autoignition occurs after the mixture has reached some critical temperature (approx. 1000 K) by a combination of self-heating due to preignition reactions and compression heating due to piston motion and flame propagation. During the course of our investigations into autoignition processes and homogeneous charge compression ignition we have observed some ignitions that begin at much lower temperature (< 550 K). In this paper we describe these observations, our attempts to investigate their origins, and an alternative explanation that proposes that traditional models may be missing the chemistry that explains this behavior. Finally, applications of lower temperature chemical reactions are discussed.
Technical Paper

Further Development of an On-Board Distillation System for Generating a Highly Volatile Cold-Start Fuel

2005-04-11
2005-01-0233
The On-Board Distillation System (OBDS) extracts, from gasoline, a highly volatile crank fuel that enables simultaneous reduction of start-up fuel enrichment and significant ignition timing retard during cold-starting. In a previous paper we reported reductions in catalyst light-off time of >50% and THC emissions reductions >50% over Phase I of the FTP drive cycle. The research presented herein is a further development of the OBDS concept. For this work, OBDS was improved to yield higher-quality start-up fuel. The PCM calibration was changed as well, in order to improve the response to intake manifold pressure transients. The test vehicle was tested over the 3-phase FTP, with exhaust gases speciated to determine NMOG and exhaust toxics emissions. Also, the effectiveness of OBDS at generating a suitable starting fuel from a high driveability index test gasoline was evaluated.
Technical Paper

A New Ignitior for Large-Bore Natural Gas Engines - Railplug Design Improvement and Optimization

2005-04-11
2005-01-0249
It is a very challenging problem to reliably ignite extremely lean mixtures, especially for the low speed, high load conditions of large-bore natural gas engines. If these engines are to be use for the distributed power generation market, it will require operation with higher boost pressures and even leaner mixtures. Both place greater demands on the ignition system. The railplug is a very promising ignition system for lean burn natural gas engines with its high-energy deposition and high velocity plasma arc. It requires care to properly design railplugs for this new application, however. For these engines, in-cylinder pressure and mixture temperature are very high at the time of ignition due to the high boost pressure. Hot spots may exist on the electrodes of the ignitor, causing pre-ignition problems. A heat transfer model is proposed in this paper to aid the railplug design. The electrode temperature was measured in an operating natural gas engine.
Technical Paper

Analysis of Factors that Affect the Performance of Railplugs

2005-04-11
2005-01-0252
As natural gas engines are designed to operate leaner and with increased boost pressure, durability of the spark plugs becomes problematic. Among the various new ignition devices that have been considered to solve some of the problems facing spark plugs, railplugs appear to hold clear advantages in some areas. There are two types of railplugs: coaxial rail and parallel rail. This paper reports the results of an experimental study of various parameters that affect the performance of parallel railplugs. Their performance was quantified by the distance that the arc traveled along the rails from the initiation point. Travel along the rails is thought to be an important performance metric because rail-travel limits excessive local wear and produces a distributed ignition source which can potentially reduce mixture inhomogeneity induced ignition problems.
Technical Paper

Some Observations on the Effects of EGR, Oxygen Concentration, and Engine Speed on the Homogeneous Charge Combustion of n-Heptane

2004-06-08
2004-01-1905
NOx and soot emissions remain critical issues in diesel engines. One method to address these problems is to achieve homogeneous combustion at lower peak temperatures - the goal of research on controlled autoignition. In this paper n-heptane is used to represent a large hydrocarbon fuel and some of the effects of internal and external EGR, oxygen concentration, and engine speed on its combustion have been examined through simulation and experiment. Simulations were conducted using our existing skeletal chemical kinetic model, which combines the chemistry of the low, intermediate, and high temperature regimes. Experiments were carried out in a single cylinder, four-stroke, air cooled engine and a single cylinder, two stroke, water cooled engine. In the four-stroke engine experiments the effects of EGR were examined using heated N2 addition as a surrogate for external EGR and engine modifications to increase internal EGR.
Technical Paper

Potential of Thermal Stratification and Combustion Retard for Reducing Pressure-Rise Rates in HCCI Engines, Based on Multi-Zone Modeling and Experiments

2005-04-11
2005-01-0113
This work investigates the potential of in-cylinder thermal stratification for reducing the pressure-rise rate in HCCI engines, and the coupling between thermal stratification and combustion-phasing retard. A combination of computational and experimental results is employed. The computations were conducted using both a custom multi-zone version and the standard single-zone version of the Senkin application of the CHEMKIN III kinetics-rate code, and kinetic mechanisms for iso-octane. This study shows that the potential for extending the high-load operating limit by adjusting the thermal stratification is very large. With appropriate stratification, even a stoichiometric charge can be combusted with low pressure-rise rates, giving an output of 16 bar IMEPg for naturally aspirated operation. For more typical HCCI fueling rates (ϕ = 0.38 - 0.45), the optimal charge-temperature distribution is found to depend on both the amount of fuel and the combustion phasing.
Technical Paper

Further Development of an Electronic Particulate Matter Sensor and Its Application to Diesel Engine Transients

2008-04-14
2008-01-1065
This paper presents the latest developments in the design and performance of an electronic particulate matter (PM) sensor developed at The University of Texas at Austin (UT) and suitable, with further development, for applications in active engine control of PM emissions. The sensor detects the carbonaceous mass component of PM in the exhaust and has a time-resolution less than 20 (ms), allowing PM levels to be quantified for engine transients. Sample measurements made with the sensor in the exhaust of a single-cylinder light duty diesel engine are presented for both steady-state and transient operations: a steady-state correlation with gravimetric filter measurements is presented, and the sensor response to rapid increases in PM emission during engine transients is shown for several different tip-in (momentary increases in fuel delivery) conditions.
Technical Paper

Prediction of Pre-ignition Reactivity and Ignition Delay for HCCI Using a Reduced Chemical Kinetic Model

2001-03-05
2001-01-1025
Homogeneous Charge Compression Ignition (HCCI) engines have the possibility of low NOx and particulate emissions and high fuel efficiencies. In HCCI the oxidation chemistry determines the auto-ignition timing, the heat release rate, the reaction intermediates, and the ultimate products of combustion. This paper reports an initial effort to apply our reduced chemical kinetic model to HCCI processes. The model was developed to study the pre-ignition characteristics (pre-ignition heat release and start of ignition) of primary reference fuels (PRF) and includes 29 reactions and 20 active species. The only modifications to the model were to make the proscribed adjustments to the fuel specific rate constants, and to enhance the H2O2 decomposition rate to agree with published data.
Technical Paper

Refinement of a Dedicated E85 1999 Silverado with Emphasis on Cold Start and Cold Drivability

2001-03-05
2001-01-0679
The University of Texas 2000 Ethanol Vehicle Challenge team remains focused on cold start, cold drivability, fuel economy, and emissions reduction for our 2000 Ethanol Vehicle Challenge entry. We used the stock PCM for all control functions except control of an innovative cold-start system our team designed. The primary modifications for improved emissions control involved ceramic coating of the exhaust manifolds, use of close-coupled ethanol-specific catalysts, use of a moddified version of the California Emissions Calibrated PCM, and our cold-start system that eliminates the need to overfuel the engine at the beginning of the FTP. Additionally, we eliminated EGR at high load to improve power density. Major modifications, such as increasing the compression ratio or pressure boosting, were eliminated from consideration due to cost, complexity, reliability, or emissions penalties.
Technical Paper

Evaluating the Effects of Restraint Systems on Four Wheel Drive Testing Methodologies: A Collaborative Effort between NVFEL and ANL

2009-04-20
2009-01-1522
Testing vehicles for emissions and fuel economy has traditionally been conducted with a single-axle chassis dynamometer. The 2006 SAE All Wheel Drive Symposium cited four wheel drive (4WD) and all wheel drive (AWD) sales as climbing from 20% toward 30% of a motor vehicle market share. With an increasing number of four wheel-drive vehicles being introduced to the market place, certification testing for emissions and fuel economy has been changed to allow both two wheel drive and four wheel drive testing [1]. As manufacturers plan to test these vehicles in this mode, test methods need to be developed to allow for these changes. This paper focuses on the tie down methods available for 4WD testing to determine possible effects of test methodologies on a traditional 4WD Vehicle and a hybrid vehicle.
X