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Journal Article

Investigation of the Acoustic Performance of After Treatment Devices

2011-05-17
2011-01-1562
Diesel engines produce harmful exhaust emissions and high exhaust noise levels. One way of mitigating both exhaust emissions and noise is via the use of after treatment devices such as Catalytic Converters (CC), Selective Catalytic Reducers (SCR), Diesel Oxidation Catalysts (DOC), and Diesel Particulate Filters (DPF). The objective of this investigation is to characterize and simulate the acoustic performance of different types of filters so that maximum benefit can be achieved. A number of after treatment device configurations for trucks were selected and measured. A measurement campaign was conducted to characterize the two-port transfer matrix of these devices. The simulation was performed using the two-port theory where the two-port models are limited to the plane wave range in the filter cavity.
Journal Article

Gasoline Direct Injection Compression Ignition (GDCI) - Diesel-like Efficiency with Low CO2 Emissions

2011-04-12
2011-01-1386
A single-cylinder engine was used to study the potential of a high-efficiency combustion concept called gasoline direct-injection compression-ignition (GDCI). Low temperature combustion was achieved using multiple injections, intake boost, and moderate EGR to reduce engine-out NOx and PM emissions engine for stringent emissions standards. This combustion strategy benefits from the relatively long ignition delay and high volatility of regular unleaded gasoline fuel. Tests were conducted at 6 bar IMEP - 1500 rpm using various injection strategies with low-to-moderate injection pressure. Results showed that triple injection GDCI achieved about 8 percent greater indicated thermal efficiency and about 14 percent lower specific CO2 emissions relative to diesel baseline tests on the same engine. Heat release rates and combustion noise could be controlled with a multiple-late injection strategy for controlled fuel-air stratification. Estimated heat losses were significantly reduced.
Technical Paper

Mode Transition between Low Temperature Combustion and Conventional Combustion with EGR and Injection Modulation in a Diesel Engine

2011-04-12
2011-01-1389
Mode transition between low temperature combustion and conventional combustion was investigated in a direct injection diesel engine. Low temperature diesel combustion was realized by means of high exhaust gas recirculation rate (69~73%) and early injection timing (-28~ -16 crank angle degree after top dead center) compared with those (20% exhaust gas recirculation rate and -8 crank angle degree after top dead center) of conventional combustion. Tests were carried out at different engine speeds and injection pressures. Exhaust gas recirculation rate was changed transiently by controlling each throttle angle for fresh air and exhaust gas recirculation to implement mode transition. Various durations for throttle transition were applied to investigate the effect of speed change of exhaust gas recirculation rate on the characteristics of mode transition.
Technical Paper

Identifying Optimal Operating Points in Terms of Engineering Constraints and Regulated Emissions in Modern Diesel Engines

2011-04-12
2011-01-1388
In recent decades, “physics-based” gas-dynamics simulation tools have been employed to reduce development timescales of IC engines by enabling engineers to carry out parametric examinations and optimisation of alternative engine geometry and operating strategy configurations using desktop PCs. However to date, these models have proved inadequate for optimisation of in-cylinder combustion and emissions characteristics thus extending development timescales through additional experimental development efforts. This research paper describes how a Stochastic Reactor Model (SRM) with reduced chemistry can be employed to successfully determine in-cylinder pressure, heat release and emissions trends from a diesel fuelled engine operated in compression ignition direct injection mode using computations which are completed in 147 seconds per cycle.
Journal Article

Effects of Post-Injection Strategies on Near-Injector Over-Lean Mixtures and Unburned Hydrocarbon Emission in a Heavy-Duty Optical Diesel Engine

2011-04-12
2011-01-1383
Post-injection strategies aimed at reducing engine-out emissions of unburned hydrocarbons (UHC) were investigated in an optical heavy-duty diesel engine operating at a low-load, low-temperature combustion (LTC) condition with high dilution (12.7% intake oxygen) where UHC emissions are problematic. Exhaust gas measurements showed that a carefully selected post injection reduced engine-out load-specific UHC emissions by 20% compared to operation with a single injection in the same load range. High-speed in-cylinder chemiluminescence imaging revealed that without a post injection, most of the chemiluminescence emission occurs close to the bowl wall, with no significant chemiluminescence signal within 27 mm of the injector. Previous studies have shown that over-leaning in this near-injector region after the end of injection causes the local equivalence ratio to fall below the ignitability limit.
Technical Paper

A Demonstration of Simultaneous Infrared and Visible Imaging Techniques with Pressure Data in an Optically Accessible Diesel Engine Operating at Part Load with High EGR

2011-04-12
2011-01-1395
This work presents a method for simultaneously capturing visible and infrared images along with pressure data in an optical Diesel engine based on the International 4.5L VT275 engine. This paper seeks to illustrate the merits of each imaging technique for visualizing both in-cylinder fuel spray and combustion. The engine was operated under a part load, high simulated exhaust gas recirculation operating condition. Experiments examining fuel spray were conducted in nitrogen. Overlays of simultaneously acquired infrared and visible images are presented to illustrate the differences in imaging between the two techniques. It is seen that the infrared images spatially describe the fuel spray, especially fuel vapors, and the fuel mixing process better than the high-speed visible images.
Technical Paper

Injector Tip Design Improvement of the Diesel Injectors

2011-04-12
2011-01-1397
Parameters of the fuel economy and the exhaust gases pollution of the high-speed diesel engines, with unshared and half-shared combustion chambers, are predetermined by processes of fuel spray and fuel-air mixture creation. The parameters of these processes (fuel spraying and development of flame structure dynamic) appreciably depend from design features of a flowing part of the injector tips. The major parameters of the injector tips design are the spraying nozzles length and the ratio of the length these nozzles to their diameters. The experimental research of the D-245.12C type diesel engine has been carried out. Fuel injectors of the diesel engine were equipped with injector tips of different spray nozzles lengths. The experimental data show improvement fuel efficiency, reduction of emissions and smoke due to optimization of geometries in the injector tip.
Technical Paper

Using Multiple Injection Strategies in Diesel PCCI Combustion: Potential to Extend Engine Load, Improve Trade-off of Emissions and Efficiency

2011-04-12
2011-01-1396
The Premixed Charge Compression Ignition (PCCI) engine has the potential to reduce soot and NOx emissions while maintaining high thermal efficiency at part load conditions. However, several technical barriers must be overcome. Notably ways must be found to control ignition timing, expand its limited operation range and limit the rate of heat release. In this paper, comparing with single fuel injection, the superiority of multiple-pulse fuel injection in extending engine load, improve emissions and thermal efficiency trade-off using high exhaust gas recirculation (EGR) and boost in diesel PCCI combustion is studied by engine experiments and simulation study. It was found that EGR can delay the start of hot temperature reactions, reduce the reaction speed to avoid knock combustion in high load, is a very useful method to expand high load limit of PCCI. EGR can reduce the NOx emission to a very small value in PCCI.
Journal Article

Low Emissions and High-Efficiency Diesel Combustion Using Highly Dispersed Spray with Restricted In-Cylinder Swirl and Squish Flows

2011-04-12
2011-01-1393
A new clean diesel combustion concept has been proposed and its excellent performance with respect to gas emissions and fuel economy were demonstrated using a single cylinder diesel engine. It features the following three items: (1) low-penetrating and highly dispersed spray using a specially designed injector with very small and numerous orifices, (2) a lower compression ratio, and (3) drastically restricted in-cylinder flow by means of very low swirl ports and a lip-less shallow dish type piston cavity. Item (1) creates a more homogeneous air-fuel mixture with early fuel injection timings, while preventing wall wetting, i.e., impingement of the spray onto the wall. In other words, this spray is suitable for premixed charge compression ignition (PCCI) operation, and can decrease both nitrogen oxides (NOx) and soot considerably when the utilization range of PCCI is maximized.
Technical Paper

Continuous Load Adjustment Strategy of a Gasoline HCCI-SI Engine Fully Controlled by Exhaust Gas

2011-04-12
2011-01-1408
Homogeneous charge compression ignition (HCCI) technology is promising to reduce engine exhaust emissions and fuel consumption. However, it is still confronted with the problem of its narrow operation range that covers only the light and medium loads. Therefore, to expand the operation range of HCCI, mode switching between HCCI combustion and transition SI combustion is necessary, which may bring additional problems to be resolved, including load fluctuation and increasing the complexity of control strategy, etc. In this paper, a continuously adjustable load strategy is proposed for gasoline engines. With the application of the strategy, engine load can be adjusted continuously by the in-cylinder residual gas fraction in the whole operation range. In this research, hybrid combustion is employed to bridge the gaps between HCCI and traditional SI and thus realize smooth transition between different load points.
Technical Paper

Development of Low Pressure Loop EGR System for Diesel Engines

2011-04-12
2011-01-1413
Low pressure loop (LPL) EGR systems are effective means of simultaneously reducing the NOx emissions and fuel consumption of diesel engines. Further lower emission levels can be achieved by adopting a system that combines LPL EGR with a NOx storage and reduction (NSR) catalyst. However, this combined system has to overcome the issue of combustion fluctuations resulting from changes in the air-fuel ratio due to EGR gas recirculation from either NOx reduction control or diesel particulate filter (DPF) regeneration. The aim of this research was to reduce combustion fluctuations by developing LPL EGR control logic. In order to control the combustion fluctuations caused by LPL EGR, it is necessary to estimate the recirculation time. First, recirculation delay was investigated. It was found that recirculation delay becomes longer when the LPL EGR flow rate or engine speed is low.
Technical Paper

An Investigation of the Potential of EGR stratification for Reducing Pressure Rise Rate in HCCI Combustion by using Rapid Compression Machine

2011-08-30
2011-01-1762
HCCI (Homogeneous Charge Compression Ignition) engine is able to achieve low NOx and particulate emissions as well as high efficiency. However, its operation range is limited by the knocking at high load, which is the consequence of excessively rapid pressure rises. It has been suggested that making thermal or fuel inhomogeneities can be used to solve this problem, since these inhomogeneities have proved to create different auto-ignition timing zones. It has also been suggested that EGR (Exhaust Gas Recirculation) has a potential to reduce pressure rise rate. But according to a past report, it was concluded that under the same fueling ratio and CA50 with different initial temperature and EGR ratio, the maximum PRR is almost constant. The purpose of this study is to investigate the fundamental effects of EGR. First, I considered EGR homogeneous charge case. In this case, the effects of EGR and its components like CO₂, H₂O or N₂ on HCCI combustion process is argued.
Journal Article

A Study of Newly Developed HCCI Engine With Wide Operating Range Equipped With Blowdown Supercharging System

2011-08-30
2011-01-1766
To extend the operating range of a gasoline HCCI engine, the blowdown supercharging (BDSC) system and the EGR guide were developed and experimentally examined. The concepts of these techniques are to obtain a large amount of dilution gas and to generate a strong in-cylinder thermal stratification without an external supercharger for extending the upper load limit of HCCI operation whilst keeping dP/dθmax and NOx emissions low. Also, to attain stable HCCI operation using the BDSC system with wide operating conditions, the valve actuation strategy in which the amount of dilution gas is smaller at lower load and larger at higher load was proposed. Additionally to achieve multi-cylinder HCCI operation with wide operating range, the secondary air injection system was developed to reduce cylinder-to-cylinder variation in ignition timing. As a result, the acceptable HCCI operation could be achieved with wide operating range, from IMEP of 135 kPa to 580 kPa.
Technical Paper

Future Emission Concepts versus Fuel Quality Aspects - Challenges and Technical Concepts

2011-08-30
2011-01-2097
From current point of view future emission legislations for heavy-duty engines as well as industrial engines will require complex engine internal measures in combination with sophisticated aftertreatment systems as well as according control strategies to reach the emission targets. With EU VI, JP 09/NLT and US10 for heavy-duty engines as well as future Tier4 final or stage IV emission legislation for industrial applications, EGR + DPF + SCR probably will be combined for most applications and therefore quite similar technological approaches will be followed up in Europe as well as in the US and in Japan. Most “emerging markets” all over the world follow up the European, US or Japanese emission legislation with a certain time delay. Therefore similar technologies need to be introduced in these markets in the future. On the other hand specific market boundary conditions and requirements have to be considered for the development of tailored system concepts in these markets.
Journal Article

Development of Di-Air - A New Diesel deNOx System by Adsorbed Intermediate Reductants

2011-08-30
2011-01-2089
An unprecedented phenomenon that achieves high NOx conversion was found over an NSR catalyst. This phenomenon occurs when continuous short cycle injections of hydrocarbons (HCs) are supplied at a predetermined concentration in lean conditions. Furthermore, this phenomenon has a wider range of applicability for different catalyst temperatures (up to 800 degrees Celsius) and SVs, and for extending thermal and sulfur durability than a conventional NOx storage and reduction system. This paper analyzes the reaction mechanism and concludes it to be highly active HC-deNOx by intermediates generated from adsorbed NOx over the base catalysts and HCs partially oxidized by oscillated HC injection. Subsequently, a high performance deNOx system named Di-Air (diesel NOx aftertreatment by adsorbed intermediate reductants) was demonstrated that applies this concept to high speed driving cycles.
Technical Paper

Design Optimization of Non-Catalyzed DPF from Viewpoint of Back Pressure in Ash loading State

2011-08-30
2011-01-2091
Back pressure of Diesel Particulate Filter (DPF) varies with accumulation of soot and/or ash. Soot can be cleaned in a high temperature oxidation (regeneration) process. But ash which is incombustible particulate matter derived from lubricant oil, engine wear, etc. cannot be cleaned from DPF without mechanical ash removal process and influences the back pressure perpetually. Design and control of DPF involving variation of the back pressure with ash accumulation will provide further improvement of fuel consumption and reliable operation in extended vehicle life time. Nevertheless, empirical investigations concerning ash accumulation are few because of the long testing time due to the slow accumulation rate, i.e. 0.5 - 2mg/mile [19]. In this investigation, four different designs of Cordierite (Cd) DPF were subjected to an accelerated ash accumulation test which is utilizing artificial ash powder.
Technical Paper

Experimental Investigation of Applying Raw Fuel Injection Technique for Reducing Methane in Aftertreatment of Diesel Dual Fuel Engines Operating under Medium Load Conditions

2011-08-30
2011-01-2093
Towards the effort of using natural gas as an alternative fuel for a diesel engine, the concept of Diesel Dual Fuel (DDF) engine has been shown as a strong candidate. Typically, DDF's engine-out emission species such as soot and nitrogen oxides are decreased while carbon monoxide and hydrocarbons are increased. The aftertreatment system is required in order to reduce these pollutant emissions from DDF engines. Additionally, DDF engine exhaust has a wide temperature span and is rich in oxygen, which makes HC emissions, especially methane (CH₄), difficult to treat. Until now, it is widely accepted that the key parameter influencing methane oxidation in a catalytic converter is high exhaust temperature. However, a comprehensive understanding of what variables in real DDF engine exhausts most influencing a catalytic converter performance are yet to be explored.
Journal Article

Particulate Matter Sampling and Volatile Organic Compound Removal for Characterization of Spark Ignited Direct Injection Engine Emissions

2011-08-30
2011-01-2100
More stringent emissions regulations are continually being proposed to mitigate adverse human health and environmental impacts of internal combustion engines. With that in mind, it has been proposed that vehicular particulate matter (PM) emissions should be regulated based on particle number in addition to particle mass. One aspect of this project is to study different sample handling methods for number-based aerosol measurements, specifically, two different methods for removing volatile organic compounds (VOCs). One method is a thermodenuder (TD) and the other is an evaporative chamber/diluter (EvCh). These sample-handling methods have been implemented in an engine test cell with a spark-ignited direct injection (SIDI) engine. The engine was designed for stoichiometric, homogeneous combustion.
Technical Paper

Fuel Sulfur Effect on Nano-PM Formation from Diffusion Flame

2011-08-30
2011-01-2055
Recently, for reduction of PM emission from diesel engine, low sulfur diesel fuel was introduced and commercialized. There are some reports for effect of fuel sulfur on PM characteristics by using engine dynamometer tests. However, it is difficult to understand mechanism of PM formation and effect of fuel sulfur on PM formation process. Thus, investigation by a simple flame is effective way for understanding detail PM formation process. In this paper, effect of sulfur content in fuel on PM characteristics was investigated by using laboratory-scale PM generator. Test fuels were diesel and surrogate diesel fuel, and sulfur concentration in the surrogate fuel was controlled with thiophene addition. Effects of fuel sulfur on PM were clarified with characteristics of PM obtained from PM number distribution measurements and PM compositions analysis.
Technical Paper

De-NOx Characteristics of a Combined System of LNT and SCR according to Space Velocity

2011-08-30
2011-01-2088
The purpose of this paper is to investigate the adsorption and desorption characteristics of only LNT and SCR catalysts with respect to SV (Space Velocity) and the de-NOx performance of a combined system of LNT and SCR according to the SV. The adsorption time to reach NOx concentration of 500 ppm at SV = 14,000 1/h of the LNT catalyst was about 1,000 sec. The physically and chemically absorbed NH₃ on the SCR catalyst desorbed in same concentration though various SVs. The NOx conversion of the LNT decreased with SV increased in range of 350° or lower temperature, the formation quantity of NH₃ increased as SV increased in the lower temperature range. The NOx conversion of the SCR with SV = 14,000 1/h showed 95% at 320°, the effect of SV on the NOx conversion was not so much. The NOx conversion of the combined system of LNT and SCR with fresh catalysts appeared maximum value of 70% and hydrothermal aging at 900° decreased about to 25% below range of 300°.
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