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Technical Paper

Pressure Drop and Soot Regeneration Characteristics through Hexagonal and Square Cell Diesel Particulate Filters

2017-03-28
2017-01-0979
Although diesel engines have higher output torque, lower fuel consumption, and lower HC pollutant emissions, larger amounts of NOx and PM are emitted, compared with equivalent gasoline engines. The diesel particulate filters (DPF) have proved one of the most promising aftertreatment technologies due to the more stringent particulate matters (PM) regulations. In this study, the computational fluid dynamics (CFD) model of DPF was built by utilizing AVL-Fire software code. The main objective of this paper was to investigate the pressure drop and soot regeneration characteristics of hexagonal and conventional square cell DPFs with various inlet mass flow rates, inlet temperatures, cell densities, soot loads and ash loads. Different cell geometry shapes of DPF were evaluated under various ash distribution types.
Technical Paper

Effects of Lubricating Oil Metallic Content on Morphology, Nanostructure and Graphitization Degree of Diesel Engine Exhaust Particles

2017-03-28
2017-01-1009
In this paper, the influences of metallic content of lubricating oils on diesel particles were investigated. Three lubricating oils with different levels of metallic content were used in a 2.22 Liter, two cylinders, four stroke, and direct injection diesel engine. 4.0 wt. % and 8 wt. % antioxidant and corrosion inhibitor (T202) were added into baseline lubricating oil to improve the performance respectively. Primary particle diameter distributions and particle nanostructure were compared and analyzed by Transmission Electron Microscope. The graphitization degrees of diesel particles from different lubricating oils were analyzed by Raman spectroscopy. Conclusions drawn from the experiments indicate that the metallic content increases the primary particles diameter at 1600 rpm and 2200 rpm. The primary particles diameter ranges from 5 nm to 65 nm and the distribution conformed to Gaussian distribution.
Technical Paper

Surface Functional Groups and Graphitization Degree of Soot in the Sooting History of Methane Premixed Flame

2017-03-28
2017-01-1003
The evolution of surface functional groups (SFGs) and the graphitization degree of soot generated in premixed methane flames are studied and the correlation between them is discussed. Test soot samples were obtained from an optimized thermophoretic sampling system and probe sampling system. The SFGs of soot were determined by Fourier transform infrared spectroscopy (FT-IR) and X-ray photoelectron spectroscopy (XPS) after removing the soluble impurities from the soot samples, while the graphitization degree of soot was characterized by Raman spectrum and electron energy loss spectroscopy (EELS). The results reveal that the number of aliphatic C-H groups and C=O groups shows an initial increase and then decrease in the sooting history. The large amount of aliphatic C-H groups and small amount of aromatic C-H groups in the early stage of the soot mass growth process indicate that aliphatic C-H groups make a major contribution to the early stage of soot mass growth.
Technical Paper

A Simulation Study on Particle Motion in Diesel Particulate Filter Based on Microcosmic Channel Model

2018-04-03
2018-01-0964
As the prime after-treatment device for diesel particulate matter (PM) emission control, Diesel Particulate Filter (DPF) has been widely used for its high particle capture efficiency. In order to study the particle motion and deposition distributions in the DPF inlet channel, a 2-D wall flow DPF microcosmic channel model is built in this paper. The motion trajectories of particles with different sizes are investigated considering the drag force, Brownian motion, gravity and Saffman lift. The effects of the space velocity on particle motion trajectories and deposition distributions inside the inlet channel are evaluated. These results demonstrate that the particle motion trajectories are highly dependent on particle sizes and influenced by the space velocity. The effect of the Brownian motion is obvious for fine particles and suppressed when the space velocity is raised.
Technical Paper

Simulating the Flow and Soot Loading in Wall- Flow DPF Using a Two-Dimensional Mesoscopic Model

2018-04-03
2018-01-0955
A two-dimensional mesoscopic approach has been developed to investigate the flow and soot loading in the micro-channels of diesel particulate filter. Soot particle size examined is in the range of 10 nm to 10 μm. The flow is solved by an incompressible lattice Boltzmann model and the transport of solid particle is described in a Lagrangian frame of reference by cell automation probabilistic model. The lattice Boltzmann-cell automation probabilistic model (LB-CA model) is validated with the results of previous studies. The heterogeneous porous wall of DPF is generated by quartet structure generation set (QSGS). The effects of porous wall on the pressure field and velocity field are investigated. The distribution and deposition of soot particles with different sizes in clean channels are simulated. The dynamic evolution of solid boundary in soot particle capture process is investigated and the effects of the deposited soot particles on flow field are evaluated.
Technical Paper

Potentials of External Exhaust Gas Recirculation and Water Injection for the Improvement in Fuel Economy of a Poppet Valve 2-Stroke Gasoline Engine Equipped with a Two-Stage Serial Charging System

2018-04-03
2018-01-0859
Engine downsizing is one of the most effective means to improve the fuel economy of spark ignition (SI) gasoline engines because of lower pumping and friction losses. However, the occurrence of knocking combustion or even low-speed pre-ignition at high loads is a severe problem. One solution to significantly increase the upper load range of a 4-stroke gasoline engine is to use 2-stroke cycle due to the double firing frequency at the same engine speed. It was found that a 0.7 L two-cylinder 2-stroke poppet valve gasoline engine equipped with a two-stage serial boosting system, comprising a supercharger and a downstream turbocharger, could replace a 1.6 L naturally aspirated 4-stroke gasoline engine in our previous research, but its fuel economy was close to that of the 4-stroke engine at upper loads due to knocking combustion.
Technical Paper

Pressure Drop Characteristics Through DPF with Various Inlet to Outlet Channel Width Ratios

2015-04-14
2015-01-1019
The main objective of this paper was to investigate the pressure drop characteristics of ACT (asymmetric cell technology) design filter with various inlet mass flow rates, soot loads and ash loads by utilizing 1-D computational Fluid Dynamics (CFD) method. The model was established by AVL Boost code. Different ratios of inlet to outlet channel width inside the DPF (Diesel Particulate Filter) were investigated to determine the optimal structure in practical applications, as well as the effect of soot and ash interaction on pressure loss. The results proved that pressure drop sensitivity of different inlet/outlet channel width ratios increases with the increased inlet mass flow rate and soot load. The pressure drop increases with the increased channel width ratio at the same mass flow rate. When there is little soot deposits inside DPF, the pressure drop increases with the bigger inlet.
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.
Technical Paper

A Hybrid Combustion Control Strategy for Heavy Duty Diesel Engines Based on the Technologies of Multi-Pulse Injections, Variable Boost Pressure and Retarded Intake Valve Closing Timing

2011-04-12
2011-01-1382
Combustion control strategy for high efficiency and low emissions in a heavy duty (H D) diesel engine was investigated experimentally in a single cylinder test engine with a common rail fuel system, EGR (Exhaust Gas Recirculation) system, boost system and retarded intake valve closing timing actuator. For the operation loads of IMEPg (Gross Indicated Mean Effective Pressure) less than 1.1 MPa the low temperature combustion (LTC) with high rate of EGR was applied. The fuel injection modes of either single injection or multi-pulse injections, boost pressure and retarded intake valve closing timing (RIVCT) were also coupled with the engine operation condition loads for high efficiency and low emissions. A higher boost pressure played an important role in improving fuel efficiency and obtaining ultra-low soot and NOx emissions.
Technical Paper

Experimental Study of Multiple Injections and Coupling Effects of Multi-Injection and EGR in a HD Diesel Engine

2009-11-02
2009-01-2807
Diesel engines have to reduce emissions to satisfy future emission legislations. The purpose of this paper is to investigate the effect of multiple injections and the combined effects of multi-injection and EGR on HD diesel engine emissions and performance. A common rail fuel injection system and high pressure EGR system based on variable geometry turbocharger (VGT) were used. Injection parameters (injection dwell and mass) were adjusted with different injection strategies (pilot-main, pilot-pilot-main, main-post and pilot-main-post) to find out the influence of these parameters on combustion and emissions. Secondly the coupling effects of multi-injection and EGR were evaluated at both high and low loads. Finally, while keeping NOx at 2.0 g/kW.h by adjusting EGR rate, the influence of injection parameters and EGR were tested to highlight their influence on smoke and BSFC.
Technical Paper

Noise Source Identification of a Diesel Engine Using Inverse Boundary Element Method

2008-04-14
2008-01-0729
The inverse boundary element method (IBEM) is presented to accurately identify the noise sources of a diesel engine in this study. The sound pressures on four near-field planes were measured as inputs for the method. Then, the acoustic model of the full diesel engine was established using the boundary element method, and the acoustic transfer vectors (ATV) between the surface normal velocity and acoustic pressure at field points were calculated over the frequency range of interest. Based on the measured sound pressure and the ATVs, the surface normal velocity distribution of the diesel engine was reconstructed by the IBEM. The reconstructed pressures at two reference field points were compared with the measured ones. Furthermore, the panel contribution of each engine component was analyzed through the reconstructed surface velocity.
Technical Paper

Effects of Late Intake Valve Closing Timing on Thermal Efficiency and Emissions Based on a Two-stage Turbocharger Diesel Engine

2013-04-08
2013-01-0276
This paper investigated the effects of late intake valve closing timing (IVCT) and two-stage turbocharger systems matching based on partially premixed combustion strategy. Tests were performed on a 12-liter L6 heavy-duty engine at loads up to 10 bar BMEP at various speed. IVCT (where IVCT is -80°ATDC, -65°ATDC and -55°ATDC at 1300 rpm, 1600 rpm and 1900 rpm, respectively) lowered the intake and exhaust difference pressure, reducing pumping loss and improved the effective thermal efficiency by 1%, 1.5% and 2% at BMEP of 5 bar at 1300 rpm, 1600 rpm and 1900 rpm. For certain injection timings and EGR rate, it is found that a significant reduction in soot (above 30%) and NOx (above 70%) emissions by means of IVCT. This is due to that IVCT lowered effective compression ratio and temperature during the compression stroke, resulting in a longer ignition delay as the fuel mixed more homogeneous with the charge air ahead of ignition.
Technical Paper

Kinetic Modeling of Soot Formation with Highlight in Effects of Surface Activity on Soot Growth for Diesel Engine Partially Premixed Combustion

2013-04-08
2013-01-1104
In this study, Partially Premixed Combustion (PPC) on a modified heavy-duty diesel engine was realized by hybrid combustion control strategy with flexible fuel injection timing, injection rate pattern modulation and high ratio of exhaust gas recirculation (EGR) at different engine loads. It features with different degrees of fuel/air mixture stratifications. The very low soot emissions of the experiments called for further understanding on soot formation mechanism so that to promote the capability of prediction. A new soot model was developed with highlight in effects of surface activity on soot growth for soot formation prediction in partially premixed combustion diesel engine. According to previous results from literatures on the importance of acetylene as growth specie of PAH and soot surface growth, a gas-phase reduced kinetic model of acetylene formation was developed and integrated into the new soot model.
Technical Paper

Theoretical and Practical Mechanisms on Lowering Exhaust Emission Levels for Diverse Types of Spark Ignition Engines

2008-06-23
2008-01-1545
The exhaust aftertreatment strategy is one of the most fundamental aspects of spark ignition engine technologies. For various types of engines (e.g., carburetor engine, PFI engine and GDI engine), measuring, purifying, modeling, and control strategies regarding the exhaust aftertreatment systems vary significantly. The primary goal of exhaust aftetreatment systems is to reduce the exhaust emission levels of NOx, HC and CO as well as to lower combustion soot. In general, there is a tradeoff among different engine performance aspects. The exhaust catalytic systems, such as the three way catalyst (TWC) and lean NOx trap (LNT) converters, can be applied together with the development of other engine technologies (e.g., variable valve timing, cold start). With respect to engine soot, some advanced diagnosing techniques are essential to obtain thorough investigation of exhaust emission mechanisms.
Technical Paper

Advanced Gasoline Engine Management Platform for Euro IV & CHN IV Emission Regulation

2008-06-23
2008-01-1704
The increasingly stringent requirements in relation to emission reduction and onboard diagnostics are pushing the Chinese automotive industry toward more innovative solutions and a rapid increase in electronic control performance. To manage the system complexity the architecture will require being well structure on hardware and software level. The paper introduces GEMS-K1 (Gasoline Engine Management System - Kit 1). GEMS-K1 is a platform being compliant with Euro IV emission regulation for gasoline engines. The application software is developed using modeling language, the code is automatically generated from the model. The driver software has a well defined structure including microcontroller abstraction layer and ECU abstraction layer. The hardware is following design rules to be robust, 100% testable and easy to manufacture. The electronic components use the latest innovation in terms of architecture and technologies.
Technical Paper

The Application and Optimization of EGR-LNT Synergetic Control System on Lean-burn Gasoline Engine

2015-04-14
2015-01-1036
Ensuring lower emissions and better economy (fuel economy and after-treatment economy) simultaneously is the pursuit of future engines. An EGR-LNT synergetic control system was applied to a modified lean-burn CA3GA2 gasoline engine. Results showed that the synergetic control system can achieve a better NOx reduction than sole EGR and sole LNT within a proper range of upstream EGR rate and without the penalty in fuel consumption. It also has the potential to save costly noble metals in LNT, but excessive or deficient upstream EGR would make the synergetic control system inefficiency. In order to guarantee the objectivity of the effect of EGR-LNT synergetic control system on NOx reduction, another modified lean-burn CA4GA5 gasoline engine was additionally tested.
Technical Paper

A Comparative Study on the Fuel Economy Improvement of a Natural Gas SI Engine at the Lean Burn and the Stoichiometric Operation both with EGR under the Premise of Meeting EU6 Emission Legislation

2015-09-01
2015-01-1958
In order to further study the effects of air and EGR dilution on the fuel economy improvement of natural gas engines under the premise of meeting EU6 legislation, a comparison between stoichiometric operation with EGR and lean burn operation with and without EGR has been conducted at 1600rpm 50% and 75% load. The conversion efficiencies of the catalysts for both NOx and CH4 emissions are assumed at 90% for lean burn operation. Experiment results indicate that under the condition of meeting both NOx and CH4 predetermined engine-out emissions limits for EU6 legislation, lean operation with a small fraction of EGR dilution enables more advanced combustion phasing compared to pure lean operation, which results in much better fuel economy, thus further improvement compared to stoichiometric operation is achieved.
Technical Paper

Achievement of Diesel Low Temperature Combustion through Higher Boost and EGR Control Coupled with Miller Cycle

2015-04-14
2015-01-0383
Diesel engines generally tend to produce a very low level of NOx and soot through the application of Miller Cycle, which is mainly due to the low temperature combustion (LTC) atmosphere resulting from the Miller Cycle utilization. A CFD model was established and calibrated against the experimental data for a part load operation at 3000 r/min. A designed set of Miller-LTC combustion modes were analyzed. It is found that a higher boost pressure coupled with EGR can further tap the potential of Miller-LTC cycle, improving and expanding the Miller-LTC operation condition. The simulated results indicated that the variation of Miller timings can decrease the regions of high temperatures and then improve the levels and trade-off relationship of NOx and soot. The in-cylinder peak pressure and NOx emissions were increased dramatically though the problem of insufficient intake charge was resolved by the enhanced intake pressure that is equivalent to dual-stage turbo-charging.
Technical Paper

Pump-End Control Technology for Small Engine Management System

2015-04-14
2015-01-1731
A pump-end control technology for pump-nozzle fuel supply unit, in which the pump is driven and controlled electrically for pressurizing and metering the fuel fed into an engine, is studied. The unit is composed of a solenoid driven plunger pump, a high-pressure fuel tube, and an auto-open nozzle, and only the pump is propelled by PWM power from an ECU. To achieve a higher metering accuracy, a metering theory deciding the fuel discharging rate was developed by studying the system using a physical-mathematical model. The developed so called T3 theory makes the fuel supply unit with excellent metering consistency under various conditions, which can meet the requirement of fuel supply unit application to small engine management system. The study reveals that an electrically characterized variable, T3, which is associated with the net output energy, can directly results in a mass discharge.
Technical Paper

An Investigation of Abnormal Spray Behaviors of Multi-Hole GDI Injector

2016-04-05
2016-01-0848
The main objective of this paper is to investigate the influence of injection pressures and fuel temperatures on the secondary injection spray evolution at the end of injection from a multi-hole gasoline direct injection (GDI) injector by Mie-scattering technique. The results of this paper show that the overall injection process can be classified into five stages which are injection delay stage, main injection stage, dwell stage, secondary injection stage and ligaments breakup stage respectively. Especially, the secondary injection occurs at the end of main injection, which is abnormal and undesirable spray behaviors. During the injection, big droplets and ligaments are injected through nozzle orifices at low speed. As the injection pressure increases, the phase of the secondary injection advances, and the injection duration decreases. At medium injection pressures (at 6, 8 MPa), more quantity of fuel are injected as ligaments.
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