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Technical Paper

Stratified Mixture Formation and Combustion Process for Wall-guided Stratified-charge DISI Engines with Different Piston Bowls by Simulation

2010-04-12
2010-01-0595
This paper presents the simulation of in-cylinder stratified mixture formation, spray motion, combustion and emissions in a four-stroke and four valves direct injection spark ignition (DISI) engine with a pent-roof combustion chamber by the computational fluid dynamics (CFD) code. The Extended Coherent Flame Combustion Model (ECFM), implemented in the AVL-Fire codes, was employed. The key parameters of spray characteristics related to computing settings, such as skew angle, cone angle and flow per pulse width with experimental measurements were compared. The numerical analysis is mainly focused on how the tumble flow ratio and geometry of piston bowls affect the motion of charge/spray in-cylinder, the formation of stratified mixture and the combustion and emissions (NO and CO₂) for the wall-guided stratified-charge spark-ignition DISI engine.
Technical Paper

Material Compatibilities of Biodiesels with Elastomers, Metals and Plastics in a Diesel Engine

2009-11-02
2009-01-2799
The effects of biodiesel on the swelling of the elastomers and plastics and the corrosion of metals are studied by the immersion tests. The results indicate that biodiesels make little corrosion effect on aluminum, steel and little swelling impact on plastics, but a significant corrosion may be taken place on cooper and brass for some sourced biodiesels. For nitrile-butadiene rubber, the variation of swelling properties in biodiesels is slightly higher than that in diesel. For the non-diesel-resistant elatomers, the variation of swelling properties is lower than those in diesel. The production process and biodiesel source have an influence on the result of elastomer swelling and corrosion. The relationship between the impact of biodiesel on materials and biodiesels properties are also discussed.
Technical Paper

Compatibility of Biodiesels and Their Blends with Typical Rubbers and Copperish Metals

2010-04-12
2010-01-0476
The swelling of ‘O’ rings of 3 typical rubbers (NBR, FKM, EPDM) and the corrosion of 2 typical copperish metal pieces (Copper, Brass) were investigated. The fuel samples included 14 kinds of biodiesels, 1 kind of diesel, and 4 kinds of blends respectively for 2 kinds of biodiesels. The changes in mass and size of ‘O’ rings were measured with an electronic balance and a vernier caliper. The surface corrosion of copperish metals was recorded with photos. It was found that the swelling of NBR in pure biodiesels were generally larger than those in diesel. The mass and size of FKM almost did not change in both pure biodiesels and diesel. The swelling of EPDM became less in pure biodiesels than that in diesel. When the blend ratios of biodiesels were less than 10%, the change rates in mass, inner diameter and section diameter of NBR, FKM and EPDM were similar between blended fuels and diesel.
Technical Paper

Effect of First Cycle Fuel Injection Timing on Performance of a PFI Engine during Quick Start for HEV Application

2011-04-12
2011-01-0886
Idle stopping is one of the most important fuel saving methods for hybrid electric vehicle (HEV). While the enriched injection strategy which was employed to ensure reliable ignition of first cycle will leads to even more fuel film stayed in the intake port, all of the liquid film will evaporate randomly and interfere the mixture air-fuel ratio of the followed cycles. The fuel transport of the first cycle should be enhanced to reduce the residual fuel film, and then the control of the cycle-by-cycle air-fuel ratio will become easier and the combustion and HC emissions will also be better. In this paper the mixture preparation characteristics of the unfired first cycle, as well as the combustion and HC emissions characteristics of the fired first cycle under various injection timing strategies such as close-valve injection, mid-valve injection, and open-valve injection were investigated.
Technical Paper

A Study on the Factors Affecting Heated Wall Impinging Characteristics of SCR Spray

2011-04-12
2011-01-1311
Many studies show that under diesel engine operating conditions, SCR reductant sprays will impinge on the wall of exhaust pipes. In order to understand this impinging process of SCR reductant spray, and to analyze what factors affect it, a test bench was set up by means of high speed video camera. At atmospheric pressure, SCR spray was injected on a heated metal wall, the impacts of wall temperature, injection pressure, injection height and angle on developing characteristics of SCR reductant spray after impinging on the heated wall have been researched and analyzed. The results show that the heated wall temperature has a great impact on the spray developing process, when wall temperature is lower than 405K, after water evaporated the crystallized urea will remain on the wall to block exhaust pipes. When wall temperature is higher, the atomization and evaporation of SCR reductant spray will be better, and the hydrolysis process of urea will be faster.
Technical Paper

Design and Simulation of Serial Hybrid Electric Moped Powertrain

2008-06-23
2008-01-1567
According to the requirements of two-wheel vehicle's future market and the characteristic of urban road conditions in China, the advantages and disadvantages of three basic configurations for the Hybrid Electric Vehicle are compared, finally, the serial hybrid configuration is chosen to be applied to hybrid Electric Moped solution. The selection principle of main components of this hybrid powertrain system includes ICE, generator, battery and hub motor, and the optimal match for performance parameters of these components are introduced in this paper. Then, a hybrid system model is established based on AVL-CRUISE. The simulations of fuel efficiency and exhaust emissions for both serial hybrid moped and conventional motorcycle is offered.
Technical Paper

A Study of Crevice HC Mechanism Based on the Transient HC Test Data and the Double Zone Combustion Model

2008-06-23
2008-01-1652
The effectiveness of after-treatment systems depends on the exhaust gas temperature, which is low during cold-start. As a result, Euro III, Euro IV and FTP75 require that the emissions tests include exhaust from the beginning of cold start. It is proved that 50%∼80% of HC and CO emissions are emitted during the cold start and the amount of unburned fuel from the crevices during starting is much higher than that under warmed engine conditions. The piston crevices is the most part of combustion chamber crevices, and results of mathematical simulations show that the piston crevice contribution to HC emissions is expected to increase during cold engine operation. Based on the transient HC test data and the double zone combustion model, this paper presents the study of the crevice HC Mechanism of the first firing cycle at cold start on an LPG SI Engine. A fast-response flame ionization detector (FFID) was employed to measure transient HC emissions of the first firing cycle.
Technical Paper

Misfiring Control in Current Cycle at Engine Start Employing Ion Sensing Technology

2009-11-02
2009-01-2713
In this paper a method of misfiring control in current cycle at engine start is presented. With this novel method, the high HC emissions of gasoline engine employed in traditional or hybrid electrical vehicles will be avoided. By the feedback of ion current signal, misfire phenomenon is identified within 30 degrees crank angle after spark plug ignited. Then, the ignition coil will be recharged and the plug sparked again to promote air fuel mixture oxidation and deplete the unburned hydrocarbon produces in exhaust gas. On the other hand, too late ignition will not always result in normal combustion, a kind of reaction similar with slow oxidation also occurs in such case.
Technical Paper

Fuel Injection Optimization during Engine Quick Start by Means of Cycle-by-Cycle Control Strategy for HEV Application

2009-11-02
2009-01-2718
Engine-off strategy are popular used in hybrid electric vehicles (HEV) for fuel saving. The engine of an HEV will start and stop frequently according to the road condition. In order to obtain excellent fuel economy and emissions performance, the fuel injection during engine quick start should be optimized. In this paper, the characteristic of mixture formation and the HC emissions at the first 5 cycles which contribute the most HCs were investigated. After the analysis of mixture preparation during start process, the HC emissions during engine quick start were optimized by means of cycle-by-cycle fuel injection control strategy. The fuel mixture concentration during start-up process fluctuates more dramatically under hot start condition. Typically, the mixture at 4th and 5th cycle is over-riched. Based on the original engine calibration, the fuel injection at the initial 5 cycles was optimized respectively.
Technical Paper

Characteristics of Three-way Catalyst during Quickly Start-up Process in a PFI Engine for HEV Application

2009-04-20
2009-01-1325
The characteristics of three-way-catalyst during engine start process were investigated based on a simulated start/stop test system for HEV application. Although the catalyst has already reached its light-off temperature, the conversion efficiency is poor during engine start process due to the deviation of lambda from stoichiometric. The high concentration hydrocarbon emission spike can be stored by catalyst substrate temporarily, then it is released. This dynamic process decreases the conversion efficiency for the following exhaust hydrocarbon emission. When the initial temperature of catalyst substrate before engine start increased from 150°C to 400°C, the conversion efficiency for both the hydrocarbon and NO are increased.
Technical Paper

Transient Characteristics of Combustion and Emissions during Start up at Higher Cranking Speed in a PFI Engine for HEV Application

2008-10-06
2008-01-2420
The transient characteristics of combustion and emissions during the engine start up at different higher cranking speeds for hybrid electric vehicle (HEV) applications were presented in this paper. Cycle-by-cycle analysis was done for each start up case. Intake air mass during the first several cycles decrease as the engine was cranked at higher speed. Ignition timing is delayed with higher cranking speed, which leads to an increase of exhaust temperature. For various start up cases, similar quantity of fuel is injected at the first cycle, but the ignition timing is significantly delayed to meet the acceleration requirement when cranking speed enhanced. Because of the deterioration of intake charge, the air-fuel mixture is over-enriched in the first several cycles for the cases at higher cranking speed. With cranking speed is increased, the in-cylinder residual gas fraction rises, which leads to poor combustion and decrease of mass fraction of burned fuel.
Technical Paper

Power Matching and Control Strategy of Plug-in Series Hybrid Electric Car

2010-10-25
2010-01-2195
In this paper, based on the plug-in series hybrid electric vehicle development project, the vehicle technology solutions and the match of power system parameters were analyzed. The vehicle control strategies were identified and optimized according to plug-in hybrid vehicle features. The plug-in series hybrid, rule-based logic threshold switching control strategy, charge depleting (CD) mode and charge-sustaining (CS) mode are chosen according to the key factors, such as the environment, performance requirements, technical requirements and cost. And then the structure and model of vehicle control strategy were established to carry out vehicle energy management and power system control. The parameter selection, electric drive system matching, energy storage system design based on the requirement of vehicle performance, system architecture and control strategy are presented.
Technical Paper

Spray Characteristics of Biodiesel and Diesel Fuels under High Injection Pressure with a Common Rail System

2010-10-25
2010-01-2268
Biodiesel has been paid more and more attention as a renewable fuel due to some excellent properties such as renewable, high cetane number, ultralow sulfur content, no aromatic hydrocarbon, high flash point, low CO2 emission when compared with diesel. While others physical properties like high viscosity, high surface tension, big density and bad volatility would spoil the spray characteristics of biodiesel fuel, which will affect the thermal efficiency when running in diesel engine. Accompanied with constant volume vessel and high speed video camera system, a high pressure common rail system, which could provide an injection pressure of 180 MPa, is used to investigate the characteristics of jatropha curcas biodiesel, palm oil biodiesel and diesel fuel. The effects of injection pressures and ambient densities on spray characteristics of these fuels are studied.
Technical Paper

Optimization of Control Strategy for Engine Start-stop in a Plug-in Series Hybrid Electric Vehicle

2010-10-25
2010-01-2214
Plug-in hybrid electric vehicles (PHEVs) provide significantly improvement in fuel economy over conventional vehicles as well as reductions in greenhouse gas and petroleum. Numerous recent reports regarding control strategy, power train configuration, driving pattern, all electric range (AER) and their effects on fuel consumption and electric energy consumption of PHEVs are reported. Meanwhile, the control strategy for engine start-stop and mileage between recharging events from the electricity grid also has an important influence on the petroleum displacement potential of PHEVs, but few reports are published. In this paper, a detailed simulation model is set up for a plug-in series hybrid electric vehicle (PSHEV) employing the AVL CRUISE. The model was employed to predict the AER of the baseline PSHEV using rule-based logical threshold switching control strategy.
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

The Social Economical Benefit Estimation by HEVs Application-Shanghai Case Study

2008-06-23
2008-01-1565
In this paper, a case study of Shanghai HEVs application and its effects on the social and environmental benefits are presented based on the multi views on the different aspects, such as, not only for the fuel consumption saving, but also emissions reduction and health effect, agriculture loss and cleaning cost. The results show that the potential benefits for the society from HEVs application are markedly with the increase of the ratio of HEV in the population of vehicle. Based on this, the policy to promote the HEV purchased by consumers is very important at the beginning of HEV into market.
Journal Article

Estimation on the Location of Peak Pressure at Quick Start of HEV Engine Employing Ion Sensing Technology

2008-06-23
2008-01-1566
In this paper an estimation method on location of peak pressure (LPP) employing flame ionization measurement, with the spark plug as a sensor, was discussed to achieve combustion parameters estimation at quick start of HEV engines. Through the cycle-based ion signal analysis, the location of peak pressure can be extracted in individual cylinder for the optimization of engine quick start control of HEV engine. A series of quick start processes with different cranking speed and engine coolant temperature are tested for establishing the relationship between the ion signals and the combustion parameters. An Artificial Neural Network (ANN) algorithm is used in this study for estimating these two combustion parameters. The experiment results show that the location of peak pressure can be well established by this method.
Technical Paper

Characteristics of Output Performances and Emissions of Diesel Engine Employed Common Rail Fueled with Biodiesel Blends from Wasted Cooking Oil

2008-06-23
2008-01-1833
In this paper, the characteristics of performance and emissions of diesel and biodiesel blends are studied in a four-cylinder DI engine employing common rail injection system. The results show that engine output power is further reduced and brake specific fuel consumption (BSFC) increased with the increase of the blend concentration. B100 provides average reduction by 8.6% in power and increase by 11% in BSFC. With respect to the emissions, although NOx emissions were increased with increasing the blend concentration, the increase depends on the load. Filter smoke number is reduced with increasing the blend concentration. At the same time, NO, NO2 and other specific emissions are also investigated. In addition, difference of performance and emission between standard parameters of ECU and modified parameters of ECU is investigated for B10 and B20 based on same output power. The results show that NOx emission and FSN are still lower than baseline diesel.
Technical Paper

Characteristics of Particulates and Exhaust Gases Emissions of DI Diesel Engine Employing Common Rail Fuel System Fueled with Bio-diesel Blends

2008-06-23
2008-01-1834
In this paper, characteristics of gas emission and particle size distribution are investigated in a common rail diesel engine fueled with biodiesel blends. Gas emission and particle size distribution are measured by AVL FTIR - SESAM and SMPS respectively. The results show that although biodiesel blends would result in higher NOx emissions, characteristics of NOx emissions were also dependent on the engine load for waste cooking oil methyl ester. Higher blend concentration results in higher NO2 emission after two diesel oxidation catalyst s (DOC). A higher blend concentration leads to lower CO and SO2 emissions. No significant difference of Alkene emission is found among biodiesel blends. The particle size distributions of diesel exhaust aerosol consist of a nucleation mode (NM) with a peak below 50N• m and an accumulation mode with a peak above 50N • m. B100 will result in lower particulates with the absence of NM.
Technical Paper

Characteristics of Combustion and Emissions in a DI Engine Fueled with Biodiesel Blends from Soybean Oil

2008-06-23
2008-01-1832
Combustion and emission characteristics of diesel and biodiesel blends (soybean methyl ester) were studied in a single-cylinder Direct Injection (DI) engine at different loads and a constant speed. The results show that NOx emission and fuel consumption are increased with increasing biodiesel percentage. Reduction of smoke opacity is significant at higher loads with a higher biodiesel ratio. Compared with the baseline diesel fuel, B20 (20% biodiesel) has a slight increase of NOx emission and similar fuel consumption. Smoke emission of B20 is close to that of diesel fuel. Results of combustion analysis indicate that start of combustion (SOC) for biodiesel blends is earlier than that for diesel. Higher biodiesel percentage results in earlier SOC. Earlier SOC for biodiesel blends is due to advanced injection timing from higher density and bulk modulus and lower ignition delay from higher cetane number.
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