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Technical Paper

Development of a POD-Based Analysis Approach for Quantitative Comparison of Spray Structure Variations in a Spark-Ignition Direct-Injection Engine

2013-10-14
2013-01-2545
Strong cycle-to-cycle variations of fuel spray are observed due to the highly transient in-cylinder airflow in spark-ignition direct-injection (SIDI) engine. The spray structure comparison based on ensemble-averaged image may be misleading sometimes because the spray images for the same engine running condition could be different from cycle to cycle. Also, the visual comparison of spray images from many cycles is only qualitative and very time-consuming. Therefore, the present paper provides a novel approach to make quantitative comparison of spray structures from different engine conditions, or comparison between experiment and simulation (such as large eddy simulation, LES). The methodology is based on the proper orthogonal decomposition (POD), which has been utilized for in-cylinder turbulent flow research for over a decade.
Technical Paper

Flow Field Characterization of Superheated Sprays from a Multi-Hole Injector by Using High-Speed PIV

2012-04-16
2012-01-0457
Superheated spray is expected to improve the fuel atomization and evaporation processes by introducing fuel temperature as a new control parameter in spark-ignited direct-injection (SIDI) engines. In this study, flow fields of n-hexane spray from a multi-hole injector in both vertical and cross-sectional directions were investigated by using high-speed particle image velocimetry (HS-PIV) within the lower density regions. The results provide insight to the spray-collapsing processes under various superheated conditions. It was found that in axial direction, the vertical velocity increases while the radial velocity decreases with increasing superheat degree, which determines the convergent spray structure. In cross-sectional direction, the dynamic variation of the spray structure and interaction among spray plumes were investigated. The relationship between the spray structure and flow field was found. The flow patterns during and after the injection are significantly different.
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

Combustion and Emissions of Ethanol Fuel (E100) in a Small SI Engine

2003-10-27
2003-01-3262
An air-cooled, four-stroke, 125 cc electronic gasoline fuel injection SI engine for motorcycles is altered to burn ethanol fuel. The effects of nozzle orifice size, fuel injection duration, spark timing and the excess air/ fuel ratio on engine power output, fuel and energy consumptions and engine exhaust emission levels are studied on an engine test bed. The results show that the maximum engine power output is increased by 5.4% and the maximum torque output is increased by 1.9% with the ethanol fuel in comparison with the baseline. At full load and 7000 r/min, HC emission is decreased by 38% and CO emission is decreased 46% on average over the whole engine speed range. However, NOx levels are increased to meet the maximum power output. The experiments of the spark timing show that the levels of HC and NOx emission are decreased markedly by the delay of spark timing.
Technical Paper

Diesel Spray Characterization at Ultra-High Injection Pressure of DENSO 250 MPa Common Rail Fuel Injection System

2017-03-28
2017-01-0821
High fuel injection pressure has been regarded as a key controlling factor for internal combustion engines to achieve good combustion performance with reduced emissions and improved fuel efficiency. For common-rail injection system (CRS) used in advanced diesel engines, fuel injection pressure can often be raised to beyond 200 MPa. Although characteristics of diesel spray has been thoroughly studied, little work has been done at ultra-high injection pressures. In this work, the characteristics of CRS diesel spray under ultra-high injection pressure up to 250 MPa was investigated. The experiments were conducted in an optically accessible high-pressure and high-temperature constant volume chamber. The injection pressure varied from 50 MPa to up to 250 MPa. Both non-evaporating condition and evaporating condition were studied. A single-hole injector was specially designed for this investigation.
Technical Paper

Study on the Optimal Control Strategy of Transient Process for Diesel Engine with Sequential Turbocharging System

2016-10-17
2016-01-2157
Three-phase sequential turbocharging system with two unequal-size turbochargers is developed to improve fuel economy performance and reduce emission of the automotive diesel engine, which satisfies wide range of intake flow demand. However, it results in complicated transient control strategies under frequently changing operating conditions. The present work aims to optimize the control scheme of boost system and fuel injection and evaluate their contributions to the improvement of transient performance. A mean value model for diesel engine was built up in SIMULINK environment and verified by experiment for transient study. Then a mathematical model of optimization issue was established. Strategies of control valves and fuel injection for typical acceleration and loading processes are obtained by coupled calculating of the simulation model and optimization algorithm.
Technical Paper

Effects of Injection Rate Profiles on Auto-Ignition in Ignition Quality Tester

2018-09-10
2018-01-1695
Ignition quality tester (IQT) is a standard experimental device to determine ignition delay time of liquid fuels in a controlled environment in the absence of gas exchange. The process involves fuel injection, spray breakup, evaporation and mixing, which is followed by auto-ignition. In this study, three-dimensional computational fluid dynamics (CFD) is used for prediction of auto-ignition characteristics of diethyl ether (DEE) and ethanol. In particular, the sensitivity of the ignition behavior to different injection rate profiles is investigated. Fluctuant rate profile derived from needle lift data from experiments performs better than square rate profile in ignition delay predictions. DEE, when used with fluctuant injection rate profile resulted in faster ignition, while for ethanol the situation was reversed. The contrasting results are attributed to the difference in local mixing.
Technical Paper

Study of Flash Boiling Spray Combustion in a Spark Ignition Direct Injection Optical Engine Using Digital Image Processing Diagnostics

2019-04-02
2019-01-0252
Flash boiling spray has been proven to be a useful method in providing finer fuel droplet and stronger evaporation in favor of creating a homogeneous fuel-air mixture. Combustion characteristics of flash boiling spray are thus valuable to be investigated systematically for aiding the development of efficient internal combustion system. An experimental study of flash boiling spray combustion in a SIDI optical engine under early injection has been conducted. The fuel, Iso-octane, was used across all tests. Three fuel spray conditions experimented in the study: normal liquid, transitional flash boiling and flare flash boiling sprays, within each case that Pa/Ps ratio was set in (>1), (0.3~1), and (<0.3) respectively. A small quartz insert on the piston enables optical access for observing combustion process; non-intrusive measurements on flame radicals has been carried out using a high-speed color camera.
Technical Paper

An Experimental Study of the Effects of Coolant Temperature on Particle Emissions from a Dual Injection Gasoline Engine

2019-01-15
2019-01-0051
Euro VI emission standards have set a very strict limitation on particulate matter emissions of Gasoline Direct Injection (GDI) engine. It is difficult for GDI engine to meet the Euro VI PN regulation (6×1011#/km) without a series of complicated after-treatment devices such as Gasoline Particulate Filter (GPF). Previous research shows that GDI vehicles under cold start condition account for more than 50% of both particle number and mass emissions during the entire NEDC driving cycle. Dual Injection Gasoline engine is based on the GDI engine by adding a set of port fuel injection system. The good mixing characteristics of the port fuel injection system can help to reduce the particulate matter emissions of the GDI engine during the cold start condition.
Technical Paper

Application of the Newly Developed KLSA Model into Optimizing the Compression Ratio of a Turbocharged SI Engine with Cooled EGR

2018-10-30
2018-32-0037
Owing to the stochastic nature of engine knock, determination of the knock limited spark angle (KLSA) is difficult in engine cycle simulation. Therefore, the state-of-the-art knock modeling is mostly limited to either merely predicting knock onset (i.e. auto-ignition of end gas) or combining a simple unburned mass fraction (UMF) model representative of knock intensity (KI). In this study, a newly developed KLSA model, which takes both predictions of knock onset and intensity into account, is firstly introduced. Multiple variables including the excess air ratio, EGR ratio, cylinder pressure and the end gas temperature are included in the knock onset model. Based on the auto-ignition theory of hot spots in end gas, both the energy density and heat release rate in hot spots are taken into consideration in the KI model.
Technical Paper

Influence of the Injector Configuration on the Spray Evaporation Characteristics under Superheated Conditions

2015-09-01
2015-01-1900
In spark ignition direct injection (SIDI) engines, the injector configuration plays an important role on influencing the spray atomization and evaporation. In order to optimize the injector configuration to generate a better fuel spray, the further study to understand the effect of injector configuration is needed. In this study, the influence of the hole length to diameter ratio (L/D) on the fuel spray evaporation is investigated in a constant volume chamber under various operating conditions. The laser induced exciplex fluorescence (LIEF) technique is utilized to capture the vapor fluorescence signal of fuel spray. The fuel sprays with the fuel temperature ranging from 45°C to 85°C and ambient pressure ranging from 20kPa to 100kPa are investigated to study the influences of superheated degree (SD) on the spray evaporation.
Journal Article

Analyzing the Cycle-to-Cycle Variations of Vapor and Liquid Phases of Evaporating SIDI Sprays via Proper Orthogonal Decomposition Technique

2015-09-01
2015-01-1901
In this study, the spray characteristics of three multi-hole injectors, namely a 2-hole injector, a 4-hole injector, and a 6-hole injector were investigated under various superheated conditions. Fuel pressure was kept constant at 10MPa. Fuel temperature varied from 20°C to 85°C, and back pressure ranged from 20kPa to 100kPa. Both liquid phase and vapor phase of the spray were investigated via laser induced exciplex fluorescence technique. Proper orthogonal decomposition technique was applied to analyze the cycle-to-cycle variations of the liquid phase and vapor phase of the fuel spray separately. Effects of fuel temperature, back pressure, superheated degree and nozzle number on spray variation were revealed. It shows that higher fuel temperature led to a more stable spray due to enhanced evaporation which eliminated the fluctuating structures along the spray periphery. Higher back pressure led to higher spray variation due to increased interaction between spray and ambient air.
Technical Paper

Experimental Research on Mixture Distribution of Diesel Premixed Low-Temperature Combustion

2015-09-01
2015-01-1839
The diesel premixed low-temperature combustion mode avoids the generation of thick mixture and the high temperature region in which a great amount of NOx and PM generates. It makes a significant reduction in the emissions of both NOx and PM available at the same time. However, with the quantity of pre-injection increases and the injection time advances, the emission of HC increases significantly, which causes a decrease in the combustion efficiency. Studies have shown that the flame quench caused by too thick or too lean mixture and the oil film on the chamber is the main source for the emission of HC. As a result, understanding the mechanism of atomization and evaporation of the fuel and the formation of the mixture makes significant sense. This paper focuses on the mixture formation process. And the methods of testing the distribution of the mixture, the influential factors and control methods are studied.
Technical Paper

Influence of Early and Late Fuel Injection on Air Flow Structure and Kinetic Energy in an Optical SIDI Engine

2018-04-03
2018-01-0205
The turbulent in-cylinder air flow and the unsteady high-pressure fuel injection lead to a highly transient air fuel mixing process in spark-ignition direct-injection (SIDI) engines, which is the leading cause for combustion cycle-to-cycle variation (CCV) and requires further investigation. In this study, crank-angle resolution particle image velocimetry (PIV) was employed to simultaneously measure the air flow and fuel spray structure at 1300 rpm in an optically accessible single-cylinder SIDI engine. The measurement was conducted at the center tumble plane of the four-valve pent-roof engine, bisecting the spark plug and fuel injector. 84 consecutive cycles were recorded for three engine conditions, i.e. (1) none-fueled motored condition, (2) homogeneous-charge mode with start of injection (SOI) during intake (50 crank-angle degree (CAD) after top dead center exhaust, aTDCexh), and (3) stratified-charge mode with SOI during mid compression (270 aTDCexh).
Technical Paper

Contrary Effects of Nozzle Length on Spray Primary Breakup under Subcooled and Superheated Conditions

2018-04-03
2018-01-0302
Nozzle length has been proven influencing fuel spray characteristics, and subsequently fuel-air mixing and combustion processes. However, almost all existing related studies are conducted when fuel is subcooled, of which fuel evaporation is extremely weak, especially at the near nozzle region. In addition, injector tip can be heated to very high temperature in SIDI engines, which would trigger flash boiling fuel spray. Therefore, in this study, effect of nozzle length on spray characteristics is investigated under superheated conditions. Three single-hole injectors with different nozzle length were studied. High speed backlit imaging technique was applied to acquire magnified near nozzle spray images based on an optical accessible constant volume chamber. Fuel pressure was maintained at 15 MPa, and n-hexane was chosen as test fuel.
Technical Paper

Effects of Spark Timing with Other Engine Operating Parameters on the Particulate Emissions of a Dualinjection Gasoline Engine During Warm-up Conditions

2019-12-19
2019-01-2214
Gasoline direct injection (GDI) has been a mainstream technology due to its higher thermal efficiency and better power output. However, with increasingly stringent emission regulations introduced (EURO VI PN limits: 6 x l011#/km), high particulate matter (PM) emission of GDI engine has been a serious problem that limits its further development. Previous studies have found that cold-start and warm-up operation conditions play the dominant role in engine-out particulate emissions. In this paper, emission characteristics during the cold-start were first studied by controlling the coolant temperature. A Cambustion DMS500 fast particle spectrometer was employed to analyze the PM emissions. In order to reduce the engine-out emissions of cold-start, a dual injection system which combines port-fuel-injection (PFI) and direct-injection (DI) was applied in a four-cylinder gasoline engine.
Technical Paper

System Characteristics of Direct and Secondary Loop Heat Pump for Electrical Vehicles

2018-04-03
2018-01-0063
The electricity energy consumption for passenger cabin heating can drastically shorten the driving range for electric vehicles in cold climates. Mobile heat pump system is considered as an effective method to improve heating efficiency. This study investigates the system characteristics of mobile heat pump systems for electrical vehicle application. Based on KULI thermal management software, simulation models including HFC-R134a direct heat pump (DHP) and secondary loop heat pump (SLHP) were developed. The secondary loop employed in the SLHP includes a coolant pump, an indoor heater core and a plate heat exchanger, instead of an indoor condenser in the DHP. The use of a secondary loop has advantages to improve air outlet temperature uniformity. The simulation models were verified by measured data obtained from calorimeter experiments. By adopting simulation models, the effects of indoor and outdoor temperatures on system performance and cycle characteristics were discussed.
Technical Paper

Experimental Investigation of Injection Strategies to Improve Intelligent Charge Compression Ignition (ICCI) Combustion with Methanol and Biodiesel Direct Injection

2020-09-15
2020-01-2072
Applications of methanol and biodiesel in internal combustion engines have raised widespread concerns, but there is still huge scope for improvement in efficiency and emissions. The brand-new combustion mode, named as Intelligent Charge Compression Ignition (ICCI) combustion, was proposed with methanol-biodiesel dual fuel direct injection. In this paper, effects of injection parameters such as two-stage split-injections, injection timings, injection pressure and intake pressure on engine combustion and emissions were investigated at IMEP = 8, 10, and 12 bar. Results show that the indicated thermal efficiency up to 53.5% and the NOx emissions approaching to EURO VI standard can be obtained in ICCI combustion mode.
Technical Paper

Numerical Investigation of the Effects of Port Water Injection Timing on Performance and Emissions in a Gasoline Direct Injection Engine

2020-04-14
2020-01-0287
Port water injection is considered as a promising strategy to further improve the combustion performance of internal combustion engines for its benefit in knock resistance by reducing the cylinder temperature. A thorough investigation of the port water injection technique is required to fully understand its effects on the engine combustion process. This study explores the potential of the port water injection technique in improving the performance of a turbo charged Gasoline Direct Injection engine. A 3D computational fluid dynamics model is applied to simulate the in-cylinder mixing and combustion for this engine both with and without water injection. Different water injection timings are investigated and it is found that the injection timing greatly effects the mass of water which enters the combustion chamber, both in liquid and vapor form.
Journal Article

In-Flame Soot Sampling and Morphology Analysis in an Optical Spark-Ignition Direct-Injection (SIDI) Engine

2018-04-03
2018-01-1418
Stringent particulate emission regulations are applied to spark-ignition direct-injection (SIDI) engines, calling for a significant in-cylinder reduction of soot particles. To enhance fundamental knowledge of the soot formation and oxidation process inside the cylinder of the engine, a new in-flame particle sampling system has been developed and implemented in a working optical SIDI engine with a side-mounted, wall-guided injection system. Using the sampling probes installed on the piston top, the soot particles are directly sampled from the petrol flame for detailed analysis of particle size distribution, structure, and shape. At the probe tip, a transmission electron microscope (TEM) grid is stored for the soot collection via thermophoresis, which is imaged and post-processed for statistical analysis. Simultaneously, the flame development was recorded using two high-speed cameras to evidence the direct exposure of the sampling grids to the soot-laden diffusion flames and pool fires.
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