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Technical Paper

Experimental Validation of Jet Fuel Surrogates in an Optical Engine

2017-03-28
2017-01-0262
Three jet fuel surrogates were compared against their target fuels in a compression ignited optical engine under a range of start-of-injection temperatures and densities. The jet fuel surrogates are representative of petroleum-based Jet-A POSF-4658, natural gas-derived S-8 POSF-4734 and coal-derived Sasol IPK POSF-5642, and were prepared from a palette of n-dodecane, n-decane, decalin, toluene, iso-octane and iso-cetane. Optical chemiluminescence and liquid penetration length measurements as well as cylinder pressure-based combustion analyses were applied to examine fuel behavior during the injection and combustion process. HCHO* emissions obtained from broadband UV imaging were used as a marker for low temperature reactivity, while 309 nm narrow band filtered imaging was applied to identify the occurrence of OH*, autoignition and high temperature reactivity.
Technical Paper

Simulation of Dual-Fuel-CI and Single-Fuel-SI Engine Combustion Fueled with CNG

2016-04-05
2016-01-0789
With increasing interest to reduce the dependency on gasoline and diesel, alternative energy source like compressed natural gas (CNG) is a viable option for internal combustion engines. Spark-ignited (SI) CNG engine is the simplest way to utilize CNG in engines, but direct injection (DI) Diesel-CNG dual-fuel engine is known to offer improvement in combustion efficiency and reduction in exhaust gases. Dual-fuel engine has characteristics similar to both SI engine and diesel engine which makes the combustion process more complex. This paper reports the computational fluid dynamics simulation of both DI dual-fuel compression ignition (CI) and SI CNG engines. In diesel-CNG dual-fuel engine simulations and comparison to experiments, attention was on ignition delay, transition from auto-ignition to flame propagation and heat released from the combustion of diesel and gaseous fuel, as well as relevant pollutants emissions.
Technical Paper

The Development of an Electronic Control Unit for a High Pressure Common Rail Diesel/Natural Gas Dual-Fuel Engine

2014-04-01
2014-01-1168
Natural gas has been considered to be one of the most promising alternative fuels due to its lower NOx and soot emissions, less carbon footprint as well as attractive price. Furthermore, higher octane number makes it suitable for high compression ratio application compared with other gaseous fuels. For better economical and lower emissions, a turbocharged, four strokes, direct injection, high pressure common rail diesel engine has been converted into a diesel/natural gas dual-fuel engine. For dual-fuel engine operation, natural gas as the main fuel is sequentially injected into intake manifold, and a very small amount of diesel is directly injected into cylinder as the ignition source. In this paper, a dual-fuel electronic control unit (ECU) based on the PowerPC 32-bit microprocessor was developed. It cooperates with the original diesel ECU to control the fuel injection of the diesel/natural gas dual-fuel engine.
Technical Paper

GDi Nozzle Parameter Studies Using LES and Spray Imaging Methods

2014-04-01
2014-01-1434
Development of in-cylinder spray targeting, plume penetration and atomization of the gasoline direct-injection (GDi) multi-hole injector is a critical component of combustion developments, especially in the context of the engine downsizing and turbo-charging trend that has been adopted in order to achieve the European target CO2, US CAFE, and concomitant stringent emissions standards. Significant R&D efforts are directed towards the optimization of injector nozzle designs in order to improve spray characteristics. Development of accurate predictive models is desired to understand the impact of nozzle design parameters as well as the underlying physical fluid dynamic mechanisms resulting in the injector spray characteristics. This publication reports Large Eddy Simulation (LES) analyses of GDi single-hole skew-angled nozzles, with β=30° skew (bend) angle and different nozzle geometries.
Journal Article

Role of Volatility in the Development of JP-8 Surrogates for Diesel Engine Application

2014-04-01
2014-01-1389
Surrogates for JP-8 have been developed in the high temperature gas phase environment of gas turbines. In diesel engines, the fuel is introduced in the liquid phase where volatility plays a major role in the formation of the combustible mixture and autoignition reactions that occur at relatively lower temperatures. In this paper, the role of volatility on the combustion of JP-8 and five different surrogate fuels was investigated in the constant volume combustion chamber of the Ignition Quality Tester (IQT). IQT is used to determine the derived cetane number (DCN) of diesel engine fuels according to ASTM D6890. The surrogate fuels were formulated such that their DCNs matched that of JP-8, but with different volatilities. Tests were conducted to investigate the effect of volatility on the autoignition and combustion characteristics of the surrogates using a detailed analysis of the rate of heat release immediately after the start of injection.
Journal Article

Pilot Injection Ignition Properties Under Low-Temperature, Dilute In-Cylinder Conditions

2013-10-14
2013-01-2531
Measurements of ignition behavior, homogeneous reactor simulations employing detailed kinetics, and quantitative in-cylinder imaging of fuel-air distributions are used to delineate the impact of temperature, dilution, pilot injection mass, and injection pressure on the pilot ignition process. For dilute, low-temperature conditions characterized by a lengthy ignition delay, pilot ignition is impeded by the formation of excessively lean mixture. Under these conditions, smaller pilot mass or higher injection pressures further lengthen the pilot ignition delay. Similarly, excessively rich mixtures formed under relatively short ignition delay conditions typical of conventional diesel combustion will also prolong the ignition delay. In this latter case, smaller pilot mass or higher injection pressures will shorten the ignition delay. The minimum charge temperature required to effect a robust pilot ignition event is strongly dependent on charge O2 concentration.
Technical Paper

Investigation of Low-Temperature Combustion in an Optical Engine Fueled with Low Cetane Sasol JP-8 Fuel Using OH-PLIF and HCHO Chemiluminescence Imaging

2013-04-08
2013-01-0898
Low cetane JP-8 fuels have been identified as being difficult to use under conventional diesel operation. However, recent focus on low-temperature combustion (LTC) modes has led to an interest in distillate hydrocarbon fuels having high volatility and low autoignition tendency. An experimental study is performed to evaluate low-temperature combustion processes in a small-bore optically-accessible diesel engine operated in a partially-premixed combustion mode using low-cetane Sasol JP-8 fuel. This particular fuel has a cetane number of 25. Both single and dual injection strategies are tested. Since long ignition delay is a consequence of strong autoignition resistance, under the conditions examined, low cetane Sasol JP-8 combustion can only take place with a double injection strategy: one pilot injection event in the vicinity of exhaust TDC and one main injection event near firing TDC.
Technical Paper

Self-Ignition Calculation of Diesel Spray

2012-04-16
2012-01-1262
This paper describes a computer simulation of Diesel spray formation and the locations of self-ignition nuclei. The spray is divided into small elementary volumes in which the amounts of fuel and fuel vapours, air, mean, maximum and minimum fuel droplet diameter are calculated, as well as their number. The total air-fuel and air-fuel vapour ratios are calculated for each elementary volume. The paper introduces a new criterion for determining self-ignition nuclei, based on assumptions that the strongest self-ignition probability lies in those elementary volumes containing the stoichiometric air ratio, where the fuel is evaporated or the fuel droplet diameter is equal to or lower than 0.0065 mm. The most efficient combustion in regard to consumption and emission will be in those elementary volumes containing stoichiometric air ratio, and fuel droplets with the lowest mean diameters. Measurements of injection and combustion were carried out in a transparent research engine.
Journal Article

Investigation of Fuel Effects on Spray Atomization and Evaporation Studied for a Multi-hole DISI Injector with a Late Injection Timing

2011-08-30
2011-01-1982
The influence of fuel composition on sprays was studied in an injection chamber at DISI conditions with late injection timing. Fuels with high, mid and low volatility (n-hexane, n-heptane, n-decane) and a 3-component mixture with similar fuel properties like gasoline were investigated. The injection conditions were chosen to model suppressed or rapid evaporation. Mie scattering imaging and phase Doppler anemometry were used to investigate the liquid spray structure. A spray model was set up applying the CFD-Code OpenFOAM. The atomization was found to be different for n-decane that showed a smaller average droplet size due to viscosity dependence of injected mass. And for evaporating conditions, a stratification of the vapor components in the 3-component fuel spray was observed.
Technical Paper

Influence of the fuel quantity on the spray formation and ignition under current engine relevant conditions

2011-08-30
2011-01-1928
Flexible and multiple injections are an important strategy to fulfill today's exhaust emission regulations. To optimize injection processes with an increasing number of adjustable parameters knowledge about the basic mechanisms of spray breakup, propagation, evaporation and ignition is mandatory. In the present investigation the focus is set on spray formation and ignition. In order to simulate current diesel-engine conditions measurements were carried out in a high-temperature (1000 K) and high-pressure (10 MPa) vessel with optical accesses. A piezo servo-hydraulic injector pressurized up to 200 MPa was used to compare four single injection durations and four multi-injection patterns in the ignition phase. All measurements were performed with CEC RF-03-06, a legislative reference fuel. For the spray measurements, a program of 16 to 18 different operating points was chosen to simulate engine conditions from cold start to full load.
Technical Paper

Characterization of Internal flow and Spray of Multihole DI Gasoline Spray using X-ray Imaging and CFD

2011-08-30
2011-01-1881
Multi-hole DI injectors are being adopted in the advanced downsized DISI ICE powertrain in the automotive industry worldwide because of their robustness and cost-performance. Although their injector design and spray resembles those of DI diesel injectors, there are many basic but distinct differences due to different injection pressure and fuel properties, the sac design, lower L/D aspect ratios in the nozzle hole, closer spray-to-spray angle and hense interactions. This paper used Phase-Contrast X ray techniques to visualize the spray near a 3-hole DI gasoline research model injector exit and compared to the visible light visualization and the internal flow predictions using with multi-dimensional multi-phase CFD simulations. The results show that strong interactions of the vortex strings, cavitation, and turbulence in and near the nozzles make the multi-phase turbulent flow very complicated and dominate the near nozzle breakup mechanisms quite unlike those of diesel injections.
Technical Paper

Interactions of Multi-hole DI Sprays with Charge Motion and their Implications to Flexible Valve-trained Engine Performance

2011-08-30
2011-01-1883
Advanced valvetrain coupled with Direct Injection (DI) provides an opportunity to simultaneous reduction of fuel consumption and emissions. Because of their robustness and cost performance, multi-hole injectors are being adopted as gasoline DI fuel injectors. Ethanol and ethanol-gasoline blends synergistically improve the performance of a turbo-charged DI gasoline engine, especially in down-sized, down-sped and variable-valvetrain engine architecture. This paper presents Mie-scattering spray imaging results taken with an Optical Accessible Engine (OAE). OAE offers dynamic and realistic in-cylinder charge motion with direct imaging capability, and the interaction with the ethanol spray with the intake air is studied. Two types of cams which are designed for Early Intake Valve Close (EIVC) and Later Intake Valve Close (LIVC) are tested, and the effect of variable valve profile and deactivation of one of the intake valves are discussed.
Technical Paper

Characterization of Multi-hole Spray and Mixing of Ethanol and Gasoline Fuels under DI Engine Conditions

2010-10-25
2010-01-2151
Because of their robustness and cost performance, multi-hole gasoline injectors are being adopted as the direct injection (DI) fuel injector of choice as vehicle manufacturers look for ways to reduce fuel consumption without sacrificing power and emission performance. To realize the full benefits of direct injection, the resulting spray needs to be well targeted, atomized, and appropriately mixed with charge air for the desirable fuel vapor concentration distributions in the combustion chamber. Ethanol and ethanol-gasoline blends synergistically improve the turbo-charged DI gasoline performance, especially in down-sized, down-sped and variable-valve-train engine architecture. This paper presents the spray imaging results from two multi-hole DI gasoline injectors with different design, fueled with pure ethanol (E100) or gasoline (E0), under homogeneous and stratified-charge conditions that represent typical engine operating points.
Journal Article

Effects of Fuel Cell Material Properties on Water Management Using CFD Simulation and Neutron Imaging

2010-04-12
2010-01-0934
Effects of fuel cell material properties on water management were numerically investigated using Volume of Fluid (VOF) method in the FLUENT. The results show that the channel surface wettability is an important design variable for both serpentine and interdigitated flow channel configurations. In a serpentine air flow channel, hydrophilic surfaces could benefit the reactant transport to reaction sites by facilitating water transport along channel edges or on channel surfaces; however, the hydrophilic surfaces would also introduce significantly pressure drop as a penalty. For interdigitated air flow channel design, it is observable that liquid water exists only in the outlet channel; it is also observable that water distribution inside GDL is uneven due to the pressure distribution caused by interdigitated structure. An in-situ water measurement method, neutron imaging technique, was used to investigate the water behavior in a PEM fuel cell.
Journal Article

Spray Characterization of Ethanol Gasoline Blends and Comparison to a CFD Model for a Gasoline Direct Injector

2010-04-12
2010-01-0601
Operation of flex fuel vehicles requires operation with a range of fuel properties. The significant differences in the heat of vaporization and energy density of E0-E100 fuels and the effect on spray development need to be fully comprehended when developing engine control strategies. Limited enthalpy for fuel vaporization needs to be accounted for when developing injection strategies for cold start, homogeneous and stratified operation. Spray imaging of multi-hole gasoline injectors with fuels ranging from E0 to E100 and environmental conditions that represent engine operating points from ambient cold start to hot conditions was performed in a spray chamber. Schlieren visualization technique was used to characterize the sprays and the results were compared with Laser Mie scattering and Back-lighting technique. Open chamber experiments were utilized to provide input and validation of a CFD model.
Journal Article

Experimental Investigation of the Interaction of MultipleGDI Injections using Laser Diagnostics

2010-04-12
2010-01-0596
In present GDI engines, multiple injection strategies are often employed for engine cold start mixture formation. In the future, these strategies may also be used to control the combustion process, and to prevent misfiring or high emission levels. While the processes occurring during individual injections of GDI injectors have been investigated by a number of researchers, this paper concentrates on the interactions of multiple injection events. Even though multiple injection strategies are already applied in most GDI engines, the impact of the first injection event on the second injection event has not been analyzed in detail yet. Different optical measurement techniques are used in order to investigate the interaction of the two closely timed injection events, as well as the effect of dwell time and the in-cylinder conditions. The injector investigated is a GDI piezo injector with an outwardly opening needle.
Technical Paper

Near-Nozzle Structure of Diesel Sprays Affected by Internal Geometry of Injector Nozzle: Visualized by Single-Shot X-ray Imaging

2010-04-12
2010-01-0877
By taking advantage of high-intensity and high-brilliance x-ray beams available at the Advanced Photon Source (APS), ultrafast (150 ps) propagation-based phase-enhanced imaging was developed to visualize high-pressure high-speed diesel sprays in the optically dense near-nozzle region. The sub-ns temporal and μm spatial resolution allows us to capture the morphology of the high-speed fuel sprays traveling at 500 m/s with a negligible motion blur. Both quality and quantitative information about the spray feature can be readily obtained. In the experiment, two types of single-hole nozzles have been used, one with a hydroground orifice inlet and the other with a sharp one. Within 3 mm from the nozzle, the sprays from these nozzles behave differently, ranging from laminar flow with surface instability waves to turbulent flow. The sprays are correlated with the nozzle internal geometry, which provides practical information for both nozzle design and supporting numerical simulation models.
Technical Paper

Effects of B20 Fuel and Catalyst Entrance Section Length on the Performance of UREA SCR in a Light-Duty Diesel Engine

2010-04-12
2010-01-1173
The current study focused on the effects B20 fuel (20% soybean-based biodiesel) and SCR entrance shapes on a light-duty, high-speed, 2.8L common-rail 4-cylinder diesel engine, at different exhaust temperatures. The results indicate that B20 has less deNOX efficiency at low temperature than ULSD, and that N₂O emission need to be characterized as well as NH₃ slip. If a mixer and enough mixing length are used, longer divergence section does not improve the deNOX efficiency significantly under the speed ranges tested.
Technical Paper

Impact of Biodiesel Emission Products from a Multi-Cylinder Direct Injection Diesel Engine on Particulate Filter Performance

2009-04-20
2009-01-1184
As diesel emission regulations continue to increase, the use of exhaust aftertreatment systems containing, for example the diesel oxidation catalyst (DOC) and diesel particulate filter (DPF) will become necessary in order to meet these stringent emission requirements. The addition of a DOC and DPF in conjunction with utilizing biodiesel fuels requires extensive research to study the implications that biodiesel blends have on emissions as well as to examine the effect on aftertreatment devices. The proceeding work discusses results from a 2006 VM Motori four-cylinder 2.8L direct injection diesel engine coupled with a diesel oxidation catalyst and catalyzed diesel particulate filter. Tests were done using ultra low sulfur diesel fuel blended with 20% choice white grease biodiesel fuel to evaluate the effects of biodiesel emission products on the performance and effectiveness of the aftertreatment devices and the effect of low temperature combustion modes.
Journal Article

Characterization of Diesel Common Rail Spray Behavior for Single- and Double-hole Nozzles

2008-10-06
2008-01-2424
Double-hole nozzle and multiple injections have the potential for better fuel atomization and mixing in DI engine. In order to evaluate the behavior of the spray for the double-hole nozzles against traditional single-hole ones, high-speed spray visualization was carried out using a streak film camera and a copper vapor laser, and in combination with a long-distance camera when taking microscopic movies. The spray penetration and the cone angle were measured based on the images and compared for variable injection pressures, and for single and split injections, under ambient and elevated chamber pressure conditions. The results showed that the spray of the double-hole nozzle has comparable penetration but smaller cone angle when viewed from the nozzle end, compared to the single-hole nozzle with the same total hole discharge cross-sectional area. For microscopic view, it was observed that the interaction between the dual sprays is very dynamic.
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