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Technical Paper

Pathway to 50% Brake Thermal Efficiency Using Gasoline Direct Injection Compression Ignition

2019-04-02
2019-01-1154
Continued improvement in the combustion process of internal combustion engines is necessary to reduce fuel consumption, CO2 emissions, and criteria emissions for automotive transportation around the world. In this paper, test results for the Gen3X Gasoline Direct Injection Compression Ignition (GDCI) engine are presented. The engine is a 2.2L, four-cylinder, double overhead cam engine with compression ratio ~17. It features a “wetless” combustion system with a high-pressure direct injection fuel system. At low load, exhaust rebreathing and increased intake air temperature were used to promote autoignition and elevate exhaust temperatures to maintain high catalyst conversion efficiency. For medium-to-high loads, a new GDCI-diffusion combustion strategy was combined with advanced single-stage turbocharging to produce excellent low-end torque and power. Time-to-torque (TT) simulations indicated 90% load response in less than 1.5 seconds without a supercharger.
Technical Paper

Advancement of GDCI Engine Technology for US 2025 CAFE and Tier 3 Emissions

2018-04-03
2018-01-0901
The automotive industry is facing tremendous challenges to improve fuel economy and emissions of the internal combustion engine. In the US, 2025 standards for fuel economy and CO2 emissions are extremely stringent. Simultaneously, vehicles must comply with new US Tier 3 emissions standards. In all market segments, there is a need for very clean and efficient engines operating on gasoline fuels. Gasoline Direct Injection Compression Ignition (GDCI) has been under development for several years and significant progress has been realized. As part of two US DOE programs, Delphi has developed a third generation GDCI engine that utilizes partially premixed compression ignition. The engine features an innovative “wetless”, low-temperature, combustion system with the latest high-pressure GDi injection system. The system was developed using extensive simulation and engine testing.
Technical Paper

Numerical Investigation of Natural Gas-Diesel Dual Fuel Engine with End Gas Ignition

2018-04-03
2018-01-0199
The present study helps to understand the local combustion characteristics of PREmixed Mixture Ignition in the End-gas Region (PREMIER) combustion mode while using increasing amount of natural gas as a diesel substitute in conventional CI engine. In order to reduce NOx emission and diesel fuel consumption micro-pilot diesel injection in premixed natural gas-air mixture is a promising technique. New strategy has been employed to simulate dual fuel combustion which uses well established combustion models. Main focus of the simulation is at detection of an end gas ignition, and creating an unified modeling approach for dual fuel combustion. In this study G-equation flame propagation model is used with detailed chemistry in order to detect end-gas ignition in overall low temperature combustion. This combustion simulation model is validated using comparison with experimental data for dual fuel engine.
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.
Journal Article

Second Generation GDCI Multi-Cylinder Engine for High Fuel Efficiency and US Tier 3 Emissions

2016-04-05
2016-01-0760
The second generation 1.8L Gasoline Direct Injection Compression Ignition (GDCI) engine was built and tested using RON91 gasoline. The engine is intended to meet stringent US Tier 3 emissions standards with diesel-like fuel efficiency. The engine utilizes a fulltime, partially premixed combustion process without combustion mode switching. The second generation engine features a pentroof combustion chamber, 400 bar central-mounted injector, 15:1 compression ratio, and low swirl and squish. Improvements were made to all engine subsystems including fuel injection, valve train, thermal management, piston and ring pack, lubrication, EGR, boost, and aftertreatment. Low firing friction was a major engine design objective. Preliminary test results indicated good improvement in brake specific fuel consumption (BSFC) over the first generation GDCI engines, while meeting targets for engine out emissions, combustion noise and stability.
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.
Journal Article

GDCI Multi-Cylinder Engine for High Fuel Efficiency and Low Emissions

2015-04-14
2015-01-0834
A 1.8L Gasoline Direct Injection Compression Ignition (GDCI) engine was tested over a wide range of engine speeds and loads using RON91 gasoline. The engine was operated with a new partially premixed combustion process without combustion mode switching. Injection parameters were used to control mixture stratification and combustion phasing using a multiple-late injection strategy with GDi-like injection pressures. At idle and low loads, rebreathing of hot exhaust gases provided stable compression ignition with very low engine-out NOx and PM emissions. Rebreathing enabled reduced boost pressure, while increasing exhaust temperatures greatly. Hydrocarbon and carbon monoxide emissions after the oxidation catalyst were very low. Brake specific fuel consumption (BSFC) of 267 g/kWh was measured at the 2000 rpm-2bar BMEP global test point.
Journal Article

Development of a Gasoline Direct Injection Compression Ignition (GDCI) Engine

2014-04-01
2014-01-1300
In previous work, Gasoline Direct Injection Compression Ignition (GDCI) has demonstrated good potential for high fuel efficiency, low NOx, and low PM over the speed-load range using RON91 gasoline. In the current work, a four-cylinder, 1.8L engine was designed and built based on extensive simulations and single-cylinder engine tests. The engine features a pent roof combustion chamber, central-mounted injector, 15:1 compression ratio, and zero swirl and squish. A new piston was developed and matched with the injection system. The fuel injection, valvetrain, and boost systems were key technology enablers. Engine dynamometer tests were conducted at idle, part-load, and full-load operating conditions. For all operating conditions, the engine was operated with partially premixed compression ignition without mode switching or diffusion controlled combustion.
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.
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.
Technical Paper

Investigation of Ignition Energy with Visualization on a Spark Ignited Engine powered by CNG

2014-04-01
2014-01-1331
The need for using alternative fuel sources continues to grow as industry looks towards enhancing energy security and lowering emissions levels. In order to capture the potential of these megatrends, this study focuses on the relationship between ignition energy, thermal efficiency, and combustion stability of a 0.5 L single cylinder engine powered by compressed natural gas (CNG) at steady state operation. The goal of the experiment was to increase ignition energy at fixed lambda values to look for gains in thermal efficiency. Secondly, a lambda sweep was performed with criteria of maintaining a 4% COVIMEP by increasing the ignition energy until an appropriate threshold for stable combustion was found. The engine performance was measured with a combustion analysis system (CAS), to understand the effects of thermal efficiency and combustion stability (COVIMEP). Emissions of the engine were measured with an FTIR.
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

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

Engine Efficiency Improvements Enabled by Ethanol Fuel Blends in a GDi VVA Flex Fuel Engine

2011-04-12
2011-01-0900
Advances in engine technology including Gasoline Direct injection (GDi), Dual Independent Cam Phasing (DICP), advanced valvetrain and boosting have allowed the simultaneous reductions of fuel consumption and emissions with increased engine power density. The utilization of fuels containing ethanol provides additional improvements in power density and potential for lower emissions due to the high octane rating and evaporative cooling of ethanol in the fuel. In this paper results are presented from a flexible fuel engine capable of operating with blends from E0-E85. The increased geometric compression ratio, (from 9.2 to 11.85) can be reduced to a lower effective compression ratio using advanced valvetrain operating on an Early Intake Valve Closing (EIVC) or Late Intake Valve Closing (LIVC) strategy. DICP with a high authority intake phaser is used to enable compression ratio management.
Technical Paper

Charge Motion Benefits of Valve Deactivation to Reduce Fuel Consumption and Emissions in a GDi, VVA Engine

2011-04-12
2011-01-1221
Requirements for reduced fuel consumption with simultaneous reductions in regulated emissions require more efficient operation of Spark Ignited (SI) engines. An advanced valvetrain coupled with Gasoline Direct injection (GDi) provide an opportunity to simultaneously reduce fuel consumption and emissions. Work on a flex fuel GDi engine has identified significant potential to reduce throttling by using Early Intake Valve Closing (EIVC) and Late Intake Valve Closing (LIVC) strategies to control knock and load. High loads were problematic when operating on gasoline for particulate emissions, and low loads were not able to fully minimize throttling due to poor charge motion for the EIVC strategy. The use of valve deactivation was successful at reducing high load particulate emissions without a significant airflow penalty below 3000 RPM. Valve deactivation did increase the knocking tendency for knock limited fuels, due to increased heat transfer that increased charge temperature.
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

A Simulation Method to Guide DISI Engine Redesign for Increased Efficiency using Alcohol Fuel Blends

2010-04-12
2010-01-1203
A turbocharged 2.0L 4-cylinder direct injection spark ignition (DISI) engine designed for use with gasoline is simulated using one dimensional engine simulation. Engine design modifications - increased compression ratio, 2-step valve train with dual independent cam phasing and fuel injection timing - are considered in an effort to improve fuel economy with gasoline and take advantage of properties of ethanol fuel blends (up to E85). This paper discusses a methodology to use the simulation to quantitatively evaluate the design modification effects on fuel economy. Fuel consumption predictions from the simulation for each design are evaluated. The goal is to identify the best design with the constraints of hardware physical limitations, engine residual tolerance and knock tolerance. The result yields a specification for a 2-step valve train design and phasing requirements that can improve fuel economy for each compression ratio design.
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.
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