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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.
Journal Article

Application of High-Speed PIV Diagnostics for Simultaneous Investigation of Flow Field and Spark Ignited Flame inside an Optical SI Engine

2017-03-28
2017-01-0656
High speed, time resolved Particle Image Velocimetry (PIV) diagnostics was applied to an optical SI engine to study the interactions between in-cylinder flow field and flame development. Optimisation and certain adaptations have been made to the diagnostic setup to enable time-resolved, simultaneous measurements of both PIV data and flame tomography imaging from the same original captured image set. In this particular study, interactions between flow and flame during lean-burn operating conditions at various tumble strength have been investigated and compared to a standard stoichiometric operation. Diagnostics were performed for both the vertical plane (x-y) and the horizontal plane (r-⊖) of the combustion chamber with a particular focus in the pent-roof area. Some major differences in the tumble flow-field prior to ignition has been observed between the lean and stoichiometric conditions.
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

Control Strategy Development of Natural Gas/Diesel Dual Fuel Engine for Heavy Duty Vehicle

2016-04-05
2016-01-0628
An applicable and comprehensive control strategy of a natural gas/diesel dual fuel engine is presented in this paper. The dual fuel engine is converted from a conventional mechanical pump, turbo charged, heavy duty diesel engine. In the dual fuel mode, the pedal position is explained as demanded total fuel quantity, the quantity of pilot diesel and natural gas are calculated in order to provide the equal energy with the original diesel engine at the same operation condition, the proportion of the natural gas is primarily determined by the load rate and the speed of the engine. When the engine is working under light or moderate load, the intake air is throttled in order to improve the brake mean effective pressure and reduce the hydrocarbon emissions of the dual fuel engine, according to target excess air ratio and the quantities of the two fuels, the desired air mass per cycle can be obtained.
Technical Paper

Combustion Diagnostics Using Time-Series Analysis of Radical Emissions in a Practical Engine

2015-11-17
2015-32-0748
The objective of this study is to investigate the initial flame propagation characteristics of turbulent flame in an engine cylinder through time-series analysis of radical emissions. A spark plug with optical fiber was developed in this study. The plug sensor is M12 type that makes it possible to mount in practical engine. The spark plug sensor can detect radical emissions in time-resolved spectra through time-series spectroscopic measurement. In this spectra, some kinds of radical emissions such as OH*(306nm), CH*(431nm) and C2*(517nm) based on principle of chemiluminescence are observed. In this study, the spark plug sensor was applied to both compression-expansion machine (CEM) and practical engine. As a result of CEM with bottom viewed high-speed camera, three kinds of spectra could be detected.
Technical Paper

Effect of Hydrogen Concentration on Engine Performance, Exhaust Emissions and Operation Range of PREMIER Combustion in a Dual Fuel Gas Engine Using Methane-Hydrogen Mixtures

2015-09-01
2015-01-1792
A single cylinder, supercharged dual fuel gas engine with micro-pilot fuel injection is operated using methane only and methane-hydrogen mixtures. Methane only experiments were performed at various equivalence ratios and equivalence ratio of 0.56 is decided as the optimum operating condition based on engine performance, exhaust emissions and operation stability. Methane-hydrogen experiments were performed at equivalence ratio of 0.56 and 2.6 kJ/cycle energy supply rate. Results show that indicated mean effective pressure is maintained regardless of hydrogen content of the gaseous fuel while thermal efficiency is improved and presence of hydrogen reduces cyclic variations. Increasing the fraction of hydrogen in the fuel mixture replaces hydrocarbon fuels and reduces carbon monoxide and hydrocarbon emissions.
Technical Paper

Effect of Bio-Gas Contents on SI Combustion for a Co-Generation Engine

2015-09-01
2015-01-1946
Bio-gas as an internal combustion (I.C.) engine fuel has many advantages such as cheaper fuel cost, low emission levels and especially the neutral recirculation loop of carbon dioxide, which is one of the principal factors in global warming. In this study, positive potentialities of bio-gas were investigated using a micro co-generation engine. The mixing ratio of methane (CH4) and carbon dioxide (CO2) was changed to simulate various types of bio-gases. Intake air and fuel flow rates were controlled to change the equivalence ratio. The engine load condition could be changed with the electric output power used. Base on the result, the higher CO2 content rate slowed down the engine speed in the same load condition and the combustion speed generally decreased under the same load condition with maintaining the engine speed. However thermal efficiency increased with lean burn conditions and NOX emission decreased with higher CO2 mixing rates.
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

Mixing Process of Direct Injection Hydrogen Jet in a Constant Volume Vessel by Using Spark-Induced Breakdown Spectroscopy

2013-10-14
2013-01-2526
Hydrogen spark-ignition (SI) engines based on direct-injection (DI) have been investigated because of their potential for high thermal efficiency and solving the problems related to knocking, backfiring, and pre-ignition. Wide range flammability limits in hydrogen engine enable smooth engine operation for a very lean mixture with low NOX. However, a too lean mixture may increase ignition delay and causes severe cyclic variations. There is a possibility that the turbulence occurred during injection of fuel surround the spark plug in the combustion chamber is major contributor to this phenomenon. To overcome this problem, a better understanding of the spark discharge and spark ignition during transient hydrogen jet is necessary. Therefore, it is very important to study an effect of local equivalence ratio and behavior of spark discharge in SI engine. This paper describes a mixing process of hydrogen jet using spark-induced breakdown spectroscopy (SIBS) in a constant volume vessel.
Journal Article

Effect of Hot Exhaust Gas Recirculation on the Combustion Characteristics and Particles Emissions of a Pilot-Ignited Natural Gas Engine

2013-04-08
2013-01-1341
Natural gas has become an attractive alternative for diesel fuel due to its higher octane number, richer reserves and lower price. It has been utilized in compression ignition engines to obtain a higher thermal efficiency compared with spark ignition engines. However, its relatively higher auto-ignition temperature increases the difficulty of compression-ignition based on present hardware devices. One optimal ignition method is that a very small quantity of diesel fuel as the only ignition resource pilot-ignites the lean natural gas-air mixture. This micro diesel pilot-ignited natural gas premixed charge compression ignition (DPING-PCCI) combustion strategy is easy to implement without major hardware modifications, and can significantly reduce the NOx and particle mass emissions from diesel engines. Although the DPING-PCCI has so many advantages, it suffers from poor engine stability and high ultrafine particles emissions at part loads.
Technical Paper

Experimental Investigation of Cycle-by-Cycle Variations in a Natural Gas/Diesel Dual Fuel Engine with EGR

2013-04-08
2013-01-0853
This study presents a detailed experimental investigation on the cycle-by-cycle variations in a natural gas/diesel dual fuel engine with EGR. The experiment used a single-cylinder, four-stroke, water-cooled, DI diesel engine. The EGR ratio, diesel injection timing and pilot diesel quantity were varied respectively while all the other parameters were held constant. The parameters of cylinder pressure are used to investigate the cyclic variations. The results show that the cylinder peak pressure, the maximum rate of pressure rise and the indicated mean effective pressure decrease. COVimep increases to 18.9% with 25% EGR ratio. The interdependency between the pressure parameters and their corresponding crank angles become weak with the increasing EGR ratio. The increasing EGR ratio increases the ignition delay. The cylinder peak pressure and the maximum rate of pressure rise increase dramatically with the advance of the pilot diesel injection timing.
Journal Article

High-Pressure Hydrogen Jet and Combustion Characteristics in a Direct-Injection Hydrogen Engine

2011-08-30
2011-01-2003
Hydrogen spark-ignition (SI) engines based on direct-injection (DI) promise significant advantages in terms of thermal efficiency and power output, as well as a means of overcoming problems related to knocking, backfiring, and pre-ignition. In a DI hydrogen engine, the fuel/air mixture is formed by injecting a jet of hydrogen into the air inside the combustion chamber. An Ar-ion laser beam was used as a light source to visualize the hydrogen jet in a constant-volume chamber. This allowed us to study the structure of the jet in addition to other physical processes resulting from hydrogen gas injection. Combustion experiments were conducted in a single-cylinder SI optical research engine equipped with a DI system to detect the early kernel growth assisted by the spark, as well as flame propagation. Various equivalence ratios and fuel injection timings were analyzed to identify the effects on combustion.
Technical Paper

Extending the Lean Stability Limits of Gasoline Using a Microwave-Assisted Spark Plug

2011-04-12
2011-01-0663
The extension of the lean stability limits of gasoline-air mixtures using a microwave-assisted spark plug has been investigated. Experiments are conducted on a 1200 RPM single-cylinder Waukesha Cooperative Fuel Research (CFR) engine at two compression ratios: 7:1 and 9:1; and four different levels of microwave energy input per cycle (prior to accounting for transmission losses): 0 mJ (spark only), 130 mJ, 900 mJ, and 1640 mJ. For various microwave energy inputs, the effects upon stability limits are explored by gradually moving from stoichiometric conditions to increasingly lean mixtures. The coefficient of variation (COVIMEP) of the indicated mean effective pressure (IMEP) is used as an indication of the stability limits. Specific characteristics of microwave-assisted ignition are identified. Microwave enhancement extends stability limits into increasingly lean regions, but slow and partial burning at the leanest mixtures curb efficiency gains.
Technical Paper

Mixture Formation Process in a Spark-Ignition Engine with Ethanol Blended Gasoline

2009-06-15
2009-01-1957
In this study, fuel concentration measurements in a spark-ignition (SI) engine with ethanol blended gasoline were carried out using an optical sensor installed in the spark plug with laser infrared absorption technique. The spark plug sensor for in-situ fuel concentration measurement was applied to a port injected SI engine. The molar absorption coefficients of ethanol blended gasoline were determined for various pressures and temperatures in advance using a constant volume vessel with electric heating system. Ethanol blended gasoline with high volumetric ratios shows lower molar absorption coefficients due to lower molar absorption coefficients of ethanol. The molar absorption coefficients of ethanol blended gasoline can be estimated by considering the molar fraction of each component.
Technical Paper

Effect of EGR on Combustion and Exhaust Emissions in Supercharged Dual-Fuel Natural Gas Engine Ignited with Diesel Fuel

2009-06-15
2009-01-1832
The combustion and exhaust emissions characteristics of a supercharged dual-fuel natural gas engine with a single cylinder were analyzed. We focused on EGR (Exhaust Gas Recirculation) to achieve higher thermal efficiency and lower exhaust emissions. The combustion of diesel fuel (gas oil) as ignition sources was visualized using a high-speed video camera from the bottom of a quartz piston. The luminous intensity and flame decreased as the EGR rate increased. Furthermore, the ignition delay became longer due to the EGR. Characteristics of the combustion and exhaust emissions were investigated with changing EGR rates under supercharged conditions. The indicated mean effective pressure and thermal efficiency decreased with increasing EGR rate. In addition, NOx emissions decreased due to the EGR. In this study two-stage combustion was observed.
Technical Paper

Gas Temperature Measurement in a DME-HCCI Engine using Heterodyne Interferometry with Spark-Plug-in Fiber-Optic Sensor

2007-07-23
2007-01-1848
Non-intrusive measurement of transient unburned gas temperatures was developed with a fiber-optic heterodyne interferometry system. Using the value of the Gladstone-Dale constant for DME gas and combustion pressure we can calculate the in-cylinder temperature inside unburned and burned region. In this experimental study, it was performed to set up a fiber-optic heterodyne interferometry technique to measure the temperature before and behind the combustion region in a DME-HCCI engine. At first, measured temperature was almost the same as the temperature history assuming that the process that changes of the unburned and the burned are polytropic. In addition, we measured the temperature after combustion which of condition was burned gas with DME-HCCI combustion. The developed heterodyne interferometry used the spark-plug-in fiber-optic sensor has a good feasibility to measure the unburned and burned temperature history.
Technical Paper

In-Situ Fuel Concentration Measurement Near Spark Plug by 3.392 μm Infrared Absorption Method-Application to a Port Injected Lean-Burn Engine

2004-03-08
2004-01-1353
In this study, a spark plug sensor for in-situ fuel concentration measurement was applied to a port injected lean-burn engine. Laser infrared absorption method was employed and a 3.392 μm He-Ne laser that coincides with the absorption line of hydrocarbons was used as a light source. In this engine, the secondary valve lift height of intake system was controlled to obtain appropriate swirl and tumble flow in order to achieve lean-burn with the characteristics of intake flow. For such in-cylinder stratified mixture distribution, the fuel concentration near the spark plug is very important factor that affects the combustion characteristics. Therefore, the mixture formation process near the spark plug was investigated with changing fuel injection timing. Under the intake stroke, the timing that fuel passed through near the spark plug depended largely on the fuel injection timing.
Technical Paper

Homogeneous Charge Compression Ignition Combustion with Dimethyl Ether - Spectrum Analysis of Chemiluminescence

2003-05-19
2003-01-1828
Homogeneous Charge Compression Ignition (HCCI) combustion with dimethyl ether has been carried out in a single cylinder engine with a transparent piston. The engine was operated at 800 rpm with a wide-open throttle. The intake-premixed mixture was preheated with an electric heater to promote auto-ignition. HCCI combustion with dimethyl ether indicates multi-stage heat releases. Investigations were conducted with visualization of combustion in the cylinder and detailed and temporal spectroscopic measurements using spectrometer. In order to understand reaction mechanism of auto-ignition and combustion mechanism in HCCI engine, spectrum analysis of chemiluminescence was carried out.
Technical Paper

Effects of EGR and Early Injection of Diesel Fuel on Combustion Characteristics and Exhaust Emissions in a Methane Dual Fuel Engine

2002-10-21
2002-01-2723
A dual fuel engine fueled with methane from an inlet port and ignited with diesel fuel was prepared. This study focuses on the effects of early injection and exhaust gas recirculation (EGR) on the characteristics of combustion and exhaust emissions. The injection timing was changed between TDC and 50 degrees before the TDC. In the early injection timing, smoke was never seen and hydrocarbons were smaller compared with those at the normal injection timing. However, the combustion becomes too early to obtain an appropriate torque when the equivalence ratio increases. Then, moderate EGR was very effective to force the combustion to retard with lower NOx, higher thermal efficiency and almost the same hydrocarbons and carbon monoxide. The engine operated even under the condition of stoichiometric mixture.
Technical Paper

Hydrogen Combustion and Exhaust Emissions Ignited with Diesel Oil in a Dual Fuel Engine

2001-09-24
2001-01-3503
Hydrogen is expected to be one of the most prominent fuels in the near future for solving greenhouse problem, protecting environment and saving petroleum. In this study, a dual fuel engine of hydrogen and diesel oil was investigated. Hydrogen was inducted in a intake port with air and diesel oil was injected into the cylinder. The injection timing was changed over extremely wide range. When the injection timing of diesel fuel into the cylinder is advanced, the diesel oil is well mixed with hydrogen-air mixture and the initial combustion becomes mild. NOx emissions decrease because of lean premixed combustion without the region of high temperature of burned gas. When hydrogen is mixed with inlet air, emissions of HC, CO and CO2 decrease without exhausting smoke while brake thermal efficiency is slightly smaller than that in ordinary diesel combustion.
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