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Technical Paper

A Study of Fuel Auto-ignitability on Premixed Compression Ignition Characteristics

2008-04-14
2008-01-0062
It has been clarified that diesel fuel properties have a great effect on the exhaust emissions and fuel consumption of a conventional diesel combustion regime. And as other diesel combustion regimes are applied in order to improve exhaust emissions and fuel consumption, it can be supposed that the fuel properties also have significant effects. The purpose of this study is to propose the optimum diesel fuel properties for a premixed compression ignition (PCI) combustion regime. In this paper, the effect of the auto-ignitability of diesel fuels on exhaust emissions and fuel consumption was evaluated using a heavy-duty single-cylinder test engine. In all experiments, fuels were injected using an electronically controlled, common-rail diesel fuel injector, and most experiments were conducted under high EGR conditions in order to reduce NOx emissions.
Technical Paper

Measurement of Trace Levels of Harmful Substances Emitted from a DME DI Diesel Engine

2005-05-11
2005-01-2202
In this report, trace levels of harmful substances, such as formaldehyde, acetaldehyde, SO2, benzene and so on, emitted from a DME fueled direct injection (DI) compression ignition (CI) engine were measured using a Fourier Transform Infrared (FTIR) emission analyzer. Results showed that the NO portion of NOx emissions with DME exceeded diesel fuel operation levels. DME fueling caused greater amounts of water than with diesel fuel operation. DME fueling was also associated with higher formaldehyde emissions than with diesel fuel operation. However, using an oxidation catalyst, formaldehyde could be decreased to a negligible level.
Technical Paper

Research and Development of a Medium Duty DME Truck

2005-05-11
2005-01-2194
Dimethyl ether (DME) has been attracting notable attention as a clean alternative fuel for diesel engines. The authors developed a medium duty DME truck, and investigated aspects of vehicle performance such as engine power, exhaust characteristics, fuel consumption, noise, in-vehicle systems, and so on. Results indicated that higher engine torque and power could be achieved with DME compared to diesel fuel operation of the base engine at any engine speed. Results also showed that emissions decreased dramatically, to 27% for NOx, 74% for HC, 95% for CO and 94% for PM (Particulate Matter) compared to maximum allowed Japanese 2003 emission regulations. The operating noise of the DME vehicle was slightly lower than the base vehicle with diesel fuel, because the combustion noise with DME was decreased compared to with diesel fuel operation. The DME vehicle was given a public license plate in October 2004, after which running test continued on public roads and on a test course.
Technical Paper

Fuel Characteristics Evaluation of GTL for DI Diesel Engine

2004-03-08
2004-01-0088
In this study, advantages of GTL fueled DI diesel engine were observed, then, some cautionary areas, notably the aptitude for sealing materials, were investigated. Some advantages of using GTL as a diesel engine fuel include reduction of soot emission levels, power output and fuel consumption with GTL to conventional diesel fuel operation is equivalent, super-low sulfur content of GTL and its liquid state at normal temperature and pressure. However, there are some problems with putting GTL fuel on the market, such as lubricity, aptitude for sealing materials, high cetane index and high pour point. It is necessary to use additives to improve GTL's lubricity, and selecting the most appropriate type of lubricity improver is also important. The influence of GTL on the swelling properties of standard rubber materials seem basically the same, but it is necessary to notice on used rubbers.
Technical Paper

NO Emission Characteristics of a CI Engine Fueled with Neat Dimethyl Ether

1999-03-01
1999-01-1116
In this study, the NO emission characteristics of a dimethyl ether fueled compression ignition (CI) engine were studied, and a suitable combustion control concept was developed. A three-zone thermo-chemical model was used to understand the basic NO formation characteristics with dimethyl ether. The experimental study was carried out using a small direct-injection diesel engine. Comparison of the experimental and calculated results showed that the dimethyl ether / air mixing process was relatively slow compared with diesel fuel, which is the main reason for the relatively high NO emissions with dimethyl ether operation, in spite of its lower adiabatic flame temperature. To reduce the high temperature period, turbulence was introduced into the combustion chamber by a high-turbulence combustion system, which reduced NO emissions. It became clear that acceleration of the mixing process is an important factor for NO reduction with dimethyl ether spray combustion.
Technical Paper

Spray and Exhaust Emission Characteristics of a Biodiesel Engine Operating with the Blend of Plant Oil and DME

2002-03-04
2002-01-0864
As an effective method to solve the global warming and the energy crisis, the research has been carried out for the adaptability of plant oil as an alternative fuel for Diesel engine. But there are the problems of engine performance and exhaust emissions owing to the high viscosity and low volatility, when the plant oil is used as a fuel. In order to eliminate these problems, spray characteristics of the DME (Dimethyl ether) blended plant oil has been examined by using the image processing based on the shadowgraph methodology. Results show that the optimum mixing ratio of the blend is about 50:50 (by weight %). Thereafter, experiments have been conducted with a DI Diesel engine using the DME blended plant oil, and compared the exhaust emissions with Diesel, DME and transesterified fuel operation. From the results, it can be concluded that the combustion characteristics of DME blended plant oil are comparable to Diesel fuel.
Technical Paper

DME Fuel Blends for Low-Emission, Direct-Injection Diesel Engines

2000-06-19
2000-01-2004
Based on the knowledge that cavitation in a nozzle enhances the atomization of fuel spray, fuel modification is conducted by blending Dimethyl Ether (DME). Because the boiling point of DME is -24.8°C, it may easily take place during the cavitation in an injection nozzle. Furthermore, there is a soot reduction effect caused by the oxygenated fuels. The oxygen content in the DME is 34.8%, which accelerates soot reduction in the combustion chamber. The experimental results are compared with those of DiMethoxyMethan (Methylal: DMM), a blend of gas-oil. The ignition temperatures of DME and DMM are 235°C and 236°C, the boiling temperatures of DME and DMM are -24.8°C and 42.1°C, and the oxygen contents of DME and DMM are 34.8% and 42.1%, respectively. In addition to the oxygenated fuel, a propane blend of gas-oil was also used as a blended fuel in order to examine the effects of the boiling point and oxygen content of the fuel.
Technical Paper

Methodology of Lubricity Evaluation for DME Fuel based on HFRR

2011-11-08
2011-32-0651
The methodology of lubricity evaluation for DME fuel was established by special modified HFRR (High-Frequency Reciprocating Rig) such as Multi-Pressure/Temperature HFRR (MPT-HFRR). The obtained results were summarized as follows: The HFRR method is adaptable with DME fuel. There is no effect of the test pressure (up to 1.8 MPa) and the test temperature (up to 100°C) of MPT-HFRR on wear scar diameter. The results with MPT-HFRR can be applied at the sliding parts of the injection needle and the fuel supply pump's plungers which are secured lubricity by the boundary lubrication mode mainly and the mixed lubrication mode partially. Using the fatty-acid-based lubricity improver in amounts of approximately 100 ppm, the lubricity of DME, which has a lack of self-lubricity, is ensured as same as the diesel fuel equivalent level. There is a big deviation of measured wear scar diameter when the LI concentration is not enough.
Technical Paper

Numerical Analysis of Carbon Monoxide Formation in DME Combustion

2011-11-08
2011-32-0632
Dimethyl ether (DME) is an oxygenated fuel with the molecular formula CH₃OCH₃, economically produced from various energy sources, such as natural gas, coal and biomass. It has gained prominence as a substitute for diesel fuel in Japan and in other Asian countries, from the viewpoint of both energy diversification and environmental protection. The greatest advantage of DME is that it emits practically no particulate matter when used in compression ignition (CI) engine. However, one of the drawbacks of DME CI engine is the increase carbon monoxide (CO) emission in high-load and high exhaust gas circulation (EGR) regime. In this study, we have investigated the CO formation characteristics of DME CI combustion based on chemical kinetics.
Technical Paper

Development of Retrofit DME Diesel Engine Operating with Rotary Distributor Fuel Injection Pump

2003-03-03
2003-01-0758
In order to reduce environmental disruption due to exhaust PM and NOx emissions from diesel engines of dimethyl ether (DME) has been proposed the use for the next generation vehicles, because the discharge of the atmospheric pollutants is less. In this study, DME is used to fuel a retrofit type diesel engine, and operational tests were carried out using a rotary distributor fuel injection pump. In this experiment, comparison and examination of the effects of fuel injection pressure, nozzle hole diameter, and injection timing. When using DME as an alternative fuel, the fuel temperature affects engine operation. And diameter of the injector nozzle hole and larger injection quantity is regarded as factors affecting the improvement in engine performance. In addition, for understanding the DME spray in the cylinder, DME was sprayed in a constant volume chamber where atmospheric temperature and pressure increased simultaneously, and the result is compared and examined with diesel fuel.
Technical Paper

Spectroscopic Analysis of Combustion Flame Fueled with Dimethyl Ether (DME)

2003-05-19
2003-01-1797
To better understand the combustion characteristics of DME, emission intensities of DME combustion radicals from a pre-mixed burner flame were measured by a spectroscope and photomultiplier, Results were compared to other fuels, such as methane and butane. Large peaks in the band spectra from pre-mixed and diffusion DME flames were found near 310 nm, 430 nm, and 515 nm, arising from OH, CH and C2, respectively. The DME emission intensities decreased with increasing the equivalence ratio in this study. Notably, the relative decrease in the C2 band spectra peak was greater than that of the OH band. Comparing the pre-mixed DME and butane flames, the butane band spectra peaks were similar in shape, but much stronger than those for DME. However, it was remarkable that CH and C2 band spectra peaks decreased only slightly with increase in equivalence ratio compared to the DME case.
Technical Paper

Experimental Study of CI Natural-Gas/DME Homogeneous Charge Engine

2000-03-06
2000-01-0329
In this study, a homogeneous mixture of natural-gas and air was used in a compression ignition engine to reduce NOx emissions and improve thermal efficiency. In order to control ignition timing and combustion, a small amount of DME was mixed with the natural-gas. Engine performance and the exhaust characteristics were investigated experimentally. Results show the following: the engine can run over quite a large load range if a certain amount of DME is added into natural-gas. By optimizing the proportion of DME to natural-gas, NOx emissions can be lowered to near zero levels if the mixture is lean enough. Thermal efficiency is higher than that obtained with normal diesel fuel operation.
Journal Article

Investigation of Mechanism for Formation of EGR Deposit by in situ ATR-FTIR Spectrometer and SEM

2016-10-17
2016-01-2351
Exhaust gas recirculation (EGR) is widely used in diesel engines to reduce nitrogen oxide (NOx) emissions. However, a lacquer is formed on the EGR valve or EGR cooler due to particulate matter and other components present in diesel exhaust, causing serious problems. In this study, the mechanism of lacquer deposition is investigated using attenuated total reflection Fourier transform infrared spectrometry (ATR-FTIR) and scanning electron microscopy (SEM). Deposition of temperature-dependent lacquers was evaluated by varying the temperature of a diamond prism between 80 and 120 °C in an ATR-FTIR spectrometer integrated into a custom-built sample line, which branched off from the exhaust pipe of a diesel engine. Lacquers were deposited on the diamond prism at 100 °C or less, while no lacquer was deposited at 120 °C. Time-dependent ATR-FTIR spectra were obtained for approximately 2 h from the beginning of the experiment.
Technical Paper

Engine Performance and Emission Characteristics of DME Diesel Engine With Inline Injection Pump Developed for DME

2004-06-08
2004-01-1863
The engine performance and exhaust characteristics of the DME-powered diesel engine with an injection system developed for DME were investigated. The injection pump is an inline type that can inject double amount of DME fuel compared to the base injection pump because the calorific value of DME is about half lower than that of diesel fuel. The effect of injection timing on engine performances such as thermal efficiency, engine torque, and exhaust characteristics were investigated. Maximum torque and power with DME could be achieved the same or greater level compared to diesel fuel operation. Considering over all engine performances, the best dynamic injection timings without EGR were -3, -3, -6 and -9 deg. ATDC in 1120, 1680, 2240 and 2800 rpm engine speeds respectively in this experiment.
Technical Paper

Spectroscopic Analysis of Combustion in the DME Diesel Engine

2004-03-08
2004-01-0089
For better understanding of the combustion characteristics in a direct injection dimethyl ether (DME) engine, the chemiluminescences of a burner flame and in-cylinder flame were analyzed using the spectroscopic method. The emission intensities of chemiluminescences were measured by a photomultiplier after passing through a monochrome-spectrometer. For the burner flame, line spectra were found nearby the wave length of 310 nm, 430 nm and 515 nm, arising from OH, CH and C2 radicals, respectively. For the in-cylinder flame, a strong continuous spectrum was found from 340 nm wave length to 550 nm. Line spectra were also detected nearby 310 nm, 395 nm and 430 nm, arising from OH, HCHO, and C2 radicals, respectively, partially overlapping with the continuous spectrum. Of these line spectra, 310 nm of OH radical did not overlapped with the continuous spectrum.
Technical Paper

CFD Study of an LPG DI SI Engine for Heavy Duty Vehicles

2002-05-06
2002-01-1648
This work aimed to develop an LPG fueled direct injection SI engine, especially in order to improve the exhaust emission quality while maintaining high thermal efficiency comparable to a conventional engine. In-cylinder direct injection engines developed recently worldwide utilizes the stratified charge formation technique at low load, whereas at high load, a close-to-homogeneous charge is formed. Thus, compared to a conventional port injection engine, a significant improvement of fuel consumption and power can be achieved. To implement such a combustion strategy, the stratification of mixture charge is very important, and an understanding of its combustion process is also inevitably necessary. In this work, a numerical simulation was performed using a CFD code (KIVA-3), where the shape of a combustion chamber, swirl intensity, injection timing and duration, etc. were varied and their effects on the mixture formation and combustion process were investigated.
Technical Paper

Simultaneous Observation of Droplets and Evaporated State of Liquid Butane and DME at Low Injection Pressure

2002-05-06
2002-01-1627
Alternative fuels such as butane and DME have different properties including high vapor pressure, low viscosity, and low surface tension, compared to other conventional fuels. These properties may lead to different atomization characteristics such as liquid core breakup, droplet size distribution, and evaporation process. To investigate these effects, a method based on shadowgraph technique to take spray images for droplets and surrounding gas was tested and evaluated. Experiments were performed at low injection pressure for early stage direct injection. It could be concluded from the results that the proposed method could be used to investigate the structure of evaporating spray, and the vapor layer around the spray core could be correlated to the turbulent mixing length for both of butane and DME sprays by observing vapor and spray core.
Technical Paper

Atomization Characteristics for Various Ambient Pressure of Dimethyl Ether (DME)

2002-05-06
2002-01-1711
Recently, dimethyl ether (DME) has been attracting much attention as a clean alternative fuel, since the thermal efficiency of DME powered diesel engine is comparable to diesel fuel operation and soot free combustion can be achieved. In this experiment, the effect of ambient pressure on DME spray was investigated with observation of droplet size such as Sauter mean diameter (SMD) by the shadowgraph and image processing method. The higher ambient pressure obstructs the growth of DME spray, therefore faster breakup was occurred, and liquid column was thicker with increasing the ambient pressure. Then engine performances and exhaust emissions characteristics of DME diesel engine were investigated with various compression ratios. The minimum compression ratio for the easy start and stable operation was obtained at compression ratio of about 12.
Technical Paper

Chemiluminescence Analysis from In-Cylinder Combustion of a DME-Fueled DI Diesel Engine

2003-10-27
2003-01-3192
To date, the DME combustion mechanism has been investigated by in-cylinder gas sampling, numerical calculations and observation of combustion radicals. It has been possible to quantify the emission intensities of in-cylinder combustion using a monochromator, and to observe the emitting species as images by using band-pass filters. However, the complete band images were not observed since the broadband (thermal) intensity may be stronger than band spectra intensities. Emission intensities of DME combustion radicals from a pre-mixed burner flame have been measured using a spectroscope and photomultiplier. Results were compared to other fuels, such as n-butane and methane, then, in this study, to better understand the combustion characteristics of DME, emission intensities near CH bands of an actual DI diesel engine fueled with DME were measured, and band spectra emitted from the engine were defined. Near TDC, emission intensities did not vary with wavelength.
Technical Paper

Effects of Fuel Injection Conditions on Driving Performance of a DME Diesel Vehicle

2003-10-27
2003-01-3193
Since dimethyl ether (DME) is a synthetic fuel, it is possible to make it from natural gas, coal and biomass. It is a low-emission, oxygenated fuel, which does not generate soot in the exhaust. Therefore, it has recently been identified as a possible replacement for diesel fuel. In Japan, the new short-term emissions regulations will be enforced beginning in 2003, and the long-term emissions regulations are scheduled to be enforced in 2005. In order to meet these more stringent emissions regulations, existing diesel engines would not be as widely used in the near future as they currently are. This will thus bring about a more widespread use of DME engines due to their low emissions potential. Moreover, when the modification of existing diesel engines into DME engines is available at a moderate cost, the wider use of DME engines can be expected. This study targeted development and application of DME engine technology for diesel engine retrofit, in a used diesel vehicle.
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