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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

Effects of Particle Size Distribution on Soot Particle Measurement by Transmissive Light Extinction Method

1986-09-01
861234
This paper presents the result of a theoretical study on the effects of particle size distribution on the soot particle measurement method. The principal equations are rear-ranged into a concise form, and a wide variation of size distribution functions are introduced to calculate the effects. It was found that the mean extinction coefficient is very weakly dependent on the shape of size distribution functions and can be approximated to that for the Sauter mean diameter with insignificant error. The volumetric density of soot particles can be obtained by light transmittance measurement on a single wavelength, and this is affected only by the estimated value for the Sauter mean diameter. The error due to the estimation is under 5%. On the other hand, it was found that the light transmittance measurement is insufficient to obtain size distribution or the Sauter mean diameter of soot particles.
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

A Study of PM Emission Characteristics of Diesel Vehicle Fueled with GTL

2007-01-23
2007-01-0028
In this study, diesel exhaust emission characteristics were investigated as GTL (Gas To Liquid) fuel was applied to a heavy-duty diesel truck which had been developed to match a Japanese new long-term exhaust emission regulation (NOx < 2.0 g/kWh, PM < 0.027 g/kWh). The results in this study show that although the test vehicle has advanced technologies (e.g. high pressure fuel injection, oxidation catalyst, and urea-SCR aftertreatment system, etc.) which are applied to reduce diesel emissions, the neat GTL fuel has a great advantage to reduce particulate matter emissions and poly aromatic hydrocarbons. And regarding nano-size PM emissions, nuclei mode particles emitted during idling are significantly decreased by using the GTL fuel.
Technical Paper

Dual-Fuel Diesel Engine Using Butane

1992-02-01
920690
The authors tried to use LP gas, mainly butane, as the main fuel of diesel engines to reduce soot and to maintain high thermal efficiency. LP gas was injected in the direction of the intake valve directly as a spray to prevent knocking and to preserve high charging efficiency. The newly developed electronic fuel injection provided accurate fuel control and injection timing. As a result, the dual-fuel operation produced high thermal efficiency almost identical to that of diesel engines. Soot in engine exhaust was almost negligible. Three quarters of maximum output was obtained with butane, and only small amount of gas oil for idling, in spite of an high compression ratio of 17 for gas engines. Increasing the proportion of gas oil resulted in maximum output from a diesel engine and almost no soot output.
Technical Paper

The Dependence of Carbon/Hydrogen Ratio on Soot Particle Size

1992-02-01
920689
This paper deals with the process regarding how dehydrogenation of soot particles takes place. The measured carbon/hydrogen ratios plotted against mean-diameter of soots fall on a straight line passing through the origin. It is shown that in the course of soot particle growth CM ratio increases linearly with the particle diameter: D. This is an indication of the fact that the number of carbon grows in proportion to D3, whereas that of hydrogen is proportional to D2. It is there by concluded that hydrogen sit only on surface of soot particles.
Technical Paper

Performance and Emissions of an LPG Lean-Burn Engine for Heavy Duty Vehicles

1999-05-03
1999-01-1513
Performance and emissions of an LPG lean burn engine for heavy duty vehicles were measured. The piston cavity, swirl ratio, propane - butane fuel ratio, and EGR were varied to investigate their effects on combustion, and thus engine performance. Three piston cavities were tested: a circular flat-bottomed cavity with sloped walls (called the “bathtub” cavity), a round bottomed cavity (called the “dog dish” cavity), and a special high-turbulence cavity (called the “nebula” cavity). Compared to the bathtub and dog dish cavities, the nebula type cavity showed the best performance in terms of cyclic variation and combustion duration. It was capable of maintaining leaner combustion, thus resulting in the lowest NOx emissions. High swirl improved combustion by achieving a high thermal efficiency and low NOx emissions. In general, as the propane composition increased, cyclic variation fell, NOx emissions increased, and thermal efficiency was improved.
Technical Paper

Effects of Initial In-Cylinder Flow Field on Mixture Formation in a Premixed Compression Ignition Engine

2000-03-06
2000-01-0331
To find more effective lean mixture preparation methods for smokeless and low NOx combustion, a numerical study of the effects of in-cylinder flow field before injection on mixture formation in a premixed compression ignition engine was conducted. Premixed compression ignition combustion is a very attractive method to reduce both NOx and soot emissions, but it still has some problems, such as high HC and CO emissions. In case of early direct injection, it is important to avoid wall wetting by spray impingement, which can cause higher HC and CO emissions. Since it is not easy to examine the effects of initial flow and injection parameters on mixture formation over the wide range by practical engine tests, a computer program named “GTT (Generalized Tank and Tube)” code was used to simulate the in-cylinder phenomena before autoignition.
Technical Paper

Spray Characteristics of LPG Direct Injection Diesel Engine

2003-03-03
2003-01-0764
In this study, spray images of LPG Blended Fuels (LBF) for DI diesel engines were observed using a constant volume chamber at high ambient temperature and pressure, and the spray characteristics of the fuel were investigated. The LBF spray started to vaporize at the injector tip and the outer downstream regions of the spray, like diesel fuel, because of the high temperature at these areas. There were more vaporized areas compared to diesel fuel. Sufficient fuel injection volume and volatility of LBF resulted in good fuel-air mixture, then, THC emissions decreased compared to diesel fuel at high load engine test conditions. Butane spray image could not be observed at the injector tip. It seems that the high temperature of the injector tip caused the butane spray to vaporize rapidly. Spray tip penetration with LBF and butane were equal or greater than with diesel fuel. The high volatility of LBF and butane had no noticeable effect on spray penetration.
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

Observation of Flame Propagation in an LPG Lean Burn SI Engine

1999-03-01
1999-01-0570
Using an extended bottom view piston having a quartz window, flame propagation observation and flame contour analysis were carried out to investigate the combustion characteristics of a heavy-duty type LPG lean burn engine. The swirl ratio and piston cavity configuration were varied to investigate their effects on combustion and engine performance. Gradual reduction of NOx but increased hydrocarbon emissions were measured for leaner mixtures compared to the stoichiometric operation. High swirl apparently accelerated the initial flame kernel development, as evidenced by a shorter crank angle interval from the spark ignition to the maximum cylinder pressure. The ‘D’ type cavity, with an increased squish area located below the intake valve, was shown to have the shortest burn duration among the piston cavities tested. The experimental flame propagation observation procedure was shown to be useful for the study of the combustion process in engines.
Technical Paper

Conversion of Nitric Oxide to Nitrogen Dioxide Using Hydrogen Peroxide

2000-06-19
2000-01-1931
Detailed chemical kinetic model of hydrogen peroxide (H2O2) into diesel exhaust gas has been executed to investigate its effect on the removal of nitric oxide(NO) by changing exhaust gas temperature and H2O2 addition amount. Flux analysis has also been done to clarify which reaction mainly affects NO-to-NO2 conversion. From the results of this study, it is shown that the optimal temperature condition to maximize the removal of NO exists near at 500K for OH addition condition, while that for H2O2 addition exists near at 800K. It is also shown that temperature window for the removal of NO becomes widened as the initial temperature of the exhaust gas increases, and NO-to-NO2 conversion rate decreases in proportion to the concentration of hydrocarbon(HC), although that of the total NOx remains the same level regardless of HC concentration. Finally, it is shown that HO2 + NO → NO2 + OH is mainly responsible for NO-to-NO2 conversion.
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

Development of LPG SI and CI Engines for Heavy Duty Vehicles

2000-06-12
2000-05-0166
Development of LPG SI and CI engines for heavy duty vehicles has been carried out. In order to measure the performance and emissions of an LPG lean burn SI engine, the piston cavity, swirl ratio, and propane-butane fuel ratio were varied and tested. Compared to the bathtub and dog dish cavities, the nebula type cavity showed the best performance in terms of cyclic variation and combustion duration. High swirl improved combustion by achieving a high thermal efficiency and low NOx emissions. A feasibility study of an LPG DI diesel engine also has been carried out to study the effectiveness of the selected cetane enhancing additives:Di-tertiary-butyl peroxide (DTBP). When more than 5 wt% DTBP was added to the base fuel, stable engine operation over a wide range of engine loads was possible. The thermal efficiency of LPG fueled operation was found to be comparable to diesel fuel operation at DTBP levels over 5 wt%.
Technical Paper

Influence of Fuel Injector Nozzle Geometry on Internal and External Flow Characteristics

1997-02-24
970354
The effects of upstream conditions, such as nozzle and entrance shapes, on external flow characteristics continue to challenge fuel injection modeling efforts, particularly in the case of high-pressure diesel sprays. In this research, flow details were investigated both experimentally and numerically in a fuel injector nozzle orifice using an integrated approach. Calculations using the SIMPLE algorithm were first performed for the scaled-up experimental nozzles with various length to diameter ratios (L/d). Measurements of internal flow velocities for these nozzles were made by laser Doppler velocimetry in order to verify the computational results. Mean and fluctuating velocities and discharge coefficients were obtained at various Reynolds numbers. The mean turbulence intensity and turbulent kinetic energy for a sharp inlet nozzle were generally higher than for a round inlet nozzle, except for the near-wall region beginning at about one nozzle diameter from the entrance.
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 Investigation of the Combustion Process in an LPG Lean-burn SI Engine

1999-10-25
1999-01-3510
Band spectrum images for CH, OH and CHO were taken in a heavy duty type LPG lean-burn SI engine, to investigate the combustion process as it pertains to the pollutant formation process in the post flame region. Full spectra and band spectrum flame images were observed with a bottom view single cylinder research engine and two high speed cameras. NOx emissions were also measured for excess air ratios ranging from 1.0 to 1.6. A thermodynamic model, including the detailed chemical kinetic mechanism for LPG and NOx formation reactions, was developed to predict the major reaction species in the post flame region, and NOx emissions during the combustion process. The model qualitatively described the flame images for each band spectrum and could predict the measured NOx emissions very well.
Technical Paper

Development of an LPG DI Diesel Engine Using Cetane Number Enhancing Additives

1999-10-25
1999-01-3602
A feasibility study of an LPG DI diesel engine has been carried out to study the effectiveness of two selected cetane enhancing additives: Di-tertiary-butyl peroxide (DTBP) and 2-Ethylhexyl nitrate (EHN). When more than either 5 wt% DTBP or 3.5 wt% 2EHN was added to the base fuel (100 % butane), stable engine operation over a wide range of engine loads was possible (BMEPs of 0.03 to 0.60 MPa). The thermal efficiency of LPG fueled operation was found to be comparable to diesel fuel operation at DTBP levels over 5 wt%. Exhaust emissions measurements showed that NOx and smoke levels can be significantly reduced using the LPG+DTBP fuel blend compared to a light diesel fuel at the same experimental conditions. Correlations were derived for the measured ignition delay, BMEP, and either DTBP concentration or cetane number. When propane was added to a butane base fuel, the ignition delay became longer.
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