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Technical Paper

Analysis of car structures in future market and necessary policy for environment based on the vehicle performance and economic aspects

2000-06-12
2000-05-0382
Increasing CO2 emissions from vehicles is becoming a major concern in automotive society, and variety of future types of cars are intensively investigated. However it is not clear which level of performance and cost must be achieved for the future cars to be available in a market and how much percentage of cars is necessary to be replaced by the future cars for the conservation of environment. The objective of this paper is to evaluate the possibility of market growth of future cars, as hybrid cars, electric vehicles and fuel cell cars, based on the performance and economic aspects. This paper investigates the emission reduction potential of these vehicles, and also compares the composition of vehicle types and emissions for a variety of scenarios of consumer characteristics, economic growth, fuel price, performance of cars, and carbon tax control measures. A model of user preference of cars was established from the statistic analysis of past data.
Technical Paper

An Investigation on the Simultaneous Reduction of Particulate and NOx by Controlling Both the Turbulence and the Mixture Formation in DI Diesel Engines

1993-10-01
932797
This paper presents experimental results of the reduction of both particulate and NOx emitted from direct injection diesel engines by a two stage combustion process. The primary combustion is made very rich to reduce NOx and then the particulate is oxidized by strong turbulence generated during the secondary combustion. The rich mixture is formed by low pressure fuel injection and a small cavity combustion chamber configuration. The strong turbulence is generated by a jet of burned gas from an auxiliary chamber installed at the cylinder head. The results showed that NOx was reduced significantly while maintaining fuel consumption and particulate emissions. An investigation was also carried out on the particulate reduction process in the combustion chamber with the turbulence by gas sampling and in-cylinder observation with an optical fiber scope and a high speed camera.
Technical Paper

Study on Simple and High-Speed Diesel Combustion Model with Wall Impingement

2011-08-30
2011-01-1846
To design diesel engines adapted to future exhaust gas regulation, it would be advantageous to have a driving mode simulation for vehicle performance and exhaust emissions, including after-treatment systems. The combustion model for this objective must be able to simulate the engine performance in very short time. We have tried to develop such diesel engine combustion model by adding the improvements to the Hiroyasu model. In this paper, we detail the improvements that were added to this model and comparisons the calculated results by the improved model with experimental result.
Journal Article

Combustion Characteristics of Emulsified Blends of Water and Diesel Fuel in a Diesel Engine with Cooled EGR and Pilot Injection

2013-10-15
2013-32-9022
Water and diesel fuel emulsions containing 13% and 26% water by volume were investigated in a modern diesel engine with relatively early pilot injection, supercharging, and cooled EGR. The heat release from the pilot injection with water emulsions is retarded toward the top dead center due to the poor ignitability, which enables larger pilot and smaller main injection quantities. This characteristic results in improvements in the thermal efficiency due to the larger heat release near the top dead center and the smaller afterburning. With the 26% water emulsion, mild, smokeless, and very low NOx operation is possible at an optimum pilot injection quantity and 15% intake oxygen with EGR at or below 0.9 MPa IMEP, a condition where large smoke emissions are unavoidable with regular unblended diesel fuel. Heat transfer analysis with Woschni's equation did not show the decrease in cooling loss with the water emulsion fuels.
Technical Paper

Semi-Premixed Diesel Combustion with Twin Peak Shaped Heat Release Using Two-Stage Fuel Injection

2016-04-05
2016-01-0741
Characteristics of semi-premixed diesel combustion with a twin peak shaped heat release (twin combustion) were investigated under several in-cylinder gas conditions in a 0.55 L single cylinder diesel engine with common-rail fuel injection, super-charged, and with low pressure loop cooled EGR. The first-stage combustion fraction, the second injection timing, the intake oxygen concentration, and the intake gas pressure influence on thermal efficiency related parameters, the engine noise, and the exhaust gas emissions was systematically examined at a middle engine speed and load condition (2000 rpm, 0.7 MPa IMEP). The twin peak shaped heat release was realized with the first-stage premixed combustion with a sufficient premixing duration from the first fuel injection and with the second fuel injection taking place just after the end of the first-stage combustion.
Technical Paper

Characteristics of Diesel Soot Suppression with Soluble Fuel Additives

1987-09-01
871612
Experiments on a large number of soluble fuel additives were systematically conducted for diesel soot reduction. It was found that Ca and Ba were the most effective soot suppressors. The main determinants of soot reduction were: the metal mol-content of the fuel, the excess air factor, and the gas turbulence in the combustion chamber. The soot reduction ratio was expressed by an exponential function of the metal mol-content in the fuel, depending on the metal but independent of the metal compound. A rise in excess air factor or gas turbulence increased the value of a coefficient in the function, resulting in larger reductions in soot with the fuel additives. High-speed soot sampling from the cylinder showed that with the metal additive, the soot concentration in the combustion chamber was substantially reduced during the whole period of combustion. It is thought that the additive acts as a catalyst not only to improve soot oxidation but also to suppress soot formation.
Technical Paper

Catalytic Reduction of NOx in Actual Diesel Engine Exhaust

1992-02-01
920091
Copper ion-exchanged ZSM-5 zeolite catalyst, which reduces nitrogen oxides (NOx) in the presence of oxygen and hydrocarbons, was applied to actual diesel engine exhaust. Copper ion-exchanged ZSM-5 zeolite effectively reduced NOx by 25% in normal engine operation, and by 80% when hydrocarbons in the exhaust were increased. Water in the exhaust gas decreased the NOx reduction efficiency, but oxygen and sulfur appeared to have only a small effect. Maximum NOx reduction was observed at 400°C irrespective of hydrocarbon species, and did not decrease with space velocity up to values of 20,000 1/h. THE PURPOSE of this paper is to evaluate the possibilities and problems in catalytic reduction of NOx in actual diesel engine exhaust. Here, a copper ion-exchanged ZSM-5 zeolite (Cu-Z) catalyst was applied to diesel engine exhaust to examine the dependency of the NOx reduction efficiency on temperature and space velocity. The effects of oxygen, water and hydrocarbons were also examined.
Technical Paper

Reduction of Smoke and NOx by Strong Turbulence Generated During the Combustion Process in D.I. Diesel Engines

1992-02-01
920467
This paper presents results of experiments to reduce smoke emitted from direct Injection diesel engines by strong turbulence generated during the combustion process. The turbulence was created by jets of burned gas from an auxiliary chamber installed in the cylinder head. Strong turbulence, which was induced late in the combustion period, enhanced the mixing of air with unburned fuel and soot, resulting in a remarkable reduction of smoke and particulate; NOx did not show any increase with this system, and thermal efficiency was improved at high loads. The paper also shows that the combination of EGR and water injection with this system effectively reduces the both smoke and NOx.
Technical Paper

Time Series Analysis of Diesel Exhaust Gas Emissions Under Transient Operation

1993-03-01
930976
Time series analysis of diesel exhaust gas emissions under transient operation was carried out using a uniquely developed gas sampling system to efficiently collect all exhaust gas throughout transient cycles. The effects of fuel properties and other engine operation parameters on the exhaust emissions under transient runs when fuel amounts abruptly increase were analyzed. The results showed that THC increased abruptly to 2 or 6 times the final steady-state concentration immediately after the start of acceleration and then decreased to the steady-state values after 70∼200 cycles. At acceleration, NOx increased abruptly to about 80 % of the final NOx concentration, and then increased gradually to reach the final values after 60∼500 cycles. The behaviors of THC and NOx during transient operation can be described by exponential functions of the elapsed cycle numbers and the final emission concentrations.
Technical Paper

Description of Diesel Emissions by Individual Fuel Properties

1992-10-01
922221
The effects of several fuel property variables on the emissions from a D.I. diesel engine were individually analyzed. The results showed that the smoke and dry soot increased with increased kinematic viscosity, shorter ignition lag, and higher aromatic content, especially at high equivalence ratios. Over the whole range of equivalence ratios, SOF depended on and increased with only ignition lag. The NOx improved slightly with increased kinematic viscosity, higher ignitability, and decreased aromatic content. The unburnt HC also improved with decreased kinematic viscosity and higher ignitability. The distribution shape of distillation curves had little influence on the emissions.
Technical Paper

Ultra Low Emission and High Performance Diesel Combustion with Highly Oxygenated Fuel

2000-03-06
2000-01-0231
Significant improvements in exhaust emissions and engine performance in an ordinary DI diesel engine were realized with highly oxygenated fuels. The smoke emissions decreased sharply and linearly with increases in oxygen content and entirely disappeared at an oxygen content of 38 wt-% even at stoichiometric conditions. The NOx, THC, and CO were almost all removed with a three-way catalyst under stoichiometric diesel combustion at both the higher and lower BMEP with the combination of EGR and a three-way catalyst. The engine output for the highly oxygenated fuels was significantly higher than that with the conventional diesel fuel due to the higher air utilization.
Technical Paper

Improvements of Diesel Combustion and Emissions with Two-stage Fuel Injection at Different Piston Positions

2000-03-06
2000-01-1180
The fuel spray distribution in a DI diesel engine with pilot injection was actively controlled by pilot and main fuel injections at different piston positions to prevent the main fuel injection from hitting the pilot flame. A CFD analysis demonstrated that the movement of the piston with a cavity divided by a central lip along the center of the sidewall effectively separates the cores of the pilot and main fuel sprays. Experiments showed that an ordinary cavity without the central lip emitted more smoke, while smokeless, low NOx operation was realized with a cavity divided by a central lip even at heavy loads where ordinary operation without pilot injection emits smoke.
Technical Paper

Improvement of Combustion and Emissions in a Dual Fuel Compression Ignition Engine with Natural Gas as the Main Fuel

2015-04-14
2015-01-0863
Dual fuel combustion with premixed natural gas as the main fuel and diesel fuel as the ignition source was investigated in a 0.83 L, single cylinder, DI diesel engine. At low loads, increasing the equivalence ratio of natural gas to around 0.5 with intake throttling makes it possible to reduce the THC and CO emissions as well as to improve the thermal efficiency. At high loads, increasing the boost pressure moderates the combustion, but increases the THC and CO emissions, resulting in deterioration of the thermal efficiency. The EGR is essential to suppress the rapid combustion. As misfiring occurs with a compression ratio of 14.5 and there is excessively rapid combustion with 18.5 compression ratio, 16.5 is a suitable compression ratio.
Technical Paper

Improvement of Performance and Emissions of a Compression Ignition Methanol Engine with Dimethyl Ether

1994-10-01
941908
Dimethyl ether (DME) has very good compression ignition characteristics, and can be converted from methanol using a γ - alumina catalyst. A previous report investigated a compression ignition methanol engine with DME as an ignition improver. The results showed that the engine operation was sufficiently smooth without either spark or glow plugs. Two methods were studied, one was an aspiration method, and the other was a torch ignition chamber method (TIC method). The aspiration method allows a simple engine structure, but suffers from poor engine emissions and requires large amounts of DME. With the TIC method where the DME was introduced into a torch ignition chamber (TIC) during the intake stroke, the diffusion of the DME into the main combustion chamber was limited, and significant reductions in both the necessary quantity of DME and emissions were obtained [1][2].
Technical Paper

Ultra Low Emissions and High Performance Diesel Combustion with a Combination of High EGR, Three-Way Catalyst, and a Highly Oxygenated Fuel, Dimethoxy Methane (DMM)

2000-06-19
2000-01-1819
Ultra low emissions and high performance combustion was achieved with a combination of high EGR, a three-way catalyst, and a highly oxygenated liquid fuel, neat dimethoxy methane (DMM), in an ordinary DI diesel engine. The smokeless nature of neat DMM effectively allowed stoichiometric diesel combustion by controlling BMEP with EGR. NOx, THC, and CO emissions were reduced with a three-way catalyst. At lower BMEP with excess air, the EGR effectively reduced NOx. High-speed video in a bottom view type engine revealed that luminous flame decreased with increased fuel oxygen content and almost disappeared with DMM.
Technical Paper

Time-Resolved Nature of Exhaust Gas Emissions and Piston Wall Temperature Under Transient Operation in a Small Diesel Engine

1996-02-01
960031
Diesel combustion and exhaust gas emissions under transient operation (when fuel amounts abruptly increased) were investigated under a wide range of operating conditions with a newly developed gas sampling system. The relation between gas emissions and piston wall temperatures was also investigated. The results indicated that after the start of acceleration NOx, THC and smoke showed transient behaviors before reaching the steady state condition. Of the three gases, THC was most affected by piston wall temperature; its concentration decreased as the wall temperature increased throughout the acceleration except immediately after the start of acceleration. The number of cycles, at which gas concentrations reach the steady-state value after the start of acceleration, were about 1.2 times the cycle constant of the piston wall temperature for THC, and 2.3 times for smoke.
Technical Paper

Simultaneous Reductions of Smoke and NOx from a DI Diesel Engine with EGR and Dimethyl Carbonate

1995-10-01
952518
Extensive experiments were conducted on a low emission DI diesel engine by using Dimethyl Carbonate (DMC) as an oxygenate fuel additive. The results indicated that smoke reduced almost linearly with fuel oxygen content. Accompanying noticeable reductions of HC and CO were attained, while a small increase in NOx was encountered. The effective reduction in smoke with DMC was maintained with intake charge CO2, which led to low NOx and smoke emissions by the combined use of oxygenated fuel and exhaust gas recirculation (EGR). Further experiments were conducted on an optically accessible combustion bomb and a thermal cracking set-up to study the mechanisms of DMC addition on smoke reduction.
Technical Paper

Combustion and Emissions in a New Concept DI Stratified Charge Engine with Two-Stage Fuel Injection

1994-03-01
940675
A new concept DISC engine equipped with a two-stage injection system was developed. The engine was modified from a single cylinder DI diesel engine with large cylinder diameter (135mm). Combustion characteristics and exhaust emissions with regular gasoline were examined, and the experiments were also made with gasoline-diesel fuel blends with higher boiling temperatures and lower octane numbers. To realize stratified mixture distribution in combustion chamber flexibly, the fuel was injected in two-stages: the first stage was before the compression stroke to create a uniform premixed lean mixture and the second stage was at the end of the compression stroke to maintain stable ignition and faster combustion. In this paper, the effect of the two-stage injection on combustion and exhaust emissions were analyzed under several operating conditions.
Technical Paper

Cycle-to-cycle Transient Characteristics of Diesel Emissions during Starting

1999-10-25
1999-01-3495
Changes in exhaust gas emissions during starting in a DI diesel engine were investigated. The THC after starting increased until around the 50th cycle when the fuel deposited on the combustion chamber showed the maximum, and THC then decreased to reach a steady value after about 1000 cycles when the piston wall temperature became constant. The NOx showed an initial higher peak just after starting, and increased to a steady value after about 1000 cycles. Exhaust odor had a strong correlation with THC, and at the early stage odor was stronger than would be expected from the THC concentration. The THC increased with increased fuel injection amounts, decreased cranking speeds, and fuels with higher viscosity, higher 90% distillation temperature, and lower ignitability.
Technical Paper

Performance of NOX Catalyst in a DI Diesel Engine Operated with Neat Dimethyl Ether

1999-10-25
1999-01-3599
An experiment was conducted with a direct injection Diesel engine operated with neat dimethyl ether (DME). Main focus of this research is to investigate the performance of the catalysts designed for NOx reduction, such as Co–alumina and Sn–alumina catalysts, for the reduction of NOX and other unburned species contained in the exhaust gas. In the experiments, DME concentration in the exhaust gas was changed by adding extra DME before the catalytic reactor, which is the important experimental parameter in the research. Results showed that NOX reduction rate was not so high without any DME addition, because the content of unburned DME, reducing agent, is very low in the DME engine exhaust gas. However, NOX reduction rate increased with increase in DME content and it reached around 80% with enough DME addition. The NOX reduction rate increased with increase in reaction temperature up to around 300 °C.
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