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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.
Technical Paper

Time-Resolved Behavior of Unburned Hydrocarbon Components in Diesel Exhaust Under Transient Operations

2001-03-05
2001-01-1259
Time resolved changes in unburned hydrocarbon emissions and their components were investigated in a DI diesel engine with a specially developed gas sampling system and gas chromatography. The tested transient operations include starting and increasing loads. At start-up with high equivalence ratios the total hydrocarbon (THC) at first increased, and after a maximum gradually decreased to reach a steady state value. Reducing the equivalence ratio of the high fueling at start-up and shortening the high fueling duration are effective to reduce THC emissions as long as sufficient startability is maintained. Lower hydrocarbons, mainly C1-C8, were the dominant components of the THC and mainly determined the THC behavior in the transient operations while the proportion of hydrocarbon (HC) components did not significantly change. The unregulated toxic substances, 1,3 butadiene and benzene were detected in small quantities.
Technical Paper

Low Emission and Knock-Free Combustion with Rich and Lean Biform Mixture in a Dual-Fuel CI Engine with Induced LPG as the Main Fuel

2001-09-24
2001-01-3502
Smokeless and ultra low NOx combustion without knocking in a dual-fuel diesel engine with induced LPG as the main fuel was established with a uniquely developed piston cavity divided by a lip in the sidewall. A small quantity of diesel fuel was directly injected at early compression stroke into the lower part of the cavity as an ignition source for this confined area, and this suppressed explosively rapid combustion just after ignition and spark-knock like combustion at later stage. A combination of the divided cavity, EGR, and intake air throttling was effective to simultaneously eliminate knocking, and reduce THC and NOx significantly.
Technical Paper

Improvement of Diesel Combustion and Emissions with Addition of Various Oxygenated Agents to Diesel Fuels

1996-10-01
962115
The effect of eight kinds of oxygenated agents added to diesel fuels on the combustion and emissions was investigated in a DI diesel engine. The results showed significant smoke and particulate suppression without increases in NOx with every oxygenated agent. The emissions decreased linearly with increasing oxygen content in the fuels, almost regardless of the kind of oxygenated agent. The improvement in smoke and particulate emissions with the oxygenated agent addition was more significant for lower volatility fuels. Combustion analysis with the two-dimensional two color method showed that soot concentration in the flame during the combustion process decreased with the addition of the oxygenated agent while the flame temperature distribution was almost unchanged.
Technical Paper

In-Cylinder Control of Smoke and NOx by High Turbulent Two-Stage Combustion in Diesel Engines

1996-10-01
962113
The authors have previously reported significant reductions in particulate emissions by generating strong turbulence during the combustion process. Extending this, it was attempted to reduce NOx, particulate, and fuel consumption simultaneously by two-stage combustion: forming a fuel rich mixture at the initial combustion stage to prevent NOx formation, and inducing strong turbulence in the combustion chamber at the later stage of combustion to oxidize the particulate. The purpose of this study is to examine the effect of two-stage combustion in emission control. The paper gives an evaluation of the NO reaction-kinetics of the system and experimental results for a combustion chamber specially made for the two-stage combustion. With this combustion system, it was possible to reduce NOx levels to 1/3 of the base engine. Combination of EGR and the two-stage combustion was also examined.
Technical Paper

Development of a Micro-Reactor HC-SCR System and the Evaluation of NOx Reduction Characteristics

2015-09-01
2015-01-2021
To reduce NOx emissions from diesel engines, the urea-SCR (selective catalytic reduction) system has been introduced commercially. In urea-SCR, the freezing point of the urea aqueous solution, the deoxidizer, is −11°C, and the handling of the deoxidizer under cold weather conditions is a problem. Further, the ammonia escape from the catalyst and the generation of N2O emissions are also problems. To overcome these disadvantages of the urea-SCR system, the addition of a hydrocarbon deoxidizer has attracted attention. In this paper, a micro-reactor SCR system was developed and attached to the exhaust pipe of a single cylinder diesel engine. With the micro-reactor, the catalyst temperature, quantity of deoxidizer, and the space velocity can be controlled, and it is possible to use it with gas and liquid phase deoxidizers. The catalyst used in the tests reported here is Ag(1wt%)-γAl2O3.
Technical Paper

Significant NOx Reductions with Direct Water Injection into the Sub-Chamber of an IDI Diesel Engine

1995-02-01
950609
The effect of direct water injection into the combustion chamber on NOx reduction in an IDI diesel engine was investigated. The temperature distribution in the swirl chamber was analyzed quantitatively with high speed photography and the two color method. Direct water injection into a swirl chamber prior to fuel injection reduced NOx emission significantly over a wide output range without sacrifice of BSFC. Other emissions were almost unchanged or slightly decreased with water injection. Water injection reduced the flame temperature at the center of the swirl chamber, while the mean gas temperature in the cylinder and the rate of heat release changed little.
Technical Paper

Improvements to Premixed Diesel Combustion with Ignition Inhibitor Effects of Premixed Ethanol by Intake Port Injection

2010-04-12
2010-01-0866
Premixed diesel combustion modes including low temperature combustion and MK combustion are expected to realize smokeless and low NOx emissions. As ignition must be delayed until after the end of fuel injection to establish these combustion modes, methods for active ignition control are being actively pursued. It is reported that alcohols including methanol and ethanol strongly inhibit low temperature oxidation in HCCI combustion offering the possibility to control ignition with alcohol induction. In this research improvement of diesel combustion and emissions by ethanol intake port injection for the promotion of premixing of the in-cylinder injected diesel fuel, and by increased EGR for the reduction of combustion temperature.
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

HCCI Combustion Control by DME-Ethanol Binary Fuel and EGR

2012-09-10
2012-01-1577
The HCCI engine offers the potential of low NOx emissions combined with diesel engine like high efficiency, however HCCI operation is restricted to low engine speeds and torques constrained by narrow noise (HCCI knocking) and misfiring limits. Gasoline like fuel vaporizes and mixes with air, but the mixture may auto-ignite at the same time, leading to heavy HCCI knocking. Retarding the CA50 (the crank angle of the 50% burn) is well known as a method to slow the maximum pressure rise rate and reduce HCCI knocking. The CA50 can be controlled by the fuel composition, for example, di-methyl ether (DME), which is easily synthesized from natural gas, has strong low temperature heat release (LTHR) characteristics and ethanol generates strong LTHR inhibitor effects. The utilization of DME-ethanol binary blended fuels has the potential to broaden the HCCI engine load-speed range.
Technical Paper

Combustion Characteristics of Emulsified Blends of Aqueous Ethanol and Diesel Fuel in a Diesel Engine with High Rates of EGR and Split Fuel Injections

2011-08-30
2011-01-1820
Silent, clean, and efficient combustion was realized with emulsified blends of aqueous ethanol and diesel fuel in a DI diesel with pilot injection and cooled EGR. The pilot injection sufficiently suppressed the rapid combustion to acceptable levels. The thermal efficiency with the emulsified fuel improved as the heat release with the pilot injection was retarded to near top dead center, due to poor ignitability and also due to a reduction in afterburning. With the emulsified fuel containing 40 vol% ethanol and 10 vol% water (E40W10), the smokeless operation range can be considerably extended even under low fuel injection pressure or low intake oxygen content conditions.
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.
Technical Paper

An Investigation of the Transient DPF Pressure Drop under Cold Start Conditions in Diesel Engines

2017-10-08
2017-01-2372
To monitor emission-related components/systems and to evaluate the presence of malfunctioning or failures that can affect emissions, current diesel engine regulations require the use of on-board diagnostics (OBD). For diesel particulate filters (DPF), the pressure drop across the DPF is monitored by the OBD as the pressure drop is approximately linear related to the soot mass deposited in a filter. However, sudden acceleration may cause a sudden decrease in DPF pressure drop under cold start conditions. This appears to be caused by water that has condensed in the exhaust pipe, but no detailed mechanism for this decrease has been established. The present study developed an experimental apparatus that reproduces rapid increases of the exhaust gas flow under cold start conditions and enables independent control of the amount of water as well as the gas flow rate supplied to the DPF.
Technical Paper

Visualization and Heat Release Analysis of Premixed Diesel Combustion with Various Fuel Ignitabilities and Oxygen Concentrations in a Constant Volume Combustion Vessel

2013-04-08
2013-01-0899
Low NOx and soot free premixed diesel combustion can be realized by increasing ignition delays in low oxygen atmospheres, as well as the combustion here also depends on fuel ignitability. In this report single intermittent spray combustion with primary reference fuels and a normal heptane-toluene blend fuel under several oxygen concentrations in a constant volume combustion vessel was analyzed with high-speed color video and pressure data. Temperature and KL factor distributions are displayed with a 2-D two-color method. The results show that premixing is promoted with a decrease in oxygen concentration, and the local high temperature regions, above 2200 K, as well as the duration of their appearance decreases with the oxygen concentration. With normal heptane, mild premixed diesel combustion can be realized at 15 vol% oxygen and there is little luminous flame.
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

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.
Journal Article

Improvement in DME-HCCI Combustion with Ethanol as a Low-Temperature Oxidation Inhibitor

2011-08-30
2011-01-1791
Port injection of ethanol addition as an ignition inhibitor was implemented to control ignition timing and expand the operating range in DME fueled HCCI combustion. The ethanol reduced the rate of low-temperature oxidation and consequently delayed the onset of the high-temperature reaction with ultra-low NOx over a wide operating range. Along with the ethanol addition, changes in intake temperature, overall equivalence ratio, and engine speed are investigated and shown to be effective in HCCI combustion control and to enable an extension of operation range. A chemical reaction analysis was performed to elucidate details of the ignition inhibition on low-temperature oxidation of DME-HCCI combustion.
Journal Article

Analysis of the Trade-off between Soot and Nitrogen Oxides in Diesel-Like Combustion by Chemical Kinetic Calculation

2011-08-30
2011-01-1847
This study makes use of the detailed mechanisms of n-heptane combustion, from gas reactions to soot particle formation and oxidation, and a two-stage model based on the CHEMKIN reactor network is developed and used to investigate the trade-off between soot and NOx emissions. The effects of the equivalence ratio, EGR, ambient pressure and temperature, and initial particle diameter are observed for various residence times. The results show that high rates of NOx formation are unavoidable under conditions where high reduction rates of soot particles are obtained. This suggests that suppression of the amount of soot during the formation stage is essential for simultaneous reductions in engine-out soot and NOx emissions.
Journal Article

Combustion and Emissions with Bio-alcohol and Nonesterified Vegetable Oil Blend Fuels in a Small Diesel Engine

2012-10-23
2012-32-0017
Combustion and exhaust gas emissions of alcohol and vegetable oil blends including a 20% ethanol + 40% 1-butanol + 40% vegetable oil blend and a 50% 1-butanol + 50% vegetable oil blend were examined in a single cylinder, four-stroke cycle, 0.83L direct injection diesel engine, with a supercharger and a common rail fuel injection system. A 50% diesel oil + 50% vegetable oil blend and regular unblended diesel fuel were used as reference fuels. The boost pressure was kept constant at 160 kPa (absolute pressure), and the cooled low pressure loop EGR was realized by mixing with a part of the exhaust gas. Pilot injection is effective to suppress rapid combustion due to the lower ignitability of the alcohol and vegetable oil blends. The effects of reductions in the intake oxygen concentration with cooled EGR and changes in the fuel injection pressure were investigated for the blended fuels.
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