NOx PM Research Articles

Effects of Oxymethylene Ether in a Commercial Diesel Engine

Oxymethylen Ether (OME) is a promising alternative fuel for diesel engines. It can be produced sustainably, and its combustion is clean and efficient. This study investigates the effects of different OME3-5 mixtures on emissions and combustion. The measurements were done on a four-cylinder common rail commercial diesel engine equipped with an exhaust gas recirculation system (EGR). Five different blends of OME3-5 and B7 diesel were applied with 0, 7, 15, 25 and 45 vol% OME3-5 content at four loads. The NOx–PM trade-off was investigated at 11 EGR rates for each mixture at each load. Increasing OME3-5 mixing ratio reduced the PM emission, improved the NOx–PM trade-off, and increased the brake thermal efficiency. The maximum achieved PM emission reduction was 86.8% for high loads. However, NOx emission increased, and also low heat capacity and viscosity can be a problem for real applications

Combustion and emission characteristics of E85 and diesel blend in conventional diesel engine operating in PPCI mode

To study the possibility of operating a traditional diesel engine as a partially premixed compression ignition engine, E85 created from 85% bioethanol and 15% unleaded Iraqi gasoline blend was used as the main fuel. E85 blend fuel has a low evaporation temperature, large latent heat and low cetane number (CN). Iraqi diesel fuel was used as a pilot fuel to assure ignition. High rate of cooled exhaust gas recirculation was used. The engine performance and emissions, particularly NOx–smoke trade-off, was also investigated. In order to reduce the number of experiments to be performed, the tests were conducted at a speed of 1500 rpm, with changes in the recirculated exhaust gas rate (10%, 30% and 50%) and change in injection timing (20°, 22°, 25°, 28° and 32° BTDC).Practical results showed that a significant improvement could be achieved in the NOx–PM trade-off. The ignition delay period can be increased by using a low-CN fuel accompanied with a low oxygen intake charge. When using the PPCI system, low levels of NOx and PM can be achieved without affecting the brake thermal efficiency of the engine. Smoke can be reduced even when the EGR percentage is increased under a mixed condition. ED10 (90% E85 + 10% diesel) had the largest decline in NOx (84.66%) and smoke (55.8%) compared to diesel.

Low Temperature Combustion Optimization and Cycle-by-Cycle Variability Through Injection Optimization and Gas-to-Liquid Fuel-Blend Ratio

The advent of common rail technology alongside powerful control systems capable of delivering multiple accurate fuel charges during a single engine cycle has revolutionized the level of control possible in diesel combustion. This technology has opened a new path enabling low-temperature combustion (LTC) to become a viable combustion strategy. The aim of the research work presented within this paper is the understanding of how various engine parameters of LTC optimize the combustion both in terms of emissions and in terms of fuel efficiency. The work continues with an investigation of in-cylinder pressure and IMEP cycle-by-cycle variation. Attention will be given to how repeatability changes throughout the combustion cycle, identifying which parts within the cycle are least likely to follow the mean trend and why. Experiments were conducted on a single-cylinder 510cc boosted diesel engine. LTC was affected over varying rail pressure and combustion phasing. Single and split injection regimes of varying dwell-times were investigated. All injection conditions were phased across several crank-angles to demonstrate the interaction between emissions and efficiency. These tests were then repeated with blends of 30% and 50% gas-to-liquid (GTL)-diesel blends in order to determine whether there is any change in the trends of repeatability and variance with increasing GTL blend ratio. The experiments were evaluated in terms of emissions, fuel efficiency, and cyclic behavior. Specific attention was given to how the NOx–PM trade-off changes through increased injection complexity and increasing GTL blend ratio. The cyclic behavior was analyzed in terms of in-cylinder pressure standard deviation. This gives a behavior profile of the repeatability of in-cylinder pressure in comparison to the mean. Each condition was then compared to the behavior of equivalent injection conditions in conventional diesel combustion. Short-dwell split injection was shown to be beneficial for LTC, while NOx was shown to be reduced by the substitution of GTL in the fuel. In-cylinder pressure cyclic behavior was also shown to be comparable or superior to conventional combustion in every case examined. GTL improved this further, but not in proportion to its blend ratio.

NOx and PM emissions reduction on an automotive HSDI Diesel engine with water-in-diesel emulsion and EGR: An experimental study

Automotive Diesel engines exhaust emissions must constantly be reduced to comply with more and more stringent regulations, all over the world. The introduction of water in the combustion chamber is already used on some large marine diesel engines to cut down NOx emission.In this paper an experimental study is conducted on a modern automotive 1.5l HSDI Diesel engine while injecting a water-in-diesel emulsion (WDE) with a volumetric water-to-fuel ratio of 25.6%. Four injection strategies are considered with and without pilot injection, with two levels of injection pressure. First, the injection of WDE is compared to diesel-fuel in terms of combustion and NOx and PM emissions without using exhaust gas recirculation (EGR). Depending on the WDE fuelling rate and injection strategy (with or without a pilot injection before main injection), NOx emissions are most often reduced (of up to 50%), and PM emission are most often decreased as well (the maximum relative reduction being 94%). The combustion is largely affected by the injection of WDE as compared with pure diesel-fuel, the main observations being an increased of the ignition delay and an improved mixing-process between the fuel and the surrounding gases.After that, the use of WDE in parallel with EGR (with various EGR rates) is tested with the aim at improving the NOx–PM trade-off (reduction of NOx emission at a given PM emission level or reduction of PM emission at a given NOx emission level). The results show that this method is an effective way for NOx and PM emission reduction on an automotive Diesel engine.

NOx・PM法における車種規制の経済分析 : 定量的政策評価

NOx・PM法における車種規制の経済分析 : 定量的政策評価

Remarkable improvement of NOx–PM trade-off in a diesel engine by means of bioethanol and EGR

In order to realize a premixed compression ignition (PCI) engine, the effects of bioethanol–gas oil blends and exhaust gas recirculation (EGR) on PM–NOx trade-off have been investigated focusing on ignition delay, premixed combustion, diffusion combustion, smoke, NOx and thermal efficiency. The present experiment was done by increasing the ethanol blend ratio and ethanol and by increasing the EGR ratio in a single cylinder direct injection diesel engine. It is found that a remarkable improvement in PM–NOx trade-off can be achieved by promoting the premixing based on the ethanol blend fuel having low evaporation temperature, large latent heat and low cetane number as well, in addition, based on a marked elongation of ignition delay due to the low cetane number fuel and the low oxygen intake charge. As a result, very low levels of NOx and PM, which satisfies the 2009 emission standards imposed on heavy duty diesel engines in Japan, were achieved without deterioration of brake thermal efficiency in the PCI engine fuelled with the 50% ethanol blend diesel fuel and the high EGR ratio. It is noticed that smoke can be reduced even by increasing the EGR ratio under the highly premixed condition.

Emissions from different alternative diesel fuels operating with single and split fuel injection

Few factors affect diesel combustion and emissions more significantly than the composition of the fuel and the fuel injection process. In this paper, both of these factors are considered by comparing conventional, synthetic and vegetable oil-derived diesel fuels and by comparing a single pulse injection and a split (pilot and main) injection process. This paper focuses on characterization of the combustion process and emissions produced by three substantially different diesel fuels: an ultra low sulfur diesel fuel (BP15), a pure soybean methyl ester (B100), and a synthetic, practically free of sulfur and aromatic compounds, Fischer–Tropsch fuel (FT) produced in a gas-to-liquid process. The study was carried out in a direct injection (DI) 2.5 L common-rail turbodiesel engine working at four engine operation modes, spanning conditions of most interest in the engine map. In all modes the engine was tested with single and split injection (pilot and main), with constant start of injection (SOI), and without exhaust gas recirculation (EGR). Using the results from thermodynamic analysis, this study confirms that the ignition character of the fuel affects the start of the combustion process, notably for the whole combustion process when the single injection is used, and during the combustion process after the pilot injection when the split injection is used. In general, the FT fuel can reduce both NOx and PM specific emissions in all modes under both single and split injection modes, bypassing the nitrogen oxides-particulate matter (NOx–PM) trade-off. Finally, this work confirms that biodiesel can reduce the particle concentration. However, in some cases an increase of PM mass emission has been observed and this increase of the PM mass emission is due to unburned or partially burned hydrocarbon (HC) emissions.

Consideration of the Control Method Using EGR for the HCCI Engine Running on DME

A Homgeneous Charge Compression Ignition (HCCI) engine is supposed to achieve high thermal effciency and low NOx PM emissions at the same time. Though it is expected to come into practical use, it has some serious problems such as ignition timing control, knocking at high load and securing of high combustion effciency. In this study, a four-stroke HCCI engine running on Di-Methyl Ether (DME) is developed to make it practicable as a generator engine. A new HCCI combustion control method, controlling the gas fraction of internal EGR gas at high temperature, external EGR gas at low temperature and premixture at stoichiometric ratio, is proposed. And effects of the gas fraction on HCCI combustion are researched by numerical calculation with elementally reactions and experiment. To conclude, HCCI combustion can be optimized with controlling the fraction of internal EGR gas, external EGR gas and premixture.