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The low auto-ignition temperature, rapid evaporation and high cetane number of dimethyl ether (DME) enables the use of low-pressure direct injection in compression ignition engines, thus potentially bringing the cost of the injection system down. This in turn holds the promise of bringing CI efficiency to even the smallest engines. A 50cc crankcase scavenged two-stroke CI engine was built based on moped parts. The major alterations were a new cylinder head and a 100 bar DI system using a GDI-type injector. Power is limited by carbon monoxide emission but smoke-free operation and NOx < 200ppm is achieved at all points of operation.

An experimental study has been carried out on the homogeneous charge compression ignition (HCCI) combustion of Dimethyl Ether (DME). The study was performed as a parameter variation of engine speed and compression ratio on excess air ratios of approximately 2.5, 3 and 4. The compression ratio was adjusted in steps to find suitable regions of operation, and the effect of engine speed was studied at 1000, 2000 and 3000 RPM. It was found that leaner excess air ratios require higher compression ratios to achieve satisfactory combustion. Engine speed also affects operation significantly.

This work is an extension to a previously reported work on chemical kinetic mechanism reduction scheme for large-scale mechanisms. Here, Perfectly Stirred Reactor (PSR) was added as a criterion of data source for mechanism reduction instead of using only auto-ignition condition. As a result, a reduced n-hexadecane mechanism with 79 species for diesel fuel surrogate was successfully derived from the detailed mechanism. Following that, the reduced n-hexadecane mechanism was validated under auto-ignition and PSR conditions using zero-dimensional (0-D) closed homogeneous batch reactor in CHEMKIN-PRO software. Agreement was achieved between the reduced and detailed mechanisms in ignition timing predictions and the reduced n-hexadecane mechanism was able to reproduce species concentration profiles with a maximum error of 40%. Accordingly, two-dimensional (2-D) Computational Fluid Dynamic (CFD) simulations were performed to study the spray combustion phenomena within a constant volume bomb.

This study explores the feasibility of using a sustainable lignin-based fuel, consisting of 44 % lignin, 50 % ethanol, and 6 % water, in conventional compression ignition (CI) marine engines. Through experimental evaluations on a modified small-bore CI engine, we identified the primary challenges associated with lignin-based fuel, including engine startup and shutdown issues due to solvent evaporation and lignin solidification inside the fuel system, and deposit formation on cylinder walls leading to piston ring seizure. To address these issues, we developed a fuel switching system transitioning from lignin-based fuel to cleaning fuel with 85 vol% of acetone, 10 vol% of water and 5 vol% of ignition improving additive, effectively preventing system clogs.

Studies were performed with three commonly used additive metals, cerium copper, and iron, with a conventional and a low sulfur fuel in order to investigate fuel additive effects on engine particulate emissions before a particulate filter. Measurements were made on a 4 cylinder direct injection diesel engine and included total particulate mass, soluble organic fraction for both fuels, and polynuclear aromatic hydrocarbon emissions for the low sulfur fuel. The cerium based additive reduced the emissions with both fuels, with the largest effect being on the non-SOF fraction. With the other additives and the high sulfur fuel, non-SOF emissions were increased, increasing total particulate emissions. Copper was found to reduce the polynuclear aromatic hydrocarbons, and cerium was found to have the least effect. The use of an SiC wall flow filter reduced particulate and polynuclear aromatic emissions by over 90%.

The main purpose of this study was to investigate the influence of diesel engine conditions on the mutagenic activity of the exhaust. Special emphasis was put on investigation of the influence of nitrogen oxides content. Experiments with a diesel engine have been carried out in the laboratory and the emissions of carbon monoxide (CO), carbon dioxide (CO2), nitrogen oxides (NOx) and particulate matter (PM) have been measured at different engine conditions. The particulate matter was extracted in order to obtain the soluble organic fraction (SOF), and this fraction was analyzed for mutagenic activity in the Salmonella/microsome assay (AMES test). It was found that the mutagenic activity evidently depended on the PAH content (PAH = Polycyclic Aromatic Hydrocarbons) of the exhaust gas rather than the NOx content. However, the percentage of the direct mutagenic activity of the total mutagenic activity increased as the NOx content in the exhaust gas increased.

Engine experiments were carried out on a six cylinder DI-diesel engine using synthetic fuel and lubricant containing no PAH (Polycyclic Aromatic Hydrocarbons) [1]. By selectively doping the fuel and oil with pyrene, the effect of fuel and oil originating PAH on the exhaust emissions could be investigated. The experimental results are analyzed in a new way by suggesting a general transport model for PAH. By estimating as many transport quantities as possible it is attempted to gain knowledge about the most dominant mechanisms. The main finding is not surprisingly that for commercial fuels containing substantial concentrations of PAH, the by far major contributor to exhaust PAH is unburned fuel PAH. The concentration of PAH in the oil sump affects only weakly the PAH concentration in the exhaust for engines operating on commercial fuels. The PAH desorbing from the liner are getting burned efficiently, thereby being insignificant.

This work concerns the modelling of soot formation process in diesel spray combustion under engine-like conditions. The key aim is to investigate the soot formation characteristics at different ambient temperatures. Prior to simulating the diesel combustion, numerical models including a revised multi-step soot model is validated by comparing to the experimental data of n-dodecane fuel in which the associated chemistry is better understood. In the diesel spray simulations, a single component n-heptane mechanism and the multi-component Diesel Oil Surrogate (DOS) model are adopted. A newly developed C16-based model which comprises skeletal mechanisms of n-hexadecane, heptamethylnonane, cyclohexane and toluene is also implemented. Comparisons of the results show that the simulated liftoff lengths are reasonably well-matched to the experimental measurement, where the relative differences are retained to below 18%.

The liquefied natural gas (LNG)-fueled ships were provisioned to meet the strict emission legislation in the marine application since 2000. However, the scientific approach of burning the low-emission natural gas in lean combustion uncovered that the engine suffers from high methane slip emission. Serious questions are raised about the quantity of methane slip during marine conditions when the load varies in multiple frequencies and amplitudes. Previous studies by these authors explained how methane slip increases during load oscillation. This paper examined several practical methods to reach stable combustion in transient conditions to reduce the methane slip. Employing Proportional-Integral-Derivative (PID) controllers in a closed loop, implementing open-loop lookup tables, model predictive controller (MPC), and an innovated solenoid method are performed in a high-fidelity medium-speed natural gas spark-ignition (SI) engine model.