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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.

A model which calculates the hydrocarbon emissions from an SI engine is presented. The model was developed in order to obtain a better under-standing of experimental results from an engine operating on different fuels and lubricants. The model is based on the assumptions that fuel is stored in crevices and oil film during intake and compression followed by desorption during expansion and exhaust. The model also calculates the amount of desorbed material that undergoes in cylinder oxidation and exhaust port oxidation. The model succesfully predicts the trends followed by varying different engine parameters. The effect of changing the lubricant is of the same order of magnitude as found experimentally, but the effect of changing the fuel could not be predicted very well by the model. A possible explanation is, that the lubricant film thickness varies due to viscosity variations of the oil film, when the fuel is dissolved in the film.

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.

Investigations were made concerning the formation of combustion chamber deposits (CCD) in SI gas engines fueled by producer gas. The main objective was to determine and characterise CCD and PAH formation caused by the presence of the light tar compounds phenol and guaiacol in producer gas from an updraft gasifier. The work was based on previous work regarding the assumption that phenol is a soot precursor and therefore could lead to CCD formation. Laboratory experiments were conducted, where pyrolysis products of the single tar components were collected on small aluminium plates. The experiments showed that guaiacol formed significant amount of deposits. The structure observed was a lacquer type of deposit. It was determined that there was no distinct deposit formation due to phenol. Experiments were conducted with a 0.48 litre one-cylinder high compression ratio SI engine fueled by synthetic producer gas.

The use of vegetable oil methyl esters has been proposed as an alternative fuel for diesel engines. The purpose of this study is to investigate the combustion of soybean oil methyl ester in a direct injection diesel engine, and compare it to that of a conventional diesel fuel. Experimental measurements of performance, emissions, and rate of heat release were performed as a function of engine load for different fuel injection timings, and injector orifice diameters. It was found that overall, the soybean oil methyl ester behaved comparably to diesel fuel in terms of performance and rate of heat release. The methyl ester fuel gave lower HC emissions and smoke number than diesel fuel at optimum operating conditions. The results for CO emissions were varied. NOx emissions were strongly related to the cylinder pressure development. Changing the injection orifice diameter had less effect on engine performance when using diesel fuel, than with methyl ester fuel.

With the current trend towards engine downsizing, the use of turbochargers to obtain extra engine power has become common. A great difficulty in the use of turbochargers is in the modelling of the compressor map. In general this is done by inserting the compressor map directly into the engine ECU (Engine Control Unit) as a table. This method uses a great deal of memory space and often requires on-line interpolation and thus a large amount of CPU time. In this paper a more compact, accurate and rapid method of dealing with the compressor modelling problem is presented. This method is physically based and is applicable to all turbochargers with radial compressors for either Spark Ignition (SI) or diesel engines.

Diesel spray experimentation at controlled high-temperature and high-pressure conditions is intended to provide a more fundamental understanding of diesel combustion than can be achieved in engine experiments. This level of understanding is needed to develop the high-fidelity multi-scale CFD models that will be used to optimize future engine designs. Several spray chamber facilities capable of high-temperature, high-pressure conditions typical of engine combustion have been developed, but because of the uniqueness of each facility, there are uncertainties about their operation. For this paper, we describe results from comparative studies using constant-volume vessels at Sandia National Laboratories and IFP.

The effects of methanol and EGR on HCCI combustion of dimethyl ether have been tested separately in a diesel engine. The engine was equipped with a common rail injection system which allowed for random injection of DME. The engine could therefore be operated either as a normal DI CI engine or, by advancing the injection timing 360 CAD, as an HCCI engine. The compression ratio of the engine was reduced to 14.5 by enlarging the piston bowls. The engine was operated in HCCI mode with DME at an equivalence ratio of 0.25. To retard the combustion timing, methanol was port fuel injected and the optimum quantity required was determined. The added methanol increased the BMEP by increasing the total heat release and retarding the combustion to after TDC. Engine knock was reduced with increasing quantities of methanol. The highest BMEP was achieved when the equivalence ratio of methanol was around 0.12 at 1000 RPM, and around 0.76 at 1800 RPM. EGR was also used to retarding the timing.

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.

Development of numerical tools for quantitatively assessing biofuel combustion in Internal Combustion Engines and facilitating the identification of optimum operating parameters and emission strategy are challenges of engine combustion research. Biofuels obtained through e.g. a Fischer-Tropsch process (FT) are complex mixtures of wide ranges of high molecular weight hydrocarbons in the diesel and naphtha boiling range dominated by C10-C18 hydrocarbons in n-alkane, iso-alkane, alkenes, aromatic and oxygenate classes. In this paper modeling of combustion in a rapid compression machine has been performed using model compounds from a given FT biofuel distribution as surrogate fuels. Furthermore, the detailed mechanism has been reduced by applying an automatic necessity analysis removing redundant species from the detailed model.

This paper describes the development and test of a method capable of determining the lubricity of low boiling point fuels with emphasis on Dimethyl Ether (DME). DME has excellent combustion characteristics but diesel engine injection equipment can break down due to extensive wear when handling this fuel. Earlier work has established that the lubricity of neat DME is considerably lower than that of diesel oil and kerosene. The repeatability of the results in this former work was poor though. In the present work, the Medium Frequency Pressurised Reciprocating Rig 2 (MFPRR2) was developed and tested. In this apparatus the influence of the frictional force on the load magnitude was eliminated resulting in a drastic improvement of the repeatability. The lubricity of DME was attempted redressed by adding either commercial wear reducing agents or a high lubricity fuel. A very few ppm of additive raised the lubricity of DME considerably to a level above the one of kerosene.

This paper describes the development and test of a viscometer capable of handling dimethyl Ether (DME) and other volatile fuels. DME has excellent combustion characteristics in diesel engines but the injection equipment can break down prematurely due to extensive wear when handling this fuel. It was established, in earlier work, that the wear in the pumps is substantial even if the lubricity of DME is raised to a believed acceptable level using anti-wear additives. An influence of the viscosity on the wear in the pumps was suspected. The problem, up to now, was that the viscosity of DME has only been estimated or calculated but never actually measured. In the present work a volatile fuel viscometer (VFVM) was developed. It is of the capillary type and it was designed to handle DME, neat or additised. The kinematic and dynamic viscosities of pure DME were measured at 0.185 cSt and 0.122 cP at 25 °C respectively.

An investigation has been performed of some of the characteristics of di-methyl ether (DME) during high pressure injection in a diesel fuel injection system with a single hole nozzle. Recent developments in the use of DME as an alternate fuel for diesel engines are discussed. The effects of fuel compressibility on compression work are compared for DME and typical hydrocarbon fuel components. Photographs of the transient injection process into room temperature Nitrogen are given for a range of chamber pressures. For a single hole injector, spray penetrations can be predicted using existing correlations for diesel fuel, provided DME fuel properties are used.

The issues addressed in this paper are investigation of the wear mechanisms present in the standard lubricity test for diesel oil: The High frequency Reciprocating Rig (HFRR). The HFRR is a laboratory wear test using a ball on disk configuration. The result of a test is the wear scar diameter (WSD) on the ball. Up to now, all analyses indicated that fuel viscosity influences the wear scar size and fuel performance in full-scale pumps. The wear scar size could then be a result of hydrodynamic lubrication (at least a significant part of it) and not of boundary lubrication as it was the original intention of the test. The appearance of an excellent volatile fuel for diesel engines, Dimethyl Ether (DME), has resulted in new wear tests such as the Medium Frequency Pressurised Reciprocating Rig (MFPRR), a pressurised version of the HFRR. DME has a about 25 times lower viscosity than diesel oil so the MFPRR viscosity sensibility issue is seriously aggravated for this fuel.

Initially, a new direct digital Diesel fuel injection system: an electronic Pump-Pipe-Valve-Injector system was introduced. A general comparison of this system with other electronic Diesel injection systems indicated that the new system can be more effective for high pressure Diesel injection and more flexible for wide engine speed range. Then, the digital injection control characteristics of this system were studied by both experiment and computer simulation. Some special digital injection control functions were obtained. In particular, it was found that transient effect of the control valve action can be used to regulate the pulsed Diesel fuel flow to achieve a low initial injection rate and high injection cut-off rate. This effect can be optimized by appropriate selection of the control valve location. Finally, a direct digital Diesel engine governing technique was investigated.

The effects of lubricant composition on hydrocarbon emissions from a SI engine have been experimentally investigated. Results based on measurements of solubilities of different fuel components in different types of lubricants are presented. 2 lubricants and two hydrocarbons were chosen for testing in a single cylinder engine. Emissions and performance was measured for various fuel air ratios and ignition timings. The lubricant with the lowest solubility with respect to isooctane also showed the lowest hydrocarbon emissions. The influence of the lubricant was greatest at lean air fuel ratios. Xylene is much more soluble in the lubricants than isooctane and gave lower hydrocarbon emissions when the engine was operated at rich air fuel ratios. At leaner mixtures, isooctane gave lower emissions. The results indicate that the lubricant plays a contributing, but not dominating role in hydrocarbon emissions from gasoline engines.

The effects of mixture turbulence on combustion in a spark-ignition engine were investigated using a CFR engine. The apparent instantaneous turbulent flame speed during combustion was calculated from a combustion heat release model that used measured cylinder pressures and assumed spherical flame propagation. This flame speed was correlated with turbulent intensities measured in the motored engine. The ratio of fully developed turbulent flame speed to laminar flame speed was found to be a linear function of motored turbulent intensity.

The aim of this study is to evaluate the existing chemical kinetic mechanism reduction techniques. From here, an appropriate reduction scheme was developed to create compact yet comprehensive surrogate models for both diesel and biodiesel fuels for diesel engine applications. The reduction techniques applied here were Directed Relation Graph (DRG), DRG with Error Propagation, DRG-aided Sensitivity Analysis, and DRG with Error Propagation and Sensitivity Analysis. Nonetheless, the reduced mechanisms generated via these techniques were not sufficiently small for application in multi-dimensional computational fluid dynamics (CFD) study. A new reduction scheme was therefore formulated. A 68-species mechanism for biodiesel surrogate and a 49-species mechanism for diesel surrogate were successfully derived from the respective detailed mechanisms.

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.

The utilisation of producer gas - from thermal gasification of biomass - as a fuel for spark ignition gas engines is of vital importance to the ongoing effort of making biomass gasification a commercially feasible technology. Tests have been carried out with a 1.1 litre four-cylinder natural aspirated SI engine in conjunction with a two-stage gasifier with a nominal thermal input of 100 kW. The fuel-gas is produced from wood chips in order to get a CO2 neutral fuel for combined heat and power production. The producer gas has a very low tar and particulate content and high hydrogen content. As the gasifier was operated with varying fuel properties, engine tests were made with different fuel-gas compositions. The engine tests showed that producer gas has a power and efficiency advantage compared to natural gas when operating the engine at lean burn conditions. The engine was operated at air/fuel ratios varying from stoichiometric to extremely lean burn (λ>3).