Breda Kegl

Numerical and experimental study of water/oil emulsified fuel combustion in a diesel engine ☆

Numerical and experimental studies were made on some of the chemical and physical properties of water/oil emulsified fuel (W/OEF) combustion characteristics. Numerical investigations of W/OEF combustions chemical kinetic aspects have been performed by simulation of water/n-heptane mixture combustion, assuming a model of a homogenous reactors concentric shells. The injection and fuel spray characteristics are analyzed numerically also in order to study indirectly the physical effects of water present in diesel fuel during the combustion process. The experimental results of W/OEF combustion in the DI diesel engine are also presented and discussed. The results of engine testing in a broad field of engine loads and speeds have shown a significant pollutant emission reduction with no worsening of specific fuel consumption.

Influence of biodiesel on injection, fuel spray, and engine characteristics

This paper discusses the influence of biodiesel on the injection, spray, and engine characteristics with the aim to reduce harmful emissions. The considered engine is a bus diesel engine with injection M system. The injection, fuel spray, and engine characteristics, obtained with biodiesel, are compared to those obtained with mineral diesel under peak torque and rated conditions. The considered fuel is neat biodiesel from rapeseed oil. Its density, viscosity, surface tension, and sound velocity are determined experimentally and compared to those of mineral diesel. The experimentally obtained results are used to analyze the most important injection, fuel spray, and engine characteristics. Furthermore, the influence of biodiesel usage on lubrication is presented briefly. The results indicate that, by using biodiesel, harmful emissions (NOx, CO, HC, smoke, and PM) can be reduced to some extent by adjusting the injection pump timing properly while keeping other engine characteristics within acceptable limits. Furthermore, the results indicate better lubrication conditions when biodiesel is used.

Determining the speed of sound, density and bulk modulus of rapeseed oil, biodiesel and diesel fuel

Modern tendencies in the development of diesel engines include the operation of the system for injecting diesel fuel at pressures higher than 100 MPa. Knowing the characteristics of liquid fuels such as speed of sound, bulk modulus and density depending on pressure, is important for predicting the behavior of fuel injection systems for diesel engines and optimization of the same. The paper presents an original method and apparatus (device) for determining the speed of sound and density of fluids depending on the pressures. With this method, values of these characteristics for rapeseed oil, biodiesel, and conventional diesel fuel at pressures up to 160 MPa are determined. The method is non-destructive, it can also be applied to higher pressures than 160 MPa, as well as other liquid fluids that are used at high pressure – hydraulic oil, for example.

Guidelines for Improving Diesel Engine Characteristics

Diesel engine characteristics depend significantly on the engine type. But, even for a given engine type, the engine characteristics can still be varied in a wide range in dependence on engine management, exhaust gas after treatment, and usage of alternative fuels (Fino et al. 2003; Gray and Frost 1998; Maiboom et al. 2008; Peng et al. 2008; Stanislaus et al. 2010; Twigg 2007) (Fig. 3.1). Engine management and alternative fuels usage offer a possibility to reduce the formation of harmful emissions. On the other hand, exhaust gas after treatment techniques enable a reduction of harmful emissions already produced by the engine.

Biodiesel as Diesel Engine Fuel

In recent years, the interest to use biodiesel as a substitute for mineral diesel has been increasing steadily. Biodiesel is a renewable fuel, consisting of various fatty acid methyl esters with the exact composition depending on the feedstock. This is a distinctly different composition than the hydrocarbon content of mineral diesel. In spite of that, biodiesel has many properties very close to those of mineral diesel. Consequently, the required biodiesel-related modifications of the diesel engine are typically rather minor. On the other hand, because of its different chemical character, biodiesel has several properties, which differ from those of mineral diesel just enough to offer an opportunity to reduce harmful emissions without worsening other economy and engine performances. It should be noted, however, that biodiesel properties may depend heavily on its raw materials.

Diesel Engine Characteristics

Diesel engine is a compression ignition engine of a 2- or 4-stroke type. From the p − V diagrams (Fig. 2.1), it can be seen that the duration of the whole diesel cycle is 360°CA for the two-stroke engine and 720°CA for the four-stroke engine. The whole cycle consists of the following phases: intake of air, compression of air, fuel injection, mixture formation, ignition, combustion, expansion, and exhaust. The intake phase begins with the intake valve opening and lasts till the intake valve closing. After that the intake air is compressed to a level corresponding to compression ratios from 14:1 to 25:1 (Bauer 1999) or even more. The compression ratio e is a geometrical quantity, defined as

Efficient Velomobile Design

\varepsilon =\frac{V_{\max }}{V_{\min }}=\frac{V_{\mathrm{h}}+{V}_{\mathrm{c}}}{V_{\mathrm{c}}},