Spray atomization of alternative fuels in medium speed diesel engines

Until today, the diesel engine is still the most important power source for heavy duty road & rail transport, marine, genset and agriculture applications. The decreasing reserves of fossil fuels, the strict emission regulations, the greenhouse effect, the increasing energy demand and fuel prices are all strong drivers for research into the use of alternative fuels in internal combustion engines. Potential alternative fuels for this application are straight vegetable oils and animal fats. Several manufacturers of medium speed diesel engines show interest. However, due to the difference in fuel properties problems due to the lack of knowledge still exists and engine modifications are required. The study focused on the understanding of the behavior of the fuel during injection in the engine. This was realized through both experimental and numerical work. For the experimental work, a constant volume combustion chamber, equipped with a medium speed diesel injection system, was developed and baptized as the Ghent University Combustion Chamber I (a.k.a. GUCCI). The setup allows the simulation of engine-like conditions and enables several optical diagnostics. Several boundary conditions were carefully analyzed and finally the influence of straight oil on the injection system and atomization were investigated in cold pressurized ambients. The numerical part consisted of the implementation of a spray model as sub-model for an engine simulation tool. The behavior of the model was evaluated for different commonly used diesel and biodiesel surrogates. The conclusions were used to make suggestions for oil surrogates. In a final step, the vaporizing spray model was validated with experiments that were conducted in the constant volume combustion chamber at the Technical University of Eindhoven. The setup conditions were taken as determined by the internationally established engine combustion network (ECN), making the results useful for comparison with similar setups and research at other institutions

Design of an injection system under low pressure and temperature conditions in liquid fuelled micro UAV's

Unmanned air vehicles (UAV’s) today are extensively used for a wide range of applications, from amateur to human to military applications. Electric propulsion is preferred for small UAV’s, while piston engines and gas turbines are used for the bigger ones. The proposed engine in this work covers the midscale for restart able, low budget vehicles (<10kg and 30-200N thrust). Simplicity, durability and manufacturability are the main target goals of the design. The liquid fuelled engine is designed to run on gasoline and ethanol as a fuel and a hydrogen peroxide – water solution as the oxidizer. The advantage of the high energy density of the liquid reactants is counteracted by the difficulty for the ignition of the reactants at low pressures and temperatures, especially at the starting up process. In this work, different nozzles and injection strategies were tested and evaluated under similar conditions that exist at start up of the engine. It has been found that even for reasonable manufacturing process and precision, good atomization can be obtained if a mixture of gas and liquid is premixed prior to injection. This can be realized by catalytic decomposition of the hydrogen peroxide without the need for an extra gas supply circuit. This exothermal reaction provides the additional advantage of injecting a hot mixture in the cold combustion chamber, allowing easier ignition

Fuel injection temperature determination and effect on the injection process for different alternative fuels

The influence of the fuel temperature on injection using a pump-line-nozzle system of a medium speed diesel engine was studied for different fuels. The impact of the temperature was significant, suggesting that accurate knowledge of the injected fuel temperature is necessary in order to provide quantitative spray data. The experiments are performed in a constant volume combustion chamber with temperature control of the chamber and the injector cooling. The injector is both in contact with the chamber walls and injector cooling, resulting in a temperature gradient inside the injector. A method to correlate the fuel temperature with chamber and injector cooling temperature is proposed resulting in increased accuracy for the injected fuel temperature

Alternative fuels for spark-ignition engines: mixing rules for the laminar burning velocity of gasoline-alcohol blends

Experimental measurements of the laminar burning velocity are mostly limited in pressure and temperature and can be compromised by the effects of flame stretch and instabilities. Computationally, these effects can be avoided by calculating one-dimensional, planar adiabatic flames using chemical oxidation mechanisms. Chemical kinetic models are often large, complex and take a lot of computation time, and few models exist for multi-component fuels. The aim of the present study is to investigate if simple mixing rules are able to predict the laminar burning velocity of fuel blends with a good accuracy. An overview of different mixing rules to predict the laminar burning is given and these mixing rules are tested for blends of hydrocarbons and ethanol. Experimental data of ethanol/n-heptane and ethanol/n-heptane/iso-octane mixtures and modeling data of an ethanol/n-heptane blend and blends of ethanol and a toluene reference fuel are used to test the different mixing rules. Effects of higher temperature and pressure on the performance of the mixing rules are investigated. It was found that simple mixing rules that consider only the change in composition are accurate enough to predict the laminar burning velocity of ethanol/hydrocarbon blends. For the blends used in this study, a Le Chatelier's rule based on energy fractions is preferable because of the similar accuracy in comparison to other mixing rules while being more simple to use

Failure behaviour of preloaded API line pipe threaded connections

This paper reports on numerical and experimental work concerning the fatigue behaviour and sealing capacity of threaded pipe connections (1” API Line Pipe). Numerical simulations are performed using Abaqus® in combination with ThreadGen©. The fatigue life of a thick-walled standard coupling is determined using a four-point bending test. The corresponding S-N curve is compared to results of previous work on thin-walled specimens. It can be concluded that the standard thick-walled connection has a higher fatigue life than thin-walled ones. In future work, the prediction of fatigue life using established multi-axial criteria will be evaluated. Further, the sealing capacity of several couplings will be investigated by submitting them to different combinations of internal pressure and axial force. Hereto, a specific test setup is designed. The results will then be presented as a test load envelope