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The thermal performance of an ammonia-water-hydrogen absorption refrigeration system using the waste exhaust gases of an internal combustion diesel engine as energy source was investigated experimentally. An automotive engine was tested in a bench test dynamometer, with the absorption refrigeration system adapted to the exhaust pipe via a heat exchanger. The engine was tested for different torques (15 N.m, 30 N.m, and 45 N.m). The exhaust gas flow to the heat exchanger built on the generator was controlled manually using two control valves. The refrigerator reached a steady state temperature between 10 and 14.5°C about 3.5 hours after system start up, depending on engine load. The maximum coefficient of performance was 0.10 obtained for the controlled exhaust mass flow case at torque 30 Nm after 3hrs from system startup.

A semi phenomenological and global chemical kinetic model is adopted and applied to predict soot formation in gasoline-fueled spark ignition engines. The adopted model considers acetylene produced from gasoline pyrolysis process as the main precursor for soot inception. The adopted soot model was initially proposed for diffusion flames and this work tries to apply and modify it to gasoline fueled (premixed flame) spark ignition engines. The burned mass fraction and burn rate are used to estimate the instantaneous acetylene, oxygen and Hydroxyl (OH) radical mass fractions at each crank angle of the engine. Experimental data from a single point throttle body injected spark ignition engine is used for validating total particle numbers at different engine operating conditions. The simulation results agree reasonably with the experimental results. Both experimental and predicted results showed that the inception rate increases with the engine load in an exponential form.

The transformation of rapeseed oil into methyl ester through the transestrification process normally produce biodiesel fuel with kinematic viscosity almost double that of the commercial diesel fuel. The bulk modulus of biodiesel is also higher than that for the conventional diesel fuel. In this paper, the effects of the two physical properties on the injection characteristics of Rapeseed Methyl Ester (RME) are discussed. The injection characteristics considered here were namely; nozzle chamber pressure, needle lift, and fuel injection rate. The mutual effects of engine speed and delivery pipe length were also analyzed. A previously developed computer model was used to simulate the injection process of the conventional pump-line-nozzle injection system. An explicit finite difference scheme was adopted to solve the unsteady flow equation within the delivery pipe.

Ignition timing control is a key problem in the conventional spark ignition engine due to the nonlinear nature of its variation with the engine conditions. The problem is much more pronounced in natural gas fueled engines due to the frequent variation of the operating parameters. The variation in the air-to-fuel ratio, gas composition, engine load and speed during engine operation require different spark timings for better engine performance. The ability of neural networks to reasonably handle such a complicated control problem is introduced. The training and testing of the predictor of the optimum spark timing for maximum brake torque (MBT) is conducted. The training was carried out using a large set of experimental data collected from natural gas fueled engine. The obtained predictor is tested and possible causes of robustness problem are discussed. The predicted MBT spark timing is compared with a different set of experimental data for the same gas fueled engine.

The characteristics of the combustion process in an improved design of a novel spark ignition engine studied by means of Computational Fluid Dynamics are presented. The engine is designed to work at low average combustion temperatures to achieve very low NOx emissions. The engine is a two-stroke, two piston in-line engine. The main combustion occurs in four combustion pre-chambers that have an annular shape with a nozzle on the side facing the cylinder. Fuel is directly injected into the pre-chambers by using high-pressure fuel injectors. A progressive burning process is expected to keep the flame inside the pre-chambers while the fast ejection of combustion products should produce effective mixing with the cold air in the cylinder. This fast dilution should guarantee a temperature drop of the combustion products thus reducing the formation of NOx via a thermal path.

The wider flammability limit of lean natural gas-air mixtures offers potential for operating spark ignition engines on lean air-to-fuel ratios. However, at very lean equivalence ratios, the development of the initial flame and its subsequent propagation becomes highly sensitive to physical and chemical state of the mixture. This in turn, can adversely affect engine performance, particularly the cyclic variation in the combustion process. This paper discusses the effects of lean-burn operation on the flame development durations and the cycle-by-cycle variations in a natural gas fuel injected engine. The study was conducted on a 8-cylinder, 4.6 liter, spark-ignited engine. A data acquisition system is used to acquire 300 consecutive in-cylinder pressure cycles. A heat release model was used to estimate the initial flame development time and the rapid burn duration.