George M. Kosmadakis

Comparative Evaluation of Ethanol, n-Butanol, and Diethyl Ether Effects as Biofuel Supplements on Combustion Characteristics, Cyclic Variations, and Emissions Balance in Light-Duty Diesel Engine

AbstractThis work evaluates experimentally on a comparative basis the effects of using three customary biofuels on the cyclic variability (irregularity) of combustion and emissions balance in a single-cylinder, light-duty, direct-injection diesel engine run at three loads. Blends of fossil diesel with up to 15% (by volume) ethanol and 24% n-butanol or diethyl ether (DEE) are investigated. Related experimental study including heat release diagrams reported by the authors for these blends in the same engine disclosed the differentiation in performance and emissions of these biofuel blends from running the engine with neat fossil diesel. Given that low ignition quality fuels, as the present biofuels, mainly at high blending ratios may give rise to unstable engine functioning and hence detrimental performance, this work examines on a comparative basis the strength of combustion cycle-to-cycle variations as revealed in the measured cylinder pressure diagrams. The latter are analyzed with respect to maximum pre...

Renewable and Conventional Electricity Generation Systems: Technologies and Diversity of Energy Systems

In this chapter, the primary technical aspects of conventional and renewable energy systems are presented. The description focuses on commercial systems installed across the world, together with a brief introduction to some promising technologies currently under development, such as Carbon Capture and Storage (CCS). Conventional energy systems include power plants using fossil fuels (natural gas, coal, etc.), while renewable energy systems include solar, wind, geothermal, biomass, and small-hydropower applications. These technologies are briefly described accompanied by economic figures (installation cost, fuel cost, specific cost of electricity, etc.) and emissions data (where applicable). Some insight on the energy strategy in specific countries is provided and how this can be related to local conditions and electric power requirements.

Combustion Analysis of a Spark-Ignition Engine Fueled on Methane-Hydrogen Blend with Variable Equivalence Ratio Using a Computational Fluid Dynamics Code

AbstractThe main scope of the present work is to examine the combustion processes inside the cylinder of a spark-ignition (SI) engine fueled with a methane-hydrogen blend with variable equivalence ratio. This combustion analysis is conducted with a computational fluid dynamics code, which is an in-house code and has been initially developed for simulating hydrogen-fueled SI engines. Lately, its combustion model has been extended with the introduction of methane fuel and various routes are used for the calculation of the nitric oxide (NO) emissions. The first task is to conduct the validation of this code, focusing on this newly developed combustion model. This validation is based on both performance and emissions comparison with experimental data, in order to gain a complete view of the code capabilities. The available experimental data are from a two-cylinder SI engine with complete sets of measured values. For the current study, it was decided to focus on the effect of the equivalence ratio (from 0.7 up...

Spark-Ignition Engine Fueled with Methane-Hydrogen Blends

The motivation of the present work is first to conduct the validation of a Computational Fluid Dynamics (CFD) code, for different methane-hydrogen fuel blends in a spark-ignition (SI) engine, focusing on the newly developed combustion model. This validation is based on both performance and emissions comparison with experimental data, in order to gain a complete view of the code capabilities. Then, a detailed combustion analysis is conducted, by further processing the results of the numerical code, providing insight of the flame front propagation and emissions production inside the engine cylinder. The available experimental data are from a two-cylinder SI engine with complete sets of measured values. For the current study it has been decided to focus on the effect of variable hydrogen content (from 0 up to 50% by vol. hydrogen). The CFD code is an in-house code and has been initially developed for simulating hydrogen-fueled SI engines. Lately, its combustion model has been extended with the introduction of methane fuel and the reaction rates are calculated with the characteristic conversion time-scale method, while the flame front is tracked using a laminar and turbulent combustion velocity. The nitric oxide (NO) emissions are calculated according to the widely-used Zeldovich mechanism. The CFD code validation includes the comparison of calculated performance values (pressure history and heat release rates) with the measured ones for variable hydrogen content. The calculated NO emissions are also compared with the measured ones for the same conditions. From this comparison it has been revealed that a good match exists for both performance and emissions, showing that the code can be applied for detailed investigation of such combustion processes. Finally, a detailed combustion analysis is implemented with the support of the measured data, in order to examine the combustion processes and flame propagation for the different fuel blends.