LITERATURE REVIEW AND SCOPE OF RESEARCH
2.4 Scope of the Work
Figure 2.22 Variations of engine speed at different engine load (Sahoo et al., 2009b)
Figure 2.23 Comparison of exergy efficiency at different load (Sahoo et al. 2009b)
liquid fuels shortage. The technical issues of these small single cylinder diesel engines that can efficiently utilize biogas are yet to be systematically addressed.
Syngas is ideally a mixture of H2 and CO produced by gasifying a solid fuel feedstock (such as coal or biomass). In its simplest form, syngas is composed of two diatomic molecules CO and H2 that provide the building blocks upon which an entire field of fuel science and technology is based. Over the years, the gaseous mixture of CO and H2 has had many names depending on how it was formed; producer gas, town gas, water gas, synthesis gas, and syngas etc. to name a few. Generally, the volumetric H2/CO ratios of syngas fuels vary greatly depending on the source and the processing technique. The different combinations of H2/CO ratio in syngas affect the efficiency, combustion and emissions of an IC engine when used in dual fuel mode. In the previous literatures, several researchers have conducted tests on various types H2 and CO composition syngas fuels. In these published works, there was more information regarding the type and composition of used gaseous fuels while very little detailed information about engine geometry was mentioned. This makes more difficult to evaluate or analyze the reported results because the engine performance, combustion and exhaust gas emissions depend not only on the properties of the gaseous fuels but also on the characteristics of engines tested. In addition, almost all past investigations were conducted with different engines test benches with controlled engine cooling water and lube oil temperatures to a predetermined value. However, this is contrary to real operational conditions. Including this, as found from the previous literatures, the use of only CO gas as a fuel for CI engines under dual fuel mode is not explored.
The second law analysis provides the knowledge of when and where the available energy is lost or destroyed in the engine system. Evaluation of available energy determines the maximum possible performance of a thermodynamic system. In addition, impact of process change in the system in terms of system losses is also assessed. These findings help in reducing the availability loss to improve the performance of an engine in terms of efficiency and power output. The availability analysis has been used for many years for evaluating stationary systems and automotive engines. However, too little has been done towards the thermodynamic analysis of dual fuel IC engines.
Therefore, to solve the above mentioned problems from previous literatures, the present contribution is focused to perform a systematic experimental investigation including the
thermodynamic behavior of a CI diesel engine under dual fuel mode. The following objectives have been addressed in the present investigation:
• Optimization of engine operating and design parameters.
It is found from several published literatures that the dual fuel operations behave differently to the changes in operating and design parameters. Load is an important operating parameter for dual fuel operations because the engine performance at part load varied remarkably to the medium and high load cases. Again, the characteristics of a dual fuel engine such as, efficiency, ignition delay and emissions vary much to the changes in the fuel composition. Therefore, in this work, various engine parameters such as load, pilot fuel quality and gaseous fuel type, are optimized for minimum emissions and maximum efficiency from the dual fuel operations.
• Maximum replacement of fossil petroleum diesel fuel.
During dual fuel operations fossil diesel, even a small amount, used for pilot ignition of gaseous fuels, have the shortcomings of emitting of air pollutants. Hence, to reduce dependence on foreign petroleum fossil fuels and mitigate GHG emissions, a diesel like fuel, bio-diesel, is employed in this work as the fuel-gas ignition source.
• Energy and exergy analysis for dual fuel engine operation.
The performance characteristics of dual fuel modes are quite different to the diesel mode. To have the knowledge of energy losses whereabouts the combined energy and exergy analyses are added to this research program. Whether the dual fuel mode efficiency able to surpasses the diesel mode efficiency? The availability analysis will able to determine this for both the systems. In addition, impact of changes in the design and operating parameters of the dual fuel system in terms of system losses can also be assessed. These findings will help in reducing the availability loss to improve the performance of the engine in terms of efficiency and power output.
• CDM potential of CI diesel engines using gaseous fuels under dual fuel operation.
The principal aim of this research program is to pull through diesel engines from their greenhouse gas emissions of CO2 and CH4. To satisfy this, the two utilized alternative gaseous fuels have to qualify their potential towards clean development mechanism under dual fuel mode. Hence, this important investigation of the biogas and syngas dual fuel operations is to be executed to meet the aim of this research work.