Tightening of emission norms necessitate intensified research in the field of emissions reduction. Fuel research opens up a vast area of potential improvement, since combustion behavior and the nature of the combustion products can be heavily influenced by fuel composition. In this paper, the effects of fuel properties on combustion and emissions shall be discussed, based on the study of standard diesel fuel, two types of diesel-like fuels and a kerosene fuel. Investigations were conducted on a single cylinder heavy duty direct-injected diesel engine operating under part-homogeneous combustion in the part-load operating range. For this purpose, a statistical design of experiments method (DOE) was utilized in order to evaluate the influence of each fuel property and, thus, develop a model for all selected fuels. Variation in EGR rates, injection and air patterns have significant effects on the combustion in the fuels under investigation. Therefore, common DOE plans with the same engine DOE parameters and ranges have been considered for all investigated fuels. On the other hand, the centroid of combustion was maintained constant for each operating point for all the fuels, to have the same evaluation basis. This investigation contains the experimental results obtained at the test cell, followed up with heat release calculations, to analyze combustion rates. Based on these investigations, the impact of the different fuels on the efficiency and raw engine emissions shall be discussed. Results show the potential of each fuel, based on its physical and chemical properties. Kerosene, with its high volatility and zero aromatic content appears desirable for application in heavy duty diesel engines. Further, part homogeneous combustion offers a possibility to reduce the amount of exhaust after-treatment.
Locomotive engines are emitting high levels of exhaust gas emissions and substantial amount of particulates which is thought to have significant global warming potential. In the past years locomotive regulations have been implemented in the United States to control the emission in this application. Also it can be observed that engine emitted carbon dioxides (CO2) will be limited soon for all on-road engine categories to meet the Green House Gases (GHG) norms.
Tier 4 standards apply to locomotives since the beginning of 2015 for newly built or remanufactured engines. NOx and particulate limits have been reduced by around 70% compared to the Tier 3 standards requiring significant advancements in engine technology and / or exhaust aftertreatment solutions. EGR technology is an option to reduce NOx emissions to Tier 4 locomotive standards indeed of its impact on engine fuel consumption as well as the emitted CO2 gas, which may be controlled either by future CO2 or fuel consumption standards.
To cope with this challenge, new engine technology concepts need to be developed. A waste heat recovery system is a beneficial solution to recover the wasted energies from different heat sources in the engine. Especially the considerable amount of exergy in the exhaust gas (EGR and tailpipe), which results from its high temperature and mass flow, has significant recovery potential. By utilizing a waste heat recovery system a portion of this exergy can be converted into a usable form of power, which then will increase the effective power output of the engine system. A major challenge is to recover the wasted exhaust energy with the maximum possible system efficiency. In a Tier 4 locomotive engine, heat from the EGR system as well as the tailpipe waste heat can be recovered by using an Organic Rankine Cycle (ORC) waste heat recovery system.
This paper will discuss the results of a waste heat recovery (ORC) system evaluation for locomotive applications. With the help of thermodynamic calculations the incremental power from ORC system as well as the fuel economy benefit will be evaluated and discussed. Additionally, a reasonable working fluid and the system layout, which are considered for thermodynamic calculations, will be reviewed.
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