A natural gas fueled homogeneous charge compression ignition (HCCI) engine is coupled to an exhaust gas operated turbine driven two-phase ejector cycle to generate power and cooling energy, simultaneously. By establishing a thermodynamic model, the simulation of the proposed system and its parametric analyses are conducted. Energetic and exergetic investigations are carried out to study the role of equivalence ratio, engine speed, condenser temperature, refrigeration evaporator temperature, air conditioning evaporator temperature, and ejector nozzle efficiency on the thermodynamic performance parameters of the combined cycle. The analysis of two-phase ejector cooling cycle using three working fluids including R717, R290, and R600a is conducted. Results reveal that the thermal efficiency of HCCI engine is increased from 47.44% to 49.94%, and for the R600a operated combined cycle it is increased from 60.05% to 63.26% when the equivalence ratio is promoted from 0.3 to 0.6. Distribution of fuel exergy results show that out of 100% exergy input, in case of R717 operated combined cycle, 139.79 kW (38.72%) is the total exergy output and 164.21 kW (45.49%) and 57 kW (15.79%), are the values for exergy destruction and exergy losses. It is further shown that change in refrigerant minorly influence the percentages of exergy distribution.

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The fuel composition highly affects formation of toxic pollutants in a diesel engine. The aromatics are found to be prominent fuel components that affect pollutant formation and at the same time help provide lubricity to moving engine parts. Therefore, their effect needs to be addressed systematically. This article elucidates aromatic types and its content effects on fuel atomization, regulated and unregulated emissions. Acoustic emission signals were also recorded for engine noise diagnosis during the exhaustive testing. Five different aromatics namely, ethylbenzene, α-methylstyrene, indene, tetralin and methylnaphthalene were blended in ratio of 15, 20 and 25% by mass with dearomatized hydrocarbon fuel and tested in a compression ignition engine. Results reveal that unregulated emissions, carbon monoxide (CO), unburnt hydrocarbon (HC) and particulate matter (PM) increase with aromatic content. However, nitrogen oxides (NO x ) and acoustic emissions were found to be maximum with low aromatic content (15%). The polycyclic aromatics (indene, tetralin and methylnaphthalene) produce higher polyaromatic hydrocarbons (PAHs) and carbonyl emissions compared to monocyclic aromatics (ethylbenzene, α-methylstyrene). Additionally, polycyclic aromatics with 20% blending produced higher PAHs and carbonyl compound emissions than diesel with 23.6% aromatics. Ethylbenzene showed significantly better results for both spray and emission characteristics compared to the other tested aromatics.

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