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In the light of major research work carried out on the detrimental health impacts of ultrafine particles (<50 nm), Euro VI emission standards incorporate a limit on particle number, of which ultrafine particles is the dominant contributor. As Compressed Natural Gas (CNG) is a cheaper and cleaner fuel when compared to diesel, there has been a steady increase in the number of CNG vehicles on road especially in the heavy duty segment. Off late, there has been much focus on the nature of particle emissions emanating from CNG engines as these particles mainly fall under the ultrafine particle size range. The combustion of lubricant is considered to be the dominant source of particle emissions from CNG engines. Particle emission due to lubricant is affected by the oil transport mechanisms into the combustion chamber which in turn vary with engine operating conditions as well as with the physico chemical properties of the lubricant.

In this paper, experimental evaluation was carried out on a 6.0 L heavy duty CNG engine which has been optimized for 18 percent hydrogen blended CNG (HCNG). Optimization test results shows that use of HCNG results in reduced CO, THC & CH4 emissions by 39, 25 & 25 percent respectively and increase in NOx by 32 percent vis-a-vis CNG. After optimization the engine was subjected to endurance test of 600 hours as per 15 mode engine simulated city driving cycle with HCNG. The performance & emission characteristics of the engine were analyzed after completion of every 100 hours as per European Transient Cycle (ETC). Test results indicate that there were no significant changes observed in engine power output over the complete endurance test of 600 hrs with HCNG. Specific fuel consumption (SFC) measurements were consistent at all the 15 modes of engine simulated city driving cycle.

Depletion of fossil fuel reserves, the unsteadiness of their prices and the increasingly stricter exhaust emission legislation put forward attention of world towards use of alternate fuels. The ever increasing demand for ecologically friendly vehicles can be met by use of clean fuels like Compressed Natural Gas (CNG) and Hydrogen (H2). Lower carbon to hydrogen ratio of CNG makes it a cleaner fuel, due to this CNG is gaining popularity as an internal combustion (IC) engine fuel in transport sector. Hydrogen fuel for IC engines is also being considered as a future fuel due to its simple carbon less structure. However, several obstacles have to be overcome before widespread utilization of hydrogen as an IC engine fuel can occur in the transport sector. The 18 percent hydrogen enriched CNG fuel referred to as HCNG has the potential to lower emissions and could be considered a first step towards promotion of a Hydrogen economy.

In this paper, the characteristics of particle size distribution in the exhaust of a turbocharged 5.9 liter Cummins gas engine lubricated by two commonly used oils of different viscometrics (15W-40 and 20W-50) have been investigated. The study also attempts to differentiate the performance of the lubricants on the basis of fuel economy. A test procedure developed in- house was used for the evaluation, wherein the engine was operated at various speeds (1200-2800rpm) and load (25 %, 50% & 75%) conditions. Particle size distribution is measured using Engine Exhaust Particle Sizing Spectrometer (TSI EEPS Model 3090). Results indicate that a majority of the particle emissions are observed in the nucleation region (particle diameter < 50nm) and particle size distribution is found to significantly vary with engine speed.