PERFORMANCE, EMISSION AND COMBUSTION STUDIES OF A RENEWABLE DIESEL IN A COMPRESSION IGNITION ENGINE

Abstract

India is a developing country and major parts of its transportation, agriculture, and energy sectors are all diesel-dependent. The exhaust gases emitted by the combustion of diesel fuel have led to an increase in airpollution and global warming. These exhaust emissions have affected the lives of animals and humans innumerous ways. Extensive research has been done on alternative fuels, biodiesel being a common one. However, due to biodiesel’s limitations, it cannot replace diesel in existing CI engines. All over theworld, researchers, academicians, and industrialists are exploring alternative fuels, which can be sustainable in such a way that they can replace diesel as fuel. Renewable diesel is such a fuel, which isproduced from non-edible vegetable oil undergoing hydroprocessing at high pressure and temperature in presence of a catalyst. The molecular structure of renewable diesel is similar to diesel. Renewable diesel can use the same pipeline infrastructure as is used for diesel fuel. It is also called a ‘drop-in fuel’. The objective of the present research work is to produce renewable diesel by hydroprocessing. Thecatalyst used during the hydroprocessing process was chosen as manganese, cerium promoted ruthenium-based catalyst supported on Al2O3. Various blends of diesel and renewable diesel and ternaryblends of renewable diesel, diesel, and ethanol were prepared in different proportions and their performance, emission, and combustion characteristics were compared to the baseline data of conventional fuel, diesel. Percentage of ethanol was limited to 15% due to its insolubility in diesel fuel.Physicochemical properties like kinematic viscosity, density, cold flow properties, cetane index, etc. were evaluated and found suitable for use as per ASTM D standards. Response surface methodology (RSM) optimization technique was implemented to study various response variables like brake thermal efficiency (BTE), carbon monoxide (CO), unburnt hydrocarbon (HC), nitrogen oxide (NO) emissions, and smoke opacity by using input factors like Performance, Emission and Combustion Studies of a Renewable Diesel in a Compression Ignition Engine P a g e | viii brakemean effective pressure (BMEP) and percentage of renewable diesel and ethanol by volume in diesel. For getting the most accurate solutions, a face-centered model of Central Composite Design (CCD) was chosen. This helps researchers predict results very precisely with fewer experiments to be conducted. The results obtained from RSM were validated with experimental data. RSM optimizer toolshowed that 30% of Renewable diesel and 7% of ethanol at BMEP of 2.6 bar can give optimized output.The predicted values for BTE, CO, HC, NO, and smoke were found to be 29.21%, 5.5g/kWh, 4.32g/kWh, 4.47g/kWh, and 19.46% respectively. Renewable diesel was mixed with diesel from 10% to 50% by volume and was named D90R10, D80R20, D70R30, D60R40, and D5050. The results for renewable diesel (R100) and diesel (D100) blends indicate that with an increase in the percentage of renewable diesel, brake thermal efficiency decreases. There is a decrease of 16.7%, 3.51%, 6.35%, 8.66%, 10.91% and 12.65% of BTEfor R100, D90R10, D80R20, D70R30, D60R40 and D5050 respectively. In addition, the heat release rate (HRR) for diesel fuel is more than for renewable diesel and its blends. This is because of the earlier ignition of renewable diesel. Exhaust emissions like CO, HC, and smoke opacity are found to decreaseup to 30% blend, after which it increases. At full load, there is a decrease of 5.79%, 10.31%, and 14.47%in HC emissions for R10D90, R20D80, and R30D70 blends. For CO exhaust emissions, 5.09%, 9.55%,and 13.38% decrease until renewable diesel is up to 30% of the blend. Beyond 30% renewable diesel in a blend, the percentage of CO exhaust emissions starts increasing. NO emissions were lower for all blends than diesel. The lowest NO emission for neat renewable diesel is 3.1014 g/kWh which is 23.2%lesser than that emitted by diesel fuel. At full load, smoke opacity was lowest for R30D70 which is 54.1% than that of diesel which was 62.4%. It was observed that R20D80 gave better BTE and D70R30 gave lesser emissions. Keeping Performance, Emission and Combustion Studies of a Renewable Diesel in a Compression Ignition Engine P a g e | ix these two blends into consideration and to improve the shortcomings of both, ethanol was added. 5%, 10% and 15% of ethanol were blended with 20% and 30% of renewable diesel. The experiments concluded that HRR increased with a n addition of ethanol due to a low cetane index which increased ignition delay. Values of HRR for ternary blends were found to be more than diesel. BTE increased with an increase in the percentage of ethanol till E10. Beyond E10, BTE decreased. R30E15 has the least BTE of 23.8% on full load which is 24.8% lesser than diesel fuel. With an increase in the percentage of ethanol, HRR increased. At full load, the maximum HRR for R20E15 was 61.74J/°CA whereas, for D80R20 it was 50.16J/°CA. With an increase in addition of ethanol pressure also increased. Ethanol percentage up to 10% by volume in a blend is acceptable as otherwise, it can lead to a further decreasein the BTE. This is due to the lower calorific value of both renewable diesel and ethanol. Low calorificvalue also leads to more consumption of fuel with an increase of renewable diesel and ethanol percentage in a ternary blend. With an increase in the percentage of ethanol, CO and HC emission increases however, CO emissions are lesser than diesel. Moreover, with an increase in ethanol percentage smoke opacity and NO decreases. Ternary blend R30E10 has the lowest NO and smoke emissions. NO and smoke opacity were reduced by 24.25% and 20.35% respectively.