SOME STUDIES ON NANO-PARTICLES DOPED ALTERNATIVE FUELS IN UNMODIFIED CI ENGINE

Abstract

Diesel fleets, the most efficient prime mover, plays a transformative role in powering the world economy. However, the undue reliance on petrodiesel, coupled with alarming environmental concerns, are severely threatening its existence. Across all, agriculture will be the sector most vulnerable to the transition of existing diesel engine technology. These engines fulfill more than 60% of the total energy demand of the farmlands worldwide. Biodiesel

derived from inedible sources can be a productive approach, especially for an agricultural- driven economy like India, rich in biodiversity and has more than 47,000 oil-bearing plants. It

can revolutionize the agriculture sector to a whole new level by imparting new life to the millions of existing diesel engines. In view of this, the present study highlights the potential of underutilized inedible oil biodiesel, Schleichera oleosa, as a promising renewable fuel for stationary light-duty agricultural engines. However, despite interest in sustainable energy resources is growing sharply, the popularity of the biodiesel economy is relatively low. Several reasons, particularly poor flow properties, lower calorific value, sensitivity to cold weather conditions, inadequate shelf life, engine incompatibility and higher NOx emission, are accountable for this cause, which requires attention. Therefore, in order to encounter the critical issues and stimulate the engine performance of biodiesel blends, the properties of two different nanoparticles, alumina and MWCNT, in the form of additives, have been investigated and utilized in the present research. The primary objective is to identify a propitious fuel borne nano-additive that can simultaneously improve the performance and regulate the harmful emissions associated with the operation of Schleichera oleosa biodiesel blends in farmland-based CI engine. In light of the above, the research effort has been broadly divided into three major sections. In the initial phase of work, the selection and production of biodiesel and nanoparticles were carried out.Subsequently, the biodiesel and nanoparticles produced were characterized with the aid of Gas

Chromatography-Mass Spectroscopy (GC-MS), Scanning Electron Microscopy (SEM) and X- ray diffraction (XRD) spectroscopy techniques, respectively. The first phase of research ended

up by preparing different nano-fuel blends containing (25, 50, 75, 100 and 125) ppm dosage level of nanoparticles. The dispersion of nanoparticles in the base fuel (diesel-biodiesel blend) was achieved with the aid of ultrasonication and addition of arrogate surfactant (Sodium Dodecyl Sulfate). In the second phase of work, the prepared blends of nano-fuels underwent a short/ long-term stability test known as zeta potential measurement and visual inspection to ensure the test fuels were free from agglomeration. The MWCNT dispersed test fuels showed a higher value of zeta potentials than alumina, thus signifying the higher stability of MWCNT nanoparticles in the base fuel and were only considered for further analysis. Also, the visual inspection result of six-month duration showed that nano-fuel blend containing 125 ppm dosage showed aggregation at a lower temperature (10o

C). Thereafter, the physico-chemical properties of the nano-fuel blends such as density, viscosity, calorific value, cetane index, etc. were evaluated as per relevant ASTM standard methods. The properties of nano-fuel blends were well-within range and comparable to neat diesel; the value of calorific value, cetane index, flash point, and cold flow properties were higher than diesel-biodiesel blend (D80B20). The final phase of work includes evaluation of ignition probability, spray and engine characteristics of nano-fuels by undergoing trials on hot-plate, Malvern spraytec and 3.5 kW Kirloskar make single-cylinder, direct injection CI engine setup. The results obtained were compared with the biodiesel blend (D80B20) and neat diesel (D100). Due to increase in thermal conductivity with respect to temperature and shorter wavelength of nanoparticles, the nano-fuel blends showed higher ignition probability among all the fuels. Interestingly, the droplet size of nano-fuels was also comparable to neat diesel and smaller than diesel-biodiesel blend with D80B20C75S3 exhibiting the lowest sauter mean diameter i.e., (15.1μm) among all the nano-fuel blends. The engine performance also showed an overall increase of upto 6.7% in brake thermal efficiency and upto 10.2% reduction in brake specific energy consumption with the addition of 75 ppm dosage of MWCNT nanoparticles as compared to D80B20 blend. Moreover, due to efficient atomization, excellent reactivity and thermal properties, the combustion characteristics of all the nano-fuel were also significantly improved. The ignition delay was reduced to 7.9o for D80B20C75S3 from 14.1o for D80B20 blend whereas the peak heat release rate showed upto 11% rise for D80B20C75S3 as compared to D80B20 blend. The

exhaust emissions were also found to be (5-45%) lower when engine was operated with nano- fuel blends, most importantly NOx emission showing an overall decrease of upto 22.8% with

the addition of 125 ppm dosage of MWCNT nanoparticles in D80B20 blend. Lastly, as the consequence of exhaustive experimental results, RSM based multi-objective model was constructed to calculate the optimal dosage of MWCNT nanoparticle to be dispersed in the base fuel. Thus, findings from the present research confirm that utilizing nanoparticles' strength as a fuel additive for biodiesel blends can be a great leap forward in the fuel reformulation realm. As, it can play a decisive role in preserving the existing diesel engine technology in certain ways.