Recently, there has been an exponential growth in research and innovation in the natural fiber composites (NFC) due to their diversified applications in the field of engineering. Biodegradability, light weight, formability and availability at low cost are the attractive merits of the natural fibers. Mechanical, Thermal and Machinabilty properties of Natural fiber composites have their own advantage and adoptability in the field of automobile, power plants, aeronautical, defense and naval applications. This review aims to provide an overview of the comparison of differ types of Natural fiber composites, factors that affect the mechanical, thermal and machinabilty of NFCs and their engineering applications.

Biodiesels are alternative fuels for petroleum-based diesel without major modifications of engine. In the environmental aspect, also biodiesel gives fewer pollutants than petroleum diesel. However, the NO x level is slightly higher. To reduce NO x , some of the methods are being used, which include direct injection, turbocharging, air-to-air intercooling, combustion optimization with and without swirl support, multivalve cylinder head, advanced high pressure injection system, i.e., split injection or rate shaping, and electronic management system. However, technologies such as exhaust gas recirculation ͑EGR͒, soot traps, and exhaust gas after treatment are gaining emphasis to cater to the challenges posed by increasingly stringent environmental emission legislations. In this work, experimentation was conducted on a single cylinder diesel engine with mahua methyl ester ͑MME͒ in the neat form along with the cooled EGR and performance, combustion pressure, and emission parameters are collected by using suitable instrumentation. Same experimentation was repeated for the petroleum diesel and a comparison was made to evaluate the applicability of MME along with EGR without major modifications. After the analysis of results, it was found that 5% EGR is recommendable with neat biodiesel ͑MME͒ run, and in most of the situations, it proved its merit over neat diesel run.

In many countries, methyl esters of vegetable oils are blended with petroleum diesel and used as a partial substituent to petroleum diesel. In our experimentation, neat cotton seed methyl ester (without blending) was implemented as fuel for a direct injection compression ignition engine. Cotton seed methyl ester cetane number and calorific value are close to petroleum diesel. But the flash point, auto-ignition temperature and viscosity are higher than petroleum diesel. If it is preheated, the viscosity will decrease and flow ability in the fuel lines will increase. While injecting, the atomization level of the fuel was also improved by the preheating. But too much heating is not preferable, because it causes formation of vapors in the fuel lines. Preheating of methyl ester to the correct temperature gives better thermal efficiency and lower environmental pollution. Hence in our investigations, cotton seed methyl ester is preheated to different temperatures (27 C, 35 C, 40 C, 45 C, 52 C and 55 C) and implemented as fuel for a direct injection compression ignition engine. At these temperatures, engine performance, fuel combustion and pollutants in the exhaust gas are analyzed. It was found, preheating of cotton seed methyl ester to a temperature between 45 C and 52 C gives lower pollutants and better thermal efficiency.

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