4. Tribological aspects associated with binary fuel blends

There are two different types of tribological studies available in the literature for binary fuel compatibility in engines, that is, short-term bench tests and long-term endurance test. Before conducting the endurance test, some bench tests on four ball tester (FBT), high frequency reciprocating rig (HFRR), and pin on disc tester (POD) were carried with binary fuel blends to endow the convenient basic information about the fuel lubricity behavior, effect of oxidative stability, and engine oil dilution. The effect of temperature and load on friction and wear were investigated with the help of FBT [4]. As biodiesel is subjected to oxidation and has highly affected lubricity at higher temperature and load, so the effect of oxidation was also studied. The effect of dilution in lubricating oil was also evaluated by means of HFRR and POD friction monitor [5]. The effect of engine oil dilution on pin and disc as well as on cam and tappet in valve train combination were studied. The effect of binary fuel blend on injection system of engine was also discussed by Singh et al. [22]. Result revealed that biodiesel and its oil blends show improved lubricity as compared to diesel, and hence increase the life of injection system of the engine.

compared to original conditions. This is also due to the fact that air move in during the suction stroke at higher CR is compressed, which escalates the air temperature. Higher air temperature helps for better atomization of fuel which improves fuel combustion inside the combustion chamber. But NOx emissions increase at higher CR as compared to original conditions. This is due to the higher temperature inside the combustion chamber at higher CR conditions as compared to original CR conditions. This is also due to the higher oxygen contents in the biodiesel-oil blends which improves combustion and hence increases NOx formation. The exhaust gas temperature also found to be higher due to the higher intake temperature and then better combustion rate. Similarly, Dubey and Gupta [19] had also altered CR with the aim of better performance of binary fuel blends in diesel engines. They found that the JB50TO50 gives the better result as compared to other blends and BTE efficiency improved by 2.17% a full load condition and higher CR. The tailpipe emissions CO, HC, and NOx, and smoke opacity were decreased by 13.04, 17.5, 4.21, and 30.8%, respectively, while there is some increment was noticed in CO2, that is, 11.04%. Overall, they stated that JB50TO50 has better

Fuel IT is undoubtedly an important parameter that influences the combustion, performance, and emission characteristics of any diesel engine. Advanced IT results in increase in maximum cylinder pressure and heat release rate, while the reverse trend is noticed in the case of retarded IT. Ignition delay was found to be longer with shorter combustion duration at advanced IT as compared to that with the original and retarded ITs. BSEC at advanced IT is lower than that with the original IT. Advancing the IT results in reduced CO, HC, and particulate emission. This is due to the fact that more time is being available for the complete combustion in the case of advanced ITs. NOx emission was higher at the advanced IT in comparison to that with the original IT and lower at retarded IT compared to original and advanced ITs. This is due to the fact that at retarded IT, fuel is injected near the top dead centre (TDC) and most of the fuel burn after TDC. It causes higher amount of heat going to the exhaust which results in lowering of maximum cylinder pressure and temperature [20].

Sharma and Murugan [21] used JB50TPO50 as a fuel at altered IP conditions. Outcome revealed that the IP up to 220 bar gave good engine performance as compared to those of original IP and also 230, 240, and 250 bar. At 220 bar IP, the BTE was found to be higher. HC and CO emissions were also lower at this IP as compared to original IP at full load. The smoke

There are two different types of tribological studies available in the literature for binary fuel compatibility in engines, that is, short-term bench tests and long-term endurance test. Before conducting the endurance test, some bench tests on four ball tester (FBT), high frequency reciprocating rig (HFRR), and pin on disc tester (POD) were carried with binary fuel blends

option at higher CR condition as a fuel for CI engines.

132 Biofuels - Challenges and opportunities

opacity was lower at full load compared to original IP.

4. Tribological aspects associated with binary fuel blends

The outcome of the four ball tester gives an idea about the impact of binary fuel blend used in the experiment on wear and friction under different operating conditions. The operating loads and temperatures were 147–392 N and 45–60–75C, respectively. The changes in load and temperature highly influenced the wear and friction between sliding surfaces. Higher load and higher temperature adversely affect the tribological performance of the used feedstocks. The existence of both abrasive and adhesive wear has been observed at this condition, while only abrasive wear occurred at low temperature and load condition. The oxidation of methyl ester blends at higher loads and temperature conditions lead to higher corrosive wear. However, the aged (oxidized) methyl ester shows better results in terms of lubricity in short-term test [4].

The effect of 10% dilution of fresh AB70EU30 oxidized AB70EU30 and diesel by volume in the engine oil by means of HFRR and POD. The results revealed that the 10% dilution AB70EU30 showed promising results after dilution with lubricating oil as compared to diesel and oxybiodiesel and provided much smoother mating surfaces. It is due to the existence of palmitic acid, tocopherol, etc. in the biodiesel and oil blend [23]. The lubricating oil diluted with oxybiodiesel shows higher COF and WSD as compared to fresh biodiesel contaminated lubricating oil. This is because of complex interactions between polar molecules of anti-wear additives and biodiesel after the oxidation. This shows the poorer results as compared to fresh biodiesel but rather it is better than diesel. AB70EU30 diluted lubricating oil shows lower change in the value of total acid number (TAN) after the test as compared to diesel contaminated lubricating oil. This also justified the better condition of the lubricating oil after the dilution of AB70EU30. The ferrography also showed the less wear debris in the AB70EU30 contained lubricating oil. In modern diesel engine, additional late in-cylinder injection strategy is implemented to raise the EGT in order to check the particulate emission. During late injection, piston moves toward BDC exposing more cylinder surface area to the fuel, causing lubricating oil dilution as fuel readily passes through to the crankcase [24]. Crankcase dilution can decrease viscosity and lubricity of engine lube oil, and at the same time, it can diminish the performance of anti-wear additives. Sharma and Murugan [25] have assessed the use of 20% tyre pyrolysis oil with 80% Jatropha oil methyl ester in CI engine for long term, that is, 100 hrs. They reported that the deposition of carbon on injector tip and inside the combustion chamber was higher for this blend. But, they did not find any problem with the use of JB80TPO20 for 100 hrs in diesel engine with modified conditions.
