ANFIS technique for handling vibration characteristics of a diesel engine fueled by hybrid biodiesel-natural gas

The importance of energy and its role in economics and politics in today's world is quite clear. This subject is important for both the advanced industrialized countries which are the major energy consumer and the oil-producing countries [1]. Nowadays, the most important source of energy in the transportation, industry, agriculture, and household sectors is fossil fuels and their derivatives [2]. Based on reports from the U.S. Energy Information, the transportation sector is one of the major consumers of diesel fuel in the world which can emit a significant volume of pollutants. These concerns led to the production of low-emission alternative fuels with pollution and environmental damage. Diesel engines are more efficient and more cost-effective compared to spark-ignition engines. They are also safer, as diesel fuel is less volatile than other fuels such as gasoline and natural gas which are used in spark-ignition engines, and also its steam is less explosive. Unlike gasoline engines, especially for heavy duties, diesel engines operate well and efficiently compared with spark-ignition engines, so they are ideal for the use of ships, trucks, buses, railroads, and locomotives [5]. The use of biodiesel has to improve the engine performance and reduce emissions, otherwise, there is no justification for using alternative fuels [17]. This led researchers to apply fuel additives in order to improve the disadvantages of biodiesel and diesel fuels. Some additives including metal-based additives [18-20], ethanol and methanol as alcohol [21, 22], CN improvers [23], and emulsifiers [24] have been employed to improve the NOx emission in a diesel engine fueled with biodiesel. In dual fuel technology systems, NG-air pre-mixture takes into the combustion chamber and starts the combustion process by the injection of pilot fuel.
NG benefits a higher compared with that diesel fuel. This protects NG from self-ignition which needs a comparison ratio higher than 1:40 [25]. Biodiesel as pilot fuel helps for improving the pilot fuel condition. Otherwise, there is no justification for using alternative fuels. The present study wants to look into the effects of engine load, NG fraction, and biodiesel blends in dual-fuel combustion in the presence of NG, diesel, and biodiesel on engine vibration. This trend also wants to employ the ANFIS technique as a hybrid ML technique for the prediction of total engine vibration. To our best knowledge, this study can be the first study for the employment of the ANFIS for handling a CI engine vibration fueled by Diesel-biodiesel-NG which the results could be interesting to researchers who are studying for finding the best fuel sample for reaching a sustainable and proper engine performance. In this study, Biodiesel was produced through a trans-esterification process from WCO as an available and low-cost source. Differences in the values of the impact Factors like the amount and type of catalyst and alcohol and processing time and temperature strongly affect the production yield. The amount and type of factors were selected from the study by Faizollahzadeh et al [9] which the maximum biodiesel production yield (98.46%) was obtained in the case of using methanol as the alcohol at 67.62 °C, in presence of NaOH as the catalyst by 1.1 wt. %, mixing intensity of 709.42 rpm and the alcohol to oil ratio of 6.09. Fuel samples were prepared with Diesel and B5 samples in the presence of pilot to gaseous fuel ratios of 50, 60, 70, and 80 %. The ratio of the pilot to gaseous was prepared by the use of Eq. 1 which prepares samples by the percentage of alternative energy. Experiments were performed using a 0.948 L, naturally aspirated, direct injection, four-stroke, single-cylinder, water-cooled diesel engine manufactured by Kirloskar Oil Engines Ltd., India. The engine benefits a displacement of 948 cc which was loaded by a jb/t-200 electricity generator which was suspended to the test engine using a shaft. The generator was connected to a 200 kN load cell through a 30 cm arm. The engine was loaded by a variable resistance TDGC2-5KVA. The fuel consumption is also measured by calibrated cylinder method. The tests were conducted at a constant speed of 1500 rpm and full load. In the present study, ANFIS was employed as a modeling platform for the estimation of the total vibration value. Additional description about ANFIS is available in our previous study in [35]. As is clear from the architecture of ANFIS in Fig. 2, biodiesel portion, NG ratio, and engine load are three inputs for generating the only output value (total vibration). The modeling phase for ANFIS was started using three MFs of Tri., Trap, Gbell for choosing the best function. These MFs are four types of the most popular membership functions for developing the ANFIS technique in the training phase. The training phase was performed using 70% of the total data. ANFIS was developed using the hybrid optimum method with linear type for the output membership function. Based on the results the following conclusions could be derived:
• Increasing the engine load from 25 to 100 increased the engine vibration, especially in the Diesel cycle. Accordingly, in all the cases, the increase of engine load increased the engine vibration such that the full load condition had a higher vibration compared with the part-load condition. This can be due to the higher CN of NG compared with Diesel fuel.
• In the vertical axis the vibration trend was different. The presence of NG in the combustion chamber increased the vertical vibration. This could be due to the increase of peak pressure in the combustion chamber in the presence of NG which increases the piston force in the vertical direction because of its higher calorific value (kJ/kg) compared with Diesel and B5. This point requires more studies about the relation between vertical vibration and piston peak pressure that can be a considerable future perspective for further studies.
• B5 provided lower vibration compared with that diesel fuel. Also, in the case of using B5, increasing the NG ratio could effectively reduce the engine vibration compared with Diesel fuel.
• ANFIS could successfully predict the total engine vibration with high accuracy. This makes ANFIS a robust tool for future studies. ANFIS also has the capability of staying on as a controlling unit for control purposes. Results of the present study can successfully cover the operations of intelligence systems for the reduction of engine vibrations.