Experimental investigation & thermodynamic modeling of a diesel engine to analyze performance, energy, emission and exergy using edible and inedible biodiesel blends

Abstract

Abstract The demand for energy alternatives other than conventional fossil fuel is growing in the modern era as the rise in depleting fossil fuel prices and thriving interest in the environment. Most developing countries are primarily dependent on the supply from the volatile international market that affects their socio-economic growth. Non-renewable resources, such as fossil fuels, can be substituted by renewable resources such as biofuels obtained in liquid (biodiesel) and gaseous form (hydrogen, biogas, producer gas). By adopting new policies, generations of biodiesel have expanded in the modern era in numerous countries. Biodiesel is acknowledged as a 'green fuel' with diverse superiority compared to petroleum diesel. It is non-toxic, renewable, and safe to handle. Also, biodiesel is biodegradable. The low sulfur content with an increased flashpoint compared to petroleum diesel makes the biodiesel a promising suitable automotive fuel in the near future. According to FAO (Food and Agricultural Organization) Italy, the rapid escalation in biodiesel generation is alarming as biodiesel's extensive use would develop greater constrain on food supply, and adverse social and environmental consequences could arise. Though no possible unanimity can be validated, the high food price does not correlate with edible seed oil production. However, more significant investments in the agricultural sector offer probable everlasting convenience for agriculture and rural development. In Malaysia, the palm tree was popularized since 1870 as an exquisite plant. In 2014 the universal production of oil had expanded about 155.8 million tons. Only in Malaysia, there was 60% growth of palm agricultural land by 2005. The fruit of the palm tree is produced two or three years after being planted. Palm trees produce fruit for twenty-five years. The amount of oil produced per hectare is more as compared to other oilseed crops. In 2014, Malaysia's government had mandated the adoption of 5% palm oil methyl ester biodiesel (B5) with petroleum diesel in the transport sector entire nationwide. In 2018 researchers have claimed that industrial palm oil can yield sufficient biodiesel (POME) to balance Malaysia's total diesel consumption effectively. Diesel engine manufacturers provide engine warranties on biodiesel's consumption up to B7 in Malaysia, and the fact that without any significant modification, the diesel engine can handle biodiesel-diesel blends up to B100 (100% biodiesel) can promise a better future environment. Global biodiesel generation is based on edible oil such as Palm, Sunflower, etc. However, in India, Bangladesh, and Pakistan, where scarcity of food is a prime concern, biodiesel production from edible oil is not very welcome. Some inedible oils are accessible in these countries, which are prescribed for biodiesel generation. Azadirachta Indica (neem) thrives in different regions of Asia (India, Bangladesh, etc.) in the genre 'maliaceae'. This herbal and holy tree can grow up to 18 meters with 40% oil content seed. Triglycerides and other triterpenoid composites are found in neem oil with mainly palmitic acid and stearic acid. Waste vegetable oil (WVO) indicates the oil after cooking, which is a waste product and is produced by food industries at the time of food formation. A noticeable hefty amount of WVO is spawned by the hotel, restaurant, and food chain industries and ditched into illicit dumping ground and river. The use of WVO in biodiesel production can cut down the production cost and hazardous waste dump. In the long run, pure biodiesel directly in the engine can cause complications of injector & delivery valve clogging, severe engine deposits, and a sticky piston ring. Inedible vegetable oil biodiesel blend can be applied to compensate for the total consumption of petroleum diesel. Due to high viscosity, flash point, density, and low heating value, raw vegetable oil cannot be straightly used in an unmodified diesel engine. Vegetable oil is required to be transformed into biodiesel to achieve the required properties as engine fuel. The neem oil and waste cooking oil biodiesel from inedible sources can be utilized commercially as a counterfeit for petroleum diesel. Also, the esterifies product maintain tolerable fuel properties according to the American Society for Testing and Materials (ASTM), European Committee for standardization (EN) & Bureau of Indian Standards (BIS). There are a thriving amount of works dedicated to the generation and application of various biofuels. In the modern era, the utmost prevailing substitute to Petroleumbased diesel is biodiesel; chemically, it was known as an alkyl ester of fatty acids from various plant and animal sources. Biodiesel has more oxygen in its structure cause of its organic nature, which allows widespread oxidation of fuel, resulting in complete combustion. Due to biodiesel's more significant cetane number, it has good self-ignition characteristics, which benefits in its combustion and permits achieving comparable thermal efficiency values regarding engine powered by diesel fuel. Biodiesel also reduces the formation of CO, HC, and soot particles in the engine. However, the NOx emission from the engine with biodiesel is found to be higher. IC engines' exergy and energy analysis has been considered for almost decades to estimate the various losses developing during the CI engine operation. The value of useful work is represented by exergy, which a system can provide when moving toward the reference environment by a reversible process. Analysis of exergy can assess the location, type, and magnitude of energy losses in various engine areas. Hence, analysis of exergy provides a context to take necessary action for reducing the losses in different parts of the engine. Numerous research works have been done on CI Engines in various capacities. Most of the works are cited based on the experimental investigation to find out the engine performance. Researchers are recently showing more interest in simulating the engine performance to get optimum engine operating parameters instead of build and test method that requires more time and expense. Commonly simulation of the engine can be done considering the engine cylinder volume as 'single zone,'' multi-zone,' and 'multidimensional'. Generally, single-zone thermodynamic models are used to have a fast and primary analysis of engine combustion and performance. In the single-zone model, it is assumed that the cylinder charge is a uniform or homogeneous mixture with the same temperature and composition for all the time during the engine cycle. The model must be based on empirical heat-release laws to use a single-zone model in diesel engines. A multidimensional model sets the cylinder's space on a fine grid, but it requires detailed information of many phenomena inside the combustion chamber. This kind of approach has its disadvantage in computational time and the need for massive storage space. The multizone model is an intermediate step between single-zone and multidimensional models. Multizone models can be effectively used to model diesel engine combustion systems. However, Multizone models are generally not any good than single-zone models since the phenomena of zone characteristics and interactions inside the combustion chamber are unknown. Single-zone models are one of the simplest and fastest methods to model engine combustion processes. Based on the above discussions, the present work deals with biodiesel production from three different vegetable oil. Biodiesel production from edible palm oil, inedible neem oil, and waste vegetable oil was executed, and biodiesel's characteristics were studied. Palm oil has been established as a suitable biodiesel resource in various countries. Neem oil (considered inedible but herbal tree) is available in India and tropical regions. Waste vegetable oil is a waste product produced by food industries and available in plenty throughout the world. The optimal parameters as catalyst concentration, the molar ratio of methanol and oil, reaction time, and temperature for high biodiesel yield of palm oil biodiesel were determined by the Taguchi method. An experimental investigation to study the combustion, performance, emission characteristics of biodiesel fired C. I. engine were carried out with different biodiesel blends (B5, B10, B15, B20) under various engine load conditions at three different compression ratios. The energy in terms of shaft energy and associated energy loss and exergy as exergetic efficiency were analyzed based on experimental data. Also, the CI engine model was developed in an in-house code using a single zone approach fueled with biodiesel blends. The combustion product model was incorporated in the model. Finally, the CI engine simulation model was validated with the experimental results fueled with biodiesel blends.