Effects of Castor and Corn Biodiesel on Engine Performance and Emissions under Low-Load Conditions

Abstract

Growing concerns over resource depletion and air pollution driven by the rising dependence on fossil fuels necessitate the exploration of alternative energy sources. This study investigates the performance and emission characteristics of a diesel engine fueled by biodiesel blends (B10 and B20) derived from castor and corn feedstocks under low-load conditions (idle and minimal accessory loads). We compare the impact of these biofuels on engine power, fuel consumption, and exhaust emissions relative to conventional diesel, particularly in scenarios mimicking real-world traffic congestion and vehicle stops. The findings suggest that biodiesel offers environmental benefits by reducing harmful pollutants like carbon monoxide (CO) and particulate matter (PM) during engine idling and low-load operation. However, replacing diesel with biodiesel requires further research to address potential drawbacks like increased NO_x emissions and lower thermal efficiency. While a higher fuel consumption with biodiesel may occur due to its lower calorific value, the overall benefit of reduced contaminant emissions makes it a promising alternative fuel.

1. Introduction

The consumption of petroleum-based fuels on Earth is increasing very rapidly in the transportation, power generation, and agriculture sectors along with the growth in industry. Limited energy resources are causing the depletion of fossil fuels, continuing the era of high oil prices, and rapidly increasing the problem of air pollution [1,2]. In particular, the fossil fuels used in transportation are a major source of pollution and contribute to environmental destruction. In large cities where vehicles are more concentrated, air pollution is progressing faster [3]. Although the government is enforcing strong emissions regulations, the overall environmental pollution problem in cities shows no signs of improvement as vehicle use increases rapidly [4]. Exhaust gasses from a vehicle’s engine emit toxic gasses due to incomplete combustion. This causes a lot of damage to people, animals, and plants. In general, the source of exhaust gas emissions from vehicles is generated while driving on the road, but many pollutants are emitted when the engine is idling even when the vehicle is parked or stopped. When a vehicle’s engine is idling, a lot of fine dust and nitrogen dioxide are emitted into the air due to unnecessary fuel consumption. This idling operation can also expose the engine to the risk of overheating. According to reports from relevant regulatory agencies, if a vehicle with a fuel efficiency of 12 km per liter is idling for 10 min while stationary, it consumes approximately 138 cc of fuel, which is equivalent to driving 1.6 km on the road [5]. Compared to when the vehicle is running, the exhaust gasses include 6.5 times more carbon monoxide and 2.5 times more hydrocarbons when the vehicle is in stationary mode. As stated above, the pollutants in vehicle exhaust gasses can be emitted more when the engine is running while idling or when accessories such as air conditioners or various electrical devices are used while idling [6,7].

In order to solve these problems, a lot of attention has been focused on biodiesel as an alternative energy source worldwide to meet energy demand and protect the environment from air pollution. In recent years, the consumption of diesel fuel for logistics transportation has been increasing, and biodiesel is an appropriate energy source to replace it. Compared to fossil fuels, biodiesel has the advantage of being able to utilize abundant resources and relatively low resource depletion problems [8]. Biodiesel is a fuel in the renewable energy sector, which is environmentally friendly when burned compared to pure diesel and has great future growth potential in terms of economy and energy efficiency [9].

This study investigates the performance and emission characteristics of a diesel engine operating under low-load conditions (idle and minimal accessory loads) fueled by pure diesel and biodiesel blends (B10 and B20) derived from castor and corn feedstocks. The aim is to compare and analyze how these biofuels impact engine power output, fuel consumption, and exhaust emission components compared to conventional diesel, particularly under low-load (0%, 5%, 10% load) scenarios prevalent in real-world driving situations like traffic congestion and stationary vehicles.

2. Methodology

2.1. Material and Biodiesel Fuel Production

Biodiesel is produced through the glycerin separation process by reacting alcohol and triglycerides in rapeseed oil. Although it has the disadvantage of high viscosity and low volatility compared to pure diesel, it has excellent combustion performance and emits less exhaust contaminants because it is an oxygen-containing fuel [10,11]. Raw materials for biodiesel rapeseed oil are divided into edible crops and non-edible crops. First, corn is a biodiesel food crop that uses food-based raw materials and has the advantage of a stable supply of raw materials through mass production [12]. However, there may be limits to sustainability in terms of price competitiveness. Corn has the advantage of low free fatty acid content and a low concentration of process contaminants, including moisture. However, corn oil is mostly waste cooking oil that is discarded after being used for cooking, and there is no recycling method, so it is recognized as a substance that pollutes soil and water [13]. Therefore, it is necessary to use corn as an eco-friendly fuel through various studies and experiments, and it is useful to produce it as biodiesel and use it as an alternative energy fuel. Secondly, there is castor, which is a non-food crop. Oil extracted from castor seeds can be produced as biodiesel through transesterification reaction. Although castor is a non-edible crop, it is widely used as a raw material for cosmetics or to manufacture various bio-based products. It can also be used as a renewable alternative energy source, and its distribution and demand are increasing [14,15]. Castor is very environmentally friendly, and the biodiesel produced from it can play a significant role in protecting the atmospheric environment as an eco-friendly alternative energy source. Figure 1 shows castor and corn plants.

Biodiesel is produced through a transesterification process. This is an organic chemistry reaction that is formed by adding methanol and potassium hydroxide (KOH) as a catalyst to seed oil and mixing them in a stirred reactor [16]. This process allows the reaction to proceed more quickly at higher temperatures, but in most cases, the temperature is maintained below the boiling point of methanol. There are two types of biodiesels used in the experiment, and the production process is shown in Figure 2. First, 2.5 g of potassium hydroxide is diluted in 135 mL of methanol and then mixed with 500 mL of corn oil. Then, it is diluted in a magnetic stirrer at a temperature of 55 degrees Celsius while rotating at 700 rpm for about 2 h. After storing it at room temperature for about a day, glycerin is separated from the biodiesel. The separated glycerin contains soap components formed during the reaction between methanol and the catalyst and many contaminants originally present in the seed oil. Glycerin is a pure compound and originally has a clear and bright color, but due to these contaminants, it changes to a dark brown or black color. Even when glycerin is separated from biodiesel, it still contains 3% to 6% methanol and generally some soap. If the soap content is low enough, it can be removed by the evaporation of methanol, but washing with water is necessary to remove any residual glycerin, methanol, soap, and catalyst in the biodiesel. Washing is performed by mixing biodiesel with water at a temperature of 70 degrees Celsius. This process is repeated approximately 5 to 6 times until no more contaminants are found [17]. Castor biodiesel was also manufactured using the same method.

2.2. Experimental Setup

Table 1. Experimental engine specifications.

Parameter	Specification
Using fuel	Diesel
No. of cylinders	4 (inline)
Bore × Stroke	84 × 90 mm
Displacement	1995 cc
Fuel injection	Common rail direct injection
Valve type	DOHC
Injector type	Magnetic solenoid
Compression ratio	16.0:1
Max. fuel pressure	1800 bar
Max. Power	186 PS/4000 rpm
Max. Torque	41 kgf-m/1750–2750 rpm
Emission Level	EURO5

shows the specifications of the engine used in the experiment. The engine used in the biodiesel combustion experiment is an electronic diesel engine of the common rail direct injection (CRDI) type. A normal engine mounted on an actual sports utility vehicle that had driven about 1000 km was removed from the vehicle and installed on an engine dynamometer for testing. To accurately measure combustion gas emission properties, the diesel particulate filter (DPF) bricks in the exhaust manifold assembly were removed. And the experimental engine was installed in the dynamometer. Testing biodiesel in a controlled environment with a test electronic diesel engine allows valuable data to be gathered on emissions, performance, compatibility, and cost-effectiveness.

Figure 3 shows a photo of the actual experimental engine and dynamometer. The dynamometer used in the experiment is an eddy-current electronic type, has a maximum capacity of 37.3 kw, and can rotate at a maximum speed of 7000 rpm. The engine dynamometer is equipped with SB-200L (manufactured by CAS, Yangju city in Republic of Korea) as a torque load cell sensor and is installed on the side of the dynamometer’s rotation direction to measure the load on the engine issued by the dynamometer.

Table 2. Smoke meter and emission analyzer tester specifications.

	Emission Analyzer	Smoke Meter
Measuring	HC, CO, CO2—NDIR	Light transmission
Principle	O2, NOx—Electrochemistry	smoke meter
Measurement	HC: 1~15,000 ppm,	0.0~100.0%
Range	CO: 0.000~9.999%
	NOx: 0~5000 ppm,
	O2: 0.00~25.00%
Accuracy	FS ±2%	±1% (0.00~21.42 m−1)

shows two specifications of the exhaust gas data acquisition device used in the experiment. It shows the specifications of the equipment of HG-550RT (manufactured by Hephzibah, Incheon city in Republic of Korea) for the exhaust gas analyzer and CMS-2300 (manufactured by Jastec, Seongnam city in Republic of Korea) for the diesel smoke tester. These measuring devices detect the properties of the exhaust gasses when the engine is running.

Figure 4 shows the installation locations of various measuring devices required for the experiment. The measuring tubes of the exhaust gas analyzer and smoke meter were inserted about 30 cm into the exhaust gas line, and to measure fuel consumption, a fuel weight meter using a load cell (CAS, BCA-15L) was installed at the bottom of the fuel tank to measure the weight of fuel consumed. In addition, to monitor the temperature and pressure of each part in the engine during the experiment, the engine data acquisition device, the INSITE engine diagnostics provided by Cummins, was connected to the OBD terminal of the engine wiring harness and monitored using a computer.

2.3. Methodology

The five fuels used in the experiment were pure diesel D100, castor B10, castor B20, corn B10, and corn B20. Biodiesel B10 fuel is a blended fuel with 10% biodiesel added to pure diesel, and B20 is a fuel with 20% biodiesel added. Due to the characteristics of the electronically controlled CRDI diesel engine, when pure biodiesel of B100 is used, the viscosity and density of the fuel are higher than that of pure diesel, which can cause changes in the injection conditions in the combustion chamber and differences in the lubrication function of injector parts during the experiment. Therefore, in order to maintain constant operating conditions of the experimental engine, B10 and B20 fuels were selected, and the experiment was conducted.

The exhaust gas measurement experiment was conducted under engine warm-up conditions where the engine coolant temperature reached 85 to 90 degrees. Three load conditions for the engine were selected: 0% load, 5% load, and 10% load. In each load condition, hydrocarbon (HC), carbon monoxide (CO), nitrogen oxide (NO_x), and particle mass (PM) were measured at 4 different engine speeds: 850 rpm, 1000 rpm, 1150 rpm, and 1300 rpm. To obtain a stable value during measurement, exhaust gas was measured while the engine was sufficiently maintained for about 5 min after reaching the target engine speed. To ensure accuracy, 4 speeds were measured as a cycle, and the average value was calculated by repeating the measurement three times. Finally, the final data were obtained by adding up all the emission values measured in each engine speed range and displayed as a bar graph for comparison with other fuels.

Brake Thermal Efficiency (BTE) and Brake-Specific Fuel Consumption (BFSC) were measured at an engine load of 10%. The engine’s torque was measured for each engine speed and the brake power value was calculated. Then, the calorific value of fuel and mass of the fuel-supplied values were additionally input to calculate BTE and BFSC and display them in a linear graph.

2.4. Properties of Biodiesel

Table 3. Fuel properties and ASTM standard.

Property	Standard (ASTM)	Diesel (D100)	Castor (B100)	Castor (B20)	Castor (B10)	Corn (B100)	Corn (B20)	Corn (B10)
Density (kg/m3)	800–880	830	885	861	852	879	858	849
Kinematic viscosity (mm2/s)	1.9–6	2.43	8.46	5.92	4.08	7.26	4.68	3.78
Cetane num.	48–65	49.3	61.2	58.4	56.3	63.2	56.4	53.9
Flash point (°C)	>130.0	54.0	109.0	90.2	78.2	79.1	66.7	61.5
Calorific value (MJ/kg)	>35.0	45.1	35.2	39.8	41.9	38.4	40.4	42.1

shows the physicochemical properties of biodiesel manufactured from castor oil and corn oil for comparison with pure diesel. The manufactured 100% biodiesel was confirmed to have a relatively high density and kinematic viscosity compared to pure diesel. The cetane number was higher than that of pure diesel, but the calorific value was relatively low [18]. The physicochemical properties of the blended fuel of castor and corn B10 and B20 used in the experiment are also shown.

3. Results

3.1. Emission Characteristics

3.1.1. HC Emissions Characteristics

Figure 5 shows the HC values measured by five fuels, pure diesel (D100), castor biodiesel (B10, B20), and corn biodiesel (B10, B20) under three load conditions (0%, 5%, and 10% load). As the engine load increased from 0% to 5% and 10%, the pure diesel was measured as 102 ppm, 104 ppm, and 114 ppm, respectively. It was confirmed that HC emissions increase as the engine load increases. This is because the fuel injected into the combustion chamber is richly controlled and burned when the engine load increases [19]. When castor B10 fuel was used under the same load conditions, HC values were confirmed to be 84 ppm, 93 ppm, and 105 ppm. These were reduced emissions compared to using D100 fuel, and the reduction rates were confirmed to be 17.6%, 10.6%, and 7.9%, respectively. In addition, when measuring using castor B20, it was confirmed that it was reduced by 33.3%, 11.8%, and 24.6% to 68 ppm, 78 ppm, and 86 ppm. Compared to D100, HC emissions decreased in castor biodiesel. Among castor biodiesels, HC emissions were lower in castor B20 than in castor B10. The reason why HC is reduced is because the 10% oxygen component contained in castor biodiesel promotes active combustion when the fuel burns in the combustion chamber, so the HC emissions are reduced [19,20].

When corn biodiesel fuel was used, corn B10 was measured at 76 ppm, 84 ppm, and 86 ppm, and corn B20 was measured at 64 ppm, 74 ppm, and 79 ppm under each load condition. This confirmed that compared to D100, corn B10 was overall reduced by 25.5%, 14.1%, and 24.6%, and corn B20 was reduced by 37.3%, 13.1%, and 30.7%. When comparing castor biodiesel and corn biodiesel, corn biodiesel was found to be more effective in reducing HC than castor biodiesel. This is because the density and viscosity of the biodiesel fuel properties are higher in castor biodiesel, so when fuel is injected into the combustion chamber, it has a negative effect on the injection state, spray state, and distribution, thereby reducing the acceleration of combustion [21].

3.1.2. CO Emissions Characteristics

Figure 6 shows the results of CO emissions from pure diesel and castor and corn biodiesel. When the engine load is changed from 0% to 5% and 10%, both pure diesel and castor and corn biodiesel tend to increase overall. This is because more fuel is supplied for active combustion when the load increases. This locally richer mixing ratio causes a lack of oxygen in the combustion chamber, which increases the CO emission of the exhaust gas during combustion.

When classified by load condition, CO values of 0.132%, 0.145%, and 0.155% were measured in the engine when using castor B10 fuel, and 0.097%, 0.174%, and 0.134% in castor B20. Comparing this with D100, castor B10’s CO emissions during engine combustion were reduced by 4.3%, 7.6%, and 3.7%, and castor B20’s CO emissions were further decreased to 29.7%, 25.5%, and 16.8%. Corn B10 and corn B20 fuels were also used under the same conditions and measurements were made under three conditions: 0%, 5%, and 10% loads. The result values were measured as 0.106%, 0.134%, and 0.141%, and corn B20 was measured as 0.076%, 0.060%, and 0.073%. When these values are compared to D100, CO was reduced by 23.2%, 14.6%, and 12.4% for corn B10, and CO reduction was further increased by 44.9%, 61.8%, and 54.7% for corn B20. When comparing the two biodiesel fuels used in the experiment, it was confirmed that corn biodiesel was more effective than castor biodiesel in terms of CO emissions, like the HC results. This is influenced by the density and viscosity of the biodiesel properties, and the lower the value, the more positively it responds to the effect of combustion [22].

3.1.3. NO_x Emissions Characteristics

Figure 7 shows the NO_x emissions of the exhaust gas emitted from the engine, comparing pure diesel, castor, and corn biodiesel, respectively. It was confirmed that biodiesel had higher NO_x emissions than pure diesel under three different load conditions. Comparing the NO_x emissions of castor B10, castor B20, corn B10, and corn B20, respectively, it was measured as 399 ppm, 433 ppm, 430 ppm, and 480 ppm at 0% load. These results were 4.7%, 13.6%, 12.9%, and 26.0% more than those of D100. As a result of applying 5% load, the results were 546 ppm, 580 ppm, 583 ppm, and 645 ppm, which were increases of 31.9%, 40.1%, 40.8%, and 55.8% compared to D100. When the engine load was applied at 10% load, more NO_x emissions were measured at 583 ppm, 660 ppm, 665 ppm, and 715 ppm, which was 23.3%, %39.5%, 40.6%, and 51.2% compared to D100. Overall, D100 was proven to be more effective than biodiesel in terms of NO_x emissions. Among biodiesels, the NO_x values increased in the following order: castor B10, castor B20, corn B10, and corn B20. The reason for this increase in NO_x emissions from biodiesel is that the oxygen contained in the fuel acts as a combustion accelerator in the combustion chamber, and active combustion leads to an increase in exhaust gas temperature, resulting in an increase in NO_x [23]. Biodiesel generally has the effect of reducing HC and CO during engine combustion, but it has the problem of increasing NO_x. There is a need for improvement to demonstrate that biodiesel is an environmentally friendly fuel.

3.1.4. Particle Mass (PM) Characteristics

Figure 8 compares PM emissions from castor and corn biodiesel compared to D100. Overall, it was confirmed that biodiesel PM emissions decreased when engine load conditions increased. Under 0% load conditions, it was measured at 0.3% at D100, and the measurement results were 0.2%, 0.1%, 0.2%, and 0.1% in the order of castor B10, castor B20, corn B10, and corn B20, respectively. Castor biodiesel and corn biodiesel showed the same reduction rate, and compared to D100, emissions were lower at 33.3%, 66.7%, 33.3%, and 66.7%, respectively. And under 5% load conditions, PM was measured at 0.3%, 0.4%, 0.2%, and 0.0%. It was confirmed that corn biodiesel is more effective in reducing PM than castor biodiesel, with reduction rates of 50.0%, 33.3%, 66.7%, and 100.0% compared to D100, respectively. In addition, even under the 10% load condition, reductions of 42.9%, 42.9%, 57.1% and 100.0% were confirmed. Both corn B10 and B20 were more effective in reducing PM emissions than castor biodiesel. This change in PM reduction proves that biodiesel is an eco-friendly fuel because its combustion effect is better than that of pure diesel, and it can be an alternative energy source in the future. Since biodiesel has the potential to lower PM emissions, research should focus on demonstrating its effectiveness using a diversity of feedstocks [24,25].

3.2. Performance Characteristics

3.2.1. Variation in Brake Thermal Efficiency

Figure 9 shows BTE calculated under 10% load conditions. It was calculated from the brake power values measured at four locations starting from 850 pm up to 1300 pm. Overall, it was confirmed that BTE increased as engine speed increased. This is because as the engine speed increases, the vortex phenomenon of the air flowing into the combustion chamber becomes active, allowing fuel and air to mix well, thereby increasing combustion performance. When analyzed by fuel, D100 showed the best efficiency, followed by corn B10, corn B20, castor B10, and castor B20. Through experiments, it was confirmed that biodiesel fuel had a lower BTE than pure diesel. The reason is that biodiesel has a relatively high fuel consumption per unit horsepower and a low calorific value of the fuel. However, technology to capture the pollutants generated by combustion using biomass, which is the raw material for biodiesel, is being studied to overcome the disadvantages associated with low calorific value [26].

3.2.2. Brake-Specific Fuel Consumption

Figure 10 shows BSFC, measured at four engine speeds under 10% load conditions. As engine speed increased, the BSFC of all fuels tended to decrease. D100 indicates the lowest value in the entire engine speed range, followed by corn B10, castor B10, corn B20, and castor B20. In terms of braking fuel consumption per kw-h, D100 is the most efficient. The reason is that compared to pure diesel, biodiesel has a low fuel calorific value, and biodiesel’s relatively high density and viscosity increase braking fuel consumption due to inefficient fuel quantity control when the engine load increases.

4. Conclusions

As a result of testing while idle and in low load mode using pure diesel and blended biodiesel in a CRDI diesel engine, the following conclusions were drawn regarding the performance of the engine and the properties of the exhaust gas. From the five fuels (D100, castor B10, castor B20, corn B10, and corn B20) used in the experiment, it was confirmed that HC and CO emissions overall tended to increase as the engine load increased to 0%, 5%, and 10%. However, when comparing the exhaust gas properties emitted from each fuel at the same load, biodiesel showed a greater improvement in HC and CO reduction than pure diesel. When comparing four types of biodiesel fuel, the fuel that was more effective in reducing CO and HC emissions was corn B10 compared to castor B10, and corn B20 rather than castor B20. Regarding the blended rate of biodiesel, B20 tends to outperform B10 in reducing these pollutants. This is because biodiesel burns cleaner than pure diesel. With a higher percentage of biodiesel in the blend (B20 vs. B10), there is more clean-burning fuel, and less pure diesel contributing to these emissions. This shows that when the vehicle is stopped and the engine is operated in idle or low load mode, biodiesel fuel has a more positive effect on protecting the atmospheric environment than pure diesel fuel. Additionally, this experiment confirmed that biodiesel fuel is effective even when measuring PM. Castor biodiesel was more effective in reducing PM than pure diesel, and corn biodiesel was more effective than castor biodiesel.

However, it was confirmed that NO_x emissions among exhaust gas properties increased in biodiesel fuel compared to pure diesel fuel. In particular, corn biodiesel emitted the largest amount of NO_x. Biodiesel combustion leads to higher NO_x emissions compared to pure diesel. This is due to the higher in-cylinder temperatures during combustion caused by the oxygen content in biodiesel. However, the oxygen content of these biodiesels promotes complete combustion, resulting in reduced HC, CO, and PM emissions. Therefore, it is important to consider the balance of these effects. When comparing engine performance, BTE showed the best performance in D100 under 10% load conditions, followed by corn B10, corn B20, castor B10, and castor B20. BSFC also had the best fuel reduction effect in D100, followed by corn B10, castor B10, corn B20, and castor B20. Biodiesel is an environmentally friendly fuel in terms of emissions, but various approaches are needed, such as optimized engine research for biodiesel and biodiesel fuel improvement that can improve engine performance with a low BTE and BSFC.

This study supports the fact that biodiesel is a more environmentally friendly fuel than pure diesel when the engine is operated in idle mode or low load conditions while the vehicle is stopped. However, to replace pure diesels with sustainable fuels, a comprehensive and multifaceted research approach is needed on the problem of increasing NO_x emissions and increasing fuel consumption due to low thermal efficiency from biodiesel. Engine modifications can be used to optimize combustion and minimize the increase in NO_x with biodiesel. While increased fuel consumption is a consequence of biodiesel’s lower calorific value, the overall impact on contaminant emissions can be positive due to reductions in harmful pollutants like CO and PM. However, potential NO_x increases require consideration and potential mitigation strategies.