Introduction

Presently, the major source of air pollution is due to the exhaust emission from the diesel engines. Automobiles generally use gasoline as fuel in the internal engine, but technological advances have led to the design of cars that run on electricity and even water.

Kathirvelu et al. (2017) investigated the performance of an engine with the biodiesel obtained from jatropha seeds and fish waste. The results showed that the brake thermal efficiency (BTE) was slightly lower than the diesel whereas the efficiency of the engine was found to be higher for jatropha oil methyl ester than fish oil methyl ester. HC (hydrocarbon), CO (carbon monoxide), and soot emissions were found to be lower than the diesel whereas NOx (oxides of nitrogen) and exhaust gas temperature were found to be higher than the diesel. Also, jatropha oil methyl esters seem better than fish oil methyl esters. Comparative studies were carried out for oxidation and storage stability of mahua biodiesel with that of jatropha biodiesel and mineral diesel by Acharya et al. (2017). The biodiesel blended with various blending ratios from 10 to 90% (B10 to B90) were prepared for the experimental purpose. The experimental results showed that the oxidation stability seemed to be satisfied with 20% of jatropha biodiesel and 30% blending of mahua biodiesel but showed steady increase with equal percentage blending of the biodiesels. An experimental investigation by Madiwale et al. (2018) with jatropha, soyabean, palm, and cottonseed biodiesel of the different blending ratios are performed to enhance the performance of the engine and to reduce harmful exhaust emissions. They have used ethanol as an additive in the blends at a constant ratio of 5%, and the experiment was carried out on the single-cylinder four-stroke VCR electric start diesel engine. The investigation results showed a significant improvement in brake power and brake-specific fuel consumption with the addition of ethanol as an additive for jatropha, soyabean, palm, and cottonseed biodiesel. Among all fossil fuels, diesel in particular has played a critical role in all major sectors such as transportation, power, industry, marine, and agriculture owing to fuel economy, reliability, and rigidity. But they emit hazardous emissions like NOx, HC, PM, and smoke which causes several global hazards. Jatropha curcas is a plant that belongs to the Euphorbiaceae family (Sadhik Basha and Anand 2014). Within this genus, there are more than 170 species distributed around the world, especially in tropical regions. This plant comes from Central America (Mexico), and it is possible to obtain an oil yield higher than 1500 kg per hectare. This oil is adequate to be used as a raw material in the biodiesel production. Jatropha curcas is gaining more attention as a feedstock for biodiesel production due to its incompetence with food crops (Silitonga et al. 2017). Furthermore, adverse climatic conditions such as high temperature, low moisture content, and soil fertility do not affect its productivity (Balat 2010; Ong et al. 2013; Yusuf et al. 2011). Alternative fuels should be eco-friendly, be easily available at a low cost, and fulfill the basic requirements without sacrificing engine operational performance (Deepak and Avinash 2007).

An experimental investigation by Forson et al. (2004) on the performance and emission with preheated jatropha biodiesel, untreated jatropha biodisel and its blends at different load conditions in a constant speed of 1500 rpm engine was performed, and the results prove jatropha biodiesel as a promising alternative fuel for compression ignition engines. Thermal efficiency was lower for unheated jatropha biodiesel compared to heated jatropha biodiesel and base diesel. The blend of 97.4% of pure diesel and 2.6% of jatropha biodiesel yielded a better engine performance. Also, Bhupendra Singh Chauhan et al. (2010, 2012) investigated that the engine performance with unheated jatropha biodiesel is slightly inferior to the performance with diesel fuel and concluded that the biodiesel derived from jatropha biodiesel will be the best substitute for diesel fuel in CI engine without any modifications. A study on the effects of engine design parameter followed by performance and emission characteristics of a diesel engine fuelled with jatropha methyl ester was conducted by Jindal et al. (2010). The experiment was conducted with various compression ratios along with injecting pressure. The results showed an increase in compression ratio and injection pressure that increases the brake thermal efficiency with a reduction in brake-specific fuel consumption with lower emissions. The use of biodiesel blends is limited due to its poor oxidative stability (Dinkov et al. 2009; Karthikeyan et al. 2018; Yuvarajan et al. 2017; Thangaraja et al. 2012). Tan et al. (2012) investigated exhaust emission at various blending of jatropha methyl ester with diesel from 5 to 100 volume percentages. They observed that with less effect on NOx emission, CO emission is found to be increased with biodiesel at low engine loads and HC emission was reduced with increasing biodiesel fuels. Torres-Jimenez et al. (2011) made a study on the physical and chemical properties of ethanol–diesel fuel blends. The study reported that using additives to avoid phase separation and to raise the flash point, blends of diesel fuel with ethanol up to 15% can be used to fuel diesel engines.

In previous research (Dhandapani et al. 2012), both jatropha and ethanol have injected through intake port at constant rate for the evaluation of effect of fuel viscosity and combustion duration, and also blended with diesel with constant proportion for performance and emission characteristics. The present work aimed to investigates the effect of the engine performance and emission characteristics for different blending ratios of the Jatropha biodiesel, ethanol and diesel.

Materials and methods

Preparation of biodiesel

Jatropha biodiesel was prepared using commercial jatropha oil by transesterification process. In this process, potassium hydroxide is used as a catalyst and methanol as alcohol (Kishore Pandian et al. 2017; Radhakrishnan et al. 2018). Preheating of raw oil was performed to 70 °C followed by mixing to a solution containing catalyst and alcohol. The obtained mixture is heated again for 5 °C till the complete vaporization of methanol so that glycerol and ester were separated.

To perform the engine test, the prepared biodiesel was mixed with diesel and ethanol at different blending ratios namely, the first blend comprises of 90% diesel, 7.5% jatropha biodiesel, and 2.5% ethanol (D 90J7.5E1.25), where ethanol acts as a catalyst. The second blend comprises of 95% diesel with 3.75% jatropha biodisel and 1.25% (D95J3.75E1.25), and the third blend comprises of 98% diesel with 1.5% jatropha biodisel and 0.5% ethanol (D98J1.5E0.5). The physical and chemical properties of the prepared biodiesel blends are tested as per the ASTM standards and listed in Table 1.

Table 1 Properties of fuel
Full size table

Experimental setup

The experiments were performed on a water-cooled, single-cylinder, four-stroke, variable compression ratio (VCR) and electric start direct-injection diesel engine. The schematic layout and the photographic view of experimental setup are shown in Figs. 1 and 2, respectively. Table 2 shows the test engine specifications. The test engine is coupled to an eddy current type dynamometer for load variations. The AVL Digas 444 five-gas analyzer was employed for the measurement of CO, CO2, NOx, and HC emissions at different load conditions. Diesel engine output shaft is connected with the eddy current dynamometer, which is used to measure the power and torque. The load cell is connected to the dynamometer for varying the load on the engine (0–100%).

Fig. 1
figure 1

Schematic layout of test engine

Full size image
Fig. 2
figure 2

Photographic view of test engine

Full size image
Table 2 Specifications of engine setup
Full size table

Uncertainty analysis

Every work includes some amount of uncertainty. These uncertainties mainly result of calibration, sensors, observations, test procedure, and environmental condition. In view of uncertainties, the preferred test results can be examined of any work. If a quantity to be measured “R” has a function of many self-regulating variables like x1, x2, x3, ...xn, then R = R (x1, x2, x3, ...xn).

Let the measured quantity uncertainty be expressed as WRand the independent variables uncertainties are expressed as W1, W2, W3, ...Wn.

Subsequently, the uncertainty in the measured quantity is given by Eq. (1):

$$ {W}_R=\sqrt{\;\left[{\left(\frac{\partial R}{\partial {x}_1}{W}_1\right)}^2+{\left(\frac{\partial R}{\partial {x}_2}{W}_2\right)}^2+{\left(\frac{\partial R}{\partial {x}_3}{W}_3\right)}^2+...........{\left(\frac{\partial R}{\partial {x}_n}{W}_n\right)}^2\right]} $$
(1)

where \( {W}_R=\frac{\delta\;R}{R};\pm \delta\;R \)is the error in R. The root-mean-square method is employed to examine the percentage of the uncertainty of different parameters such as smoke, BTE, HC, brake-specific fuel consumption (BSFC), CO, and NOx emissions. The accuracy and uncertainty levels for the measured quantity are presented in Table 3.

Table 3 Accuracy and uncertainties
Full size table

Results and discussion

The performance and emission characteristics of an engine fuelled with jatropha biodiesel–ethanol–diesel were evaluated by finding the BTE, BSFC, NOx emission, CO2 emission, CO emission, and HC emission.

BTE

The ratio of brake power (BP) to the energy in the fuel burned to produce this power is called brake thermal efficiency. It is used to evaluate how far an engine utilizes the heat from fuel to convert into energy. The variation of BTE with brake power for different blends is shown in Fig. 3. At 0.937 kW, compared with diesel, the brake thermal efficiency of the blends D90J7.5E2.5 and D95J3.75E1.25 was increased by 2.13% and 3.24%, respectively. Similar trend has been observed for the brake power output 3.467 kW. It was noticed that the BTE of biodiesel blends is higher than base diesel. This is due to better atomization, better combustion, and shorter ignition delay characteristics of biodiesel and ethanol blends. In addition, the atomization and mixing of biodiesel and ethanol blends with air is in uniform rate causing shorter breakup length, higher dispersion rate, and increased efficiency. These results are matched with the experimental results of Appavu et al. (2018), Devarajan (2018), and Mahalingam et al. (2018).

Fig. 3
figure 3

Brake thermal efficiency

Full size image

BSFC

BSFC is used to measure the fuel consumption rate for unit power output. The variations in the BSFC for the different blends are shown in Fig. 4. It can be seen that the BSFC of the blend D90J7.5E2.5 was decreased by 2.68% compared with diesel at 0.937 kW. Similar trends have been observed for all rated power outputs. It is also observed that the BSFC of the D95J3.75E1.25 blend was increased by 3.69% at 0.937 kW. In general, BSFC decreases with an increase in loads. Due to the presence of ethanol in the biodiesel blends, the BSFC of the high concentrated biodiesel blend was decreased with respect to lower density and viscosity. The combined effects of relative fuel density, viscosity, and blending proportions lead to these fluctuations (Yuvarajan and Venkata Ramanan 2016).

Fig. 4
figure 4

Brake-specific fuel consumption

Full size image

NOx emission

Nitrogen oxide is a generalized term for NO and NO2 represented as NOx. The high temperature in the combustion chamber and the surplus availability of oxygen are the causes of formation for NOx emission (Sudalaimuthu et al. 2018; Balan et al. 2018). Engine test was conducted for emissions using various blending properties of jatropha oil and ethanol under various load conditions. Figure 5 shows the NOx emission levels for the various loads. The baseline data were generated using pure diesel. D90J7.5E2.5 shows moderate decrease in NOx emission by 1.96%, 21.88%, 14.68%, and 15.56% for the power output 0.937, 1.874, 2.811, and 3.467 kW compared to base diesel, whereas D95J3.75E1.25 shows a marginal increase of NOx emission by 0.39%, 0.29%, and 0.556% at 0.937, 2.811, and 3.467 kW, respectively, compared with base diesel. Generally, NOx emissions from biofuels are higher than that of diesel. The possible reason is due to higher availability of oxygen in methyl esters when compared to diesel. The other possible reason is due to higher peak cylinder pressure of methyl esters over diesel originating high NOx emissions (Devarajan et al. 2018; Siva et al. 2018; Ganesan et al. 2018).

Fig. 5
figure 5

NOx emission

Full size image

CO2 emission

Engine test was conducted for emissions using various blending properties of jatropha oil and ethanol under various load conditions. Figure 6 shows the CO2 emission levels for various loads. The baseline data were generated using pure diesel. The CO2 emission of D90J7.5E2.5 blend shows a marginal decrease by 0.02%, 0.03%, and 0.07% at 0, 0.937, and 3.467 kW power output, respectively, compared to diesel. It was observed that CO2 emissions were marginally decreased with increasing of biodiesel blending. It is because of higher oxygen content in biodiesel when compared with base diesel which helps for complete combustion (Radhakrishnan et al. 2017; Rathinam et al. 2018; Yuvarajan et al. 2018; Senthilkumar et al. 2018).

Fig. 6
figure 6

CO2 emission

Full size image

CO emission

Carbon monoxide is formed because of the incomplete conversion of carbon atoms present in the fuel, and its main cause is due to an inadequate supply of oxygen during combustion (Arul Gnana Dhas et al. 2018; Balan et al. 2018). Figure 7 shows the CO emission levels for various loads. Engine test was conducted for emissions using various blending properties of jatropha oil and ethanol under various load conditions. The baseline data were generated using pure diesel. For the blend D98J1.5E0.5, a significant decrease of 0.01% and 0.02% at 0, 2.811, 3.467, and 0.937, 1.874 kW power output was observed. For the blend, D95J3.75E1.25 shows a marginal increase of 0.01% at 0, 1.874 kW, a marginal decrease of 0.01% at 2.811 kW, an increase of 0.04% at 0.937 kW, and a decrease of 0.04% at 3.467 kW than the base diesel. It was observed that CO emissions were decreased with the decrease of biodiesel blending. This effect is due to oxygen supply variation during engine operation (Joy et al. 2017; Yuvarajan and Venkata Ramanan 2016).

Fig. 7
figure 7

CO emission

Full size image

HC emission

Figure 8 shows the HC emission levels for various loads. The baseline data were generated using pure diesel. The blend D95J3.75E1.25 shows a marginal decrease of HC emission by 1.32% at initial power output and a drastic decrease of 15.21% at 1.874 kW and 10.6% at 3.467 kW power output. It was observed that HC emissions were decreased with increasing of biodiesel blending at all power outputs. It is because of higher oxygen content in biodiesel when compared with base diesel which helps for complete combustion.

Fig. 8
figure 8

HC emission

Full size image

Conclusions

The present experimental investigation was carried out on a single-cylinder four-stroke diesel engine. After the transesterification process, it was observed that the kinematic viscosity of Jatropha curcas oil gets reduced significantly than the diesel. The density of Jatropha curcas oil was higher, but calorific value seems to be lower than the diesel. The experimental output showed a significant improvement in performance with three blends and when the percentage of blend increases, performance also slightly increases. On the other hand, when the engine is running with biodiesel and its blend, emission such as HC, CO2, and NOx emissions were reduced with increasing of biodiesel blend whereas the CO emission was reduced with decreasing of the biodiesel blend. This was due to complete combustion of fuel and variation in the supply of oxygen to the engine. This result proves that jatropha with ethanol blend will act as a good substitute biofuel for a diesel engine in near future. However, there are variable parameters which can be evaluated in future such as by varying compression ratio, injection timing, and injection pressure.