Introduction

Diesel engines played dominant role in energy and power sectors of everyday human life. They are producing power in efficient way at reliable cost with minimum requirement. The diesel engines are used in many fields like, pumping work, construction, transportation, locomotive, diesel generators, marine and defense sectors. In India, most of the agricultural equipment relies on diesel fuel for its onsite and stationary applications. Diesel engines are mostly preferred to run with minimum or without any modification required for its multi-fuel application like biodiesel and biogas, while operating diesel engines, emission coming out from the diesel engine is to be properly controlled to meet standards of emission norms. Biodiesels are one of the promising renewable sources from various edible and non-edible oil reduces emissions drastically under controlled operating conditions [1,2,3,4,5,6]. Biodiesel produced from alkaline-based commercial unrefined oils has high acid value. Two-step transesterification processes are used to remove acid from rubber seed oil in the presence of sulfuric acid. Then, the alkaline-catalyst transesterification is developed to get biodiesel from unrefined oil. The performance and emission of biodiesel from rubber seed oil reduce the emissions at increase in biodiesel blends, and on the other hand lower blends of biodiesel increases the thermal efficiency and reduces the fuel consumption in diesel engine [7]. The thermodynamic model is established to analyze the performance and combustion characteristics of diesel engine. The established model increases combustion pressure, peak temperature and brake thermal efficiency of biodiesel from rubber seed oil and diesel with increase in compression ratio. At the same time, increases in relative air–fuel ratio decrease the above parameters for all fuels. The mathematical model can be used of any kind of hydrocarbon fuel in diesel engines [8]. Cement clinker-based limestone is used as catalyst to obtain biodiesel made from high FFA rubber seed oil in one step. The catalyst used in this process is not affected by moisture and the free fatty acid produced in this process can be reused without loss in activity and also it meets the ASTM D7651 standard of biodiesel [9].

Addition of cerium oxide nanoparticle additives with diesel and castor oil biodiesel in VCR engine improves the combustion and reduces the emission significantly compared to diesel. Use of cerium oxide catalyst provides oxygen for CO and absorbs oxygen from exhaust to reduce NOx formation [10, 11]. Biodiesel is produced from waste cooking oil by varying load and blend at fixed CR 21 in VCR engine. The results reveal that the reduction in CO, HC and CO2 was obtained with increase in NOx emission of lower blends of biodiesel compared to diesel [12, 13].

The energy and exergy analysis of VCR engine is conducted on variable CR and IT at fixed load with dual fuel mode. The engine is operated with biogas with emulsified rice bran biodiesel as pilot fuel. The combination of CR 18° and IT 29° BTDC gives a better thermodynamic analysis for dual fuel VCR engine [14]. The energy availability, conversion and destroyed energy in different methods in diesel engine are evaluated to find the utility of fuel in diesel engine. The unavailability of energy in diesel engine due to heat lost in friction, heat transfer to walls, insufficient air and combustion is discussed. Several studies reported the exergy and energy analysis in different parts of diesel engine [15,16,17,18,19,20]. Exergy analysis on alternate fuel by three injection strategies in diesel engine decreases the NOx emission, and there is no change in thermal and second law efficiency. There was a control in pre-injection strategy that increases the CO and HC emission in diesel engines [21, 22].

The biogas-run dual fuel mode diesel is tested with biodiesel and diesel as pilot fuel at different combinations to utilize the exergy from various forms.  Exergy loss due to exhaust and cooling water in dual fuel mode is 28–30% more than that in diesel mode. When the biodiesel is replaced as pilot fuel in same settings, the exergy efficiency reduces by 2% [23]. The use of alternative fuels in diesel with addition of ethanol/butanol results in high combustion rate with delayed ignition of the air–fuel mixture. At this juncture, there was delayed combustion kinetic phase, lead to reduction in in-cylinder temperature, resulted in reduction in soot particles compared to conventional fuel [24,25,26]. Diesel-like fuel is used to analyze the heat of combustion of diesel, diesel-like produced from pyrolysis of soybean oil and diesel/biofuel blends using a bomb calorimetry. The results revealed that the calorific value of diesel-like fuel is better than that of biodiesel blends during combustion reaction. It is observed that the addition of biodiesel blends to diesel decreases the calorific value of fuel blends [27].

Thermodynamic analysis of an irreversible air standard dual cycle-based numerical study is established which is more close to experimental results. In this study, the effect of increasing the stroke length rises the power output and then further increase in compression ratio decreasing the power output. The maximum power output at this compression ratio maximizes the thermal efficiency by increasing the volumetric efficiency [28]. This study estimates the chemical exergy of coal, heavy fuel and natural gas for conventional thermal power plants. It is observed that the chemical composition of fuel greatly influences the chemical exergy. In heavy oil, hydrogen-carbon ratio is longer than other fuels, which is the most influencing parameter of exergy [29,30,31,32].

Research objective

To the best of authors’ knowledge, the effect of biodiesel fueled engine with variable compression ratio on energy and exergy analysis is limited [29, 30] under thermodynamic point of second law efficiency. Moreover, most of the experiments were conducted by varying CR from 16:1 to 18.5:1 by varying load, IT and IP [4, 5]. But in this experiment, the VCR engine is provided with varying CR from 18:1 to 22:1 at higher CR; as well as exergy and energy analysis of biodiesel fuel blends is limited in VCR engine study.

The aim of this present work is to analyze the effect on variation in CR and biodiesel blends of diesel with different proportions on energy and exergy distributions of a VCR engine fueled with methyl esters of rubber seed oil as fuel. This test is conducted in a 3.5 kW, single cylinder, water-cooled, naturally aspirated, direct injection, multi-fuel, VCR engine. The experiment is conducted at different loadings for a combination of five CR from 18:1 to 22:1 and with five biodiesel blends like B20, B40, B60 and B80 at 80% load.

Materials and methods

Test setup

Test setup is a four stroke single cylinder, direct injection, water-cooled variable compression ratio multi-fuel engine as shown in Fig. 1. The detailed specifications of VCR engine are given in Table 1. The engine consists of air plenum, fuel flow sensor(solenoid type), speed sensor, crank angle encoder and combustion pressure (Kistler make) sensor provided in the various places of engine to acquire data for data acquisition system, using “engine test express 8.5” version, connected to personal computer. Thermocouples (J, K type thermocouples) are connected at various points of engine, at inlet and exhaust manifold to measure the temperature at different locations.

Fig. 1
figure 1

Schematic diagram of the experimental set up

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Table 1 Specification of the variable compression ratio engine
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The engine exhaust manifold is connected with exhaust gas calorimeter provided with inlet and outlet water connections to measure energy carried by exhaust gases. The exhaust gas calorimeter is a shell-and-tube-type exchanger to conduct heat balance test. The outlet of the manifold is connected to exhaust pipe with a provision to insert exhaust gas analyzer nozzle with hose. The engine and various sensors are calibrated before taking readings. The engine output shaft is connected to strain gauge-based load cell and eddy current dynamometer. The engine exhaust emissions are measured using Mars Tech. five gas analyzer, and accuracy in measurements is tabulated in Table 2.

Table 2 Accuracies of the measurements of the gas analyzer
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Test fuel

Rubber seed oil is a by-product of rubber and is acquired in Madurai city, Tamilnadu, India. India is the one of the rubber-producing country among nine countries, rubber seed from rubber tree is unutilized much. The kernel contains 40–45% of oil, extracted and processed for biodiesel production. Two-step transesterification process is used to remove high fatty acid content of rubber seed oil, the FFA is above 2%. The fatty acid composition of rubber seed oil is given in Table 3. In acid esterification process, 6 mL of sulfuric acid is added to 200 mL of methanol to reduce FFA content below 2% in the heated oil about 60 °C, and then, 4 g of KOH is dissolved in 300 mL of methanol; mixture is heated and stirred. The methyl esters that remain in the upper layer is removed and heated about to 80 °C to remove moisture in the biofuel. The biodiesel properties is tested in the laboratory and compared with ASTM/IS 1448 standard of diesel and biodiesel as tabulated in Table 4.

Table 3 Free fatty acid composition of rubber seed oil
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Table 4 Properties and Indian standards of biodiesel and diesel
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Test procedure

The engine is run with diesel to achieve steady-state condition, at standard CR18, at a standard injection pressure of 150 bar. Then the engine is fueled with biodiesel (methyl esters of rubber seed oil) blended with diesel via 20, 40, 60 and 80% on volume basis at different combinations of CR from 18:1 to 22:1 at 80% load. During the test period, volume flow of fuel consumption and exhaust gas emissions of CO, HC, NOx and CO2 are recorded. In every test, brake thermal efficiency, fuel flow rate, brake power, brake-specific energy consumption and exhaust gas temperature for five compression ratios from 18:1 to 22:1 for different biodiesel blends are calculated and recorded. The combustion characteristics such as combustion pressure, heat release rate and various emission levels are recorded for each operating levels and are stored in personal computer. The same procedure is repeated for different biodiesel blends of methyl esters of rubber seed oil.

Calculations

The energy and exergy analysis of VCR engine is given below.

Energy analysis

The energy analysis was used to find the energy conversion of chemical energy of fuel into heat energy (Qin). The heat energy after combustion was converted into brake power (shaft power), the energy carried away by cooling water (Qw), energy carried away by exhaust gases (Qe) and unaccounted losses (Qu) due to friction, radiation, heat lost to surrounding, etc.

Energy supplied by the fuel in unit time can be expressed as,

$$Q_{\text{in}} = \left[{\dot{m}_{\text{f}} \times {\text{LHV}}} \right],\,{\text{kW}}$$
(1)

Useful power available at output shaft is given by

$$Q_{\text{s}} = {\text{BP}} = \left[{\frac{2 \times \pi \times N \times W \times r}{60 \times 1000}} \right],\,{\text{kW}}$$
(2)

Thermal efficiency available at shaft is calculated by

$${\text{BTE}}\,{ = }\,\left[ {\frac{{{\text{BP}} \times 3600 \times 100}}{{Q_{\text{in }} }}} \right]\,\%$$
(3)

The brake-specific energy consumption can be calculated from

$${\text{BSEC}} = \frac{{\left[{ \dot{m}_{\text{f}} \times {\text{LHV}}} \right]}}{\text{BP}},\,{\text{kJ}}\,{\text{s}}^{- 1} \, {\text{kW}}^{- 1}$$
(4)

The maximum pressure developed in the cylinder per CA rotation is given by,

$$\frac{{{\text{d}}p}}{{{\text{d}}\theta}} = k - \frac{1}{V}\left({\frac{{{\text{d}}Q_{\text{in}}}}{{{\text{d}}\theta}} - \frac{{{\text{d}}Q_{\text{loss}}}}{{{\text{d}}\theta}}} \right) - k\frac{{P{\text{d}}V}}{{{\text{d}}\theta}} + \frac{P}{{\left({k - 1} \right)}}\frac{{{\text{d}}k}}{{{\text{d}}\theta}}$$
(5)

Energy in engine cooling water per unit time is given as

$$Q_{\text{w}} = \left[{\dot{m}_{\text{w}} \times C_{\text{pw}} \times \left({T_{\text{ewo}} - T_{\text{ewi}}} \right)} \right],\,{\text{kW}}$$
(6)

Energy in exhaust gas in unit time is found from

$$Q_{\text{e}} = \left[{\left({\dot{m}_{\text{a}} + \dot{m}_{\text{f}}} \right) \times C_{\text{pe}} \times \left({T_{\text{eci}} - T_{\text{amb}}} \right)} \right],\,{\text{kW}}$$
(7)

Heat lost by exhaust gases equals to heat carried by calorimeter, using this energy balance specific heat of exhaust is evaluated as

$$C_{\text{pe}} = \frac{{\left[{ \dot{m}_{\text{cw}} \times C_{\text{pw}} \times \left({T_{\text{cwo}} - T_{\text{cwi}}} \right)} \right]}}{{\left[{\left({\dot{m}_{\text{a}} + \dot{m}_{\text{f}}} \right) \times \left({T_{\text{eci}} - T_{\text{eco}}} \right)} \right]}},\,{\text{kJ}}\, {\text{kg}}^{- 1} \,{\text{K}}^{- 1}$$
(8)

The unaccounted loss in unit time is calculated from

$$Q_{\text{u}} = \left[{Q_{\text{in}} - \left({Q_{\text{s}} + Q_{\text{w}} + Q_{\text{e}}} \right)} \right],\,{\text{kW}} .$$
(9)

Exergy analysis

Availability in thermodynamics is the part of energy that can be converted into useful energy. The chemical energy of fuel is appeared as shaft availability (As), cooling water availability (Aw), availability in exhaust gases (Ae), and unaccounted availability (Ad) due to friction, radiation and heat lost to surroundings, etc. The availability terms were calculated using second law of thermodynamics as explained by [33,34,35,36].

Fuel input availability is found from

$$A_{\text{in}} = \left[{\frac{{1.0338 \times \dot{m}_{\text{f}} \times {\text{LHV}}}}{3600}} \right],\,{\text{kW}}$$
(10)

Shaft availability is evaluated as

$$A_{\text{s}} - {\text{Shaft}}\,{\text{power}}\,{\text{or}}\, {\text{brake}}\,{\text{power,}}\,{\text{kW}}$$
(11)

Availability in cooling water is calculated by

$$A_{\text{w}} = \left[{Q_{\text{w}} - \left\{{\dot{m}_{\text{w}} \times C_{\text{pw}} \times T_{\text{amb}} \times \ln \left({\frac{{T_{\text{ewo}}}}{{T_{\text{ewi}}}}} \right)} \right\}} \right], {\text{kW}}$$
(12)

Exhaust gas availability is evaluated from

$$A_{\text{e}} = Q_{\text{e}} + \left[{\left({\dot{m}_{\text{a}} + \dot{m}_{\text{f}}} \right) \times T_{\text{amb}} \times \left\{{C_{\text{pe}} \times \ln \left({\frac{{T_{\text{amb}}}}{{T_{\text{eci}}}}} \right) - R_{\text{e}} \times \ln \left({\frac{{P_{\text{amb}}}}{{P_{\text{e}}}}} \right)} \right\}} \right], {\text{k}}$$
(13)

Re is exhaust gas constant in kJ kg−1 K−1, by assuming complete combustion calculated by, \(\text{Re} \, = \,{\text{Universal}}\,{\text{gas}}\, {\text{constant}}\left({ R_{{{\text{u}} }} \,{\text{in}}\, {\text{kJ}}\,{\text{k}}\,{\text{mol}}^{- 1} \,{\text{K}}^{- 1}} \right)/{\text{molecular}}\,{\text{weight}}\left({M\, {\text{in}}\, {\text{kg}}\,{\text{k}}\,{\text{mol}}^{- 1}} \right) ,\) Destructed availability is found from

$$A_{\text{d }} = \left[{A_{\text{in}} - \left({A_{\text{s}} + A_{\text{w}} + A_{\text{e}}} \right)} \right], {\text{kW}}$$
(14)

Second law efficiency or exergy efficiency is calculated by

$$\eta_{\text{II}} = \left[ {1 - \left( {\frac{{A_{\text{d }} }}{{A_{\text{in}} }}} \right)} \right] \times 100\%$$
(15)

Entropy generated is given by

$$S = (A_{\text{d }}/T_{\text{amb}}),\, {\text{kW}}\,{\text{K}}^{- 1}.$$
(16)

Error analysis

The error analysis for engine performance parameters such as pressure, temperature, IMEP and BSFC are measured and calculated based on root mean square value [21, 37]. The errors are calculated based on the minimum value of output measured from instrument and its accuracy. The uncertainty [38] was calculated using formula (17).

$$U_{\text{R}} = \left[ {\left( {\frac{\partial R}{{\partial x_{1} }} U_{{{\text{x}}_{1} }} } \right)^{2} + \left( {\frac{\partial R}{{\partial x_{2} }} U_{{{\text{x}}_{2} }} } \right)^{2} + \cdots + \left( {\frac{\partial R}{{\partial x_{\text{n}} }} U_{{{\text{x}}_{\text{n}} }} } \right)^{2} } \right] ^{1/2}$$
(17)

The uncertainty of the measured quantity R is \(U_{\text{R}},\)\(x_{\text{n}}\) be the measured uncertainties with independent variables and \(U_{{{\text{x}}_{1}}},U_{{{\text{x}}_{2}}}, U_{{{\text{x}}_{\text{n}}}}\) error values of measured parameters. The measured and calculated uncertainties are given in Table 5.

Table 5 Uncertainties of measured and calculated values
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Results and discussions

Energy analysis

The conversion of fuel energy into heat energy is distributed in unit time at various processes at different CR, and blend at 80% load is given in Table 6. The VCR engine is considered for this study; the effect of CR on various energy distributions under different biodiesel blends is averaged and included in Fig. 2a. The shaft energy and cooling water energy distributions on an average, decrease by 7.86% and 15.32%, respectively, for change in CR from 18:1 to 22:1. For the same settings, energy carried away by exhaust gases and the unaccounted losses increases by 23.59% and 6.8%, respectively. At an averaged CR 20, shaft energy distributions and cooling water energy of B20 and B40 are found to be 19.5, 19.34, 3.91 and 6.49% higher than diesel, respectively, depicted in Fig. 2b. For the same settings, the energy lost in exhaust gases and uncounted losses decreases by 19.25, 17.24, 10.2 and 13.4% compared to diesel. This is due to fast distribution of temperature at micro flare-up of fuel at rise in CR. The energy conversion of fuel for higher blends (B60 & B80) decreases due to its lower volatility nature and ignition delay [25]. Increasing CR from 18:1 to 21:1, power output increases, afterward shaft energy decreases due to its increase in stroke volume [28].

Table 6 Energy analysis of biodiesel and diesel for different CRs at 80% load
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Fig. 2
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a–f Energy analysis of biodiesel at different CR

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On an average, there was an increase in BSEC and mass of fuel consumed by 8.84% and 7.62% on increasing CR from 18:1 to 22:1 as shown in Fig. 2c, d. Upon increasing CR from 18:1 to 22:1, the mass of fuel consumption of B20 is found to be 0.71, 0.71, 0.72, 0.70 and 0.72 kg h−1, respectively, lower than diesel due to its homogeneous mixture of fuel with air. On increasing CR from 18:1 to 22:1, the BTE of B20 are found to be 37.49, 37.43, 36.66, 37.95 and 37.56%, respectively, higher than diesel and other blends as shown in Fig. 2e. This is due to better cone spray formation of fuel blend and oxygen content present in the fuel; further increase in biodiesel content at all CR decreases efficiency due to its lower calorific value of fuel and poor volatility of biodiesel [8]. On an average, the maximum pressure and heat release rate increase by 16.51% and 14.92% upon increasing the CR from 18:1 to 22:1 as presented in Fig. 2f. On increasing the CR from 18:1 to 22:1, the exhaust gas temperature rises by 1.64%, on an average as depicted in Fig. 2g. This is due to better combustion and shorter ignition delay of biodiesel [1].

On the other hand, the increase in CR from 18:1 to 20:1 on an average increases the uncounted loss by 32.29% and decreases shaft energy, cooling water energy and exhaust gas energy by 1.85, 18.93 and 17.29%, respectively [23]. The BTE of B40 for CR of 18:1 to 22:1 are found to be 36.64, 33.37, 33.04, 28.33 and 29.98%, respectively, and that of diesel are 33.81, 32.54, 31.51, 33.21 and 30.30%, respectively. It is quite apparent that there is an improvement in BTE with the change in CR of biodiesel with that of diesel due to its burning velocity and shorter ignition delay of biodiesel to burn the fuel completely. With the advancement of B20 for CR from 18:1 to 22:1, the mass of fuel consumed, maximum pressure and exhaust temperature of B20 increase by 1.81, 16.5 and 33.93%, respectively. For the same settings, maximum pressure and HRR of B20 increase by 19.57% and 1.37%, respectively. From the results, it is observed that increase in CR increases BTE, maximum pressure and HRR and lowers BSEC of B20 with that of diesel and other blends [11].

Exergy analysis

The exergy analysis of various processes per unit time of biodiesel blends at different combinations of CR’s at 80% load was given in Table 7. The outcome of this work is to examine the CR on VCR engine; various exergy distributions under biodiesel blends of diesel, B20, B40, B60 and B80 are averaged and included in Fig. 3a. On an average, due to increase in CR from 18:1 to 20:1, destructed availability increases by 11.57% and decreases for further advancement of CR. Upon increasing the CR from 18:1 to 22:1, cooling water availability decreases by 26.95%. On the other hand, shaft energy availability and exhaust gas availability are found to be 7.89% and 19.12%, respectively. The impact of biodiesel blends on VCR engine under averaged CR is included in Fig. 3b. The shaft availability of averaged CR of B20 and B40 increases by 19.54% and 19.35%, respectively. However, for same settings, the destroyed availability decreases by 3.65% and 4.55%, respectively. The averaged exhaust gas availability and cooling water availability for the same settings are found to be 23.79, 20.69, 19.01 and 14.08%, respectively [33].

Table 7 Exergy analysis of biodiesel and diesel for different CRs at 80% load
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Fig. 3
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a–d Exergy analysis of biodiesel at different CR

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The exergy efficiency and entropy generation of fuel blends at various CR’s are as depicted in Fig. 3c, d. Upon increasing CR from 18:1 to 22:1, the exergy efficiency of B20 increases by 4.19% and for B40 decreases by 7.41%, respectively. On the other hand, for the same settings, the entropy generation is the reverse trend of exergy efficiency. On CR increases from 18:1 to 22:1, B20 decreases by 18.27% and for B40 increases by 28.94%. On an average fuel blend, by increasing CR from 18:1 to 22:1, the exergy efficiency and entropy generation increase by 1.75% and 4.19%, respectively. This due to increase in stroke length from certain value, exergy efficiency increases first, and then it starts to decrease. The exergy efficiency of biodiesel blends and diesel increases with rise in CR except B80 owing to its lower volatility in nature. But at the same time, the entropy generation starts to decrease from CR 18: to 21:1; afterward it increases due to its increase in stroke length [28].

Emission analysis

The emission analysis for different combinations of CR at various biodiesel blends at 80% load is presented in Fig. 4a–d. On increasing CR from 18:1 to 22:1, the CO and HC emission of B20 and B40 are near to diesel when compared to other blends. By increasing CR, the CO emission of B60 and B80 increases due to its higher viscosity of blends, rise in in-cylinder temperature, improper mixing of fuel–air mixture, deficiency in oxygen at full load and shorter ignition delay of higher blends of biodiesel [5]. For same settings, CO2 and NOx emission are found be higher than diesel. On an average fuel blend, by increasing CR 18:1 to 22:1, CO and HC emission decreases by 3.63% and 33.08%, respectively. For the same settings, CO2 and NOx emission increases by 3.6% and 10.81%, respectively. With the improvement in CR, the charge pressure and temperature enhance the complete combustion upon decrease in clearance volume [28]. But at the same time, addition of biodiesel blends in fuel at combination of CR’s improves the combustion and cylinder temperature due to its short ignition delay of biodiesel, increases NOx and CO2 emissions further. The CO and HC emission of B20, by increasing CR from 18:1 to 22:1, decreases by 7.34% and 53.33%, respectively. For same settings, NOx increases by 6.73% and CO2 emission is found to be 2.43%. For the same settings, the CO and HC emission of B40 increases by 20.48% and 41.17%, respectively. On the other hand, CO2 emission decreases by 2.09% but NOx emission is found to be high of 1.17%, respectively. The results revealed that on an average, the stationary VCR diesel engine emissions of various blends were found to be less than prescribed level for all biodiesel blends at all CR at 80% load.

Fig. 4
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a–d Emission analysis of biodiesel at different CR

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Conclusions

In this study, thermodynamic analysis of methyl esters of rubber seed oil blended with diesel for four various combinations by varying CR from 18:1 to 22:1 in VCR engine at 80% load was performed. Thermodynamic analysis of biodiesel in VCR engine revealed that the energy analysis at CR 20, the shaft energy, fuel input and cooling water energy distributions of lower blends decrease with increase in CR. However, at higher CR and blends, energy distributions of exhaust gases and cooling water increase.

The exergy analysis revealed that, on an average, the destructed availability decreases for lower blends of biodiesel at 4.55% by increasing CR. On the other hand, for same settings, shaft availability of lower blend increases by 14.95% at CR 20. However, cooling water availability in fuel input and biodiesel blends observed are very low. Further, the energy content in biodiesel of higher blends increases the peak pressure at higher CR, but at the same settings, energy released by B20 is higher than other blends and diesel due to micro-explosion of fuel.

In emission analysis, CO and HC emission of B20 and B40 behaves near to diesel at CR 20 and at CR 22. On the other hand, CO2 emission is slightly higher at higher CR of lower blends. The NOx emission of biodiesel blends found to be slightly higher than diesel at higher CR. The experimental results revealed that available energy can be effectively recovered from B20 and B40 at CR 20 compared to diesel. The diesel can be effectively replaced by lower blends of biodiesel at optimum CR 20 without any modification in VCR engine. This research engine used in this study is focused on stationary VCR diesel engine with improved efficiency and lowered emission in agricultural sectors in India. In existing design, adopting the change in CR with biodiesel blends improves the performance at reduced cost with slight modifications.