Evaluation of Performance and Emission

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JSAE 20119060 SAE 2011-01-1936

Evaluation of Performance and Emission Characteristic of Karanja Biodiesel and Diesel Blend in a Medium Capacity C.I. Engine Employing EGR N Ramaswamy Alstom Projects India Ltd

Mohammad Aqil, Naveen Kumar Delhi Technological University, Delhi, India

Copyright © 2011 Society of Automotive Engineers of Japan, Inc. and Copyright © 2011 SAE International

compression ignition (CI) engines as shown by various researchers [3-5]. Other emissions such as carbon monoxide (CO), particulate matter (PM), hydrocarbon (HC) and smoke reduce with biodiesel as compared to fossil diesel without any penalty on engine performance [5-7]. Among the various NOx reduction strategies available viz. fuel additives, retarded injection, selective catalytic reduction (SCR) and exhaust gas recirculation (EGR) [8], EGR was chosen for this experimental study as it replaces both fresh oxygen and nitrogen in the cylinder with exhaust gas, thereby limiting the peak combustion temperature and oxygen concentration inside the cylinder, which results in reduced NOX emissions. Considering the wide application in agriculture sector, a medium capacity, single cylinder, direct injection diesel engine was selected for the present study and fitted with EGR system to measure and allow EGR rates till 20%. The combined effect of using Karanja biodiesel blend (KB20) and EGR on the performance and emissions of the CI engine was recorded and compared with that of diesel fuel.

ABSTRACT Depleting fossil energy reserves and large scale debasement of the environment has been grabbing headlines for some time now. Biodiesel has been proven by researchers to produce less CO, HC and PM, albeit higher NOx as compared to diesel. The present study was carried out with blends of Karanja –a type of Leguminosae plant abundant in India- that produces non-edible seed oil analogous to Jatropha. An exhaust gas recirculation (EGR) system was employed to encumber the higher NOx emissions produced with biodiesel. Performance and emission characteristics of Karanja biodiesel blend (KB20) with EGR rates of 0, 5, 10, 15 & 20% were compared with baseline data of diesel. The results show that adaptation of EGR with KB20 reduces NOx emissions without any penalty on smoke opacity or BSEC.

INTRODUCTION Energy is the building block for socio-economic development of any country. Fossil fuels are projected to remain the dominant sources of primary energy globally and their demand is predicted to reach 16,800 Mtoe by the year 2030 as compared to 12,000 Mtoe in 2007 [1]. Middle distillates - the group of petroleum cracking products containing diesel and kerosene constitute 49.2% of this world fossil fuel demand [2]. The diesel engines are typically more efficient than the gasoline engines due to higher compression ratio. Diesel engines also do not suffer from size and power limitations, which the SI engine is prone to. Thus, keeping these factors into account, the diesel engine emerges as the obvious choice for heavy-duty applications in agricultural, industrial and transport sector. But on the flip side, combustion in diesel engines produces large amounts of nitrogen oxides (NOx) due to availability of excess oxygen and nitrogen in the presence of high flame temperatures inside combustion chamber. This phenomenon is compounded with the use of biodiesel blends in

EXPERIMENTAL SETUP AND METHODOLOGY BIODIESEL Biodiesel is derivative of vegetable oils. It is made from virgin or used vegetable oils (both edible & non-edible) and animal fats through transesterification. In comparison to diesel, the higher cetane number of biodiesel results in shorter ignition delay and longer combustion, which results in low PM emissions and lesser carbon deposits on injector. The use of biodiesel blends also reduces the overall sulfur content of the blend and compensates for the lubricity loss due to removal of sulfur from ULSD and thus, helps in meeting the sulfur oxides emission norms. KB20 (a blend of 20% Karanja biodiesel+ 80% diesel) was taken for the present experimental work mainly due to the worldwide acceptability of B20.The different


EXHAUST GAS RECIRCULATION SETUP

physico-chemical properties of Karanja biodiesel, diesel and KB20 have been represented in Table 1. It is seen that Karanja biodiesel has slightly lower calorific value but higher density, kinematic viscosity and acid number as compared to fossil diesel. Oleic acid constitutes half of the fatty acid content in Karanja seed oil (Table 2). It is also relevant to mention that unsaturated fatty acids are much higher in Karanja oil as compared to saturated fatty acids. Further, studies have revealed that biodiesel blends of Karanja have shown favorable results over exhaustive trials [9-10].

A direct injection diesel engine of Kirloskar make was used for conducting the experiment (Table 3). It is a single cylinder, four stroke, vertical, air-cooled diesel engine with a compression ratio of 17.5 and develops 7.4 kW brake power at rated speed of 1500 rpm with diesel as fuel. The engine was loaded electrically after being coupled with single phase alternator through flexible coupling. EGR flow was measured using a bypass arrangement for the exhaust gas with a manually controlled EGR valve along the recirculation line, which was sized to allow 25% EGR flow. The high pressure exhaust gas coming out of the engine during the exhaust stroke was led into a smaller air box which acted as a surge tank for accurate measurement of EGR flow rate at each operating point. An orifice meter mounted with a U-tube manometer was designed and installed to measure the volumetric flow rate of the EGR (figure 2).

Table 1: Physico-chemical properties of diesel, KB100 & KB20. Property (unit) Method

Diesel

KB100, Karanja Biodiesel

KB20, Karanja Biodiesel Blend

831

884

841.6

42232

39112

41608

3.21

4.45

3.41

0.2

0.12

0.18

-12

3

-3

-17

-4

-12

76

168

103

3

Density (Kg/m ) ASTM D-4052 Calorific Value (KJ/Kg) ASTM D-4809 Kinematic Viscosity @40°C ASTM D-445 Acid No (mg KOH/ g) ASTM D-664 Cloud Point (°C) ASTM D-2500 Pour Point(°C) ASTM D-97 Flash Point(°C) ASTM D-93

Table 3: Engine specifications Model Rated Brake Power (kW) Rated Speed (rpm) Number of Cylinder Bore x Stroke (mm) Displacement volume (cc) Compression Ratio Cooling System Lubrication System Inlet Valve Open (º) Inlet Valve Closed (º) Exhaust Valve Open (º) Exhaust Valve Closed (º) Fuel Injection Timing (º) Injection Pressure Length Width Height Weight

Table 2: Fatty acid composition (%) of Karanja seed oil. 14:0 (Myristic) ---

16:0 (Palmitic) 11.69

18:0 (Stearic) 6.87

18:1 (Oleic) 51.81

18:2 (Linoleic) 24.46

Single Cylinder, DAF10 7.4 kW (10HP) 1500 One 102 x 116 948 17.5:1 Air Cooled Forced Feed 4.5 BTDC 35.5 ABDC 35.5 BBDC 4.5 ATDC 26 BTDC 200-205 bar 531 mm 546 mm 878 mm 194 Kg

Measurement of EGR rate EGR rate is calculated by the formula [5]: % EGR=

100 x (EGR mass flow) (Total air intake mass of cylinder)

The mass flow rates for computing the EGR rate using the above formula are calculated by using the manometric head in both main air intake and EGR inlet. Thus, the simplified formula used for computation is as follows: % EGR =

a x ¥2ȡwgh/ȡa ______ {(a x ¥2ȡwgh/ȡa) + (A x ¥2ȡwgH/ȡa)}

Where, A - Area of Inlet Manifold H - Height difference on Primary Manometer

Figure 1: Karanja seed oil and biodiesel sample.


EGR Orifice meter EGR Flow control valve Measurement Panel

AVL Smoke-meter

Air Box

Thermocouple AVL DIGAS4000L

Test Engine

EGR Surge Tank

A H ȡw ȡa

- Area of orifice-meter orifice - Height on EGR U-tube Manometer. - Density of water - Density of air

Adequate care was taken while taking down readings for EGR rate, the setup (figure 2) was given 2-3 minutes of time to stabilize after each change in load or EGR rate. EXHAUST EMISSION ANALYSIS The exhaust emission e.g. smoke, HC, CO, CO2 and NOx were measured during the present work. For measuring the smoke opacity, AVL 437 smoke meter was utilized. This instrument gave reading in terms of percentage opacity which was derived from the obstruction of a light beam by the exhaust gas stream. For measurement of HC, CO, CO2 and NOx, an AVL 4000 di-gas analyzer was used (figure 2).

RESULTS The performance and emission characteristics of KB20 at EGR rates of 0, 5, 10, 15 and 20% were noted and plotted against different values of BMEP. The results were compared with the baseline data of diesel without EGR. NOx emissions were reduced by significant amount with application of EGR using Karanja biodiesel. The detailed variation in each of the calculated and measured parameter with changing load and EGR rate is discussed below.

PERFORMANCE CHARACTERISTICS Brake thermal efficiency Figure 3 shows the comparison of BTE for KB20 through EGR levels of 0-20% and diesel without EGR. Brake thermal efficiency values were similar for both the fuels. The Karanja biodiesel on application of EGR has shown slightly higher thermal efficiency perhaps due to the increased combustion velocity as a result of higher intake charge temperature. EGR is found to have resulted in improved combustion due to higher inlet temperature. In addition, it may also be possible that EGR being at slightly higher pressure than atmosphere might have reduced pumping losses also. The chemical effect of EGR associated with dissociation of carbon dioxide to form free radicals can also be attributed to this improvement in efficiency. It shall also be worthwhile to notice that the BTE with 20% EGR was less than that with 15% EGR at peak loads; the drop in efficiency at higher levels viz. 20% of EGR is possibly due to predominant dilution effect of EGR leaving more exhaust gases in combustion chamber. Brake specific energy consumption Brake specific energy consumption is more effective than brake specific fuel consumption (BSFC) in


comparing fuels of different calorific values and densities. Figure 4 indicates the variation of BSEC for KB20 for different EGR rates. BSEC of KB20 was slightly higher for all levels of EGR compared to diesel fuel. This is presumably due to lower calorific value, higher boiling point and viscosity. The plot of BSEC is similar to an inverse plot of BTE which is explained by the fact that reduction in thermal efficiency will invariably increase energy consumption to meet the same load requirement. It was observed that BSEC at 15% EGR rate was higher than 20% for lower loads (figure 4). Exhaust gas temperature There is a small variation in the exhaust temperatures of KB20 and diesel over the whole range of EGR. As EGR rate increases, the relative mechanical energy at the flywheel decreases. This decrease is the result of less efficient energy conversion. In KB20, the exhaust temperature was reduced with increase in the EGR rate (with the exception of 15% and 20% EGR rate) at lower engine loads. The maximum peak load exhaust temperature of 348.6°C was observed with diesel and lowest of 300°C was that of KB20 with 20% EGR rate as shown in figure 5. The exhaust energy also decreases with increased EGR, primarily as a result of lower exhaust flow rate, since a fraction of exhaust energy is re-circulated. This is often complemented with a decrease of exhaust temperature [11].

Figure 5: Exhaust Temp. v/s BMEP. EMISSION CHARACTERISTICS NOx emissions The NOx emissions increased with the engine load for both the fuels as shown in figure 6, due to a higher combustion temperature. The variation of NOx emission was found to be 1577 ppm for diesel and 1850 ppm for KB20 at full load (for 0% EGR operation). NOx emissions were also higher at part load for Karanja biodiesel without EGR. This is perhaps due to dynamic injection advance created by biodiesel apart from static injection advance provided for best efficiency as per engine design. Excess oxygen (10%) present in the biodiesel would have also aggravated the situation. At higher loads, NOx levels were higher by 5–8% as compared to diesel. With 5% and 10% EGR, the NOx level came down for Karanja biodiesel at all the load conditions. Dynamic injection advance of biodiesel fuel can also enhance NOx formation. However, at higher loads NOx levels surprisingly reduced, perhaps due to the dilution effect of EGR at higher loads. With 15% EGR and at full load NOx levels were found to be 1148 ppm for KB20 at full load. NOx emission from biodiesel at all loads, for this EGR rate, was lower compared to diesel under no EGR condition also. Though 20% EGR was able to reduce NOx by a large amount, i.e. 77% for full load, however, reduction in BTE and huge increase in other emissions such as smoke, CO and HC was observed, thus 20% EGR rate is an impractical and unfeasible solution for environment friendly means of reduction of NOx. The results obtained for use of Karanja biodiesel blend KB20 with EGR were concurrent to those obtained by earlier research with Jatropha and Rice bran biodiesel [12-14].

Figure 3: BTE v/s BMEP

CO emissions

Figure 7 represents the variation of CO for different load conditions at various EGR levels. CO emissions were found to be lower for KB20 as compared to diesel with and without EGR. For Karanja biodiesel, CO levels increased as EGR rate was increased. However, CO emissions of KB20 were comparatively lower to diesel. Higher values of CO were observed at full load for Karanja biodiesel beyond 15% EGR. For biodiesel, the excess oxygen content might have partially compensated for the oxygen deficient

Figure 4: BSEC v/s BMEP


trade-off between NOx and smoke opacity. On the other hand, if biodiesel is used in diesel engine smoke opacity is decreased but NOx is increased.

operation under EGR. At peak loads, CO2 breaks into CO in operations where high combustion temperatures and comparatively fuel rich ambience is present, which can also contribute to higher CO emissions. CO2 emissions The CO2 emission for various EGR rates and loads is shown in Figure 8. The CO2 emission increases with increase in the engine load, which is opposite to the trend of the brake thermal energy consumption. The CO2 emission with KB20 was greater than the baseline diesel. However, with increase in EGR rates the CO2 emission decreased. Lesser amount of CO2 in exhaust emission is an indication of the incomplete combustion of fuel. This supports the lower value of exhaust gas temperature. The combustion of fossil fuels produces carbon dioxide that gets accumulated in the atmosphere and leads to many environmental problems. The combustion of Karanja biodiesel also produces carbon dioxide but crops are readily absorbing these and hence carbon dioxide levels are kept in balance. Thus considering the closed cycle of biodiesel it can also be pointed out that the effective emission of CO2 is relatively lower [15].

Figure 6: NOx v/s BMEP.

Un-burnt HC emissions Figure 9 shows variation of HC emission with BMEP at different EGR rate. Increase in HC was significant as EGR rate was increased for biodiesel. It was observed that the full load HC emission was 82.2ppm for diesel compared to 51ppm in case of KB20. This was essentially due to excessive exhaust gas being recirculated, thereby reducing oxygen in the combustion chamber. The graph shows that HC increase with EGR and load. It is perhaps due to the lower excess oxygen availability for combustion as a result of which rich air fuel mixtures are formed at many locations inside the combustion cylinder. The uneven mixture of air and fuel thus formed does not combust properly and evenly, resulting in higher HC emissions. Presence of molecular oxygen in KB20 biodiesel decreases the oxygen required for combustion. This results in lower HC emission. It can be observed from Figure 9 that HC emissions are lower for biodiesel blends than with diesel. HC emissions for KB20 at EGR rate of 20% is the closest as compared to baseline data of diesel.

Figure 7: CO v/s BMEP.

Figure 8: CO2 v/s BMEP.

Smoke opacity Figure 10 shows the smoke opacity v/s BMEP at different EGR rates. Higher smoke opacity of the exhaust is observed when the engine is operated with EGR compared to without EGR, this result is similar to that observed by Hountalas et al [16]. Smoke opacity increases with increasing EGR rates and increasing engine load for KB20. Recirculation of exhaust gas reduces availability of oxygen for combustion of fuel which results in partial combustion and growth in the formation of Particulate Matter. More change in smoke opacity levels was reported at high load as compared to lower load. Therefore, it can be observed that when EGR is applied to diesel engine NOx is reduced but smoke opacity is increased. This is a well-known

Figure 9: HC v/s BMEP


9.

10.

11. Figure 10: Smoke Opacity v/s BMEP

CONCLUSION 12.

As compared with diesel fuel, the biodiesel produced from Karanja oil used in this investigation leads to reduction in CO, HC and smoke opacity. However, there is an increase in NOx concentration, which again is brought down by application of EGR. KB20 has shown small improvement in thermal efficiency with EGR; however, at peak loads there is a decline in BTE with 20% EGR rate. Thus EGR rate of 15 % was found to be optimum in a KB20 biodiesel fueled engine keeping both performance and emission parameters optimal. Adaptation of EGR provided a reduction of up to 45% in NOx concentrations when tested on Karanja B20 fuel with 15% EGR without parallel increase in smoke levels. Thus Karanja, with its large availability and easy convertibility into biodiesel through base catalyzed process can be a viable future alternative for blending into fossil diesel. Karanja biodiesel’s NOx emissions can be kept within the norms by implementation of EGR methodology.

13.

14.

15.

16.

methods for NOx reduction from biodiesel. SAE. Tech Paper; 2003-01-3205. Avinash Agarwal, K Rajamanoharan. Experimental investigations of performance and emissions of Karanja oil and its blends in a single cylinder agricultural diesel engine. Applied Energy 2009; 86(1): 106-112 H Raheman, AG Phadatare. Diesel engine emissions and performance from blends of karanja methyl ester and diesel. Biomass and Bioenergy 2004; 27: 393–397 Avinash Kumar Agrawal, Shrawan Kumar Singh, Shailendra Sinha , Mritunjay Kumar Shukla. Effect of EGR on the exhaust gas temperature and exhaust opacity in compression ignition engines. Sadhana 2004; 29(3):275–284. V Pradeep, R P Sharma. Use of hot EGR for NOx control in a compression ignition engine fuelled with bio-diesel from Jatropha oil. Renewable Energy 2007; 32:1136–1154. A Tsolakis, A Megaritis, ML Wyszynski, K Theinnoi. Engine performance and emissions of a diesel engine operating on diesel-RME (rapeseed methyl ester) blends with EGR (exhaust gas recirculation). Energy 2007; 32(11) : 2072-2080 Levendis YA, Pavlatos I, Abrams R. Control of diesel soot, hydrocarbon and NOx emissions with a particulate trap and EGR. SAE paper 940460. W H Kemp. Biodiesel Basics and Beyond: A Comprehensive Guide to Production and Use for the Home and Farm; ISBN13: 9780973323337 DT Hountalas, GC Mavropoulos, KB Binder. Effect of exhaust gas recirculation (EGR) temperature for various EGR rates on heavy duty DI diesel engine performance and emissions. Energy 2008; 33: 272–283.

REFERENCES DEFINITIONS, ABBREVIATIONS 1. IEA World Energy Outlook 2009. 2. BP Statistical Review of World Energy, June 2010. 3. A George, JY Ban-Weiss, A Chen, Bruce W Buchholz, Dibble Robert. A numerical investigation into the anomalous slight NOx increase when burning biodiesel: A new (old) theory. Fuel Processing Technology 2007; 88: 659–667. 4. www.biodiesel.org/pdf_files/fuelfactsheets/prod_q uality.pdf 5. Deepak Agarwal, Shailendra Sinha, Avinash Kumar Agarwal. Experimental investigation of control of NOx emissions in biodiesel-fueled compression ignition engine. Renewable Energy 2006; 31: 2356-2369. 6. C Kumar, M K G Babu, L M Das, Experimental Investigations on a Karanja Oil Methyl Ester Fueled DI Diesel Engine. SAE paper number 2006-01-0238 7. A K Pandey, M R Nandgaonkar. Investigation of Esterified Karanja Oil Biodiesel Fuel for Military Use on a 38.8L Diesel Engine. SAE paper Number: 2009-01-2806 8. J Szybist, J Simmons, M Druckenmiller, K Al-Qurashi, A Boehman, A Scaroni. Potential

ULSD: Ultra low sulfur diesel, diesel fuel with sulfur content less than 15 parts per million (ppm). Mtoe: Million tones of oil equivalent. A tone of oil equivalent (toe) is a unit of energy released by burning one tonne of crude oil, approximately 42 GJ. BTDC: Before Top Dead Center BTE: Brake Thermal Efficiency BSEC: Brake Specific Energy Consumption CI: Compression Ignition CO: Carbon monoxide CO2: Carbon dioxide EGR: Exhaust Gas Recirculation HC: Hydrocarbon KB100: 100% Karanja biodiesel KB20: 20% Karanja biodiesel+80% diesel. MTOE: NOx: Nitrogen oxides PM: Particulate matter RPM: Revolutions per minute SI: Spark Ignition %: Percentage

APPENDIX 1. Technical specification of AVL 437 smoke meter. 2. Technical specification of AVL Di-GAS analyzer.


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