studies on di diesel engine fueled with rice bran methyl ... · ethanol is a poor fuel for a diesel...

INTERNATIONAL JOURNAL OF APPLIED ENGINEERING RESEARCH, DINDIGUL Volume 1, No1, 2010

© Copyright 2010 All rights reserved Integrated Publishing Association

RESEARCH ARTICLE ISSN 09764259

206

Studies on Di Diesel Engine Fueled With Rice Bran Methyl Ester Injection and Ethanol Carburetion

Rambabu Kantipudi 1 , Appa Rao.B.V 2 , Hari Babu.N 3 , Satyanarayana.CH 4 1 Associate Professor, Department of Mechanical engineering ,

Sir CRR College of Engineering, Eluru 2 Professor, Department of Marine engineering , AU College of Engineering,

Andhra University 3 Professor, Department of Mechanical engineering. Aditya Engineering college, Tekkali

4 Professor, Department of Marine engineering, AU College of Engineering Andhra University [email protected]

ABSTRACT

The present research trend is to reduce the exhaust emissions from engines to suit the norms set by Euro/ Bharat Pollution boards. Replacement by renewable alternative fuels is simultaneous attempt to replce diesel fuel in view of possible depletion of petroleum reserves. Our context is to utilize biodiesel ( Rice bran methyl ester) as a total replacement to Petrol Diesel. It is proved that biodiesel reduces the engine emissiong but for the NOx which is emitted more than that when neat diesel fuel is implemented. This is the main reason to turn our attention to dual fuel operatio with ethanol fuel. In this work instead of heated air with the carburetion technique as attempted by the predecessors, on line heating of the fuel ethanol before its being cargureted at the suction end is tried with the view that the volumetric efficiency of the engine doesn’t suffer. Betterment in the engine performance and exhaust emission is observed at retrofit engine aimed at total diesel replacement is achieved with several benefits.

Key words: Rice bran methyl ester, Ethanol, carburetion, performance, emissions.

1. Introduction

The increasing industrialization and motorization of the world has led to a steep rise in the demand of petroleumbased fuels. Petroleumbased fuels are obtained from limited reserves. These finite reserves are highly concentrated in certain regions of the world. Therefore, those countries not having these resources are facing energy/foreign exchange crisis, mainly due to the import of crude petroleum. Hence, it is necessary to look for alternative fuels which can be produced from resources available locally within the country such as alcohol, biodiesel, vegetable oils etc. Ethanol is also an attractive alternative fuel because it is a renewable bio based resource and it is oxygenated, thereby providing the potential to reduce particulate emissions in compressionignition engines. Biodiesel is methyl or ethyl ester of fatty acid made from virgin or used vegetable oils (both edible and nonedible) and animal fat. The main resources for biodiesel production can be nonedible oils obtained from plant species such as Jatropha curcas (Ratanjyot), Pongamia pinnata (Karanj), Calophyllum inophyllum (Nagchampa), Hevea brasiliensis (Rubber) and edible oils like rice bran,soya bean etc. Biodiesel can be blended in any proportion with Petroleum diesel to create a biodiesel blend or can be used in its pure form. Just like petroleum diesel, biodiesel operates in compression ignition (diesel) engine, and essentially require very little or no engine modifications because biodiesel has properties similar




207

to petroleum diesel. It can be stored just like Petroleum diesel and hence does not require separate infrastructure. The use of biodiesel in conventional diesel engines results in substantial reduction in emission of unburned hydrocarbons, carbon monoxide and particulate. Ethanol is a poor fuel for a diesel engine because of its low ignition quality or cetane value. It is to be emphasized that a high octane fuel (a virtue for a petrol engine), necessarily has a low cetane value (a curse for a diesel engine). The flammability results of ethanol are higher than gasoline or diesel. More ethanol vapor has to be produced and mixed with air before a flammable mixture is produced. This factor together with ethanol’s high latent heat of evaporation , low vapor pressure and high boiling point , demands more energy to produce ethanol air mixture flammable. The main research in diesel alcohol technology is to find ways and means to force alcohol to ignite by compression in the diesel engine recognizing these fuel characteristics.

Anhydrous ethanol can be blended with diesel fuel, but several problems remain to be solved before diesohol can be considered a practical alternative [1,2]. The problems can be avoided by keeping the ethanol in a separate tank and injecting it into the air stream of the engine. This technique is called vaporization. It has been shown that it is possible to replace up to 60% of diesel fuel, using the vaporization method [3]. Adding a carburetor has been suggested as a relatively inexpensive way of vaporizing ethanol into a naturally aspirated diesel engine [4] when ethanol is carbureted into a naturally aspirated diesel engine, energy is required to vaporize the ethanol. An air preheater could supply the energy needed to achieve the complete evaporation. Though several researchers have reported the vaporization of ethanol in higher horse power engines [5, 6] there is no information on the use of vaporized ethanol in low horse power stationary engines. Since these types of engines are commonly used in the agricultural and transport sectors of developing countries, there is a need to study their performance using vaporized ethanol. The first objective of the study reported in the paper [7] was to investigate the effect of fuelling a constant speed low horsepower diesel engine with vaporized ethanol. The second objective was to study the effect of preheating the ethanol air mixture on engine performan.

In this study, the diesel fuel is replaced with neat Rice bran methyl ester (RBME). Heated Ethyl alcohol is carbureted at the suction end through a bifurcated suction arrangement. This attempt is made after surveying the previous work done on alcohol carburetion. Several vegetable oils are being produced in India however; it is desirable to give priority to that oil, which is not being used for human consumption in practice. Among vegetable oils rice bran oil can be used as CI engine fuel because rice is one of major crops cultivated in India. In spite of an annual production of 91 MMT rice grain with a theoretical potential of 1.2 MMT rice bran oil, the estimated production was only 0.7 MMT in 200405 (Solvent Extractors Association of India). Extra 0.5 MMT rice bran oil may be available for 10 percent replacement of diesel used in agriculture sector of India.

The exhaust gas temperature of the engine on all the blends of methyl ester of rice bran oildiesel was found to be lower than that of diesel at rated load. The emission of carbon monoxide from the engine was found to be lower on all the blends of methyl ester of rice bran oildiesel compared to diesel at rated load. The emission of unburnt hydrocarbon from the engine at higher loads was found to be more on all the fuel blends as compared to diesel. The emission of NOx from the engine found to be higher on the all fuel blends as compared to diesel [10].




208

RBME Injection & Preheated Ethanol Carburetion

In this study, dual fuel operation is adapted with RBME injection and preheated ethanol carburetion. As per the investigations mentioned earlier in the above said pages, the emission control is the main criterion. Neat Rice bran methyl ester has its own advantages and disadvantages and an attempt is made to rectify some of the problems in implementing the neat RBME. Attention is bestowed upon the reduction of HC, NO, and CO emissions and the same is successfully achieved with the preheated ethanol carburetion of 70.17mg/sec.Vibration on the engine cylinder in three directions and on the foundation is measured and analyzed to elicit information about the nature of combustion.

2. Experimental Setup

The experimental setup consisting of DI diesel engine available in the engines laboratory of department of Marine Engineering, Andhra University is utilized for the experimentation. Preheated Ethanol (heated to temperatures in between 40 0 50 0 C) is carbureted at the suction end through a bifurcated air duct along with the Rice bran methyl ester injection.

Figure1: Schematic diagram of experimentation




209

The amount of Ethanol is regulated by the throttle opening of the carburetor and the engine performance was tested at six different throttle openings. Various higher proportions of Ethanol is being tried to eliminate the knocking condition. Different mass flow rates of Ethanol viz. 195.90 mg/sec, 137.20 mg/sec, 106.90 mg/sec, 70.17 mg/sec, 48.45 mg/sec, 23.14 mg/sec were implemented at the six different throttle openings as mentioned earlier. 195.90 mg/sec mass flow rate is threshold flow value above which knocking becomes intensive (which is identified with sudden power loss and vibration severity) and hence higher mass flow rates above this percentage were discarded. Throttle opening more than this is forfeited. Experimentation is carried out at various engine loads by means of eddy current dynamometer. Engine performance data is acquired to investigate engine performance along with the engine pollution parameters.

Ethanol carburetor

Figure 2: Diesel Engine Test rig with Ethanol carburetion at the bifurcated air inlet with the preheating arrangement

Ethanol mass shares for six throttle positions of carburetor and for five loads are shown in table .1

Ethanol of Share Mass = RBME of mass Ethanol of Mass

Ethanol of Mass +

Preheater




210

Table 1: Ethanol mass shares for various throttle positions of carburetor.

Ethanol Mass Share (%) Combination 1

(Throttle position 1)

Combination 2


Combination 3


Combination 4


Combination 5


Combination 6


Ethanol mass flow rate

195.90 mg/sec 137.20 mg/sec 106.90 mg/sec 70.17 mg/sec 48.45 mg/sec 23.14 mg/sec

No load 67.58% 59.07% 51.73% 40.68% 32.23% 18.30%

1/4th load 66.02% 55.70% 44.63% 34.22% 25.78% 13.41%

Half load 59.08% 48.36% 37.74% 28.36% 21.00% 10.72%

3/4th load 50.17% 39.35% 31.10% 22.51% 16.17% 8.09%

Full load 42.71% 32.85% 26.50% 18.82% 12.93% 6.49%

3. Engine, Pollution Measurement, and Fuel Specifications

3.1. Engine details

Table 2: Specifications for Kirlosker Diesel engine

Rated Horse power: 5 hp (3.73 kW)

Rated Speed: 1500rpm

No of Strokes: 4

Mode of Injection and injection pressure

Direct Injection,200 kgf/cm 2

No of Cylinders: 1 Stroke 110 mm

Bore 87.5 mm

Compression ratio 16.5




211

3.2. Pollution measurement

MRU Exhaust gas analyzer, Delta 1600L calibrated with propane.

3.3. Fuel properties Table 3: Properties of Diesel, Rice bran methyl ester and Ethanol

Sl.No Name of the oil sample →

↓Characteristics

Diesel Rice bran methyl ester

Ethanol

1 Density @ 33 0 c (kg/m 3 ) 833 868.6 783.2 2 Lower calorific value (kJ/kg) 43000 38552 26855 3 Cetane number 51 63.8 8 4 Kinematic viscosity @ 33 0 c (cSt) 2.58 3.57 1.2 5 Conradson’s Carbon Residue

(Wt %) 0.1 0.35

6 Stoichometric air –fuel ratio 15 13.8 9 7 Latent heat of evaporation (kJ/kg) 250 840 8 Flash point ( 0 c) 68 185 9 Fire point ( 0 c) 72 196

4. Results and Discussions

4.1. Engine Performance

Figure 3: Specific fuel consumption of RBME & Diesel with respect to Equivalence ratio of RBME & Diesel for various Ethanol combinations




212

Figure 4: Specific Energy consumption of total fuel with respect to Equivalence ratio of RBME & Diesel for various Ethanol combinations

Figure 5: Brake thermal efficiency with respect to Equivalence ratio of RBME & Diesel for various Ethanol combinations




213

Figure 6: Load verses Specific fuel consumption of RBME & Diesel for Ethanol equivalence ratio.

Figure 7: Load verses Specific Energy consumption for Ethanol equivalence ratio




214

Figure 8: Load verses brake thermal efficiency for Ethanol equivalence ratio.

Figure 9: Load verses Brake thermal efficiency

Ethanol involves high velocity combustion and as ethanol flow rate increases the combustion velocities obviously increase. This high velocity combustion decreases some of the exhaust emissions with lesser NO emission at all loads because of involvement of cold flame. The brake thermal efficiency increased with the load on the engine and the same is increasing with the increase of ethanol flow rate for 3/4th load and full load, but decreasing with the increase of ethanol flow rate for 1/4 th load and half load (fig.5, fig.8 & fig.9). At smaller ethanol mass




215

shares which normally occur at higher loads like ¾ th load and full load, the thermal efficiency at higher flow rates of ethanol is reached maximum and as the flow rate decreases the thermal efficiency also decreases converging to the brake thermal efficiency of neat biodiesel operation. At lower loads because of incomplete combustion, which can be gauged by HC release in exhaust gas, the brake thermal efficiency is low at high ethanol flow rates and progressively it increases with the decrease of ethanol flow rate, which lead to better ethanol ratio finally to govern the combustion. Brake thermal efficiency dipped at higher loads as calculated and presented in fig. 5. The engine is trying to tackle the load with higher consumption of biodiesel and as a consequence the thermal efficiency graph is running flat and the RBME equivalence ratio is increasing at full load.

Specific fuel consumption of RBME decreases with load and further decreases with the increase of ethanol (fig.3 and fig.6). At higher ethanol flow rates the specific fuel consumption drop is widened indicating higher biodiesel energy saving.

Table 4. Energy saving in terms of kJ/sec when ethanol is carbureted at full load.

RBME mg/sec +Ethanol mg/sec

RBME saving mg/sec

Ethanol mg/sec

RBME saving in kJ/sec

Ethanol in kJ/sec

Net saving in kJ/sec

% energy saving

187.68 +195.90 166.85 195.9 6.43 5.27 1.17 8.53

236.55 +137.20 117.98 137.2 4.55 3.69 0.86 6.29

270.76 +106.90 83.77 106.9 3.23 2.87 0.36 2.60

290.50 + 70.17 64.03 70.17 2.47 1.89 0.58 4.26

314.48 + 48.45 40.05 48.45 1.54 1.30 0.24 1.77

333.82 + 23.14 20.71 23.14 0.80 0.62 0.18 1.29

Specific energy consumption (due to ethanol, RBME, diesel) decreases with load and is further decreased with increase of ethanol flow rate at high loads (fig.4 and fig.7). . Table 4. is showcasing energy saving in terms of kJ/sec when ethanol is carbureted at full load. When the ethanol flow is maximum and when the engine is running at full load, the energy saving is also maximum i.e. up to 8.53%.The energy saving percentage gradually decreased with the decrease in the flow rate of ethanol to reach 2.60% for the ethanol flow rate of 106.9 mg/sec. For the ethanol flow of 70.17 mg/sec, the energy saving picked up again to 4.26% finally fall down to 1.29% for the ethanol flow rate of 23.14 mg/sec. There is obvious sign of better combustion when ethanol is carbureted at full load, since the energy saving remained positive all through.




216

Specific energy consumption increases with increase of ethanol flow rate at lower loads because of incomplete combustion of ethanol at higher mass shares.

4.2. Engine Exhaust emissions

4.2.1. Hydrocarbons Emission

The HC release in the exhaust is increasing with the increase of ethanol flow as shown in fig.10 at every load tested on the engine. Especially at low loads HC emission is very high for higher ethanol flow rates, because of incomplete combustion of ethanol at higher ethanol mass shares at lower loads. Low thermal efficiencies recorded for higher ethanol flow rates at lower loads in fig.9 are supporting the above statement.

Figure 10: Hydrocabon emission in the exhaust

At no load, the HC release in the case of alcohol flow of 195.90 mg/sec is 4413 ppm and for diesel it is 74 ppm. As the graph envisages, the emission of HC is decreasing with the decrease of the alcohol flow and at 70.17mg/sec alcohol flow, the HC emission is minimum amongst the alcohol combinations tested. Of course, for the neat methyl ester implemented on the engine, the HC emission is minimum i.e. 16ppm.In the same way at the full load running of the engine, for highest flow of ethanol the HC emission is 256ppm and minimum emission of HC is 37ppm recorded at 70.17 mg/sec ethyl alcohol flow. For neat diesel application it is 96ppm. Hence it can be concluded that the ethanol flow rate of 70.17 mg/sec encourages combustion refinement by its participation in the combustion. This particular flow rate of ethanol is observed to be working at all loads in reducing the HC emission in the exhaust.

INTERNATIONAL JOURNAL OF APPLIED ENGINEERING RESEARCH Volume 1, No2, 2010



217

4.2.2. Nitric Oxide emission

Figure 11: NO emission in the exhaust

The flow rate 70.17mg/sec of ethanol has shown NO emission in a better way than that of diesel and the methyl ester. With this ethanol flow rate, the reduction of NO emission at full load is 201 ppm when compared to the neat RBME implementation. At other loads i.e. at no load, ¼ th load, half full load and 3/4 th full load the decrease in emission is observed to be 77 ppm, 212 ppm, 369 ppm respectively and as shown in fig.11, the NO emission is far lesser than when pure RBME fuel is implemented. Normally it is learned from the literature that biodiesel fuel emits more NO than the diesel fuel at all loads. But for this, in all other emissions the biodiesel is a merited one. The biodiesel oil’s emission reducing characteristic is fully justified with the carburetion of 70.17mg/sec for this particular engine and biodiesel.

4.2.3. Carbon monoxide Emission

Figure 12: CO emission in the exhaust




218

Carbon Monoxide emission is increasing with the increase of ethanol content. There is an exception for the ethanol flow rate of 70.17 mg/sec. The CO emission in the exhaust is consistently minimum at all loads for the flow rate of 70.17mg/sec, as shown in fig.12. At full load, 0.03% absolute fall is there in this emission when it is compared for the 70.17mg/sec ethanol flow rate combination and neat biodiesel usage.

4.2.4. Carbon dioxide Emission

Figure 13: CO2 emission in the exhaust

It is observed from the fig.13, increasing the ethanol flow rate is decreasing the CO2 emission at any load in general. The main reason of CO2 reduction is low C/H ratio and high oxygen content of the RBME and ethanol combinations. The CO2 is consistently low at all loads for 70.17 mg/sec ethanol flow rate. Biodiesel is known for green house gas reduction and now it can be observed that the emission with the implementation of 70.17mg/sec flow rate of ethanol further reduces green house gas emission. From the fig.5.40 , the absolute difference in percentage emission of CO2 from no load to full load spanning five loads are 0.64, 1.7, 2.1, 1.2, and 1.3 respectively. This combination also reduces this emission considerably with that of diesel implementation.

4.2.5. Exhaust gas Temperature

It is observed that the exhaust gas temperature is decreasing with increasing ethanol flow rate at any load (fig.14).This is because of high latent heat of vaporization of ethanol. From no load to full load, the exhaust gas temperature are observed to be 4 0 C, 21 0 C, 28 0 C, 40 0 C, and 29 0 C more with biodiesel in comparison with 70.17 mg/sec of ethanol flow rate combination.




219

Figure 14: Load verses Exhaust gas temperature

4.2.6. Smoke in the exhaust

Load Vs Smoke

48

48

49 53

53

37 40

47 49

49

49

48

49 53

53

48 52

51 53 55

40 42

49 53

55

40

47

42

49 53

49 51

51 53

61

51

51 55

55

63

0

10

20

30

40

50

60

70

No load 1/4th load Half load 3/4th load Full load

Smoke (HSU

).

RBME+195.90mg/sec Ethanol RBME+137.20mg/sec Ethanol RBME+106.90mg/sec Ethanol RBME+ 70.17mg/sec Ethanol RBME+ 48.45mg/sec Ethanol RBME+ 23.14mg/sec Ethanol RBME DIESEL

Figure 15: Smoke emission in the exhaust

The smoke levels with neat RBME application are less than that of with neat diesel at all loads (fig.15). Ethanol addition marginally reduced the smoke values at all loads tried on the engine. The flow rate of 137.20 mg/sec of ethanol with the biodiesel combination produced smoke levels in the exhaust less than 50 Hatridge smoke units at all loads. This combination is also merited with lesser NO emission in the exhaust at all loads and especially at full load.




220

5. Conclusions

1. Higher thermal efficiencies are observed at higher replacement of RBME with ethanol at higher loads. 2. SFC consumption has flattened and the equivalence ratio span has reduced encompassing all loads with respect to more RBME replacement with ethanol. 3. Engine is operating at lower equivalence ratios at higher ethanol flow rates. There is higher energy saving at higher ethanol flow rates at full load. But the flow rate of 70.17 mg /sec is the optimal flow rate considering all engine properties to be investigated. HC emissions are increased with increased ethanol induction. 4. The specific energy consumption (encompassing the heat ratings of both the fuels) has increased at lower loads with the increase of ethanol flow rate. The same specific energy consumption is decreasing at higher loads with the increase of ethanol flow rates. 5. The NO emission in the exhaust is decreasing with the increase of ethanol 6. Carbon Monoxide emission is increasing with the increase of ethanol content. 7. Increasing the ethanol flow rate is decreasing the CO2 emission at any load in general 8. It is observed that the exhaust gas temperature is decreasing with increasing ethanol flow rate at any load. 9. Exhaust emissions have decreased appreciably especially at 70.17 mg/sec flow rate of ethanol in the dual fuel operation. NO increase is generally accepted for the biodiesel application. But the addition of ethanol has brought relief to more NO emission.

6. Acknowledgement

The author thanks Prof. B.V.Appa Rao, Department of Marine Engineering, Andhra University,Visakhaptnam for the unstinted support in guiding my research in this field.

7. References

1. Wrage, K. E. and Goering, C. E., Technical feasibility of diesohol, Agricultural Engineering, 1979, 60(10), pp34 36.

2. Boruff P. A., Schwab A. W., Goering C. E. and Pryde, E. H., Evaluation of diesel fuel ethanol micro emulsions, Transactions of the ASAE, 1982, 25(1), pp 4753

3. Goering C.E, Crowell TJ, Griffith DR, Jarrett MW, Savage LD. Compressionignition, flexiblefuel engine. Transactions of the ASAE, 1992, 35(2), pp 423428.

4. Goering, C. E. and Wood, D. R., Over fuelling a diesel engine with carbureted ethanol, Transactions of the ASAE, 1982, 25(3), pp 576580.

5. Chaplin, J. and Janius, R. B., Ethanol fumigation of a compression ignition engine using advanced injection of diesel fuel, Transactions of the ASAE, 1987, 30(3), pp 610614.

6. Sarkkinen, K., Alcohol for automobiles, Indian Auto, 1997, 7(4), pp 2021.




221

7. E. A. AJAV, BACHCHAN SINGH and T. K. BHATTACHARYA,” Performance of a Stationary Diesel Engine using Vapourized Ethanol as Supplementary Fuel” Biomass and Bioenergy Vol. 15, No. 6, pp. 493502, 1998

8. Stumborg, M. A., Investigations of alternate fuel control parameters for a diesel engine, Canadian Agricultural Engineering, 1989, 31, pp 2533.

9. Alexandrain, M. and Schwalm, M., Comparison of ethanol and gasoline as automotive fuels. In Am. Soc. Mech. Eng... Winter annual meeting Anaheim, CA, USA, publ. by ASME, NY, USA, 1992, pp. 110.

10. Jayant Singh, T. N. Mishra, T. K. Bhattacharya, and M. P. Singh ‘Emission Characteristics of Methyl Ester of Rice Bran Oil as Fuel in Compression Ignition Engine’ International Journal of Chemical and Biomolecular Engineering Volume 1 Number 2, pp 6367

11. Tat, M.E. and Van Gerpen, J.H. (1999) “The kinematic Viscosity of Biodiesel and its blends with Diesel Fuel”. Journal of American Oil Chemists Society, Vol.76.No.12, pp 15111513.

12. Tat, M.E. and Van Gerpen, “The Specific gravity of Biodiesel and its blends with Diesel Fuel”. Journal of American Oil Chemists Society, Vol.77, No.2, 115119.

13. K. M. Chun and J. B. Heywood. “Estimating heatrelease and massofmixture burned from sparkignition engine pressure data”. Combustion Sci. and Tech., Vol. 54: pp 133–143, 1987.

studies on di diesel engine fueled with rice bran methyl ... · ethanol is a poor fuel for a diesel...

Documents