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A comparative study on exhaust emissions from high grade low heat rejection diesel engine with pongamia oil based bio diesel.

Introduction

The major pollutants emitted from diesel engine are smoke and oxides of nitrogen (NOx). Excessive breathing of smoke causes (Sharma, 1996: Fulekar, 1999) tuberculosis and may also lead to death. It also causes detrimental effects on animal and plat life besides environmental (Khopkar, 1993) disorders. Inhaling of oxides of nitrogen causes dizziness, vomiting sensation, severe headache etc. Hence globally, stringent regulations are made for permissible pollutants in the exhaust of the engines. It is well known fact that about 30% of the energy supplied is lost through the coolant and the 30% is wasted through friction and other losses, thus leaving only 30% of energy utilization for useful purposes. In view of the above, the major thrust in engine research during the two decades has been on development of low heat rejection engines. Several methods adopted for achieving low heat rejection to the coolant were using ceramic coatings (Krishnan et al., 1980) on piston, liner and cylinder head and creating air gap in the piston (Rama Mohan, 1995) and other components with low-thermal conductivity material like superni, mild steel etc. However, this method involved the complication of joining two different metals. A few researchers (Jabez Dhinagar, 1993) used different crown materials with different thickness of air gap in between the crown and the body of the piston. As the cetane number of the vegetable oils is closer to that of diesel fuel, attempts were made to induct vegetable oils in the forms of crude vegetable oil (Rehaman, 1995) emulsified form (Kiannejad. F.et al. 1993) and bio-diesel (Annapurna Devi, N. et al, 2006) in the conventional engine. However, due to high viscosity of the vegetable oil, these vegetable oils were used in low heat rejection (Bhaskar, T.et . al. 1993: Murali Krishna, 2005) diesel engines. However, no systematic investigations are reported so far about the use of crude vegetable oil in low heat rejection diesel engines which consist of different degree of insulation and hence attempt is made in this direction and the pollution levels are reported and compared with pure diesel operation.

Experimental program

The low heat rejection (LHR-1) diesel engine contains two-part piston-the top crown made of low thermal conductivity material, superni-90 (an alloy of nickel) screwed to aluminum body of the piston, providing a 3mm-air gap in between the crown and the body of the piston. The optimum thickness of air gap in the air gap piston is found to be 3 mm (Rama Mohan, 1995) for better performance of the engine with superni inserts with diesel as fuel. A superni-90 insert is screwed to the top portion of the liner in such a manner that an air gap of 3-mm is maintained between the insert and the liner body. Investigations are also conducted on LHR-2 engine which consists of partially stabilized zirconium (PSZ) of thickness 500 microns sprayed on inner side of cylinder head and assembled with air gap insulated piston with superni crown and air gap insulated liner with superni inserts. At 500[degrees]C the thermal conductivity of superni-90 and air are 20.92 and 0.057 W/m-K respectively.

Fig. 1 shows the experimental set up. The conventional engine is four-stroke, water cooled diesel engine with 3.68 kW at a rate speed of 1500 rpm having compression ratio of 16:1. The engine is connected to electric dynamometer for measuring brake power of the engine. The variable carburetor is installed at the inlet manifold of the engine to induct methanol at different percentages of pure diesel at peak load operation of the engine. Jatropha oil substituted 100% for diesel fuel is used as fuel injected in the cylinder in conventional manner. Two burettes are arranged for finding fuel consumption of the methanol and crude jatropha oil. Air-consumption of the engine is measured by air-box method. The naturally aspirated engine is provided with water-cooling system in which inlet temperature of water is maintained at 60[degrees]C by adjusting the water flow rate. The injection pressures are varied from 190 bars to 270 bars (in steps of 40 bars) using nozzle-testing device. The exhaust gas temperature (EGT) is measured with thermocouple made of iron and iron-constantan. Pollution levels of smoke and oxides of nitrogen (NOx) are recorded by AVL smoke meter and Netel Chromatograph NOx analyzer respectively at the peak load operation of the engine. Pongamia based bio-diesel substituted 100% for diesel fuel is used as fuel in the investigations. The experiments are conducted on conventional engine (CE)--engine with air gap insulated piston and air gap insulated liner (LHR-1) and engine with air gap insulated piston, air gap insulated liner and ceramic coated cylinder head (LHR-2). Results are compared with pure diesel operation on conventional engine. The properties of bio-diesel are given in reference(11).

[FIGURE 1 OMITTED]

Results and Discussion

Smoke levels: The data of variation of smoke levels at peak load with conventional engine and Low Heat Rejection (LHR) engines at normal temperature of the vegetable oil and at different injection pressures is shown in Table-1. Drastic increase of smoke levels is observed at the peak load operation in both versions of engine at different operating conditions of the vegetable oil, compared to pure diesel operation engine on conventional engine. This is due to the higher magnitude of the ration C/H, (C-Number of carbon atoms, H-Number of hydrogen atoms in the composition of the fuel) when compared with pure diesel. The increase of smoke levels is also due to decrease of air-fuel ratios and volumetric efficiency with vegetable oil operation compared with pure diesel operation.

Smoke levels are proportional to the density of the fuel. Since vegetable oils have higher density compared to diesel fuels, smoke levels are higher with vegetable oils. However, LHR engines marginally decreased smoke levels due to efficient combustion and less amount of fuel accumulation on the hot combustion chamber walls of the LHR engines at different operating conditions of the vegetable oil compared to the conventional engine. Smoke levels decreased with increase of injection pressure, in both versions of the engine, at normal temperature of the vegetable oil. This is due to improvement in the fuel spray characteristics at higher injection pressures and increase of air entrainment causing lower smoke levels.

NOx levels: The data of variation of oxides of nitrogen (NOx) levels at peak load with different versions of the engine at normal temperature of the vegetable oil and at different injection pressure is shown in Table-2, NOx levels are lower in the conventional engine while they are higher in the LHR engine with esterfied vegetable oil at peak load when in comparison with pure diesel operation. This is due to lower heat release rate because of high duration of combustion causing lower gas temperature with vegetable oil operation on conventional engine, which reduced NOx levels.

Increased injection pressures decreased NOx levels in LHR engine while they increased in conventional engine due to decreased of gas temperatures in LHR engines and increase of the same in the conventional engine.

Conclusions

Vegetable oil operation at 27[degrees]bTDC on conventional engine showed the deterioration in the performance, while LHR engines showed similar performance, when compared with pure diesel operation on conventional engine. Increase of injection pressure increased efficiency and decreased pollution levels

Acknowledgements

The authors are thankful to the authorities of Chaitanya Bharathi Institute of Technology, Hyderabad for providing facilities to carryout this work. The financial assistance provided by the All India Council for Technical Education, New Delhi is also gratefully acknowledged.

References

[1] Sharma, B.K. 1996, Engineering Chemistry, Pragathi Prakashan (P) Ltd., Merut.

[2] Fulekar, M.H. 1999, Chemical Pollution- a threat to human life, Indian J.Environ, Prot., 1(3): 353-359

[3] Khopkar, S.M., 1993, Environmental Pollution Analaysis, New Age International (P) Ltd, Publishers, New Delhi.

[4] Krishnan, D.B. et al. 1980. Performance of an Al-Si graphite particle composite piston in a diesel engine. Transactions of Wear, 60(2): 205-215.

[5] Rama Mohan, K. 1995. Performance evaluation of an air gap insulated piston engine. Ph.D. Thesis, Kakatiya University, Warangal.

[6] Jabez Dhinagar, S., Nagalingam, B. and Gopala Krishna, K.V. 1993. A comparative study of the performance of a low heat rejection engine with four different levels of insulation. International Conference on Small Engines and Fuels. Chang Mai, Thailand. Proceedings, pp 121-126.

[7] Rehman, A. and Singhai, K.C. 1995. Vegetable oils as alternate fuels for diesel engine. IV Asian -Pacific International Symposium on Combustion and Energy Utilization. Hong Kong. Proceedings, pp 924-928.

[8] Kiannejad, F., Crookes R.J. and Nazha, M.A.A. 1993. Performance and emissions of a 1.5 litre single cylinder diesel engine with low cetane number vegetable oil fuel and emulsification with water. IV International Conference on Small Engines and Fuels. Chang Mai, Thailand. Proceedings, pp 32-39.

[9] Annapurna Devi, N. et al. 2006. Production and evaluation of bio-diesel from Sunflower and Nigerseed oil with performance studies on a diesel engine. International Congress on Renewable energy-2006. Proceedings, pp 478-484.

[10] Bhaskar, T.et al. 1993. The effect of two ignition improving additives on the performance of oil in low heat rejection diesel engine. IV International Conference on Small Engines and their Fuels. Thailand. Proceedings, pp 1419.

[11] Murali Krishna, M.V.S. 2004. Investigations on low heat rejection diesel engine with alternate fuels. Ph.D Thesis. J.N.T. University, Hyderabad.

[12] Murali Krishna, M.V.S., Ratna Reddy, T. and Murthy, P.V.K. 2005. Studies on Exhaust emissions from low heat rejection diesel engine with carbureted ethanol and Pongamia oil", Indian J. Env. Prot., 25(12): 1101-1108.

P.V. Krishna Murthy (1), C.M. Vara Prasad (2), A.V. Sita Rama Raju (3) and M.V.S. Murali Krishna (4)

(1) Principal, Gnyana Saraswati Colllege of Engineering and Technology, Dharmaram (B), Dichpally, Nizamabad--503 230 Andhra Pradesh, India E-mail: krishshnamurthy venkata@yahoo.co.in

(2) Principal CRV College of Engineering and Technology, Shameerpet, Hyderabad-56

(3) Professorf Mechanical Engineering Department, J.N.T. U College of Engineering, Kakinada-533003

(4) Associate Professor, Chaiatanya Bharathi Institute of Technology, Gandipet, Hyderabad-500075
Table 1: Data of smoke levels with conventional engine and Low Heat
Rejection Engine at peak load operation with different test fuels.

Smoke levels (Hartridge smoke units, HSU)

                      Pure Diesel operation

                      Injection Pressure (bar)
      Engine
      Version             190   230   270
Conventional Engine       48    38    34
LHR-1                     68    53    58
LHR-2                     65    60    55

                      Esterfied pongamia oil
                           operation

                      Injection Pressure (bar)
      Engine
      Version           190   230   270
Conventional Engine     66    62    55
LHR-1                   50    48    46
LHR-2                   50    45    40

LHR-1 -Air gap insulated piston, air gap insulated liner

LHR-2 -Air gap insulated piston, air gap insulated liner and ceramic
coated cylinder
head.

Table 2: Data of NOx levels with different versions of the engine
at peak load operation with different test fuels.

NOx levels (ppm)

Engine                Pure Diesel Operation
Version
                      Injection Pressure (bar)

                        190    230    270

Conventional Engine     850    890    930
LHR -1                  1300   1280   1260
LHR-2                   1400   1380   1360

Engine                 Esterfied Pongamia Oil
Version                      Operation

                      Injection Pressure (bar)

                        190    230    270

Conventional Engine     850    890    920
LHR -1                  1250   1230   1190
LHR-2                   1275   1205   1165

LHR-1 -Air gap insulated piston, air gap insulated liner

LHR-1 -Air gap insulated piston, air gap insulated liner
and ceramic coated cylinder head.
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Article Details
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Author:Murthy, P.V. Krishna; Prasad, C.M. Vara; Raju, A.V. Sita Rama; Krishna, M.V.S. Murali
Publication:International Journal of Applied Environmental Sciences
Article Type:Report
Geographic Code:1USA
Date:Jun 1, 2009
Words:1873
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