Advanced Materials Research Vol. 795 (2013) pp 164-169 © (2013) Trans Tech Publications, Switzerland doi:10.4028/www.scientific.net/AMR.795.164
Performance and Emission Characteristics of Diesel Engine Running on Blended Palm Oil A.M. Iqbal1,2*, Z.A. Zainal2, M. Mazlan1, A.M. Mustafa Al-Bakri3, M.S. Salim4 1
Faculty of Mechanical Engineering, Universiti Teknologi MARA,Permatang Pauh, Pulau Pinang, Malaysia. 2
School of Mechanical Engineering, Universiti Sains Malaysia Eng. Campus, Pulau Pinang, Malaysia.
3
Center of Excellence Geopolymer & Green Technology (CEGeoGTech) School of Materials Engineering, University Malaysia Perlis 4
School of Mechatronic Engineering, University Malaysia Perlis
[email protected] (corresponding author)
Keywords: Palm Oil; Bio-fuels; Renewable Energy
Abstract Rapid increasing of industrialization and motorization has led arising of petroleum and energy demand. This pursue a new energy blends to cater the depletion of fossil fuel and the environmental degradation condition. Malaysia is blessed, which has suitable climate to plant alternative fuel (palm oil) and become one of the largest exporters to the world. Palm oil in its refined form as cooking oil has high energy content which can be adopted as an alternative to the petroleum based fuel. This paper evaluates the performance and emission characteristics of refined palm oil (RPO) as a fuel to the diesel engine. Palm oil and its blends composition with 20%, 40%, 60% as well as pure palm oil (100%) and diesel were tested separately under various engine loads. Five series of tests data on each type of fuel were analyzed and compared. Moreover, by increasing the percentage of RPO in blends would lead a character of higher percentage in density and viscosity. Studied revealed that the small percentage of RPO composition promises a good thermal efficiency together with the emission released. Introduction Palm oil, an alternative to compression ignition (CI) engine, is a renewable energy resource and can be mixed with diesel fuel when applied in a diesel engine with little or without modification. From this point of view, there have been many experimental investigations done on the combustion and emissions characteristics of neat and blends palm oil in the diesel engine [1-5].The issues of emission release such as nitrogen oxide (NOx), carbon monoxide (CO) and unburned hydrocarbon (HC) as combustion product fuelled from blended palm oil is seen closely related to the engine performance. Palm oil composition also produced higher CO and NO emissions [8]. This is such related of fuel mixing process which highly affected by higher viscosity and difficulty in atomization for higher compound fuel. Other researchers have mentioned used other plant oil (rubber seed oil, coconut oil) to be used, together with preheating method as remedy to viscosity [9, 10]. However, the preheated plant oil can be adapted well and it gives similar performance as non-preheated. Therefore, preheated palm oil study will not be done in this work. This paper will investigate Malaysia targeted mixed energy from refined palm oil blends to be used in CI engine. Furthermore, the relations to engine performance and emissions such as the brake thermal, brake specific fuel consumption CO and NOX formation will be investigated.
All rights reserved. No part of contents of this paper may be reproduced or transmitted in any form or by any means without the written permission of TTP, www.ttp.net. (ID: 218.111.223.86, Universiti Malaysia Perlis (UniMAP), Kangar, Malaysia-30/07/13,10:45:48)
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Experimental Setup Performance and emission tests were conducted in a two-cylinder naturally aspirated diesel engine modified to be operated at a constant speed of 1500 rev/min. Table 1 shows the engine specification of the unmodified engine. Electrical heaters were used to apply different loads on the engine. The voltage and current were displayed on control panel and the electrical power developed was calculated. The measurement of volumetric fuel consumption is based on the time for the flow of 20 mL in a burette. The exhaust temperatures were monitored by a probe which was located at the exhaust pipe. The gas analyzer (SPTC, Gas & Smoke) was used to measure the exhaust gas emissions of CO, NOx and HC concentrations. Figure 1 shows the experimental setup for engine performance and emission. Table 1 : Engine-generator specification Parameters Model Fuel Type Capacity Engine continuous power Cooling system Alternator rated AC power Voltage Dry weight (Kg)
Specifications :KUBOTA ASK-R3100-50-B :Diesel :Two-cylinder, 4-stroke,direct injection diesel :931cc :10.3kW @ 2200rpm (without speed modification) :Radiator-cooled :8kW@3000 RPM :15.2Amp @ 50Hz each phase :220V :315
Fig. 1 : Schematic diagram of experimental setup for engine study The density was determined by using a specific weighing probe where a constant volume of certain oil is weighed. For the fuel viscosity, the neat diesel and various palm oil blends were measured using a digital viscometer (Brookfield, DV-I+). The calorific value was determined using an adiabatic bomb calorimeter (Yoshida Seisakusho, 1013-B) and the specification are shown in Table 2. In addition, the physical properties of palm oil and its blends were studied in accordance with ASTM standards.
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Table 2 : Bomb calorimeter specification Parameters Model Power source Max. power consumption Stirring speed Transformer for ignition Stirrer motor Thermometer for measuring Thermometer for hot water Bomb
Hot water tank thermo-control
Specifications :YOSHIDA SEISAKUSHO 1013-B :AC100V, 1ø 50 :750 W :Outer tank: 1800 rpm, Inner cylinder: 800 rpm :20 V, 1 A (self contained) :40 W synchronous motor, AC100 V :Beckman thermometer (scale div. 1/100 °C) :1 pcs. 100 °C (scale div. 1 °C) :Stainless steel (SUS-304) with automatic closing valve :Pressure proof 200 kg/cm2 :Capacity 300 cc :High sensitivity thermostat (0-100 °C)
Result and Discussion Fuel Properties The density, viscosity and the calorific value measurements of diesel and its blend
with palm oil are given in Table 1. Higher viscosity would significantly affect the fuel spray structure due to poor atomization. The viscosity of the cooking palm oil is 85 mm2/s, which means 71.1 % increase compared to diesel fuel as also noted by other researchers [5]. It can be seen that viscosity and density of P20 has close to diesel condition. As fuel injection system is volume metering basis, hence higher density would lead to deliver more of mass of fuel. Table 3 : Fuel properties of cooking palm oil-diesel blend
P100
Density kg/m³ 904
Calorific value (kJ/kg) 39,027
Viscosity at 27oC (mm²/s) 84.99
Viscosity reduction (%) `-
P60
882
41,184
45.90
45.99
P40
863
41,558
27.32
67.86
P20
855
42,840
24.55
71.12
Diesel
840
43,379
13.95
-
Sample
Engine Performance Engine test were carried out separately using diesel and its blends with palm oil at varying load. The brake thermal efficiency, an indication of performance increases when the load increases. As predicted, the average thermal efficiency of neat diesel is better at all loads (Figure 2a). The maximum brake thermal efficiency of P20 was 22.4 % compared to 22.2 % for diesel. The similarity is due to their similar fuel properties. The same trends occur for brake thermal efficiencies for P40, P60 and P100 being less than that for diesel, due to the lower calorific value for every increment of palm oil composition in the blends. Thermal efficiency also reflects the combustion characteristics at which maximum contact of fuel with air during the fuel spraying process leads to a better performance. Due to high viscosity of palm oil, the air-fuel mixing is affected by the difficulty in vaporizing the fuel resulting in lower tip penetrations and smaller cone angles as the ratios of blend increase. The comparison of specific fuel consumption for various blends of palm oil and diesel fuel is shown in Figure 2b. The diesel shows the lowest fuel consumption at all loads whilst P20, P40 and P100 were observed to be slightly higher. In all cases, the neat palm oil, P100 shows the highest fuel consumption rate at all loads. The combination effect of higher density and calorific value has
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led to this phenomenon. The lower energy content required a larger mass of fuel as energy input into the engine [6, 7]. This trend is also reported by other researcher [9] while using a vegetable oil in diesel engine. Figure 2c shows the exhaust gas temperature at varying load for various blend ratios. In general, increasing the load will increase the exhaust gas temperature. It was found that the exhaust gas temperature is always higher for diesel than the various blend ratios as load increase. The main reason for this phenomenon is due to the high calorific value and better spray performance for diesel fuel that lead to better combustion performance. Specific Fuel Consumption (kg/kWh)
Brake Thermal Efficiency (%)
24 22 20 18 16 Diesel P20 P40 P60 P100
14 12 10 8
1.0
Diesel P20 P40 P60 P100
0.8 0.6 0.4 0.2 0.0
0
1000
2000
3000
4000
5000
6000
0
1000
2000
Load (Watt)
3000
4000
5000
6000
Load (Watt)
(a)
(b)
Exhaust Temperature(oC)
450 Diesel P20 P40 P60 P100
400 350 300 250 200 150 100 0
1000
2000
3000
4000
5000
6000
Load (Watt)
(c) Fig. 2 : Comparison of (a) brake thermal, (b) specific fuel consumption and (c) exhaust temperature with load for different value of palm oil- diesel blended fuel in engine. Engine Emissions Carbon monoxide emission for P20, P40, P60 and P100 were slightly higher than diesel over a broad range of load as shown in Figure 3a. At low load, the CO emission of P100 was the highest compared to other blend ratios. The minimum and maximum CO produced was 0.01-0.17 % for P100. The CO emission data support correlation between density and atomization process. In consequence, partial load reveal a poor spray characteristics at higher blends and resulted a rich mixture in engine, and promote incomplete combustion. In Figure 3b with respect to NOx emission, there are two significance conclusions that can be made. First, the NOx emission increases with increasing load due to higher combustion temperature hence increases thermal efficiency and NOx emissions. Secondly, the lower NOx emission in the case of palm oil (P100) at partial load is due to its low calorific value resulting in lower combustion temperature. Late ignition delay is another factor that causes low temperature for palm oil blends due to combination of lower calorific value and poor break up in the spray. Unburned hydrocarbon (HC) consists of incomplete combustion comprising of actual carbon and product of complex reaction. The concentration of HC is shown in Figure 3c.In the figure, palm oil blends produce higher HC emission release compared to diesel fuel. It was found that HC emission is always higher in P100 than neat diesel at all loads. The HC emissions of P20 and P40 were lower in partial engine load, but higher at high engine load.
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In summary, the use of neat palm oil (P100) in diesel engine would give an adverse effect in performance together with high emission. P20 and P40 show more encouraging emission results and compete well with neat diesel. 350
0.25 Diesel P20 P40 P60 P100
0.15
Diesel P20 P40 P60 P100
300 250
NOx (ppm)
CO (%)
0.20
0.10
200 150 100
0.05
50
0.00 0
0
1000
2000
3000
4000
5000
0
6000
1000
2000
3000
4000
5000
6000
Load(Watt)
Load (Watt)
(b)
(a) 16 14
Diesel P20 P40 P60 P100
HC (ppm)
12 10 8 6 4 2 0 0
1000
2000
3000
4000
5000
6000
Load (Watt)
(c) Fig. 3 : Comparison of (a) carbon monoxide and (b) nitrogen oxide (c) unburned hydrocarbon emission with load for different value of palm oil blended fuel in engine. Conclusion When applying fuel blends with variable palm oil-diesel fractions in the direct injection diesel injector, it was found that the high viscosity palm oil had major influence to the performance and emission: Viscosity and density mentioned the RPO give a higher value from diesel fuel. Lower concentration of such P20 palm oil indicates the properties quite close to that of diesel. Engine performance testing also shows that the palm-oil blends have lower brake thermal efficiencies and higher brake specific fuel consumption promise with brake thermal efficiency close to diesel. The exhaust gas temperature for diesel also was found to be the highest when compared to neat palm oil and other blends. Moreover the CO emissions for palm oil blends were higher compared to diesel due to poor spray characteristics of blends oil caused by higher viscosity. It is recommended to use higher injection pressures, which is more than manufacturer injector setting and advance the injection timing when using the palm oil blends in diesel engine, apart from preheating the fuel. Acknowledgements The authors would like to express their appreciation to Mr. Mohd Zalmi Yop (Universiti Sains Malaysia) for providing a support for this study.
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