National Conference on Advances in Mechanical Engineering 2011, 03 – 05 January, 2011
EXPERIMENTAL INVESTIGATION OF PERFORMANCE AND POLLUTANT EMISSIONS OF OXYGEN ENRICHED DIESEL ENGINE S. Periyasamy, Asst. Professor in Mechanical Engineering Babu.R., PG scholar in Thermal engineering Dept. of Mechanical Engineering Government College of Technology Coimbatore, Tamilnadu e-mail:
[email protected] e-mail:
[email protected] Abstract— In recent years, growing concerns about environmental preservation have created a demand for a lower pollution automotive diesel engine. Regulations covering diesel engines have also become increasingly stringent in many countries. The present work examines the effects of oxygen addition on diesel engine combustion parameters and pollutant emissions. Oxygen is enriched by adding oxygenate additive to the diesel fuel. This paper deals with oxygenate selection criterion and emission reductions in modern diesel engines. Critical fuel blending properties, which were used to screen and identify viable oxygenate additives, includes high oxygen content, diesel fuel solubility, cost, toxicity flashpoint, viscosity, water solubility in the resultant fuel blend, oxygenate extractability from the fuel and minimal impact on the natural diesel fuel cetane number. The chemical diethylene glycol dimethyl ether meets the above requirements, which is used as oxygenate of various compositions of blends. The experiment was conducted on single cylinder four stroke diesel engine. It was found that addition of oxygenated agent decrease the brake specific fuel consumption and pollutant emissions. Keywords-Oxygenated diesel fuel; Engine performance; Emission characteristics ;
I.
INTRODUCTION
Diesel engines currently find applications in most heavy load vehicles and in many stationary powergeneration units, because of their high torque output, size flexibility, durability and fuel efficiency. Thus, to facilitate widespread applications of such engines, attention has been paid to the associated environmental issues. The main pollutant emissions from diesel engines are fine particulate matter and oxides of nitrogen, unburned hydrocarbon and carbon monoxide emissions are less pronounced, but are still significant. The reduction of such pollutants from diesel engines is dictated by increasingly stringent environmental regulations all over the world. There are many different techniques for reducing emissions; some involve engine design and operational parameters, whereas others focus on engine exhaust after-treatment. Diesel engines though enjoying higher fuel economy than gasoline engines suffer from inherent higher PM and nitride oxide emissions. Currently there are many techniques that are capable of improving the combustion
Dr.T.Alwarsamy, Liaison officer Department of Technical Education Chennai, Tamilnadu email:
[email protected].
processes of diesel engines, such as the fuel injection retarding, exhaust gas recirculation, high-pressure injection and air intake supercharging. However, due to the trade-off between the Particulate matter PM and Oxides of nitrogen NOX emissions, it is very difficult to have simultaneous reductions of both the emissions. In order to meet Euro IV or the Chinese 4th Stage Emission Standards, and the future regulations, diesel vehicles usually employ two types of technical strategies: (1) Reduce Oxides of nitrogen (NOX) by Exhaust gas recirculation(EGR) and Particulate matter (PM) by diesel particulate filter and (2) Control PM by high-pressure injection and reduce NOX by selective catalytic reduction. That is to say, the meeting of the 4th Stage or higher regulations requires exhaust after treatment devices to be installed. Because the cost of diesel after treatment devices are much higher than the three-way catalyst used on gasoline vehicles, the competitiveness and applicability of future diesel vehicles have been largely hindered. The reduction of diesel engine emissions could be considered from three aspects: the combustion improvement technique, the exhaust after treatment technology and the fuel reformulation technique. However, the relevant research on fuels especially on liquid fuels was still less investigated until very recently. One promising in-cylinder technique for reducing primarily soot emissions from diesel engines is to increase the oxygen availability in the combustion chamber. This can be done by either burning oxygenated diesel fuels or by increasing the oxygen concentration of the intake air. The research on dimethyl ether as an alternative fuel produced great enlightenment. DME contains oxygen element and has no C–C bonds, which therefore helps to achieve smokeless combustion that is superior than with a diesel fuel even without high-pressure injection or turbocharger, however, the use of DME requires significant modifications on the fuel supply, delivery, and injection systems, which largely limits its application. The blending of oxygenates into a diesel fuel could effectively reduce the smoke emission from diesel engines, which has a strong synergy to the use of methanol, ethanol or dimethyl carbonate.
Department of Mechanical & Manufacturing Engineering, MIT Manipal
National Conference on Advances in Mechanical Engineering 2011, 03 – 05 January, 2011
The results indicated that the smoke emission decreased linearly as the oxygen content increased and notably near zero smoke emission was attained when the oxygen content was higher than 30%. However, the PM was not found reducing by the same extent, because the worsened ignitability of ethanol had led to a large increase in the soluble organic fraction of PM. Biodiesel is also an oxygenated fuel and contains no aromatics. Many literatures reported that biodiesel could significantly reduce the smoke and PM emissions with slightly increase in NOX. From these studies, we considered it promising to significantly reduce the PM emission from diesel engines and thus to meet more stringent emission standards via fuel formulization design, at the current engine technology level and without using an exhaust after treatment device. The present work examines the effects of oxygen addition on diesel engine combustion parameters and pollutant emissions. Oxygen is enriched by adding oxygenate additive to the diesel fuel. This project deals with oxygenate selection criterion and emission reductions in modern diesel engines. II.
III.
METHODOLOGY
A.
Oxygenate Selection Key oxygen selection criterion include: cost, toxicity, environmental impact, fuel blending properties, and engine performance. Critical fuel blending properties which were used to screen and identify viable oxygenates included: high oxygen content, diesel fuel solubility, flashpoint, viscosity, water solubility in the resultant fuel blend, oxygenate extractability from the fuel, and minimal impact on the natural diesel fuel cetane number. The Oxygenate should be soluble in diesel fuel from 1.0 to 5.0% to achieve maximum emissions reduction and improved engine performance. A number of high oxygen containing materials, such as ethylene and propylene carbonate, and most E - series glycol ethers, which are based on ethylene glycol, were eliminated from consideration due to poor diesel fuel solubility. As aromatic content in future reformulated diesel fuels is reduced from 35% to 10 - 20%, oxygenate solubility in the less polar hydrocarbon fuels will become acute. Table 1 Comparison of base fuel and various oxygenates:
LITERATURE REVIEW
T.C. Zannes [1] examined the effects of oxygen addition on diesel combustion parameters and pollutant emissions by increasing the partial pressure of oxygen in the intake air and by oxygenating the fuel resulted that fuel side fuel side oxygenation gave higher soot reductions then air side oxygen enrichment. Dr R Anand [2] studied that by varying oxygen enrichment in the inlet air increases the brake thermal efficiency and subsequently decreases the brake specific fuel consumption. It was also found that an oxide of nitrogen (NOX) increases whereas smoke intensity decreased from the normal level. Md. Nurun Nabi [3] studied the effects of performance parameters, emission and combustion related parameters for different oxygenated fuels and the results showed that almost all the combustion related parameters are closely related to oxygen content of the fuels. Jianxin Wang and Fujia Wu [4] are designed various oxygenated blends and its effects on engine performance and emissions and resulted that the oxygenated blends not only be high oxygen content, but also high cetane number, low sulphur and low aromatic contents. Bruce A. Buchholz [5] studied the effects of various oxygenates on diesel engine particulate matter and the experimental results shows PM reduction is controlled by the oxygen content of the fuel. Huang et al [6] investigated the combustion and emission characteristics in a compression-ignition engine with DME and found that the DME engine has high thermal efficiency, short premixed combustion, fast diffusion combustion duration, and their work was to realize lownoise, smoke-free combustion.
Oxygenates
Abbreviation
Molecular formula
Oxygen content (Wt %)
Penta decane
PD
C15H32
0.0
Di-n-butyl ether
DBE
C8H18O
12.3
Methyl-t-butyl ether
MTBE
C5H12O
18.2
Methyl ethyl ketone
MEK
C4H8O
22.2
Diethylene glycol dimethyl ether
DGM
C6H14O3
35.8
Dimethoxy methane
DMM
C3H8O2
42.1
Methanol
MEOH
CH3OH
50.0
Dimethyl carbonate
DMC
C3H6O3
53.3
The Oxygenated diesel fuel flashpoint needs to be over 52˚C, as specified by ASTM D975 to reduce the transportation flammability risk. Many inexpensive types of ether with high oxygen content, including MTBE and ETBE were eliminated from consideration due to the low flashpoints of the resulting 1.0% oxygenated fuel blends. Fuel blends containing 1 % or more of inexpensive dimethyl carbonate and diethyl carbonate were also eliminated because the resulting blends had flashpoints
Department of Mechanical & Manufacturing Engineering, MIT Manipal
National Conference on Advances in Mechanical Engineering 2011, 03 – 05 January, 2011
lower than the target. A key issue is how the additive behaves if the oxygenated blend becomes exposed to water. Both high degree of water solubility in the fuel blend and high degree of water extractability of the oxygenated additive from the fuel are unacceptable. Dimethyl and diethyl carbonate both have high water extractability from the fuel. Similarly, most fuel soluble E - series glycol ethers are easily extracted and are thus eliminated from consideration. P - Series glycol ethers, generally, have acceptable partitioning characteristics. Many intermediate molecular weight aliphatic, cycloaliphatic and aryl alkyl alcohols meet the fuel blending selection criteria. Poly (ether) polyols based on propylene oxide or butylene oxide are viable oxygenate candidates. Methyl soyate which is a form of biodiesel meets selection criterion and was evaluated. Several commercial p- series glycol ethers and new glycol ether oxygenate di-butyl glycerol are potentially inexpensive and meet the other entire selection criterion. Diglyme which is associated with health risks and too expensive to be economically viable was included in the test program so that benchmark comparisons can be made with previous studies. Various emission reduction strategies which utilize oxygenated diesel fuel are outlined in this work the comparison of base fuel and diglyme as shown in table 2. TABLE 2: COMPARISON OF BASE FUEL AND DIGLYME Properties
Diesel
Diglyme
Chemical formula
C H
CH O
Mole weight (g)
0.86
0.94
42.5
24.5
260
322
Cetane number
45
126
Boiling point (°C)
180-330
161.3
C (wt %)
86
53.7
H (wt %)
14
10.5
O (wt %)
0
35.8
Lower heating value(MJ/kg) Heat of evaporation (kJ/kg)
IV.
12
26
6
14
3
KIRLOSKAR COMPUTERISED IC ENGINE SPECIFICATIONS
Type: Engine speed: Rated power: Bore: Stroke length: Fuel type: Cooling: Loading:
Single cylinder four stroke vertical Engine 1500 RPM 3.5 kW 80 mm 110 mm High speed diesel Water cooled Eddy current dynamometer
FIGURE 1: Schematic Diagram of Experimental Setup
Starting : Manual cranking Type of ignition: Compression ignition Arm length: 0.185 m Orifice diameter: 0.02 The experiment was conducted on single cylinder four stroke diesel and the specifications given above. The schematic diagram of experimental setup is shown in figure1. The experiment was conducted for two proportions (10% and 20%) of blend and base fuel (diesel) and then performance and emissions observations were tabulated. V.
RESULTS AND DISCUSSIONS
Based on the experimental data the graphs were drawn. These graphs shows the variation in brake thermal efficiency, specific fuel consumption, NOX, mechanical efficiency and air fuel ratio with respect to brake power. The variation of brake thermal efficiency at various loads of the base engine is compared with different oxygenates blends as shown in figure 3. There is an improvement in the brake thermal efficiency at all loads when 10% of blend is used. This improvement is due to better combustion of fuel. However, brake thermal efficiency falls as the oxygenate blend is increased to 20%.The variation of specific fuel consumption at various loads of the base fuel engine is compared with various oxygenate blends as shown in figure 2.There is a fall in the SFC at all loads when 10% blend is used. This decrease is due to higher combustion efficiency of the fuel. The variation of mechanical efficiency at various loads of base fuel engine is compared with various oxygenate blends as shown in figure 4. There is a slight increase in mechanical efficiency for 10% of blend, but later it is unaltered. The variation of air fuel ratio at various loads of the base fuel engine is compared with various oxygenate blends as shown in figure 5.There is an increase in the A/F ratio at all loads when 10% blend is used. This improvement is due to complete combustion of fuel. Based on the emission readings the graphs were drawn for various pollutant emissions with respect to loads. The variation of NO at various loads of the base fuel engine
Department of Mechanical & Manufacturing Engineering, MIT Manipal
National Conference on Advances in Mechanical Engineering 2011, 03 – 05 January, 2011
is compared with various oxygenate blends as shown in figure 6. The result shows that there is slight increase in the NO for all the blends. The variation of CO at various loads of the base fuel engine is compared with various oxygenate blends as shown in figure 7. The result shows that there is decrease in the CO for all the blends. This improvement is due to oxygen content present in the blended fuel. The variation of NOX at various loads of the base fuel engine is compared with various oxygenate blends as shown in figure 8. The result shows that there is slight increase in the NOX due to increase in adiabatic flame temperature of the combustion which influences oxidation of nitrogen to form NOX. The variation of CO2 at various loads of the base fuel engine is compared with various oxygenate blends as shown in figure 9. The result shows that there is slight increase in the CO2 for all the blends because CO is converted into CO2.
side could lead to significant improvement in performance parameters and reduction in pollutant emissions of a diesel engine. However, it has an adverse effect on NOX emissions. Thus, it has to be combined with other methods of controlling NOX emissions if overall improvement is desired. Methods such as, exhaust gas recirculation, injection of water or three phase emulsion and after cooling following turbo charging may be tried.
V. CONCLUSION An experimental study was conducted, to scrutinize the effect of oxygen enrichment on DI diesel engine performance characteristics and pollutant emissions. The following conclusions are summed up, from the examination of the experimental findings and computational results: It is concluded that oxygen enrichment in the fuel
[4]
Figure 2 LOAD Vs BSFC
REFERENCES [1]
[2]
[3]
[5]
[6]
T C Zannis,E G Pariotis “Theoretical study of DI diesel engine performance and pollutant emissions using comparable air side and fuel side oxygen addition” Energy conservation and management 48(2007). Dr R Anand,Dr N V Mahalakshmi “The effects of oxygen enrichment with intake air in a direct injection diesel engine” Nov 2006 IE(I) journal-MC. Md.Nurun Nabi “Theoretical investigation of engine thermal efficiency, adiabatic flame temperature, NO x emission and combustion-related parameters for different oxygenated fuels.”Applied Thermal Engineering 30(2010) 839-844. Jianxin wang,Fujia Wu “Oxygenated blend design and its effects on reducing diesel particulate emissions” Fuel 88 (2009)2037-2045. Bruce A. Buchholz, A.S.Cheng and Robert W.dibble “The Effect of oxygenates on diesel Engine Particulate Matter,” SAE Technical Paper 2002-01-1705. Huang, Z. H, Wang, H. W, Chen, H. Y. Study on combustion characteristics of a compression ignition engine fueled with dimethyl ether.
Figure 3 LOAD Vs BRAKE THERMAL EFFICIENCY
Figure 4 LOAD Vs MECHANICAL EFFICIENCY
Department of Mechanical & Manufacturing Engineering, MIT Manipal
Figure 5 LOAD Vs A/F RATIO
National Conference on Advances in Mechanical Engineering 2011, 03 – 05 January, 2011
Figure 6 LOAD Vs NO
Figure 7 LOAD Vs CO
Figure 8 LOAD Vs NOX
Figure 9 LOAD Vs CO2
Department of Mechanical & Manufacturing Engineering, MIT Manipal
