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Lakshmanan

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Published in: Mechanical
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Acetylene gas in ic engines.

Praveen J / Chennai

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  1. SOSA' s ELSEVIER Transportation Research Part D 54 (2017) 372—380 Contents lists available at ScienceDirect Transportation Research Part D journal homepage: www.elsevier.com/locate/trd TRANSPORTATION RESEARCH CrossMark Experimental study on DI diesel engine with acetylene in dual fuel mode with DEE as an ignition enhancer T. Lakshmanan a'* , A. Avinash b, G. Nagarajan c Department of Mechanical Engineering, S.A Engineering College, Chennai 600077, India b Department of Mechanical Engineering, KPR Institute of Engineering and Technology, Coimbatore 641407, India c Internal Combustion Engineering Division, College of Engineering, Anna University, Chennai 600025, India ARTICLE Keywords: Dual-fuel Port injection Dilution effect Ignition Pre-ignition Backfire 1. Introduction INFO ABSTRACT Fossils fuels are currently the dominant global source for air pollution and their combus- tion is posing a serious threat to clean environment. The economic cost of the effect of this pollution has been estimated at 0.4% of GDP for a developing country. The limits for reduc- tion in the emissions levels have been agreed by various nations in concordance with the Kyoto protocol. As far as low emission fuels are concerned, gaseous fuels appear to be cap- able of performing a prominent role in reducing emissions. Various gaseous fuels such as biogas, producer gas, hydrogen, acetylene, LPG and CNG are suitable for IC engines. In the present research, a genuine effort is made to establish that acetylene can be taken as a substitute fuel for diesel in dual fuel mode. A 4.4 kW single cylinder, air-cooled diesel engine has been taken up for the present study. As the gaseous fuel suffers poor combus- tion in diesel engines, especially at part loads, DEE which is considered as a most renew- able fuel was injected into the port as a combustion enhancer at the rate of 100 g/h, 150 g/h and 200 g/h adopting carburetion technique at the maximum gas flow rate of 390 g/h of acetylene gas. Finally, the experiment yielded the maximum diesel energy sub- stitution of 49% along with DEE. In this study, the performance, combustion and emission characteristics of acetylene DEE have been analysed. 0 2017 Elsevier Ltd. All rights reserved. The problems of dwindling reserves of easily accessible non-renewable petroleum fuels coupled with the hazards of envi- ronmental pollution caused by their combustion necessitates to search for an alternative clean burning fuel. Promising alter- nate fuels for internal combustion engines are natural gas, liquefied petroleum gas, hydrogen, acetylene, producer gas, alcohols and vegetable oils. The engine researchers in particular are keen on developing and introducing alternative gaseous fuels to replace either partially or totally the conventional fuel. The gaseous fuels have a high self-ignition temperature and hence they are suitable for spark ignition (SI) engines. For this substantial reason they cannot be used directly in compres- sion ignited (CI) engines. On the other hand, CI engines however can be made to use a considerable amount of gaseous fuels in dual fuel mode without incorporating any major changes in the engine construction. In dual fuel engines, usually gaseous fuels are mixed with air either in the intake manifold or through direct injection into the cylinder. The resulting mixture, * Corresponding author. E-mail address: [email protected] (T. Lakshmanan). http ://dx.doi.org/10.1016/j .trd.2017.06.012 1361-9209/0 2017 Elsevier Ltd. All rights reserved.
  2. T. Lakshmanan et al./ Transportation Research Part D 54 (2017) 372—380 373 after compression is then ignited through direct injection of small amount of diesel fuel. Thus, gas diesel engine combines the features of both SI and CI engine (Karim et al., 1983). 1.1. Acetylene as an alternative fuel Among gaseous fuels which possess excellent combustion properties are LPG, natural gas, hydrogen and acetylene. Gas- eous fuels such as LPG and natural gas have been commercialized and more research work has been carried out to use hydro- gen in internal combustion engines. Research work has not been much carried out using acetylene as an alternative fuel in diesel engines. Acetylene is a colourless gas with garlic smell produced from hydrolysis of calcium carbide (CaC2), commer- cially used for generating acetylene for welding purpose. Its chemical formula is C2H2. Acetylene has a very wide flamma- bility range (2-80% by volume); as a result, engine can run with a very lean mixture. It has higher flame speed (1.5 m/s) and hence faster energy release rate when compared to diesel fuel (I
  3. 374 T. Lakshmanan et al./ Transportation Research Part D 54 (2017) 372—380 HCCI mode is comparable with that of the diesel engine. Nitric oxide and smoke emissions got reduced drastically. Hydro- carbon emissions are comparatively lower at lower loads and higher at higher load conditions. Carbon monoxide emissions are comparable with that of the conventional CI mode. 2.1. Objectives of the present research work The objectives of the present research work is to study the performance, emission and combustion characteristics of acet- ylene at 390 g/h of flow rate in a diesel engine by adopting the carburetion technique with timed port injection of DEE as an ignition improver. 3. Experimental set-up and procedure A single cylinder, 4-stroke, air-cooled, naturally aspirated direct injection diesel engine with a compression ratio of 17.5:1 developing 4.4 kW at 1500 rpm was used for the present research work. A three hole nozzle was used with an opening pres- sure of 200 bar injecting fuel at 230 bTDC. (Before top dead center). The schematic of the experimental setup is shown in Fig. 1. The in-cylinder pressure was measured with a water-cooled piezoelectric transducer. The engine was modified to operate in the dual fuel mode by fitting a gas carburetor in the intake manifold. The engine was coupled to an electrical dynamometer for loading. The temperature of the exhaust gas was measured with Chromel Alumel (1
  4. T. Lakshmanan et al./ Transportation Research Part D 54 (2017) 372—380 375 l. 2. 3. 4. 5. 1 2 t 3 Switch ECU Battery Water pump Water tank 7 6 t 4 5 7 6 6. 7. 8. 9. 7 8 6 9 Pressure regulator Pressure gauge Inlet port Water injector Fig. 2. Acetylene-DEE injection system. injector. The DEE injector, which is normally used to inject gasoline, was mounted at intake port 5 mm above the inlet valve seat. The ECU controlled the injector to inject the exact quantity of DEE during the suction stroke (TPI timed polt injection). The equipment was calibrated outside before fitting it into the system. Tests were conducted in dual fuel mode with port injection of DEE in carburetion technique with fixed acetylene flow rate of 390 g/h (Lakshmanan and Nagarajan, 2010). The injected DEE quantity was 100 g/h, 150 g/h and 200 g/h. 3.2. Experimental procedure Initially experiments were conducted for various loads at constant speed in diesel engine with maximum knock limited flow rate of 390 g/h acetylene in dual fuel mode. To improve the combustion characteristics of acetylene- diesel mixture; DEE was injected into the port at 100 g/h, 150 g/h and 200 g/h during the suction stroke in carburetion technique at the max- imum gas flow rate of 390 g/h for various loads at constant speed. 4. Experimental error analysis Three runs of tests were performed under identical conditions to check for the repeatability of all the results. The average of the three measured values is taken as a reading for the basic quantities. The repeatability of the results was found to be within 3% based on Gaussian distribution. An error analysis for the derived quantities, such as brake power and thermal Table 2 Accuracy of the instruments used and uncertainty of the measured value. Sl. No 1 2 3 4 5 6 7 8 9 10 11 12 13 Measured values Air flow Diesel flow Time Speed Voltage Current Crank angle In-cylinder pressure Smoke Unburned HC Carbon monoxide Carbon dioxide Oxides of nitrogen Instruments Orifice Burette Digital stop watch Tachometer Vol tmeter Ammeter Crank angle encoder Pressure pickup Bosch smoke meter Exhaust gas analyser Exhaust gas analyser Exhaust gas analyser Exhaust gas analyser Accuracy ±1 mm ±1 mm rpm ±O.16A OCA ±0.2 bar ±0.2 BSN ±1 ppm ±0.01 vol% ±0.1 vol% ±1 ppm Uncertainty (%) ± 1.3 ± 1.3
  5. 376 efficiency was performed, based on the method suggested by Holman (1973). The uncertainty in the measured values and calculated values are given in Table 2. 5. Result and discussion The performance, combustion and emission characteristics are discussed in this section for the experiments conducted at various loads with different DEE flow rates. The pressure crank angle and heat release rate for 100 g/h and 150 g/h showed a similar trend to that of 200 g/h of DEE injection. Hence, pressure crank angle and heat release rate are discussed only for 200 g/h of DEE injection. 5.1. Pressure crank angle The variation of cylinder pressure with crank angle is shown in Fig. 3. The peak pressure obtained in acetylene diesel dual fuel mode is the highest compared to diesel fuel. This is because of acetylene combustion exhibits a higher ignition delay in dual fuel mode which is the significance characteristics of dual fuel engines when compared to diesel combustion (Karim et al., 1983). Acetylene with DEE as ignition source results in a lower cylinder pressure than acetylene diesel dual fuel mode. The reduction in peak pressure is due to DEE as lower chemical delay and slight cooling of the intake charge, which results in a reduction in combustion chamber peak pressure. 5.2. Heat release rate The analysis for the heat release rate is based on the application of thermodynamics first law for a closed system using Eq. 50 40 30 T. Lakshmanan et al./ Transportation Research Part D 54 (2017) 372—380 (1) dQht 1 dp do 7-1 do 7-1 do (1) where 0 is the crank angle in degrees, y is the ratio of specific heat of the fuel and air. The primary source data for the above equation is taken from the average pressure crank angle cycle as measured by the pressure transducer. Fig. 4 shows the vari- ation of heat release rate with crank angle at full load. It is noticed that the heat release rate for acetylene diesel operation is advanced and diffusion combustion is suppressed than the diesel fuel. This may be attributed to high diffusion rate of acet- ylene and faster energy release due to increased flame propagation velocity once the ignition set in at various locations. The acetylene with DEE mode results in slight advancement in heat release rate than the acetylene-diesel dual fuel mode. This may be attributed to DEE is a highly volatile fuel which forms the homogenous mixture leading to lower chemical delay. 5.3. Cylinder peak pressure The cylinder pressure variation is shown in Fig. 5. The maximum cylinder pressure obtained in acetylene diesel dual fuel mode is higher than that of diesel fuel. The peak pressure rise in carburetion technique corresponds to instantaneous and large amount of fuel burnt in pre-mixed combustion stage compared to diesel fuel. The peak pressure in the case of acetylene with DEE is reduced than that of acetylene without DEE dual fuel operation. The reduction in peak pressure is due to the use of DEE which has higher latent heat of evaporation and lower chemical delay period. The percentage gas substitution is higher at part load though the gas flow rate and DEE injection rate is fixed; only diesel quantity is varied by the governor to maintain the constant speed. At higher loads, the percentage diesel replacement decreases as the quantity of diesel 100 90 80 70 60 20 10 340 Fig. 3. Il Diesel Acetylene 390 g/h — Acetylene 390 g/h + DEE 200 g/h 350 360 370 380 crank angle (deg) 390 400 Variation of Pressure with crank-angle at full load.
  6. T. Lakshmanan et al./ Transportation Research Part D 54 (2017) 372—380 377 2 90 80 70 60 50 40 30 20 10 -10 350 Diesel - Acetylene 390 g/h Acetylene 390 g/h + DEE 200 g/h 360 370 Crank angle (deg) 380 390 Fig. 4. Variation of Heat release rate with crank-angle at full load. injected is higher. The maximum diesel substitution achieved at 200 g/h of DEE along with acetylene in carburetion tech- nique is 49% at full load. As DEE also takes part in combustion along with acetylene, energy substitution is higher than acet- ylene diesel dual fuel mode. 5.4. Brake thermal efficiency shows the variation of brake thermal efficiency with load for the engine operating on diesel, acetylene 390 g/h and Fig. 6 acetylene-DEE (acetylene with DEE 100 g/h, acetylene with DEE 150 g/h and acetylene with DEE 200 g/h) fuels. The maxi- mum brake thermal efficiency obtained with diesel at full load is 28%. The brake thermal efficiency is lower throughout acet- ylene diesel dual fuel mode operation compared with neat diesel operation. This is due to gaseous combustion exhibiting a higher combustion velocity compared to hydrocarbon combustion leading to higher heat loss through combustion chamber wall which in-turn lowers brake thermal efficiency (Shudo et al., 2000). The brake thermal efficiency of acetylene with DEE injection (200 g/h) is 28%. It is observed that by injecting DEE along with the air in the suction stroke slightly increases the brake thermal efficiency of acetylene operation with respect to acetylene-diesel operation. This may be due the reason that when DEE is injected, it evaporates quickly, mixes easily with air, forms a homogeneous mixture, and results in combustion creating a hotter environment in burning the acetylene charge mixture completely. 5.5. Exhaust gas temperature The variation of exhaust gas temperature with load for different modes of operation is shown in Fig. 7. The exhaust gas temperature for acetylene-diesel dual fuel mode is 300 oc at full load. Acetylene-diesel dual fuel mode shows lower exhaust gas temperature than diesel. The reason is due to the advancement of energy release in the cycle and higher flame speed (Haragopala et al., 1983). The exhaust temperature is reduced to 254 oc at 200 g/h flow rate of DEE with acetylene at full load. This may be attributed to the reduction in the inlet charge temperature due to the presence of DEE. The combined effect of acetylene and DEE in the reduction of exhaust gas temperature leads to increase in life expectancy of the engine compo- nents thereby increasing the durability of the engine. 5.6. Oxides of nitrogen emission The emission of oxides of nitrogen is significantly influenced by the cylinder gas temperature and availability of oxygen during combustion. Fig. 8 shows the variation of NOX emissions with load in acetylene-diesel dual fuel mode operation. NOX 100 90 80 70 60 50 40 30 20 10 Fig. 5. Diesel —EAcety1ene+DEE 100 Acetylene+DEE 150 g/h —+-Ace lene+DEE200 h 20 40 60 80 100 Load % Variation of cylinder peak pressure with load.
  7. 378 T. Lakshmanan et al./ Transportation Research Part D 54 (2017) 372—380 35 30 25 20 15 10 5 Di el Acetylene+DEE 200 g/h Acetylene 390 g/h 20 40 60 80 100 Load (0/0) Fig. 6. Variation of Brake thermal efficiency with load. is 16.93 g/l
  8. T. Lakshmanan et al. / Transportation Research Part D 54 (2017) 372—380 379 25 20 15 10 5 Diesel —e— Acetylene+DEE 100 —x— Acetylene+DEE 150 g/h Acetylene+DEE 200 g/h Acetylene 390 g/h 20 40 60 Load (%) 80 5 4 3 1 0 0.25 0.20 0.15 0.10 0.05 0.00 20 12 10 8 6 4 2 O 20 Fig. 8. Variation of NOX with load. Diesel Acetylene+DEE 100 g/h Acetylene+DEE 150 Wh -+— Acetylene+DEE 200 —a— Acetylene 390 g/h 20 40 60 80 100 100 Fig. 9. Variation of Smoke with load. Diesel -+- Acetylene+DEE 100 g/h Acetylene+DEE 150 g/h Acetylene+DEE 200 g/h —E— Acetylene 390 Y/h 40 Fig. 10. 40 Fig. 11. 60 80 100 Load (0/0) Variation of HC with load. Diesel Acetylene+DEE 100 g/h -x- Acetylene+DEE 150 —+— Acetylene+DEE 200 g'h —a— Acetylene 390 o 60 80 100 Load (0/0) Variation of CO with load.
  9. 380 T. Lakshmanan et al./ Transportation Research Part D 54 (2017) 372—380 neat diesel operation. CO emission decreases with increase in DEE flow rate. DEE contains 21.6% of oxygen by mass; this leads to complete combustion and lowering CO emission level. Thus, oxygen-contained fuel has a significant effect in reduc- ing CO levels. 6. Conclusions The conclusions drawn from the work are as follows: The brake thermal is 28% with 200 g/h of DEE. The brake thermal efficiency of acetylene-diesel dual fuel operation is 27% with 390 g/h of gas flow rate at the rated output, which is lower than diesel efficiency of 29%. Injection of DEE with acetylene marginally increases the brake thermal efficiency when compared to acetylene without DEE. Dual fuel mode shows a lower exhaust gas temperature than diesel. NOX levels are higher for acetylene dual fuel operation with 390 g/h of gas flow rate due to increase in the combustion rate. The maximum NOX emission is 16.93 g/l

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