Performance Analysis of Petrol Engine using Producer Gas with Variable CR

Transcription

1 Performance Analysis of Petrol Engine using Producer Gas with Variable CR Bhavin C.Patel Dept. of Mechanical engineering PIET, Parul University Vadodara, India Imran Molvi Assistant Prof. Dept. of ME PIET, Parul University Vadodara, India Abstract: Producer gas is promising alternative fuel to meet energy demand in many countries which is defined as gas generation from solid waste through thermo-chemical conversion route (also termed as gasification) can be used for fuelling a compression ignition (CI) engine in duel fuel mode or a spark ignition (SI) engine in the gas alone mode. This technology is also environmentally benign and holds large promise for the future. Survey in the field of producer gas based engines reveals modest research work have been carried out since the inception of biomass/ charcoal gasification systems. Producer gas contains a large fraction of inert and with laminar burning velocity being high (due to presence of H 2 ), smooth operation at higher Compression ratio does not seem impossible. Many researchers have found that power loss could be reduce (about 15-30%)while operating producer gas at higher compression ratio. This could be attributed to two reasons, namely non- availability of standard gasification system that could generate consistent quality producer gas and the other relating to misconceptions about producer gas (related to compression ratio limitation due to knock tendency and de-rating). The knock tendency can be expected to be better on account of large fraction of inert gas as compared to natural gas. However, there has not been any research on octane rating test conducted on producer gas fuel and moreover it is not clear if any established test procedure exists for producer gas like the methane number test for natural gas and biogas. Power loss in producer gas engine could be due to reduction in the mixture energy density and the product-to- reactant mole ratio. Keywords: Producer gas, Knocking, De-rating, Gasification, Compression ratio ***** INTRODUCTION Reciprocating internal combustion engines have integrated into society service since the middle of 20ᵗ century. Their use has improved the quality of life substantially, but at the cost of degradation to the environment as well as depletion of fossil fuels, certainly due to insufficient environmental consciousness in several countries. Therefore, large impetus is being given to reduce the emissions by two approaches namely, increasing the engine efficiency and the use of alternate fuels in place of fossil fuels. In present chapter, the use of alternate fuels has been addressed along with modeling and simulation of engine combustion. In the domain of alternative fuels, gaseous fuels receive more prominence because of the possibility of cleaner combustion. Among the gaseous fuels, producer gas derived from biomass gasification is a better option as an environment friendly fuel. This fuel gas, in addition to being CO₂ neutral, generates lesser quantity of undesirable emissions. Even though the merits of producer gas have been recognized earlier, the technological capitalization has remained in infancy. The thermo-chemical conversion of biomass leads to generation of a gas generally termed as producer gas. The process is termed as gasification implies that a solid fuel is converted to a gaseous fuel. Gasification is not a new technology but is known ever since World War II. During this period a number of vehicles in Europe were powered with charcoal gasifiers (ANON-FAO Report, 1986). It is estimated that over seven million vehicles in Europe, Australia, South America and Pacific Islands were converted to run on producer gas during World War II. These engines were spark ignition (SI) engines, mostly operating in the lower compression ratio (CR) range and based either on charcoal or biomass derived gas. At the far end of 20ᵗ century, there was a renewed interest in biomass gasification technology, which had stimulated interest in producer gas operated engines. Prior to 21 st century, the work reported in this area had been limited to lower CR (less than 12.0) engine due to perceived limitation of knock at higher CR. Crude oil and petroleum products are proposed to become very costly. The fuel economy of engines is improving day-by-day and it will continue to improve in the future. On the other hand, there has been an enormous increase in the number of vehicles. This has started dictating the demand for fuel. In the near future, gasoline and diesel are expected to become more costly. Alternative fuel technology has become more popular with increased use and depletion of fossil fuels. There have been some internal combustion (IC) engines fuelled with non-gasoline or diesel oil fuels, although, their numbers have been relatively small. As the cost of petroleum products is high, many developing countries are trying to use alternate fuels for their vehicles. Another factor that has been motivating the development of alternate fuels for the IC engine is the emission problems of gasoline and diesel 617

2 engine. The large number of automobiles today is a major contributor to the air quality problem of the world. Quite a lot of improvements have been made in decreasing the emissions from the engines. But, these improvements have been nullified by the increase in the number of automobiles. Also, a large percentage of crude oil needs to be imported from other countries having large oil-fields. [1] BACKGROUND THEORY Large numbers of researches were carried out with biomass as a replacement of internal combustion (IC) engine fuel from various parts of the world. Most of these experiments were reported from USA, Europe, India, Malaysia, China and Germany. A summary of these experimental results are discussed in this paper. Literature survey in the field of producer gas based engines reveals modest research work to have been carried out since the inception of biomass / charcoal gasification systems. This could be attributed to two reasons, namely non availability of standard gasification system that could generate consistent quality producer gas and other relating to misconceptions about producer gas fuel. The history of gasification development starting from 1699 to 1970 as reported. The target and benchmarks for gasification were reported in Biomass gasification technology has been in existence for more than 80 years since world war two. The first attempt to use producer gas to operate an internal combustion engine was carried out in The first well reported conversation about using a producer gas engine for operating tractors was during Initially, diesel engines were operated along with producer gas in dual fuel mode. In dual fuel operation, 60-65% of diesel replacement was obtained while using an engine with a capacity of 5.25 kw. A dual fuel engine was operated with a power generation efficiency of 19%, with a diesel replacement of 59%. A maximum efficiency of shaft power was obtained at 21% in dual fuel operated engine. The specific fuel consumption to generate one kwh of electricity was reported as 1.28 kg of fuel wood and 65 ml of diesel. Presently most of the engines are working at a very low efficiency. Particularly the producer gas engines are working with an overall efficiency in the range of 20-22%. Efficiency closer to 20% is achieved only at the maximum operating capacity of the engine. At part load operating conditions, the efficiency of the engine is much lower. It is essential to operate the biomass gasifier based power generation system at higher efficiency to reduce fuel consumption and substitute the use of fossil fuel. Energy efficiency issues are discussed in the context of technology and trends in energy use. While encouraging technology driven economic growth there should be a focus for reduction of GHG (green-house gas) emission. Improvement in performance efficiency of engines by reducing fuel consumption helps to reduce GHG emissions substantially and achieve sustainable growth. The present study involves a detailed performance analysis of a biomass gasifier coupled with a producer gas engine for improving the overall efficiency of the system. Electrical output from the engine and energy flow through flue gas and radiator cooling fluid was monitored at variable load conditions. Initially, diesel engines were run along with producer gas on dual fuel mode to avoid complications involved in modifying an engine to run on 100% producer gas. Due to increase in cost of diesel and its scarcity in rural areas it was preferred to run engines on100% producer gas. The increasing cost of diesel price makes it too expensive to generate power on dual fuel mode. A diesel engine needs more modifications to run with 100% producer gas. The engine modifications needed are introduction of a spark ignition system, a gas carburetor (fuel intake manifold) for supplying the required fuel mixture and a governor to control the throttle valve for controlling the fuel flow according to the operating load and hence, maintain engine speed. The engine manufacturers are not in favor of engines operating with 100% producer gas due to the impurities in the gas. Now engine manufacturers like Cummins are manufacturing heavy duty IC engines having 12 cylinders which can run on 100% producer gas. PRODUCER GAS FUEL 3.1 Properties of Producer gas as fuel Some of the fundamental data relating to producer gas along with pure gases is given in Table 1. The comparison of producer gas with methane is more vital with regard to the internal combustion engine operation. This is because most of the engines operating on gaseous fuels are either close to pure methane (natural gas) or diluted methane (bio-gas, land-fill gas). The fuel-air mass equivalence ratio, i.e., (actual fuel to air ratio)/(stoichiometric fuel to air ratio) at the flammability limits compares closely for both the gases, but the laminar burning velocity for producer gas at the lean limits is much higher. The laminar burning velocity for producer gas (at 0.1MPa, 300K) is about 0.5 m/sec which is about 30% higher than methane. This feature demand lower advancement in the ignition timing for the engine based on producer gas fuel. Table 1: Comparison of properties of producer gas with other fuels Properties Producer gas Natural Petrol gas CH 4 C 8 H 18 Chemical composition CO,CO 2, H 2, CH 4, N 2 Fuel, LCV, MJ/kg Air-Fuel ratio at φ=1 (mass)

3 Energy Density of A + F mixture Laminar flame speed at stoichiometry (cm/s) Peak flame temperature (K) Product-reactant mole ratio Like any other gaseous fuel, producer gas can be used for internal combustion engine operation provided that the gas is sufficiently clean and contaminant does not accumulate in the intermediary passages to the engine cylinder. But this fuel has largely been left unexploited due to additional perceptions, namely (1) auto-ignition tendency at higher CR,(2) large derating in power due to lower calorific value. However, these perceptions were re-examined (Sridhar et al., 2001). Firstly, as the laminar burning velocity being high due to the presence of hydrogen (more so, with the gasifier system adapted) might reduce the tendency for the knock. Secondly, the presence of inert in the raw gas (CO₂ and N₂) might suppress the preflame reactions that are responsible for knocking on account of increased dilution. Also the maximum flame temperature attainable with the producer gas being lower compared to conventional fuels like methane, one could expect better knock resistivity. 3.2 The Gasification system The thermo-chemical reactions converting solid bioresidues to producer gas occur in the reactor. The IISc Bioresidue gasifier (IBG) is novel as compared to World War II design. This is an open top down draft re-burn system with air for gasification being shared from open top and side nozzles. The reactor has a removable top cover kept open during operation and screw conveyor system for ash removal. The open top operations lead to bed stratification. There will be an upward movement of the flame front into the moving bed of char with air flowing in the opposite direction. The flame front moves upwards into the un-burnt fuel. This is similar to the flame front moving in a premixed flame. Figure 1: The Gasification system This movement of the front helps in establishing a larger hot zone leading to better preparation of the fuel as it moves downwards towards the second air supply zone or the nozzle zone. Thus, in the case of an open-top gasifier, the air/gas flow is homogeneous across the bed and the air/gas also passes through a long porous bed of fuel in the vertical direction. In the open top gasifier, the regenerative heating due to the transfer of heat from the hot gases (through the wall) to the biomass moving down increases the residence time in the high-temperature zone and thus leads to better tar cracking. Combining the open-top with an air nozzle towards the bottom of the reactor helps in stabilizing the combustion zone by consuming the unconverted char left and also by preventing movement of the flame front to the top. As a consequence, the high temperature zone spreads above the air nozzle by radiation and conduction, aided by air flow from the top in the case of the open top system. The tar thus is eliminated in the best possible way by the high temperature oxidative atmosphere in the reactor itself. In the present design of the gasifier, the heat transfer from the hot gases flowing in the annular space makes it possible to gasify wood chips that have moisture contents as high as 25%, with consistent gas quality from a range of biomass fuels. A further feature of the introduction of the air nozzle into the open top design is that char conversion can be made near-complete. In steady operation, the heat from the combustion zone near the air nozzles is transferred by radiation, conduction and convection upwards causing wood chips to pyrolyse and loses 70-80% of their weight. These pyrolysed gases burn with air to form CO, CO₂, H 2, and H 2 O, thereby raises the temperature to K. The product gases from the combustion zone further undergo reduction reactions with char. The product gas exits from the reactor at around K, below the reduction zone. Typical gas composition (dry basis) at the reactor is as follows, 20 % CO, 20 % H 2, 1 % CH 4, 11 % CO₂ and the rest N 2. REVIEW OF THE PAST EXPERIMENTS Martin et al. (1981) had conducted experiments using charcoal gas and biomass based producer gas on a SI engine and had found a de-rating of 50% and 40 %respectively at a CR of 7. They also claimed 20% duration while working with producer gas at a CR of 11. An upper limit of CR of 14 and 11 for charcoal and biomass based producer gas respectively was proposed by Martinet.al. [3]. Parke et al. (1981) worked on both naturally aspirated and super charged gas engines. The de-ration of 34% was claimed compared to gasoline operation and a lesser de-rating in a supercharged mode [4]. In the Indian sub-continent, work in the area of producer gas engine has been reported by the biomass gasification group at the Indian Institute of Technology, Mumbai. Experiments were conducted on a naturally aspirated diesel engine at CR of 11.5 (Shashikant et al.1993, 1999; Parikh et al. 1995). The reason given for limiting the CR was 619

4 knocking tendency. However, no experimental evidence was lube oil quality has been periodically assessed and found to be provided in support of it [5]. satisfactory. The pressure curve is smooth and there is no The only earlier experimental work in the higher CR knock inside the cylinder [10]. range is reported by Ramachandran (1993) on a single cylinder N Homdoung and N Dussadee investigated on a small diesel engine with a CR 16.5 coupled to a water pump. A agricultural engine to study the effect of ignition timing power de-ration of 20% was reported at an overall efficiency advance of producer gas International Journal of of 19% without any signs of detonation. However this work AppliedEngineering Research, Vol. 9, No. 13 (2014) and does not report detailed measurement of gas composition, found that adjusting ignition timing can improve performance pressure crank angle diagram and emissions, which are of the producer gas engine. Appropriate ignition timing essential for systematic investigation and scientific advance enabled BMEP to increase. The maximum BMEP of understanding [6]. 195kPa was achieved at 1700 rpm of full load [11]. Experimental results of a systematic investigation on N Homdoung and N Dussadee (2015) had hands on producer gas operated internal combustion engine at higher the small, single cylinder; naturally aspirated diesel engine CR for the first time was reported by Sridhar et al. (2001). The was modified in to a spark-ignition engine. It was fueled with primary investigation was conducted on an engine of 24 kw 100% Producer gas and coupled to a 5.0 kw dynamometer. capacities. Experiments wereconducted on a spark ignition They observed the engine performance in terms of engine engine converted from a naturally aspirated, three cylinder, torque, brake power, brake thermal efficiency and brake direct injection diesel engine (RB 33 model) of compression specific fuel consumption at variable compression ratios ratio CR 17. It was reported that working at a higher CR between9.7:1-17:1. They found that the modified engine turned out to be more efficient and also yielded higher brake successfully ran with 100% producer gas at high CRs. The power. A maximum brake power of 17.5 kwe was obtained at most appropriate CR was 14:1 at full load with a maximum an overall efficiency of 21% at the highest CR. The maximum engine speed of 1700 rpm. The best BSFC of 0.94 kg/kwh and de-rating of power in gas mode was 16% as compared to the maximum BTE of about 19% were obtained [12]. normal diesel mode of operation at a comparable CR, whereas, P Gobbato, M Masi and M Benetti (2015) the overall efficiency declined by 32.5% [7]. investigated the performance and emissions of a heavy-duty Also a systematic investigation on producer gas PG-fuelled engine and compared the data found to SI engines. operation at CR comparable to that of diesel engine was They found that Power de-rating during PG operation exceeds carried out and reported by Sridhar et al. (2001, 2003, and 50% because of the reduction of thee volumetric efficiency 2006). The source of producer gas fuel used was from an open compared to NG operation. Exhaust gas analysis shows that top re-burn down draft gasifier system using casuarinas wood PG fuelling contributes to reduce both CO and NOₓ emissions pieces as fuel source. The compression ratio limits were tested in all the operating condition [13]. up to 17:1 without any audible knocking. It was demonstrated P Chunkaew, Y Sriudom, W Jainoy and W Chanpeng that the comparable power to that of diesel engine (with lesser (2016) tested the brake power of Honda Model GX-120-four de-rating of 15-20%) could be achieved with producer gas by strokes-spark ignited engine, they had studied the effect of CR operating engine at higher CR [8]. and percentage of opened air inlet valve on brake power, the In 2005, Sridhar et al. investigated on a naturally CR of 7.5:1 and 9.3:1 and percentage of opened air inlet valve aspirated engine (Ashok Leyland make ALU680model) to of 30% and 75% were used. They had found that the brake study the gaseous emissions of producer gas6 International power of CR at 9.3:1 with 75% of opened air inlet valve was Journal on Applied Bioengineering, Vol. 9, No. 1 January Watts at 3800 rpm showed the highest break power 2015driven by IC engine and found that in duel fuel operation [14]. NOₓ levels are lower compared to operations with pure diesel However, a combination of the ignition voltage, fuel on account of lower peak flame temperature. The CO compression ratio (CR) and piston crown geometry in the levels were higher due to combustion inefficiencies. In the performance and emission characteristics of a CNG engine case of gas alone operation, it is found to be environmentally with an improvement by 20-30% under certain cases with a benign in terms of emissions; NOₓ and CO levels are found to considerable reduction in emissions as compared to be much lower than most of the existing emissions norms of conventional gasoline was reported by Rajesh C. Iyer et al various countries including the USA and EU[9]. [15]. S. Dasappa et al. (2007) had hands on the CUMMINS naturally aspirated engine at Indian Institute of Science, EXPERIMENT Bangalore to check the wear of the components assessed at the Natural Gas engines are available as a product from end of 5000 hours of operation. They had observed that the engine manufacturers. This can be used for producer gas monitoring and reliability studies indicate that the wear of the operations by using a different carburetor. In establishing the engine s components to be with well within limits. Engine use of producer gas a fuel, basic research has been carried out 620

5 at IISc on converting a diesel engine to operate on producer gas. Use of producer as a fuel at varying compression ratio has been studied. The optimum ignition timing for producer gas operation at varying compression ratio was established during this study. It is evident that pressure curve is smooth and there is no knock inside the cylinder. An important aspect in fueling natural gas engines with producer gas is to handle the A/F for producer gas at varying load conditions. The carburetion system for handling producer gas was successfully developed and tested to operate on various engine capacities. Figure 2: Experimental setup The compression ratios and the mixing ratio between air and producer gas which produced from dry wood were clearly affected on torque and brake power while the engine load was being increased. Vs + Vc CR = Vc The experiments were conducted with two compression ratios. Compression ratio could be changed in two ways either modify the piston geometry or change the gasket size between cylinder head and cylinder. So we are modifying the piston geometry and increasing the compression ratio. CONCLUSION Many experimental works should be carried out using Producer gas as Internal Combustion engine fuels in various countries. In most of the experiments of Producer gas engine, they found about 40-50% of De-rating in power. Using of Producer gas as fuel can reduce the GHGs emissions almost zero. Researchers have found from past experiments that by increasing the Compression ratio in Producer gas engine reduce the Power loss of the engine about 15-30%. [4] Parke P.P. and Stanley S.J. and Walawnder W. (1981): Biomass producer Gas Fuelling of Internal Combustion Engine, Energy from Biomass and Wastes V, Lake Buena Vista PP [5] Shashikantha, Banerjee P.K., Khairnar G.S., Kamat P.P. and Parikh P.P. (1993): Development and Performance Analysis of a 15 kwe Producer Gas Operated SI Engine, Proceedings of Fourth national meet on Biomass Gasification and Combustion, Mysore, India, Vol. 4, PP [6] Ramachandran A. (1993) Performance studies on a wood gas run IC engine, Proceedings of Fourth National Meet on Biomass Gasification and Combustion, Mysore, India Vol 4,PP [7] G. Sridhar, P.J. Paul, H. S. Mukunda (2001): Biomass derived producer gas as a reciprocating engine fuel an experimental analysis, SAE Technical Paper. [8] G. Sridhar, H V Sridhar, S Dasappa, P J Paul, N K S Rajan, H S Mukunda (2005): Development of Producer gas engines, Indian Institute of Science, Bangalore, India. [9] G. Sridhar, S. Dasappa, H.V. Sridhar, P.J. Paul, N.K.SRajan (2005): Gaseous emissions using producer gas as fuel in reciprocating engines, SAE Technical Paper [10] Dasappa S, Sridhar G Rao, Sridhar H V, P J Paul (2007): Producer gas engines Proponent of clean energy technology, Indian Institute of Science, Bangalore, India. [11] N Homdoung, N Dussadee (2014): Effect of Ignition Timing Advance on Performance of a small Producer gas Engine, Chiang Mai University, Thailand. [12] N Homdoung, N Dussadee (2015): Performance Investigation of a modified small engine fueled with producer gas, Chiang Mai University, Thailand. [13] P Gobbato, M Masi, M Benetti (2015): Performance analysis of a producer gas-fuelled heavy-duty SI engine at full-load operation, University of Padova, Italy. [14] P Chunkaew, Y Sriudom, W Jainoy, W Chanpeng (2015): Modified Compression Ratio effect on Brake Power of Single Piston Gasoline Engine Utilizing Producer gas, Rajamangala University of Technology Thanyaburi, Pathumthani, Thailand. [15] Rajesh C. Iyer, MallikarjunVaggar, T.R. Seetharam, Salim Abbasbhai Channiwala (2008): Investigation of the influence of Ignition Voltage, Higher Compression Ratio and Piston Crown Geometry on the performance of Compressed Natural gas Engines, SAE REFERENCES [1] Ganesan V., Internal Combustion Engines. New Delhi, Tata McGraw-Hill, 2007 [2] G Sridhar, H V Sridhar, S Dasappa, P J Paul, D N Sunnukrishna and N K S Rajan, Green Electricity from Biomass fuelled producer gas Engine, IISc Banglore 2001 [3] Martin J. and Wauters P. Performance of Charcoal Gas Internal Combustion Engines, Proceedings of International Conference- New Energy Conversion Technologies and Their Commercialization, Vol 2, PP