Chapter 5 Conclusions and Recommendations
5.1 Conclusions
The study is continuous efforts of Lin’s[4] and Huang’s[5] works, which carries out with three major modifications. They are including the measurements of the detailed intake biogas constitutes and their concentrations, dehumidification of the water vapor in intake biogas and installation of the complete ignition system, consisting spark plug pressure sensor, and rotary encoder to record the crank angle of piston cylinder. This study divided into two parts. Firstly, the effect of water vapor of intake biogas with different excess air ratio on generator performance was invastigated. Secondly, the optimum spark timing of the present generator was found. Besides, the advanced and postponed spark timing from the optimum one were analyzed as well. The in-cylinder pressure was also measured.
According to the above experiment results, this study can obtain the following conclusions:
1. The detailed intake biogas constitutes and their concentrations are listed in Tables4.1 and 4.3. It is found that the biogas contains the air, hence it has to take into consideration while derives the stoichiometric air-fuel ratio.
2. At a given biogas supply rate, the biogas with dehumidification provides the higher power generation and thermal efficiency than the biogas without dehumidification. The power outputs increasing rate of biogas supply rate at 200, 220 and 240L/min with stoichiometric
56
condition are up to 4.7%, 5.9% and 2.7%, and the dehumidified biogas offers enthalpy increasing rate up to 0.79%, 1.17% and 1.27% than the biogas without dehumidification.
3. The optimum spark timing of present engine is located at BTDC13, where supplies larger power output than other spark timings. At a given biogas supply rate and excess air ratio, the power generation, thermal efficiency and percentage of used CH4 by operating at the spark timing of BTDC13 are the highest. The spark timing of BTDC9, the delayed one, leads to higher exhaust gas temperature and reduces the NOx emission at a given biogas supply rate.
4. At a given biogas supply rate, the spark timing of BTDC13 has a lowest CoVIMEP, and the BTDC17 has a largest CoVIMEP. There is an opposite trend between CoVIMEP and CH4 consumption ratio which indicate that the lower CoVIMEP makes the higher CH4 consumption ratio.
5.2 Recommendations
Based on this study, the recommendations to solve the problem of the limit excess air ratio at high biogas supply rate and the future works are suggested:
1. Redesign the engine to increase the volume limit of gas into the engine.
2. Build an automatic water gate at anaerobic fermentation pool to avoid the air that leak to the storage tank to obtain purer biogas.
3. Add H2 in the biogas to reduce the CoVIMEP and enhance the CH4
57
consumption ratio.
4. Consider to use the gas turbine engine to compare with the internal combustion engine.
58
References
[1] A. Brown, “2010 Survey of Energy Resources”, World Energy Council, 360-361, 2010.
[2] Falin Chen, Shyi-Min Lu , Eric Wang, Kuo-Tung Tseng,
“Renewable energy in Taiwan”, Renewable and Sustainable Energy Reviews, 14 ,2029-2038,2010.
[3] Wen-Tien Tsai, Che-I Lin, “Overview analysis of bioenergy from livestock manure management in Taiwan”, Renewable and Sustainable Energy Reviews, 13, pp. 2682-2688, 2009.
[4] Wei-Tsung Lin, “A Research for Electricity Generation by Using Biogas from Swine Manure for a Farm Power Requirement”, June 2010.
[5] Sheng-Rung Huang, “The Experimental Study on Biogas Power Generation Enhanced by Using Waste Heat to Preheat Inlet Gases ”, June 2011.
[6] Jung-Jeng Su, Bee-Yang Liu, Yuan-Chie Chang, “Emission of greenhouse gas from livestock waste and wastewater treatment in Taiwan”, Agriculture Ecosystems and Environment, 95, pp.
253-263, 2003.
[7] Shang-Shyng Yang, Chung-Ming Liu, Yen-Lan Liu, “Estimation of methane and nitrous oxide emission from animal production sector in Taiwan during 1990–2000”, Chemosphere, 52, pp.
1381-1388, 2003.
[8] E. Porpatham, A. Ramesh, B. Nagalingam, “Investigation on the effect of concentration of methane in biogas when used as a fuel
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for a spark ignition engine”, Fuel, 87, pp.1651–1659, 2008.
[9] Anil Singh Bika, Luke Franklin, David B. Kittelson, “Engine knock and combustion characteristics of a spark ignition engine operating with varying hydrogen and carbon monoxide proportions”, Hydrogen Energy, 36, pp.5143-5152, 2011.
[10] Aparna Arunachalam, Daniel B. Olsen, “Experimental evaluation of knock characteristics o producer gas”, Biomass and Bioenergy, 37, pp.169-176, 2012
[11] Deepak Agarwal, Shrawan Kumar Singh, Avinash Kumar Agarwal,
“Effect of exhaust gas recirculation (EGR) on performance, emissions, deposits and durability of a constant speed compression ignition engine”, Applied Energy, 88, pp.2900-2907, 2011.
[12] Erjiang Hu, Zuohua Huang, Bing Liu, Jianjun Zheng, Xiaolei Gu,
“Experimental study on combustion characteristics of a spark-ignition engine fueled with natural gas-hydrogen blends combining with EGR”, Hydrogen Energy, 34, pp. 1035-1044, 2009.
[13] S. Swami Nathan, J.M. Mallikarjuna, A. Ramesh, “Effects of charge temperature and exhaust gas re-circulation on combustion and emission characteristics of an acetylene fuelled HCCI engine”, 89, pp.515-521, 2010.
[14] S. Szwaja, K.R. Bhandary, J.D. Naber, “Comparisons of hydrogen and gasoline combustion knock in a spark ignition engine”, Hydrogen Energy, 32, pp.5076-5087, 2007.
[15] Cheolwoong Park, Seunghyun Park, Yonggyu Lee, Changgi Kim,
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Sunyoup Lee, Yasuo Moriyoshi, “Performance and emission characteristics of a SI engine fueled by low calorific biogas blended with hydrogen” , Hydrogen Energy, 36, pp.10080-10088, 2011.
[16] O. Badr, N. Alsayed and M. Manaf, “A parametric study on the lean misfiring and knocking limits of gas-fueled spark ignition engines”,18,pp.579-594,1998.
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Figure 1.1 Simple Carbon Cycle for Biogas [4]
Figure 1.2 Scope of this Research
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Figure 2.1 Process of Biogas Production
Figure 2.2 Range of Capacities for the Power Generators
63 Feature Four-stroke
engine
Gas-Diesel engine
Stirling
engine Fuel cell Gas turbine Micro gas turbine
Capacity(kW) <100 >150 <150 1-10000 20MW 28-200
Electrical
efficiency 30-40% 35-40% 30-40% 40-70% 25-35% 15-25%
Pressure ratio 10:1 20:1 5:1 n.a. 5:1 5:1
Lifetime Medium Medium Long Very short Long Long
Alternative fuel in case of shortage
of biogas
Liquid gas
(gasoline) Liquid gas Any Natural gas Natural gas Natural gas, Fuel oil
Figure 2.3 Values of Power Generators
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Figure 3.1 Experimental Equipment Layout
Figure 3.2 Four Stroke Diesel Engine
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Figure 3.3a VA-400 Flow Sensor
Figure 3.3b VA-400 Flow Sensor Data
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Figure 3.4a TF-4000 Flow Meter
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Figure 3.4b TF-4000 Flow Meter Data
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Figure 3.5 Dehumidifier (RD15)
Figure 3.6 JHTD3010-N Temperature with Humidity Transmitter
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Figure 3.7 ECA450 Gas Analyzer
Figure 3.8 Guardian Plus Infra-Red Gas Monitor
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Figure 3.9a CompactDAQ Chassis
Figure 3.9b NI 9203 Analog Input Module
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Figure 3.9c NI 9211 Analog Input Module
Figure 3.9d NI 9401 Digital Input Module
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Figure 3.10 Ignition System Layout
Figure 3.11 Spark Timing Controller
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Figure 3.12 VERICOM 4000DAQ Tachometer
Figure 3.13 Spark Plug Pressure Sensor (BKR5E-11 and 112A05)
74
Figure 3.14 Charge Converter (PCB 422E05)
Figure 3.15 HPN-6A Rotary Encoder
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Figure 4.1 Power generation v.s. excess air ratio with and without dehumidification
Figure 4.2 Waste gas temperature v.s. excess air ratio with and without dehumidification
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Figure 4.3a Thermal, fuel conversion and combustion efficiency v.s.
excess air ratio with 240L/min biogas supply and with and without dehumidification
Figure 4.3b Thermal, fuel conversion and combustion efficiency v.s.
excess air ratio with 220L/min biogas supply and with and without dehumidification
77 Figure 4.3c Thermal, fuel conversion and combustion efficiency v.s.
excess air ratio with 200L/min biogas supply and with and without dehumidification
Figure 4.4 O2 concentration in waste gas v.s. excess air ratio with and without dehumidification
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Figure 4.5 NOx concentration in waste gas v.s. excess air ratio with and without dehumidification
Figure 4.6 CO2 concentration in waste gas v.s. excess air ratio with and without dehumidification
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Figure 4.7a Power generation v.s. excess air ratio with 260L/min biogas supply and different spark timings
0.80 0.85 0.90 0.95 1.00 1.05 1.10
4
Figure 4.7b Power generation v.s. excess air ratio with 240L/min biogas supply and different spark timings
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Figure 4.7c Power generation v.s. excess air ratio with 220L/min biogas supply and different spark timings
0.80 0.85 0.90 0.95
Figure 4.8a Thermal efficiency v.s. excess air ratio with 260L/min.
biogas supply and different spark timings
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Figure 4.8b Thermal efficiency v.s. excess air ratio with 240L/min.
biogas supply and different spark timings
0.8 0.9 1.0 1.1 1.2 1.3
Figure 4.8c Thermal efficiency v.s. excess air ratio with 220L/min.
biogas supply and different spark timings
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Figure 4.9 Waste gas temperature v.s. excess air ratio with different biogas supply and different spark timings
0.8 0.9 1.0 1.1 1.2 1.3
Figure 4.10 O2 concentration in waste gas v.s. excess air ratio with different biogas supply and different spark timings
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Figure 4.11 NOx concentration in waste gas v.s. excess air ratio with different biogas supply and different spark timings
0.8 0.9 1.0 1.1 1.2 1.3
Figure 4.12 CO2 concentration in waste gas v.s. excess air ratio with different biogas supply and different spark timings
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Figure 4.13a Estimated CH4 consumption ratios v.s. excess air ratio with 260L/min biogas supply and different spark timings
0.8 0.9 1.0 1.1
Figure 4.13b Estimated CH4 consumption ratios v.s. excess air ratio with 240L/min biogas supply and different spark timings
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Figure 4.13c Estimated CH4 consumption ratios v.s. excess air ratio with 220L/min biogas supply and different spark timings
-100 0 100 200 300 400 500 600 700 800
Figure 4.14 In-cylinder pressure v.s. crank angle degree with 240L/min biogas supply rate and λ=1.0 at different spark timings
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Figure 4.15 IMEP v.s. 200 combustion cycles with 240L/min biogas supply rate and λ=1.0 at different spark timings
0.80 0.85 0.90 0.95
Figure 4.16a CoVIMEP v.s. excess air ratio with 260L/min biogas supply and different spark timings
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0.80 0.85 0.90 0.95 1.00 1.05 1.10
11
Figure 4.16b CoVIMEP v.s. excess air ratio with 240L/min biogas supply and different spark timings
Figure 4.16c CoVIMEP v.s. excess air ratio with 220L/min biogas supply and different spark timings
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Figure 4.17 Estimated CH4 consumption ratios v.s. CoVIMEP with different spark timings
Figure 4.18 Comparison of thermal efficiency with other researches at 200L/min biogas supply