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Combustion and emissions behaviour assessment of a partially premixed charge compression ignition (PCCI) engine with diesel and fumigated ethanol
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2nd International Conference on Energy and Power, ICEP2018, 13–15 December 2018, 2nd International Conference on Energy and Power, ICEP2018, 13–15 December 2018, Sydney, Australia Sydney, Australia
Combustion and emissions behaviour assessment of a partially Combustion andInternational emissions behaviour assessment a partially The 15th Symposium on District Heating andof Cooling premixed charge compression ignition (PCCI) engine with diesel premixed charge compression ignition (PCCI) engine with diesel and fumigated Assessing the feasibility of usingethanol the heat demand-outdoor and fumigated ethanol temperature function a long-term district heatChintala demand forecast * Shyam Pandeyfor , Swapnil Bhurat, Venkateswarlu * Shyam Pandey , Swapnila Bhurat, Venkateswarlu Chintala a,b,c a b c I. Andrić *, A. Pina , P. Ferrão , J. Fournier ., B. Lacarrière , O.India Le Correc School of Engineering, University of Petroleum and Energy Studies (UPES), Dehradun, 248007,
School of Engineering, University of Petroleum and Energy Studies (UPES), Dehradun, 248007, India IN+ Center for Innovation, Technology and Policy Research - Instituto Superior Técnico, Av. Rovisco Pais 1, 1049-001 Lisbon, Portugal b Veolia Recherche & Innovation, 291 Avenue Dreyfous Daniel, 78520 Limay, France Abstract c Département Systèmes Énergétiques et Environnement - IMT Atlantique, 4 rue Alfred Kastler, 44300 Nantes, France a
Abstract The study is aimed to evaluate the combustion and emission characteristics of a partially premixed charge compression ignition (PCCI) engine withtodiesel and the ethanol fuels. Ethanol was fumigated with of preheated intake air at charge 40°C and inducted into the The study is aimed evaluate combustion and emission characteristics a partially premixed compression ignition intake manifold of thediesel test engine. Experimental tests were out with varying proportions at different (PCCI) engine with and ethanol fuels. Ethanol was carried fumigated preheated intake airofatpremixed 40°C andethanol inducted into the Abstract engine manifold loading conditions 1, 2, Experimental 3, and 4 bar brake meancarried effective (BMEP). It wasofexplored at lower BMEP, intake of the test of engine. tests were out pressures with varying proportions premixedthat ethanol at different oxides of nitrogen (NOx) of were decreased an increment of premixed ethanol, however, higher BMEP, the emissions engine loading conditions 1, 2, 3, and 4with bar brake mean effective pressures (BMEP). It wasatexplored that at lower BMEP, District heating networks are commonly addressed in the literature as one of the most effective solutions for decreasing the increased. At all loads, opacity decreased premixedhowever, ethanol share. At part loads,the hydrocarbon decreased with exceedingly an incrementwith of increasing premixed ethanol, at higher BMEP, emissions oxides of nitrogen (NOsmoke x) were greenhouse gas emissions from the building sector. These systems require high investments which are returned through theheat heat (HC) and carbon monoxide (CO) emissions wereexceedingly increased because of the high latent ethanol heat of vaporization ethanol. Net increased. At all loads, smoke opacity decreased with increasing premixed share. At partofloads, hydrocarbon sales. Due to the changed climate conditions and building renovation policies, heat demand in the future could decrease, release rate and in-cylinder pressure rise were to be increased with increasing load. Overall, it could be (HC) and carbon monoxide (CO) emissions werefound increased because of the highanlatent heat ofengine vaporization of ethanol. Net heat prolonging the return period. determined the performance of therise PCCI ethanol fumigation is comparable with the conventional release rate that andinvestment in-cylinder pressure wereengine foundwith to be increased with an increasing engine load. Overall, itdiesel couldfuel be The main scope of this paper is toofassess the feasibility of using the fumigation heat demandis –comparable outdoor temperature function for heat demand operation. determined that the performance the PCCI engine with ethanol with the conventional diesel fuel forecast. The district of Alvalade, located in Lisbon (Portugal), was used as a case study. The district is consisted of 665 operation. vary in both construction ©buildings 2018 Thethat Authors. Published by Elsevierperiod Ltd. and typology. Three weather scenarios (low, medium, high) and three district © 2019 The Authors. Published by Elsevier Ltd. renovation scenarios were developed (shallow, deep). To estimate the error, obtained heat demand values were © 2018 The Authors. Published by Elsevier Ltd. intermediate, This is an open access article under the CC BY-NC-ND license (https://creativecommons.org/licenses/by-nc-nd/4.0/) This is an open access the CC license (https://creativecommons.org/licenses/by-nc-nd/4.0/) compared with resultsarticle fromunder aunder dynamic heatBY-NC-ND demand model, previously developed by theConference authors. on Energy and This is an and open access article under the CC BY-NC-ND license (https://creativecommons.org/licenses/by-nc-nd/4.0/) Selection peer-review responsibility of the scientific committee of the theand 2ndvalidated International Selection andshowed peer-review underonly responsibility of theis scientific committee of 2nd International Conference on Energy and The results that when weather change considered, the margin of error could be acceptable for some applications Selection and peer-review under responsibility of the scientific committee of the 2nd International Conference on Energy and Power, ICEP2018. Power, ICEP2018. (the error in annual demand was lower than 20% for all weather scenarios considered). However, after introducing renovation Power, ICEP2018. scenarios,Ethanol; the error value increased up to 59.5% (depending on the weather and renovation scenarios combination considered). Keywords: PCCI; diesel The valueEthanol; of slope coefficient increased on average within the range of 3.8% up to 8% per decade, that corresponds to the Keywords: PCCI; diesel decrease in the number of heating hours of 22-139h during the heating season (depending on the combination of weather and renovation scenarios considered). On the other hand, function intercept increased for 7.8-12.7% per decade (depending on the scenarios). The values suggested could be used to modify the function parameters for the scenarios considered, and 1.coupled Introduction the accuracy of heat demand estimations. 1.improve Introduction
Partially premixed charge compression ignition (PCCI) engines are gaining significant importance in view of
© Partially 2017 The premixed Authors. Published by Elsevier Ltd. charge compression ignition (PCCI) engines are gaining significant importance in view of Peer-review under responsibility of the Scientific of The 15th International Symposium on District Heating and * Corresponding author. Tel.: 00911352770137/ 1347;Committee fax +91 1352776090/95 Cooling. E-mail address:author. [email protected] * Corresponding Tel.: 0091135- 2770137/ 1347; fax +91 1352776090/95
E-mail address: [email protected] Keywords: Heat demand; Forecast; Climate change 1876-6102 © 2018 The Authors. Published by Elsevier Ltd. This is an open access under the CC BY-NC-ND license (https://creativecommons.org/licenses/by-nc-nd/4.0/) 1876-6102 © 2018 Thearticle Authors. Published by Elsevier Ltd. Selection under responsibility of the scientific of the 2nd International Conference on Energy and Power, ICEP2018. This is an and openpeer-review access article under the CC BY-NC-ND licensecommittee (https://creativecommons.org/licenses/by-nc-nd/4.0/) Selection and peer-review under responsibility of the scientific committee of the 2nd International Conference on Energy and Power, ICEP2018. 1876-6102 © 2017 The Authors. Published by Elsevier Ltd. Peer-review under responsibility of the Scientific Committee of The 15th International Symposium on District Heating and Cooling. 1876-6102 © 2019 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license (https://creativecommons.org/licenses/by-nc-nd/4.0/) Selection and peer-review under responsibility of the scientific committee of the 2nd International Conference on Energy and Power, ICEP2018. 10.1016/j.egypro.2019.02.210
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stringent emission norms and higher performance. The PCCI engines offer better combustion performance due to homogeneous combustion of air-fuel charge. Utilization of alcohol as a premixed fuel is one of the promising options towards achieving homogeneous combustion and thus lower emissions and better fuel economy. Alcohols could be directly supplied to the engine by fumigation technology. Fumigation process involves atomization of fuel and mixing with intake air, prior to its induction to the engine cylinder [1]. Fumigation of alcohol studies was carried out extensively in China [2, 3] and other parts of the world, especially on multi-cylinder engines. For example, Griffith et al. [4] examined the effect of ethanol fumigation on Harvester farm tractor engine (turbocharged direct injection diesel engine) by both laboratory and field-testing trails. Ethanol fumigation was achieved by installing electronically controlled multi-point fuel injection system [4]. Their experimental test results revealed that maximum of 28% fuel energy could be supplied by ethanol at low engine loads and 13% at full load [4]. Similarly, Tsang et al. [2] studied fumigation of ethanol on multi-cylinder diesel engine (4.334 L, Isuzu 4HF1) fueled with Euro-V diesel. At the engine loading of 0.08 MPa and 0.70 MPa, carbon monoxide (CO) emission increased significantly at 20% ethanol share [2]. At the same loading conditions, hydrocarbon (HC) emission increased by 3.3 and 2.4 times. The reduction in oxides of nitrogen (NO x) with reference to pure diesel combustion was more prominent at part loads as compared to full loads [2]. Smoke opacity decreased significantly at medium and high engine loads with an increase in fumigation ethanol [2]. Experimental investigations of Hebbar et al. [5] with fumigated ethanol share of 5 to 15% revealed the NOx emission reduction about 15%. Pure diesel combustion along with EGR emits higher smoke as compared to fumigation ethanol mode [5]. Horng-Wen Wu et al. [6] investigated the combustion and emission of a PCCI engine using ethanol and gasoline as a premixed fuel and diesel as a directly injected fuel in a single cylinder compression ignition engine. Concentrations of NO x and smoke were lower in case of premixed ethanol as compared to premixed gasoline [6]. They have found NOx concentration reduction and HC emission increased with an increase in premixed fuel ratio [6]. Pedrozo et al. studied ethanol-diesel dual-fuel combustion by Miller cycle and charge air cooling by using single cylinder heavy-duty engine [7]. They found application of a Miller cycle strategy that involves late intake valve closing lead to retard the ethanol auto-ignition process. In addition, induction air-cooling was done by using water cooler successfully impeded early ignition of ethanol. As per the reported results, the higher net indicated efficiency and lower NOx emissions could be attained by using Miller cycle and charge air-cooling. Haifeng et al. [8] examined effect of port injection of hydrous ethanol on combustion and emission characteristics of singlecylinder, 4-valve, 4-stroke and water-cooled diesel engine. They found that higher share of ethanol leads to adversely affect thermal and indicated thermal efficiency. Hydrous ethanol purity ranges from 60% to 100%, thermal efficiency showed significant reduction at the ethanol purity of 60%. Performance of the engine can be improved by controlling intake temperature of air, fuel injection pressure and EGR rate. Lower purity of ethanol was found favourable for NOx emissions. Sahin et.al [9] examined the effect of ethanol fumigation on the engine emissions and performance characteristics. It has proved that ethanol fumigation can enhance the performance of an engine along with decrement in smoke and NOx emissions. Several investigations were carried out with pre-heated air to assist the alcohol vaporization/fumigation. For example, Kaneko et al. [10] conducted a study with the intake air temperature at 20 ºC. When diesel fuel was used, HC emission increased dramatically. However, NOx and smoke emissions were also increased considerably with diesel fuel, indicating that the mixture was not sufficiently homogenous. Olsson et al. [11] utilized isooctane and nheptane as fuel candidates in a PCCI engine to assess the combustion characteristics. Similarly, Kim et al. [12] found that PCCI strategy as an effective way to control HCCI combustion. The combustion and emission characteristics showed a reduction in both NOx and soot emissions simultaneously [12]. NOx and soot emission decreased when diesel was used as a port fuel at room temperature, however, at elevated temperature it resulted in deterioration of combustion, leading to the narrowed operating limit at a higher premixed ratio [12]. Naoyam et al. [13] conducted an experimental study for control of fuel ignition timing and suppression of rapid combustion by injecting water in a PCCI engine [13]. The possible engine operating range with ultra-low NOx and smokeless combustion was extended to a higher load range with the water injection [13]. It is explored from the aforementioned literature that the several studies have been conducted on ethanol fumigation with lower shares. In addition, the information on the assessment of the entire spectrum of engine behavior with ethanol fumigation is inadequate. To address these issues, the present study is focused on the development of a PCCI engine to operate on ethanol and diesel fuel. To enhance the homogeneity of fumigated ethanol, the engine intake air was pre-heated to 40 °C. Engine tests were conducted at four different engine loads, i.e., 1 to 4 bar BMEP at varying ratios of premixed ethanol with diesel. To understand the effect of varying premixed ethanol on combustion and emissions,
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maximum in-cylinder pressure rise and net heat release rate (NHRR) along with CO, HC, NOx and smoke emissions were studied. 2. Experimental test setup details Schematic diagram of the experiential test setup is shown in Fig.1. A 3.5 kW rated power single cylinder compression ignition (CI) engine was coupled with an eddy current dynamometer. A fuel injection system for diesel and ethanol was customized as per the requirement. The setup was instrumented for capturing the data related to incylinder pressure, airflow, fuel flow, temperatures and load measurements. Various sensors and instruments used for measurements were integrated with computerized data acquisition system. The test rig has a stand-alone panel box consisting of the airbox, fuel tank, manometer, fuel measuring unit, transmitters for the air and fuel flow measurements, process indicator and engine indicator. A partial amount of ethanol was fumigated into the air intake manifold of the engine and diesel fuel was directly injected into the engine cylinder. The carburetor was failed to provide a precise and varying quantity of fuel at different loads under unthrottled condition. Therefore, advanced multi-point fuel injection system was developed for fumigated ethanol injection. The ethanol injection system was controlled by an electronic control unit (ECU). The proximity sensor and engine rpm sensors were the two inputs variable to the ECU. Based on these inputs and the logic, it can change the output pulse for the injector and delay in order to achieve the precise quantity of fuel. Injection period or quantity of fuel injected can be changed by altering the pulse duration given to the solenoid operated injector. HC, CO, and NO x emissions were measured with the Digas analyzer.
Fig.1. Schematic diagram of engine experimental test setup
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3. Results and discussion 3.1. Effect of premixed ethanol on net heat release rate (NHRR) and maximum in-cylinder pressure rise (𝑝𝑝𝑚𝑚𝑚𝑚𝑚𝑚 )
Fig. 2 shows the variation of in-cylinder maximum pressure (pmax ) rise and NHRR at varying premixed ethanol shares at different engine loading conditions. The maximum NHRR and pmax increased with increasing engine loads under all operating conditions. At 1 to 3 bar BMEP, the maximum NHRR and pmax decreased with increasing premixed ethanol quantity from 2 ml to 8 ml as seen in Fig. 2. However, the trend was reversed at 4 bar BMEP. The reason for the NHRR and pmax reduction could be due to reduction in-cylinder temperature with the cooling effect of ethanol vapors. It is well accepted that latent heat of vaporization of ethanol is higher than diesel, which reduces the in-cylinder temperature drastically during combustion. However, the reverse trend could be due to the dominant effect of higher flame speed of ethanol. It is observed that the maximum NHRR rate increased with an increase in ethanol at high engine load (4 bar BMEP), the maximum NHRR was observed with 8 ml of premixed ethanol. Thus, it is clearly evident from the figure that at high load, premixed ethanol burns faster and leads to increase in pmax and maximum NHRR. Hayes et al. [14] also reported similar trends of increase in pmax with increasing premixed proportion of ethanol at 5 bar BMEP. In the present study, the pmax decreased from 57.8 bar with diesel alone operation to 53.4 bar with 10 ml ethanol fumigation at 2 bar BMEP. Similarly, the maximum NHRR decreased form 39.5 J/degree with diesel to 34.3 bar J/degree with ethanol at 2 bar BMEP condition. However at 4 bar BMEP, the pmax and maximum NHRR increased from 62.9 bar and 48.9 J/degree to 66.2 bar and 60.2 J/degree.
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Fig. 2. Effect of premixed ethanol on Maximum NHRR and in-cylinder pressure at (a) 1 bar BMEP , (b) 2 bar BMEP, (c) 3 bar BMEP (d) 4 bar BMEP
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3.2. Effect of premixed ethanol on NOx and smoke emissions The NOx generation is affected by two mutually countering effects. As NOx is produced at high temperature, the high latent heat of vaporization of ethanol creates a cooling effect, whereas an increase in ignition delay and heat release rate in premixed phase lead to increase in combustion temperature. At low loads (1-3 bar BMEP), NOx decreased with an increase in ethanol quantity due to the cooling effect produced by ethanol. However, at 4 bar BMEP, the trends were reversed with an increase in premixed ethanol as shown in Fig. 3. It is known that NOx formation directly depends on in-cylinder temperature and pressure [15]. At 1 bar BMEP, NOx emissions decreased with 4 ml and 10 ml ethanol by about 43% and 78% respectively as compared to pure diesel operation. Similarly, NOx emissions decreased with increase in premixed ethanol, except at 4 bar BMEP, however, the rate of reduction is lesser as compared to 1 bar BMEP. Bhupendra et al. [16] also observed decrement in NOx emissions at similar engine operating conditions. Fig. 3 depicts the variation of smoke opacity (%) with a premixed ethanol fumigation. In general, the smoke opacity changes inversely with premixed ethanol. There are several reasons leading to such reduction of smoke emissions when premixed ethanol is supplied to PCCI engine. Low amount of diesel fuel is burned in the diffusion mode which reduces the smoke formation. Increase in ignition delay increases the amount of diesel fuel burned in the diffusion mode. Thus, the lesser smoke formation has been observed during premixed ethanol combustion. AbuQudais et al. [1] also showed a reduction of smoke emission under similar conditions. 9
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Fig. 3. Effect of premixed ethanol on NOx and smoke emissions at (a) 1 bar BMEP , (b) 2 bar BMEP, (c) 3 bar BMEP (d) 4 bar BMEP
3.3. Effect of premixed ethanol on CO and HC emissions Fig. 4 shows the variation HC and CO emissions with different premixed ethanol fumigation quantities. It is found that HC and CO emissions increased with the increase in premixed ethanol at low engine loads. The CO and HC emissions increased at the part and moderate engine loads due to the high latent heat of vaporization of ethanol.
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The main reason for HC and CO emissions increase could be due to a decrease in NHRR and pmax which further lead to incomplete combustion of the fuel. At 4 bar BMEP, due to increases in pmax and NHRR, CO emissions decreased with increase in premixed ethanol. However, HC emissions increased with premixed ethanol ratio but the rate of increase is lower at higher loads as compared to low loads.
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Fig. 4. Effect of premixed ethanol on CO and HC emissions at (a) 1 bar BMEP, (b) 2 bar BMEP, (c) 3 bar BMEP (d) 4 bar BMEP
4. Conclusions Based on the experimental investigation carried out on ethanol fumigation, it is concluded that NHRR and maximum in-cylinder pressure rise reduced at lower engine loads (BMEP) due to the high latent heat of vaporization (840 kJ/kg) of ethanol, which further lead to increase in CO and HC emissions. However, at higher loads, CO emissions decreased with increase in NHRR and maximum in-cylinder pressure. NOx emissions decreased with an increase in premixed ethanol at all engine loads, except at 4 bar BMEP. Smoke emission decreased for all loads with increasing premixed ethanol share. Based on the comparable behaviour of the engine pertaining to combustion, performance, and emissions. It is concluded that replacing diesel (polyaromatic hydrocarbons) with ethanol is found to be beneficial. References
[1] Abu-Qudais, M., O. and M.Q. Haddad, The effect of alcohol fumigation on diesel engine performance and emissions. Energy Conversion & Management, 2000. 41: p. 389-399. [2] Tsang, K.S. and Z.H.C. Zhang, C. S. Chan, T. L., Reducing Emissions of a Diesel Engine Using Fumigation Ethanol and a Diesel Oxidation Catalyst. Energy & Fuels, 2010. 24(11): p. 6156-6165. [3] Zhang Z.H. and K.S. Tsang, Cheunga,C.S., Chana, T.L., Yao Effect of fumigation methanol and ethanol on the gaseous and particulate emissions of a direct-injection diesel engine. Atmospheric Environment 2011. 45 p. 2001-2008.
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[4] Griffith, D. and L. Savage, and Goering, CE Evaluation of an Ethanol-Fumigated Diesel Tractor. American Society of Agricultural Engineers (ASAE), 1988. ASAE Paper 88-1558. [5] Hebbar, G.S. and K.B. Anantha, Control of NOx from a DI dieselengine with hot EGR and ethanol fumigation:an experimental investigation. IOSR Journal of Engineering, 2012. 2: p. 45–53. [6] Horng-Wen Wu and D.-J.O. Ren-Hung Wang, Ying-Chuan Chen, Teng-yu Chen Reduction of smoke and nitrogen oxides of a partial HCCI engine using premixed gasoline and ethanol with air. Applied Energy, 2011. 88(11): p. 3882-3890. [7] Pedrozo, V.B. and H. Zhao, Improvement in high load ethanol-diesel dual-fuel combustion by Miller cycle and charge air cooling. Applied Energy, 2018. 210: p. 138-151. [8] Liu, H., et al., Effects of port injection of hydrous ethanol on combustion and emission characteristics in dual-fuel reactivity controlled compression ignition (RCCI) mode. Energy, 2018. 145: p. 592-602. [9] Şahin, Z., O. Durgun, and M. Kurt, Experimental investigation of improving diesel combustion and engine performance by ethanol fumigation-heat release and flammability analysis. Energy Conversion and Management, 2015. 89: p. 175-187. [10] Kaneko, N. and H. Ando, Ogawa, H., Miyamoto, N. , Expansion of the operating range with in-cylinder water injection in a premixed charge compression ignition engine. Society of Automotive Engineers, 2002. SAE Paper 2002-01-1743. [11] Olsson, J.-O. and P. Tunestal, Johansson Bengt Closed-loop control of an HCCI engine. Society of Automotive Engineers, 2001. SAE papers 2001-01-1031. [12] Kim, D. and C. Lee, Improved emission characteristics of HCCI engine by various premixed fuels and cooled EGR. Fuel, 2006. 85(5-6): p. 695-704. [13] Naoyam, K. and A. Hirokazu, Hideyuki, Ogawa, Noboru Miyamoto Expansion of the Operating Range with In-Cylinder Water Injection in a Premixed Charge Compression Ignition Engine. Society of Automotive Engineers, 2002. SAE Paper 2002-01-1743. [14] Hayes, T. and L. Savage, White RA., and Sorenson SC, The effect of fumigation of different ethanol proofs on a turbocharged diesel engine. Society of Automotive Engineers, 1988. SAE Paper 880497. [15] Chintala, V. and K.A. Subramanian, Experimental investigation on effect of enhanced premixed charge on combustion characteristics of a direct injection diesel engine. International Journal of Advances in Engineering Sciences and Applied Mathematics, 2014. 6(1-2): p. 3-16. [16] Bhupendra Singh Chauhana and S.S.P. Naveen Kumar, Yong Du Jun Experimental studies on fumigation of ethanol in a small capacity Diesel engine. Energy, 2011. 36: p. 1030-1038.
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Energy (2019) 000–000 590–596 EnergyProcedia Procedia160 00 (2017) www.elsevier.com/locate/procedia
2nd International Conference on Energy and Power, ICEP2018, 13–15 December 2018, 2nd International Conference on Energy and Power, ICEP2018, 13–15 December 2018, Sydney, Australia Sydney, Australia
Combustion and emissions behaviour assessment of a partially Combustion andInternational emissions behaviour assessment a partially The 15th Symposium on District Heating andof Cooling premixed charge compression ignition (PCCI) engine with diesel premixed charge compression ignition (PCCI) engine with diesel and fumigated Assessing the feasibility of usingethanol the heat demand-outdoor and fumigated ethanol temperature function a long-term district heatChintala demand forecast * Shyam Pandeyfor , Swapnil Bhurat, Venkateswarlu * Shyam Pandey , Swapnila Bhurat, Venkateswarlu Chintala a,b,c a b c I. Andrić *, A. Pina , P. Ferrão , J. Fournier ., B. Lacarrière , O.India Le Correc School of Engineering, University of Petroleum and Energy Studies (UPES), Dehradun, 248007,
School of Engineering, University of Petroleum and Energy Studies (UPES), Dehradun, 248007, India IN+ Center for Innovation, Technology and Policy Research - Instituto Superior Técnico, Av. Rovisco Pais 1, 1049-001 Lisbon, Portugal b Veolia Recherche & Innovation, 291 Avenue Dreyfous Daniel, 78520 Limay, France Abstract c Département Systèmes Énergétiques et Environnement - IMT Atlantique, 4 rue Alfred Kastler, 44300 Nantes, France a
Abstract The study is aimed to evaluate the combustion and emission characteristics of a partially premixed charge compression ignition (PCCI) engine withtodiesel and the ethanol fuels. Ethanol was fumigated with of preheated intake air at charge 40°C and inducted into the The study is aimed evaluate combustion and emission characteristics a partially premixed compression ignition intake manifold of thediesel test engine. Experimental tests were out with varying proportions at different (PCCI) engine with and ethanol fuels. Ethanol was carried fumigated preheated intake airofatpremixed 40°C andethanol inducted into the Abstract engine manifold loading conditions 1, 2, Experimental 3, and 4 bar brake meancarried effective (BMEP). It wasofexplored at lower BMEP, intake of the test of engine. tests were out pressures with varying proportions premixedthat ethanol at different oxides of nitrogen (NOx) of were decreased an increment of premixed ethanol, however, higher BMEP, the emissions engine loading conditions 1, 2, 3, and 4with bar brake mean effective pressures (BMEP). It wasatexplored that at lower BMEP, District heating networks are commonly addressed in the literature as one of the most effective solutions for decreasing the increased. At all loads, opacity decreased premixedhowever, ethanol share. At part loads,the hydrocarbon decreased with exceedingly an incrementwith of increasing premixed ethanol, at higher BMEP, emissions oxides of nitrogen (NOsmoke x) were greenhouse gas emissions from the building sector. These systems require high investments which are returned through theheat heat (HC) and carbon monoxide (CO) emissions wereexceedingly increased because of the high latent ethanol heat of vaporization ethanol. Net increased. At all loads, smoke opacity decreased with increasing premixed share. At partofloads, hydrocarbon sales. Due to the changed climate conditions and building renovation policies, heat demand in the future could decrease, release rate and in-cylinder pressure rise were to be increased with increasing load. Overall, it could be (HC) and carbon monoxide (CO) emissions werefound increased because of the highanlatent heat ofengine vaporization of ethanol. Net heat prolonging the return period. determined the performance of therise PCCI ethanol fumigation is comparable with the conventional release rate that andinvestment in-cylinder pressure wereengine foundwith to be increased with an increasing engine load. Overall, itdiesel couldfuel be The main scope of this paper is toofassess the feasibility of using the fumigation heat demandis –comparable outdoor temperature function for heat demand operation. determined that the performance the PCCI engine with ethanol with the conventional diesel fuel forecast. The district of Alvalade, located in Lisbon (Portugal), was used as a case study. The district is consisted of 665 operation. vary in both construction ©buildings 2018 Thethat Authors. Published by Elsevierperiod Ltd. and typology. Three weather scenarios (low, medium, high) and three district © 2019 The Authors. Published by Elsevier Ltd. renovation scenarios were developed (shallow, deep). To estimate the error, obtained heat demand values were © 2018 The Authors. Published by Elsevier Ltd. intermediate, This is an open access article under the CC BY-NC-ND license (https://creativecommons.org/licenses/by-nc-nd/4.0/) This is an open access the CC license (https://creativecommons.org/licenses/by-nc-nd/4.0/) compared with resultsarticle fromunder aunder dynamic heatBY-NC-ND demand model, previously developed by theConference authors. on Energy and This is an and open access article under the CC BY-NC-ND license (https://creativecommons.org/licenses/by-nc-nd/4.0/) Selection peer-review responsibility of the scientific committee of the theand 2ndvalidated International Selection andshowed peer-review underonly responsibility of theis scientific committee of 2nd International Conference on Energy and The results that when weather change considered, the margin of error could be acceptable for some applications Selection and peer-review under responsibility of the scientific committee of the 2nd International Conference on Energy and Power, ICEP2018. Power, ICEP2018. (the error in annual demand was lower than 20% for all weather scenarios considered). However, after introducing renovation Power, ICEP2018. scenarios,Ethanol; the error value increased up to 59.5% (depending on the weather and renovation scenarios combination considered). Keywords: PCCI; diesel The valueEthanol; of slope coefficient increased on average within the range of 3.8% up to 8% per decade, that corresponds to the Keywords: PCCI; diesel decrease in the number of heating hours of 22-139h during the heating season (depending on the combination of weather and renovation scenarios considered). On the other hand, function intercept increased for 7.8-12.7% per decade (depending on the scenarios). The values suggested could be used to modify the function parameters for the scenarios considered, and 1.coupled Introduction the accuracy of heat demand estimations. 1.improve Introduction
Partially premixed charge compression ignition (PCCI) engines are gaining significant importance in view of
© Partially 2017 The premixed Authors. Published by Elsevier Ltd. charge compression ignition (PCCI) engines are gaining significant importance in view of Peer-review under responsibility of the Scientific of The 15th International Symposium on District Heating and * Corresponding author. Tel.: 00911352770137/ 1347;Committee fax +91 1352776090/95 Cooling. E-mail address:author. [email protected] * Corresponding Tel.: 0091135- 2770137/ 1347; fax +91 1352776090/95
E-mail address: [email protected] Keywords: Heat demand; Forecast; Climate change 1876-6102 © 2018 The Authors. Published by Elsevier Ltd. This is an open access under the CC BY-NC-ND license (https://creativecommons.org/licenses/by-nc-nd/4.0/) 1876-6102 © 2018 Thearticle Authors. Published by Elsevier Ltd. Selection under responsibility of the scientific of the 2nd International Conference on Energy and Power, ICEP2018. This is an and openpeer-review access article under the CC BY-NC-ND licensecommittee (https://creativecommons.org/licenses/by-nc-nd/4.0/) Selection and peer-review under responsibility of the scientific committee of the 2nd International Conference on Energy and Power, ICEP2018. 1876-6102 © 2017 The Authors. Published by Elsevier Ltd. Peer-review under responsibility of the Scientific Committee of The 15th International Symposium on District Heating and Cooling. 1876-6102 © 2019 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license (https://creativecommons.org/licenses/by-nc-nd/4.0/) Selection and peer-review under responsibility of the scientific committee of the 2nd International Conference on Energy and Power, ICEP2018. 10.1016/j.egypro.2019.02.210
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stringent emission norms and higher performance. The PCCI engines offer better combustion performance due to homogeneous combustion of air-fuel charge. Utilization of alcohol as a premixed fuel is one of the promising options towards achieving homogeneous combustion and thus lower emissions and better fuel economy. Alcohols could be directly supplied to the engine by fumigation technology. Fumigation process involves atomization of fuel and mixing with intake air, prior to its induction to the engine cylinder [1]. Fumigation of alcohol studies was carried out extensively in China [2, 3] and other parts of the world, especially on multi-cylinder engines. For example, Griffith et al. [4] examined the effect of ethanol fumigation on Harvester farm tractor engine (turbocharged direct injection diesel engine) by both laboratory and field-testing trails. Ethanol fumigation was achieved by installing electronically controlled multi-point fuel injection system [4]. Their experimental test results revealed that maximum of 28% fuel energy could be supplied by ethanol at low engine loads and 13% at full load [4]. Similarly, Tsang et al. [2] studied fumigation of ethanol on multi-cylinder diesel engine (4.334 L, Isuzu 4HF1) fueled with Euro-V diesel. At the engine loading of 0.08 MPa and 0.70 MPa, carbon monoxide (CO) emission increased significantly at 20% ethanol share [2]. At the same loading conditions, hydrocarbon (HC) emission increased by 3.3 and 2.4 times. The reduction in oxides of nitrogen (NO x) with reference to pure diesel combustion was more prominent at part loads as compared to full loads [2]. Smoke opacity decreased significantly at medium and high engine loads with an increase in fumigation ethanol [2]. Experimental investigations of Hebbar et al. [5] with fumigated ethanol share of 5 to 15% revealed the NOx emission reduction about 15%. Pure diesel combustion along with EGR emits higher smoke as compared to fumigation ethanol mode [5]. Horng-Wen Wu et al. [6] investigated the combustion and emission of a PCCI engine using ethanol and gasoline as a premixed fuel and diesel as a directly injected fuel in a single cylinder compression ignition engine. Concentrations of NO x and smoke were lower in case of premixed ethanol as compared to premixed gasoline [6]. They have found NOx concentration reduction and HC emission increased with an increase in premixed fuel ratio [6]. Pedrozo et al. studied ethanol-diesel dual-fuel combustion by Miller cycle and charge air cooling by using single cylinder heavy-duty engine [7]. They found application of a Miller cycle strategy that involves late intake valve closing lead to retard the ethanol auto-ignition process. In addition, induction air-cooling was done by using water cooler successfully impeded early ignition of ethanol. As per the reported results, the higher net indicated efficiency and lower NOx emissions could be attained by using Miller cycle and charge air-cooling. Haifeng et al. [8] examined effect of port injection of hydrous ethanol on combustion and emission characteristics of singlecylinder, 4-valve, 4-stroke and water-cooled diesel engine. They found that higher share of ethanol leads to adversely affect thermal and indicated thermal efficiency. Hydrous ethanol purity ranges from 60% to 100%, thermal efficiency showed significant reduction at the ethanol purity of 60%. Performance of the engine can be improved by controlling intake temperature of air, fuel injection pressure and EGR rate. Lower purity of ethanol was found favourable for NOx emissions. Sahin et.al [9] examined the effect of ethanol fumigation on the engine emissions and performance characteristics. It has proved that ethanol fumigation can enhance the performance of an engine along with decrement in smoke and NOx emissions. Several investigations were carried out with pre-heated air to assist the alcohol vaporization/fumigation. For example, Kaneko et al. [10] conducted a study with the intake air temperature at 20 ºC. When diesel fuel was used, HC emission increased dramatically. However, NOx and smoke emissions were also increased considerably with diesel fuel, indicating that the mixture was not sufficiently homogenous. Olsson et al. [11] utilized isooctane and nheptane as fuel candidates in a PCCI engine to assess the combustion characteristics. Similarly, Kim et al. [12] found that PCCI strategy as an effective way to control HCCI combustion. The combustion and emission characteristics showed a reduction in both NOx and soot emissions simultaneously [12]. NOx and soot emission decreased when diesel was used as a port fuel at room temperature, however, at elevated temperature it resulted in deterioration of combustion, leading to the narrowed operating limit at a higher premixed ratio [12]. Naoyam et al. [13] conducted an experimental study for control of fuel ignition timing and suppression of rapid combustion by injecting water in a PCCI engine [13]. The possible engine operating range with ultra-low NOx and smokeless combustion was extended to a higher load range with the water injection [13]. It is explored from the aforementioned literature that the several studies have been conducted on ethanol fumigation with lower shares. In addition, the information on the assessment of the entire spectrum of engine behavior with ethanol fumigation is inadequate. To address these issues, the present study is focused on the development of a PCCI engine to operate on ethanol and diesel fuel. To enhance the homogeneity of fumigated ethanol, the engine intake air was pre-heated to 40 °C. Engine tests were conducted at four different engine loads, i.e., 1 to 4 bar BMEP at varying ratios of premixed ethanol with diesel. To understand the effect of varying premixed ethanol on combustion and emissions,
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maximum in-cylinder pressure rise and net heat release rate (NHRR) along with CO, HC, NOx and smoke emissions were studied. 2. Experimental test setup details Schematic diagram of the experiential test setup is shown in Fig.1. A 3.5 kW rated power single cylinder compression ignition (CI) engine was coupled with an eddy current dynamometer. A fuel injection system for diesel and ethanol was customized as per the requirement. The setup was instrumented for capturing the data related to incylinder pressure, airflow, fuel flow, temperatures and load measurements. Various sensors and instruments used for measurements were integrated with computerized data acquisition system. The test rig has a stand-alone panel box consisting of the airbox, fuel tank, manometer, fuel measuring unit, transmitters for the air and fuel flow measurements, process indicator and engine indicator. A partial amount of ethanol was fumigated into the air intake manifold of the engine and diesel fuel was directly injected into the engine cylinder. The carburetor was failed to provide a precise and varying quantity of fuel at different loads under unthrottled condition. Therefore, advanced multi-point fuel injection system was developed for fumigated ethanol injection. The ethanol injection system was controlled by an electronic control unit (ECU). The proximity sensor and engine rpm sensors were the two inputs variable to the ECU. Based on these inputs and the logic, it can change the output pulse for the injector and delay in order to achieve the precise quantity of fuel. Injection period or quantity of fuel injected can be changed by altering the pulse duration given to the solenoid operated injector. HC, CO, and NO x emissions were measured with the Digas analyzer.
Fig.1. Schematic diagram of engine experimental test setup
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3. Results and discussion 3.1. Effect of premixed ethanol on net heat release rate (NHRR) and maximum in-cylinder pressure rise (𝑝𝑝𝑚𝑚𝑚𝑚𝑚𝑚 )
Fig. 2 shows the variation of in-cylinder maximum pressure (pmax ) rise and NHRR at varying premixed ethanol shares at different engine loading conditions. The maximum NHRR and pmax increased with increasing engine loads under all operating conditions. At 1 to 3 bar BMEP, the maximum NHRR and pmax decreased with increasing premixed ethanol quantity from 2 ml to 8 ml as seen in Fig. 2. However, the trend was reversed at 4 bar BMEP. The reason for the NHRR and pmax reduction could be due to reduction in-cylinder temperature with the cooling effect of ethanol vapors. It is well accepted that latent heat of vaporization of ethanol is higher than diesel, which reduces the in-cylinder temperature drastically during combustion. However, the reverse trend could be due to the dominant effect of higher flame speed of ethanol. It is observed that the maximum NHRR rate increased with an increase in ethanol at high engine load (4 bar BMEP), the maximum NHRR was observed with 8 ml of premixed ethanol. Thus, it is clearly evident from the figure that at high load, premixed ethanol burns faster and leads to increase in pmax and maximum NHRR. Hayes et al. [14] also reported similar trends of increase in pmax with increasing premixed proportion of ethanol at 5 bar BMEP. In the present study, the pmax decreased from 57.8 bar with diesel alone operation to 53.4 bar with 10 ml ethanol fumigation at 2 bar BMEP. Similarly, the maximum NHRR decreased form 39.5 J/degree with diesel to 34.3 bar J/degree with ethanol at 2 bar BMEP condition. However at 4 bar BMEP, the pmax and maximum NHRR increased from 62.9 bar and 48.9 J/degree to 66.2 bar and 60.2 J/degree.
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3.2. Effect of premixed ethanol on NOx and smoke emissions The NOx generation is affected by two mutually countering effects. As NOx is produced at high temperature, the high latent heat of vaporization of ethanol creates a cooling effect, whereas an increase in ignition delay and heat release rate in premixed phase lead to increase in combustion temperature. At low loads (1-3 bar BMEP), NOx decreased with an increase in ethanol quantity due to the cooling effect produced by ethanol. However, at 4 bar BMEP, the trends were reversed with an increase in premixed ethanol as shown in Fig. 3. It is known that NOx formation directly depends on in-cylinder temperature and pressure [15]. At 1 bar BMEP, NOx emissions decreased with 4 ml and 10 ml ethanol by about 43% and 78% respectively as compared to pure diesel operation. Similarly, NOx emissions decreased with increase in premixed ethanol, except at 4 bar BMEP, however, the rate of reduction is lesser as compared to 1 bar BMEP. Bhupendra et al. [16] also observed decrement in NOx emissions at similar engine operating conditions. Fig. 3 depicts the variation of smoke opacity (%) with a premixed ethanol fumigation. In general, the smoke opacity changes inversely with premixed ethanol. There are several reasons leading to such reduction of smoke emissions when premixed ethanol is supplied to PCCI engine. Low amount of diesel fuel is burned in the diffusion mode which reduces the smoke formation. Increase in ignition delay increases the amount of diesel fuel burned in the diffusion mode. Thus, the lesser smoke formation has been observed during premixed ethanol combustion. AbuQudais et al. [1] also showed a reduction of smoke emission under similar conditions. 9
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Fig. 3. Effect of premixed ethanol on NOx and smoke emissions at (a) 1 bar BMEP , (b) 2 bar BMEP, (c) 3 bar BMEP (d) 4 bar BMEP
3.3. Effect of premixed ethanol on CO and HC emissions Fig. 4 shows the variation HC and CO emissions with different premixed ethanol fumigation quantities. It is found that HC and CO emissions increased with the increase in premixed ethanol at low engine loads. The CO and HC emissions increased at the part and moderate engine loads due to the high latent heat of vaporization of ethanol.
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The main reason for HC and CO emissions increase could be due to a decrease in NHRR and pmax which further lead to incomplete combustion of the fuel. At 4 bar BMEP, due to increases in pmax and NHRR, CO emissions decreased with increase in premixed ethanol. However, HC emissions increased with premixed ethanol ratio but the rate of increase is lower at higher loads as compared to low loads.
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Fig. 4. Effect of premixed ethanol on CO and HC emissions at (a) 1 bar BMEP, (b) 2 bar BMEP, (c) 3 bar BMEP (d) 4 bar BMEP
4. Conclusions Based on the experimental investigation carried out on ethanol fumigation, it is concluded that NHRR and maximum in-cylinder pressure rise reduced at lower engine loads (BMEP) due to the high latent heat of vaporization (840 kJ/kg) of ethanol, which further lead to increase in CO and HC emissions. However, at higher loads, CO emissions decreased with increase in NHRR and maximum in-cylinder pressure. NOx emissions decreased with an increase in premixed ethanol at all engine loads, except at 4 bar BMEP. Smoke emission decreased for all loads with increasing premixed ethanol share. Based on the comparable behaviour of the engine pertaining to combustion, performance, and emissions. It is concluded that replacing diesel (polyaromatic hydrocarbons) with ethanol is found to be beneficial. References
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