- Email: [email protected]
Numerical Study on Combustion and Emission Characteristics of a PFI Gasoline Engine with Hydrogen Direct-Injection
Available online at www.sciencedirect.com Available online at www.sciencedirect.com
ScienceDirect ScienceDirect
Energyonline Procedia 00 (2018) 000–000 Available onlineatat www.sciencedirect.com Available www.sciencedirect.com Energy Procedia 00 (2018) 000–000
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www.elsevier.com/locate/procedia www.elsevier.com/locate/procedia
Energy Procedia 158 Energy Procedia 00(2019) (2017)1449–1454 000–000 www.elsevier.com/locate/procedia
10th th
International Conference on Applied Energy (ICAE2018), 22-25 August 2018, Hong Kong, 10 International Conference on Applied Energy China(ICAE2018), 22-25 August 2018, Hong Kong, China
Numerical Study on Combustion and Emission Characteristics of a 15th International Symposium on Emission District Heating and Cooling Numerical The Study on Combustion and Characteristics of a PFI Gasoline Engine with Hydrogen Direct-Injection PFI Gasoline Engine with Hydrogen Direct-Injection Assessing the feasibility of using the heat demand-outdoor Lv Heaa, Li Jingyuanaa ,Yu Xiuminb,b,*, Li Mengliangaa , Yang Tianaa Lv He function , Li Jingyuan Xiumin *, Lidistrict Mengliang , Yang Tian forecast temperature for,Yu a long-term heat demand China Automotive Technology and Research Center Co.,Ltd., Xianfeng Dong Road, Dongli District,Tianjin 300300, China a
b China Automotive Research Center Co.,Ltd., XianfengTianjin Dong Road, DongliTianjin District,Tianjin 300300, China State KeyTechnology Laboratoryand of Automotive Simulation anf Control, University, 130022, China a,b,c a a b c c b State Key Laboratory of Automotive Simulation anf Control, Tianjin University, Tianjin 130022, China
a
I. Andrić
*, A. Pina , P. Ferrão , J. Fournier ., B. Lacarrière , O. Le Corre
a
IN+ Center for Innovation, Technology and Policy Research - Instituto Superior Técnico, Av. Rovisco Pais 1, 1049-001 Lisbon, Portugal Abstract b Veolia Recherche & Innovation, 291 Avenue Dreyfous Daniel, 78520 Limay, France Abstract c Département Systèmes Énergétiques Environnement - IMT 4 rueand Alfred Kastler,characteristics 44300 Nantes, France In this paper, the effects of hydrogen blending etradio and EGR rate onAtlantique, combustion emission of a PFI gasoline In this paper, the effects of hydrogen blending radio and EGR rate on combustion and emission characteristics of a PFI gasoline engine with hydrogen direct-injection have been investigated by numerical modeling methods using a new generation of CFD engine withsoftware hydrogen direct-injection have showed been investigated by numerical modeling methods using a new generation of CFD simulation CONVERGE. Results that compared with original engine, hydrogen direct-injection PFI gasoline simulation CONVERGE. showed that compared engine, hydrogen direct-injection PFI gasoline engine had software a better performance on Results combustion characteristics, but itwith alsooriginal had a disadvantage of increasing NOx emissions. With Abstract engine had a of better performance on radio, combustion characteristics, it also and had aCA50 disadvantage increasing NOxtoemissions. the increase hydrogen blending combustion duration but shortened advancedofand was closer TDC. AndWith CO the increase of hydrogen blending radio,NOx combustion shortened and CA50 advanced and was to TDC. And CO and THC emissions decreased, however emissionduration increased. The variations of the combustion andcloser emission characteristics District heating networks are commonly addressed in the literature as one of the most effective solutions for decreasing the and THC by emissions decreased, increased. variations combustion and radio. emission characteristics followed the increase of the however EGR rateNOx wereemission exactly the oppositeThe to the changeof ofthe hydrogen blending Considering both greenhouse gas emissions from the building sector. These systems require high investments which are returned through the heat followed by the increase of the EGR rate were exactly the opposite to the of hydrogen radio. Considering both the combustion and emission characteristics, using moderate EGR ratechange (15%~20%) underblending high hydrogen blending radio sales. Due to the changed climate conditions and building renovation policies, heat demand in the future could decrease, the combustion and emission using moderate of EGR rate (15%~20%) under high hydrogen blending radio (15%~20%) condition can realizecharacteristics, the simultaneous improvement combustion and emission performance. prolonging the investment return period. (15%~20%) condition can realize the simultaneous improvement of combustion and emission performance. The main scope of this paper is to assess the feasibility of using the heat demand – outdoor temperature function for heat demand Copyright © 2018 Elsevier Ltd. All rights reserved. forecast. The districtPublished of Alvalade, locatedLtd. in Lisbon (Portugal), was used as a caseth study. The district is consisted of 665 © 2019 The by Elsevier Copyright ©Authors. 2018 Elsevier Ltd. Allresponsibility rights reserved. Selection and peer-review under of the scientific committee of the 10 International Conference on Applied This is an open the CC period BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/) buildings that access vary inarticle both under construction and typology. Three weather scenarios (low, medium, high) and three district Selection and peer-review under responsibility of the scientific committee of the 10th International Conference on Applied Energy (ICAE2018). Peer-review responsibility of the scientific of ICAE2018 The 10th the International Conference on Applied Energy. renovation under scenarios were developed (shallow,committee intermediate, deep). To– estimate error, obtained heat demand values were Energy (ICAE2018). compared with results from a dynamic heat demand model, previously developed and validated by the authors. Keywords: Direct-injection; Hydrogen; Exhaust Gas Recirculation; Combustion characteristics; Emission characteristics The results showed that when only weather change is considered, the margin of error could be acceptable for some applications Keywords: Direct-injection; Hydrogen; Exhaust Gas Recirculation; Combustion characteristics; Emission characteristics (the error in annual demand was lower than 20% for all weather scenarios considered). However, after introducing renovation scenarios, the error value increased up to 59.5% (depending on the weather and renovation scenarios combination considered). 1.The Introduction value of slope coefficient increased on average within the range of 3.8% up to 8% per decade, that corresponds to the 1. Introduction decrease in the number of heating hours of 22-139h during the heating season (depending on the combination of weather and The rapidscenarios development of theOn automobile industry has brought a number of problems, such (depending as fossil energy renovation considered). the other hand, function interceptabout increased for 7.8-12.7% per decade on the The rapid of pollution the automobile has brought about a number problems, such as fossiltoenergy depletion anddevelopment environmental aggravation. Hydrogen is the recognized as the of most ideal energy solve coupled scenarios). The values suggested couldindustry be used to modify function parameters for the vehicle scenarios considered, and depletion andaccuracy pollution aggravation. Hydrogen is recognized idealsources, vehicle energy to solve the shortage ofenvironmental energy and reduce greenhouse gas emissions becauseas ofthe its most extensive high efficiency improve the of supply heat demand estimations.
the shortage of energy supply and reduce greenhouse gas emissions because of its extensive sources, high efficiency © 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.
* Corresponding author. Tel.: +86-0431-8509 5897; fax: +86-0431-8509 5127. * E-mail Corresponding Tel.: +86-0431-8509 5897; fax: +86-0431-8509 5127. address:author. [email protected] Keywords: Heat demand; Forecast; Climate change E-mail address: [email protected] 1876-6102 Copyright © 2018 Elsevier Ltd. All rights reserved. 1876-6102 Copyright © 2018 Elsevier Ltd. All of rights reserved. committee of the 10th International Conference on Applied Energy (ICAE2018). Selection and peer-review under responsibility the scientific Selection and peer-review under responsibility of the scientific committee of the 10th International Conference on Applied Energy (ICAE2018). 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 (http://creativecommons.org/licenses/by-nc-nd/4.0/) Peer-review under responsibility of the scientific committee of ICAE2018 – The 10th International Conference on Applied Energy. 10.1016/j.egypro.2019.01.348
Lv He et al. / Energy Procedia 158 (2019) 1449–1454 Author name / Energy Procedia 00 (2018) 000–000
1450 2
and cleanliness [1]. Lucas et al. [2] investigated that the fuel economy of gasoline engine after hydrogen blending was improved. The strategy of using gasoline and hydrogen mixture under partial load and using pure gasoline at full load could meet the demand of burning rate and power output. Zhao et al. [3] studied the emission characteristics of hydrogen gasoline duel fuel engine. The research showed that the addition of hydrogen could reduce the in-cylinder particulate emissions generation in whole operation condition. Ceviz et al. [4] found that with the increase of hydrogen blending ratio, the thermal efficiency increased, and the maximum in-cylinder temperature increased. Besides, the THC (Total Hydrocarbons) emission reduced, while the NOx (Nitrogen Oxide) emission increased. In order to reduce the excessive NOx emission, the method of EGR (Exhaust Gas Recirculation) is widely used. Recycling exhaust gases into the cylinder could increase the capacity of mixture fraction further decrease the incylinder combustion temperature resulting in the reduction of NOx emission [5-6]. Therefore, this paper used CFD technology to study the effects of hydrogen blending radio and EGR rate on combustion and emission characteristics of a PFI (Port Fuel Injection) gasoline engine with hydrogen direct-injection. Results showed that compared with original engine, hydrogen direct-injection PFI gasoline engine had a better performance on combustion characteristics, but it also had a disadvantage of increasing NOx emissions. With the increase of hydrogen blending radio, combustion duration was shortened and the crank angle of the combustion center (CA50) advanced and was closer to TDC. And CO and THC emissions decreased, NOx emission increased nevertheless. The variations effect of EGR on combustion and emission characteristics followed by the increase of the EGR rate were as exactly the opposite of to the change of hydrogen blending radio. Considering both combustion characteristics and emission characteristics, using moderate EGR rate (15%~20%) exhaust gas recirculation methods under high hydrogen blending radio （15%~20%）condition can realize the simultaneous improvement of combustion and emission performance. 2. Three Dimensional Numerical Simulation Analysis 2.1. Engine specifications The specifications of hydrogen direct-injection PFI gasoline engine are shown in Table 1. Hydrogen was directly injected into the cylinder from the nozzle while gasoline was injected into the intake port. Intake valve opening timing was 381°CA BTDC, and closing timing was 119°CA BTDC. Exhaust valve opening timing was 139°CA ATDC. Table 1. Engine specification. Type
4 cylinder inline
Bore
82.5mm
Stroke
84.2mm
Connecting rod
147mm
Piston displacement
1.8L
Compression ratio
9.6:1
Holes num./nozzle diam.
6/0.18mm
2.2. Numerical model In order to analyze the whole process of intake, fuel-air mixing, combustion and exhaust, a three-dimensional computation zone including intake port, exhaust port, intake valves, exhaust valves and cylinder was established using an innovative thermal fluid analysis software CONVERGE as shown in Figure 1. The maximum of calculation grid in this study was 1.2 million. Calculations were carried out from intake valve open timing to exhaust value opening timing. For initial conditions and boundary conditions setting, intake port initial temperature was 363K, intake port initial pressure was 101325 Pa, cylinder initial temperature was 363K, cylinder initial pressure
Lv He et al. / Energy Procedia 158 (2019) 1449–1454 Author name / Energy Procedia 00 (2018) 000–000
1451 3
was 101325 Pa, piston head temperature was 550K, cylinder wall temperature was 450K and cylinder head temperature was 450K.
(a) Three-dimensional computation zone
(b) Defined boundary
(c) Sectional view of dynamic mesh model Fig. 1. Single cylinder model
The numerical models for simulation included turbulence model, wall heat transfer model, ignition model, combustion model and emission model as shown in Table 2. SAGE detailed chemistry reaction model is used to simulate the combustion process, and the flame propagation process can be accurately simulated by adaptive mesh refinement. For hydrogen injection simulation, six inflow boundaries were added into the geometric model as spray holes of hydrogen injector. The injection amount of hydrogen and injection timing were regulated by the velocity and pressure of the nozzle. The combustion mechanism used in this paper is a combination of skeleton chemical reaction mechanism of isooctane, n-heptane and toluene mixed fuel (48 components, 152 reactions) proposed by Liu et al. [7] and detailed chemical reaction mechanism of hydrogen in Lawrence Livermore National Laboratory (10 components, 21 reactions) [8]. Table 2. Sub-model group. Turbulence model
RNG k-ε Model
Wall heat transfer model
O’Rourke and Amsden Model
Ignition model
Spark-energy Deposition Model
Combustion model
SAGE Model
NOx formation model
Extended Zeldovich Model
As shown in Figure 2, the simulation data of cylinder pressure showed the same tendency as compared with the experimental data. And Figure 3 showed that the simulation errors of main emission were less than 10%. Results showed that the model parameters were reasonable and the three-dimensional model was available.
Lv He et al. / Energy Procedia 158 (2019) 1449–1454 Author name / Energy Procedia 00 (2018) 000–000
1452 4
20
7000 Cylinder Pressure (kPa)
6000
-100
16
Meas.
5000
Mass (mg)
4000 3000 2000 1000 -80
-60
-40
-20
0
Calc. Meas.
Calc.
12 8 4
0
20
40
60
80
100
Crank Angle (℃A ATDC)
Fig. 2. Cylinder pressure comparison of calc. and meas.
0
NOx
CO×10
THC×10 4
Fig. 3. Emission mass comparison of calc. and meas.
2.3. Simulation conditions In this simulation process, in order to avoid the difference of input energy between different condition models caused by the different calorific value of gasoline and hydrogen, the input energy was set as a fixed value. The hydrogen blending radio was defined as the ratio of hydrogen heat to total heat. The operation conditions have been given in Table 3. The injection timing was 105°CA BTDC and the ignition timing was 11°CA BTDC. The operation conditions for this study were fixed at engine speed of 1500rpm and stoichiometric ratio. Table 3. Calculation operation conditions. Variable
Values
Engine speed (1/min)
1500
Hydrogen blending radio (%)
0,5.10,15,20
EGR rate (%)
0,5,10,15,20
Hydrogen injection pressure (bar)
150
Hydrogen injection timing (°CA BTDC)
105
Spark timing (°CA BTDC)
11
3. Results and discussion 3.1. Effect of hydrogen blending radio and EGR rate on combustion characteristics In this section, combustion duration (crank angles from CA10 to CA90) and CA50 (crank angle when the accumulated heat release reached 50% of the total heat release) were used to describe the combustion characteristics. Figure 4(a) shows the effects of hydrogen blending radio and EGR rate on combustion duration. It was obvious that as hydrogen blending radio increase, combustion duration decreased and with the increase of EGR rate, combustion duration increased. Besides, with the increase of hydrogen blending radio, combustion duration decreased rapidly as the hydrogen blending radio was in the range of 0~5%. After hydrogen blending radio was greater than 5%, the decreasing rate of the combustion duration slowed down. In comparison, the effect of hydrogen ratio on the duration of combustion was more obvious. Figure 4(b) shows the effects of hydrogen blending radio and ERG rate on CA50. It could be seen that the variation trend of CA50 with hydrogen blending ratio and EGR rate was the same as combustion duration. When hydrogen blending ratio is increased from 0 to 5%, the decrease of CA50 was the most obvious.
Lv He et al. / Energy Procedia 158 (2019) 1449–1454 Author name / Energy Procedia 00 (2018) 000–000
1453 5
As hydrogen blending radio increased, the amount of hydrogen distributed around the spark plug increased resulting in rapid heat release after spark ignition. Therefore, combustion duration was shortened and CA50 was advanced. Increasing the EGR rate reduced the flame speed resulting in the increase of the combustion duration and the retard of CA50.
(a) Combustion duration
(b) CA50
Fig. 4. Effect of hydrogen blending radio and EGR rate on combustion characteristics
3.2. Effect of hydrogen blending radio and EGR rate on emission characteristics In this section, effects of hydrogen blending radio and EGR rate on three major emissions were analyzed. Figure 5(a) shows the effects of hydrogen blending radio and EGR rate on NOx emission. It can be seen that NOx emission increased obviously with the increase of hydrogen blending ratio. With EGR rate increasing, NOx emission was substantially reduced. NOx emission decreased faster with the increase of EGR ratio at high hydrogen ratio.
(a) NOx emission
(b) CO emission
(c) THC emission
Fig. 5. Effect of hydrogen blending radio and EGR rate on emission characteristics
Effects of hydrogen blending radio and EGR rate on CO emission are shown in figure 5(b). With the increase of hydrogen blending ratio, CO emission reduced. On the one hand, with the increase of hydrogen blending radio, the amount of gasoline was reduced; on the other hand, combustion temperature also raised , which resulted more CO was oxidized. With the increase of the EGR rate, CO emission increased because of the deterioration of combustion. Figure 5(c) shows the effects of hydrogen blending radio and EGR rate on THC emission. It could be seen that when hydrogen blending ratio increased from 0 to 5%, THC emissions decreased significantly. With futher increase of the hydrogen blending ratio, THC emission decreased, but the decreasing amplitude was very limited. THC emission increased as the increase of EGR rate under different hydrogen blending radio.
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Lv He et al. / Energy Procedia 158 (2019) 1449–1454 Author name / Energy Procedia 00 (2018) 000–000
4. Conclusions 1. With the increase of hydrogen blending radio, the combustion characteristics improved, combustion duration shortened and the CA 50 advanced to TDC. The effect of EGR on combustion characteristics was exactly the opposite of hydrogen blending radio. With the increase of EGR rate, combustion duration prolonged and CA50 was retarded. 2. Hydrogen blending radio had a great influence on NOx emission. With the increase of hydrogen, NOx emission increased rapidly, which could be solved by increase the EGR rate. With the increase of hydrogen blending ratio, CO emission and THC emission reduced slightly. Nevertheless, CO and THC emission increased with the increase of EGR rate under either hydrogen blending radio. 3. Compared with original engine, hydrogen direct-injection PFI gasoline engine had a better performance on combustion characteristics, but it also had a disadvantage of increasing NOx emissions. Considering both the combustion characteristics and emission characteristics, using moderate EGR rate (15%~20%) under high hydrogen blending radio (15%~20%) condition can realize the simultaneous improvement of combustion and emission performance. Acknowledgements This work was supported by National Natural Science Foundation of China (No. 51276079). References [1] White C, Steeper R, Lutz A. The hydrogen -fueled internal combustion engine: A technical review [J]. International Journal of Hydrogen Energy, 2006.31(10): 1292-1305. [2] Lucas G. The hydrogen/petrol engine-the means to give good part-load thermal efficiency [J]. SAE Paper, 1982. (8)20315.27-42. [3] Zhao HY, Stone R, Zhou L. Analysis of the particulate emissions and combustion performance of a direct injection spark ignition engine using hydrogen and gasoline mixtures[J].International Journal of Hydrogen Energy,2010.35(10): 4676-4686. [4] Ceviz M, Sen A, Küleri A, et al. Engine performance, exhaust emissions, and cyclic variations in a lean-burn SI engine fueled by gasolinehydrogen blends[J]. Applied Thermal Engineering,2012.36: 314-324. [5] G.H. Abd-Alla. Using exhaust gas recirculation in internal combustion engines: a review[J]. Engine Conversion and Management, 2002,43: 1027-1042. [6] Seyfi Polat, Ahmet Uyumaz, et al. A numerical study on the effects of EGR and spark timing to combustion characteristics and NOx emission of a GDI engine [J]. International Journal of Green Energy, 13:1,63-70, DOI: 10.1080/15435075.2014.909361. [7] Liu Y D, Jia M, Xie M Z. et al. Enhancement on a skeletal kinetic model for primary reference fuel oxidation by using a semidecoupling methodology[J]. Energy & Fuel, 2012. 26(12): 7069-7083. [8] http://www-cms.llnl.gov/combustion/archive.html
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Energy Procedia 158 Energy Procedia 00(2019) (2017)1449–1454 000–000 www.elsevier.com/locate/procedia
10th th
International Conference on Applied Energy (ICAE2018), 22-25 August 2018, Hong Kong, 10 International Conference on Applied Energy China(ICAE2018), 22-25 August 2018, Hong Kong, China
Numerical Study on Combustion and Emission Characteristics of a 15th International Symposium on Emission District Heating and Cooling Numerical The Study on Combustion and Characteristics of a PFI Gasoline Engine with Hydrogen Direct-Injection PFI Gasoline Engine with Hydrogen Direct-Injection Assessing the feasibility of using the heat demand-outdoor Lv Heaa, Li Jingyuanaa ,Yu Xiuminb,b,*, Li Mengliangaa , Yang Tianaa Lv He function , Li Jingyuan Xiumin *, Lidistrict Mengliang , Yang Tian forecast temperature for,Yu a long-term heat demand China Automotive Technology and Research Center Co.,Ltd., Xianfeng Dong Road, Dongli District,Tianjin 300300, China a
b China Automotive Research Center Co.,Ltd., XianfengTianjin Dong Road, DongliTianjin District,Tianjin 300300, China State KeyTechnology Laboratoryand of Automotive Simulation anf Control, University, 130022, China a,b,c a a b c c b State Key Laboratory of Automotive Simulation anf Control, Tianjin University, Tianjin 130022, China
a
I. Andrić
*, A. Pina , P. Ferrão , J. Fournier ., B. Lacarrière , O. Le Corre
a
IN+ Center for Innovation, Technology and Policy Research - Instituto Superior Técnico, Av. Rovisco Pais 1, 1049-001 Lisbon, Portugal Abstract b Veolia Recherche & Innovation, 291 Avenue Dreyfous Daniel, 78520 Limay, France Abstract c Département Systèmes Énergétiques Environnement - IMT 4 rueand Alfred Kastler,characteristics 44300 Nantes, France In this paper, the effects of hydrogen blending etradio and EGR rate onAtlantique, combustion emission of a PFI gasoline In this paper, the effects of hydrogen blending radio and EGR rate on combustion and emission characteristics of a PFI gasoline engine with hydrogen direct-injection have been investigated by numerical modeling methods using a new generation of CFD engine withsoftware hydrogen direct-injection have showed been investigated by numerical modeling methods using a new generation of CFD simulation CONVERGE. Results that compared with original engine, hydrogen direct-injection PFI gasoline simulation CONVERGE. showed that compared engine, hydrogen direct-injection PFI gasoline engine had software a better performance on Results combustion characteristics, but itwith alsooriginal had a disadvantage of increasing NOx emissions. With Abstract engine had a of better performance on radio, combustion characteristics, it also and had aCA50 disadvantage increasing NOxtoemissions. the increase hydrogen blending combustion duration but shortened advancedofand was closer TDC. AndWith CO the increase of hydrogen blending radio,NOx combustion shortened and CA50 advanced and was to TDC. And CO and THC emissions decreased, however emissionduration increased. The variations of the combustion andcloser emission characteristics District heating networks are commonly addressed in the literature as one of the most effective solutions for decreasing the and THC by emissions decreased, increased. variations combustion and radio. emission characteristics followed the increase of the however EGR rateNOx wereemission exactly the oppositeThe to the changeof ofthe hydrogen blending Considering both greenhouse gas emissions from the building sector. These systems require high investments which are returned through the heat followed by the increase of the EGR rate were exactly the opposite to the of hydrogen radio. Considering both the combustion and emission characteristics, using moderate EGR ratechange (15%~20%) underblending high hydrogen blending radio sales. Due to the changed climate conditions and building renovation policies, heat demand in the future could decrease, the combustion and emission using moderate of EGR rate (15%~20%) under high hydrogen blending radio (15%~20%) condition can realizecharacteristics, the simultaneous improvement combustion and emission performance. prolonging the investment return period. (15%~20%) condition can realize the simultaneous improvement of combustion and emission performance. The main scope of this paper is to assess the feasibility of using the heat demand – outdoor temperature function for heat demand Copyright © 2018 Elsevier Ltd. All rights reserved. forecast. The districtPublished of Alvalade, locatedLtd. in Lisbon (Portugal), was used as a caseth study. The district is consisted of 665 © 2019 The by Elsevier Copyright ©Authors. 2018 Elsevier Ltd. Allresponsibility rights reserved. Selection and peer-review under of the scientific committee of the 10 International Conference on Applied This is an open the CC period BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/) buildings that access vary inarticle both under construction and typology. Three weather scenarios (low, medium, high) and three district Selection and peer-review under responsibility of the scientific committee of the 10th International Conference on Applied Energy (ICAE2018). Peer-review responsibility of the scientific of ICAE2018 The 10th the International Conference on Applied Energy. renovation under scenarios were developed (shallow,committee intermediate, deep). To– estimate error, obtained heat demand values were Energy (ICAE2018). compared with results from a dynamic heat demand model, previously developed and validated by the authors. Keywords: Direct-injection; Hydrogen; Exhaust Gas Recirculation; Combustion characteristics; Emission characteristics The results showed that when only weather change is considered, the margin of error could be acceptable for some applications Keywords: Direct-injection; Hydrogen; Exhaust Gas Recirculation; Combustion characteristics; Emission characteristics (the error in annual demand was lower than 20% for all weather scenarios considered). However, after introducing renovation scenarios, the error value increased up to 59.5% (depending on the weather and renovation scenarios combination considered). 1.The Introduction value of slope coefficient increased on average within the range of 3.8% up to 8% per decade, that corresponds to the 1. Introduction decrease in the number of heating hours of 22-139h during the heating season (depending on the combination of weather and The rapidscenarios development of theOn automobile industry has brought a number of problems, such (depending as fossil energy renovation considered). the other hand, function interceptabout increased for 7.8-12.7% per decade on the The rapid of pollution the automobile has brought about a number problems, such as fossiltoenergy depletion anddevelopment environmental aggravation. Hydrogen is the recognized as the of most ideal energy solve coupled scenarios). The values suggested couldindustry be used to modify function parameters for the vehicle scenarios considered, and depletion andaccuracy pollution aggravation. Hydrogen is recognized idealsources, vehicle energy to solve the shortage ofenvironmental energy and reduce greenhouse gas emissions becauseas ofthe its most extensive high efficiency improve the of supply heat demand estimations.
the shortage of energy supply and reduce greenhouse gas emissions because of its extensive sources, high efficiency © 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.
* Corresponding author. Tel.: +86-0431-8509 5897; fax: +86-0431-8509 5127. * E-mail Corresponding Tel.: +86-0431-8509 5897; fax: +86-0431-8509 5127. address:author. [email protected] Keywords: Heat demand; Forecast; Climate change E-mail address: [email protected] 1876-6102 Copyright © 2018 Elsevier Ltd. All rights reserved. 1876-6102 Copyright © 2018 Elsevier Ltd. All of rights reserved. committee of the 10th International Conference on Applied Energy (ICAE2018). Selection and peer-review under responsibility the scientific Selection and peer-review under responsibility of the scientific committee of the 10th International Conference on Applied Energy (ICAE2018). 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 (http://creativecommons.org/licenses/by-nc-nd/4.0/) Peer-review under responsibility of the scientific committee of ICAE2018 – The 10th International Conference on Applied Energy. 10.1016/j.egypro.2019.01.348
Lv He et al. / Energy Procedia 158 (2019) 1449–1454 Author name / Energy Procedia 00 (2018) 000–000
1450 2
and cleanliness [1]. Lucas et al. [2] investigated that the fuel economy of gasoline engine after hydrogen blending was improved. The strategy of using gasoline and hydrogen mixture under partial load and using pure gasoline at full load could meet the demand of burning rate and power output. Zhao et al. [3] studied the emission characteristics of hydrogen gasoline duel fuel engine. The research showed that the addition of hydrogen could reduce the in-cylinder particulate emissions generation in whole operation condition. Ceviz et al. [4] found that with the increase of hydrogen blending ratio, the thermal efficiency increased, and the maximum in-cylinder temperature increased. Besides, the THC (Total Hydrocarbons) emission reduced, while the NOx (Nitrogen Oxide) emission increased. In order to reduce the excessive NOx emission, the method of EGR (Exhaust Gas Recirculation) is widely used. Recycling exhaust gases into the cylinder could increase the capacity of mixture fraction further decrease the incylinder combustion temperature resulting in the reduction of NOx emission [5-6]. Therefore, this paper used CFD technology to study the effects of hydrogen blending radio and EGR rate on combustion and emission characteristics of a PFI (Port Fuel Injection) gasoline engine with hydrogen direct-injection. Results showed that compared with original engine, hydrogen direct-injection PFI gasoline engine had a better performance on combustion characteristics, but it also had a disadvantage of increasing NOx emissions. With the increase of hydrogen blending radio, combustion duration was shortened and the crank angle of the combustion center (CA50) advanced and was closer to TDC. And CO and THC emissions decreased, NOx emission increased nevertheless. The variations effect of EGR on combustion and emission characteristics followed by the increase of the EGR rate were as exactly the opposite of to the change of hydrogen blending radio. Considering both combustion characteristics and emission characteristics, using moderate EGR rate (15%~20%) exhaust gas recirculation methods under high hydrogen blending radio （15%~20%）condition can realize the simultaneous improvement of combustion and emission performance. 2. Three Dimensional Numerical Simulation Analysis 2.1. Engine specifications The specifications of hydrogen direct-injection PFI gasoline engine are shown in Table 1. Hydrogen was directly injected into the cylinder from the nozzle while gasoline was injected into the intake port. Intake valve opening timing was 381°CA BTDC, and closing timing was 119°CA BTDC. Exhaust valve opening timing was 139°CA ATDC. Table 1. Engine specification. Type
4 cylinder inline
Bore
82.5mm
Stroke
84.2mm
Connecting rod
147mm
Piston displacement
1.8L
Compression ratio
9.6:1
Holes num./nozzle diam.
6/0.18mm
2.2. Numerical model In order to analyze the whole process of intake, fuel-air mixing, combustion and exhaust, a three-dimensional computation zone including intake port, exhaust port, intake valves, exhaust valves and cylinder was established using an innovative thermal fluid analysis software CONVERGE as shown in Figure 1. The maximum of calculation grid in this study was 1.2 million. Calculations were carried out from intake valve open timing to exhaust value opening timing. For initial conditions and boundary conditions setting, intake port initial temperature was 363K, intake port initial pressure was 101325 Pa, cylinder initial temperature was 363K, cylinder initial pressure
Lv He et al. / Energy Procedia 158 (2019) 1449–1454 Author name / Energy Procedia 00 (2018) 000–000
1451 3
was 101325 Pa, piston head temperature was 550K, cylinder wall temperature was 450K and cylinder head temperature was 450K.
(a) Three-dimensional computation zone
(b) Defined boundary
(c) Sectional view of dynamic mesh model Fig. 1. Single cylinder model
The numerical models for simulation included turbulence model, wall heat transfer model, ignition model, combustion model and emission model as shown in Table 2. SAGE detailed chemistry reaction model is used to simulate the combustion process, and the flame propagation process can be accurately simulated by adaptive mesh refinement. For hydrogen injection simulation, six inflow boundaries were added into the geometric model as spray holes of hydrogen injector. The injection amount of hydrogen and injection timing were regulated by the velocity and pressure of the nozzle. The combustion mechanism used in this paper is a combination of skeleton chemical reaction mechanism of isooctane, n-heptane and toluene mixed fuel (48 components, 152 reactions) proposed by Liu et al. [7] and detailed chemical reaction mechanism of hydrogen in Lawrence Livermore National Laboratory (10 components, 21 reactions) [8]. Table 2. Sub-model group. Turbulence model
RNG k-ε Model
Wall heat transfer model
O’Rourke and Amsden Model
Ignition model
Spark-energy Deposition Model
Combustion model
SAGE Model
NOx formation model
Extended Zeldovich Model
As shown in Figure 2, the simulation data of cylinder pressure showed the same tendency as compared with the experimental data. And Figure 3 showed that the simulation errors of main emission were less than 10%. Results showed that the model parameters were reasonable and the three-dimensional model was available.
Lv He et al. / Energy Procedia 158 (2019) 1449–1454 Author name / Energy Procedia 00 (2018) 000–000
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20
7000 Cylinder Pressure (kPa)
6000
-100
16
Meas.
5000
Mass (mg)
4000 3000 2000 1000 -80
-60
-40
-20
0
Calc. Meas.
Calc.
12 8 4
0
20
40
60
80
100
Crank Angle (℃A ATDC)
Fig. 2. Cylinder pressure comparison of calc. and meas.
0
NOx
CO×10
THC×10 4
Fig. 3. Emission mass comparison of calc. and meas.
2.3. Simulation conditions In this simulation process, in order to avoid the difference of input energy between different condition models caused by the different calorific value of gasoline and hydrogen, the input energy was set as a fixed value. The hydrogen blending radio was defined as the ratio of hydrogen heat to total heat. The operation conditions have been given in Table 3. The injection timing was 105°CA BTDC and the ignition timing was 11°CA BTDC. The operation conditions for this study were fixed at engine speed of 1500rpm and stoichiometric ratio. Table 3. Calculation operation conditions. Variable
Values
Engine speed (1/min)
1500
Hydrogen blending radio (%)
0,5.10,15,20
EGR rate (%)
0,5,10,15,20
Hydrogen injection pressure (bar)
150
Hydrogen injection timing (°CA BTDC)
105
Spark timing (°CA BTDC)
11
3. Results and discussion 3.1. Effect of hydrogen blending radio and EGR rate on combustion characteristics In this section, combustion duration (crank angles from CA10 to CA90) and CA50 (crank angle when the accumulated heat release reached 50% of the total heat release) were used to describe the combustion characteristics. Figure 4(a) shows the effects of hydrogen blending radio and EGR rate on combustion duration. It was obvious that as hydrogen blending radio increase, combustion duration decreased and with the increase of EGR rate, combustion duration increased. Besides, with the increase of hydrogen blending radio, combustion duration decreased rapidly as the hydrogen blending radio was in the range of 0~5%. After hydrogen blending radio was greater than 5%, the decreasing rate of the combustion duration slowed down. In comparison, the effect of hydrogen ratio on the duration of combustion was more obvious. Figure 4(b) shows the effects of hydrogen blending radio and ERG rate on CA50. It could be seen that the variation trend of CA50 with hydrogen blending ratio and EGR rate was the same as combustion duration. When hydrogen blending ratio is increased from 0 to 5%, the decrease of CA50 was the most obvious.
Lv He et al. / Energy Procedia 158 (2019) 1449–1454 Author name / Energy Procedia 00 (2018) 000–000
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As hydrogen blending radio increased, the amount of hydrogen distributed around the spark plug increased resulting in rapid heat release after spark ignition. Therefore, combustion duration was shortened and CA50 was advanced. Increasing the EGR rate reduced the flame speed resulting in the increase of the combustion duration and the retard of CA50.
(a) Combustion duration
(b) CA50
Fig. 4. Effect of hydrogen blending radio and EGR rate on combustion characteristics
3.2. Effect of hydrogen blending radio and EGR rate on emission characteristics In this section, effects of hydrogen blending radio and EGR rate on three major emissions were analyzed. Figure 5(a) shows the effects of hydrogen blending radio and EGR rate on NOx emission. It can be seen that NOx emission increased obviously with the increase of hydrogen blending ratio. With EGR rate increasing, NOx emission was substantially reduced. NOx emission decreased faster with the increase of EGR ratio at high hydrogen ratio.
(a) NOx emission
(b) CO emission
(c) THC emission
Fig. 5. Effect of hydrogen blending radio and EGR rate on emission characteristics
Effects of hydrogen blending radio and EGR rate on CO emission are shown in figure 5(b). With the increase of hydrogen blending ratio, CO emission reduced. On the one hand, with the increase of hydrogen blending radio, the amount of gasoline was reduced; on the other hand, combustion temperature also raised , which resulted more CO was oxidized. With the increase of the EGR rate, CO emission increased because of the deterioration of combustion. Figure 5(c) shows the effects of hydrogen blending radio and EGR rate on THC emission. It could be seen that when hydrogen blending ratio increased from 0 to 5%, THC emissions decreased significantly. With futher increase of the hydrogen blending ratio, THC emission decreased, but the decreasing amplitude was very limited. THC emission increased as the increase of EGR rate under different hydrogen blending radio.
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Lv He et al. / Energy Procedia 158 (2019) 1449–1454 Author name / Energy Procedia 00 (2018) 000–000
4. Conclusions 1. With the increase of hydrogen blending radio, the combustion characteristics improved, combustion duration shortened and the CA 50 advanced to TDC. The effect of EGR on combustion characteristics was exactly the opposite of hydrogen blending radio. With the increase of EGR rate, combustion duration prolonged and CA50 was retarded. 2. Hydrogen blending radio had a great influence on NOx emission. With the increase of hydrogen, NOx emission increased rapidly, which could be solved by increase the EGR rate. With the increase of hydrogen blending ratio, CO emission and THC emission reduced slightly. Nevertheless, CO and THC emission increased with the increase of EGR rate under either hydrogen blending radio. 3. Compared with original engine, hydrogen direct-injection PFI gasoline engine had a better performance on combustion characteristics, but it also had a disadvantage of increasing NOx emissions. Considering both the combustion characteristics and emission characteristics, using moderate EGR rate (15%~20%) under high hydrogen blending radio (15%~20%) condition can realize the simultaneous improvement of combustion and emission performance. Acknowledgements This work was supported by National Natural Science Foundation of China (No. 51276079). References [1] White C, Steeper R, Lutz A. The hydrogen -fueled internal combustion engine: A technical review [J]. International Journal of Hydrogen Energy, 2006.31(10): 1292-1305. [2] Lucas G. The hydrogen/petrol engine-the means to give good part-load thermal efficiency [J]. SAE Paper, 1982. (8)20315.27-42. [3] Zhao HY, Stone R, Zhou L. Analysis of the particulate emissions and combustion performance of a direct injection spark ignition engine using hydrogen and gasoline mixtures[J].International Journal of Hydrogen Energy,2010.35(10): 4676-4686. [4] Ceviz M, Sen A, Küleri A, et al. Engine performance, exhaust emissions, and cyclic variations in a lean-burn SI engine fueled by gasolinehydrogen blends[J]. Applied Thermal Engineering,2012.36: 314-324. [5] G.H. Abd-Alla. Using exhaust gas recirculation in internal combustion engines: a review[J]. Engine Conversion and Management, 2002,43: 1027-1042. [6] Seyfi Polat, Ahmet Uyumaz, et al. A numerical study on the effects of EGR and spark timing to combustion characteristics and NOx emission of a GDI engine [J]. International Journal of Green Energy, 13:1,63-70, DOI: 10.1080/15435075.2014.909361. [7] Liu Y D, Jia M, Xie M Z. et al. Enhancement on a skeletal kinetic model for primary reference fuel oxidation by using a semidecoupling methodology[J]. Energy & Fuel, 2012. 26(12): 7069-7083. [8] http://www-cms.llnl.gov/combustion/archive.html