Coefficient of richness and combustion efficiency in opposed-piston engines
-
摘要:
针对空气利用率用于描述对置活塞（OP2S）二冲程压燃式发动机油气相互作用规律时局限性较大的问题，给出过浓系数的定义并以之作为对置活塞二冲程压燃式发动机缸内油气混合效果的评价指标。在此基础上通过基于CONVERGE软件的数值模拟研究了初始涡流比和喷油器倾角对OP2S燃烧效率的影响规律。结果表明：过浓系数可以排除平均当量比的影响并有效反映喷油参数对油气混合效果的影响。提高涡流比可以强化喷油过程中的油气混合，同时改变喷油过程形成的燃油径向分布。过小或过大的涡流比使燃油过度集中于气缸轴线附近或气缸壁附近，造成局部过浓，喷油结束后的燃烧效率下降。整个循环的燃烧效率由喷油过程中及喷油结束后的燃烧放热过程共同决定。在所研究的范围内，涡流比对燃油径向分布的影响可以使燃烧效率在0.6～1.0的范围内变化。喷油器倾角同样可以改变燃油径向分布位置及燃烧效率，且这一影响可以与涡流对燃油径向分布规律的影响相叠加。
-
关键词:
- 对置活塞（OP2S） /
- 燃烧效率 /
- 过浓系数 /
- 涡流比 /
- 油气混合
Abstract:Opposed-piston 2-stroke (OP2S) compress ignition engines have different fuel-air interactions compared with ordinary CI engines, while air utilization has proved inadequate in measuring fuel-air mixing in CI engines. In this study, the concept of coefficient of richness was proposed as an index of fuel-air mixing in OP2S engines to replace air utilization. Numerical simulation was carried out with CONVERGE software to study the effect of swirl ratio and injector yaw on combustion efficiency in OP2S-CI. Results showed that the coefficient of richness was effective in representing fuel-air mixing regardless of average equivalence ratio. Larger swirl ratio could improve fuel-air mixing during injection while affecting radial distribution of fuel at end of injection. Fuel concentration near either cylinder axis or cylinder wall could hinder fuel-air mixing after injection, decreasing combustion efficiency. Combustion efficiency could vary between the range 0.6 and 1.0 of swirl ratio. Injector yaw may also impact radial distribution of fuel and in turn the combustion efficiency. This effect was taken into account jointly with that from swirl.
-
图 2 单元尺寸为1.4～4 mm的计算结果对比
Figure 2. Comparison of calculation results from cell size 1.4−4 mm
图 4 计算结束时刻总过浓系数、空气利用率与燃烧效率的关系
Figure 4. Correlation between total coefficient of richness, air utilization and combustion efficiency at end of simulation
图 5 喷油器布置对总过浓系数变化规律的影响
Figure 5. Effect of nozzle layout on trend of total coefficient of richness
图 8 涡流比对总过浓系数变化规律的影响
Figure 8. Effect of swirl ratio on trend of total coefficient of richness
图 9 涡流比对瞬时放热率及燃烧效率变化规律的影响
Figure 9. Effect of swirl ratio on trend of heat release rate and combustion efficiency
图 10 涡流比对曲轴转角为8°（上止点后）时缸内y方向速度分布的影响
Figure 10. Effect of swirl ratio on y-velocity distribution at 8° crank angle after TDC （ATDC）
图 11 涡流比对曲轴转角为16°（上止点后）时缸内当量比分布的影响
Figure 11. Effect of swirl ratio on equivalence ratio distribution at 16° crank angle （ATDC）
图 12 涡流比对曲轴转角为100°（上止点后）时缸内过浓系数的径向分布的影响
Figure 12. Effect of swirl ratio on radial distribution of coefficient of richness at 100° crank angle （ATDC）
图 13 涡流比对燃烧效率的影响机理
Figure 13. Mechanism of swirl ratio’s effect on combustion efficiency
图 15 22.5°喷油器倾角下涡流比对总过浓系数变化规律的影响
Figure 15. Effect of swirl ratio on trend of total coefficient of richness at injector yaw 22.5°
图 16 22.5°喷油器倾角下涡流比对曲轴转角为8°（上止点后）时缸内y方向速度分布的影响
Figure 16. Effect of swirl ratio on y-velocity distribution at 8° crank angle （ATDC） and injector yaw 22.5°
图 17 22.5°喷油器倾角下涡流比对曲轴转角为16°（上止点后）时缸内当量比分布的影响
Figure 17. Effect of swirl ratio on equivalence ratio distribution at 16° crank angle （ATDC） and injector yaw 22.5°
图 18 22.5°喷油器倾角下涡流比对曲轴转角为100°（上止点后）时缸内过浓系数的径向分布的影响
Figure 18. Effect of swirl ratio on radial distribution of coefficient of richness at 100° crank angle （ATDC）and injector yaw 22.5°
表 1 仿真的初始条件及其他参数
Table 1. Initiation condition and other parameters of simulation
参数 数值及说明 上止点后曲轴转角
（计算起止点）/（°）−110～100 初始压力/MPa 0.37 初始温度/K 400 循环充气量/mg 4320 初始成分质量分数/% 21（O2） 79（N2） 喷油压力/MPa 177 喷孔直径/mm 0.142 曲轴转角（喷油持续期）/（°） 31.5 上止点后曲轴转角
（喷油起始时刻）/（°）−15 燃油模型 DIESEL2 气缸壁温度/K 400 进、排气活塞顶温度/K 450 
下载: 导出CSV
-
[1] 卢东亮,郑君,胡崇波,等. 通用航空活塞发动机的发展现状研究[J]. 内燃机与配件,2019(8): 64-66.LU Dongliang,ZHENG Jun,HU Chongbo,et al. Research on development status of general aviation piston engine[J]. Internal Combustion Engine & Parts,2019(8): 64-66. (in Chinese) [2] 郑君. 通用航空活塞发动机现状及发展趋势探讨[J]. 内燃机与配件,2020(19): 196-198.ZHENG Jun. Discussion on the present situation and development trend of general aviation piston engine[J]. Internal Combustion Engine and Parts,2020(19): 196-198. (in Chinese) [3] 丁水汀,宋越,杜发荣,等. 航空重油活塞发动机发展趋势及关键技术分析[J]. 航空动力学报,2021,36(6): 1121-1136.DING Shuiting,SONG Yue,DU Farong,et al. Analysis on development trend and key technology of aircraft heavy fuel piston engine[J]. Journal of Aerospace Power,2021,36(6): 1121-1136. (in Chinese) [4] PIRAULT J P, FLINT M. Opposed piston engines: evolution, use, and future applications[R]. Warrendale, US: SAE International, 2010. [5] KALKSTEIN J, RÖVER W, CAMPBELL B, et al. Opposed piston opposed cylinder (opoc™) 5/10 kW heavy fuel engine for UAVs and APUs[R]. Warrendale, US: SAE International, 2006. [6] HOFBAUER P. Opposed piston opposed cylinder (opoc) engine for military ground vehicles[R]. Warrendale, US: SAE International, 2005. [7] FRANKE M, HUANG Hua, LIU Jing, et al. Opposed piston opposed cylinder (opoc™) 450 hp engine: performance development by CAE simulations and testing[R]. Warrendale, US: SAE International, 2006. [8] 许汉君,宋金瓯,姚春德,等. 对置二冲程柴油机缸内流动形式对混合气形成及燃烧的模拟研究[J]. 内燃机学报,2009,27(5): 395-400.XU Hanjun,SONG Jinou,YAO Chunde,et al. Simulation on In-cylinder flow on mixture formation and combustion in OPOC engine[J]. Transactions of CSICE,2009,27(5): 395-400. (in Chinese) [9] ZHANG Zhenyu,ZHAO Changlu,XIE Zhaoyi,et al. Study on the effect of the nozzle diameter and swirl ratio on the combustion process for an opposed-piston two-stroke diesel engine[J]. Energy Procedia,2014,61: 542-546. doi: 10.1016/j.egypro.2014.11.1166 [10] 郭勇,续彦芳. 双对置二冲程柴油机不同扫气口结构对燃烧过程的影响[J]. 内燃机,2016(1): 13-16.GUO Yong,XU Yanfang. Influence of different scanvenging port structure on combustion process in opposed piston opposed cylinder two stroke diesel engine[J]. Internal Combustion Engines,2016(1): 13-16. (in Chinese) [11] ZHANG Zhenyu,ZHANG Peng. Cross-impingement and combustion of sprays in high-pressure chamber and opposed-piston compression ignition engine[J]. Applied Thermal Engineering,2018,144: 137-146. doi: 10.1016/j.applthermaleng.2018.08.038 [12] ZHAO Zhenfeng, WU Dan, ZHANG Fujun, et al. Design and performance simulation of opposed-piston folded-cranktrain engines[R]. Warrendale, US: SAE International, 2014. [13] 强永平,李耀宗,白洪林,等. 组合喷射对双对置二冲程发动机燃烧过程影响的计算研究[J]. 车用发动机,2014(5): 46-53.QIANG Yongping,LI Yaozong,BAI Honglin,et al. Influence of combined injection on OPOC two-stroke engine combustion[J]. Vehicle Engine,2014(5): 46-53. (in Chinese) [14] MA Fukang,ZHAO Changlu,ZHANG Fujun,et al. An experimental investigation on the combustion and heat release characteristics of an opposed-piston folded-cranktrain diesel engine[J]. Energies,2015,8(7): 6365-6381. doi: 10.3390/en8076365 [15] 刘彩明,续彦芳,许俊峰,等. 对置活塞二冲程柴油机喷油角度对油气混合的影响[J]. 科学技术与工程,2015,15(2): 227-230.LIU Caiming,XU Yanfang,XU Junfeng,et al. Influence of fuel injection angle on air-fuel mixing and combustion of OPOC engine[J]. Science Technology and Engineering,2015,15(2): 227-230. (in Chinese) [16] 章振宇,赵长禄,张付军,等. 对置二冲程柴油机喷油规律曲线对燃烧过程影响的仿真研究[J]. 内燃机工程,2015,36(6): 32-37.ZHANG Zhenyu,ZHAO Changlu,ZHANG Fujun,et al. Simulation of the effect of fuel injection rate-shape on combustion process of an opposed-piston two-stroke diesel engine[J]. Chinese Internal Combustion Engine Engineering,2015,36(6): 32-37. (in Chinese) [17] 谢钊毅. 对置活塞二冲程柴油机喷雾过程的试验研究与数值模拟[D]. 北京: 北京理工大学, 2016.XIE Zhaoyi. Experimental study and numerical simulation of the spray process in an opposed-piston two-stroke diesel engine[D]. Beijing: Beijing Institute of Technology, 2016. (in Chinese) [18] ZHANG Zhenyu,ZHANG Peng,ZHAO Zhenfeng. Spray impingement and combustion in a model opposed-piston compression ignition engine[J]. Combustion Science and Technology,2017,189(11): 1943-1965. doi: 10.1080/00102202.2017.1340278 [19] 刘宇航,赵振峰,张付军,等. 对置活塞二冲程柴油机双喷油器碰撞喷雾试验研究[J]. 兵工学报,2017,38(10): 1881-1890.LIU Yuhang,ZHAO Zhenfeng,ZHANG Fujun,et al. Experimental study of impingement spray of dual-fuel injector of opposed piston two-stroke diesel engine[J]. Acta Armamentarii,2017,38(10): 1881-1890. (in Chinese) [20] 马富康,赵长禄,张付军,等. 对置活塞二冲程汽油机燃烧过程组织研究[J]. 小型内燃机与车辆技术,2017,46(1): 1-9.MA Fukang,ZHAO Changlu,ZHANG Fujun,et al. Organization of combustion process on opposed-piston two-stroke gasoline engine[J]. Small Internal Combustion Engine and Vehicle Technique,2017,46(1): 1-9. (in Chinese) [21] ZHOU Lei, ZHANG Hongxing, ZHAO Zhenfeng, et al. Research on opposed piston two-stroke engine for unmanned aerial vehicle by thermodynamic simulation[R]. Warrendale, US: SAE International, 2017. [22] 陈泽玉. 对置活塞二冲程发动机缸内燃烧数值模拟及优化[D]. 哈尔滨: 哈尔滨工业大学, 2020.CHEN Zeyu. Numerical simulation and optimization of In-cylinder combustion of opposed piston two stroke engine[D]. Harbin: Harbin Institute of Technology, 2020. (in Chinese) [23] VENUGOPAL R, ABANI N, MACKENZIE R. Effects of injection pattern design on piston thermal management in an opposed-piston two-stroke engine[R]. Warrendale, US: SAE International, 2013. [24] HUO Ming, HUANG Yuexin, HOFBAUER P. Piston design impact on the scavenging and combustion in an opposed-piston, opposed-cylinder (OPOC) two-stroke engine[R]. Warrendale, US: SAE International, 2015. [25] SHIRVANI S, SHIRVANI S, SHAMEKHI A. Effects of injection parameters and injection strategy on emissions\n and performance of a two-stroke opposed-piston diesel engine[R]. Warrendale, US: SAE International, 2020 [26] LEFEBVRE A H, MCDONELL V G. Atomization and sprays[M]. 2nd ed. Boca Raton, US: Taylor & Francis Group, 2017. -
点击查看大图
计量
- 文章访问数: 42
- HTML浏览量: 19
- PDF量: 2
- 被引次数: 0