柴油喷射策略对甲醇/柴油双直喷发动机性能的影响

doi:10.11949/0438-1157.20250912

摘要/Abstract

摘要：

通过改变柴油喷射时刻和喷射压力，研究了50.0%甲醇能量替代率下不同柴油喷射策略对甲醇/柴油双直喷发动机燃烧特性、经济特性和排放特性的影响。结果表明，提前柴油喷射时刻有助于改善缸内燃料和空气的混合效果，缩短燃烧持续时间，从而提高指示热效率。适当提前喷射时刻与增加喷射压力（从80 MPa升至100 MPa）可显著增强燃烧稳定性，指示平均有效压力变动系数（COV_IMEP）最大降幅达44.4%（从3.6%降至2.0%），但会增加爆震风险。总体而言，柴油喷射时刻对热效率的影响大于喷射压力。此外，通过喷射时刻（-12 º）与喷射压力（100 MPa）的同步优化，发动机最高指示热效率可达41.3%，同时污染物排放显著改善：CO比排放量最大降幅10.7%（80 MPa 下从7.8 g‧（kW‧h）^-1 降至7.0 g‧（kW‧h）^-1），HC与Soot比排放量显著降低，尽管NO _x 排放有所增加，但总体仍维持在5 g‧（kW‧h）^-1以下的较低水平。

关键词: 双燃料发动机, 甲醇/柴油双直喷, 燃烧特性, 喷射策略, 醇, 污染, 排放

Abstract:

By varying the diesel injection timing and injection pressure, this study investigated the effects of different diesel injection strategies on the combustion characteristics, economic characteristics, and emission characteristics of a methanol/diesel dual direct-injection engine under a 50.0% methanol energy substitution rate. The results show that advancing the diesel injection timing helps improve the mixing of fuel and air in the cylinder and shorten the combustion duration, thereby increasing the indicated thermal efficiency. Appropriate advancement of injection timing combined with an increase in injection pressure (from 80 MPa to 100 MPa) can significantly enhance combustion stability. The coefficient of variation of indicated mean effective pressure (COV_IMEP) experiences a maximum reduction of 44.4% (from 3.6% to 2.0%), but this also increases the knock risk. Overall, the diesel injection timing has a greater impact on thermal efficiency than the injection pressure.In addition, through the simultaneous optimization of injection timing (-12 º) and injection pressure (100 MPa), the maximum indicated thermal efficiency of the engine can reach 41.3%, while pollutant emissions are significantly improved: the specific CO emissions have a maximum reduction of 10.7% (decreasing from 7.8 g‧(kW‧h)^-1 to 7.0 g‧(kW‧h)^-1 under 80 MPa), and the specific HC and Soot emissions are significantly reduced. Although NO _x emissions increase slightly, they still remain at a low level below 5 g‧(kW‧h)^-1 overall.

Key words: dual-fuel engine, methanol/diesel dual direct injection, combustion characteristics, injection strategy, alcohol, pollution, emissions

中图分类号:

TK 431

雷军, 胡友耀, 赵晨辉, 尹晓军, 段浩, 胡二江, 曾科. 柴油喷射策略对甲醇/柴油双直喷发动机性能的影响[J]. 化工学报, DOI: 10.11949/0438-1157.20250912.

Jun LEI, Youyao HU, Chenhui ZHAO, Xiaojun YIN, Hao DUAN, Erjiang HU, Ke ZENG. Effects of Diesel Injection Strategy on Performance of Methanol/diesel Dual Direct Injection Engine[J]. CIESC Journal, DOI: 10.11949/0438-1157.20250912.

图/表 15

表1 原柴油机主要参数

Table 1 Main parameters of original diesel engine

项目	数值或描述	项目	数值或描述
发动机类型	单缸风冷柴油机	压缩比	19.0:1
排量 (L)	0.498	最大扭矩/转速 (N‧m)/(r·min^-1)	25/2000
缸径/行程 (mm)	92/75

图1 燃烧系统的剖面图

Fig.1 Combustion system cross-sectional view

图2 DMDDI发动机试验平台

Fig.2 DMDDI engine test platform

表2 发动机运行工况参数设置

Table 2 Engine parameter setup

参数	设定值	参数	设定值
转速/(r·min^-1)	2000	甲醇能量替代率/(%)	50.0
柴油喷射压力/MPa	80~100	柴油主喷时刻/º	-13~-8
柴油主喷预喷间隔角/º	12	甲醇喷射压力/MPa	15
甲醇喷射时刻/º	-60

图3 θD2和pD对燃烧过程p值和HRR的影响

Fig.3 Effects of θD2 and pD on pressure and HRR in combustion processes

图4 不同pD下的θD2对着火延迟的影响

Fig.4 Effect of θD2 on ignition delay under different pD conditions

图5 不同pD下的θD2对CA50的影响

Fig.5 Effect of θD2 on CA50 under different pD conditions

图6 不同pD下的θD2对CD的影响

Fig.6 Effect of θD2 on CD under different pD conditions

图7 不同pD下的θD2对Rmax的影响

Fig.7 Effect of θD2 on Rmax under different pD conditions

图8 不同pD下的θD2对COVIMEP的影响

Fig.8 Effect of θD2 on COVIMEP under different pD conditions

图9 不同pD下的θD2对ITE的影响

Fig.9 Effect of θD2 on ITE under different pD conditions

图10 不同pD下的θD2对NOX比排放的影响

Fig.10 Effect of θD2 on BSNOX under different pD conditions

图11 不同pD下的θD2对CO比排放的影响

Fig.11 Effect of θD2 on BSCO under different pD conditions

图12 不同pD下的θD2对HC比排放的影响

Fig.12 Effect of θD2 on BSHC under different pD conditions

图13 不同pD下的θD2对碳烟比排放的影响

Fig.13 Effect of θD2 on BSSoot under different pD conditions

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