Comparative study of hydrogen addition effects on the natural-gas/diesel and natural-gas/dimethyl-ether reactivity controlled compression ignition mode of operation
Comparative study of hydrogen addition effects on the natural-gas/diesel and natural-gas/dimethyl-ether reactivity controlled compression ignition mode of operation
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DOI：
10.1016/j.enconman.2019.05.113
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发表时间：
2019-09-15
影响因子：
10.4
通讯作者：
Gharehghani, A.
中科院分区：
文献类型：
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作者：
Kakoee, A.;Gharehghani, A.
反应性控制压燃式发动机与其他低温燃烧策略相比具有更好的性能。使用不同的燃料可以根据化学产物和反应以及热值而具有不同的输出。本文采用数值模型和实验数据相结合的方法，研究了添加剂对天然气/二甲醚和天然气/柴油反应性控制压燃式发动机燃烧特性的影响。氢气作为添加剂，在燃料混合物中具有3%、6%和9%的热值。结果表明，在所有使用柴油作为高反应性燃料的情况下，指示平均有效压力较高。燃烧特性研究表明，天然气/柴油混合燃料的燃烧开始时间和燃烧相位提前，燃烧持续时间比天然气/柴油混合燃料的燃烧持续时间长。通过添加氢物种，可以看出，氢对天然气/二甲醚情况下的燃烧开始具有更大的影响，其中添加9%的氢，使燃烧开始提前约2曲柄角度，而天然气/柴油情况下的该量为约0.3。在所有使用柴油作为高反应性燃料的情况下，温度高于使用二甲醚的情况，这导致产生更多的氮氧化物;例如，在9%的氢气添加下，天然气/柴油模式比天然气/二甲醚模式多产生0.54 g/kW/h氮氧化物。基于所获得的结果，天然气/柴油模式下的一氧化碳排放在所有情况下均低于2 g/kW/h，而在天然气/二甲醚的每种情况下，该排放均高于8 g/kW/h。这种情况也发生在未燃烧的碳氢化合物排放物上，其中对于天然气/二甲醚加燃料的情况，这种排放物高于11 g/kW/h，而对于天然气/柴油模式，这种排放物低于2 g/kW/h。定量比较表明，氢气的添加是更有效的天然气/二甲醚反应性控制的压缩着火模式。根据二甲醚分解过程，注入开始为二甲醚分解为其产物（尤其是甲烷）提供了时间。基于数值计算结果，超过10%的二甲醚在燃烧开始之前被分解，这代表了在天然气/二甲醚情况下开始喷射的重要性。
Reactivity controlled compression ignition engines have been proven to have better performance comparing with other methods of low temperature combustion strategies. Using various fuels can have different outputs according to the chemical products and reactions as well as heating values. In this study, a numerical model beside experimental data as validation is used to investigate the effects of using additive on combustion characteristics of natural gas/dimethyl-ether and natural-gas/diesel Reactivity controlled compression ignition engines. Hydrogen is used as additive with 3, 6 and 9 percentage of heating value in the fuel mixture. Results show higher indicated mean effective pressure in all cases of using diesel as high reactivity fuel. In addition, investigation on the combustion characteristics shows that natural gas/diesel cases have advanced start of combustion and combustion phasing, while burn duration in natural gas/dimethyl-ether cases is higher than natural gas/diesel cases. By adding hydrogen species, it is seen that hydrogen has more effect on the start of combustion of natural gas/dimethyl-ether case where adding 9% hydrogen, advanced the start of combustion about 2 crank angle degree while this amount for natural gas/diesel case is about 0.3. In all cases of using diesel as high reactivity fuel, temperature is higher than dimethyl-ether used cases, which causes to produce more nitrogen oxides; for example, in 9% hydrogen addition, natural gas/diesel mode produced 0.54 g/kW/h nitrogen oxide more than natural gas/dimethyl-ether mode. Based on achieved results, carbon monoxide emission in natural gas/diesel mode is lower than 2 g/kW/h for all cases where this emission is higher than 8 g/kW/h in each case of natural gas/dimethyl-ether. This condition was also occurred for unburned hydrocarbons emissions, where this emission is higher than 11 g/kW/h for natural gas/dimethyl-ether fueling case while it is lower than 2 g/kW/h for natural gas/diesel mode. Quantitatively comparison shows that hydrogen addition is more effective on natural gas/dimethyl-ether reactivity controlled compression ignition mode. According to dimethyl-ether breaking up process, start of injection provides a time to decomposition of dimethyl-ether to its products, especially Methane. Based on numerical results, more than 10% of dimethyl-ether is broken up before start of combustion that represented importance of start of injection in natural gas/dimethyl-ether case.