梅德清, 任华, 姜士阳, 王忠, Roland Baar. 多段燃油喷射对碳酸二甲酯-柴油混合燃料燃烧过程的影响[J]. 农业工程学报, 2014, 30(8): 74-80. DOI: 10.3969/j.issn.1002-6819.2014.08.009
    引用本文: 梅德清, 任华, 姜士阳, 王忠, Roland Baar. 多段燃油喷射对碳酸二甲酯-柴油混合燃料燃烧过程的影响[J]. 农业工程学报, 2014, 30(8): 74-80. DOI: 10.3969/j.issn.1002-6819.2014.08.009
    Mei Deqing, Ren Hua, Jiang Shiyang, Wang Zhong, Roland Baar. Effects of multiple injections strategy on combustion process of mixed fuels with dimethyl carbonate and diesel[J]. Transactions of the Chinese Society of Agricultural Engineering (Transactions of the CSAE), 2014, 30(8): 74-80. DOI: 10.3969/j.issn.1002-6819.2014.08.009
    Citation: Mei Deqing, Ren Hua, Jiang Shiyang, Wang Zhong, Roland Baar. Effects of multiple injections strategy on combustion process of mixed fuels with dimethyl carbonate and diesel[J]. Transactions of the Chinese Society of Agricultural Engineering (Transactions of the CSAE), 2014, 30(8): 74-80. DOI: 10.3969/j.issn.1002-6819.2014.08.009

    多段燃油喷射对碳酸二甲酯-柴油混合燃料燃烧过程的影响

    Effects of multiple injections strategy on combustion process of mixed fuels with dimethyl carbonate and diesel

    • 摘要: 柴油机多段燃油喷射可用来优化缸内燃烧以实现排放净化的目标。该文采用两段预喷和一段主喷组合的多段燃油喷射进行混合燃料D10(90%柴油+10%碳酸二甲酯)燃烧过程的研究。通过预喷相位可调但3段喷油之间相位间隔恒定、主喷持续时间可调但第1、2段预喷持续时间固定的喷油策略,实现在目标工况下精确的放热中心COHR(center of heat release)。当调整多段燃油喷射策略实现目标COHR以等步长推移时,柴油机的燃烧过程呈现如下特点:各工况的着火时刻均处于第2段预喷和主喷之间;从喷油时刻至着火时刻所经历的曲轴转角越来越小;着火时刻至放热中心所占用的曲轴转角则越来越大;缸内燃烧压力峰值出现位置与放热中心位置较为接近,相对缸内峰值压力出现位置,COHR不断后移且相距更远。与柴油相比,D10的滞燃期更长,其最大压升率也更高。由于易汽化的碳酸二甲酯促进了燃料混合及后续燃烧,从着火时刻到10%放热率及90%放热率对应时刻所占用曲轴转角均变小,说明碳酸二甲酯的加入有助燃烧的迅速进行。基于COHR为表征的燃烧特性分析,为碳酸二甲酯/柴油混合燃料的应用、多段燃油喷射调控燃烧过程及排放控制理论提供指导。

       

      Abstract: Abstract: In order to achieve the target of emission purification within the aspect of combustion optimizing in a cylinder, as well as the partial replacement of fossil fuels, a study on the combustion process of dimethyl carbonate (DMC)-diesel fuel blend was carried off. A fuel blend D10 (10% DMC and 90% diesel by volume) was chosen as the test fuel. The experiments were conducted on a single-cylinder research engine originated from a Daimler Benz OM646 2.2 litre common rail direct injection four-cylinder in-line diesel engine. As for the research engine, the indicated mean effective pressure pmi was adopted as the baseline for assessment of engine performance. A given load at 1900 r/min was chosen as the engine operating mode. According to the first law of thermodynamics, the heat release rate can be presented in real-time by the IndiCom software. The exact position in the crank angle of the center of heat release (COHR, 50% of the total heat release) can be figured out by interpolation. It was a key parameter to describe the combustion process of the engine. Through a fuel injection strategy characterized by an adjustable first pre-injection phase but constant phase intervals between the three injections and adjustable main injection duration but fixed durations of first pre-injection and second pre-injection, the accurate COHR target at a steady working mode can be implemented. Therefore five modes with an even interval of COHR, under the same engine speed and pmi, were inspected. As for D10 fuel, to compensate for its energy density falling, the rail pressure of D10 was 3 MPa higher than that of a diesel. While using D10 fuel, two schemes were considered. One was to keep the injection parameters of fuel system unchanged. The other was to slightly adjust the injection parameters, thus the COHR can be precisely accorded with the original diesel engine. When multiple injection strategy was adjusted to achieve the exact COHR which was delayed in constant step, the features of the combustion process of a diesel engine were analyzed. The ignition for each operating mode occurred between the second pilot injection and the main injection. For every two adjacent modes varying with COHR, the crank angle intervals of the fuel injection timings as well as center of heat release and the location of heat release peak were almost identical. With the increase of COHR, the duration in crank angle taken from injection timing to ignition became shorter, while the duration in the crank angle taken from ignition to the center of the heat release became longer. As compared with the location of a peak pressure in-cylinder, the COHR would be moved backward far away. As for D10 fuel, because the easy vaporization of dimethyl carbonate promoting the mixing of fuel and air and combustion, both crank angle intervals, from the ignition to 10% of heat release and from ignition to 90% of heat release, were shorter, which indicated that the added dimethyl carbonate could help to promote the combustion process. These analyses of combustion features based on COHR will provide a fundamental guidance for the application of dimethyl carbonate/diesel blends, multiple injections regulating the combustion process, and emission control theory.

       

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