1.Yantai Research Institute,Harbin Engineering University,Yantai,Shandong,264000
2.College of Power and Energy Engineering,Harbin Engineering University,Harbin,150001
3.Zichai Power Co. ,Ltd. ,Zibo,Shandong,255035
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文章历史+
Received
Accepted
Published
2024-10-31
Issue Date
2026-04-07
PDF (1737K)
摘要
为了探明船用甲醇动力的特性并为建模仿真研究提供校核数据,对一台船用甲醇-柴油双燃料发动机进行了推进特性试验,对比了发动机在纯柴油模式以及双燃料模式下的经济性、燃烧性能及排放性能。研究结果表明,甲醇的加入对发动机的等效燃料消耗量影响较小,但同工况下最多可以降低18.22%的单位功成本;甲醇的加入会导致各工况点下的燃烧持续期缩短、平均有效压力降低;双燃料模式下发动机的CO与HC排放均高于柴油模式,双燃料模式下的NO x 排放仅在高负荷时略高于柴油模式。
Abstract
In order to investigate the characteristics of marine methanol powers and provide calibration data for modeling simulation studies, a marine methanol-diesel dual fuel engine was subjected to propulsion characteristics tests. The economy, combustion performance and emission performance of the engines were compared under pure diesel mode and dual fuel mode. The results show that the addition of methanol has a small effect on the equivalent fuel consumption of the engines, but it may reduce the unit power cost by 18.22% at most under the same operating conditions; the addition of methanol leads to the shortening of the combustion duration and the reduction of the average effective pressure at each operating point; the CO and HC emissions of the engines under the dual-fuel mode are higher than those of under the diesel mode, and the NO x emissions under dual-fuel mode are slightly higher than those of the diesel mode only at high loads.
在交通运输业中,水运运量大、距离远、周期长,对输出源的动力性、经济性与可靠性有着较高需求[1-3]。柴油机凭借着动力输出强、热效率高、经济性好的诸多优势在该领域得到了广泛运用,成为船舶主要动力输出装置[4]。然而,随着排放法规的日益严苛、石油战略意义的不断增强,如何使船用发动机在保证动力输出的同时提升经济性并减少污染物排放,成为了内燃机界的重要研究课题。尽管国内外许多专家学者针对废气再循环系统(exhaust gas recirculation,EGR)、选择性催化还原系统(selective catalytic reduction,SCR)等发动机辅助设备进行了大量研究,但这并未从根本上解决化石燃料应用及高污染排放的问题,使用清洁替代燃料成为解决这一问题的有效措施[5]。
本文的试验对象原型为一台船用柴油机,柴油通过电子组合泵加压后经由机械阀喷入缸内;通过对原机进气歧管打孔,并安装甲醇供给系统、甲醇轨、喷射器以及甲醇/柴油模式电子控制器(electronic control unit,ECU)可以将原机改造为船用甲醇/柴油双燃料发动机。甲醇喷射器及进气歧管打孔的示意图见图1。
发动机及测控系统的实物图见图3,将水力测功机与发动机相连为发动机提供负荷,并对发动机的输出扭矩和转速进行监测。通过安装在1缸的缸压传感器对发动机的缸内燃烧情况进行监测,并基于燃烧分析仪进行信号处理和数据分析,最终可以得到缸内压力、放热率、平均指示有效压力等数据,在试验中待发动机稳定运行后,取发动机转动200 r的缸压数据平均值。为确保排放采样的准确性,排放分析仪的取样口需设置在排气管上,且应选取距发动机排气口下游约10倍排气管直径的位置,并通过该取样口对发动机尾气中的CO、CO2、NO x 、THC等进行采样分析,待排放分析仪读数稳定后记录30 s内的各排放物的排放浓度平均值。
将相同工况下两种模式下第1缸的最大缸压及对应转角、CA05(指累积放热达到总放热量5%时对应的曲轴转角,即燃烧始点)、CA50(指累积放热达到总放热量50%时对应的曲轴转角,即燃烧重心)、CA90(指累积放热达到总放热量90%时对应的曲轴转角,即燃烧终点)、燃烧持续期和平均有效压力作为发动机燃烧性能的评判标准。将相同工况下两种模式下CO、CO2、NO x 等污染物排放的情况作为发动机排放性能的评判标准。本文中,D代表发动机处于纯柴油模式时得到或计算出的数据,M/D代表发动机处于甲醇/柴油双燃料模式时得到或计算出的数据。
图14a展示了两种模式下尾气排放中的NO x 含量和O2含量的对比情况。可以看出:全工况下发动机的NO x 排放均大于0.1%,在25%~75%负荷间双燃料模式下的NO x 排放均低于柴油模式。25%负荷下两种模式的NO x 排放均为最高,其中双燃料模式下的NO x 排放为0.1356%,柴油模式下的NO x 排放为0.1477%;100%负荷下两种模式的NO x 排放均为最低,其中双燃料模式下的NO x 排放为0.1101%,柴油模式下的NO x 排放为0.1051%。与此同时,双燃料模式下尾气中的O2含量均高于柴油模式,如图14b所示。
发动机工作中,NO x 的生成需要满足高温、富氧和燃烧反应持续时间三个条件。25%~75%负荷下,双燃料模式下尾气中的NO x 均低于纯柴油模式,但双燃料模式下排放尾气的O2含量与纯柴油模式下的差值不低于0.39%,远高于90%及100%负荷下的氧含量差值,分别为0.15%及0.01%。由此可认为此时缸内即便有较为充足的氧气,但大量甲醇的加入降低了缸内温度,从而削弱了NO x 的生成条件;在高负荷时甲醇替代率较低,且缸内温度进一步升高,这导致缸内的N2能够充分与O2发生反应,从而导致NO x 排放升高。
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