共查询到17条相似文献,搜索用时 531 毫秒
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燃油多次喷射控制策略对单缸柴油机燃烧与排放特性的影响 总被引:1,自引:0,他引:1
基于高压共轨系统对一台单缸柴油机采用燃油预喷射控制策略时的燃烧特性与排放特性变化规律进行了研究。在保持循环油量不变的前提下,通过控制每循环燃油的喷射次数、预喷油量、预喷与主喷的间隔角,对发动机缸内燃烧压力、放热规律、压力升高率及排放变化规律进行了分析。试验结果表明:当预喷油量小于5 mg/循环时,发动机能够在维持炭烟颗粒不增加的同时降低NO x的排放,同时发动机的压升率也较无预喷工况有所降低;多次喷射燃烧过程对燃油消耗率的影响较小,较无预喷工况略有上升,但通过对预喷角度、预喷油量及间隔角的合理匹配,能够实现对燃油消耗率的进一步优化。 相似文献
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《汽车工程》2015,(10)
本文中对比分析了某四缸轻型车用柴油机喷射正时、废气再循环(EGR)率和喷射压力对燃烧过程和污染物排放的影响规律。结果表明:采用适时早喷或者晚喷策略均能延长滞燃期而改善可燃混合气的均匀性,以实现部分预混合燃烧,抑制碳烟排放。适时早喷策略相对晚喷策略更有利于降低碳烟排放,但将受到NO_x排放恶化的限制。引入EGR后,适时早喷不但可降低缸内燃烧温度抑制NO_x排放,还可有效解决因早喷带来的燃烧相位过早的问题,从而提高燃烧效率,改善燃油经济性,在高EGR率区域可兼顾有效燃油消耗率、NO_x和碳烟排放。而晚喷条件下,引入EGR后会进一步加重后燃现象,使有效燃油消耗率和碳烟排放有所恶化。随着喷射压力的提高,适时早喷时,燃烧放热过程变缓,瞬时放热率峰值和缸内平均温度降低,从而可同时降低NO_x和碳烟排放,而晚喷则相反,NO_x排放随着喷射压力的提高而有所上升。而不论适时早喷还是晚喷,有效燃油消耗率受喷射压力的影响很小。 相似文献
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预喷射对生物柴油发动机燃烧及排放特性影响研究 总被引:3,自引:0,他引:3
研究了不同预喷条件下满足国Ⅴ排放的高压共轨柴油机燃用混合燃料BD20(含80%体积分数的国Ⅴ柴油和20%体积分数的餐饮废油制生物柴油)的燃烧及排放特性。结果表明:采用预喷射后滞燃期有所缩短,燃烧持续期有所增大。相比于预喷间隔,预喷油量对滞燃期及燃烧持续期的影响更为显著;预喷射显著减小了主燃烧的压力升高率,改善了燃烧的剧烈程度,且低负荷取较小预喷间隔、高负荷取较大预喷间隔效果较优;采用预喷射后NO x 排放均有所降低,大部分预喷射条件下PM 排放有所增加,各负荷均存在着较佳预喷射方案,可以同时改善NO x 及PM 排放。 相似文献
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正(接上期)(6)预喷射通过在压缩行程期间少量燃油(约1mg)的燃烧提高主喷射开始时刻汽缸内的压力和温度,能够缩短主喷射的着火滞后期,这能降低燃烧产生的噪声。但是,因为减少了预混合燃烧的燃油份额,同时增加了扩散燃烧的燃油量,以及提高了汽缸中的温度,会使炭烟颗粒和NOx排放有所增加。另一方面,冷启动和低负荷范围内,较高的燃烧室温度对稳定燃烧,降低HC和CO排放 相似文献
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柴油微引燃乙醇发动机采用进气道喷射乙醇、缸内直喷微量柴油引燃的方式进行燃料供给。基于单缸四冲程柴油机,对其燃烧、性能及排放特性进行研究,固定引燃柴油喷射量为发动机能实现压燃着火的最小值,在进气压力为0.15 MPa时比较不同乙醇喷射量的工况组,通过改变柴油喷射时刻进行工况扫描。结果表明,引燃柴油的喷射时刻对发动机的燃烧、性能和排放影响显著。柴油微引燃乙醇发动机在中高负荷能够稳定运行,指示热效率可达34%以上,通过适当调节柴油喷射时刻,可以有效控制未燃碳氢(UHC)、NO_x与CO排放,同时可以实现极低的炭烟排放。柴油微引燃乙醇发动机燃烧模式为预混合或部分预混合燃烧,燃烧有两阶段放热特征,改变引燃柴油喷射时刻,可以有效控制燃烧相位。 相似文献
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J. H. Jeong D. W. Jung O. T. Lim Y. D. Pyo Y. J. Lee 《International Journal of Automotive Technology》2014,15(6):861-869
This work experimentally investigates how the dwell time between pilot injection and main injection influences combustion and emissions characteristics (NOx, CO, THC and smoke) in a single-cylinder DI diesel engine. The experiments were conducted using two fuel injection systems according to the fuel type, diesel or dimethyl ether (DME), due to the different fuel characteristics. The injection strategy is accomplished by varying the dwell time (10°CA, 16°CA and 22°CA) between injections at five main injection timings (?4°CA aTDC, ?2°CA aTDC, 0°CA aTDC, 2°CA aTDC and 4°CA aTDC). Results from pilot-main injection conditions are compared with those shown in single injection conditions to better demonstrate the potential of pilot injection. It was found that pilot injection is highly effective for lowering heat-release rates with smooth pressure traces regardless of the fuel type. Pilot injection also offers high potential to maintain or increase the BMEP; even the combustion-timing is retarded to suppress the NOx emission formation. Overall, NOx emission formation was suppressed more by the combustion phasing retard effect, and not the pilot injection effect considered in this study. Comparison of the emissions for different fuel types shows that CO and HC emissions have low values below 100 ppm for DME operation in both single injection and pilot-main injection. However, NOx emission is slightly higher in the earlier main injection timings (?4°CA aTDC, ?2°CA aTDC) than diesel injections. Pilot injection was found to be more effective with DME for reducing the amount of NOx emission with combustion retardation, which indicates a level of NOx emission similar to that of diesel. Although the diesel pilot-main injection conditions show higher smoke emission than single-injection condition, DME has little smoke emission regardless of injection strategy. 相似文献
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通过柴油机工作过程测量分析系统对一台直喷式车用柴油机加速时的喷油和燃烧过程进行了试验研究和计算,并计算了其加速过程中的总声压级;利用油滴蒸发准维燃烧模型对柴油机加速过程NOx 排放进行了模拟计算。研究结果表明,柴油机喷油和燃烧特性参数的综合效果对NOx排放值产生影响;柴油机加速时的燃烧噪声大于标定工况,加速工况时的NOx 排放浓度值变化较大,有时大于标定工况。 相似文献
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This paper focuses on the mechanisms of combustion noise during the accelerating operation of multi-cylinder diesel engines
using testing technology for the transient conditions of IC engines. Based on impact factors, such as the gas dynamic load
and cylinder pressure oscillations, tests and analysis of the combustion noise during transient and steady-state conditions
for different loads are made on four-cylinder naturally aspirated engines, turbocharged engines, EGR-introduced engines, and
high pressure common rail engines. The laws of combustion noise difference for the same engine speed and load are researched
during transient and steady-state conditions. It is found that during transient conditions, the maximum pressure rise rate
and the high frequency oscillation amplitude of the cylinder pressure are all higher than those observed during steadystate
conditions for the same engine speed and load. With their joint action, the combustion noise during transient conditions is
greater than that during steady-state conditions. Turbocharging is useful in reducing the combustion noise during transient
conditions. Turbocharging has a better effect on the control over the combustion noise during transient conditions with a
constant engine speed and an increasing torque than in conditions with a constant torque and an increasing engine speed. One
of the main reasons for different control effects on the combustion noise is that turbocharging causes different wall temperatures
inside combustion chambers. The introduction of the appropriate EGR is helpful in the reduction of the combustion noise during
transient conditions. The key to the control of combustion noise with EGR during transient conditions is whether a real-time
adjustment to the EGR rate can be made to achieve the optimization of the EGR rates for different transient conditions. By
means of analyzing the differences in the combustion noise between the transient and steady-state conditions for different
pilot injection controls, we obtain a strategy for controlling the combustion noise during transient conditions with a pilot
injection. Compared with the steady-state conditions, a larger pilot injection quantity and a longer interval between the
main injection and pilot injection should be selected for transient conditions, and this is verified through tests. 相似文献