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Fuel effects on the low temperature performance of two generations of Mercedes-Benz heavy-duty diesel engines

机译:对两代梅赛德斯 - 奔驰重型柴油发动机的低温性能的燃料影响

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Cold performance is a very important issue for diesel engines. Customers expect their engines to start reliably under all ambient conditions, and to quickly deliver useful power without unacceptable noise or exhaust emissions. In this program the low-ambient-temperature, cold-start performance of two generations of Mercedes-Benz heavy-duty diesel engines has been explored. Both are typical of the smaller European heavy-duty engine design. The OM364 LA meets Euro 2 emissions legislation using mechanical controls; the OM904 LA is the first evolution of an all-new design to replace the OM364 LA, and features a three-valve cylinder head and high-pressure unit-pump injection, with fully electronic controls. Engines were tested in a temperature-controlled chamber, using a procedure that studied the first few minutes of operation from cold. In production engines intended for use in cold climates a cold-starting aid is used which improves cold-start performance, and reduces sensitivity to fuel properties. In order to more clearly discriminate fuel effects, starting aids were not used in this program. Three production fuels were tested in both engines, including European specification fuels from the UK and Germany, and an ultra-low sulfur fuel from Fin-land. Work was focused on the OM904 LA which was tested at ambient temperatures ranging from -5°C to -20°C, whilst the OM364 LA was tested only at -15°C.The results showed that the new OM904LA gave major improvements over the OM364 LA in all aspects of low-temperature, cold-start performance, including starting time and exhaust emissions of white smoke and unburned hydrocarbons. Performance was strongly affected by ambient temperature, with substantial increases in starting time and emissions as the temperature was reduced from -5°C to -20°C. The Finnish fuel gave the best overall performance in both engines. The German fuel tested had lower density/higher volatility than the UK test fuel and gave reduced smoke, but increased HC emissions. Fuel effects on starting time were significant in the OM364 LA, but not in the OM904 LA. Additional work was carried out to provide a better under-standing of the important fuel variables, using a special fuel matrix designed to allow the effects of cetane number, front-end and back-end volatility to be separated. This showed that cetane number was the dominant fuel parameter affecting cold-start performance. No effects of back-end volatility were detected, and effects of front-end volatility were relatively small and varied between engines. These results helped explain the performance of the production fuels, and suggested that other fuel properties had only a minor effect. The performance of fuels with and without cetane improver was tested at 50 cetane number and found to be comparable at the same measured cetane number. This confirmed the effectiveness of the selected cetane improver at low ambient temperatures and at the treat rates investigated. Use of cetane improver was tested up to 55 cetane number, and gave significant reductions in hydrocarbon emissions.
机译:冷表现是柴油发动机的一个非常重要的问题。客户希望他们的发动机在所有环境条件下可靠地开始可靠,并且在没有不可接受的噪音或废气排放的情况下快速提供有用的电力。在该计划中,探讨了两代梅赛德斯 - 奔驰重型柴油发动机的低环境温度,冷启动性能。两者都是典型的欧洲重型发动机设计。 OM364 LA使用机械控制符合欧元2欧元的排放法律; OM904 LA是全新设计的首次演进,以更换OM364 LA,采用三阀缸盖和高压单元泵注射,具有全电子控制。使用从冷的前几分钟操作的过程中在温度控制的腔室中测试了发动机。在用于寒冷气候的生产发动机中,使用冷启动助剂,从而提高了冷启动性能,并降低了对燃料特性的敏感性。为了更明确地歧视燃料效应,在该计划中没有使用起始助剂。在两个发动机中测试了三种生产燃料,包括来自英国和德国的欧洲规格燃料,以及来自鲑鱼的超低硫磺燃料。工作集中在OM904La上,在-5°C至-20°C的环境温度下测试,同时仅在-15°C测试。结果表明,新的OM904LA对此产生了重大改进OM364 LA在低温,冷启动性能的各个方面,包括白色烟雾和未燃烧的碳氢化合物的起始时间和排气。性能受环境温度的强烈影响,开始时间和排放随着温度从-5℃降低至-20℃而大大增加。芬兰燃料在两个发动机中给出了最佳整体性能。德国燃料测试的密度低于英国试验燃料的较低密度/更高的挥发性,并减少了烟雾,但增加了HC排放量。 OM364 LA的开始时间的燃料效应在OM904 LA中是显着的。使用旨在允许分离的十六烷值,前端和后端波动率的特殊燃料矩阵来提供额外的工作以提供更好的燃料变量。这表明十六烷数是影响冷启动性能的主要燃料参数。没有检测到后端挥发性的影响,并且前端挥发性的影响相对较小并且在发动机之间变化。这些结果有助于解释生产燃料的性能,并表明其他燃料特性只有轻微影响。在50个十六烷数下测试燃料的性能,并在50甲烷数下测试,发现在相同的测定的十六烷数量上可相当。这证实了所选的十六烷改进剂在低环境温度下的有效性,并在调查的治疗率下进行。使用十六烷改进剂的使用最多可测试55个十六烷数,并在碳氢化合物排放中略微减少。

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