【作者】

Oliver Lehmann

【摘要】

该论文已在赫尔辛基举行的第28届CIMAC大会上发表，论文的版权归CIMAC所有。ABSTRACT The linking between the striving for higher efficiency and global tightening of emissions legislation is one of today’s biggest technical challenges in the field of large bore engines. In case of raw emissions, gas-fuelled engines show a lower concentration of pollutants like carbon dioxide compared to other fossil fuels. To achieve high efficiency and lowest level of emissions altogether, lean-burn gas engines are a promising approach of reciprocating engines. In terms of insignificantly changed components, the operating conditions may have modified, which can exhibit wear. Valve wear is an example that links the global tightening of emission legislations and the striving for more efficiency. Operating conditions created by lean-burn concepts, efficiency enhancing measures such as, for example, higher peak cylinder pressures, customized valve timings or the compact design of cylinder heads can lead to an aggravation of the operational boundary conditions, which impose detrimental effects on the tribological contact pair of valve spindle vs. seat ring. Consequently, valve recession increases and lifetime decreases. The contact pair valve spindle/seat ring becomes more sensitive to the load collective, leading to unexpected failures of the engine. The first part of this contribution will deal with the wear behaviour of different hardfaced valve spindles obtained from engine tests. Stellite® 12 as well as Tribaloy®T400-hardfaced valve spindles of the same type from the same engine were comparatively analyzed with regard to valve recession, oxygen penetration depth and formation of a protective anti-wear tribofilm on the valve seating faces. As response to the load collective of contact, the severely worn sealing interfaces show no protective tribofilm whereas a wear-minimizing oxide film is observed on the valve seating faces showing low wear. The results from the engine tests were compared with prelimimary results from tests with the novel test rig - a valve spindle tribometer. In order to investigate the correlation of wear behavior and load parameters, the valve spindles were tested at various temperatures, atmospheres and valve closing velocities. Whereas the focus in the first phase is on inlet valves. By the use of an environmental chamber, a reliable and controlled atmosphere was ensured. From the comparison of engine tests with the lab-scale experiments, the measured linear wear rate of 2.2 µm/h is of the same magnitude as for the excessively worn valves of about 3.6 µm/h from engine test. Hence the test rig has proven that is able to produce wear rates those found in engine tests. Consequently, it establishes a research tool for study the wear mechanisms of valve closure and peak cylinder pressure in detail in a sustainable way.

【会议名称】

第28届CIMAC会议

【会议地点】

芬兰 赫尔辛基

【下载次数】

2

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