Technical Challenge for the 2-Stroke Premixed Combustion Gas Engine (Pre-ignition Behavior and Overcoming Technique)
In recently, emission legislations are gradually strengthened for marine engines. A gas engine fueled LNG is in the spotlight due to simplify an exhaust gas after-treatment and reduce GHG emission. 2-stroke slow speed engines are preferred for propulsion of large vessels due to high power, slow speed, and high reliability. Unfortunately, most commercialized gas engines have been 4-stroke medium speed engine due to technical difficulties of 2-stroke slow speed gas engine. To realize the 2-stroke slow speed premixed gas engine, a technological breakthrough is needed. The new concept of 2-stroke slow speed premixed gas engine is verified by engine test with 1-cylinder modified to gas engine configurations from a normal 2-stroke slow speed diesel engine. In this engine test, pre-ignition phenomenon is observed under specific conditions which are at higher Mean Effective Pressure. Pre-ignition leads to high maximum cylinder pressure and high NOx emission due to uncontrollable ignition timing by pilot fuel injection. In a combustion chamber of reciprocating engines, the lubrication oil is indispensable to maintain sliding condition between piston and cylinder liner and existing. This paper shows that influence of cylinder lubrication oil to pre-ignition is realized by in-cylinder visualization with a high speed camera and endoscope. Luminescence intensity and the number of auto-ignition flames are reduced by reduction of cylinder lubrication oil. In addition, this paper describes the effects of temperature, equivalence ratio of pre-mixture, and characteristics of lubrication oil on ignition behavior from fundamental test results. This fundamental test is carried out by Rapid Compression and Expansion Machine. RCEM can simulate the high temperature and high pressure condition of actual engine. The fundamental test results show that temperature reduction technique is not enough to avoid the pre-ignition because the auto-ignition temperature of lubrication oil is similar to the ignition temperature of pilot fuel. However, lean pre-mixture reduces ignition probabilities of pre-mixture induced by auto-ignition of lubrication oil. Moreover, this pre-mixture can be ignited by micro pilot fuel in this lean pre-mixture condition. In this suitable condition, it is possible to avoid pre-ignition and misfire. This paper clarifies that controlling the premixture equivalence ratio within the suitable condition is important for stable operation of the 2-stroke premixed gas engine without pre-ignition caused by autoignition of lubrication oil.
Takayuki Hirose Yutaka Masuda Takeshi Yamada Yoshiyuki Umemoto Hirohide Furutani
DIESEL UNITED,LTD.,Japan IHI Corporation,Japan National Institute of Advanced Industrial Science and Technology,Japan
国际会议
上海
英文
1-10
2013-05-13（万方平台首次上网日期，不代表论文的发表时间）