Nitrogen Oxides Reduction Effect and the Influence Mechanism of Exhaust Valve Lift on a Two-Stroke Marine Diesel Engine

2019 ◽  
Vol 141 (8) ◽  
Author(s):  
Lijiang Wei ◽  
Anmin Wu ◽  
Jie Liu ◽  
Mingliang Zhong ◽  
Xuebai Wang
Keyword(s):  
Diesel Engine ◽  
Nitrogen Oxides ◽  
Exhaust Valve ◽  
Marine Diesel Engine ◽  
Nox Emissions ◽  
Exhaust Gas ◽  
Nox Formation ◽  
Influence Mechanism ◽  
Marine Diesel ◽  
Reduction Effect

For the two-stroke marine diesel engine, the action of exhaust valve has a significant impact on scavenging and combustion processes and ultimately affects the engine performances and emissions. In order to reduce nitrogen oxides (NOx) emissions of a two-stroke marine diesel engine, different exhaust valve lifts (EVLs) were achieved by computational fluid dynamics simulation method in this study. The NOx reduction effect and influence mechanism of EVL on a two-stroke marine diesel engine were investigated in detail. The results showed that the in-cylinder residual exhaust gas and the internal exhaust gas recirculation (EGR) rate gradually increased with the decreasing EVL. Although the total mass of charge enclosed in the cylinder did not change much, the composition changed gradually and the maximum internal EGR rate reached 13.17% in this study. The maximum compression pressure and combustion pressure both rose first and then decreased with the decreasing EVL. While the start of combustion and the maximum combustion temperature were basically unaffected by EVL, the indicated power of the engine was also not much impacted when the EVL was changed from increasing 10 mm to decreasing 20 mm. The indicated specific fuel consumption first declined slowly and then rose rapidly as the EVL reduction exceeded 20 mm. NOx emissions decreased monotonously with the decreasing EVL. The reduction of NOx formation rate and the amount of NOx formation mass mainly occurred at the middle and late stages of combustion for the downward moving of residual exhaust gas. NOx emissions were reduced by 12.57% without compromising other engine performances at medium-reduced EVL in this study. However, in order to further reduce NOx emissions at low EVLs, other measures may be needed to make the residual exhaust gas more evenly distributed during the initial stage of combustion.

Analysis on Sealing and Deformation of Exhaust Valve Housing of Marine Diesel Engine

2013 ◽  
Vol 690-693 ◽  
pp. 1887-1890
Author(s):  
Ji Wu ◽  
Shu Lin Duan ◽  
Zhan Hua Wu ◽  
Hui Xing ◽  
Wen Chun Zhang
Keyword(s):  
Diesel Engine ◽  
Simulation Method ◽  
Exhaust Valve ◽  
Marine Diesel Engine ◽  
Exhaust Gas ◽  
Total Deformation ◽  
Maximum Deformation ◽  
Marine Diesel ◽  
Bolt Pretension ◽  
Valve Housing

MAN Diesels 6S50MC-C disel is a two-stroke marine diesel engine. Preload of the exhaust valve component is applied in four bolts. The preload of bolts can improve the fatigue strength of the exhaust component. In addition, the bolt pretension ensure the sealing in the maximum firing pressure. Using of simulation method, the displacement and deformation of exhaust valve component are analyzed when the maximum firing pressure and preload are applied. By analysis of the deformation of the exhaust valve housing under different preload force, the deformation of exhaust valve housing increase with the increaseing of preload. The maximum total deformation is 0.40mm in the preload of 720KN. The maximum deformation occurs in the region near the bolt in the side of exhaust gas outlet. The deformation in the direction of Y-axis of exhaust valve housing is along the Y-axis opposite direction when the preload is greater than 540KN. This indicates that the exhaust valve seal well. The sealing and deformation of the exhaust valve component meets the desgin requirement.

Validation of Multi-Zone Combustion Model Ability to Predict Two Stroke Diesel Engine Performance and NOx Emissions Using on Board Measurements

2012 ◽  
Author(s):  
Dimitrios T. Hountalas ◽  
Georgios N. Zovanos ◽  
David Sakellarakis ◽  
Antonios K. Antonopoulos
Keyword(s):  
Particulate Matter ◽  
Diesel Engine ◽  
Nox Reduction ◽  
Engine Performance ◽  
Combustion Model ◽  
Marine Diesel Engine ◽  
Nox Emissions ◽  
Exhaust Gas ◽  
Slow Speed ◽  
Marine Diesel

Diesel engines are almost exclusively used for propulsion of marine vessels. They are also used for power generation either on vessels or power stations because of their superior efficiency, high power concentration, stability and reliability compared to other alternative power systems. However, a significant drawback of these engines is the production of exhaust gases some of which are toxic and thus can be a threat to the environment. The most important toxic gaseous pollutants found in the exhaust gas of a marine diesel engine are NOx (NO, NO2 etc), CO and SOx. Particulate matter is also a major pollutant of diesel. Currently CO2 is considered to be also a “pollutant”, even though not being directly toxic, due to its impact on global warming. In the Marine sector there exists legislation for marine diesel engine NOx emissions which is getting stricter as we move on towards Tier III. This brings new challenges for the engine makers as far as NOx control and its reduction is concerned. Towards this effort of NOx reduction, modelling has an important role which will become even more important in the future. This is mainly attributed to the large size of marine engines which makes the use of experimental techniques extremely expensive and time consuming. Modelling can greatly assist NOx reduction efforts at least at the early stages of development leading to cost reduction. As known NOx emissions are strongly related to engine performance and thus efforts for their reduction usually have a negative impact on efficiency and particulate matter. Modelling can play an important role towards this direction because optimization techniques can be applied to determine the optimum design for NOx reduction with the lowest impact on efficiency. At present an effort is made to apply an existing well validated multi-zone combustion model for DI diesel engines on a 2-stroke marine diesel engine used to power a tanker vessel. The model is used to determine both engine performance and NOx emissions at various operating conditions. To validate model’s ability to predict performance and NOx emissions, a comparison is given against data obtained from the vessel official NOx file and from on board measurements conducted by the present research group. On board performance measurements were conducted using an in-house engine diagnostic system while emissions were recorded using a portable exhaust gas analyzer. From the comparison of measured against predicted data, the ability of the model to adequately predict performance and NOx emissions of the slow speed 2-stroke marine diesel engine examined is demonstrated. Furthermore, from the application are revealed specific problems related to the application of such models on large slow speed two-stroke engines which is significantly important for their further development.

Design and Experimental Study on the Urea-SCR Converter Exhaust System of the Marine Diesel Engine

2013 ◽  
Vol 291-294 ◽  
pp. 1889-1894
Author(s):  
Lei Jiang ◽  
Jun Huang
Keyword(s):  
Experimental Study ◽  
Diesel Engine ◽  
Pressure Loss ◽  
Catalytic Converter ◽  
Exhaust System ◽  
Marine Diesel Engine ◽  
Exhaust Gas ◽  
Marine Diesel ◽  
New Type ◽  
Design Requirements

Urea-SCR catalytic converter can effectively reduce the NOx emission of diesel engines, but meanwhile catalytic converter will cause some pressure loss in the exhaust system, which has negative influences on the engine performances. In this paper, the method of theoretical analysis calculated the pressure loss of the SCR catalytic converter, and designing a new type of exhaust gas pipe. Through the test to meet the design requirements,the results can provide a reference for optimum design of SCR catalytic converters and assembling.

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