Design and experimental study on the Urea-SCR converter exhaust system of the marine diesel engine

Transcription

1 Applied Mechanics and Materials Online: ISSN: , Vols , pp doi: / Trans Tech Publications, Switzerland Design and experimental study on the Urea-SCR converter exhaust system of the marine diesel engine Lei Jiang 1,a Jun Huang 2,b 1 School of Energy and Power Engineering, Jiangsu University of Science and Technology, Zhenjiang Jiangsu , China 2 Jianbi Power Plant,Guodian Corporation,Zhenjiang ,China a jiang974212@163.com, b huangjun0722@126.com Keywords: diesel engines, emission control, SCR, catalytic converters, back pressure Abstract. 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. Introduction Recent years, with the world on diesel vehicle emissions regulations become increasingly stringent, which greatly promoted the development of engine technology, in order to achieve the EuroⅣ even EuroⅤ standard cars with diesel engine SCR technology widely used in Europe with good effect[1-4]. The emission control on diesel engine exhaust would be more and more strictly, and this trend will from land to ocean: The IMO 62nd Marine Environment Meeting held in London in 2011 and the meeting through the NOx technology rules (NOx Code amendment) and the system guideline of Selective Catalytic Reduction (SCR guideline, Selective Catalytic Reduction). The China diesel engine manufacturing or shipyard s influence is enormous. With the constantly new area is designated as ECA (Emission Control Area) means that more and more ships need to be installed to achieve the requirements of Tier III diesel engine, currently just SCR systems to meet the requirements of mature products[5]. Foreign manufacturers, the ship owners and research institutions as early as in the late 1980s began the SCR's research, and more than ten years experience in real vessel. According to the report, the Japanese NYK company has already successfully completed the first for the large-scale low-speed diesel engine matching SCR system sea trial in June last year. The share of global monopoly position of MAN company also in its large-scale low-speed diesel engine (7000 kw) installed the SCR system for the first time. Domestic manufacturing about marine SCR products in the country is basically in a blank period, which means that existing traditional designs such as diesel engines equipped with SCR systems require improvements. For example, in the cabin of the SCR system piping arrangement, a reducing agent, and the urea storage corresponding adjustment[5-6]. The paper taking a shipyard which build a 3900t Multi Purpose Offshore Vessel as the object of study, design the vessel s diesel engine-electric propulsion system with Urea-SCR catalysts exhaust system and test it. All rights reserved. No part of contents of this paper may be reproduced or transmitted in any form or by any means without the written permission of Trans Tech Publications, (ID: , Pennsylvania State University, University Park, USA-12/05/16,07:50:04)

2 1890 Advances in Energy Science and Technology SCR catalytic converter pressure loss analysis A shipyard DP3 positioning 3900t offshore operations vessel with a diesel engine-electric propulsion system, a total of four four-stroke turbocharged diesel engine, the speed 1800rpm single output electric power of about 1750 kw total output of electric power of about 7000 kw. Urea-SCR catalytic converters must be installed in accordance with the requirements of the owner, however, the SCR catalytic converter in the exhaust system installed will cause larger exhaust backpressure, the engine of the economy and power[7-9]. The typical car with the structure of the catalytic converter is shown in Fig.1. It is mainly from the inlet tube, the extension tube, the carrier, composed contraction and outlet pipes. The catalytic converter pipe pressure loss can be divided into two categories: loss along the way and partial loss. Along loss is the energy loss caused due to the viscous force of the airflow; Local loss due to air micelle a collision, produce whirlpool causes such near pipeline within the scope of the local energy loss. Fig.1 Structure diagram of the catalytic converter Among them, the expansion tube and shrinkage tube local loss and local resistance coefficient, volume quality and flow rate is proportional to the square of the. More commonly used method is processing Catalytic Converter anisotropic porous medium, the resistance along the way of the overall loss is calculated by Darcy's law[10]. 2 l ρv Reλ µ lv p= λ = (1) d 2 2 d H 2 H Where, λ is the coefficient of loss along the way, can be calculated according to the formula of Nikuradse[11]; ρ as the volume of fluid quality, kg/m 3 ; µ is the fluid dynamic viscosity (pore density), Pa/s -1 ; l is the length of the carrier conduit, mm; d H is pore hydraulic diameter, mm; v means airflow velocity, m/s; Re is the Reynolds number. To steady state flow, have the following Renault average quality, momentum conservation equation: ( σuj ) = 0 xj (2) p ( σuu j i τij ) = + si xj xi (3)

3 Applied Mechanics and Materials Vols Where, si is catalyst carrier resistance; τij is stress, the Newtonian flow are: 1 uk τ ij = 2 µ ( sij δij ) σuu i j 3 x k (4) s ij 1 u uj ( i = + ) 2 x x j i (5) Where, σ uu i j is Reynolds stress; sij is fluid deformation rate; The κ ε turbulence model calculation Reynolds stress to control the flow control equation, the empirical coefficient are shown in [12]. Using sofeware (Star-CD) to solve the flow control equations. Using the finite volume difference method to deal with the discrete equation of steady incompressible fluid, then use SIMPLE algorithm. The design of exhaust system The catalytic reactor is installed on a separate platform and is erected on a special steel support. The reactor casing must be disconnected from engine and exhaust gas system vibrations by means of flexible support elements and compensators. To cope with the heat extensions of components exposed to elevated temperatures extension is defined allowed in certain places, shown in Figure2. Fig.2 SCR reactor used on the boat The flow-in hood is the connection between the waste gas steel tube and reactor casing, and has a steadily enlarging diameter. The reactor casing is reinforced by fins. It is a self-bearing, gastight steel casing that compensates for the weight forces and flow resistance of the SCR and Oxidation catalyst modules and protects them against mechanical damages. To ensure easy installation and removal of catalytic components, we chose the modular design. As regards this design, individual catalytic honeycombs are combined to larger units, several levels of which are each time installed at once in the reactor. This method permits the complicated installation of individual, ceramic honeycombs being avoided in favor of a rapid, problem-free and safe modular installation.

4 1892 Advances in Energy Science and Technology According to the ship building requirements, bridge must be designed in any position are allowed to have joint 360 degrees of vision. But as a result of main engine room is set in front of the ship. So diesel exhaust pipe can't according to traditional designs to direct pass the main deck, or smoke will keep out bridge field of vision. Therefore, the diesel engine exhaust pipe designed through the side discharge (Fig.3), this scheme risk lies in will improve exhaust back pressure which would reduce diesel engine performance. The design of exhaust system have been tested and modify. Furthermore, in order to prevent water splash into exhaust pipe which have been installed board valve (Fig.4). Fig.3 The design of the exhaust pipe style Fig.4 Board valve upper outlet Experiment research According to the Fig.3, four temperature and pressure sensors which manufactured by the company of EMTECK are installed inside the exhaust pipe. The test is done based on as following: the temperature inside the engine room is 20, the relative humidity is 65%, and ventilation inside engine room is very adequate. Four diesel engines are tested respectively, and only one engine is running at the same time. Take respectively 50%, 75%, 90%, 100% and 110% loading of generator point to test, test diesel engine s fuel consumption and exhaust temperature performance indexes such as ship could meet the design requirements. In the first test, the exhaust back pressure, exhaust temperature and fuel consumption are can't meet the design index, so again to silencer and board valve size was calculated, modify, and test. Test results are shown in Fig.5, Fig.6 and Fig.7. Fig.5 Schematic diagram of the pressure within the various conditions of the exhaust system modification

5 Applied Mechanics and Materials Vols Fig.6 Exhaust temperature contrast diagram Fig.7 Fuel consumption compared schematic diagram The Fig.5 shown the exhaust system after modification pipe after pressure distribution were obviously improved in all loading generator. The Fig.6 shown the exhaust temperature also has a substantial decline; Through the Fig.7 we conclude the fuel consumption has decreased, and the decline range is about 5%. These are in line with the wear design index shows modification is successful. Concluding remarks 1) Catalyst of the pressure loss is mainly composed of carrier along the path loss and expansion pipe, shrinkage tube local loss composition. The carrier on-way resistance loss is the main reason for the loss caused by pressure. 2) Through the test can learn, install the exhaust gas turbo charged diesel engine in the exhaust back pressure increase, diesel combustion is not full, the exhaust temperature rise, on diesel engine performance influence are negative influence. Can through the exhaust system redesigned to adjust exhaust back pressure, so as to achieve when the design of ship diesel engine - electric propulsion system can achieve performance parameters. Acknowledgements This work was financially supported by the advantages of Jiangsu Province disciplines (Naval Architecture and Marine Engineering). References [1] W. Müller, H. Ölschlegel, A. Schäfer, N. Hakim and K. Binder, Selective Catalytic Reduction Europe s Nox Reduction Technology. Future Transportation Technology Conference, June 23-25, 2003, Costa Mesa, California. [2] Rinie Van Helden, Ruud Verbeek, Frank Willems.Optimization of Urea SCR denox Systems for HD Diesel Engines[C].SAE Paper , [3] Maunula T, Lylykangas R. NOX reduction by urea in the presence of NO2 on metal substraed SCR catalysts for heavy-duty vehicles[c].jsae paper, [4] Ming Chen, Shazam Williams. Modeling and optimization of SCR-exhaust aftertreatment system[c].sae paper, [5] Marine diesel engine SCR Opportunity or Challenge? [R]. Ships and equipment, 2011, 5: [6] Ding hongxiang,weihaibo. Marine diesel engine SCR technology economic analysis [J]. world shipping, 2007, 30 (5) :41-42.

6 1894 Advances in Energy Science and Technology [7] DIAO A-i min, LIANG Weihua, LIU Zhen. Study on Influence of Inlet or Exhaust Back Pressure to Combustion Process Turbo charged of Diesel Engine[J]. Vehicle Engine, 2008, 176(6): [8] GUO Zhong-hai. The Sensitivity of Diesel to Exhaust Back-pressure Performance[J]. Internal Combustion Engines, 2010,4(8): [9] Duan Yuancai, Dong Yuanjia,Xue Yafan.Investingating of the Alternative Regime Characteristics for Turbocharging Diesel Engine under the High Exhaust Back Pressure[J]. Chinese Internal Combustion Engine Engineering, 1989,10(1): [10] Xin Zhe, Wang Shunxi, Zhang Yin, Li Zhaojing, Zhang Yunlong2, Yun Feng. Pressure loss of urea-scr converter and its influence on diesel engine performance[j]. Transactions of the CSAE, 2011,27(8): [11] Shuai Shijin, Wang Jianxin, Zhuang Renjun. Pressure losses in automotive catalytic converters[j]. J Tsinghua University (Sci & Tech), 2001, 41(4): (in Chinese with English abstract) [12] JEONG S J, KIM T H. CFD Investigation of the 3-Dimensional Unsteady Flow in the Catalytic Converter [C]. SAE Paper

7 Advances in Energy Science and Technology / Design and Experimental Study on the Urea-SCR Converter Exhaust System of the Marine Diesel Engine /