CIMAC Congress - Schiff & Hafen

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<strong>CIMAC</strong> CONGRESS | BERGEN 2010 between Particulate Matter (PM) and NOx. The paper will first tell about previous studies in Helsinki University of Technology TKK and emission reduction in a standard heavy duty diesel engine. Then the studies in a corresponding single-cylinder research engine “EVE” will be presented. In the single-cylinder EVE engine advanced cycles like Miller cycle and interrnal exhaust gas recirculation (EGR) have been studied. Also the possible benefits of blending oxygenates with the fuels have been considered. The first part of the paper concentrates on high cetane number paraffinic diesel fuels and their oxygenate blends: previous studies on their properties and effect on engine emissions. The second part describes the ongoing research in Aalto University School of Science and Technology (previously TKK, Helsinki University of Technology). In the studies, potential for emission reduction has been estimated to be 70% or more and promising preliminary results have been reached in the first test runs. This study is part of “ReFuel”–project, which is an IEA collaborative task of IEA Combustion Agreement program and a collaboration framework between IEA Combustion Agreement and IEA AMF (Advance Motor Fuels) Agreement. EMI MIN – a government funded research program to reduce emissions U. Schlemmer-Kelling, S. Watzek, Caterpillar Motoren GmbH & Co. KG, Germany There is an ongoing worldwide legislative trend to reduce the emissions of medium speed diesel engines [1]. For this reason, a joint research program was established in 2002. Partners of the socalled EMI MINI program were AVL Germany, L’Orange, University of Rostock, WTZ and Caterpillar Motoren. The program was funded by the German Ministry of Economics. The development target was to reduce the emission of diesel engines by 50% without using aftertreatment solutions. Meanwhile, the second phase of this program (EMI MINI II) is nearly finished. The team worked to define the strategy [2] and the final solution was demonstrated on a multicylinder, turbocharged 6 M 32C engine in Kiel. Using the strategy, Caterpillar Motoren was able to reach the emissions target by tuning the combustion process. The fuel and air systems were modified to reduce NOx and soot emission for both steady state and transient operation. The major building blocks of the concept were a common rail fuel system which was able to operate under heavy fuel conditions and a flexible valve drive which allowed the Miller cycle to be turned on and off. A DoE tool was used to find the optimal settings for the injection system at each load point. With the strategy, a 50 % NOx reduction was achieved with invisible soot emission. However, a slight loss in fuel efficiency was also measured. A two-stage turbo charging system could be used to improve efficiency, but this was not within the program scope and was not tested. The simulation results have shown that the target of constant fuel efficiency can be achieved with the addition of two-stage turbo charging. 10:30 June 17th Room Troldtog (2–4) Fundamental Engineering – Piston Engines – Thermodynamics Advanced heat transfer modelling with application to CI engine CFD simulations M. Nuutinen, O. Kaario, M. Larmi, Aalto University School of Science and Technology, Finland The purpose of the work is to implement and further develop an advanced wall function formalism in conjunction with a modified low Reynolds number turbulence model in Star-CD, a CFD software suitable for in-cylinder flow and conjugate heat transfer simulations. This advanced method has already been demonstrated to give predictions superior to standard methods when compared to measured heat transfer values and DNS data in strongly heated compressible flows, Nuutinen et al. [1]. Besides superior accuracy, the advanced method has a desirable feature of being free from the near wall grid resolution restrictions associated with the low and high Reynolds number turbulence models. The acquired computational tool is then used to simulate conjugate heat transfer in realistic compression ignition (CI) engines. The manufacturers of large CI engines are striving for increasing cylinder pressures which in turn results in elevated heat transfer rates and surface temperatures. As a consequence, accurate heat transfer simulation is becoming increasingly important. With the new computational tool it is possible to obtain more accurate results on heat transfer that can be utilized in engineering processes, e.g., in material choices and geometry design. In addition to improving the overall accuracy of simulations (energy balance) the more accurate temperature and heat flux predictions may be further utilized, e.g., to simulate thermal stresses in solid engine parts and heat transfer to the coolant. Piston surface heat transfer during combustion in large marine diesel engines M. V. Jensen, J. H. Walther, Technical University of Denmark, Denmark In the design process of large marine diesel engines information on the maximum heat load on the piston surface experienced during the engine cycle is an important parameter. The peak heat load occurs during combustion when hot combustion products impinge on the piston surface. Although the maximum heat load is only present for a short time of the total engine cycle, it is a severe thermal load on the piston surface. At the same time, cooling of the piston crown is generally more complicated than cooling of the other components of the combustion chamber. This can occasionally cause problems with burning off piston surface material. In this work the peak heat load on the piston surface of large marine diesel engines during combustion was investigated. Measurements of the instantaneous surface temperature and surface heat flux on pistons in large marine engines are difficult due to expensive instrumentation and high engine running costs compared to automotive engines. Therefore the investigation in this work was carried out numerically with the use of a computational fluid dynamics (CFD) code. At the same time, numerical work on detailed in-cylinder wall heat transfer in engines has been quite limited. The numerical investigation focused on the simulation of a hot turbulent gas jet impinging on a wall under very high pressure, thus approximating the process of the actual impingement of hot combustion gasses on the piston surface during combustion. The surface heat flux at the wall was calculated under different conditions in the numerical setup in order to obtain information of the actual peak heat flux experienced at the piston in large marine diesel engines during combustion. The variation of physical parameters influencing the heat transfer during combustion included a variationof pressure, temperatures, jet velocity and jet turbulence intensity. The variation in heat flux predictions resulting from application of different turbulence models was also investigated by performing calculations with three different models: the V2F model, a k-ε RNG model and a low-Re k-ε model. The obtained results indicate peak heat fluxes in the order of 5−10MW/m 2 on the piston surface during the combustion phase of the engine cycle. 92 Ship & Offshore | 2010 | No. 3
Monday, 14 June Tuesday, 15 June Wednesday, 16 June Thursday, 17 June Combining dual stage turbocharging with extreme Miller timings to achieve NOx emissions reductions in marine diesel engines F. Millo, M. Gianoglio, Politecnico di Torino, Italy, D. Delneri, Wärtsilä, Italy In this work, the potential of extreme Miller cycles, combined with two stages turbocharging, was analyzed by means of 1-D simulation code for a Wärtsilä six cylinder 4-stroke medium speed diesel engine. By means of extreme Miller timings, with Early Intake Valve Closures (up to 100 crank angle degrees before BDC), followed by an in-cylinder expansion of the charge during the last portion of the intake stroke, lower temperatures at the start of injection can be obtained, and thanks to the cooler combustion process, the NOx specific emissions can be efficiently reduced. However, the reduction of the effective intake stroke demands high intake manifold pressures, exceeding single stage turbocharging capabilities, and mandatory requiring dual stage turbo charging. Since turbines and compressor efficiencies, as well as the pressure ratio between HP and LP stages are crucial factors for a successful application of the extreme Miller timings, a careful selection of the more suitable turbomachines is extremely important. The use of numerical simulation allows indeed a detailed and extensive evaluation of the effects on engine performance, fuel consumption, NOx emissions and thermal and mechanical loads on engine components of the combination of different intake valve profiles and intake valve closure timings with different boost levels. Moreover, aiming to achieve further reduction in NOx emissions, different valve overlap values were also evaluated, trying to reduce the engine scavenging effect and increase the internal EGR. By combining early intake valve closures with reduced overlaps higher exhaust gas residuals in the combustion chamber were achieved, further reducing NOx emissions. Boost pressures up to 12 bar were evaluated that combined with extreme Miller timings (up to 100 crank angle degrees before BDC) allowed up to 50 % NOx reduction compared to conventional, single stage turbocharger architecture, with only moderate BSFC worsening. 10:30 June 17th Room Klokkeklang (5–3) Component & Maintenance Technology – Piston Engines – Noise & Vibration Noise reductions for low speed diesel engines and application of noise measurement using spherical beamforming technique S. Kajihara, Mitsui Engineering and Shipbuilding Co., Ltd., Japan, K. Takashima, Nittobo Acoustic Engineering Co., Ltd., Japan, J. Hoejgaard, M. Roegild, MAN Diesel & Turbo SE, Denmark The noise level in engine rooms of general merchant ships is relatively higher than in other facilities for transportation. In the engine room, the noise from a main engine, mainly of low speed diesel types, greatly influences noise levels. Actually at some positions on large bore engines with big turbochargers, it is not rare for the noise level to reach close to the IMO requirement of 110 dB(A). Under such situations, various efforts have been done to reduce the noise level aiming towards the improvement of livability and also work environment of the crew in engine room. In this paper, firstly, we report a noise characteristic of low speed diesel engine and also the present status of the noise level in the engine room. Secondly, we report some samples of the countermeasures for noise reduction including the application of Helmholtz resonators and absorption materials. Finally, we report on the newly introduced spherical beamforming technique with its principle and effectiveness in noise measurement. Contents: 1. Present noise measurement methods and IMO noise requirements for engine room 2. Noise characteristics of low speed diesel engine Usually, noise level is measured higher at the scavenging area, that is, around the turbocharger, air cooler, scavenging pipe and its connection part. The dominating sound source are the turbochargers, especially the compression noise. It’s caused by the recurring compression shocks and emitted as air born sound through the air intake silencers on the one hand but also trough to high-pressure-side (compressor outlet) over the connected pipes (like expansion bellow, air cooler, scavenging air pipe). The frequency spectrum is dominated by the compressor wheels blade passing frequency and (in some cases) his first harmonic. It corresponds with the number of main blades multiplied by the turbocharger rotor speed (and twice that frequency). 3. Countermeasures of low speed diesel engine noise The countermeasures are mainly applied in the turbocharger and the scavenging area. We report the present countermeasures and their effects in noise reduction such as introducing low noise turbochargers and additional insulation of diffuser pipes between the turbocharger compressor outlets and air coolers and scavenging air pipes. Further, we report new countermeasures and confirmation test results as follows. Example 1: Silencers of Helmholtz resonators and absorption materials M/E Mitsui-MAN B&W 11K98MC (62,920kW x 94rpm), T/C 3 x ABB TPL85B for a 6350 TEU container vessel: The countermeasures consisted of resonance type silencers (called CoRes) designed by ABB in the expansion bellow between the turbocharger compressor outlet and diffuser pipe and inside noise absorption in the area above the air cooler elements (called CABS). Example 2: New Silencers of Helmholtz resonators M/E Mitsui-MAN B&W 12K98MC(68,640kW x 94rpm), T/C 3 x MAN TCA88 for an 8250 TEU container vessel: The new resonance type silencers designed by MAN Diesel were located at diffuser pipes. Test results will be reported. 5. New noise measurement by using spherical beamforming technique The noise measurement technique using spherical beamforming has been developed for identifying and visualizing the noise sources as well as analyzing their characteristics (frequencies and levels) within a very short time. This technique has been recently used for investigations of noise sources for automobiles, etc. New low noise solutions for medium speed diesel engines H. Tienhaara, M. Aura, S. Jussila, Wärtsilä Finland Oy, Finland, F. Degano, Wärtsilä Italia S.p.A, Italy, A. Karjalainen, Machinery Acoustics Oy, Finland Customer requirements and excpectations of engine room noise and its characteristics are increasing importance. This is No. 3 | 2010 | Ship & Offshore 93
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