Increasing exhaust temperature to enable after-treatment operation on a two-stage turbo-charged medium speed marine diesel engine

Nitrogen-oxides (NOx) are becoming more and more regulated. In heavy duty, medium speed engines these emission limits are also being reduced steadily: Selective catalytic reduction is a proven technology which allows to reduce NOx emission with very high efficiency. However, operating temperature of the catalytic converter has to be maintained within certain limits as conversion efficiency and ammonia slip are very heavily influenced by temperature. In this work the engine calibration and hardware will be modified to allow for a wide engine operating range with Selective catalytic reduction. The studied engine has 4MW nominal power and runs at 750rpm engine speed, fuel consumption during engine tests becomes quite expensive (+- 750kg/h) for a measurement campaign. This is why a simulation model was developed and validated. This model was then used to investigate several strategies to control engine out temperature: different types of wastegates, injection variation and valve timing adjustments. Simulation showed that wastegate application had the best tradeoff between fuel consumption and exhaust temperature. Finally, this configuration was built on the engine test bench and results from both measurements and simulation agreed very well

An optical study of evaporating fuel sprays for medium speed engines

Emission legislation for medium-speed marine engines are becoming more and more regulated to improve air quality. These engines differ from automotive engines in several ways: the combustion chamber is much bigger, combustion duration is longer and injection technology is different as well. One-D engine simulation code was unable to capture emission formation for all operating points. To improve the understanding of the combustion process with marine fuel injections, a constant volume combustion chamber was improved for repeatability and reliability. A database with variable ambient conditions was then measured. Finally, a simplified simulation model was employed to estimate local conditions in the spray

Modeling of a heavy duty diesel engine to ease complex optimization decisions

Engine optimization becomes more difficult every day, more and more limits regarding emissions of noxious components have to be met. Considering heavy duty marine engines such as the 6DZC from ABC there are several important instances: IMO III reduces NOx by 75% from 2021, EPA reduces NOx by 70% from 2016. Therefore very complex systems are implemented, which each have multiple calibration or working parameters. Some are fixed, some can change depending on engine load and speed. An example of a fixed parameter is compression ratio, it can only be changed while building the engine. Other fixed parameters include: choice of injection nozzle (#holes, hole-diameter), bore, stroke, etc. Exhaust gas recirculation (EGR) is a parameter that can be changed continuously during operation of the engine. Typically there are other parameters present: Variable Valve Timing, injection timing, injection duration, injection pressure, secondary injection, wastegate setting(s), etc. Ideally these parameters are configured in a way that the engine emits very little harmful components and fuel consumption is very low. The most straightforward approach would be to test every parameter combination, record emission components and fuel consumption and choose the optimal parameter combination. This has to be repeated for every speed and load of the engine, which results in an engine map. This method becomes more and more expensive, both in time as in fuel consumption because every additional operating parameter increases the amount of tests exponentially. This is why engine simulation becomes inevitable. Accurate engine simulation is able to exclude regions of parameter values that are clearly infeasible and can give a good indication where engine tests are more interesting

Evaluation of breakup models for marine diesel spray simulations

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The behavior of a simplified spray model for different diesel and Bio-Diesel surrogates

The need for simulation tools for the internal combustion engine is becoming more and more important due to the complex engine design and increasingly strict emission regulation. One needs accurate and fast models, but fuels consist of a complex mixture of different molecules which cannot realistically be handled in computations. Simplifications are required and are realized using fuel surrogates. The main goal of this work is to show that the choice of the surrogates is of importance if simplified models are used and that the performance strongly depends upon the sensitivity of the fuel properties that refer to the main model hypotheses. This paper starts with an overview of surrogates for diesel and bio-diesel as well as the motivation for choosing them. Next, a phenomenological model for vaporizing fuel-sprays is implemented to assess how well-known surrogates for diesel and bio-diesel affect the obtained results. The model was used to calculate the liquid length and the results show significant differences among the used surrogates. These differences are explained based on the spray model's hypotheses and the surrogate fuel properties. The sensitivity of the model on the spray angle was also studied, as this is an important input parameter but is mostly determined with a large experimental uncertainty

Investigation of evaporating sprays in a medium speed marine engine

The understanding of diesel sprays is very important to enable a better and cleaner marine engine design, but unfortunately little knowledge is openly available on marine engine fuel sprays. In this paper, evaporating sprays for medium speed marine engines were studied in a constant volume combustion chamber by performing optical measurements through Schlieren and Mie diagnostic techniques. The effects of ambient gas temperature and ambient gas density on vapor and liquid penetration were investigated by changing the target condition in the combustion chamber. A comparative study of two injectors with different nozzle diameters (0.38 mm and 0.44 mm) was also carried out at ambient density of 22.5 kg/m3. Some empirical correlations of spray penetration have been modified to fit the spray measurement data. Due to the transient characteristics of the pump-line-nozzle injection system, a time-dependent injection pressure profile is suggested for calculation of spray penetration. The spray tip penetration at large distance under low density (7.6 and 15.2 kg/m3) conditions is expected to be proportional to t2/3, which is supported by the model considering spray-induced gas turbulence effect. The t1/2 law, where turbulence is not taken into account, is still valid under high density (22.5 kg/m3) conditions with higher engine load. The comparison of two models demonstrates that the effect of gas turbulence is influenced by the ambient gas density and engine load

Evaluation of some important boundary conditions for spray measurements in a constant volume combustion chamber

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