Marine Medium-speed Diesel Engine Research Articles

Applicability of the PEMS technique for simplified NO monitoring on board ships

Abstract The performance of a predictive emission monitoring system (PEMS) as a technique for NOx monitoring on medium speed marine diesel engines has been evaluated for 16 similar engines on four different ships. The PEMS function tested measured O2 concentration in the exhaust gas, engine load, combustion air temperature and humidity, and barometric pressure to calculate the NOx concentration. Emission measurements were carried out by means of a conventional continuous emission monitoring system (CEMS) and the measured NOx concentrations were compared with those calculated by the PEMS function. For 11 of the 16 engines, the average error between measured and calculated NOx concentration was Bearing in mind the performance criteria for using PEMS at land-based installations, the results from this study are promising. Viewed as a single data set of 56 h with 16 separate engine comparisons between CEMS and PEMS, the data set shows a relative accuracy of 14.5% i.e. within the 20% requirement of the US Environmental Protection Agency. In light of the increased interest and international guidelines for continuous NOx monitoring on board ships, the PEMS technique can offer a simple but cost-effective option.

Optimization of Fuel Injection Nozzles for the Reduction of NOx Emissions in Medium-speed Marine Diesel Engines(Diesel Engines, Performance and Emissions, NOx Strategies)

Numerical simulations and experiments have been carried out to investigate the effect of fuel injection nozzles on the combustion and NO_X formation processes in medium-speed marine diesel engines. Spray and combustion phenomena were examined numerically using FIRE code. Wave breakup and Zeldovich models were adopted to describe the atomization characteristics and NO_X formation processes. Spray visualization experiment was performed in the constant-volume high-pressure chamber to verify the numerical results on the spray characteristics such as spray angle and spray tip penetration. Time-resolved spray behaviors were captured by high-speed digital camera and analyzed to extract the information on the spray parameters. Numerical analysis of fuel injection system was also performed to get the profiles of fuel injection rate, which should be given as an input data for the combustion analysis. Numerical results were verified with experimental data such as cylinder pressure, ROHR (Rate of Heat Release) and NO_X emission. Finally, the effects of fuel injection nozzles on the engine performance were investigated numerically to find the optimum nozzle parameters such as fuel injection angle, nozzle hole diameter and number of nozzle holes. From this study, the optimum fuel injection nozzle (nozzle hole diameter, 0.32 mm, number of nozzle holes, 8 and fuel injection angle, 148°) was selected to reduce both the fuel consumption and NO_X emission. The reason for this selection could be explained from the highest fuel-air mixing in the early phase of injection due to the longest spray tip penetration and the highest heat release rate after 19° ATDC due to the increased injection duration.

On the Continuous Monitoring of Oil-Film Thickness in an Engine Bearing

This paper describes research involving the measurement of oil-film thickness in a large end bearing of a medium-sized medium-speed marine diesel engine. The design of the transducer and its novel signal conditioning circuitry is discussed. Comparisons are made between the measured results and numerical predictions.