Increasing the Accuracy of a Marine Diesel Engine Operation Limit by Thermal Factor

Marine diesel engines usually operate on a highly boosted intake pressure. The reciprocating feature of diesel engines and the continuous flow operation characteristics of the turbocharger (TC) make the matching between the turbocharger and diesel engine very challenging. Sequential turbocharging (STC) technology is recognized as an effective approach in improving the fuel economy and exhaust emissions especially at low speed and high torque when a single stage turbocharger is not able to boost the intake air to the pressure needed. The application of STC technology also extends engine operation toward a wider range than that using a single-stage turbocharger. This research experimentally investigated the potential of a STC system in improving the performance of a TBD234V12 model marine diesel engine originally designed to operate on a single-stage turbocharger. The STC system examined consisted of a small (S) turbocharger and a large (L) turbocharger which were installed in parallel. Such a system can operate on three boosting modes noted as 1TC-S, 1TC-L and 2TC. A rule-based control algorithm was developed to smoothly switch the STC operation mode using engine speed and load as references. The potential of the STC system in improving the performance of this engine was experimentally examined over a wide range of engine speed and load. When operated at the standard propeller propulsion cycle, the application of the STC system reduced the brake specific fuel consumption (BSFC) by 3.12% averagely. The average of the exhaust temperature before turbine was decreased by 50°C. The soot and oxides of nitrogen (NOx) emissions were reduced respectively. The examination of the engine performance over an entire engine speed and torque range demonstrated the super performance of the STC system in extending the engine operation toward the high torque at low speed (900 to 1200 RPM) while further improving the fuel economy as expected. The engine maximum torque at 900 rpm was increased from 1680Nm to 2361 Nm (40.5%). The average BSFC over entire working area was improved by 7.4%. The BSFC at low load and high torque was significantly decreased. The application of the STC system also decreased the average NOx emissions by 31.5% when examined on the propeller propulsion cycle.

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Impact of Compressor Surge on Performance and Emissions of a Marine Diesel Engine

Journal of Turbomachinery ◽

10.1115/1.4033186 ◽

2016 ◽

Vol 138 (10) ◽

Cited By ~ 6

Author(s):

Nikolaos-Alexandros Vrettakos

Keyword(s):

Steady State ◽

Diesel Engine ◽

Engine Performance ◽

Marine Diesel Engine ◽

Performance Parameters ◽

Test Bed ◽

Engine Operation ◽

Compressor Surge ◽

Marine Diesel ◽

The Impact

The operation during compressor surge of a medium speed marine diesel engine was examined on a test bed. The compressor of the engine's turbocharger was forced to operate beyond the surge line, by injecting compressed air at the engine intake manifold, downstream of the compressor during steady-state engine operation. While the compressor was surging, detailed measurements of turbocharger and engine performance parameters were conducted. The measurements included the use of constant temperature anemometry for the accurate measurement of air velocity fluctuations at the compressor inlet during the surge cycles. Measurements also covered engine performance parameters such as in-cylinder pressure and the impact of compressor surge on the composition of the exhaust gas emitted from the engine. The measurements describe in detail the response of a marine diesel engine to variations caused by compressor surge. The results show that both turbocharger and engine performance are affected by compressor surge and fast Fourier transform (FFT) analysis proved that they oscillate at the same main frequency. Also, prolonged steady-state operation of the engine with this form of compressor surge led to a non-negligible increase of NOx emissions.

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The time of the first transition of the semi-Markov process in the evaluation of diesel engine operation

Combustion Engines ◽

10.19206/ce-117106 ◽

2011 ◽

Vol 145 (2) ◽

pp. 89-98

Author(s):

Jacek RUDNICKI

Keyword(s):

Diesel Engine ◽

Markov Process ◽

Markov Processes ◽

Marine Diesel Engine ◽

Engine Operation ◽

Marine Diesel ◽

Semi Markov Process ◽

Deterioration Process ◽

Semi Markov Processes ◽

Engine Reliability

The paper presents the extension of the method discussed in the literature of quantitative evaluation of operation on the example of a marine engine. According to this interpretation, the engine operation can be shown as a physical quantity. In this aspect, based on the main marine diesel engine an evaluation of the usefulness of this index for the description of the engine reliability related properties has been performed. Apart from the generally used reliability indexes, it seems purposeful to consider the engine operation (as well as its functional subsystems) in the evaluative way, so that it could be described by both energy and time. In this aspect, in the analysis the semi-Markov processes theory was used that allowed a description of the concept of the model of the engine deterioration process as a random one. The problem of the time of the first transition of the semi-Markov process to a subset of specified classes of states representing particular technical and reliability-related states of engine was described in detail.

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