TS-55
Characteristic of Main Engine Specific Fuel Consumption on Sea Trial
Nozomu HABATA* and Toshiyuki NAKASHIMA**
ABSTRACT
Specific fuel consumption of main engine is one of the importanl index to evaluate ship's performance. During sea trial of diesel ships, some deviation in worse figure of specific fuel consumption from that of the shop trial has been observed. The specific fuel consumption is calculated with main engine output which is calculated with load index and engine speed according to the manufacturer's formulas including calorific value of fuel oil, running condition at sea and these at shop trial, however, the load index power is based on engine efficiency at shop trial. Therefore, it is considered that the load index power has not been corrected sufficiently and completely. On the other hand, at our sea trial, specific fuel consumption is calculated with engine output measured by shaft power meter. Up to now, it had commonly been understood that engine output calculated with load index had corresponded to that of shaft horse power meter. The authors were interested in existing of considerable deviation caused by those engine output. As a result of the investigation, characteristics and relationship of the both engine output power figures have been made clear, and it is explained that specific fuel consumption rate is become worse with approximately 5.2% in average on sea trial compare with shop trial depend on lowing of engine efficiency caused by kind of fuel oil and load fluctuation.
Key Words: Fuel Consumption, Sea Trial, Diesel Ship, Main Diesel Engine, Marine Diesel Engine
1. INTRODUCTION
Specific fuel consumption of main engine is important index to evaluate ship's performance and is fundamental figure of running cost in her fleet services. According to our actual results of diesel ships, during sea trial carried out before ship's delivery, some deviation in worse figure of specific fuel consumption from that of the shop trial records has been frequently observed.
Generally, the specific fuel consumption is calculated with main engine output which is calculated with load index (pump mark) and engine speed (rpm) to the engine manufacturer's formulas, however, the load index power is based on engine efficiency at shop trial. Therefore, the load index power is corrected with calorific value of fuel oil and running condition at sea and these at shop trial.
On the other hand, at our sea trial, specific fuel consumption is calculated with engine output measured by shaft horse power meter fitted on intermediate shaft. Up to now, it had commonly been understood that engine output calculated with load index had corresponded to that of shaft horse power.
This paper reports some investigation results for existing of considerable deviation, characteristics and relationships of the both main engine output power figures.
2. ACTUAL CONDITION FOR RELATIONSHIP OF LOAD INDEX POWER AND SHAFT HORSE POWER
To make clear the actual condition of the both engine output power, sea trial results were analyzed. Recent trial results of twenty-one examples are shown in Figure 1. Horizontal scale shows the nominal operation rating (NOR) of the main engine, and vertical scale shows difference with percentage between load index power and shaft horse power.
Scattering from 0 to 12% is observed, however, it is confirmed that shaft horse power is smaller than load index power with 5.2% in average.
