Feature 2 | HIGH-SPEED DIESEL ENGINES
Power density and enviro factors drive development
Tougher limits on pollutant exhaust emissions for vessels and craſt governed by US and EU environmental controls, in concert with heightened demands from operators for improved power density, unit fuel efficiency, and reliability, have motivated many new developments in the high-speed diesel sector, writes David Tinsley.
ical tools, and the increased integration of electronics, are having a signal bearing on enhanced engine performance levels. MTU Friedrichshafen has hoisted the
N
power rating of its 20-cylinder series 8000 common-rail engine by 11%, taking the high-speed diesel category to a new level of potency. Compared with the 8200kW obtained from the engine in its M70L version, the new M71 genera- tion gives a maximum continuous output of 9100kW in its M71L model, at the unchanged running speed of 1150rev/min. Te 20V 8000 M70 diesel engine was
released for commercial marine applica- tions in 2001, and the latest development programme was spurred by customer demand for higher power densities, plus low specific fuel consumption, and clean exhaust under rapid load changes, as well as at full power and low speeds. In addition to consideration of evolving market requirements and rising engine performance expectations, the uprating project was launched with a view to the advent of stricter exhaust emission limits in the future. Te enhanced design, 20V 8000 M71,
has been released in three versions, at 7200kW, 8200kW, and 9100kW power ratings with improved emission characteristics. Te 11% increase in power output from
the same cylinder capacity and engine speed was obtained by raising the brake mean effective pressure. To avoid an increase in thermal load on the engine as compared with the previous version, the
26 The M71 generation of 20V 8000 high-speed diesel engines, built by MTU.
charge-air pressure was raised by develop- ing the turbocharging system. At rated power, the charge air pressure reaches 4.1bar, delivered by single-stage sequential turbocharging. The high, maximum permissible
combustion pressure of 230bar provides sufficient possibilities for a high compres- sion ratio. Tis ensures that the starting and idling characteristics of the higher- powered, new engine model are equally favourable as those of the previous model. MTU is a practitioner of computer-
aided 3D combustion modelling, which assists precision and saves time in the development process. By such means, flows, temperatures, and heat conduction can be simulated with a high degree of accuracy, and computer-based optimisa- tion can be accompanied by verification of the computed results on a single-cylinder
test engine. Among the first M71 engines in service
are the prime movers in two Austal Auto Express-type 88m catamaran ro-ro passenger ferries deployed by Istanbul operator IDO. The installation in each vessel comprises four of the 20-cylinder engines in M71R guise, to give an overall plant output of 28,800kW at 1150rev/min. Apart from the consumption-optimised
variant, the 20V8000 M71 engine is also available as an emission-optimised, EPA Tier 2 version. Te wide engine perform- ance map, and the broad speed range in which the maximum power is available, suit the engine type to various propulsion solutions in fast vessels.
The next series With a view to US EPA Tier 2 emission requirements and the next IMO emission
Ship & Boat International May/June 2008
ew design attention to the combustion process, aided by technologically-advanced analyt-
Page 1 |
Page 2 |
Page 3 |
Page 4 |
Page 5 |
Page 6 |
Page 7 |
Page 8 |
Page 9 |
Page 10 |
Page 11 |
Page 12 |
Page 13 |
Page 14 |
Page 15 |
Page 16 |
Page 17 |
Page 18 |
Page 19 |
Page 20 |
Page 21 |
Page 22 |
Page 23 |
Page 24 |
Page 25 |
Page 26 |
Page 27 |
Page 28 |
Page 29 |
Page 30 |
Page 31 |
Page 32 |
Page 33 |
Page 34 |
Page 35 |
Page 36 |
Page 37 |
Page 38 |
Page 39 |
Page 40 |
Page 41 |
Page 42 |
Page 43 |
Page 44 |
Page 45 |
Page 46 |
Page 47 |
Page 48 |
Page 49 |
Page 50 |
Page 51 |
Page 52 |
Page 53 |
Page 54 |
Page 55 |
Page 56 |
Page 57 |
Page 58 |
Page 59 |
Page 60 |
Page 61 |
Page 62 |
Page 63 |
Page 64