Marine Diesel Engines - Decreasing Fuel Consumption and Exhaust Gas Emissions in Transportation - page 164

fuel 100 %

engine radiation
1 %

exhaust gas
18 %

cooling
8 %

steam for
turbo generator
11 %

heating
9 %

steam for
other users
1 %

shaft output
52 %

Fig. 11.5 Dissipation of energy in a slow speed marine diesel enginediesel engine

pre-mixing fuel

mixing fuel and air intensively pre-evaporating fuel

improving the uniformity of
fuel injection

avoiding incomplete
(not stoichiometric) burning

future combustion technology

changing the time that gases
stay in the combustion chamber
by variable spin formation and
recirculation

adapting after-reaction zones in
the combustion chamber

Fig. 11.6 Improvements of future injection technology

11.5.3 Improving Operation

On average, a slow speed two-stroke marine diesel engine converts more than 50%
of the chemical and thermal energy to mechanical work. With the slow speed of
the piston, the combustion process is more complete than in fast speed four-stroke
engines. Theoretically more than 60% thermal efficiency would be possible, but a
higher heat recuperation rate is not yet possible. The efficiency depends on friction
losses and recuperation of exhaust gases (see Fig. 11.5 )[ 39 ].
Further improving common rail injection efficiency for large two-stroke engines
is one of the most important technological tasks. In common rail systems, the
pressure in the fuel rail is up to 1,000 9 10 5 Pa (20.89 9 10 5 lbf ft -2 or 14,504 psi)

and the valve pressure is up to 200 9 10 5 Pa (4.18 9 10 5 lbf ft -2 or 2,901 psi) [ 40 ].