Page 36: of Maritime Reporter Magazine (April 1994)

Vasa 6R 20 No. 5700 350

O 325 r 300

Piston temperatures

Original shaker

Modified shaker

Fig. 1: More than 500 hours of heavy fuel operation have not affected the liner and no polished surfaces can be seen.

Fig. 2: A modification for the piston cooling gallery shaker effect was introduced to reduce excessive temperature levels. The resulting temperature profile is even and acceptable.

PROPULSION UPDATE

Wartsila Vasa 20:

Test Results Are In

Fig. 3: The condition of the piston after more than 500 running hours on heavy fuel oil. Note the clean ring grooves and piston lands.

Following 18 months of extensive testing and performance mapping, Wartsila Diesel Interna- tional reports that the Vasa 20 engine is showing good results in all major areas.

The tests, which must be performed and ana- lyzed before the engine enters the market, in- clude a wide variety of tests, including: the thermal load on vital engine components (pis- tons, liners, valves, injection nozzles and turbo- chargers); performance data for specific fuel, lube oil and air consumption; wear data and wear patterns of vital engine components; and much more.

CYLINDER PERFORMANCE

Good liner conditions are a prerequisite for correct engine performance, as excessive liner wear may lead to a number of potential prob- lems, including broken piston rings which could let gases enter the crank case and foul the lubricating oil. To ensure proper liner perfor- mance, the Vasa 20 engine is equipped with an anti-polishing device, and based on test results, it works. After 500 hours test on heavy fuel operation, the liners were in excellent condition (see figure 1). Another important indication of excellent liner performance is the lubricating oil consumption, and the Vasa 20 again performed well. Figures show that the lube oil consumption was steady at .53 g/kWh, low compared to state- of-the-art up to now, according to the manufac- turer, but seemingly a stable value for the anti- polishing liners.

PISTON & PISTON RINGS

The very heart of the engine are the piston and combustion space, and if the piston function is not correct, more frequent overhauls are the likely result. It is usually impossible to accu- rately predict all piston temperatures in the design stage because the shaker effect in the piston cooling gallery is complex, reports

Wartsila. High piston cooling gallery tempera- tures were recorded at a relatively early stage of the Vasa 20 testing. The shaker effect was modified to give the correct temperature profile and reduce the top temperatures by about 70° C.

The details are shown in figure 2. The engine manufacturer contends that the forced skirt lubrication provided via the circumferential groove in the piston and the anti-polishing de- vice are a good combination to ensure long over- haul intervals, and points to the condition of the piston after more than 500 hours of operation on heavy fuel oil (see fig. 3).

INJECTION SYSTEM &

ENGINE PERFORMANCE

The injection system must be analyzed in detail, as its function is usually reflected in many engine parameters, such as fuel consumption, heat release behavior, pressure rise in cylinder, smoke emissions and thermal load. If the injec- tion duration is too long, the heat released in combustion of the final portion of the fuel will not be transferred into the desired mechanical en- ergy for shaft rotation. Test results (see figure 4) on the Vasa 20 indicate that the heat release is rather quick and well-defined, which is the rea- son behind the low fuel consumption measured at 191 g/kWh. This value indicates a specific fuel consumption of 187 g/kWh according to ISO 3046/ 1 without engine driven pumps.

Figures which back the effectiveness of the fuel spray configuration include hydrocarbon values running below 50 ppm on heavy fuel and a good carbon monoxide emission below 40 ppm.

NOx EMISSIONS

After it was concluded that all main engine components were functioning well, other optimi- zation procedures started, procedures including

NOx emission measurements. Today there exists no international marine emission legislation. The existing proposals within IMO, however, indi- cate NO emission limits around 11-12 g/kWh for the Vasa 20 engine class. The California Air

Resources Board (CARB) proposal also indicates

NOx limits being of the same order of magnitude, except for new ships. If the CARB proposal will be used, it requires exhaust cleaning systems (SCR) for main engines in new ships. The NOx reduction optimization work of the Vasa 20 has shown that the engine can meet both the CARB and the IMO proposals (see figure 5).

As of December 1993, the six-cylinder proto- type Vasa 20 engine had accumulated more than 2,000 running hours in the diesel laboratory, and the manufacturer reported that no major mal- functions were recorded. Only minor adjust- ments, such as the modification of the piston shaker effect, mentioned earlier, have proved necessary. To speed up the test program, a nine- cylinder Vasa 20 was installed in the diesel labo- ratory in 1993. The engine is equipped with an engine control unit (ECU) and accumulated 500 running hours last fall. For more information on the Wartsila Vasa 20 engine program,

Circle 18 on Reader Service Card

Combustion cycle Vasa 6R20 No 5700

Speed 800 rpm, load 100%

Frinfl pressure - IS.F.C = 191 o/kwh I

U\ . : /I Injection pressure / : I -120 -90 -80 -30 TDC 30 60

Crank angle (CA")

VASA 6R20 LOW NO, OPTIMIZATION

CONSTANT SPEED: 900 rpm

MDO OPERATION 0 12 2 w 11 O - 10 1 • -3 8 § 7< 850 ~ t 750 „

E o 650 1 m 550 o ~ 450 ^ ° o 350 z - _ 20 40 60 80 100

LOAD (%)

Fig. 4: Vasa 20's cylinder pressure, heat release, cylinder pressure rise speed and injection pressure. rig. a: inux emission measuremenrs recoi low NOx optimization of the Vasa 20.

Wartsila Wins Contracts For Engines

On Tankers In S.E. Asia

Wartsila Diesel recently won several contracts for main and auxiliary engines for coastal tankers under construction in the

South East Asia region. They include seven tankers, all of which will be equipped with Wartsila Vasa 32 main engines and

Wartsila SACM Diesel UD25 auxiliary engines. Four of the vessels are 5,000-dwt coastal tankers owned by Malaysia

International Shipping Corp. (MISC), Perbadanan Nasional

Shipping Line Bhd (PNSL), AHS Marine Sdn Bhd and Gaya

Shipping Sdn Bhd. Each vessel will have a six-cylinder Vasa 32 main engine and three six-cylinder Wartsila SACM UD25 auxiliary engines. Two of the vessels are 7,200-dwt tankers owned by Neptank, the coast shipping arm of the National

Shipping Line of Singapore (NOL). These two will each have a six-cylinder Vasa 32 main engine and two six-cylinder Wartsila 'the SACM UD25 auxiliary engines. Also, both of these will feature

Wartsila Propulsion's Wichmann PR 82/4 controllable pitch propeller with shaft alternator. 38 Circle 282 on Reader Service Card Maritime Reporter/Engineering News