(tec2010_005) improvement of fuel injection valve-h2533

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TECHNICAL CIRCULAR

TYPE: H25/33

SUBJECT: IMPROVEMENT OF FUEL INJECTION VALVE

Ref. No.: TEC2010/005

Date: 6th July 2010

ENGINE & MACHINERY DIVISION Tel: +82-52-202-7274, Fax: +82-52-202-7696, E-mail: [email protected]

TECHNICAL CIRCULAR Ref. No.: TEC2010/005

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[GENERAL] The fuel injection valve has continuously been improved over the years, with all modification

being extensively tested in service to verify the improved performance. The test results and the general service results gained in recent years have led us to introduce a new design improvement of fuel injection valve on HiMSEN H25/33 four-stroke engine. [PHENOMENON]

The unexpected heavy smoke or high exhaust gas temperature was intermittently detected during engine operation in certain conditions. The reason for the above phenomenon is not only improper operation but also insufficient life time in the fuel injection valve; for example, broken spring, poor atomization and carbon deposit on the nozzle tip.

[IMPROVEMENT]

We have pursued the objective to develop fuel injection valve design that is extremely durable with respect to abrasion of fuel injection nozzle and poor atomization. As a result, we have succeeded in finding suitable solutions as follows.



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1. Improvement for nozzle durability

The major improvement to reduce wear rate has been verified with a variety of tests.

1) Material combination of nozzle body and needle It was found that the material combination of the nozzle body and the needle had

made a big effect on their wear rate. The wear rate leads to a different life time of the nozzle. <Improvement>

Four material combinations were tested. The results are listed below. The wear depth of current model that the material of body and spindle is NT 200 and SKH 51, is 7~11 ㎛. On the other hand, wear depth of SKD61 body and SKD61 needle is 1~2 ㎛ under the same conditions. The SKD61-SKD61 combination has shown the best wear resistance, which helped the nozzle achieve better reliability.

Nozzle body Needle Wear rate Remark

SKD 61 SKD 61 1~2 μm Best

SKD 61 SKH 51 3~4 μm

NT 200 SKD 61 5 μm

NT 200 SKH 51 7~11μm Current

Table 1. The test result of H21/32 nozzle body wear rate



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2) Minimized moving mass

The heavy weight of moving parts, such as needle, spindle, spring, is also another cause of high wear rate. It gives body a big shock and makes body wear easily. It is the reason of short life time of nozzle. The heavier the moving parts are, the higher the impact force generated. <Improvement>

Impact between needle and body can be reduced by means of decreasing moving part weight. In order to decrease the mass, size of needle and spindle becomes smaller. For example, needle diameter has been decreased from Ø9 to Ø8 and length of needle has been also modified from 77 mm to 67 mm. The size of the spindle has been also reduced. Finally, total moving mass have been reduced from 57.1g to 30.6g, a 46% reduction. Longer life time of minimized moving mass has been proved in field tests.

Item Present Improvement

Needle Dia. (D1) Ø9.0mm Ø8.0mm

Seat Dia. (D2) Ø6.3mm Ø5.4mm

Length of Spindle (S) 59.0mm 23.0mm

Length of Needle (N) 77.0mm 67.0mm

Table 2. The dimension data of moving parts (needle, spindle)



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3) Opening pressure of fuel injection valve

It has been found that the opening pressure is also a cause of high seat wear. The higher the opening pressure, the higher the initial spring force. If the initial spring force is reduced by 10%, the impulse can be reduced by about 20%.

<Improvement>

In order to reduce impulse power on nozzle by spring force, opening pressure of fuel injection valve has been decreased from 450 bar to 400 bar. Longer nozzle life time by optimizing opening pressure has been proved in field tests.

With these design improvements, a significantly longer life time of fuel oil injection nozzle can be achieved thanks to the new material combination, minimized moving part mass and the optimized opening pressure.

2. Improvement of spring durability

Cavitation can occur in areas where the flow of liquid suddenly increases due to narrow path (if the speed of liquid increases, the pressure becomes low by the principle of the conservation of energy). In case of fuel injection valve, spindle with spring reciprocates and

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3. Improvement of atomization at low load

Intermittent heavy smoke during low load operation on HFO has been found. The cause of smoke is carbon deposit on the nozzle tip which interrupts atomization. Carbon deposits have been generated due to low injection pressure at low load operation and thermal transformation of hot condition nozzle tip. When the surface temperature of the nozzle tip is high, atomized fuel particles are burnt on the surface. It causes carbon deposit stack near nozzle tip.

<Improvement> In order to eliminate thermal transformation, the cooling system has been adopted on the

nozzle. With this system, the temperature of nozzle tip can be kept in setting temperature range. Heavy smoke on low load has been reduced by this nozzle cooling system.

Note: Same nozzle hole configuration (Same IMO ID, No change NOx Tech. file)

4. Additional improvement (Fuel injection valve tester) We have found that even normal operating fuel injection valve has been proved as

defective product with poor injection due to malfunction of fuel injection valve tester. The cause of fuel injection valve tester malfunction is capacity shortage. Therefore, the capacity of tester has been increased by modifying the diameter of pump from Ø8 to Ø10 and increasing the volume accumulation by three times

.



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[SUMMARY] Design improvement;

- New material combination of atomizer - Mini-mass design of moving parts - Opening pressure 400 bar instead of 450 bar - Triangular shape spring guide of spindle - Nozzle cooling system

The above mentioned improvements result in better atomizer reliability and invisible smoke on low load operation.

[The end]

(tec2010_005) improvement of fuel injection valve-h2533

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