Lubrication System

The lubrication oil system has as mission the reduction of the friction between the main engine elements, the elimination of heat produced by friction, and also an anti-rust protection of the uncoated steel elements of the engine. To guarantee these functions, the system is divided into three sub-systems for transfer and storage, treatment and circulating (CIMAC, 2017). In this chapter will be analyzed the major parts of the system, which are the treatment and circulating service system. Figure 13 presents the circulating service loop where its principle will be explained forward.

y = 3E-07x + 0.0518 R² = 0.8999

0.0 0.4 0.8 1.2

0 2,000,000 4,000,000

Pump Power [kW]

Main Engine Hourly Fuel Consumption [g/h]

4-Stroke: Fuel Oil Purifier Feed Pump

Figure 13 - Lubrication system: single diagram (MAN,2020a) The main components of this sub-system are shown in Table 10.

Table 10 - Lubrication system components

nº Designation

1 Lubricating oil pumps 2 Lubricating oil cooler The machinery that will be further analyzed are the lubricating oil pumps.

3.3.2.1 System Lubrication oil pump

The lubrication oil (LO) is collected in a sump tank below the ME. Therefore, its movement mechanically propelled will lubricate the main bearings, crankpin, and crosshead in the case of 2-Stroke engines. After lubricating all components, oil discharge is done by gravity from the crankcase to the tank. The oil passing in all engine major interior components will consequently increase its temperature, as can also bring some impurities. For this reason, it is crucial to a constant circulation of this oil, as its treatment by a purifier.

The circulating system contains two pumps that will conduct the oil from the sump tank, passing through the cooler when its temperature is above the ideal conditions, and also through a fine filter beforel entering in the sump tank. Despite a small consumption of main engine oil and small amounts lost by purifier discharges, this system has a constant flow. Therefore, it is estimated that the LO system is designed according to the ME displacement volume. So, it is estimated that if an engine is larger it will have a higher flow to lubricate all the components. Being the engine displacement volume an easy parameter to estimate, it was placed as input parameters of the model, the cylinder dimensions and the number of engine cylinders. For the power estimation associated with these pumps, it was considered the capacity mentioned in manufacturers' project guide. In addition to the capacity, it was assumed the density. The LO of this system has an SAE viscosity grade of 30, which corresponds to 0.89 kg/m³ at 15ºC.

Implementing the same estimating process that has been developed until now, after pump power samples calculated, it was performed a scatter plot graphic in function of the displacement volume calculated for each engine. In this way, it was obtained for 2-Stroke the graphic of Figure 14.

Figure 14 - Lubrication oil main pump power for 2-Stroke engines

The power consumption for LO system main pumps for 2-Stroke engines is calculated based on (3.15).

9<:05&'./0.= 9.2414 × E(+ 20.656 (3.15)

The same principle was applied for 4-Stroke engines, obtaining the result shown in Figure 15 and Figure 16. After a verification of a big variance in the flow rate parameter in 4-Stroke engines with cylinders number lower than 12 and the remaining, and assuming that engines with more than 12 cylinders have a V-configuration, it was opted to divide into two possible configurations for 4-Stroke engines reducing the error previously found.

Figure 15 - Lubrication oil main pump power for 4-Stroke engines in line configuration

The power consumption equation for 4-Stroke engines lube oil main system pump is present in (3.16).

9<:05&'./0.= 59.318 × E₍+ 45.823 (3.16)

The graphic obtained for 4-Stroke engines in V configuration is shown in Figure 16.

Figure 16 - Lubrication oil main pump power for 4-Stroke engines in V configuration Where the corresponding equation of the regression achieved is following shown.

9<:05&'./0.= 98.718 × E(− 16.537 (3.17)

3.3.2.2 Cylinder Lubrication Oil Pump

For a 2-Stroke crosshead ME, normally, in addition to the general lubrication of the engine movements, there is an independent one for the cylinders. The cylinder LO will lubricate liners, pistons, and piston rings. This system is one of the most important systems since it should be prepared to deal with conditions of higher temperatures and combining with the acidity of the fuel. Normally this system can be pumped by a mechanical system that is actuated by the camshaft or can be introduced as an automatic system to dose the cylinder oil for each one. In this thesis it is considered as a mechanical system.

3.3.2.3 Lubrication Oil Purifier

The ME oil in its passage can be contaminated by small particles, combustion products, or water, for this reason, it is essential a purifier. The purifier capacity is recommended by the ME manufacturers. For the purifier power estimation, it was used the equation (3.10) and performed the analysis with the same variable E₍. The result of the analysis for 2-Stroke engines is shown in Figure 17.

Figure 17 - Lube oil purifier for 2-Stroke engines

The power consumption of the LO purifier for 2-Stroke engines can be estimated with the equation (3.18).

9<:+/*&G&)*= 0.4315 × E(+ 3.4796 (3.18)

After the same principle applied for 4-Stroke engines, it is obtained the result shown in Figure 18.

Figure 18 - Lube oil purifier for 4-Stroke engines

The corresponding equation obtained from the graphic regression curve is shown in (3.19).

9<:+/*&G&)*= 2.2101 × E₍+ 3.4383 (3.19)

3.3.2.4 Lubrication Oil Purifier Feed Pump

The LO purifier feed pump is part of the treatment sub-system. It has the same function as the FO purifier feed pump, to feed the purifier with a constant flow. The suction of this pump can be from the sump tank, occurring an oil recirculation to ensure the oil purity, or from the engine oil filling tank to guarantee the good quality of oil when it is supplied the small quantities necessary to the closed system. For the power consumption of these pumps, it was used the recommended values for purifier flow rate described on ME project guides. The independent basic design variable considered for the LO feed pump power estimation is the displacement volume. Figure 19 presents the scatter graphic then obtained for 2-Stroke engines.

Figure 19 - Lubrication oil purifier feed pump for 2-Stroke engines

The power consumption equation implemented in the model for 2-Stroke engines, is the equation (3.20).

9<:+/*&G&)*G))(./0.= 0.1265 × E₍+ 0.1868 (3.20) For 4-Stroke engines the resulting graphic is present in Figure 20.

Figure 20 - Lube oil purifier feed pump for 4-Stroke engines The resulting equation of the regression line performed is presented in (3.21).

9<:+/*&G&)*G))(./0.= 0.6843 × E₍+ 0.1458 (3.21)