Mircea cel Batran Naval Academy Scientific Bulletin, Volume XIV 2011 Issue 2 Published by Mircea cel Batran Naval Academy Press, Constanta, Romania

Transcription

1 THE ENGINE THERMAL BALANCE DETERMINATION OF ENERGY UANTITY NECESSARY FOR LUBRICATION OF A NAVAL ENGINE Florian VASILE Dmitr CATANĂ Ion ŞERBĂNESCU 3 Cătălin Petrişor MIREA 4 Dorel Dmitr VELCEA 5 Drding, Military Technical Academy, Bcharest Drding, Military Technical Academy, Bcharest 3 Drding, Military Technical Academy, Bcharest 4 Drding, Military Technical Academy, Bcharest 5 Drding, Military Technical Academy, Bcharest Abstract To keep the engine parts temperatre between some limits, a waste of energy is needed This paper presents aspects link to the importance of lbrication of engine mechanism and afferent installation and the elements of lbrication installation which inflence the thermal balance of the engine For example were determined the antity of energy necessary of lbrication of a naval engine, sing the technical docmentation Keywords: thermal balance, energy antity, lbrication THERMAL BALANCE LUBRICATING OIL SYSTEM Energy flow prodced by combstion becomes partially effective power and the rest is discharged throgh varios ways ot as loss of heat flows The distribtion of these losses depends on engine type, motor cycle, operating conditions and power otpt Thermal balance expresses the eality between the energy flow introdced into the engine by brning fel in the cylinders and the varios energy flows that occr between engine, consmer and environment The energy balance represents the distribtion of available energy flow,, between effective power and different loss Heat balance eation is : = + e ge rac rez If lbrication oil cooling is achieved with seawater, in open circit cooling, in the energy balance eations appear an additional term, rac lei, corresponding to the seawater energy flow taken from lbe oil On the other side, when are sed several closed cooling circits, the term rac will be divided in corresponding components of each circit In sch cases the energy balance eations becomes: + + where: = + e ge + rac cil + rac pist + rac inj + rac lei rez = available energy flow introdced into the engine by combstion; e = effective power; ge = energy flow exhast with combstion gases; rac = energy flow evacated by cooling; rez = residal energy flow (evacated by radiation); 34

2 fr racev rac rac cil rac pist rac inj rac lei gev ai rad conv rez e In percent the energy balance eation becomes: Figre Heat balance diagram where : e [ ] + ge + rac + rac lei + rez =00 % e e = 00[%] e = ; ge ge = 00[%] ar = 3 7 ; ge = 5 35 ; rac = 00[%] ar = 0 5 ; rac lei = 00[%] rez = 00[%] rez = 5 ; rez = Ch i [kw] Pe ce i = [kw] In the engine mechanism, the oil meets the following fnction: - ensres redction of friction forces by moving srfaces lbrication; - maintain the temperatre of the moving parts; - provides sealing between cylinder and piston-segment assembly; - evacates the imprities prodced or accidentally falling inside the moving parts; - transport and store inside the filter or in carter this imprities; - provides the engine components protection against the corrosive action of environment The lbrication intensity of the different engine parts depend on their operating conditions: charge, friction srface and relative lacement speed All forms of sliding friction exist in the internal combstion engine: dry friction, semi-dry friction, semi-liid friction and liid friction In the second figre is indicated the oil film formation for translation motion parts (cylinder and piston ) a) The maximm oil pressre is indicated in diagram b; the smallest thickness of oil layer is between 0,00 0,007 mm (diagram 35

3 4 3 - b a Oil pressre Oil layer P, kgf/cm thickness μm + Figre Oil film formation between piston and cylinder In the bearing-spindle assembly (figre 3) the spindle rotates with speed n, being placed eccentric to the bearing ; the AB gap, filled with oil, will have variable height, which makes the flid to exert a lifting action F Maximm clearance Oil otlet n Oil inlet B Minimm clearance A Oil film pressre Figre3 Oil film formation between bearing and spindle In figre 4 is illstrated the lbricating oil system for a six cylinders Diesel engine, wet crankcase, characterized in that the engine oil is stored in the crankcase From crankcase, the oil is scked throgh a raw filter and is laced by lbrication pmp to the oil strainer From this strainer, the oil passes throgh the oil cooler and reaches the lbrication ramp, from where it is distribted to main bearings From main bearings throgh crankshaft, the oil reaches the connecting rod bearings and, from here, to the gdgeon pin From the same location -lbrication ramp- the lbricating oil is sent to the other mechanical joints of the engine, like camshaft bearings, rockers, etc In the forth figre is indicated, before the oil strainer, a bypass strainer and a manometer; a second manometer is placed in the farthest location from the pmp The dry smp lbrication system has the advantage of redcing the height of the engine; the lbricating oil has a limited contact area with hot gasses, dropped in the crankcase, therefore follows that the oxidation is redced and allows an efficient cooling of lbricating oil Disadvantages of the system: - large nmber of oil pmps; - system complexity; - large amont of oil needed; All this leads to higher constrction, operation and maintenance costs This system applies in particlar to large engines, becase it allows redction of engine height and an efficient cooling oil 36

4 Piston Piston pin Connecting rod bearings Base bearings cylinders pmp Pmp strainer Lbrication ramp Relief valves cooler manometer Coarse strainer Bypass filter manometer Figre4 Wet smp lbricating oil system In figre 5 are presented the components for MAN B&W 5S 50MC main engine lbricating oil system: crankshaft lbricating oil cooler; main engine lbricating oil cooler; 3 bypass strainer; 4 self-cleaning filter; 5 cylinder lbricating oil service tank; 6 cylinder lbricating oil storage tank; 7 main engine; 8 filter nit; 9 drain and circlating tank; 0 smp tank; main lbricating oil pmps; camshaft lbricating oil smp tank; 3 camshaft lbricating oil pmps Figre5 MAN B&W 5S 50 MC lbricating oil system 37

5 DETERMINATION OF ENERGY UANTITY NECESSARY FOR LUBRICATION OF A NAVAL ENGINE We chose for exemplification the following engines: SULZER 5RT-flex 58T-B, 8550 MCE and RTA 84(4) Starting from the following SULZER 5RT-flex 58T-B characteristics and measred vales: Pe = 0900 kw - effective power engine; n = 00 rot/min - engine speed; c e = 0,70 kg/kwh - specific fel consmption; ṁ am = 74 m 3 /h - seawater pmp flow; ṁ c = 8 m 3 /h - reired lbricating oil cooling water flow; m rac ge = 5 m 3 /h - pmp water flow rate of recovery boilers; m p a d = 97 m 3 /h - freshwater flow pmp(closed circit); ṁ = 55 m 3 /h - circlation pmp lbricating oil flow; we can determine the amont of energy introdced into the engine throgh combstion, Pe ce i = [KW] where the fel low calorific power is: Performing calclation reslt: i = 4700 [kj/kg] = 978 [KW] Knowing the reired lbricating oil cooling water flow, ṁ c = 8 m 3 /h and the inpt and otpt temperatres at the oil cooler, illstrated in figre 6, is calclated the energy flow evacated by lbricating oil cooling: r = m c ca Ta r = 955 [KW] In figre 6 is shown schematically the lbricating oil system with the elements that affect the engine energy balance 955 kw 57,4 0 C 48 0 C Oil cooler 55 m 3 /h 0 m 3 /h trbocharger 5 m 3 /h Cross head 5 m 3 /h bearings 5 m 3 /h engine Oil discharged by brning Oil separator 90 0 C 57,4 0 C Oil preheater 55 m 3 /h Oil tank,5 m 3 /h Figre6 Scheme and fnctional parameters for lbricating oil system From technical data of installation, the circlation pmp lbricating oil flow is: m = 55 m 3 /h; 38

6 and the temperatre difference between the engine otpt oil temperatre and the engine inpt oil temperatre is T = 0,6 0 C Therefore follows the energy flow evacated with lbricating oil = m c T where c is the oil specific heat and has the following vale: c =,093 [kj/kg grd] = 955 [KW] Depending on engine power, calclated at certain speeds, exchange of energy between energy consmer and environment can be calclated For exemplification, the antities of energy released by engine cooling, lbrication and recovery boiler were calclated; reslt are presented graphically in the following figre Figre7 The energy loss by engine cooling, lbrication and recovery boiler for the SULZER 5RT-flex 58T-B engine The energy flow vales evacated with lbricating oil are presented frther: Heat flow introdced into the engine: = Ch i [KJ/h] Ch i = [KW] SULZER 5RT-flex 58T-B 8550 MCE RTA 84(4) [kw] , Energy flow evacated with engine mechanism lbricating oil: = m c T [KW] ρ = 900 [kg/m 3 ] m = ρ V [Kg/s] V [m 3 /h] SULZER 5RT-flex 58T-B 8550 MCE RTA 84(4) ,5 60,5 ṁ [kg/s] c =,093 [kj/kg grd] T [ 0 C] 9,4 5,5 4,6 [kw]

7 Energy flow evacated with camshaft lbricating oil: ax = m ax c V ax T [KW] m ax = ρ V ax [Kg/s] - volme flow of camshaft lbricating oil circlation pmp ρ = 900 [kg/m 3 ] c =,093 [kj/kg degree] T = [degree] SULZER 5RT-flex 58T-B V ax - 6,4 - [m 3 /h] m ax -,6 - [kg/s] ax - 6,7 - [kw] 3 CONCLUSIONS To maintain the engine parts temperatre within certain limits is necessary to evacate some energy flows that depend on engine load Operating characteristics of lbricating oil are inflenced by large temperatre variations, which reire oil cooling and maintaining its low temperatre limits 8550 MCE RTA 84(4) REFERENCES [] A Pri, Instalaţii energetice navale Editra Mntenia & Editra Leda, Constanţa (000) [] A Dragalina, Motoare c ardere internă Vol,,3, Editra Academiei Navale Mircea cel Bătrân, Constanţa (003) [3] DWoodyard, Elsevier-Btterworth Heinemann, Ponder s Marine Diesel Engines and Gas Trbines, Wobrn (004) [4] wwwdieselengine motorcom Slzer Diesel Engines 40