Massachusetts Institute of Technology DEPARTMENT OF OCEAN ENGINEERING 2 611 SHIP POWER and PROPULSION Problem Set 5 Diesel Engine Problems Due November 14 2006 1 A diesel engine designer is interested to know the effect of turbo charging on mean effective pressure and power The engine he is considering is a 14 cylinder 4 stroke diesel engine The rotational speed is 1200 rpm mean piston speed of 12 m s and stroke to bore ratio of 1 25 The following data is estimated Note Review chapter 7 in the text before attempting this problem Thermodynamic efficiency 58 5 Mechanical losses 8 Heat losses 9 Charge pressure 3 5 bar overpressure in inlet receiver Charging is reasonably effective 93 Inlet receiver temp 60 Celsius Air excess ratio 1 8 Lower heating value of fuel 42 000 kJ kg Stoichiometric fuel air ratio 13 1 Gas constant air exhaust gas R 287 kJ kg a Calculate engine efficiency mean effective pressure and power output Note you can assume that the combustion efficiency is 100 b If an engine of the same size was not turbocharged what would be the efficiency mean effective pressure and power keep assumptions unchanged 2 The air standard dual cycle is used to represent the thermodynamic characteristics of a large two stroke diesel engine The cylinder volume V1 1 0 m3 the compression ratio rv V1 V2 13 0 the value of rp T3 T2 1 80 and the cut off ratio rc T4 T3 1 40 the temperature of the air entering the cylinder T1 300 K and the pressure p1 1 0 bar 100kN m 2 Determine a b c d the temperatures T2 T3 T4 and T5 in K the mass of the gas m in the cylinder in kg the heat transfers QH 1 at constant volume QH 2 at constant pressure and QL at constant volume in kJ the work of the engine per cycle in kJ and the power per cylinder in kW when the two stroke engine operates at 79 rpm The engine is now fitted with a turbocharger and charge cooler The compressor pressure ratio of the turbocharger is 3 9 and the polytropic efficiency PC 0 83 The effectiveness of the charge cooler TCOMP T11 TCOMP TW 0 8 where the cooling water temperature TW 300 K the air temperature leaving the o compressor and entering the charge cooler is TCOMP and the temperature of the air leaving the charge cooler and entering the engine cylinder is T Determine e f the temperature of the air leaving the charge cooler and entering the engine cylinder T11 Repeat the tasks a through d for the new situation Assume that the properties of air are C p 1 00kJ kgK cv 1 1 40kJ kgK and R 286kJ kgK 3 Using the data presented in the Vee form additions to Pielstick family article calculate the engine performance assuming that it can be modeled as an Air Standard Dual Cycle Use the PC40 engine Assume that the constant volume temperature rise is T3 T2 300 K the constant pressure temperature rise is T4 T3 800 K and the air from a charge cooled turbocharger enters the cylinders at 300 K and 3 bar Determine a b c d e f g the temperatures and pressures at conditions 1 through 5 the text can be used to help you understand terms you are not familiar with like combustion ratio the thermal efficiency and sfc of the cycle section 7 4 3 in text the mass of air in each cylinder the power output per cylinder the mean effective pressure compare your predicted values with the data in the article provide a justification for any differences Assume that air has cp 1 00 kJ kg K 1 4 and the heating value of the fuel LHV is 43 000 kJ kg e e f o r madditions to Pielstick family lthough the SEMT Pielrrick PC40 engine has been wcli accepted and rervtce resuirs have shown high reiisbiiiry the use of iarge bore in line medium speed engines in ferries ln Japan has not been entirely iucccssful Engine indurdribraiionson sai e sfinpan snew ferries none of them u itll Pklsrick engin have retarded sales of in line eijgiiiesrc en y i drheFiiisrickdesignen have therefore brought our two new Veetype engines lo be known as the P C 4 2 B and PC2 6B The PC4 2B engine is based on the long established PC4 2 design but incorpamrer componentsofthe youngeePC40Lengine However the Pielstick engineen have i n creased the piston snoke from 6 2 h m in r h e 4 2 r 0 6 6 0 m m a nthefiringpressure d from 145 bar to i 5 0 bar Thesechanges combinedwdththesame power output per cylinder 1650bhp and therefore a decrease in bmep have improved the specific fuel oil consumption fiom 183gikW h 10 175gikW hfoithe new engine Further improvemenain reliability are also expected U hen some ferry operators in Japan i w k e d at newbuilding instaiiations they decided torerum to Vee type engines as aresultanumberofferries presently building in Japanese yards are being installed with Vee form P C 2 4 engines 70 funher improvethaiengine thePieistickderigner have mken proven components fmm the PC20L design and incorporated these into the new PC2 6B Other minor modificationr have beenaddedandthepweroutput per cylinder has been lifted to the 825bhp level of the PCZOL machines The piston stroke has been slightly increased t o 500mm but the engine speed is held at 520revlmin A r i though i r i engines suffered fiom some burnt air inlei valves The valves were changed during a pon turnround Both there ships have now accumulated more rhan 16 MOh of aperaiion The third ship in the senes suffered rome problems with air inier cams and missed one voyage of 2Oh d m i i o o but has nou complcred some i 5 OOOh of operation with no funher problems Heavy fueiofatleast i8OcSt vircoriryis I uStmw m mi p cylovipufbw I mepjw M u pess bar Sfoc at mn PC428 F W O 570 570 560 750 4m 8 8 375 9 4 94 11 8 13 3 140 1215 1300 12151325 27 5 21 6 20 2 22 1 145 150 155 uiedonRewHomo iuandher5iiteiships avoiding long engine idiing periods and this has brought no problems Funhemore somecrackr were foundin However the bumt air inlet vdves r e f e m d toeariieiaose from the ship spend three cylinder heads and a number of fuel inglongperiods with the engines idling on pump delivery valves but these were inilinoioad Duringtheseidlingpe odsdepo ated from manufacmring faults irs built up in the inlet ports due to rlighr b a c o w o f e x h a u i t g a s and iheieeven u Wear rates Of two more recenrly built P C 4 0 L aily fell into the air inier valves and were hammered ultimateiy causing burning powered ro ro ships operating in a tramp type sewice w d the Japanese coast one of the valve seats The problem hasbeen solved by simply has hadonestapat seaofah inaroraloftwo cross section …