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 ; the value of12/13.vrVV==0032/1.8prTT== ; and the cut-off ratio ; the temperature of the air entering the cylinder ; and the pressure43/1.4crTT==01300TK=()211.0 bar 100 /pkN m=. Determine: a. the temperatures , , and in K 2T3T4T5T b. the mass of the gas, m, in the cylinder in kg c. the heat transfers, 1HQ, at constant volume; 2HQ at constant pressure, and at constant volume, in kJ LQd. 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 efficiency0.83PCη=. The effectiveness of the charge cooler ()()11/0COMP COMP WTTTTε=− −=.8K where the cooling water temperature, the air temperature leaving the compressor and entering the charge cooler is and the temperature of the air leaving the charge cooler and entering the engine cylinder is T. 300oWT=COMPT Determine: e. the temperature of the air leaving the charge cooler and entering the engine cylinder 11Tf. Repeat the tasks a through d for the new situation. Assume that the properties of air are 1.00 /pCkJkgK=, ck1/1.40 /vJkgK= and.286 /RkJ 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. 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) b. the thermal efficiency and sfc of the cycle (section 7.4.3 in text) c. the mass of air in each cylinder d. the power output per cylinder e. the mean effective pressure f. compare your predicted values with the data in the article g. provide a justification for any differences Assume that air has cp = 1.00 kJ/kg K, γ = 1.4, and the heating value of the fuel (LHV) is 43,000 kJ/kg.~ee-form additions to - gin*, - have retarded sales of in-line nou,complcred some i5 OOOh of operation eijgiiiesrc:en;:y i?drheFiiisrickdesignen with no funher problems. have therefore brought our two new Vee- Heavy fueiofatleast i8OcSt vircoriryis type engines, lo be known as the PC4~2B uiedonRewHomo~iuandher5iiteiships. and PC2-6B. and this has brought no problems. avoiding long engine idiing periods. The PC4-2B engine is based on the long However. the bumt air inlet vdves re Funhemore.somecrackr were foundin established PC4-2 design but incorpamrer femd toeariieiaose from the ship spend- three cylinder heads and a number of fuel componentsofthe youngeePC40Lengine. inglongperiods with the engines idling on pump delivery valves but these were inili- However, the Pielstick engineen have in noioad. Duringtheseidlingpe~odsdepo~ ated from manufacmring faults. creased the piston snoke from 62hm in irs built up in the inlet ports, due to rlighr rhe~~4-2r0660mmand thefiringpressure bac~owofexhauitgas, and iheieeven,u- Wear rates from 145 bar to i50 bar. aily fell into the air inier valves and were Of two more recenrly built PC40L~ Thesechanges,combinedwdththesame hammered - ultimateiy causing burning powered ro-ro ships operating in a tramp power output per cylinder (1650bhp) and of the valve seats. type sewice wd the Japanese coast,one therefore a decrease in bmep, have im- The problem hasbeen solved by simply has hadonestapat seaofah inaroraloftwo proved the specific fuel oil consumption r. fiom 183gikW h 10 175gikW hfoithe new cross section ofthe~~13-ZE veetormmd;um-~peedd~erel engine. Further improvemenain reliability i are also expected. U'hen some ferry operators in Japan iwked at newbuilding instaiiations, they decided torerum to Vee-type engines- as aresultanumberofferries presently build- ing in Japanese yards are being installed with Vee-form PC24 engines. 70 funher improvethaiengine,thePieistickderigner, have mken proven components fmm the PC20L design and incorporated these into the new PC2-6B. Other minor modifica- tionr have beenaddedandthepweroutput per cylinder has been lifted to the 825bhp level of the PCZOL machines. The piston stroke has been slightly increased to 500mm but the engine speed is held at 520revlmin. PC40L service results At the beginning of 1990 a total of 34 PC40Lengines had been ordered and 17 of these were in service. The first engines (21 9PC40L) in three ferries have been in sewice for rome two ! andahalftothreeyeanandhvvereponedly givenercellenrrerults.lndeed,~efintpair .> ofenginer,inrtalledin the 1987-built ferry I NewHomn~srr,haveneveicauredtheship to be delayed or stopped ar sea and a sister- ship has achieved the same ncord even Pielstick family Ewlns. PC42 PC428 FWO ! Cyl bre (mm) 570 570 570 sMe (mm) 6M 560