University of Babylon College of Engineering\Al-Musayab Automobile Engineering Department Final Examination/1st Attempt جامعة بابل Subject: I. C. Engines I Maximum Time: 3 Hours Class: 3rd Date: / / 2023 Answer 07 of the following questions (First Semester) 2022/2023 (1) Choose the correct answer for eight only from below 1- Indicator diagram shows for one complete revolution of crank Maximum mark: 50 Deg. a) variation of kinetic heat in the cylinder. b) variation of pressure head in the cylinder c) variation of kinetic and pressure heat in the cylinder. d) none of the above. 2- A carburetor is used to supply (a) petrol, air and lubricating oil (b) air and diesel (e) petrol and lubricating oil (d) petrol and air. 3- In a four stroke cycle petrol engine, the charge is compressed when a) inlet valve is closed. b) exit valve is closed. c) both inlet and exit valves are closed. d) both inlet and exit valves are open. (8 deg.) 4- For an engine operating on air standard Otto cycle, the clearance volume is 10% of the swept volume. The air standard cycle efficiency is. a) 38.3% b) 39.8% c) 60.2% d) 61.7% CV = 10% 5- In carburetors, the top of the fuel jet with reference to the level in the float chamber is kept at a) Same level b) Slightly higher level c) Slightly lower level d) May be anywhere. 6- If the compression ratio of an engine working on Otto cycle is increased from 5 to 7 the percentage increase in efficiency will be (a) 2% (b) 4% (c) 8% (d) 14% 7- in diesel engine, the compression ratio as compared with the expansion ratio is (a) same (b) less (c) more (d) variable 8- Most high speed compression engines operate on a) Dual combustion cycle b) Diesel cycle e) Otto cycle d) Special type of air cycle 9- In a 75 cc engine the parameter cc indicates (a) fuel tank capacity (b) lubricating oil capacity (c) swept volume (d) cylinder volume 10- For the same maximum pressure and temperature, what is the relation among the efficiencies of the Otto cycle, the Diesel cycle and the Dual cycle? (a) n dual > n diesel > n otto (c) n diesel > n otto > n dual η (b) n diesel > η dual > n otto (d) n otto > n diesel > n dual η (2) A petrol engine has the following parameters at sea level: AF-14, T-27 'C, P=1.03 bar. Calculate the AF ratio at the altitude of 5000 (m). Where 1.03 Taltiyude =Ts -0.0065h and h = 19200 x log10 Paltitude (7 deg.) (3) A 4 cylinder has a following data Bore-15 cm; Piston speed 510 m/min: B.P= 60 kW; mech. eff. -0.80, Pm-5 bar; C.V-40000kJ/kg. Calculate i) whether this is 2 Stroke or 4 Stroke engine and why? (7 deg.) (4) Write a notes on heat balance sheet, draw that on the energy flow and state any relations you need. (7 deg.) (5) Derive an expression for the air standard efficiency of diesel combustion cycle in terms of compression ratio, cut-off ratio and pressure ratio. Show the cycle on PV and T-S diagrams. (7 deg.) 1-2