Exam2_ME444_Fall07_A

Exam2_ME444_Fall07_A - ME 444 Exam 2 Form A October 11,...

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ME 444 Exam 2 Form A October 11, 2007 Open Notes Place answers in spaces provided. Name:________________________ PID:__________________________
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____ 1) What is the difference between Net Thermal Efficiency and Brake Thermal Efficiency? a) Mechanical Losses b) Flow Losses c) Pumping Losses d) Incomplete Combustion ____ 2) Pumping losses are caused by: a) Mechanical fuel pumps b) Flow losses across intake and exhaust systems c) Unequal fuel distribution between cylinders d) Friction between piston rings and the cylinder liners ____ 3) How does volumetric efficiency change if T i (intake temperature) increases by 4%, assuming all other parameters remain constant? a) Increases by 4% b) Increases by 2% c) Increases by 16% d) Decreases by 4% e) Decreases by 2% ____ 4) A 15L diesel truck engine has a brake mean effective pressure of 190 psi and an absolute friction mean effective pressure of 10 psi. What is the net mean effective pressure? a) 200 psi b) 180 psi c) 100 psi d) 195 psi ____ 5) The same 15L diesel truck engine at a different operating state has a net mean effective pressure of 310 psi, friction mean effective pressure of 20 psi and an indicated mean effective pressure of 335 psi. What is the pumping mean effective pressure? a) 25 psi b) -25 psi c) 645 psi d) -45 psi ____ 6) For a typical engine operating at WOT, order the MEPs from highest to lowest. (Note: not all MEPs are positive values) a) MEP 1 , MEP 2 , MMEP, FMEP, XMEP, NMEP b) BMEP, NMEP, FMEP, IMEP, PMEP c) IMEP, NMEP, BMEP, FMEP, PMEP d) FMEP, PMEP, BMEP, NMEP, IMEP
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____ 7) A 4 cylinder engine with displacement of 2.4L (144 in 3 ) at 3000 RPM outputs 100 ft-lbs of torque. What is the BMEP of this engine? (Approximate π = 3) a) 25 psi b) 100 psi c) 200 psi d) 85 psi e) 150 psi f) 125 psi ____ 8) An engine has an IMEP of 300 psi. Its NMEP equals 3 times the absolute value of PMEP. What are the NMEP and PMEP respectively? a)
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Exam2_ME444_Fall07_A - ME 444 Exam 2 Form A October 11,...

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