TypicalexamquestionsforMAR2019-11May2022[1]
.docx
School
Newcastle**We aren't endorsed by this school
Course
ENG 4568
Subject
Mechanical Engineering
Date
Jan 12, 2025
Pages
2
Uploaded by JusticeRock16141
Typical exam question styles for MAR2019Note: 1.The answer keys to the questions below are NOT accurate. In the exam, the answer keys are required to have at least 6 significant digits. 2.These questions are only style example. Questions in the exam will not limited only to the contents covered by the following sample questions. A.Consider the propeller and ship described below:density of sea water 1026 kg/m3skinematic viscosity of sea water 1.13910-6 m/s2fkinematic viscosity of fresh water1.18810-6 m/s2Wwake fraction 0.135 Dpropeller diameter 4.5 mJadvance number (open-water) 0.833 npropeller rpm 3 1/sKTthrust coefficient0.1594Vship speed 13 m/sRrelative rotative efficiency 0.95 0open-water efficiency 0.684 a)The ship resistance at design speed is 580 kN. The ship is at constant speed. What is the thrust deduction fraction t?b)Give an estimate for the propulsive efficiency D.c)For a 1:16 model of the ship a wake fraction w= 0.19 is measured in towing tank tests. What should be the propeller rpm at the model speed corresponding to full-scale design speed?d)Compare Reynolds numbers at 0.7Rfor the model and at full scale. The full-scale propeller chord cat r/R = 0.7 is 2 m.B.Consider a ship with speed Vs= 15 kn, thrust deduction fraction t= 0.2, wake fraction w= 0.15. The ship is equipped with a Wageningen B4-40 propeller with diameter D= 6 m. The water density is = 1025 kg/m3. The resistance curve between 10 and 16 kn is given in good approximation by (Rin kN, Vin kn):R=10⋅V2−185⋅V+1100a)What is the required thrust?b)At what points (J, KT,KQ, 0) does the propeller operate assuming P/D= 0.8, 0.9, 1.0, 1.1, and 1.2, respectively?c)What propeller P/Dwould you chose? What are the corresponding open-water efficiency, torque and delivered power of the engine?d)What are then delivered power and open-water efficiency at Vs= 12 kn?Use the file Wageningen_B4-40.pdfto find the solution. C.Given the formula in the lecture slides for the pitch angle as a function of pitch ratio, pD, and the following table, find the pitch angle and its distribution along the radial direction (i.e., blade spanwise direction)Geometry angle as function of radius for a constant pitch ratioPD=0.601.001.60r/Rαp αp αp αp αp αp
(rad)(deg)(rad)(deg)(rad)(deg)0.200.300.400.500.600.700.800.901.00D.Given the following self-propulsion test results (page B9 on the DTMB report) FnVm (m/s)RATmQmnmRc0.12621.10659.69515.97400.81403.981022.910000.15711.377514.15224.52001.24904.969034.300000.18731.642519.17933.87401.74005.845046.980000.21161.855723.68343.63802.21906.649059.020000.22491.972426.31850.19502.55207.103066.740000.23962.101329.36459.00802.98907.662076.870000.25122.202831.86268.45103.45608.215087.550000.25472.233332.62872.64003.65308.415091.93000and the model propeller open water cherectoristic curves,00.10.20.30.40.50.00.20.40.60.81.01.21.4f(x) = − 1.22409 x² − 1.26679 x+ 1.27474R² = 0.999986650687505J as a function of KTmKTmJTm0.500 0.700 0.900 1.100 1.3000.00.10.20.30.40.5f(x) = − 0.186253 x²− 0.215815 x + 0.585875R² = 0.999881359951052KTm as a function of JJTmKTm0.5000.7000.9001.1001.3000.00.10.1f(x) = − 0.0395494 x²− 0.00484842 x + 0.0848723R² = 0.99977080111346KQm as a function of JJKQmfill in the coresponding blanks in the next table:KTmKQmJaJTm @KTmKQTm @KTmWTm1-WTmηRt1-t