Question

Question 2 (a) In a 4-cylinder 4-stroke internal combustion engine, the cylinder bore is 78 mm and the stroke length is 95 mm. In a test, the brake mean effective pressure is 850 kPa and the speed is 2400 rpm. (i) What is the total displacement volume of the engine? Express your answer in mm’, mL, and m?. (ii) Calculate the work done by gas on one piston in one full cycle. (iii) Calculate the power output of the engine. [7] (b) Explain the term “normalisation of deviance” with reference to at least one well-known example of a failure or error in mechanical engineering. [7] (c) An electric motor has its highest efficiency at a speed of 1520 rpm. It propels a car with wheels of diameter 0.46 m. When the car is driving at 45 km/h, the motor should be running at maximum efficiency. (i) What gear ratio from motor to wheel should be used? (ii) Name and sketch two types of mechanism that could provide the required gearing. [6]

Answer 1

#3. la) Given : Bore, da 78 mm Stroke, il 95 mm Brake mean effective pressure, B hep = 850 kPa Speed, n 2400 rpm (i) Total displacement volume of engine és V =4x -d² I ㅈ (0.078)*(0.095) 4 c V =4x4.53 x 10-4 m3 = 18.12 %10-4 m3. 3 3 or, V - 4x4.53 x 105 mm =18.12 1005 mm or, V =4*4.53 X 10-1.e - 4x453 m l. 1812 ml. work done by gas on one biston in one full cycle Bme p 'X V*N 2 - 850x109 x 18.12 x 10 4 x 2400 2 X 60 1848.24 Go 30.804 Kw. (in) Power developed is given by 123.216 P = 4 x 30.804 kw