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PAAVAI COLLEGE OF ENGINEERING

PACHAL, NAMAKKAL.

UNIT TEST-1

Date: 25/07/13 Dept: Automobile Engineering Max Marks: 50.

Year/Sem: II/IV Vehicle Design And Data Characteristics Duration: 1Hrs 30minsPART A

Answer Any 5 Questions (10x2=20)

1. What is the difference between the traction and tractive effort

2. Write rolling resistance & gradient resistance?

1. How is vehicle speed related to engine rotation

2. Define specific fuel consumption

3. What are the factors on which the mechanical efficiency depend

4. Define the terms throw, piston displacement

Define indicated thermal efficiency, brake thermal efficiency

PART B

Answer All Questions ( 40 Marks

1. a) The engine of a jeep is known to be able to provide 40.5kw for propulsion purpose in a certain applica

the jeep weighing 12459 N is required to pull a trailer of gross weight 10673N at a speed of 57.75km/h ingear on level. the resistance to motion is given by the equation R=Aw+bv 2 ,where a=0.016 and b=0.055,W

in N and V in km/h find out if the jeeps adequate for the job, if the transmission efficiency is 90%.what is

pull in the coupling at this speed? If the available power is just utilized in top gear by suitable loading

trailer, what is the pull in the coupling at 57.75km/h? (8(Or)

b) What is the difference between (a)IP,BP,FP (b)IMEP and BMEP

2. (a) An eight cylinder automobile engine of 85.7 mm bore and 82.5 mm stroke with a compression ratio of

tested at 4000 rpm on a dynamometer which has a 0.5335 m arm, During a 10 minute test at a dynamome

scale beam reading of 400 N, 4.55 kg of gasoline for which the heating value is 46,000 kJ/kg are burnt, andis supplied to the carburetor at the rate of 5.44 kg/mm. Find (i) the b.p delivered, (ii) the B.M.E.P, (iii)

B.S.F.C, (iv) the specific air consumption, and (e) the brake thermal efficiency.

(Or)

(b). a truck weight 100KN and the engine develops of 97KW at 2400 rpm the transmission efficienc

90% in top gear of 3.4:1 and 85% in third gear of 8.4:1. The performance of the vehicle is such that it will

reach a speed of 86.8km/hr at 2400 rpm at wide open throttle when running on the level in still air, and atsame engine speed at the third gear it will just climb a gradient of 1 in 14. If the total resistance in Newto

given by the formula R= KW+Ka AV2+W sin 0

Where A is in m2 V in Km/hr and W in N calculate K and Ka and hence the engine power requiredclimbing a grade of 1 in 40 at 48Km/hr in top gear. How much more weight can be added to the vehicle to

the engine power fully under the above condition. Frontal area of the truck is 5.575m2.

3. (a) A Leyland truck has a gross vehicle weight of 89026N engine displacement is 10m3, power 77.3KW

At governed speed of 2400RPM and maximum torque 345.8n-m at 1400 RPM rear axial ratio is 6.166:1

speed reduction ratio in transmission is 1.605:1 drive line losses amount to 10.7KW at 2400 RPM and 6.3K

at 1400RPM. Tire size is 0.4572m X 1.016m effective wheel diameter 0.950m fontal area of truck is 6.95

Calculate the grade which the vehicle can climb in fourth gear in still air condition.a. At governed engine speed

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b. At a speed of maximum torque. In the equation R= KW+Ka AV2 where K=0.044 Ka= 0.0462 and V

Km/hr

(Or)(b) The coefficient of rolling resistance for a truck weight 62293.5N is 0.018 and the coefficient of

resistance is 0.0276 in the formula R= KW+Ka AV2.The transmission efficiency in top gear of 6.2: 1 is 9

and that in the 2nd gear of 15:1 is 80% the frontal area is 5.574m2. If the truck has to have a maximum spee

88Km/hr in top gear, calculate,1. The engine brake power required

2. The engine speed if the driving wheels have an effective diameter of 0.8125m

3. The maximum Grade the truck can negotiate at the above engine speed in 2nd gear4. The maximum draw/pull available on level at the above engine speed in 2nd gear.