### AT6301 Automotive Engines Important Questions

AT6301 Automotive Engines Important Questions Unit I

1. Compare two stroke engine and four stroke engine with regard to power output and thermal efficiency.
2. Briefly explain the working principle of four stroke SI engine (OR) two stroke CI engine.
3. a) Compare the SI engine and CI engine. b) Write the major difference between Otto cycle and Diesel cycle?
4. Compare the two stroke and four stoke engine.
5. In an SI engine working on the ideal Otto cycle the compression ratio is 6. The pressure and the temperature at the beginning of compression are 1.013 bar and 27°C respectively. The Peak pressure is 30 bar. Determine the pressure and temperature at the salient points, the air standard efficiency and the mean effective pressure. Assume γ = 1.4
6. An engine working with dual cycle has a compression ratio of 10 and 2/3 of heat of combustion is liberated at constant volume and the remainder at constant pressure. The pressure and temperature at the beginning are 1 bar and 27°C. and the maximum pressure is 40 bar. Find the temperature at the end of compression and expansion. And the air standard efficiency. Assume γ = 1.4

Unit II

1. Explain with neat sketch about common rail diesel injection system.
2. Explain the working principle of Jerk type pump &amp; Unit injector.
3. A simple jet carburetor is required to supply 4.6 Kg of air per minute. The pressure and temperature of air are 1.013 bar and 25°C respectively. Assuming flow to be isentropic and compressible and velocity co-efficient as 0.8. Calculate the throat diameter of the choke for air flow velocity of 80 m/s.
4. A simple carburetor is designed to supply 6 kg of air per minute and 0.4 kg of fuel per minute. The density of the fuel is 770 kg/m3. The air is initially at 1 bar and 17 C. Calculate the venture throat diameter if the velocity of air at throat is 100 m/s. Assume Cda=0.84. Cdf=0.65 and γ=1.4. If the pressure drop across the fuel metering orifice is 0.85 of the pressure at the throat.
5. Explain the working principle of Constant vacuum type carburetor

Unit III

1. Briefly explain about the ignition timing with respect load and speed.
2. Briefly explain about various types combustion chamber designed for SI engines
3. Compare the Knock in SI Engine and CI Engine. Explain briefly the process of knocking combustion in a SI Engine
4. Explain briefly the Stages of combustion in CI Engine.
Unit IV

1. Briefly explain about the Eddy current Dynamometer &amp; Hydraulic Dynamometer.
2. The following particulars were obtained in a trial on a four stroke gas engine: Duration of trial = 1 hour, Revolutions = 14000, Number of missed cycle = 500, Net brake load = 1470 N, Mean effective pressure = 7.5 bar, Gas consumption = 20000 liter, L.C.V. of gas at supply conditions = 21 KJ/Liter, Cylinder diameter = 250 mm, Stroke = 400 mm, Effective brake circumferences = 4 m, Compression ratio = 6.5:1 Calculate i) Indicated power ii) Brake power iii) Mechanical efficiency iv) Indicated thermal efficiency
3. Explain about the Supercharging &amp; Turbocharging methods.
4. Explain : Turbo charging with waste gate &amp; variable geometry

Unit V

1. Explain the requirements of lubrication system.
2. Briefly explain with neat sketch about the wet sump &amp; Dry sump lubrication system.
3. Briefly explain with neat sketch about the Splash type lubrication system
4. Explain about properties of lubricant

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