Assignment-1 Introduction 1. Compare S.I. engines with C.I engines. 2. Explain with the help of neat sketch, the working of a 2-stroke petrol engine. 3. Derive an equation of efficiency, work output and mean effective pressure for Otto cycle. 4. Derive an equation of efficiency, work output and mean effective pressure for Diesel cycle. Examples 1. A spark ignition engine working on ideal Otto cycle has the compression ratio 6. The initial pressure and temperature of air are 1 bar and 37. The maximum pressure in the cycle is 30 bar. For unit mass flow, calculate a. P, V and T at various salient points b. The ratio of heat supplied to heat rejected Assume γ = 1.4, R = 8.314 kj/kmol K 2. The initial conditions for an air standard Diesel cycle operating with a compression ratio of 15:1 are 0.95 bar and 17. The heat added is 1800 kj/kg. Calculate the pressure and temperature at the end of each process of the cycle, also determine thermal efficiency and mean effective pressure of the cycle. 3. A compression ignition engine working on Diesel cycle operates at a compression ratio of 15 using Diesel oil of 42000 kj/kg. The inlet pressure and temperature are 1 bar and 300 K. The air-fuel ratio is 21. Calculate for air standard cycle a. The temperature and pressure at the salient points. b. The air standard efficiency and c. Mean effective pressure. Darshan Institute of Engineering and Technology, Rajkot 1
Assignment-2 Fuel air and Actual air Cycles 1. Enlist the assumptions which are made for fuel-air cycle analysis. 2. Explain the phenomenon of dissociation. Also explain its effect on maximum temperature and power. 3. Explain following: a. Burning time loss factor b. Heat loss factor c. Pumping and friction loss factor 4. Explain with neat sketch valve timing diagram for Petrol engine. 5. Explain with neat sketch valve timing diagram for Diesel engine. Also explain deviation of an actual cycle from an ideal cycle. Examples 1. Calculate the percentage change in efficiency of air standard Otto cycle having a compression ratio of 7, if the specific heat at constant volume increases by 2 %. Ans: -1.32% 2. What will be the effect on the efficiency of a diesel cycle having a compression ratio of 20 and a cut-off takes place at 8% of the swept volume, if the Cv increases by 1%. Take Cv = 0.717 kj/kg K and R = 0.287 kj/kg K. Ans: -1.197% 3. A petrol engine using a compression ratio 7 and air-fuel ratio of 15:1 has the pressure and temperature at the end of suction stroke as 1 bar and 57 C respectively. The fuel used has a calorific value of 44000 kj/kg. Compression follows the law specific heat at constant volume is given by the relation, C 1.33 pv constant and 4 V 0.718 2.1 10 T, where T is in Kelvin. Determine the maximum pressure and temperature in the cylinder and compare this value with that of constant specific heat, Cv = 0.718 kj/kg K. Ans: (T = 2918.4 K & 4457.3 K, P = 61.904 bar & 94.54 bar) 4. A Diesel engine uses a compression ratio of 16 and at the end of compression the temperature of the air is 1100 K. Now the air is supplied at constant pressure by burning fuel of calorific value of 44200 kj/kg K and the fuel-air ratio is 0.04:1. Specific heat at constant volume T is given as: CV 4 0.72 2 10 T where T is in Kelvin. Determine the maximum temperature in the cylinder and compare this value with that of constant specific heat, Cv = 0.72 kj/kg K. Ans: (T = 2356.7 K & 2788.18 K) 5. In an oil engine, working on dual combustion cycle the temperature and pressure et the beginning of compression are 87 C and 1 bar. The compression ratio is 14:1. The heat Darshan Institute of Engineering and Technology, Rajkot 2
supplied per kg of air is 1700 kj, half of which is supplied at constant volume and half at constant pressure. Take Cv = 0.718 + 2.1 X 10-4 T, where T is in Kelvin. Calculate (i) The maximum pressure in the cycle (ii) The percentage of stroke at which cut-off occurs. Ans: (i) 73.22 bar (ii) 2.42 % Darshan Institute of Engineering and Technology, Rajkot 3
Assignment-3 Combustion 1. Explain construction and working of Junker s gas calorimeter with neat sketch. 2. Explain working and construction of bomb calorimeter. Darshan Institute of Engineering and Technology, Rajkot 4
Assignment-4 Fuels & its supply system for SI and CI engine 1. Explain with neat sketch of simple carburetor and its limitations. 2. What do you mean by solid injection system? Enlist the types of solid injection system. Explain with neat sketch of common rail fuel injection system. 3. With neat sketch explain working principle and constructional detail of Bosch fuel injection pump. 4. Describe different types of injection nozzles and discuss their relative advantages and disadvantages. Examples 1. A petrol engine consumes 7.5 kg of petrol per hour. The specific gravity of the fuel is 0.75. The air temperature is 25 C. The air fuel ratio is 15. The choke tube has a diameter of 22 mm. Calculate the diameter of the fuel jet of a simple carburetor. Top of the jet is 4 mm above the petrol level in the float chamber. Take coefficient of discharge as 0.82 and 0.7 for air and fuel respectively. Atmospheric pressure = 1.013 bar. 2. The venture of a simple carburetor has a throat diameter of 20 mm and the coefficient of air flow is 0.85. The fuel orifice has a diameter of 1.25 mm and the coefficient of fuel flow is 0.66. The petrol surface is 5 mm below the throat. Find a) the air-fuel ratio for a pressure drop of 0.07 bar when the nozzle lip is neglected; b) the air-fuel ratio when the nozzle lip is taken into account; c) the minimum velocity of air or critical air velocity required to start the fuel flow when nozzle lip is provided. Take density of air and fuel as 1.2 and 750 kg/m 3 respectively. Darshan Institute of Engineering and Technology, Rajkot 5
Assignment-5 Ignition and Governing System 1. Describe a high tension magneto ignition system and compare its advantages and disadvantages with a coil ignition system. 2. Give the basic comparison between battery ignition and magneto ignition system. 3. What type of governing used in S.I engine and C.I engine? Explain any one of them. Darshan Institute of Engineering and Technology, Rajkot 6
Assignment 6 Supercharging 1. Define Supercharging and give its advantages. Also list the methods of supercharging and explain with sketch any one of them. 2. Explain the need of supercharging and with a neat sketch describe buchi type turbocharging. 3. State effect of supercharging on following parameters. a) Power output b) Mechanical efficiency c) Fuel consumption. Darshan Institute of Engineering and Technology, Rajkot 7
Assignment-7 Combustion in SI and CI Engines 1. Explain stages of combustion in C.I. engines. 2. Classify different types of combustion chambers in S.I and C.I engine. Also explain any one of them. 3. Explain briefly the phenomenon of Diesel knock. 4. Explain with help of P-ϴ diagram the combustion in S.I. engine. Discuss how the detonation and pre-ignition affect the combustion in S.I. engine. 5. Enlist various factor by which diesel knock can be controlled. 6. Explain following terms in brief related to surface ignition in SI engine: a) Run on surface ignition, b) Run away surface ignition c) Wild ping d) Rumble. Darshan Institute of Engineering and Technology, Rajkot 8
Assignment-8 Engine Lubrication and Cooling 1. Explain with neat sketch splash lubrication system. 2. What are the different methods of cooling I.C. engine? Compare different methods. Darshan Institute of Engineering and Technology, Rajkot 9
Assignment-9 Measurement and Testing of IC engines 1. Describe the Morse test. Write the assumptions made and limitation of this test.. 2. Discuss a Heat balance sheet in 350 words. Examples 1. In a Morse test with four cylinder four stroke petrol engine, the following data were obtained for a particular setting and speed. Brake power with all cylinders working = 32.0 Brake power with no. 1 cylinder cut out = 21.6 Brake power with no. 2 cylinder cut out = 22.3 Brake power with no. 3 cylinder cut out = 22.5 Brake power with no. 4 cylinder cut out = 23.0 Estimate the indicated power of the engine and its mechanical efficiency. 2. A 4-cylinder, 4-stroke petrol engine 6 cm bore and 9 cm stroke was tested at constant speed. The fuel supply was fixed to 0.13 kg/min and plugs of 4-cylinders were successively short-circuited without change of speed. The power measurements were as follows: With all cylinder working=16.25 kw With No.1st cylinder cut-off=11.55 kw With No.2nd cylinder cut-off =11.65 kw (BP) With No.3rd cylinder cut-off =11.70 kw (BP) With No.4th cylinder cut-off =11.50 kw (BP) Find (a) The IP of engine (b) Mechanical efficiency (c) Indicated thermal efficiency if CV of fuel used is 42000 kj/kg and (d) Find the relative efficiency on IP bases assuming clearance vol. =60 cm 3 3. The following observations were recorded from test on a single cylinder four stroke oil engine cylinder bore =150mm, engine stroke =250mm engine speed 420rpm, brake torque=217nm, fuel consumption 2.95 kg/h, calorific value of fuel=44000kj/kg cooling Darshan Institute of Engineering and Technology, Rajkot 10
Assignment-10 Engine Emission and their control 1. What are the major pollutants from the exhaust of gasoline &diesel engines? What are the detrimental effects of these pollutants? 2. Write down Bharat Stages of emission norms in brief for cars and two wheelers. Darshan Institute of Engineering and Technology, Rajkot 11
Assignment-11 Diesel Power Plant 1. Discuss the application of diesel plants and its advantages and disadvantages. 2. Draw a layout of diesel engine power plant. Darshan Institute of Engineering and Technology, Rajkot 12