Assignment-1 Air Standard Cycles 1. What do u mean by air standard cycle? List assumptions for air standard cycle & give reasons why air standard cycle differs from actual cycle. 2. Derive an equation of efficiency, work output and mean effective pressure for Otto cycle. 3. Derive an equation of efficiency, work output and mean effective pressure for Diesel cycle. 1. An engine working on Otto cycle has the following condition: Pressure at the beginning of compression is 1 bar and pressure at the end of compression is 11 bar. Calculate the compression ratio and air-standard efficiency of the engine. Assume γ = 1.4. 2. In an Otto cycle air at 17 and 1 bar is compressed adiabatically until the pressure is 15 bar. Heat is added at constant volume until the pressure rises to 40 bar. Calculate the airstandard efficiency, the compression ratio and the mean effective pressure for the cycle. Assume C p = 1.004 kj/kgk and R = 8.314 kj/kmol K. 3. In an S.I. engine working on the Otto cycle, compression ratio is 5.5. The pressure and temperature at the beginning of compression are 1 bar and 27 respectively. The peak pressure is 30 bar. Determine the pressure and temperature at the salient points, the air standard efficiency and mean effective pressure. Assume ratio of specific heats to be 1.4 for air. 4. 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 5. A Diesel engine has a compression ratio of 20 and cut takes place at 5 % of the stroke. Find the air standard efficiency. Assume γ = 1.4. 6. In an engine working on Diesel cycle inlet pressure and temperature are 1 bar and 17 respectively. Pressure at the end of adiabatic compression is 35 bar. The ratio of expansion i.e. after constant pressure heat addition is 5. Calculate heat addition, heat rejection and efficiency of the cycle. Assume γ = 1.4, C p = 1.004 kj/kgk and C p = 0.717 kj/kgk. 7. 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.
8. 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. Assignment-2 Fuel-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 1. What will be the effect of percentage change in the efficiency of Otto cycle having a compression ratio of 8, if the specific heat at constant volume increases by 1.1 percent? Ans: -0.704% 2. 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% 3. The following particulars relate to a Diesel cycle: Compression ratio = 18, cut-off = 5% of stroke, mean specific heat Cv for cycle = 0.71 kj/kg K, characteristic gas constant = 0.285 kj/kg K. If the mean specific heat for the air standard cycle increases by 2% determine the percentage change in the air standard efficiency. Ans: -1.147% 4. 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% 5. 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) 6. 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) 7. 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 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 % Assignment-3 Combustion 1. Explain construction and working of Junker s gas calorimeter with neat sketch. Assignment-4 Fuel supply system for SI and CI engine 1. Explain with neat sketch working Simple Carburettor. Also explain Drawback and application of simple Carburettor. 2. With neat sketch explain working principle and constructional detail of Bosch fuel injection pump. 3. Describe different types of injection nozzles and discuss their relative advantages and disadvantages. 4. What is the function of carburetor? What is carburetion 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. Assignment-5 Ignition and Governing System 1. Explain Ignition Requirement. Explain the working of battery ignition system. State its advantages and disadvantages over magneto ignition system. 2. Describe a high tension magneto ignition system and compare its advantages and disadvantages with a coil ignition system. 3. State the various methods of governing of IC engines and discuss any one of them. Assignment 6 Supercharging 1. Define Supercharging And Give Its Advantage And Disadvantage. Give Limitation Of Supercharging. 2. Which are the supercharging limitation for SI engine and CI engine? 3. Explain method of supercharging. 4. What do you mean by turbo charging? Write advantage and limitation of turbo charging. Assignment-7 Combustion in SI and CI Engines 1. What do you understand by knock in S.I. Engines? Explain this phenomenon? How does the knock in S.I. Engines differ from the knock in C.I. Engines? 2. Explain with neat sketch Combustion stages in S. I. Engine. Also define Auto ignition Temperature. 3. What are basic requirements of good spark ignition engine combustion chamber and general principles of spark ignition combustion chamber 4. Explain the phenomenon of diesel knock. Compare it with the phenomenon of detonation in SI engine. 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.
Assignment-9 Measurement and Testing of IC engines 1. Explain the Methods of obtaining Friction Power and explain any one of them in details. 2. Explain the importance of engine testing. Example 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 Assignment-10 Engine Emission and their control 1. Write brief notes on: Euro Norms and Testing of IC engine as per IS. 2. What are the major pollutants from the exhaust of gasoline &diesel engines? What are the detrimental effects of these pollutants? 3. Write down Bharat Stages of emission norms in brief for cars and two wheelers. 4. Explain different methods of measurement of pollutants in exhaust gases.