Name of the College : DMI College OF Engineering
Department : Mechanical Engineering
Subject Code/Name : ME2301 THERMAL ENGINEERING
Degree : B.E
Website : dmice.ac.in
Document Type : Question Bank
Thermal Engineering : https://www.pdfquestion.in/uploads/dmice.ac.in/1490-ME2301.docx
DMI Thermal Engineering Question Paper
Unit-I
Part-A :
** Define compression ratio.
** Sketch the Otto cycle on P-V and T-S planes.
** Draw the P-V and T-S diagram of Diesel cycle.
Related : DMI College OF Engineering ME2303 Design Of Machine Elements, B.E Question Bank : www.pdfquestion.in/1503.html
** Write the formula to find the air standard efficiency of Otto cycle.
** Write the formula to find the air standard efficiency of Diesel cycle.
** What is mean effective pressure?
** What is air standard efficiency?
** What is cut-off ratio?
** What is the effect of cut-off ratio in diesel cycle?
** Draw the P-V and T-S diagram of Dual cycle.
** Draw the P-V and T-S diagram of Brayton cycle.
** Write the formula to find the air standard efficiency of Brayton cycle.
** Write the formula to find the air standard efficiency of Dual cycle.
** What is Relative efficiency?
** What is swept volume?
** What is clearance volume?
** Which cycle is called as mixed cycle or limited pressure cycle?
** What is expansion ratio?
** What is an air standard cycle?
** In an Otto cycle, pressure ratio during compression is 11. Calculate the air standard efficiency.
Unit-II
Part-A :
** What is an internal combustion engine?
** Name any five parts of Internal combustion engine.
** What are the different types of engine cooling methods?
** What are the functions of lubrication?
** What are the desirable properties of lubricating oil?
** Define specific fuel consumption.
** What is Brake power?
** What is SIP?
** What is the use of transfer port in two stroke engines?
** Name the four strokes of a four stroke engine.
** What is valve timing diagram?
** What is port timing diagram?
** What is the range of compression ratio for Diesel engine?
** What is the range of compression ratio for petrol engine?
** Write the firing order of four cylinder engine.
** Name some emissions comes out from Diesel engine.
** What is Brake thermal efficiency?
** What is Heat balance sheet?
** What is mechanical efficiency?
** What is frictional power?
Part-B :
1. (i) Define I.C.engine. How are these engines classified.
(ii) What are the main differences between 4- stroke and 2- stroke engines?
2. (i) Describe the working principle of a four- stroke cycle petrol engine and draw its
valve timing diagram.
(ii) Describe the working principle of a four- stroke cycle Diesel engine and draw its valve timing diagram.
3. (i) Describe the working of two stroke cycle petrol engine.
(ii) Describe the working of two stroke cycle Diesel engine.
4. (i) What are the advantages and disadvantages of a two stroke cycle engine over a four stroke cycle engine?
(ii) What are the differences between a petrol engine and a Diesel engine?
5. (i) Draw the circuit diagram and describe the working of battery ignition system used for a four-cylinder petrol engine.
(ii) Draw the circuit diagram and describe the working of Magneto ignition system used for a four-cylinder petrol engine.
6. (i) What is the purpose of cooling I.C.engine? Describe the water cooling system. What are its advantages and disadvantages?
(ii) Describe with neat sketches the working of fuel injector used in diesel engine.
7. The following particulars refer to a 2 stroke diesel engine:
I. Bore=10 cm, stroke=15 cm, piston speed= 300 m/min, torque developed=58Nm, mechanical efficiency=80%, indicated thermal efficiency=40%, calorific value of fuel used=44000KJ/kg. Determine: (a) indicate power, (b) indicated mean effective pressure, and (c) fuel consumption per KW hour on brake power basis.
8. Atwo stroke cycle, 21cmx 28cm stroke, single cylinder oil engine gives the following
results on test:
Speed =350 r.p.m
Net brake load =620 N
Diameter of brake drum =1m
Oil consumption =4.25 kg/hr.
I.m.e.p. =275 KN/m2
Heating value of fuel used =43000KJ/kg.
Air- fuel ratio by weight =32
Temperature of air in test room =20° C
Temperature of exhaust gases =370°C
Calculate (a) the indicated power, (b) the brake power, (c) indicated thermal efficiency,(d) Brake thermal efficiency, and (e) percent heat loss to exhaust gases. Assume a mean Cp of 1 for the exhaust gases.
9. 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.
I. The power- measurements were as follows:
II. With all cylinders working= 16.25KW, With No. 1st cylinder cut off= 11.55KWh(B.P), With No. 1st cylinder cut off= 11.55KWh(B.P.) , With No. 2nd cylinder cut off= 11.65KWh (B.P.) , With No. 3rd cylinder cut off= 11.70KWh (B.P.), With No. 1st cylinder cut off= 11.50KWh(B.P.)
III. Find (a) The I.P. of the engines
IV. (b) The mechanical efficiency
V. (c) Indicated thermal efficiency if C.V. of fuel used is 42,000 KJ/kg and
VI. (d) Also find the relative efficiency on I.P. basis assuming clearance volumes 65 cu. Cm.
10. A test on single cylinder, 4- stroke oil engine, having bore 180 mm and stroke 360 mm gave the following results: speed 290 r.p.m.; brake torque 392 Nm ; indicated mean- effective pressure 7.2 bar; oil consumption 3.5 kg/hr; cooling water flow 270 kg/hr; cooling water temperature rise 36°C; air- fuel ratio by mass 25; exhaust gas temperature 415°C; barometric pressure 1.013 bar; room temperature 21°C. The fuel has calorific value of 45, 200KJ/kg and contains 15% of hydrogen by mass. Calculate:
b. the indicated thermal efficiency, and
c. the volumetric efficiency based on atmospheric conditions.
I. Draw up a heat balance sheet in terms of KJ/min. Take R= 0.287KJ/kg°C, Cp for dry exhaust gases= 1.0035 KJ/kg-K and Cps for superheated steam= 2.093KJ/kg-K.
(ii) Discuss about the combustion chambers in Petrol engine.
(iii) Discuss about the combustion chambers employs in Diesel engine.