Reference no: EM132256922

Questions -

Question 1 - Explain with the aid of a sketched P-V diagram, where appropriate, the following "standard" processes;

• Isobaric
• Isochoric
• Isothermal
• zero heat transfer
• polytropic expansion and compression

Question 2 - 0.22 m³ of air at 89 KN/N² guage pressure and 23^oC are polytropically compressed in an engine cylinder to a volume of 0.092 m³, the compression index is 1.35.

Calculate:

a) The final guage pressure

b) The final temperature

c) The mass of air in the cylinder

Question 3 - A quantity of gas occupies a volume of 0.3m³ at a pressure of 100 KN/m² and a temperature of 200C. The gas is compressed isothermally to a pressure of 500 KN/m² and then expanded adiabatically to its initial volume. Determine, for this quantity of gas:

(i) The heat received or rejected (state which) during the compression,

(ii) The change of internal energy during the expansion,

(iii) The mass of gas

Assume for this gas that γ = 1.4 and C_p = 1.0 KJ/kg K.

Question 4 - After ignition of the fuel mixture at the top of the stroke, an internal combustion engine cylinder contains 0.1 litre of hot gas at a temperature of 1500^oC and a pressure of 7MPa (absolute). The hot gas expands adiabatically to the bottom of the stroke.

The compression ratio is 10:1, C_p = 1.0 KJ/kgK and C_v = 0.72 KJ/kgK.

Determine the following,

(i) Temperature and pressure at the bottom of the stroke.

(ii) Work transfer during the stroke.

(iii) Internal energy change during the stroke.

(iv) Heat flow from the cylinder during the stroke.

Question 5 - A gas at a pressure of 1.4 MN/m² and temperature of 360^oC is expanded adiabatically to a pressure of 100 KN/m². The gas is then heated at constant volume until it again attains 360^oC when its pressure is found to be 220 KN/m² and finally it is compressed isothermally until the original pressure of 1.4 MN/m² is attained. Sketch the P-V diagram for these processes and if the gas has a mass of 0.23kg, find,

a. The value of the adiabatic index 'γ'.

b. Change in internal energy during the adiabatic expansion ΔU = m.Cv. (T₂ - T₁)

Take C_p for the gas as 1.004 KJ/kg K.

Question 6 - A compression ignition engine when tested gave an indicator card having area 2950mm² and length 68mm. The calibration factor was 0.2 bar / mm. The mechanical efficiency of the engine was 80%.

Calculate the IMEP and the BMEP.

Question 7 - A four cylinder two stroke cycle petrol engine develops 36 KW at 3000 rpm. The mean effective pressure of each is 900 KN/m² and mechanical efficiency is 83%.

a) Calculate the diameter and stroke of each cylinder if the stroke to bore ratio is 1.4.

b) Calculate the brake specific fuel consumption of the engine, if brake thermal efficiency is 29%. The calorific value of petrol is 45.8 MJ/kg.

Question 8 - A four cylinder four stroke petrol engine of 90mm bore and 95mm stroke gave the following results when tested at 300rpm.

Mean Effective Pressure:

Cylinder 1 = 1015 kPa

Cylinder 2 = 998 kPa

Cylinder 3 = 996 kPa

Cylinder 4 = 992 kPa

Net brake load = 340 N

Brake arm = 460mm

Fuel consumption = 20Litres/hr

Assuming that petrol has an energy content of 46.5 MJ/kg and a relative density of 0.74, determine the following,

(a) Indicated power

(b) Brake power

(c) Mechanical efficiency

(d) Specific fuel consumption

(e) Indicated thermal efficiency

(f) Brake thermal efficiency.