For a two cylinder, four stroke cycle engine the bore is 108 mm and the stroke is 135mm. During a test with the engine running at a speed of 16.5 revs/s the fuel consumption inan hour is 2.5 kg. The calorific value of the fuel is 45.5 MJ/kg. The indicated mean effectivepressure is 558 kN/m2 and the mechanical efficiency is 80 %. Determine;(i) The indicated power and the brake power. (8 marks)(ii) The brake specific fuel consumption. (4 marks)(iii) The thermal efficiency on a brake and on an indicated power basis. (6 marks)(iv) If 40 % of the total energy supplied in the fuel is accounted for by friction, exhaustgases and losses to the surroundings, estimate the rise in temperature of the coolingwater. The cooling water flows at a rate of 215 kg/hour. Take the specific heatcapacity of water as 4200 J/kgK
Question
For a two cylinder, four stroke cycle engine the bore is 108 mm and the stroke is 135mm. During a test with the engine running at a speed of 16.5 revs/s the fuel consumption inan hour is 2.5 kg. The calorific value of the fuel is 45.5 MJ/kg. The indicated mean effectivepressure is 558 kN/m2 and the mechanical efficiency is 80 %. Determine;(i) The indicated power and the brake power. (8 marks)(ii) The brake specific fuel consumption. (4 marks)(iii) The thermal efficiency on a brake and on an indicated power basis. (6 marks)(iv) If 40 % of the total energy supplied in the fuel is accounted for by friction, exhaustgases and losses to the surroundings, estimate the rise in temperature of the coolingwater. The cooling water flows at a rate of 215 kg/hour. Take the specific heatcapacity of water as 4200 J/kgK
Solution
(i) The indicated power (IP) can be calculated using the formula:
IP = IMEP * L * A * N * n / 2
where: IMEP = Indicated Mean Effective Pressure = 558 kN/m^2 = 558000 N/m^2 L = Stroke Length = 135 mm = 0.135 m A = Area of the cylinder = π * (bore/2)^2 = π * (0.108/2)^2 = 0.00915 m^2 N = Engine Speed = 16.5 rev/s n = Number of cylinders = 2
Substituting these values into the formula gives:
IP = 558000 * 0.135 * 0.00915 * 16.5 * 2 / 2 = 47.2 kW
The brake power (BP) can be calculated using the formula:
BP = IP * Mechanical Efficiency
Substituting the given mechanical efficiency of 80% gives:
BP = 47.2 * 0.8 = 37.76 kW
(ii) The brake specific fuel consumption (BSFC) can be calculated using the formula:
BSFC = Fuel Consumption / BP
Substituting the given fuel consumption of 2.5 kg/hour and the calculated BP gives:
BSFC = 2.5 / 37.76 = 0.066 kg/kWh
(iii) The thermal efficiency on a brake power basis (ηb) can be calculated using the formula:
ηb = BP / (Fuel Consumption * Calorific Value)
Substituting the calculated BP, the given fuel consumption and calorific value gives:
ηb = 37.76 / (2.5 * 45.5) = 0.33 or 33%
The thermal efficiency on an indicated power basis (ηi) can be calculated using the formula:
ηi = IP / (Fuel Consumption * Calorific Value)
Substituting the calculated IP, the given fuel consumption and calorific value gives:
ηi = 47.2 / (2.5 * 45.5) = 0.41 or 41%
(iv) If 40% of the total energy supplied in the fuel is accounted for by friction, exhaust gases and losses to the surroundings, then the energy absorbed by the cooling water is 60%. The rise in temperature of the cooling water can be calculated using the formula:
ΔT = Energy Absorbed by Water / (Mass Flow Rate of Water * Specific Heat Capacity of Water)
Substituting the given values gives:
ΔT = 0.6 * 2.5 * 45.5 * 10^6 / (215 * 4200) = 80.4 K
Similar Questions
During a dynamometer test a 4 cylinder, 4 stroke diesel engine develops an indicated meaneffective pressure of 850 KN/m2 at an engine speed of 2000rpm. The engine has a bore of93mm and stroke of 91mm. The test runs for 5 min, during which time 0.8kg of fuel isconsumed. Mechanical efficiency is 83%. Calorific value of the fuel is 43MJ/kg.Calculatei) The indicated power and Brake power (6 marks)ii) The energy supplied from the fuel per second. (5 marks)iii) The indicated and brake thermal efficiency. (6 marks)iv) The Brake specific fuel consumption in kg/KWh.
A Heat Engine has a power output of 17.4 kW and rejects heat to a heat sink at a rate of 2.69 MJ/minute. The Thermal Efficiency of this Engine is:Group of answer choices72%15%28.6%38.8%
A performance test on a single cylinder, four stroke, reciprocating internalcombustion petrol engine produced the following data:The indicated mean effective pressure 119.7kN/m2The swept volume 0.014m3Engine speed 2000rev/minThe mechanical efficiency 72%Fuel consumption 2 x 10-6 m3/sDensity of fuel 740kg/m3Calorific value of fuel 43,000 kJ/kgAir flow rate into the engine 0.025 m3/sAir density 1.2 kg/m3Exhaust temperature 502oCSpecific heat capacity of exhaust gas 1.01kJ/kgKCooling water inlet temperature 12oCCooling water outlet temperature 52oCCooling water flow rate 0.12kg/sSpecific heat capacity of cooling water 4.2kJ/kgKAir temperature at engine inlet 12oC.(i) Carry out an energy balance on the engine and show that the first law ofthermodynamics is valid.
A heat engine has an efficiency of 35.0% and receives 150 J of heat per cycle. How much work does it perform in each cycle?
The input power to machine is 18000W. Friction converts 1000J of energy into heat each second. What is the efficiency of the machine?Question 1Answera.94.74%b.94.44%c.100%d.5.56%
Upgrade your grade with Knowee
Get personalized homework help. Review tough concepts in more detail, or go deeper into your topic by exploring other relevant questions.