Worksheet.docx - ADDIS ABABA SCIENCE AND TECHNOLOGY...

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ADDIS ABABA SCIENCE AND TECHNOLOGY UNIVERSITYIC Engines and Reciprocating MachinesWorksheet-I1.A 42.5 kW engine has a mechanical efficiency of 85%. Find the indicated power andfrictional power. If the frictional power is assumed to be constant with load, what will bethe mechanical efficiency at 60% of the load?2.A four stroke, four cylinder diesel engine running at 2000 rpm develops 60 kW. Brakethermal efficiency is 30% and calorific value of fuel is 42MJ/kg. Engine has a bore of120 mm and stroke of 100 mm. Take ρa= 1.15 kg/m3, air-fuel ratio is 15:1, mechanicalefficiency is 80%. Calculate (i) fuel consumption (kg/s) (ii) air consumption (m3/s) (iii)indicated thermal efficiency (iv) volumetric efficiency (v) brake mean effective pressure(vi) mean piston speed.3.A single cylinder, four stroke hydrogen fuelled spark-ignition engine delivers a brakepower of 20 kW at 6000 r.p.m. The air-gas ratio is 8:1 and the calorific value of fuel is11000 kJ/m3. The compression ratio is 8. If volumetric efficiency is 70%, indicatedthermal efficiency is 33% and the mechanical efficiency is 90%. Calculate the cubiccapacity of the engine.4.A four stroke petrol engine at full load delivers 50 kW. It requires 8.5 kW to rotate itwithout load at the same speed. Find its mechanical efficiency at full load, half load andquarter load. Also find out the volume of the fuel consumed per second at full load ifbrake thermal efficiency is 25%, given that the calorific value of the fuel = 42 MJ/kg andspecific gravity of petrol is 0.75. Estimate the indicated thermal efficiency.5.Find out the speed at which a four cylinder engine using natural gas can develop a brakepower of 50 kW working under the following conditions. Air-gas ratio 9:1, calorific value

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Term
Fall
Professor
1
Tags
Internal combustion engine, Diesel engine, Engine technology, compression ratio, Internal combustion piston engines