Marine Engines I and Solids III Past Papers PDF - Jomo Kenyatta University

## JOMO KENYATTA UNIVERSITY ### OF ### AGRICULTURE AND TECHNOLOGY #### University Examinations 2023/2024 #### FOURTH YEAR SECOND SEMESTER EXAMINATION FOR BACHELOR OF SCIENCE IN MARINE ENGINEERING #### EMR 2405: MARINE ENGINES I **DATE:** APRIL 2024 **TIME:** 2 HOURS **INSTRUCTIONS:** - This paper c...

## JOMO KENYATTA UNIVERSITY ### OF ### AGRICULTURE AND TECHNOLOGY #### University Examinations 2023/2024 #### FOURTH YEAR SECOND SEMESTER EXAMINATION FOR BACHELOR OF SCIENCE IN MARINE ENGINEERING #### EMR 2405: MARINE ENGINES I **DATE:** APRIL 2024 **TIME:** 2 HOURS **INSTRUCTIONS:** - This paper contains FIVE questions - Question ONE is COMPULSORY and carries 20 MARKS - The other questions carry 20 MARKS each - Attempt question ONE in SECTION A, ONE question from SECTION B and ONE question from SECTION C. - The marks for each part of a question are as indicated - All symbols have their usual meaning unless specified otherwise - Use clear and neat sketches and show all your working - You should have the following for this examination: - Answer booklet - Graph paper - Scientific calculator - Steam Tables - Mobile phones and any written materials relevant to the examination are prohibited in the examination room. - DO NOT WRITE ON THE QUESTION PAPER ## SECTION A (COMPULSORY) ### QUESTION ONE (COMPULSORY) [20 MARKS] a) With the aid of a well labelled diagram describe the operation of a SI four stroke engine. b) Describe the following engine parts as used in internal combustion engine and the materials used to manufacture them. - Injector - Connecting Rod c) Define the following terms as used in internal combustion engines. - Bore - Smart Engine - Homogeneous Charge Compression Ignition Engine d) List six typical additives used in lubrication oil to enhance its lubricity. e) Describe three basic types of oil distribution in internal combustion engines. f) List and describe four parts that makes up the water cooling system. ## SECTION B (ATTEMPT ONE QUESTION) ### QUESTION TWO [20 MARKS] a) Differentiate between the following terms as used in engine lubrication system. - Full flow and bypass oil filtration - Wet and dry sump b) State three characteristics of a good lubricating oil. c) Design the following components of the valve gear mechanism of one of the standby diesel engine of MV Uhuru: The following data are provided: - Bore = 125 mm; stroke 185 mm; - Power = 5.0kW; speed = 1550 rpm; - Maximum gas pressure = 4.2 N/mm². - The valve opens 24° before top dead centre and closes 4º after the bottom dead centre. - It opens and closes with constant acceleration and deceleration for each half of the lift. - The length of the rocker arm on either side of the fulcrum is 120 mm and the included angle is 180°. - The weight of the valve is 3.2 N. Determine: - Size of the valve port. - The maximum lift of the valve. - The thickness of the valve head. - Valve stem diameter. - Valve head diameter . Assume *V₁ = 80 m/s, a = 45° k = 0.42 0 = 62 MPa and width of the valve seat = 0.06 dp*. ### QUESTION THREE [20 MARKS] a) Define the following terminologies as use in internal combustion engine. - Top Dead Centre - Direct Injection - Wide open throttle b) Differentiate between spark ignition engine and compression ignition engines. c) Seco Company Ltd in Mombasa has asked to design a plain carbon steel centre crankshaft for a single acting four stroke single cylinder engine at the dead centre for the following data: - Bore = 455 mm; Stroke = 655 mm; - Engine speed = 190 r.p.m.; - Mean effective pressure = 0.65N/mm²; - Maximum combustion pressure = 3.0 N/mm²; - Weight of flywheel used as a pulley = 56 kN; - Total belt pull = 7.5 kN. - When the crank has turned through 40 from the top dead centre, the pressure on the piston is 1N/mm² and the torque on the crank is maximum. - The ratio of the connecting rod length to the crank radius is 6. Design the following parameters: - The crank-pin. Assume _b = 80 N/mm² and P6 = 12N/mm²_. - The left hand crank web. - The right hand crank web. Assume the width of the flywheel is 512 mm, allowance for gearing and clearance of 150 mm and allowable tensile stress for the shaft _b = 37 N/mm²_. Assume any other data required for the design. ## SECTION C (ATTEMPT ONE QUESTION) ### QUESTION FOUR (20 MARKS) a) State four factors considered when designing a piston. b) List at least six properties of a good antifreeze solution. c) An internal combustion engine operated by JKUAT Mechanical Engineering department as a standby generator has the following engine specifications: - Brake power = 12.5 kW, - Speed = 2500 rpm, - Indicated mean effective pressure = 0.85 N/mm², - Maximum gas pressure = 8.2 N/mm² and - Mechanical efficiency = 85%. Determine: - The dimension of the cylinder, if the stroke length is 1.75 times the cylinder bore. - The wall thickness of the cylinder if the hoops stress is 50 MPa. Assume *p = 9Pm and C = 0.1*. - The size of the stud and the flanges if the permissible tensile stress for the stud is 60 MPa. ### QUESTION FIVE [20 MARKS] a) State two advantages and two disadvantages of water cooled system. b) Describe the two types of water cooled systems. c) Design a cast iron piston for a two stroke marine engine compression ignition engine with the following specifications. - Cylinder bore = 120 mm, - Stroke length = 140 mm - Maximum gas pressure = 6.5 N/mm², - Indicated mean effective pressure = 0.62N/mm², - Mechanical efficiency = 96%, - Fuel consumption = 0.18 kg per brake power per hour, - Higher calorific value = 47550 kJ/kg and - Speed = 3800 rpm. For cast iron allowable tensile stress is 48 N/mm² for the piston head, Constant C = 0.05, *TC - TE = 220°C*, k = 46.6 w/m°C. *Pw = 0,035 N/mm²*, Allowable bending stress for cast iron ring = 90 N/mm², *рь = 0.45 N/mm²*, *på* for bronze = 25 N/mm², *1₁ = 0.45 D*, *d₁ = 0.6do*. Design the following: - Piston Crown. - Radial ribs. - Piston rings. - Piston barrel. - Piston skirt. ## JOMO KENYATTA UNIVERSITY ### OF ### AGRICULTURE AND TECHNOLOGY #### CAT 1 (20 Marks) #### EMR 2405: MARINE ENGINE I **DATE:** 20/02/2024 **TIME:** 1 HOUR **INSTRUCTIONS:** - Describe the following parts and the materials use to manufacture them as used in marine engines. - Cylinder block. - Connecting rod. - Piston. - Valves. - List at least six requirements than a lubricating of internal combustion engines needs to satisfy. - The Department of Mechanical Engineering at Dedan Kimathi University wishes to develop a Hydrogen Engine for the small lawn mowers operated within the University for cutting grass with the following specifications: - Brake power = 4.5 kW, - Speed = 2000 rpm, - Indicated mean effective pressure = 0.45 N/mm² and - Mechanical efficiency of 92%. Determine: - The cylinder dimensions, given the stoke length is 1.4 time the bore. - The wall thickness of the cylinder if the hoop stress is 42 MPa. - The size of the stud when the permissible stress for the stud is 70 MPa. ## JOMO KENYATTA UNIVERSITY ### OF ### AGRICULTURE AND TECHNOLOGY #### CAT 2 #### EMR 2405: MARINE ENGINE I #### TOTAL MARKS: 30 **DATE:** 02/04/2024 **TIME:** 1 HOUR 15 MINUTES **INSTRUCTIONS:** - Design the following components of the valve gear mechanism of one of the standby diesel engine of MV Mkopa: The following data are provided: - Bore = 120 mm; - Stroke 180 mm; - Power = 4.5kW; - Speed = 1500 rpm; - Maximum gas pressure = 3.8 N/mm². - The valve opens 22º before top dead centre and closes 1º after the bottom dead centre. - It opens and closes with constant acceleration and deceleration for each half of the lift. - The length of the rocker arm on either side of the fulcrum is 120 mm and the included angle is 160°. - The weight of the valve is 2.5 N. Determine: - Size of the valve port. - The maximum lift of the valve. - The thickness of the valve head. - Valve stem diameter. - Valve head diameter. Assume *V1 = 80 m/s, a = 45° k = 0.42 0 = 60 MPa and width of the valve seat = 0.06 dp*. - Design a cast iron piston for a two stroke marine engine compression ignition engine with the following specifications. - Cylinder bore = 125 mm, - Stroke length = 145 mm - Maximum gas pressure = 6 N/mm², - Indicated mean effective pressure = 0.56N/mm², - Mechanical efficiency = 95%, - Fuel consumption = 0.12 kg per brake power per hour, - Higher calorific value = 47500 kJ/kg and - Speed = 4000 rpm. For cast iron allowable tensile stress is 45 N/mm² for the piston head, Constant C = 0.05, *TC-TE = 220°C*, k = 46.6 w/m°C. *Pw = 0,035 N/mm²*, Allowable bending stress for cast iron ring = 90 N/mm², *рь = 0.45 N/mm²*, *på* for bronze = 25 N/mm². ## JOMO KENYATTA UNIVERSITY ### OF ### AGRICULTURE AND TECHNOLOGY #### CAT 1 #### EMR 2405: MARINE ENGINE I **DATE:** 31/10/2023 **TIME:** 1 HOUR - Define the following terminologies giving their abbreviations as used in marine engines - Fuel Air Ratio - Homogenous Charged Compression Ignition Engine - Engine Management System - Compression Ignition Engine. - List six ideal properties of an antifreeze solution used in internal combustion engines. - The department of Marine Engineering intents to procure a stand by generator to be operated within the University with the following specifications: - Brake power = 10.5 kW, - Speed = 1900 rpm, - Indicated mean effective pressure = 0.65 N/mm2 and - Mechanical efficiency of 85%. Determine: - The cylinder dimensions, given the stoke length is 1.25 time the bore. - The wall thickness of the cylinder if the hoop stress is 45 MPa. - The size of the stud when the permissible stress for the stud is 65 MPa. ## JOMO KENYATTA UNIVERSITY ### OF ### AGRICULTURE AND TECHNOLOGY #### CAT 1 (20 Marks) #### EMR 2405: MARINE ENGINE I **DATE:** 20/02/2024 **TIME:** 1 HOUR **INSTRUCTIONS:** - Describe the following parts and the materials use to manufacture them as used in marine engines. - Cylinder block. - Connecting rod. - Piston. - Valves. - List at least six requirements than a lubricating of internal combustion engines needs to satisfy. - The Department of Mechanical Engineering at Dedan Kimathi University wishes to develop a Hydrogen Engine for the small lawn mowers operated within the University for cutting grass with the following specifications: - Brake power = 4.5 kW, - Speed = 2000 rpm, - Indicated mean effective pressure = 0.45 N/mm² and - Mechanical efficiency of 92%. Determine: - The cylinder dimensions, given the stoke length is 1.4 time the bore. - The wall thickness of the cylinder if the hoop stress is 42 MPa. - The size of the stud when the permissible stress for the stud is 70 MPa. ## JOMO KENYATTA UNIVERSITY ### OF ### AGRICULTURE AND TECHNOLOGY #### CAT 2 #### EMR 2405: MARINE ENGINE I #### TOTAL MARKS: 30 **DATE:** 02/04/2024 **TIME:** 1 HOUR 15 MINUTES **INSTRUCTIONS:** - Design the following components of the valve gear mechanism of one of the standby diesel engine of MV Mkopa: The following data are provided: - Bore = 120 mm; - Stroke 180 mm; - Power = 4.5kW; - Speed = 1500 rpm; - Maximum gas pressure = 3.8 N/mm². - The valve opens 22º before top dead centre and closes 1º after the bottom dead centre. - It opens and closes with constant acceleration and deceleration for each half of the lift. - The length of the rocker arm on either side of the fulcrum is 120 mm and the included angle is 160°. - The weight of the valve is 2.5 N. Determine: - Size of the valve port. - The maximum lift of the valve. - The thickness of the valve head. - Valve stem diameter. - Valve head diameter. Assume *V1 = 80 m/s, a = 45° k = 0.42 0 = 60 MPa and width of the valve seat = 0.06 dp*. - Design a cast iron piston for a two stroke marine engine compression ignition engine with the following specifications. - Cylinder bore = 125 mm, - Stroke length = 145 mm - Maximum gas pressure = 6 N/mm², - Indicated mean effective pressure = 0.56N/mm², - Mechanical efficiency = 95%, - Fuel consumption = 0.12 kg per brake power per hour, - Higher calorific value = 47500 kJ/kg and - Speed = 4000 rpm. For cast iron allowable tensile stress is 45 N/mm² for the piston head, Constant C = 0.05, *TC-TE = 220°C*, k = 46.6 w/m°C. *Pw = 0,035 N/mm²*, Allowable bending stress for cast iron ring = 90 N/mm², *рь = 0.45 N/mm²*, *på* for bronze = 25 N/mm². ## SECTION A (COMPULSORY) ### QUESTION ONE (COMPULSORY) [20 MARKS] a) With the aid of a well labelled diagram describe the operation of a SI four stroke engine. b) Describe the following engine parts as used in internal combustion engine and the materials used to manufacture them: - Engine block. - Valves. - Cross head. c) Define the following terms as used in internal combustion engines: - Stroke length. - Engine management system. - Direct injection. d) List three reason why water alone cannot be used as coolant. e) Give three reason why the amount of heat dissipated to air depends upon: - Amount of air flowing through fins. - Fin surface area. - Thermal conductivity of fins. f) List and describe four parts that makes up the water cooling system. ## SECTION B (ATTEMPT ONE QUESTION) ### QUESTION TWO [20 MARKS] a) State at least three basic requirement for a good lubrication oil. b) List two advantages and disadvantages each of air cooling system. c) Design a cast iron piston for a two stroke marine engine compression ignition engine with the following specifications: - Cylinder bore = 125 mm, - Stroke length = 145 mm, - Maximum gas pressure = 6 N/mm², - Indicated mean effective pressure = 0.56N/mm², - Mechanical efficiency = 95%, - Fuel consumption = 0.12 kg per brake power per hour, - Higher calorific value = 47500 kJ/kg and - Speed = 4000 rpm. For cast iron allowable tensile stress is 45 N/mm² for the piston head, Constant C = 0.05, *TC-TE = 220°C*, k = 46.6 w/m°C. *Pw = 0,035 N/mm²*, Allowable bending stress for cast iron ring = 90 N/mm², *рь = 0.45 N/mm²*, *på* for bronze = 25 N/mm². ### QUESTION THREE [20 MARKS] a) Define the following terminologies as use in internal combustion engine. - Top Dead Centre - Direct Injection - Wide open throttle - Compression Ignition Engine.