Agricultural and Biosystems Power Engineering PDF

1 AGRICULTURAL AND BIOSYSTEMS POWER ENGINEERING JONATHAN V. FABULA, Ph. D. Associate Professor...

1 AGRICULTURAL AND BIOSYSTEMS POWER ENGINEERING JONATHAN V. FABULA, Ph. D. Associate Professor Department of Agricultural and Biosystems Engineering College of Engineering, Central Luzon State University CLSU ABE I. INTRODUCTION ✓ Agricultural mechanization requires power and energy source. ✓ Agricultural mechanization aims to increase productivity and reduce laborious farm activities. II. TYPES OF FARMWORK 1. Tractive work – requiring pulling or drawing efforts. Ex. plowing or land preparation, planting and seeding, crop cultivation, harvesting, and hauling. REVIEW 2. Stationary work – usually accomplished by means of belt, gears, pto, direct drive, electric motors. Ex. Water pumping, threshing, milling III. SOURCES OF FARM POWER 1. Human Power A mature human can develop 0.10 hp continuously when in good physical condition, well- fed and working in a favorable environment. A human is a poor source of mechanical power but most suited in farm operations that required judgment and skill. CLASS 2. Animal Power Since the horse is the chief source of power during the early times, then it became the ready reference when computing for power. The horse working continuously for several hours and walking at 2.5 mph should not pull more than 1/10 to 1/8 of its body weight. To determine the power performance of an steam engine, James Watt (Scotland) conducted a series of tests with an average horses and found that a horse could left 366 lb of coal out if a mine at a rate of 1 ft/s (22,000 ft-lb/min). He then increased this value arbitrarily by 50% to underate the engines deliberately. The resulting value is 33,000 ft- lb/min or 550 ft-lb/s which is approximately equivalent to 0.746 kW. 2023 Power range of farm animals = 0.7 to 1.3 hp Power = force * speed Application: for tractive works mentioned earlier. The population of work animals is declining. Reasons for use of domestic animals: a. Small farm sizes b. Rolling topography c. Crops not suited for mechanization DO NOT REPRODUCE d. Lack of suitable fuel at reasonable cost e. High initial cost of mechanical equipment f. Plentiful supply of low cost labor 3. Wind Power Wind was another early source of power to increase the productive capacity of the human muscle. It has been utilized to propel ships in the seas and served a variety of purpose like water pumping, milling and in electricity generation. Wind power is less limited for farm use, cannot be controlled, and seldom available when needed. CLSU ABELE Review Class 2023 Agricultural and Biosystems Power Engineering  2 The theoretical power from wind can be calculated using the formula; 𝛒 𝐀 𝐕𝟑 𝑻𝒉𝒆𝒐𝒓𝒆𝒕𝒊𝒄𝒂𝒍 𝒑𝒐𝒘𝒆𝒓 = 𝟐 where: ρ – air density, 1.25 kg/m3 A – rotor area, m2 CLSU ABE V – wind speed, m/s Classification of windmills: a. According to shaft orientation – vertical or horizontal. b. According to blade material – sail, metal, wooden. c. According to shaft speed – high speed (2 to 4 blades); < 300 rpm or low speed (multi-bladed and high torque for water pumping) 4. Water Power The movement of water masses is a form of kinetic energy which can be converted into REVIEW mechanical energy by utilizing water wheels or water turbines. There are two types of water masses movement that can be used; a. The falling/flowing streams of water through the force of gravity, and b. The rise and fall of tides through lunar (and solar) gravity. In hp, the theoretical power available from flowing water can be calculated using the equation; QH 𝑇ℎ𝑒𝑜𝑟𝑒𝑟𝑡𝑖𝑐𝑎𝑙 𝑃𝑜𝑤𝑒𝑟 = 33,000 CLASS where: H – head, ft Q – mass flow rate, lb/min The mass flow rate (Q) can be expressed as: 𝑄 =VAρ where: V – velocity of flowing water, ft/min A – cross sectional area of water stream, ft2 2023 ρ – density of water, 62.4 lb/ft3 In kW, the theoretical power available is: QH 𝑇ℎ𝑒𝑜𝑟𝑒𝑟𝑡𝑖𝑐𝑎𝑙 𝑃𝑜𝑤𝑒𝑟 = 102 where: H – head, m Q – mass flow rate, kg/sec The mass flow rate (Q) can be expressed as: DO NOT REPRODUCE 𝑄 =VAρ where: V – velocity of flowing water, m/sec A – cross sectional area of water stream, m2 Ρ – density of water, 1000kg/m3 Actual power of water wheels is 60 to 80% of theoretical due to the ff: Hydraulic losses in conduit and turbines Mechanical losses in bearings and power transmission systems Electrical losses in generators, station use and transmission (hydro-electric) CLSU ABELE Review Class 2023 Agricultural and Biosystems Power Engineering  3 Types of water power generating devices: 1. Hydraulic rotating prime movers 1.1 water wheels (undershot, overshot, breast) 1.2 tub wheel or flutter wheel 1.3 turbines 2. Hydraulic rams CLSU ABE 3. Hydraulic air compressors 5. Electric Power Used extensively for supplying heat, light and power for heating water, operating brooders, water pumps, dairy and refrigeration equipment. Power (watt) = Voltage (volt)*current(amp) Limitation is due to the availability of power in the locality, or availability of 3 phase lines. Advantages of electric motor: REVIEW a. Simple and compact in construction b. Light in weight per hp c. Require limited attention, care and servicing d. Start easily and readily e. Operate quietly f. Produce smooth uniform power g. Adapted to uniform and variable loads 6. Solar Energy Solar energy has been in use throughout the world mainly for drying and heating. New dimensions of solar energy applications have been developed like electricity generation, CLASS space cooling, refrigeration and water pumping. However, due to high investment costs, the commercial use of these modern technologies has yet been limited. The energy received from the sun per unit of time on a normal surface at the average distance between the sun and the earth outside of the earth’s atmosphere is equal to 1,353 w/m2. The radiation absorbed by the earth is about 690 w/m2. Classification of Solar Energy Applications 1. Thermal or Heat-based Applications These rely on heat energy coming from the sun. The heat energy can be used directly 2023 to heat or cool systems or be transformed to other forms of energy such as mechanical or electrical. 2. Photovoltaic Applications These rely on the illumination-spectrum intensity coming from the sun. With the aid of semi-conductor materials, e.g. solar cells, the illumination is transformed directly into electricity. a. Solar collector – a device that collect solar radiant energy and transform it to some other useful form of energy. b. Photovoltaic cell – a device used to convert solar energy directly to electricity. Most common type is single crystal silicon solar cell (16% efficiency). DO NOT REPRODUCE c. Solar constant – amount of solar energy (1353 watts/sq.m.) received per unit time on a unit area of surface perpendicular to the radiation and at outer limit of earth atmosphere when the earth is at mean distance from the sun. d. Direct radiation – the solar radiation received by the earth’s surface without having been deflected/intercepted or absorbed by the atmosphere (1000watts/sq.m.) CLSU ABELE Review Class 2023 Agricultural and Biosystems Power Engineering  4 7. Biomass Energy Biomass refers to all organic materials that originate from living organisms such as wood, agricultural residues, animal wastes and others. Large proportion if biomass, mainly fuelwood, is being used in developing countries. Sources of biomass: ✓ livestock manure CLSU ABE ✓ crop residues ✓ fuel wood ✓ sugar crops ✓ household and urban refuse ✓ rural and municipal sewage ✓ aquatic plants ✓ energy farming (fast growing trees, oil and hydrocarbon crops. Biomass conversion processes a. Thermochemical conversion - (gasification, pyrolysis and carbonization, REVIEW combustion) b. Biochemical conversion - (ethanol production, biogas production) 8. Heat Engines Engine is a device that transforms the chemical energy inside a combustible fuel into mechanical energy that can be used to do work. Types of Heat Engines a. External Combustion Engines (ECE) – Work by using an external heat source (like CLASS burning coal) to heat a working fluid (like water). As the temperature of the fluid increases, the fluid expands, and this expansion is harnessed and used to do work (like moving a vehicle). Single Phase (Stirling Engine) Stirling engines are similar to steam engines except they use a working fluid that does not change phases. It is always in the gaseous form. Dual Phase (Steam Engine) Uses water as the working fluid and takes advantage of the phase change that turns warm water into steam. Steam engines have most often used coal or wood as their 2023 combustible fuel, although in the modern-day they have also been used to run coal and nuclear power plants. Advantages of ECE ✓ These engines have the capability to use all types of fuels. ✓ The external combustion engines generate very low noise. ✓ They have a low emission rate. ✓ They are best suitable for high-power generation applications. Disadvantages of ECE ✓ They are not ideal for low power generation applications. DO NOT REPRODUCE ✓ They have working fluid leakage issues. ✓ The EC engine has more size than the IC engine. ✓ They consume more lubricate than the IC engines. ✓ These engines have a high operational temperature b. Internal Combustion Engine (ICE) The ignition and combustion of the fuel occurs within the engine itself. The engine then partially converts the energy from the combustion to work. Ultimately, through a system of gears in the powertrain, this motion drives the vehicle’s wheels. Based upon the action of an ordinary rifle or cannon. The barrel served as the cylinder and the bullet or cannon ball served as the piston. CLSU ABELE Review Class 2023 Agricultural and Biosystems Power Engineering  5 History and Development of Internal Combustion Engine Beau de Rochas (1862, French Engineer) – Theory in the operation of ICE essential for efficient operation: a. the greatest possible cylinder volume with the least cooling surface CLSU ABE b. the greatest possible piston speed. c. highest possible compression at the beginning of expansion. d. the greatest possible expansion. The engine must consist of a single cylinder and piston that makes a stroke for each of the four distinct events constituting a cycle as follows: 1. Drawing of the combustible mixture on an outward stroke – intake stroke. 2. Compression of mixture on an inward stroke – compression stroke. 3. Ignition of mixture at maximum compression producing an outward - power stroke. REVIEW 4. Discharge of product of combustion on an inward stroke – exhaust stroke N. Otto (1876, German) - patented the first ICE operating on 4SC principle. D. Clerk (1878, French) – patented the 2 SCE and perfected in 1881. R. Diesel (1892, German) – patented an engine utilizing the heat of compression for ignition and perfected in 1898. IV. POWER AND ITS MEASUREMENT Fundamental Physics Term CLASS Mass – a quantity of matter a body contains irrespective of the kind of material of which it is composed (g, Kg, or lb) Inertia – property of matter by virtue of which a body tends to remain at rest or continue in motion in a straight line. Momentum -a term applied to a body in motion, it is the product of its mass and velocity at any instant. Force – is an action, exerted upon a body, that changes or tends to change its natural 2023 state of rest or uniform motion in a straight line. Work – if a force is applied to a body changing its state of motion or if it is in motion, its rate or direction of travel is changed – then work is done. (kg-m, ft-lb) Energy – the energy possessed by a body is defined by its capacity for doing work. Potential energy – energy possessed by virtue of its position. (kg-m, ft-lb) Kinetic energy – energy possessed by virtue of its motion. DO NOT REPRODUCE Kinetic Energy = WV2/2g where: W – weight of body V – velocity g – acceleration of a free falling body Torque – a turning or twisting effort or action. Power -rate at which work is done (ft-lb/min, kg-m/min) CLSU ABELE Review Class 2023 Agricultural and Biosystems Power Engineering  6 Horsepower - a unit of measurement of power (English) equal to doing work at the rate of 33,000 ft-lb/min or 550 ft-lb/sec Mechanical and Electrical Power Units CLSU ABE Electrical work (joules) Amount of work done by a current of 1 ampere flowing for 1 second under a pressure of 1 volt. joules = 1 volt x 1amp x 1 sec Electric Power (Watt) Electrical work (joules) per unit time (sec) Electric power, Watts = joules/sec REVIEW = amp x volt x sec/sec = amp x volt It has been found that if mechanical work is done at the rate of 1 ft-lb/sec, then 1.356 W of electric power will be required to do the same; 1 ft-lb/sec = 1.356W; if 1hp = 550 ft-lb/sec 1 hp = 550 x 1.356W CLASS 1 hp = 746 W 1 kW = 1.35 hp Engine Horsepower Indicated Hp (ihp) – the power generated in the cylinder and received by the piston. Power (indicated hp) = PLANn/ (33,000 x2) – 4 SCE Power (indicated hp) = PLANn/(33,000) – 2SCE 2023 where: P – mean effective pressure, psi L – length of piston stroke, ft A – area of cylinder, sq. in. N – rpm n – number of cylinders Power (indicated hp) = (P*L*A*N*n)/ 76*60 where: P – indicated mep, kg/sq.cm. L – piston stroke, m DO NOT REPRODUCE A – piston area, sq.cm. N – number of power strokes per minute n – number of cylinders Belt or Brake hp – power generated in the belt pulley (measured by a suitable dynamometer) and available for useful work. Hp = (force on scale due to friction only (lb) x 2π r(ft)x rpm)/33000 hp = (net load (lb) x lba (ft) x 2π rpm)/33000 CLSU ABELE Review Class 2023 Agricultural and Biosystems Power Engineering  7 Friction Hp (fhp) – power the engine consumes in operating itself at a given speed without any load. ihp – bhp = fhp Drawbar hp – power developed at the hitch or drawbar and available for pulling, dragging or similar tractive efforts CLSU ABE hp = (average pull (lb) x rate of travel (ft/min))/33,000 PTO hp – power developed at the PTO shaft of the tractor and available for driving rotovators and other implement. Hydraulic hp – the fluid power required by the implement from the hydraulic system of the tractor. Power (hydraulic) = (Q * P)/1714 where: Q – hydraulic flow, gpm REVIEW P – oil pressure, psi Volumetric Efficiency – refers to the relationship of the quantity of fuel mixture actually drawn into the cylinder by the piston on the intake stroke and producing power to the actual volume of space displaced by the piston on this stroke (range 75 to 85%). Factors affecting volumetric efficiency: 1) Atmospheric pressure and temperature 2) Manifold design (length, size, smoothness) 3) Intake manifold temperature 4) Air filter design and operation CLASS 5) Fuel characteristics 6) Piston speed 7) Compression ratio 8) Valve size, opening and timing 9) Engine operating temperature Methods to increase volumetric efficiency 1) The use of supercharger 2) Use of multi-barrel carburetors Thermal Efficiency – ratio of output in the form of useful mechanical power to the power 2023 value of the fuel consumed. TE, % = (BHP/power value of fuel)* 100 output (1hp = 42.42BTU/min = 2545 BTU/hr) input (gasoline = 20,000BTU/lb) (diesel = 19,000BTU/lb) Mechanical Efficiency – ratio of the useful mechanical power to the total power generated by the engine (range 75 to 90%) DO NOT REPRODUCE ME, % = (BHP/iHP)/100 where: BHP – brake hp iHP – indicated hp Factors affecting fuel consumption and efficiency: 1. Normal operating compression pressure 2. Operating load: light, medium, heavy 3. Mechanical condition: CLSU ABELE Review Class 2023 Agricultural and Biosystems Power Engineering  8 a. ignition correctly timed b. valves correctly timed c. fuel mixture properly adjusted d. piston rings and cylinder not badly worn e. bearing properly adjusted f. properly lubricated CLSU ABE V. ENGINE CYCLES AND PRINCIPLE OF OPERATION Engine Mechanical device that converts heat and other forms of energy such as wind, flowing water, and electricity into useable power. This device must carry the conversion process in a continuous, efficient and reliable manner consistent with the specific operation involved. Cycle Consists of the events taking place in each cylinder of an engine between two successive explosions in that cylinder. REVIEW ✓ Taking in of combustible mixture ✓ Compression of this mixture ✓ Ignition of the compressed mixture ✓ Expansion of the burned gases producing the power ✓ Exhaust of the products of combustion Reciprocating Engine Two-Stroke Cycle Engine -Two strokes of the piston or one revolution of the crankshaft is required to complete a cycle. CLASS Operation of Two-Stroke Cycle Engine ✓ The crankcase is closed and must be airtight as possible ✓ Ports of opening at the side of the cylinder are opened and closed by the piston sliding over them, takes the place of valves; ✓ No valve-operating mechanism of any kind is necessary; ✓ The fuel mixture usually enters and passes through the crankcase on its way to the cylinder. 2023 Advantages of a Two-Stroke Cycle Engine ✓ lighter in weight per horsepower ✓ simple in construction ✓ greater frequency of working strokes or power impulses Disadvantages of a Two-Stroke Cycle Engine ✓ Fuel mixture is controlled with difficulty ✓ Inefficient in fuel consumption ✓ Do not operate satisfactorily under fluctuating loads DO NOT REPRODUCE Four-Stroke Cycle Engine - Four strokes of the piston or two complete revolution of the crankshaft is required to complete a cycle (intake, compression, power, and exhaust strokes) Operation of Four-Stroke Cycle Engine ✓ One power impulse in two revolutions. ✓ This explains why heavy flywheels are necessary on one-cylinder engines. ✓ Were it not for these flywheels, such engine when under load would have the tendency to lose speed between explosions. CLSU ABELE Review Class 2023 Agricultural and Biosystems Power Engineering  9 ✓ These flywheels, owing to its inertia, maintain the uniformity of speed. One cylinder two stroke engine will require lighter flywheel, because it fires twice as frequently. Advantages of a Four-Stroke Cycle Engine ✓ More torque ✓ More fuel efficient CLSU ABE ✓ More durable ✓ Less pollution ✓ No extra addition of oil Disadvantages of a Four-Stroke Cycle Engine ✓ Complicated design ✓ Less powerful ✓ Expensive FIRING ORDER REVIEW The order or sequence in which the engine cylinders fire or generate & deliver power Three cylinder engines (1-3-2) Four cylinder engines (1-2-4-3; 1-3-4-2) Six cylinder engines (1-5-3-6-2-4; 1-4-2-6-3-5; 1-3-2-6-4-5; 1-2-4-6-5-3) FIRING INTERVAL The arc of travel of the crankshaft between successive explosions in an engine Firing interval = 360/no. of cylinders – for 2sce CLASS Firing interval = 720/no. of cylinders – for 4sce VI. TRACTORS A self-propelled machine that can be used for supplying power for (1) pulling mobile machines and (2) operating the mechanism of either stationary or mobile machines by means of belt pulley or PTO. Tractors are engineering vehicles specifically designed to deliver high tractive effort (torque) 2023 at low speeds that it can haul a trailer or similar implements used in agriculture. Types of tractors: (according to method of securing traction or self-propulsion) a. crawler or track type b. wheel type b.1. two wheel – power tiller, handtractor b.2. four wheel – 2WD (4x2),4WD(4x4) Standard class tractor – with more than 32hp engine. Compact class tractor – with 32 hp or less engine. DO NOT REPRODUCE Types of tractors according to utility: a. General purpose or utility tractor b. All purpose or row-crop type c. Orchard tractors d. Garden tractors e. Industrial tractors CLSU ABELE Review Class 2023 Agricultural and Biosystems Power Engineering  10 Component parts of the tractor power transmission system: a. Clutch – transmits power from the flywheel, absorbs impact load, for gradual application of load to engine, permits the change in gear without stopping the engine. b. Gear box – supply different speed and direction of travel, supply the needed torque for different work applications. CLSU ABE Component parts of the tractor power transmission system: a. Differential – supply different speeds for ground wheels when turning. It also function as second speed reduction point in the power train (final drive). b. Brake system – used to reduce the speed or stop the tractor. ROLL-OVER PROTECTIVE STRUCTURE (ROPS) Cab or frame installed on agricultural tractors to protect the operator from accidental overturning during operations REVIEW Three-point linkage Combination of one upper link and two lower links, each articulated to the four-wheel tractor and the implement at opposite ends, that connects the implement to the tractor TRACTOR DRAWBAR Rigid bar at the rear of the four-wheel tractor to which trailed implements and equipment are hitched Fixed Drawbar CLASS Swinging Drawbar Link Drawbar POWER TAKE-OFF SHAFT External shaft usually located at the rear of the four-wheel tractor that provides rotational power to implements and machines VII. FUELS AND COMBUSTION Essential Characteristics of Fuels 2023 1. They must have a reasonably high energy value. 2. They must vaporize at least partially at comparatively at low temperatures. 3. The fuel vapors must ignite and burn readily when mixed in proper proportions with oxygen. 4. Such fuels and their combustion products should not be unduly harmful or dangerous to human health or life. 5. They must be of such nature that they can be handled and transported with comparative ease and safety. Classification and composition of fuel DO NOT REPRODUCE Gaseous or liquid fuels – according to physical state before going into the cylinder. Natural gas (methane – CH4) / producer gas Propane or butane or lpg Artificial or natural – according to whether the fuel is obtained from natural sources or as a manufactured product. CLSU ABELE Review Class 2023 Agricultural and Biosystems Power Engineering  11 Liquid fuels: diesel (1D, 2D, 4D) alcohol (ethanol, methanol) gasoline (regular, premium, unleaded, super unleaded) Two important qualities of diesel fuel (1D and 2D) Freedom from solid matter, sediment and moisture; CLSU ABE Viscosity Cetane rating of diesel fuels – is the designated ignition quality as determined by comparing it with a standard reference fuel consisting of a given blend of cetane and alpha-methylnaphthalene. A 40 cetane fuel is one having ignition qualities as a blend containing 40 percent cetane and 60 percent alpha-methylnapthalene Heating value of fuels – is the amount of heat energy contained in any fuel (BTU). REVIEW Alcohol sources: Ethanol (C2H6O) – from (1) grain crops such as corn, wheat, sorghum (2) sugar crops such as sugarcane, sugar beets, sweet sorghum (3) starches such potatoes (4) crop residual such as corn stalks. This is known as grain alcohol. Methanol (CH4O) – can produced from coal, natural gas, petroleum or wood. It is commonly known as wood alcohol. (Denatured alcohol is a mixture of ethanol with little methanol and pyridine which gives its CLASS distinct color and odor.) Disadvantage of alcohol as engine fuel: 1. it has only 67.5% of the heating value of gasoline. 2. it does not vaporize as readily as gasoline. 3. the cost of manufacture and production is relatively high for anhydrous alcohol. Advantage of adding alcohol to gasoline: 1. It raises the octane rating of the fuel. 2. It forms no soot or odor in the engine. 3. Burns without producing smoke or disagreeable odor. 2023 4. The exhaust is free of nitrogen oxides without special clean up devices because alcohol burns cooler. 5. Cool burning reduces the possibility of burning valves. 6. A higher compression ratio can be utilized thereby increasing engine efficiency. Fuel Quality Volatility - It is the vaporizing ability of a fuel at a given temperature. It indicates the operating characteristics of the fuel inside the engine. Calorific Value - The heat liberated by combustion of a fuel is known as calorific value or DO NOT REPRODUCE heat value of the fuel. It is expressed in kcal/kg of the fuel. Petrol – 11,100 (highest) Power kerosene – 10,850 High speed diesel oil (HSD oil)- 10,550 Light diesel oil (LDO oil) – 10,300 Ignition Quality - refers to ease of burning the oil in the combustion chamber. Octane number and cetane number are the measures of ignition quality of the fuel. CLSU ABELE Review Class 2023 Agricultural and Biosystems Power Engineering  12 PRE-IGNITION - occurs when the fuel charge is fired too far ahead of the compression TDC of the piston. Owing too excessive spark advance or to premature spontaneous ignition resulting from excessive heat in the cylinder. DETONATION - occurs in the process of combustion of the mixture within the cylinder after ignition takes place in high compression engine CLSU ABE Methods to control detonation: 1. Using especially designed cylinder heads and pistons to so shape the combustion space that the last to burn portion of the charge will be spread out into a thin sheet and its temperature held down more effectively. 2. Providing more effective water circulation and cooling around the cylinder head and exhaust valve. 3. Using cylinder head and piston materials such as aluminum alloys that provide more heat dissipation. 4. Using properly designed spark plugs and locating it on the “hot region” preferably near the exhaust valve. REVIEW 5. Eliminating or reducing carbon deposits. 6. Maintaining the correct mixture of fuel and air and the proper spark setting and valve adjustment. 7. Using especially treated or so called “doped” or antiknock fuels (tetraethyllead or ethylene dibromide) Antiknock (Octane Rating) – it is the antiknock value of fuel determined by comparing it with a mixture of isooctane (C8H18) and heptane (C7H16). The rating is based on the percentage by volume of isooctane in an isooctane-heptane mixture. Isooctane – 100 (excellent antiknock quality) CLASS Heptane – 0 ( excessive knocking quality) Vapor Lock/gas lock/ air lock - is the partial or complete interruption of the fuel flow in the fuel feed system as a result of vaporization of the fuel and the formation of vapor or gas bubbles at some point. Combustion is applied to the process by which a fuel unites chemically with oxygen, producing of what is known as oxide and often generating heat of considerable intensity and sometimes light. It may be very slow or very rapid action. 2023 Rich mixture – is a fuel mixture containing less than the required amount of air. Indications of rich mixture 1. black smoke at the exhaust 2. lack of power and 3. over heating of the engine. Lean mixture – is a fuel mixture containing more than the required amount of air (slow burning). Indication of lean mixture DO NOT REPRODUCE 1. uneven firing 2. lack of power 3. overheating VIII. VALVES AND VALVE OPERATION VALVE CONSTRUCTION Gas engine valves are of poppet or mushroom type. The valve itself consist of a flat head with a beveled edge called the face, and the stem. CLSU ABELE Review Class 2023 Agricultural and Biosystems Power Engineering  13 A strong spring held in place by a retainer and key or wedge, holds the valve face tightly against the seat. The usual face and seat angle is 45 degrees. However, a 30-deg angle is frequently used for intake valves The four-cycle engines have inlet and exhaust ports at each combustion chamber at the upper section of the cylinder. The inlet and exhaust ports are equipped with inlet valves and exhaust valves. CLSU ABE VALVE MECHANISM INTAKE/EXHAUST VALVE Allows the fuel mixture to enter/exit the combustion chamber on the intake/exhaust stroke. Intake valves are larger in diameter than exhaust valves. TIMING GEAR Drives the camshaft that opens and closes the valves. REVIEW CAMSHAFT Driven by the camshaft gear. Held by the camshaft bearings so that it can smoothly rotate between the camshaft journals and bearings On the cam surface, tappets are mounted which move vertically. The rotating movement of the camshaft is converted into vertical movement to open and close the valves. TAPPET CLASS Used to convert camshaft rotation into reciprocating movement. The overhead valve type tappet is cylindrical or cup-shaped, and includes a push rod which connects the cam to the rocker arm PUSH ROD Push rods are simply hollow steel pipes machined at both ends The bottom contacts the tappet interior, and the top contacts the rocker arm ROCKER ARM One end is pushed up by the push rod which is moved by cam rotation. The other end directly contacts the end of the valve stem, and functions as a lever 2023 to push the valve up. The rocker arm shaft is mounted on the cylinder head, using brackets bearings. The push rod movement is transmitted to the rocker arm via an adjustment screw for valve clearance VALVE SPRING Keep the valve pressed firmly on the valve seat to maintain air-tightness when the valve is closed. Quickly return the valve to its original position after it has been pushed down by the rocker arm DO NOT REPRODUCE VALVE TIMING The timing of any valve is specified with respect to the instant it begins to open and the instant it closes in relation to the crankshaft rotation and the piston position. If a valve starts to open and then closes at the specified time with respect to the crankshaft and the piston position for that cylinder, it is said to be correctly timed. It would be assumed, ordinarily that a valve would start to open at the beginning of its stroke and be completely closed at the end. Most engines operate efficiently only when the valves open and close at certain points in the cycle and remain open a certain length of time. CLSU ABELE Review Class 2023 Agricultural and Biosystems Power Engineering  14 IX. FUEL SUPPLY AND CARBURETION FUNCTIONS OF FUEL SUPPLY SYSTEM Store sufficient amount of fuel. Filter the fuel and the air Deliver fuel to the engine Prevent fuel to vaporize CLSU ABE Prevents fuel to escape to the atmosphere FUEL SUPPLY SYSTEM FUEL TANK ASSEMBLY Made from pressed steel and coated inside to prevent corrosion, or a synthetic rubber compound or flame resistant plastic. Fuel gauge sender unit and electrically driven fuel pump are usually located inside the fuel tank. FUEL PUMP REVIEW This supplies fuel under high pressure to the fuel injection system, or under low pressure to a carburetor. FUEL PIPES/LINES Made from steel or Plastic. Secured by clips at several points along the underside of the vehicle. FUEL FILTER CLASS Prevent dirt and fluff entering the fuel pump. Fuel filter is fitted on the suction side of the pump. Fuel filter is fitted on the suction side of the pump. Fuel filter should be changed according to manufacturer recommendation CARBURETOR Atomizes the fuel and mixes it with the correct amount of air. FUNCTIONS OF CARBURETOR Assist in properly vaporizing the fuel. 2023 Mix the vaporized fuel in the correct proportions with air Supply the correct air-fuel mixture to the engine PROPER OPERATION OF CARBURETOR A constant and specific fuel level must be maintained in the nozzle. There must be at least partial if not complete vaporization of the liquid fuel The correct mixture of vaporized fuel and air must be maintained at all time Fuel supply system terminologies: 1. Air fuel ratio - the proportion of air and fuel mixture maintained by the fuel supply system for maximum power and economy. (15:1) DO NOT REPRODUCE 2. Catalytic converter - a device added to the exhaust system to reduce hydrocarbon and carbon monoxide pollutants in the exhaust gas. 3. Turbocharger/supercharger - a device that forces more air or fuel mixture into the cylinder than would be drawn under normal condition, thus increasing the volumetric efficiency and power output of the engine. 4. Euro emission standard – seek to limit the vehicle’s toxic gas in hope to attain a cleaner, breathable air. 5. Euro 1 was introduced in 1992 as an initiative by the EU. 6. Euro 6 was the latest and was introduced in 2014. CLSU ABELE Review Class 2023 Agricultural and Biosystems Power Engineering  15 7. DENR pushed for the implementation of Euro4 in July 2015. Oil and car manufacturers preferred to follow DOE timeline – Jan 2016 8. Euro 4 emission standard for gasoline; CO – 1.0g/km, THC – 0.10g/km, NOx – 0.08g/km. For diesel; CO – 0.50g/km, HC+NOx -0.30g/km, NOx – 0.25g/km, PM – 0.025g/km (CO – Carbon Monoxide, HC – Hydrocarbon, THC – Total Hydrocarbon, Nox- Nitrogen Oxide, PM – Particle matter) CLSU ABE 9. Euro 2 emission standard for gasoline; CO – 2.2g/km, HC+NOx – 0.5g/km. for diesel; CO – 1.0g/km, HC+NOx – 0.7g/km, PM – 0.08g/km 10. Catalytic converter – are used in exhaust systems to provide a site for the oxidation and reduction of toxic by-products (CO, NOx and HC) into less hazardous substance such as carbon dioxide, water vapor and nitrogen gas using redox reaction (redox reaction – oxidation reaction and reduction reaction occurring simultaneously). X. COOLING AND COOLING SYSTEM Bad effect of high temperature in engine REVIEW 1. Cylinder and piston may expand to such an extent that the piston would seize in the cylinder and stop the engine. 2. Lubricating quality of the oil inside the cylinder would be destroyed due to high temperature and there may not be sucking of air in the cylinder. 3. Pre-ignition of fuel mixture would take place and would cause engine knocking as well as loss of power. Purpose of cooling 1. To maintain optimum temperature of engine for efficient operation under all conditions. CLASS 2. To dissipate surplus heat for protection of engine components like cylinder, cylinder head, piston, piston rings and valves. 3. To maintain the lubricating property of the oil inside the engine cylinder for normal functioning of the engine. Methods of cooling 1. Air Cooling Air cooled engines are those engines, in which heat is conducted from the working components of the engine to the atmosphere directly. Applicable to engines with 2023 small bore and stroke and cylinders are individually cast Principle of air cooling The cylinder of an air-cooled engine has fins to increase the area of contact of air for speedy cooling. The cylinder is normally enclosed in a sheet metal casing called Cowling The flywheel has blades projecting from its face, so that it acts like a fan drawing air through a hole in the cowling and directing it around the finned cylinder Advantages of air cooled engine 1. It is light in weight DO NOT REPRODUCE 2. It is simpler in construction 3. It is more convenient and less troublesome 4. There is no danger of freezing in cold weather Disadvantages of air cooling 1. There is uneven cooling of the engine parts. 2. Engine temperature is generally high during working period CLSU ABELE Review Class 2023 Agricultural and Biosystems Power Engineering  16 2. Liquid/Water Cooling Cooling systems using liquids, usually water, are employed for all types of engines from the simple stationary farm engine to the most complicated multiple-cylinder high speed types. Water might be termed the universal cooling liquid for tractors, as well as for trucks and automobiles CLSU ABE The liquid is circulated round the cylinders to absorb heat from the cylinder walls. In general, water is used as cooling liquid. The heated water is conducted through a radiator which helps in cooling the water. Composition of the liquid cooling system water pump, radiator, fan, fan-belt, water jacket, thermostat valve, REVIEW temperature gauge and hose pipe Advantages of liquid cooling 1. It is plentiful and readily available nearly everywhere. 2. It absorbs heat well. 3. It circulates freely at all temperatures between the freezing and boiling points. 4. It is neither dangerous, harmful, nor disagreeable to use or handle. Disadvantages of liquid cooling CLASS 1. It has a high freezing point 2. It may cause excessive corrosion of the radiator and certain metal parts of the engine. 3. It may cause troublesome deposits in the cylinder jackets. Evaporation and boiling require frequent replenishing XI. IGNITION AND ELECTRICAL SYSTEM Parts of the Ignition and Electrical system 2023 Gasoline Engines: Diesel Engines: Spark Ignition Heat of Compression uses: spark plug uses: heat produced breaker system by compressing ignition coil air at very high high tension wire pressure, CR:16 battery or higher charging unit Ignition and electrical system terminologies: 1. Primary cell – a type of cell that is when fully discharged or dead, can only be restored DO NOT REPRODUCE to its original condition by renewing the materials that had been so changed (e.g. common dry cells). 2. Secondary cell – a type of cell that can be restored to its original condition by sending an electric current through it in the direction opposite to that of discharge. 3. Lead acid battery – a type of battery commonly used on tractors. 2 volts/cell (2.2volts max’m) 4. Electrolyte – solution used on lead acid batteries. It consist of 2 parts sulfuric acid (SG = 1.835) and 5 parts distilled water (SG=1). The specific gravity equals 1.300 at 21*C. 5. Sulfation - most common type of battery trouble. It is the formation of lead sulfate (discharged battery) at the bottom of the container due to delayed charging. CLSU ABELE Review Class 2023 Agricultural and Biosystems Power Engineering  17 6. CDI – capacitor discharge ignition 7. Ignition voltage requirement – 25,000 to 40,000 volts 8. Cold plug – a type of spark plug used on high compression, high speed engines with short heat path for quick heat dissipation. 9. Condenser/capacitor – a device connected to the ignition that eliminates arcing of the breaker points. CLSU ABE 10. Distributor – a device necessary in multi cylinder ignition system to distribute the secondary voltage to each spark plug. XII. LUBRICANTS AND LUBRICATION SYSTEM Functions of Lubrication: 1. To eliminate friction and wear of moving parts and loss of power. 2. To absorb and dissipate heat. 3. To serve as piston seal. REVIEW 4. To act as cushion to deaden the noise of moving parts and absorb shock. 5. To keep the engine working parts clean and free of dirt, gum, corrosive acids, and other contaminants. Lubricating Oils and Greases Auto equipment (automobiles, trucks and tractors) require three general types of lubricants, namely; (1) relatively thin, free flowing oil for the engine, (2) a heavier high viscosity oil for the transmission gears and bearings, and CLASS (3) various types of slow and non flowing materials termed “greases” for wheel bearings, spring shackles, universal joints and the like. Sources of Lubricants: Lubricants in the past (Fossil-based) were derived from three general sources: (1) Animal – lard, tallow, sperm and fish oil. (2) Vegetables – castor oil, olive oil, linseed oil (3) Minerals – obtained by refining crude petroleum. 2023 Synthetic lubricant- is a non-naturally occurring product made by chemical reaction of two or more simpler chemical compounds which display lubricating properties. Engine Crankcase Oil DO NOT REPRODUCE During the early times the selection of correct lubricant was left with the operator, - Today, the engine manufacturer have assumed the responsibility of determining and recommending the proper grade of oil to be used which the operator must adhere closely. Essentials of a Good Lubricating Oil 1. Must possess sufficient viscosity and lubricating power- oiliness- to suit the mechanical condition and conditions of speed, pressure and temperature. 2. Must suit the lubricating system. CLSU ABELE Review Class 2023 Agricultural and Biosystems Power Engineering  18 3. Must be of such nature that it will not produce deposits during use when exposed to the influence of the air, gas, water or impurities with which the oil. Test of Lubricating Oils Viscosity – is the measure of resistance to flow. It is the internal resistance exhibited as one portion or layer of a liquid moves in relation to another. Viscosity of lubricating oil is CLSU ABE affected by temperature. An expression involving the time in seconds required for a measured volume to flow, under specified conditions, through a standard tube, is known as the viscosity of the oil. Saybolt Universal Viscosimeter is used to determine the viscosity of lubricating oils. Viscosities are quoted in terms of Saybolt Universal Seconds (SUS) SAE Viscosity Classification – oil grading system based upon viscosity numbers taken at 0 and 210oF (-17.8 to 98.9oC) Single grade oil (ex. SAE10W – winter grade oils) REVIEW (ex. SAE 40 – summer grade oils) Multi grade oil (ex. SAE 10W-30, SAE 20W-40) Engine oils viscosity range from SAE 5W to SAE 50 API Engine-Oil Service Classification- this system enabled engine oils to be defined and selected on the basis of their performance characteristics and the type of service for which they are intended. “S” – service (service stations, garages, new car dealers, spark ignition, etc) CLASS SA - for Utility Gasoline and Diesel Engine Service. SB – for Minimum Duty Gasoline Engine Service. SC – for 1964 Gasoline Engine Warranty Maintenance Service SD – for 1968 Gasoline Engine Warranty Maintenance Service SE – for 1972 Gasoline Engine Warranty Maintenance Service “C” – Commercial (fleets, contractors, farmers), compression ignition, for Diesel Engine Service 2023 CA and CB – mild to moderate duty CC – naturally aspirated, turbo-charged, or supercharged diesel engines operated in moderate to severe duty service and some heavy duty gasoline engines CD - naturally aspirated, turbo-charged, or supercharged diesel engines where highly effective control of wear and deposits is vital. Engine Oil Additives (chemicals that when added to well-refined motor oil would improve its lubricating qualities and eliminate specific troubles) 1. Oxidation inhibitor – slows down oil oxidation and protects bearings. 2. Corrosion and rust inhibitor – eliminates corrosion by forming unbroken protective DO NOT REPRODUCE film on engine parts or by completely encircling individual water and acid molecules. 3. Detergents – cleans the engine of carbon and gums 4. Dispersants – cause carbon and gum to remain in suspension in the oil. 5. Extreme –pressure agents – enable the lubricant to withstand the unusual high pressure and temperature conditions developed by hypoid gears. Prevent metal to metal contact. 6. Foam inhibitors – accelerates the breakdown of foam. 7. Pour-point depressants- lower the temperature at which oil will pour or flow. CLSU ABELE Review Class 2023 Agricultural and Biosystems Power Engineering  19 8. Viscosity-index improvers- retards the tendency of oil to thicken as temperature drops. 9. Antiscuff/Antiwear agent – used to form lubricating films strong enough to carry the load imposed to the engine. Greases CLSU ABE ❑ a semi-solid or solid combination of petroleum and a soap or a mixture of soaps, with or without fillers, suitable for certain types of lubrication. ❑ used primarily for slow moving parts where pressure are high, and for parts that are concealed or inaccessible – wheel bearings, shackles, water pumps Advantages of grease as lubricant: 1. Simplified seal design and may act as seal. 2. Shielded bearings can be prelubricated. 3. Generally, less frequent lubrication required. REVIEW Grades of Grease - nine (9) standard grades adopted by the National Lubricating Grease Institute according to firmness or hardness. No. 000 (very soft) to No.6 (very hard). Most recommended are No. 1 or No. 2 grade. Gear or Transmission Lubricants ❑ heavy- bodied oil to cushion and sustain the sudden high-pressure loads transmitted to the gear teeth surfaces and yet cling to these teeth. ❑ must not create undue resistance to motion and should not flow in ample quantity to the shaft bearings. ❑ referred as extreme-pressure (EP) lubricants and containing certain additives.SAE CLASS 80, SAE 90, SAE 140, SAE 250 ENGINE LUBRICATION SYSTEM ❑ a good lubrication system must be efficient in operation, reliable, trouble proof, and simple. Parts of the engine requiring lubrication: 1. Cylinder wall, pistons, piston rings 2. Piston pin 2023 3. Crankshaft and connecting rod bearings 4. Camshaft bearings 5. Valves and valve-operating mechanisms Classification of Engine – Lubrication System 1. Splash type 2. Pressure-feed and splash type 3. Full-pressure feed Splash system DO NOT REPRODUCE ❑ the lubrication of al the principal engine parts is dependent directly upon the splashing of the oil by a dipper on the bottom side of the connecting rod cap that dips into the crankcase oil. ❑ Some small engines use oil slinger which are driven by the camshaft. ❑ Used on small single cylinder gasoline engines Pressure-feed and splash system ❑ in this system oil is forced directly to the main crankshaft, connecting rod, and camshaft bearings CLSU ABELE Review Class 2023 Agricultural and Biosystems Power Engineering  20 ❑ drilled passages in the crankshaft carry the oil from the main bearings to the connecting- rod bearings. The oil oozing out of these bearings creates a spray that lubricates the cylinder walls, pistons and piston pins. ❑ the valve mechanism is also oiled by pressure from the crankcase. Full-pressure system CLSU ABE ❑ this system goes further and forces oil not only to the main crankshaft, connecting rod and camshaft bearings but also to the piston pin bearings. ❑ the cylinders and pistons receive their oil from the piston pins and from the mist created by the oil issuing from the various bearings. ❑ the valve mechanism likewise is oiled by pressure feed ❑ Oil circulating pumps –gear pump is used to circulate oil and build pressure (30 to 70 psi or 2.1 to 4.9 Kg/cm2) ❑ Oil pressure –relief valves – used to maintain correct pressure and control the quantity of circulated oil. ❑ Oil pressure indicators – tells the operator what the engine oil pressure is. Warns if something occurs in the system that prevents the delivery of oil to vital parts. REVIEW ❑ Crankcase ventilation – necessary because the pumping action of the piston creates uneven pressure, which might force oil upward past the pistons into the combustion chamber or out of the crankcase joints. Also, to allow air circulation. ❑ Oil filter- to remove sand, soil, metal particles, carbon, and all other undesirable foreign matter from the oil. ❑ Oil-level indicator – shows the level of oil in the crankcase sump (oil pan) and indicates whether it is one quart low or full (bayonet type or dip stick) Conditions for effective lubrication: 1. Periodic and regular changing of the oil. CLASS 2. Careful observation and regulation of the oil-reservoir supply and the quantity distributed or fed to the parts requiring lubrication. 3. Regular servicing of the oil filter. 4. Prevention of pollution of oil such as dust, dirt, water, liquid fuel, and carbon. XIII. REFERENCES Basavaraj, D. Srigiri & Jayan P.R. 2019. A Textbook of Farm Machinery and Power Engineering. NIPA. India. 2023 Heywood, J. B. 2018. Internal Combustion Engine Fundamentals, Second Edition. McGraw-Hill Education. Jones, F. P. 1963. Farm Gas Engines and Tractors. Jones, F. R. and Aldred, W.H. 1980. Farm Power and Tractors.5th Edition. McGraw-Hill Book Company. Kepner, R.A, Bainer, R. and Barger, E.L. 1978. Principles of Farm Machinery. 3rd Edition. Avi Publishing Company, Inc. Westport Connecticut. USA Liljedahl, J. B., Carleton, W. M., Turnquist, P. K. and Smith, D. M. 1979. Tractors and Their Power Units. Srivastava, A.K., Goering, C.E., Rohrbach, R.P. and Buckmaster, D.R. 2006. Engineering Principles of Agricultural Machines. 2nd Ed. American Society of Agricultural and Biological Engineers. DO NOT REPRODUCE CLSU ABELE Review Class 2023 Agricultural and Biosystems Power Engineering  21 AGRICULTURAL AND BIOSYSTEMS POWER ENGINEERING QUESTIONS 1. The first idea concerning the operation and construction of internal combustion engine were based upon the action of a. Rifle or canon b. Sling Shot c. Water Gun d. steam engine 2. It joins the connecting rod and the piston a. Piston ring b. Piston pin c. Cylinder d. Camshaft CLSU ABE 3. A series of events occurring one after the other in a definite order and repeated once the last event has occurred a. Cycle b. Events c. Intake d. Power 4. It transmits power from piston to crankshaft a. Piston ring b. Piston pin c. Cylinder d. Connecting rod 5. The total horsepower developed by the engine disregarding all losses. a. Indicated HP b. Brake HP c. Friction HP d. Drawbar HP 6. Power developed at the hitch that can be used for pulling or dragging. a. Indicated hp b. Rated hp c. Drawbar hp d. Brake hhp 7. The rate at which work is done REVIEW a. Energy b. Force c. Inertia d. Power 8. It supports the crankshaft and serves as reservoir for lubricating the oil. a. Cylinder head b. Cylinder Block c. Crankcase d. Piston 9. The ratio of Brake horsepower to the indicated horsepower a. Mechanical Eff. b. Volumetric Eff. c. Thermal Eff. d. Engine Eff. 10. Invented the compression ignition engine. a. Rudolf Diesel b. Dugald Clerk c. Nicholas Otto d. Binotti 11. It measures the ability of the engine to convert fuel to useful work a. Mechanical Eff. b. Volumetric Eff. c. Thermal Eff. d. Engine Eff. 12. The arc of travel of the crankshaft in degrees between successive explosions in an engine a. Firing order b. Firing Interval c. Crankshaft Revolution d. Engine CLASS Combustion 13. The power generated at the belt pulley and available for useful work a. Indicated hp b. Brake hp c. Rated hp d. Friction hp 14. One hp is equal to how many foot-pound per second? a. 33,000 ft-lb/s b. 746 ft-lb/sec c. 1.356 ft-lb-sec d. 550 ft-lb/sec 15. An engine component present in a petrol engine but not in a compression ignition engine. a. Valves b. Fuel injector c. spark plug d. camshaft 16. The average fuel consumption of a gasoline engine is about a. 0.60 lb b. 0.60 lb/hp-hr c. 0.55 lb d. 0.55 lb/hp-hr 17. This is the distance travelled by the piston from the top-dead-center and bottom-dead-center 2023 or vice versa. a. Cycle b. Event c. Bore d. Stroke 18. It is a cylindrical part closed at one end which maintains a close sliding fit in the engine cylinder a. Cylinder b. Piston c. Cylinder Block d. Spark plug 19. An engine component present in a petrol engine but not in a compression ignition engine. a. Valves b. Fuel injector c. spark plug d. camshaft 20. A tractor has a three cylinder four stroke cycle engine. The cylinder bore is 88.9mm, stroke is 127mm, compression ratio is 16.5:1, belt horsepower is 32 and engine speed is 2000 rpm. What is the engine’s piston displacement? a. 787 cc b. 887 cc c. 987 cc d. 687 cc 21. What is the displacement volume of the tractor’s engine in item 20? a. 3362 cc b. 4567 cc c. 2362 cc d. 2632 cc DO NOT REPRODUCE 22. What is the engine’s piston speed in item 20? a. 508 m/min b. 430 m/min c. 644 m/min 23. What is the stroke-to-bore ratio of the engine in item 20? d. 312 m/min a. 2.34 b. 1.43 c. 1.34 d. 2.43 24. A four cylinder gas engine has a cylinder diameter of 25cm, stroke of 50cm and runs at 154 rpm. The engine is a four stroke cycle with an indicated mean effective pressure of 7.5 kg/sqcm, what is the engine’s ihp? Assumed ME is 86.4%. a. 124 hp b. 141 hp c. 151 hp d. 161 hp 25. What is the engine’s bhp in item 24? a. 131 hp b. 107 hp d. 121 hp d. 111 hp CLSU ABELE Review Class 2023 Agricultural and Biosystems Power Engineering  22 26. What is the BMEP of the engine in item 24? a. 6.47 kg/sq.cm b. 5.47 kg/sq.cm c. 4.47 kg/sq.cm d. 7.47 kg/sq.cm 27. What is the engine’s stroke to bore ratio in item 24? a. 2 b. 1.5 c. 2.3 d. 1.2 28. What engine will you recommend to operate a 220 volts direct current generator having a maximum output of 90 amperes and operating efficiency of 80%? a. 44 hp b. 33 hp c. 23 hp d. 53 hp CLSU ABE 29. A force of 750N is exerted at a velocity of 15m/s, how much power it can develop. a. 11.25 kW b. 21.25 kW c. 31.25 kW d. 41.25 kW 30. If mechanical work is done at a rate of 1 ft-lb/sec, what is its equivalent in watts? a. 43.7 b. 746 c. 0.74 d. 1.356 31. What is the IHP of a 4-stroke, 4-cylinder internal combustion engine, which has a cylinder bore of 14 cm, stroke length of 16 cm, crankshaft speed of 1100 rpm, frictional horsepower of 30, and mean effective pressure is 8 kg/cm2. a. 100 hp b. 83 hp c. 94 hp d. 78 hp 32. What is the Brake HP of the engine in Item 31? a. 64 hp b. 54 hp c. 74 hp d. 84 hp REVIEW 33. What is the engine’s mechanical efficiency in item 31? a. 58% b. 48% c. 68% d. 78% 34. The power developed at the end of the crankshaft of a 4-stroke, 4 -cylinder internal combustion engine was found to be 30 HP at a speed of 1500 RPM. The mean effective pressure is 6 kg/cm2. The stroke-bore ratio is 1.3. What is the diameter of bore if the mechanical efficiency is 80%. a. 3.8 in b. 1.7 in c. 2.6 in d. 4.5 in 35. What is the length of stroke of the engine in item 34? a. 2.2 in b. 4.9 in c. 3.4 in d. 1.5 in 36. A stream flowing at 141 ft3/s and have a vertical drop of 16 ft will be used to generate electricity in an off-grid community. The engineers decided to use a turbine with 80% CLASS efficiency and a generator that is 90% efficient. What is the theoretical power that can be generated from the stream? a. 152.1 kW b. 192.3 kW c. 202.3 kW d. 324.3 kW 37. What is the actual power in hp can be generated from the stream in item 36? a. 185.6 hp b. 175.6 hp d. 165.6 hp d. 195.6 hp 38. A wind turbine that is 80 meters tall with a blade length of 160 ft will be used to generate electricity in an off-grid farm. The average annual wind speed in the area is 50 ft/s. What is the theoretical power that it can generate? a. 13.3 MW b. 10.4 MW c. 16.4 MW d. 20.2 MW 39. What is the actual power that it can generate assuming turbine efficiency of 95%? 2023 a. 15.6 MW b. 9.3 MW c. 30.4 MW d. 22.2 MW 40. A device that transmits temperature signals to allow water flow in the cooling system a. Thermostat b. Vacuum relief valve c. Water pump d. Fan 41. A part of the carburetor that adjusts the airflow. a. Choke plate b. Throttle plate c. Bowl vent d. Fuel pump 42. Holes or openings in the engine cylinder for water circulation that aids in engine cooling a. Filter b. Venturi c. Water Jacket d. Bowl vent 43. A device that delivers the proper fuel-air mixture to the engine. a. Fuel pump b. Throttle plate c. Choke plate d. Carburetor 44. It provides a rich mixture to help start the engine at low temperatures by partially blocking the incoming air to the carburetor. DO NOT REPRODUCE a. Choke plate b. Throttle plate c. Bowl vent d. Fuel pump 45. A designated ignition quality of diesel fuel with reference to some standards. a. Octane rating b. Viscosity c. Additives d. Cetane rating 46. A device that forces more air or fuel mixture into the cylinder than under normal condition. a. Air cleaner b. Supercharger c. Throttle plate d. Choke plate 47. It supplied fuel to the fuel injection system under high pressure or to the carburetor under low pressure. a. Venturi b. Fuel lines c. Fuel Pump d. Governor system 48. It drives the camshaft to open and close the valves every cycle. a. Rocker arm b. Push rod c. Tappet d. Timing gear CLSU ABELE Review Class 2023 Agricultural and Biosystems Power Engineering  23 49. A part of the cooling system that cools the circulating water in the engine. a. Radiator b. Pressure cap c. Vacuum relief valve d. Thermostat 50. A device that prevents foreign materials from entering the fuel pump. a. Air cleaner b. Air filter c. Oil filter d. Fuel filter CLSU ABE AGRICULTURAL AND BIOSYSTEMS POWER ENGINEERING ANSWER KEY 1. A 11. D 21. C 31. C 41. B. 2. B 12. B 22. A 32. A 42. C. 3. A 13. B 23. B 33. C 43. D 4. D 14. D 24. A 34. A 44. A 5. A 15. C 25. B 35. B 45. D REVIEW 6. C 16. B 26. A 36. B 46. B 7. D 17. D 27. A 37. A 47. C 8. C 18. B 28. B 38. C 48. D 9. A 19. C 29. A 39. A 49. A 10. A 20. A 30. D 40. A 50. D CLASS 2023 DO NOT REPRODUCE CLSU ABELE Review Class 2023 Agricultural and Biosystems Power Engineering