ABE 133 Lecture 2.2 Report 1 PDF

THERMODYNAMICS PRINCIPLES INTERNAL COMBUSTION ENGINE  FIRST LAW OF THERMODYNAMICS The first law of thermodynamics is based on the law of conservation of energy, which states that energy cannot be created or destroyed, but can be transferred from one form to another.  FIRST LAW OF THERMODY...

THERMODYNAMICS PRINCIPLES INTERNAL COMBUSTION ENGINE  FIRST LAW OF THERMODYNAMICS The first law of thermodynamics is based on the law of conservation of energy, which states that energy cannot be created or destroyed, but can be transferred from one form to another.  FIRST LAW OF THERMODYNAMICS The first law of thermodynamics is based on the law of conservation of energy, which states that energy cannot be created or destroyed, but can be transferred from one form to another. WH AT I S I C E ? An internal combustion engine (ICE) is a type of engine that generates power by burning fuel within a confined space or chamber. This process converts chemical energy from the fuel into mechanical energy, which can be used to power vehicles, machinery, and other equipment. HOW ENERGY IS CONSERVED IN INTERNAL COMBUSTION ENGINES? APPLICATION IN FUEL ENERGY CONVERSION TO MECHANICAL WORK.  HOW ENERGY IS CONSERVED IN INTERNAL COMBUSTION ENGINES? ENER G Y I NP U T: Fuel Combustion: Chemical energy from fuel → thermal energy (heat).  HOW ENERGY IS CONSERVED IN INTERNAL COMBUSTION ENGINES? RA NS F O RM AT I O N: ENER GY T Mechanical Work: Heat energy → kinetic energy  HOW ENERGY IS CONSERVED IN INTERNAL COMBUSTION ENGINES? WO R K D O N E : Rotational Motion: Piston movement → rotational energy  HOW ENERGY IS CONSERVED IN INTERNAL COMBUSTION ENGINES? ENE R G Y L O S S : A large portion of the initial energy is lost to heat (exhaust, cooling system), friction, and sound, but the total energy remains constant, reflecting the conservation of energy.  SECOND LAW OF THERMODYNAMICS The second Entropy is alaw of thermodynamics measure of the disorder of a stipulates that thealso system. Entropy total entropy how describes of a system much plus its environment energy cannot is not available to dodecrease; work. Theitmore can remain constant disordered for a and a system reversible higherprocess but the entropy, must always the less of a increase system's for an irreversible energy is available to do process. work. ENTROPY  In an internal combustion engine, fuel combustion releases chemical energy, which is used to generate ENTROPY mechanical work by moving the pistons. However, not all of this energy is converted into useful mechanical EFFIENCY IN ENGINES work—some is lost as heat to the engine's components and the surroundings. This loss of energy corresponds to an increase in entropy, which limits the overall efficiency of the engine.  ENTROPY EFFIENCY IN ENGINES Energy Loss: As the engine operates, heat is transferred to the surroundings, increasing the entropy of both the engine and the environment. The greater the entropy, the more energy is lost, reducing the engine's efficiency. Irreversibility: The increase in entropy during energy conversion processes makes them irreversible. Once energy is dispersed as heat, it cannot be fully recovered for work. For example, once exhaust gases leave the engine, their thermal energy is lost to the surroundings and cannot be reused. Efficiency Limitation: The more entropy that is generated during the engine’s operation, the less efficient the engine becomes. This is why improving engine efficiency involves minimizing energy losses and reducing the amount of entropy generated. For instance, technologies like turbochargers or better fuel injection systems are designed to optimize fuel use and reduce heat loss, thereby minimizing entropy.  THERMODYNAMIC CYCLES IN INTERNAL COMBUSTION ENGINES OTTO CYCLE THE OTTO CYCLE IS A THERMODYNAMIC CYCLE USED IN GASOLINE ENGINES, CONSISTING OF FOUR PROCESSES: 1. Intake: Air-fuel mixture enters the cylinder. 2. Compression: The piston compresses the mixture, increasing temperature and pressure. 3.Power (Combustion): The spark plug ignites the mixture, causing a rapid expansion that pushes the piston down. 4.Exhaust: The piston pushes out the exhaust gases. DIESEL CYCLE THE DIESEL CYCLE IS A THERMODYNAMIC CYCLE USED IN DIESEL ENGINES, CHARACTERIZED BY ITS METHOD OF COMBUSTION. IT CONSISTS OF FOUR KEY PROCESSES: 1. Intake: Air is drawn into the cylinder. 2. Compression: The piston compresses the air to a high pressure, raising its temperature significantly. 3.Power (Combustion): Diesel fuel is injected into the highly compressed air, igniting spontaneously due to the high temperature. This rapid combustion pushes the piston down. 4.Exhaust: The piston moves up to expel the exhaust gases. I. COMPARISON OF OTTO AND DIESEL CYCLES 1. PRACTICAL APPLICATIONS IN AGRICULTURAL MACHINERY. Otto Cycle engines, typically found in lighter equipment, offer smoother operation and quicker starts, making them suitable for tasks requiring agility, like tilling or small tractors. They perform well with gasoline, providing adequate power for lighter loads. I. COMPARISON OF OTTO AND DIESEL CYCLES 1. PRACTICAL APPLICATIONS IN AGRICULTURAL MACHINERY. Diesel Cycle engines, on the other hand, are favored for heavier machinery, such as large tractors and harvesters. They provide higher torque at lower RPMs, making them more efficient for heavy- duty tasks and longer operating hours. Diesel engines also offer better fuel efficiency, which is crucial for extensive agricultural operations I. COMPARISON OF OTTO AND DIESEL CYCLES 2. EFFICIENCY Otto Cycle Efficiency: Generally has a lower thermal efficiency compared to the Diesel cycle. Typical efficiency ranges from 25% to 30%. Compression Ratio: The compression ratio is lower (typically 8:1 to 12:1). Higher compression ratios can lead to knocking. Fuel Type: Uses gasoline, which has a higher volatility and ignites more easily than diesel I. COMPARISON OF OTTO AND DIESEL CYCLES 2. EFFICIENCY Diesel Cycle Efficiency: Generally more efficient than the Otto cycle, with thermal efficiency ranging from 30% to 40%, and sometimes higher. Compression Ratio: Higher compression ratios (typically 14:1 to 22:1) contribute to better efficiency. The high compression allows for more complete combustion. Fuel Type: Uses diesel fuel, which has a higher energy content and does not require a spark plug for ignition. Part 1: Specific Heat and Work in Thermodynamics  HEAT VS. TEMPERATURE TEMPERATURE hot or cold? measured in °C  HEAT a form of energy and is measured in Joules (J)  WORK refers to the energy transferred to / from the system  SPECIFIC HEAT is defined as the amount of thermal energy needed to raise the temperature of an object.  TYPES OF SPECIFIC HEAT Cp - The specific heat at constant pressure, denoted as Cp, signifies the energy necessary to increase the temperature of a material’s unit mass (1 kg) by one degree (1°C or 1 K) in an isobaric process. Cv - Constant-volume specific heat, denoted as Cv, represents the amount of energy needed to increase the temperature of a single unit mass (1 kg) of a material by one degree (1°C or 1 K) within an isochoric process.  HEAT ADDITION DURING THE COMBUSTION -This process includes the combustion of a fuel that takes place within the system. These types of engines take place where the fuel is burnt in the engine or where the fossil fuel combustion occurs.  REJECTED DURING THE EXHAUST PHASE. Rejected during the exhaust phase. -Part of the heat which is rejected is carried away in the exhaust gases, the remainder passes through the metallic walls of the engine, causing expansion and internal stress in the parts.  WORK DONE BY THE ENGINE Work Done by the Engine Work in the field of physics is defined as the energy that is transferred when a force exerts on an object with mass over a certain distance.  CALCULATION OF WORK IN A THERMODYNAMIC CYCLE. Calculation of work in a thermodynamic cycle. Calculate the work done on or by the system using the first law of thermodynamics equation: ΔU= Q−W, where work done by the system is W. If the final value for work is positive, then work is done by the system. If the final value for work is negative, then work is done on the system.  RELATIONSHIP BETWEEN WORK, HEAT, AND ENGINE EFFICIENCY. Heat engines turn heat into work. The thermal efficiency expresses the fraction of heat that becomes useful work. The thermal efficiency is represented by the symbol η, and can be calculated using the equation: Efficiency = (Output / Input) x 100%  ENGINE COMPONENTS: CYLINDER is the power unit of the engine. This is where fuel is burned and converted into mechanical energy that powers the vehicle. The number of cylinders in a typical car could be four, six or eight.  CYLINDER MATERIALS AND DESIGN CONSIDERATION Cylinder Materials- are normally made of Cast iron or Aluminum.  PISTON ·also known as “little powerhouses,” are small but mighty components that play a crucial role in many mechanical systems, from car engines to industrial pumps. ·Function-converting the energy released during the combustion.  PISTON ·Movement of piston-The four-stroke is the most common types of internal combustion engines and is used in automobiles (specifically use gasoline as fuel) like cars, tracks, and some motorbikes (many motorbikes use a two- stroke engine).  PISTON -Intake stroke: The piston moves downward to the bottom; this increases the volume to allow a fuel-air mixture to enter the chamber. -Compression stroke: The intake valve is closed, and the piston moves up the chamber to the top. This compresses the fuel-air mixture. At the end of this stroke, a spark plug provides the compressed fuel with the activation energy required to begin combustion. -Power Stroke: As the fuel reaches the end of its combustion, the heat released from combusting hydrocarbons increases the pressure which causes the gas to push down on the piston and create the power output. -Exhaust stroke: As the piston reaches the bottom, the exhaust valve opens. The remaining exhaust gas is pushed out by the piston as it moves back upwards.  ·TYPES OF PISTONS Flat – Top Pistons - This type of piston is ideal for creating efficient combustion. Commonly used in naturally aspirated engines.  ·TYPES OF PISTONS Dish Pistons - They are shaped just like a plate with the outer edges slightly curling up. Typically, dish pistons are used in boosted applications that do not require a high-lift camshaft or high compression ratio.  ·TYPES OF PISTONS Dome Pistons - Opposite in concept to the dish pistons, these bubble in the middle like the top of a stadium. This is done to increase the surface area available on the top of the piston. More surface area means less compression.  PISTONS ·Cylinder material- are commonly made of a cast aluminum alloy for excellent and light weight thermal conductivity. ·Design consideration for piston - It should have enormous strength to withstand the high pressure. It should have minimum weight to withstand the inertia forces.  CRANKSHAFT The crankshaft transforms the linear (up and down) motion of the pistons into rotational motion, which is transferred to the vehicle's drivetrain.  CONNECTING RODS The connecting rods act as a link between the pistons and the crankshaft. For durability and performance, materials used include: Cast iron - for cost effective engines. Forged steel - for stronger, high- performance applications. Billet steel - for custom, high- strength racing engines. VALVE AND VALVE TRAIN controls the operation of the intake and exhaust valves in an internal combustion engine.  INTAKE VALVES The intake valve allows the air-fuel mixture (in gasoline engines) or air (in diesel engines) to enter the combustion chamber.  EXHAUST VALVE The exhaust valve releases the burnt gases (exhaust) from the combustion chamber after the power stroke.  Types of valve (overhead, side) 1. Overhead Valve (OHV) -In an OHV engine, the valves are located in the cylinder head above the combustion chamber. The camshaft, which controls the opening and closing of the valves, is located in the engine block. 2. Overhead Cam (OHC) -In OHC engines, the camshaft(s) are located in the cylinder head, directly above the valves. 3. Side Valve - In a side valve engine, the valves are located beside the combustion chamber, usually within the engine block. The camshaft operates via pushrods and rocker arms.  Valve train Components: camshaft, rocker arm, pushrods and lifter  How the valve train controls valve operation and timing? Valve trains in internal combustion engines are crucial for controlling the operation and timing of the engine's valves. They ensure that the intake and exhaust valves open and close at the right times for optimal engine performance.  FUEL INJECTOR a device for atomizing and injecting fuel into an internal combustion engine. The injector atomizes the fuel and forces it directly into the combustion chamber at the precise point in the combustion cycle  Types of fuel injection systems Direct Fuel Injection Port Fuel Injection Throttle Fuel Injection The system is focused on Fuel is delivered to the engine Feature a single or dual injector(s) placing the injector inside the directly into the intake mounted in the throttle body, where air cylinder to directly inject the manifold or cylinder head. enters the intake manifold. fuel, bypassing the intake valve Fuel is sprayed on the valve, While less sophisticated than PFI or DFI or manifold. which then uses the heat from systems, TBI still offers improved fuel Usually seen in diesel engines the valve to atomize the fuel atomization and engine performance further. compared to carburetors.  CARBURETTOR a device which helps in mixing fuel and air together for facilitating internal combustion inside an internal combustion engine.  HOW DOES A CARBURATTOR WORKS? Step 1 From the air intake of cars, airflow comes into the top of the carburettor by passing through a filter.  HOW DOES A CARBURATTOR WORKS? Step 2 After a certain intake of air, a choke valve blocks the further intake.  HOW DOES A CARBURATTOR WORKS? Step 3 The air passes through the narrow section of venturi, the velocity increases and creates a low-pressure pocket  HOW DOES A CARBURATTOR WORKS? Step 4: As the air pressure drops, fuel comes from the fuel chambers. Step 5: The fuel consumption is regulated by the throttle valve. Step 6: Fuel and air get mixed and come into the cylinder.  HOW DOES A CARBURATTOR WORKS? Step 7: The fuel supply remains intact as the float chamber continues to supply it. Step 8: Gradually, fuel pressure drops, and the valve at the top opens.  HOW DOES A CARBURATTOR WORKS? Step 9: As the combustion mixture enters the cylinder, it sends spark ignition to the engine. Step 10: As combustion happens, the whole process starts repeating again  TUNING Idle Speed Adjustment Air-Fuel Mixture Adjustment Test and Fine-tune  TUNING Idle Speed Adjustment Air-Fuel Mixture Adjustment Test and Fine-tune  SPARK PLUG create a spark of electrical power to ignite a fuel/air mixture within the engine's cylinders DESIGN OF A SPARK PLUG TYPES OF SPARK PLUG Copper Spark Plug Core Material Copper Core Nickel Material Electrode Alloy Best for low-heat range Use applications. TYPES OF SPARK PLUG Platinum Spark Plug Core Material Copper Core Platinum Material Electrode Coated Best for engine with Use electronic ignition. TYPES OF SPARK PLUG Double Platinum Spark Plug Core Material Copper Core Platinum Coated center& Electrode Material ground electrode Best for wasted spark Use ignition system. TYPES OF SPARK PLUG Iridium Spark Plug Core Material Copper Core Iridium AlloyMaterial Electrode Electrode Best for high performance Use with electronic ignition. TYPES OF SPARK PLUG Silver Spark Plug CoreSilver Material Silver coated Electrode electrode Material Best for high performance Use vehicles and motorcycles.