Q. What is a heat engine ?
Ans. Any type of engine or machine which derives heat energy from the combustion of fuel or any other source and converts this energy into mechanical energy is termed as a ‘‘heat engine’’.
Read moreDescription | SI Engine | CI Engine |
---|---|---|
Basic cycle | Works on Otto cycle orconstant volume heat addition cycle. | Works on Diesel cycle or constant pressure heat addition cycle. |
Fuel Gasoline | A highly volatile fuel. | Self-ignition temperature is high. |
Diesel oil | a non-volatile fuel. | Self-ignition temperature is comparatively low. |
Introduction of fuel | A gaseous mixture of fuel-air is introduced during the suction stroke.A carburettor and an ignition system are necessary. Modern engines have gasoline injection. | Fuel is injected directly into the combustion chamber at high pressure at the end of the compression stroke. A fuel pump and injector are necessary. |
Load control | Throttle controls the quantity of fuel-air mixture to control the load. | The quantity of fuel is regulated to control the load. Air quantity is not controlled. |
Ignition | Requires an ignition system with spark plug in the combustion chamber. Primary voltage is provided by either a battery or a magneto. | Self-ignition occurs due to high temperature of air because of the high compression. Ignition system and spark plug are not necessary. |
Compression ratio | 6 to 10. Upper limit is fixed by antiknock quality of the fuel. | 16 to 20. Upper limit is limited by weight increase of the engine. |
Speed | Due to light weight and also due to homogeneous combustion, they are high speed engines. | Due to heavy weight and also due to heterogeneous combustion, they are low speed engines. |
Thermal efficiency | Because of the lower CR,the maximum value of thermal efficiency that can be obtained is lower. | Because of higher CR, the maximum value of thermal efficiency that can be obtained is higher. |
Weight | Lighter due to comparatively lower peak pressures. | Heavier due to comparatively higher peak pressures. |
Ans. Any type of engine or machine which derives heat energy from the combustion of fuel or any other source and converts this energy into mechanical energy is termed as a ‘‘heat engine’’.
Read moreAns. The cylinder contains gas under pressure and guides the piston. It is made of hard grade cast iron and is usually cast in one piece.
Read moreAns. The average speed of the piston is called “piston speed”. Piston speed = 2 LN, where L and N are the stroke length and engine speed (in r.p.m.) respectively.
Read moreAns. Adiabatic compression (of air) ; Heat addition a constant pressure ; Adiabatic expansion; Heat rejection at constant volume.
Read moreAns. Brayton cycle is a constant pressure cycle for a perfect gas. It is also called Joule cycle.An ideal gas turbine plant would perform the processes that make up a Brayton cycle.
Read moreAns. Combustion may be defined as a relatively rapid chemical combination of hydrogen and carbon in the fuel with the oxygen in the air, resulting in liberation of energy in the form of heat.
Read moreAns.Pre-ignition is the ignition of homogeneous mixture in the cylinder, before the timed ignition spark occurs, caused by the local overheating of the combustible mixture.
Read moreAns. Performance Number (PN) = klimep of test fuel klimep of iso-octane where, klimep stands for knock limited indicated mean effective pressure.
Read moreAns. Diesel knock is the sound produced by the very rapid rate of pressure rise during the early part of the uncontrolled second phase of combustion. The primary cause of an excessively high pressure rise is the prolonged delay period.
Read moreAns. The ideal air capacity corresponds to filling the displaced volume (i.e., piston swept volume) with fresh mixture at inlet conditions.
Read moreAns. The process of clearing the cylinder after the expansion stroke is called “scavenging process”. The scavenging process is the replacement of combustion products in the cylinder from the previous stroke with fresh air charge to be burned in the next cycle.
Read moreAns..The property of a fuel which describes how fuel will or will not self-ignite is called theoctane number or just octane.
Read moreAns. A carburettor is a device which atomises the fuel and mixes it with air. It is the most important part of the induction system.
Read moreAns. A Choke is simply butterfly valve located between the entrance to the carburettor and the venturi throat.
Read moreAns. ‘Ignition’ is only a pre-requisite of combustion. It does not influence the gross combustion process. It is only a small scale phenomenon taking place within a specified small zone in the combustion chamber.
Read moreAns. ‘Magneto’ is a special type of ignition system with its own electric generator to provide the necessary energy for the system. It is an efficient, reliable, self contained unit which is often preferred for aircraft engines because storage batteries are heavy and troublesome.
Read moreAns. ? It is that type of lubrication in which bearing surfaces are completely separated by a layer of film of lubricant and that the frictional resistance arises only due to relative movements of the lubricant layer
Read moreAns. A high viscosity index indicates relatively smaller changes in viscosity of the oil with the temperature.
Read moreAns.‘Engine performance’ is an indication of the degree of success with which it does its assigned job i.e., convention of chemical energy contained in the fuel into the useful mechanical work.
Read moreAns. The total power developed by combustion of fuel in the combustion chamber is called indicated power.
Read moreAns. “Rope brake dynamometer” is cheap and easily constructed but not very accurate because of changes in friction coefficient of rope with temperature.
Read moreAns. The chemically correct air-fuel ratio by mass for complete combustion is known as ‘stoichiometric ratio’.
Read moreAns. A ‘Multi-fuel engine’ is one which can operate satisfactorily (with substantially unchanged performance and efficiency) on a wide variety of fuels ranging from diesel oil, crude oil, IP-4 to lighter fuel like gasoline, and even normal lubricating oil
Read moreAns.The alternate compression at low temperature and expansion at high temperature of a working fluid is the basis for the stirling engine. — The working fluid is heated in a radically different manner. It burns fuel outside the engine itself, and continuously
Read moresafety engineering is provide to protective work culture and control of workplace accident that may cause worker injuries or disorders
Read moreThe following general types of safety are considered in the workshop.
1. Safety of self.
2. Safety of job.
3. Safety of machines tools.
Developing a solid safety plan is vital in workplaces, and recreational areas. It starts with a thorough risk assessment to identify potential hazards and assess their possible impact. Equally important is being well-prepared for emergencies, involving the creation of clear plans for different scenarios.
read moreA large number of revolving, rotating, reciprocating and moving parts of machinery can besaid as the sources of danger and require guarding for protection against accidents.
read moreThe accidents are unwanted events or mishaps that result in some sort of injury to men, material, machines, tools, equipment and semi or finished product hence, a loss to the whole establishment.
read moreFew safety measures commonly used in industries comprise of the proper safety guards for reciprocating machine components such as drop hammers, presses, shaper, slotter, power hacksaw, paper cutters etc., fencing of dangerous and rotating parts like revolving shafts,
read moreThe common methods of safety are as follows:
1.Safety by construction or design.
2.Safety by position.
3.Safety by using fixed guards.
4.Safety by using interlock guards.
5.Safety by using automatic guards.
Safety Precautions while Working with Different Cutting Tools: Like as Make files, cutting, Chisels, Saws, Reamers, Tap and Dies, Abrasives.
read moreSafety Precautions while Working with Different hand Tools: Like as Screw Drivers, Wrenches, Hammers.
read moreThey must be strictly followed for safety. Specific safety guidelines for some of the machine process like lathe, drilling, shaping, planning slotting, grinding, milling, and finishing operations.
read moreReplace Cracked Grinding Wheels: If you notice that the grinding wheel is badly cracked, replace it promptly. Damaged wheels can lead to accidents during operation.
read moreAll foundry men should wear protective clothes, glasses, shoes, and gloves while handling molten metal for casting process.
read moreA welding shop is where metal pieces are joined using heat or pressure. Safety and proper equipment are essential for efficient welding processes.
read moreFactory Act is to safeguard workers from industrial hazards and ensure a secure and improved working environment, with specific provisions outlined for the fencing of machinery and other safety measures.
read moreIn industry, an inquiry is normally ordered for electrical accident. Items carrying electricity should be properly insulated. Ageing of insulation withstand capacity and should not be allowed to leak current.
read moreThe main factors for combustions are presence of oxygen, availability of combustible materials and rise of temperature to the ignition point for the material The cause of fire accidents may be electric-short circuit.
read moreThe main factors for combustions are presence of oxygen, availability of combustible materials and rise of temperature to the ignition point for the material The cause of fire accidents may be electric-short circuit.
read moreEffects of dusts, fumes, heat, noise and vibration due to hot and cold working of metals and crush and other injuries due to machine tools are discussed earlier.
read moresometimes accidents may also occur in industries. After major or minor accidents, an injured worker requires immediate preliminary treatment in the absence of same his condition may become highly critical.
read moresA Cupola furnace is utilized for melting recycled metal or pig iron to manufacture diverse cast irons. Crucial factors in choosing cupolas include melting capability, shell diameter with or without lining, and spark arrestor.
read moreAntidotes are therapeutic agents used to counteract the toxic effects of specific xenobiotics. These are heterogenous group of substances consisting of pharmaceuticals, biological agents and immunoglobulin fragments.
read moreThis Glossary of safety to help understand basic term of safety
read moreSafety Manufacuturing PPE Automation & Mechanization Friction Lubricants Classification of manufacturing advantage and dis. LPG 5S News fire prevention ci vs si engine Gear LPG vs petrol
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