I. C. Engine Test

The statement is true because the ideal air standard Otto cycle is indeed considered a closed loop cycle. In this cycle, the air-fuel mixture undergoes a series of processes including intake, compression, combustion, and exhaust, and then returns to the initial state to start the cycle again. The closed loop nature of the cycle allows for the continuous operation of the internal combustion engine, making it an efficient and reliable system.

A butterfly valve mounted at the upstream end of the intake system is known as a throttle. The throttle valve controls the flow of air or fuel mixture into the engine by adjusting the size of the opening. By restricting or allowing more air to enter the engine, the throttle valve helps regulate the engine's speed and power output. This valve is commonly used in automotive engines to control the amount of air entering the combustion chamber.

The resistance to knock in SI engines increases with the branch chain arrangement of SI fuel because it leads to a more efficient combustion process. Additionally, it increases with a decrease in the number of carbon atoms in SI fuel because shorter hydrocarbon chains have a higher resistance to knock. Furthermore, adding a methyl group to SI fuel also increases the resistance to knock as it enhances the octane rating of the fuel. Therefore, all of the above factors contribute to an increased resistance to knock in SI engines.

Increasing the suction volume of an engine allows more air to enter the combustion chamber, resulting in a higher air-to-fuel ratio. This leads to better combustion and more efficient energy conversion, ultimately increasing the air standard efficiency of the SI engine.

Vapor lock refers to the clogging of the inlet manifold channel due to rapid fuel evaporation. This can occur when the fuel gets too hot, causing it to vaporize and form bubbles in the fuel line. These bubbles disrupt the flow of fuel, leading to a loss of power and engine stalling. Vapor lock is a common issue in older vehicles or in hot weather conditions, where the fuel system may not be properly insulated or ventilated.

During the downward stroke in a two-stroke engine, all of the mentioned actions occur. Power is developed due to the high pressure gases created by the combustion process. Exhaust gases from the previous combustion cycle are expelled. Additionally, the fresh fuel-air mixture is compressed in the crankcase, ready for the next combustion cycle. Hence, all of the mentioned actions take place during the downward stroke in a two-stroke engine.

Calorific value refers to the amount of energy released when 1kg of fuel is burned completely. It is a measure of the fuel's energy content and is typically expressed in units of joules or kilojoules per kilogram. Specific heat, enthalpy, and heat capacity are all related to energy and heat transfer, but they do not specifically refer to the energy liberated by a specific amount of fuel. Therefore, the correct answer is calorific value.

CO2 has the highest specific heat with constant pressure at the same temperature compared to other monoatomic gases. This means that it requires the most amount of heat energy to raise its temperature by a certain amount. This is because CO2 is a linear molecule with three atoms, which allows it to have more degrees of freedom for energy absorption and distribution. Additionally, the presence of multiple bonds in CO2 allows for more vibrational modes, further increasing its specific heat capacity.

Gum formation occurs due to the oxidation of unsaturated hydrocarbons. Unsaturated hydrocarbons contain double or triple bonds between carbon atoms, which are susceptible to oxidation. When these bonds are oxidized, they can form sticky, gummy substances. This process is commonly observed in the degradation of oils and other organic materials, where the unsaturated hydrocarbons present undergo oxidation and result in the formation of gums.

The term OHC in engine terminology refers to "On Head camshaft." This means that the camshaft is positioned on top of the cylinder head, allowing for better control over the engine's valves. This configuration is commonly found in modern engines as it offers improved performance and efficiency compared to other camshaft placement options.

Blow by refers to the phenomenon when high-pressure gases in the combustion chamber leak past the piston into the crankcase. This can occur due to worn piston rings or cylinder walls, causing a loss of compression and decreased engine efficiency. It is a common issue in older or high-mileage engines. To prevent blow by, proper maintenance and regular inspection of the piston rings and cylinder walls are necessary.

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The weight to power ratio is less for a 2 stroke engine compared to a 4 stroke engine. This means that for the same amount of power output, the 2 stroke engine will weigh less than the 4 stroke engine. This is because the 2 stroke engine has a simpler design with fewer components, resulting in a lighter overall weight. Additionally, the 2 stroke engine has a higher power density, meaning it can produce more power in a smaller and lighter package.

When the cut off ratio is decreased in a diesel engine, it means that the combustion process is allowed to continue for a longer duration. This leads to more heat being added to the working fluid and a higher expansion ratio, which increases the work output of the engine. As a result, the air standard efficiency of the diesel engine approaches the efficiency of the Otto cycle, which is a theoretical cycle with maximum efficiency for a spark-ignition engine. Therefore, the correct answer is that the air standard efficiency of a diesel engine approaches the Otto cycle efficiency when the cut off ratio is decreased.

The knock rating of a spark ignition engine refers to its resistance to knocking or detonation. Knocking occurs when the air-fuel mixture in the engine's combustion chamber ignites prematurely or unevenly, causing a knocking sound and potentially damaging the engine. The knock rating is determined by comparing the engine's performance with reference fuels. Normal heptane and iso-octane are commonly used as reference fuels because they have well-defined knock characteristics. Normal heptane has a low knock resistance, while iso-octane has a high knock resistance. By comparing the engine's performance with these two reference fuels, the knock rating can be determined.

The spill port (valve) in the helix bypass pump connects the fuel tank and pump.

The ratio of work done by the engine to stroke volume gives the mean effective pressure. This means that the mean effective pressure is a measure of the average pressure exerted on the piston during the power stroke of an engine. It is calculated by dividing the work done by the engine by the stroke volume. The mean effective pressure is an important parameter in engine performance analysis as it provides insight into the efficiency and power output of the engine.

Gasohol is a common fuel that is made up of 90% gasoline and 10% alcohol. This blend of gasoline and alcohol is commonly used as an alternative fuel source for vehicles. The addition of alcohol to gasoline helps to reduce emissions and increase the octane rating of the fuel. Gasohol is often used as a renewable and more environmentally friendly option compared to regular gasoline.

The compensating jet in a carburettor supplies almost a constant amount of petrol at all speeds because the flow is produced due to the static head in the float chamber. This means that the fuel is constantly being supplied regardless of the suction or the diameter of the jet. The static head in the float chamber ensures a consistent flow of fuel, resulting in a constant amount of petrol being supplied at all speeds.

Sulphur is the correct answer because its presence in fuel can lower the self-ignition temperature, making it easier for the fuel to ignite. This can lead to increased knocking in an engine.

The correct order of the distillate in the ASTM distillation curve is d - c - b - a. This means that ethyl alcohol has the lowest boiling point and will evaporate first, followed by gasoline, high-speed diesel, and finally kerosene, which has the highest boiling point and will evaporate last.

The Carter carburetor has triple venturis.

Atomization refers to the process of breaking up the fuel into small droplets for better combustion. The factors that affect atomization are injection pressure, injection timing, and the diameter of the nozzle. However, the injection valve is not directly responsible for atomization. Its main function is to control the flow of fuel into the combustion chamber. Therefore, the correct answer is injection valve.

A small electrical resistance heater mounted inside the combustion chamber of many CI (Compression Ignition) engines is known as a glow plug. Unlike spark plugs, which are used in gasoline engines to ignite the air-fuel mixture, glow plugs are used in diesel engines to heat the air in the combustion chamber before the injection of fuel. This preheating helps in the combustion process, especially during cold starts, by ensuring that the diesel fuel ignites properly.

Dissociation refers to the process in which the combustion products break apart into their constituent atoms or molecules at high temperatures. This occurs due to the high energy and heat present during combustion, causing the bonds between the atoms or molecules to break. As a result, the combustion products disintegrate or dissociate into their individual components.

A cycle consisting of two constant volume and two isothermal processes is known as the Stirling cycle. In this cycle, the working fluid undergoes expansion and compression at constant volume, as well as heating and cooling at constant temperature. This cycle is used in Stirling engines, which are known for their high efficiency and ability to operate on various heat sources.

The indicator diagram is a graphical representation of the pressure (p) and crank angle (theta) in an engine cylinder. It shows the variation of pressure inside the cylinder during the four-stroke cycle of intake, compression, power, and exhaust. This diagram helps in analyzing the performance and efficiency of the engine by providing information about the combustion process and the condition of the cylinder. Therefore, the correct answer is p -theta.

In a 2 stroke 2 cylinder CI engine, there are no sparks occurring as it is a compression ignition engine. The combustion process is initiated by the high temperature and pressure in the cylinder, caused by the compression of the air-fuel mixture. Therefore, the correct answer is "None".

Dispersion refers to the distribution of fuel particles in the cylinder in order to achieve a better fuel-air mixture. This process ensures that the fuel particles are evenly distributed throughout the combustion chamber, allowing for efficient and complete combustion. By dispersing the fuel particles, a larger surface area is exposed to the air, promoting better mixing and combustion. This leads to improved fuel efficiency and reduced emissions.

Increasing the temperature of intake air can increase the brake power of a diesel engine. This is because when the temperature of the intake air is increased, the air becomes less dense. This allows for a larger volume of air to enter the combustion chamber, resulting in more efficient combustion and increased power output.