How changes in the thermal efficiency of a combustion engine can affect its performance?

However, it is possible to make improvements with regard to combustion efficiency. Combustion efficiency is the rate at which an engine converts fuel into energy. Particularly with heavy fuels with high-energy densities — diesel, fuel oil, bunker fuel, etc.

Why is the thermal efficiency of diesel engine higher than that in gasoline engine?

Because diesel has a higher compression resistance — because it is denser than light distillate fuels — engineers can design and develop diesel engines with higher compression ratios than gasoline engines. The higher the compression ratio of an engine, the greater the thermal efficiency.

What causes a piston to melt in a diesel engine?

A burned piston will typically have a melted appearance, or a hole burned completely through the top of the piston. Aluminum can only withstand so much heat, and when it gets too hot, it melts. The underlying cause is usually detonation and/or pre-ignition.

How changes in thermal efficiency affect performance?

Carnot Efficiency The energy for work comes from a decrease in the total energy of the fluid used in the system. Therefore the greater the temperature change, the greater this decrease in the fluid and thus the greater energy available to do work is.

What are the factors affecting thermal efficiency?

This study presents a simple method to quantitatively distinguish the factors that cause the thermal efficiency of a heat engine to be less than unity. These factors are the nonzero reference point, external irreversibilities and internal irreversibilities.

Why is a diesel engine more efficient at converting the fuel’s energy into work?

A diesel engine burns its fuel at a higher temperature than a gasoline engine. Efficiency increases as the temperature difference between the hot and cold objects increases. Thus, the hotter the fuel burns, the higher the efficiency.

What causes diesel engine failure?

The most common challenge leading to the failure of diesel engines is the mixture of water with diesel fuel. Some of the most common ways water can get into your fuel system include; Condensation of water in your fuel tank. This can be caused by inefficiencies during transportation or storage of the fuel.

What causes piston scoring?

Scuffing leads to scoring, which is deeper, more severe scratching in the piston. Scoring is an advanced stage of scuffing that signals much heavier levels of friction. Scoring usually occurs when one or more piston rings fail and the minor level of movement is allowed between the piston and valve wall.

How can we increase thermal efficiency of diesel engine?

1. Run the engine fuel-lean, that is, use excess air. It is well known that fuel-lean running improves the efficiency.
2. Higher compression ratio.
3. We need new cycles put into practical use.
4. Run the engine at optimum conditions, meaning low friction (modest engine speed) and low pumping work (air throttle more open).

How does heat input effect thermal efficiency?

If 200 joules of thermal energy as heat is input (), and the engine does 80 J of work (), then the efficiency is 80J/200J, which is 40\% efficient. For example, if 200 J is put into the engine, and observe 120 J of waste heat, then 80 J of work must have been done, giving 40\% efficiency.

What is the coefficient of thermal expansion?

The coefficient of thermal expansion is defined such that α measures the percentage change in the length of the material per degree of temperature change.

How do you calculate the coefficient of thermal expansion with a dilatometer?

Dilatometers can also be used to calculate the coefficient of thermal expansion. To determine the coefficient, the volume of the material is carefully measured as the temperature rises from one known value to another.

What is the difference between linear and volume thermal expansion?

They are thought to have a coefficient of linear thermal expansion instead of a coefficient of volume thermal expansion. This coefficient acts the same as the three-dimensional coefficient of expansion, except it corresponds to the fractional increase in length (instead of volume) per degree temperature.

Why are metals used to measure thermal expansion?

Metals tend to have relatively low coefficients, but they also have very high melting points, and they are not as perceptible to a material failure caused by the stress of expansion. This makes metals ideal candidates to use when measuring thermal expansion.