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GATE Exam » GATE Study Materials » Mechanical Engineering » Specific Power Output
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Specific Power Output

Specific power, also known as power-to-weight ratio, is a measurement of performance that can be applied to an engine in a power plant or a vehicle.

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The power-to-weight ratio (PWR), also known as specific power or power-to-mass ratio, is a calculation that is commonly applied to engines and mobile power sources in order to enable comparisons between different units or designs. Other names for this calculation include power-to-mass ratio and power-to-weight ratio. A measurement of an engine’s or power source’s actual performance can be found in the power-to-weight ratio. It is also used as a measurement of the performance of a vehicle as a whole. For this purpose, the power output of the engine is divided by the weight (or mass) of the vehicle, which results in a metric that is unaffected by the dimensions of the vehicle. The power-to-weight ratio is typically stated by manufacturers as the peak value; however, the real number may change depending on the application, and these fluctuations will have an effect on the overall performance.

Weight-to-power ratio, also known as power loading, is a calculation that is frequently applied to aircraft, automobiles, and vehicles in general. This calculation is used so that the performance of one vehicle can be compared to that of another vehicle. The power-to-weight ratio of any vehicle is calculated by multiplying the vehicle’s velocity by its thrust per unit of mass.

A measurement of an engine’s performance is its specific output. It is a metric that measures the effectiveness of an engine by comparing the amount of braking horsepower it produces to its overall displacement. Kilowatts or horsepower are typically used to express the measurement, and it is typically expressed in terms of litres or cubic inches. This measurement makes it possible to compare engines of varying sizes. When comparing engines of the same size, those with forced induction often have better performance than those with naturally aspirated engines.

Specific Power:

The formula for calculating the power-to-weight ratio, also known as specific power, for an engine (power plant) is the power generated by the engine divided by the mass of the engine. In this context, the term mass is more commonly referred to as weight. To understand why this is the case, one must first recognise that the “power to weight ratio” of an electric motor does not represent an infinite value in a setting with zero gravity.

With a mass of 380 kilograms (840 pounds) and a power output of 250 kilowatts (340 horsepower), a standard turbocharged V8 diesel engine has a power-to-weight ratio of 0.65 kilowatts per kilogramme (0.40 horsepower per pound).

Turbines, in many cases, are good examples of things that have high power-to-weight ratios. This is due to the fact that they are capable of functioning at extremely high rates. For instance, the main engines of the Space Shuttle were equipped with turbopumps, which are machines that consist of a pump that is driven by a turbine engine. These turbopumps were used to feed the propellants (liquid oxygen and liquid hydrogen) into the combustion chamber of the engine. The first liquid hydrogen turbopump is about the same size as an automobile engine, weighs about 352 kilograms (775 lb), and generates 72,000 horsepower (54 MW) for a power-to-weight ratio of 153 kW/kg (93 hp/lb). Its dimensions are comparable to those of a jet engine.

Engine Power:

Using a dynamometer to measure torque and rotational speed allows one to calculate the useful power that an engine with shaft power output produces. One reaches their maximum power output when the torque multiplied by the rotational speed is at its highest possible value. When it comes to jet engines, the amount of usable power is determined by multiplying the aircraft’s cruising speed by the amount of force, also known as net thrust, that is necessary to maintain that speed. When determining the effectiveness of the propelling force, it is factored in.

Heat Engines and Heat Pumps:

The molecular kinetic energy and the latent phase energy combine to provide the thermal energy that we experience. Heat engines are devices that are capable of converting thermal energy in the form of a temperature gradient between a hot source and a cool sink into other forms of mechanical effort that is desirable. In order to regenerate thermal energy in response to a temperature gradient, heat pumps require the application of mechanical work. When attempting to interpret how the thrust of a jet or rocket engine is transferred to the vehicle, it is important to use definitions that are considered standard.

Conclusion:

Specific power, also known as power-to-weight ratio, is a measurement of performance that can be applied to an engine in a power plant or a vehicle. A measurement of an engine’s or power source’s actual performance can be found in the power-to-weight ratio. It is also used as a measurement of the performance of a vehicle as a whole. The power-to-weight ratio is typically stated by manufacturers as the peak value; however, the real number may change depending on the application, and these fluctuations will have an effect on the overall performance. Kilowatts or horsepower are typically used to express the measurement, and it is typically expressed in terms of litres or cubic inches.

The formula for calculating the power-to-weight ratio, also known as specific power, for an engine (power plant) is the power generated by the engine divided by the mass of the engine.

Turbines, in many cases, are good examples of things that have high power-to-weight ratios. This is due to the fact that they are capable of functioning at extremely high rates.

Using a dynamometer to measure torque and rotational speed allows one to calculate the useful power that an engine with shaft power output produces. Heat engines are devices that are capable of converting thermal energy in the form of a temperature gradient between a hot source and a cool sink into other forms of mechanical effort that is desirable.

faq

Frequently asked questions

Get answers to the most common queries related to the GATE Examination Preparation.

How much power does the turbine actually produce?

Ans: It is expressed commonly in units of watts per kilogramme or horsepower per pound and is defined as the power o...Read full

How much power does this particular device consume?

Ans: The purpose of the SEC is to give an indication of how much energy is required to produce one unit of a product...Read full

What are some ways that a gas turbine's efficiency might be improved?

Ans: Therefore, the efficiency of gas turbines can be improved by cooling the air that goes into them. This is espec...Read full

What exactly is the product of the work?

Ans: The amount of shaft work that is produced by a gas turbine for each unit mass of gas that is passed through the...Read full

How much power do speakers actually put out?

Ans: Audio power, which is measured in watts, is the amount of electrical power that is delivered from an audio ampl...Read full

Ans: It is expressed commonly in units of watts per kilogramme or horsepower per pound and is defined as the power output divided by its mass.

Ans: The purpose of the SEC is to give an indication of how much energy is required to produce one unit of a product. It’s possible that SEC is employed because of how convenient it is; specifically, the fact that the amount of energy may be directly reported per quantity of product.

 

Ans: Therefore, the efficiency of gas turbines can be improved by cooling the air that goes into them. This is especially useful in regions where the temperature is hot and dry.

Ans: The amount of shaft work that is produced by a gas turbine for each unit mass of gas that is passed through the turbine. It is calculated by dividing the power of the shaft by the volumetric flow rate of the gas.

Ans: Audio power, which is measured in watts, is the amount of electrical power that is delivered from an audio amplifier to a loudspeaker. Together with the loudspeaker’s efficiency, the amount of electrical power that is provided to it is what defines the amount of sound power that is produced.

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