Assertion (A): Excess air supplied to a combustor increases the effici...
Excess air up to a limit increases efficiency, but beyond that the efficiency decreases for the reason given in R
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Assertion (A): Excess air supplied to a combustor increases the effici...
Excess air supplied to a combustor increases the efficiency of combustion.
- Combustion is a chemical reaction between a fuel and oxygen, resulting in the release of heat energy. The efficiency of combustion refers to how effectively this heat energy is converted into useful work.
- Excess air refers to supplying more oxygen than is required for complete combustion. It is often done to ensure that all the fuel is completely burned, minimizing the production of harmful pollutants.
- Excess air can indeed increase the efficiency of combustion due to the following reasons:
1. Complete combustion: When excess air is supplied, there is an abundance of oxygen available for the fuel. This ensures that the fuel is completely burned, resulting in a more efficient combustion process. Incomplete combustion can lead to the formation of carbon monoxide (a harmful pollutant) and the loss of potential energy.
2. Increased flame temperature: Excess air tends to lower the temperature of the products of combustion. This is because the excess air absorbs some of the heat energy from the combustion process. However, this lower temperature does not necessarily decrease the overall efficiency of combustion. In fact, it can increase the flame temperature, leading to better heat transfer and more efficient energy conversion.
3. Reduced pollutants: Excess air helps in minimizing the production of harmful pollutants like carbon monoxide (CO) and unburned hydrocarbons (UHC). These pollutants are formed due to incomplete combustion. By supplying excess air, the combustion process becomes more complete, resulting in lower emissions of these pollutants.
Excess air tends to lower the temperature of the products of combustion.
- The reason given for the above assertion is that excess air tends to lower the temperature of the products of combustion.
- This reason is not a correct explanation for the assertion because although excess air does lower the temperature of the products of combustion, it does not necessarily decrease the overall efficiency of combustion. As explained earlier, excess air can actually increase the flame temperature, leading to better heat transfer and more efficient energy conversion.
Therefore, both Assertion (A) and Reason (R) are individually true, but Reason (R) is not the correct explanation of Assertion (A). Hence, the correct answer is option 'D' - A is false but R is true.
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