Question: answer the following questions about the hydrogen usage in automobiles...
Answer the following questions about the hydrogen usage in automobiles.
a. Hydrogen has four main advantages including high knock resistance, high calorific value, high turbulent flame speed and its compatibility with the existing SI engine architecture. However, the onboard hydrogen storage poses a significant challenge. Briefly discuss this issue for the case of compressed hydrogen gas storage and liquified hydrogen storage.
b. Identify a pollutant in the exhaust stream of hydrogen SI engine and explain its environmental impact.
c. If hydrogen is used in a compression ignition engine for higher efficiency than that can be achieved in the SI engine, its high auto-ignition temperature requires a very high compression ratio. However, the increased compression ratio would cause hydrogen pre-ignition and knocking issues. Suggest a method that can avoid the knocking and maintain reliable hydrogen flame propagation.
d. Hydrogen fuel cell is an alternative method of using this non-carbon fuel for energy conversion. If a solid oxide fuel cell operates at 1500 K and the combustion temperature of an engine is measured at 2000 K, which energy converter will achieve higher theoretical maximum thermal efficiency? Explain the reason using the Gibbs free energy, enthalpy and Carnot Cycle.
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