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18/10/2020

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03/10/2020

Newcastle’s Northumbria University has confirmed that 770 of its students have tested positive for coronavirus, with nearly 80 showing symptoms. Another, smaller, outbreak was reported by nearby Newcastle University.

03/10/2020

Nature

03/10/2020

Modeling, lab work, and perhaps a mission to the planet will be required to understand the chemical reactions that take place within Venus’s hot, dense, oxidizing cloud layers.

03/10/2020

This video shows how to solve an equation of type : a^x+b^x=c^x For this example we are not looking for a general solution but to solve for a=4 b=6 c=9 Faceb...

10/09/2020

USE IN

The theoretical maximum power output from a hydrogen engine depends on the air/fuel ratio and fuel method
used.

The stoichiometric air/fuel ratio for hydrogen is 34:1. At this air/fuel ratio, hydrogen will displace 29% of the combustion chamber leaving only 71% for the air. As a result, the energy content of this mixture will be less than it would be if the fuel were gasoline (since gasoline is a liquid, it only occupies a very small volume of the combustion chamber, and thus allows more air to enter).
Since both the carbureted and port injection methods mix
the fuel and air prior to it entering the combustion chamber,
these systems limit the maximum theoretical power obtainable to approximately 85% of that of gasoline engines.

For direct injection systems, which mix the fuel with the air after the intake valve has closed (and thus the combustion chamber has 100% air), the maximum output of the engine can be approximately 15% higher than that for gasoline engines.

Therefore, depending on how the fuel is metered, the maximum output for a hydrogen can be either 15% higher or 15% less than that of gasoline if a stoichiometric air/fuel ratio is used. However, at a stoichiometric air/fuel ratio, the combustion temperature is very high and as a result it will form a large amount of oxides (NOx), which is a criteria . Since one of the reasons for using hydrogen is low exhaust , hydrogen engines are not normally
designed to run at a stoichiometric air/fuel ratio.
Typically hydrogen engines are designed to use about twice
as much air as theoretically required for complete combustion. At this air/fuel ratio, the formation of NOx is reduced to near zero. Unfortunately, this also reduces the power output to about half that of a similarly sized engine.

To make up for the power loss, hydrogen engines are usually
larger than gasoline engines, and/or are equipped with turbochargers or superchargers.

Source: US. D.O.E. Hydrogen Office - Hydrogen Fuel Cell Engines and Related Technologies: Rev 0, December 2001

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