EGRM 303 Thermal Systems Design Homework #1 Due in-class on Wednesday (February
ID: 1717842 • Letter: E
Question
EGRM 303 Thermal Systems Design Homework #1 Due in-class on Wednesday (February 03, 2016) A developer wishes to have the most efficient cars for fuel consumption. List and discribe at least 5 general considerations you should stipulate in the design to yield a workable (satisfactory) solution. What factors (minimum of 3) might be involved in defining an optimal solution to this problem? Note that you should give these factors in terms of trade-offs [for example: the factor X goes up (maybe that is good) then the factor Y goes down (maybe that is bad)]Explanation / Answer
Consider a petrol engine car.
A) The 5 general considerations are
1. Mixing of air and fuel in right proportion
2. How long it has been since the preparation of air fuel mixture to its actual injection into cylinder.
3. How well is the air and fuel mixed as it enters into combustion chamber
4. Nature of travel experienced by air fuel mixture (pipe length & bends)
5. How is the excess air fuel mixture managed
B) factors
1. Quantity of air in air fuel mixture: if air is less than required, the combustion will not be complete. So little quantity of fuel has to leave without getting combusted resulting in fuel loss. On the other hand, if air more than required, sufficient quantity of energy cannot be liberated within each cycle. It also leafs to avoidable pumping energy wastage.
2. How long it has been since the preparation of air fuel mixture to its actual injection into cylinder: If charge (air fuel mixture) has to travel a long distance, it should be prepared well in advance. But this can lead to settlement of fine fuel droplets at few regions and there by combustion is ineffective. If charge in not prepared in advance, the flow losses and other factors can lessen the quantity of charge that is entering into the combustion chamber. There by performance is badly effected.
3. How is the excess air fuel mixture managed: if unutilized charge is ignored, the charge may loose its quality as the fuel droplets get settled at one place and sometimes fuel may also get deposited on surfaces available there. Hence unutilised charge should be managed to acooid wastage of fuel.
The optimized way of handling air fuel mixture would be
To mix the fuel just before the entry of charge into combustion chamber. And use only that quantity of fuel that is required for complete combustion. This ensures thorough mixing as well as increased performance with respect to fuel consumption.
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