If this is your first visit, be sure to check out the FAQ by clicking the link above. You may have to register before you can post: click the register link above to proceed. To start viewing messages, select the forum that you want to visit from the selection below. |
|
|
Thread Tools | Display Modes |
#21
|
|||
|
|||
|
Ads |
#22
|
|||
|
|||
Alex Rodriguez wrote:
> In article >, > says... > > >>People say that all a supercharger does is cram more fuel/air mixture >>into the cylinder, but that is a very simplistic and inaccurate description, >>as it leaves important stuff out. > > > That's all it does. It is a simple device. > ---------------- > Alex > > Let's talk about the air. Ratio-wise the fuel is a small fraction, and the charger does not ordinarily affect the fuel distribution since it is usually but not always added AFTER the charger. A non-supercharged engine is technically called a normally aspirated engine, from the medical term aspiration for breathing. Even if the pressure in the cylinder dropped to absolute pressure of zero the maximum pressure difference driving air into cylinder would be 14.7 pounds. At high rpm this is not enough pressure to fill cylinder. Even if it did, the weight of the air would be the weight of that displacement volume of air. Supercharging compresses air to a higher pressure and density. The higher pressure does a better job of filling the cylinder quickly. Even more important, however, if we double the pressure of the air being crammed into the cylinder (and if we intercool it to prevent too high a temperature rise) the density of the charge in the cylinder will be doubled. Now, the weight of fuel in the charge must be proportional to the wieght of the air (NOT the volume). If we double the weight of air in the cylinder, double the fuel weight and double the energy content is in the charge to be ignited. The reason for intercoolers is to prevent the air from getting too hot. Since density is INVERSELY proportional to temperature (on the absolute scale) an increase in temp reduces the density and hence weight of the charge. BTW, compressing air raises its temp, and it IS possible to raise the air temp so high in a high pressure supercharger that the temp reaches the ignition temp of the fuel/air mix- bad situation. This was a problem with early P-38s in WW2. |
Thread Tools | |
Display Modes | |
|
|
Similar Threads | ||||
Thread | Thread Starter | Forum | Replies | Last Post |
rec.autos.makers.chrysler FAQ, Part 1/6 | Dr. David Zatz | Chrysler | 5 | July 10th 05 05:24 AM |
rec.autos.makers.chrysler FAQ, Part 1/6 | Dr. David Zatz | Chrysler | 5 | June 24th 05 05:27 AM |
rec.autos.makers.chrysler FAQ, Part 1/6 | Dr. David Zatz | Chrysler | 5 | June 8th 05 05:28 AM |
rec.autos.makers.chrysler FAQ, Part 1/6 | Dr. David Zatz | Chrysler | 5 | May 24th 05 05:27 AM |
rec.autos.makers.chrysler FAQ, Part 1/6 | Dr. David Zatz | Chrysler | 4 | February 2nd 05 05:22 AM |