Realistic Explosion

1. Make a new document sized 2000x2000, background black. (Screenshots will be 200x200 for space sake)

Make a new layer, and paint it black aswell.

2. Press D to reset your colors, and then go Filter->Render->Difference Clouds 4-6 times.

3. Go Filter->Render->Lighting Effects with the following settings:

Light Type: Spotlight (Make the thing on the left a perfect circle. You can do this by holding shift when you go to resize it.)
Color: #FFF000
Intensity: 20
Focus: 50

Color: #CC0000
Gloss: 40
Material: 100
Exposure: 40
Ambience: 40

4. Go Image->Adjustments->Levels (Control+L) and do the following:

Red
Dark Output->100

Blue
Dark Output->50

Green
Midtones-> 0.85

5. Make a new layer, fill it white, and go Filter->Render->Fibers with the following settings:

Variance 5
Strength 45

6. Filters->Distort->Polar Coordinates, and choose Rectangular to Polar

Filters->Blur->Radial Blur with the following settings:

Quality: Best
Amount: 100
Method: Zoom

7. Image->Adjustments->Levels and on the RGB channel, change the White Output level to about 170, set layer to Hard Light, opacity to around 60%

8. On the layer with the 'fire' on it, go Filters->Distort->Glass with the following settings:

Distortion: 9
Smoothness: 12
Texture: Frosted
Scaling: 125
Invert: Yes

9. Take a sample of the yellow, then go Select->Color Range, set Fuzziness to 70%

Keeping the selection, make a new layer, fill the selection with white.

Deselect and go Filters->Blur->Radial Blur with the following settings:

Quality: Best
Amount: 35
Method: Zoom

10. Once again select the 'fire' layer and go Image->Adjustments->Levels and on the green channel set Midtone to 1.45

11. Now select the layer on top, select all, then go Shift+Control+C

Go to the channels window, and create a new channel

Go Control+V into this new channel, then load it as a selection, then invert the selection by going Control+Shift+I

Make a new layer and fill the selection in with a dark red, I used #460D0D, make the layer mode Hard Light

12. Now, we just need to black out the unneeded spots around the explosion, so take a soft black brush to the outsides, and your done!