  A leading model for Type Ia supernovae (SNe Ia) begins with a white dwarf
near the Chandrasekhar mass that ignites a degenerate thermonuclear runaway
close to its center and explodes. In a series of papers, we shall explore the
consequences of ignition at several locations within such dwarfs. Here we
assume central ignition, which has been explored before, however, the problem
is worth revisiting, if only to validate those previous studies and to further
elucidate the relevant physics for future work. A perturbed sphere of hot iron
ash with a radius of ~100 km is initialized at the middle of the star. The
subsequent explosion is followed in several simulations using a thickened flame
model in which the flame speed is either fixed --- within the range expected
from turbulent combustion --- or based on the local turbulent intensity. Global
results, including the explosion energy and bulk nucleosynthesis (e.g. 56Ni of
0.48--0.56 $\Msun$) turn out to be insensitive to this speed. In all completed
runs, the energy released by the nuclear burning is adequate to unbind the
star, but not enough to give the energy and brightness of typical SNe Ia. As
found previously, the chemical stratification observed in typical events is not
reproduced. These models produce a large amount of unburned carbon and oxygen
in central low velocity regions, which is inconsistent with spectroscopic
observations, and the intermediate mass elements and iron group elements are
strongly mixed during the explosion.

High Energy Astrophysical Phenomena;Solar and Stellar Astrophysics