  We present a new time-dependent inhomogeneous jet model of non-thermal blazar
emission. Ultra-relativistic leptons are injected at the base of a jet and
propagate along it. We assume continuous reacceleration and cooling, producing
a relativistic quasi-maxwellian (or "pile-up") particle energy distribution.
The synchrotron and Synchrotron-Self Compton jet emissivity are computed at
each altitude. Klein-Nishina effects as well as intrinsic gamma-gamma
absorption are included in the computation. Due to the pair production optical
depth, considerable particle density enhancement can occur, particularly during
flaring states.Time-dependent jet emission can be computed by varying the
particle injection, but due to the sensitivity of pair production process, only
small variations of the injected density are required during the flares. The
stratification of the jet emission, together with a pile-up distribution,
allows significantly lower bulk Lorentz factors, compared to one-zone models.
Applying this model to the case of PKS 2155-304 and its big TeV flare observed
in 2006, we can reproduce simultaneously the average broad band spectrum of
this source from radio to TeV, as well as TeV light curve of the flare with
bulk Lorentz factor lower than 15.
