  We undertake a theoretical study of a finite-time quantum Otto engine cycle
driven by inter-particle interactions in a weakly interacting one-dimensional
Bose gas in the quasicondensate regime. Utilizing a $c$-field approach, we
simulate the entire Otto cycle, i.e. the two work strokes and the two
equilibration strokes. More specifically, the interaction-induced work strokes
are modelled by treating the working fluid as an isolated quantum many-body
system undergoing unitary evolution. The equilibration strokes, on the other
hand, are modelled by treating the working fluid as an open quantum system
tunnel-coupled to another quasicondensate which acts as either the hot or cold
reservoir, albeit of finite size. We find that, unlike a uniform 1D Bose gas, a
harmonically trapped quasicondensate cannot operate purely as a \emph{heat}
engine; instead, the engine operation is enabled by additional \emph{chemical}
work performed on the working fluid, facilitated by the inflow of particles
from the hot reservoir. The microscopic treatment of dynamics during
equilibration strokes enables us to evaluate the characteristic operational
time scales of this Otto chemical engine, crucial for characterizing its power
output, without any \emph{ad hoc} assumptions about typical thermalization
timescales. We analyse the performance and quantify the figures of merit of the
proposed Otto chemical engine, finding that it offers a favourable trade-off
between efficiency and power output, particularly when the interaction-induced
work strokes are implemented via a sudden quench. We further demonstrate that
in the sudden quench regime, the engine operates with an efficiency close to
the near-adiabatic (near maximum efficiency) limit, while concurrently
achieving maximum power output.
