  We study a one-dimensional mixture of active (run-and-tumble) particles and
passive (Brownian) particles, with single-file constraint, in a sawtooth
potential. The active particles experience a ratchet effect: this generates a
current, which can push passive particles against an applied load. The
resulting system operates as an active engine. Using numerical simulations, we
analyse the efficiency of this engine, and we discuss how it can be optimised.
Efficient operation occurs when the active particles self-organise into teams,
which can push the passive ones against large loads by leveraging collective
behaviour. We discuss how the particle arrangement, conserved under the
single-file constraint, affects the engine efficiency. We also show that
relaxing this constraint still allows the engine to operate effectively.
