This study investigates the feasibility of a novel internal combustion engine
(ICE) architecture, termed the membrane engine, in which the conventional piston
is replaced by a flexible elastic membrane. Although the concept appears in
several patent documents proposing reduced friction, improved sealing, and lower
heat losses, no empirical data has been published to support these claims. To
the authors’ knowledge, this work presents the first membrane engine built and
experimentally tested. The primary aim is to verify whether such an engine can
operate as a functional ICE, regardless of its current efficiency or performance
level.
To support concept validation, a simplified mathematical model was developed to
describe the membrane’s deformation and its effect on combustion chamber volume.
Unlike conventional piston engines, the membrane introduces a pressure-dependent
geometry, enabling a variable compression ratio. The model is not intended to
predict performance but to assist in interpreting experimental results and
assessing feasibility. It combines geometric and pressure-induced volume changes
and was constructed conservatively to avoid overestimating deformation
effects.
A single-cylinder spark-ignition prototype was built by modifying an existing
piston engine. Experimental tests were conducted under motored and fired
conditions, with comparative measurements taken against the unmodified engine.
Results confirmed that the membrane engine can sustain combustion and produce
torque. Notably, the exhaust stroke exhibited a steeper pressure drop,
suggesting improved scavenging, and the torque trace showed a distinct positive
spike post-combustion. These findings support the hypothesis that the membrane’s
dynamic behavior influences combustion and gas exchange.
While some patent claims remain unverified, the study demonstrates that the
membrane engine is a viable concept. The results provide a foundation for
further development and refinement, including material selection and advanced
modeling. Future work will focus on improving durability, expanding the
operating envelope, and exploring hybrid configurations for waste heat
recovery.
