The Design, Construction, Simulation and Testing of a Novel Prototype Two-Stroke Opposed-Piston Engine

Furze, Samuel Frederick (2025) The Design, Construction, Simulation and Testing of a Novel Prototype Two-Stroke Opposed-Piston Engine. Doctoral thesis, University of East Anglia.

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Abstract

Climate change is of increasing concern globally, and there are extensive efforts to curb greenhouse gas emissions rates from many sectors of society, including transportation. Low-carbon fuels like biomethane are an important option in this respect, and using them more efficiently could help maximise their positive impact. Opposed-piston two-stroke engines might offer this opportunity. They are increasingly well-proven in compression ignition form, benefitting from thermodynamic advantages like a higher stroke-to-bore ratio, uniflow scavenging, and reduced heat loss to coolant. However, bio-methane and similar fuels are very well-suited to spark ignition: contemporary examples of spark ignition opposed piston engines, which face challenges such as a large flame propagation distance and lack of tumble, are rare. In this project therefore, a new and novel design of spark ignition opposed piston engine, dedicated to the task of engine research, was proposed. The engine design was based on key identified requirements. These included that it be self-scavenging, with this process de-coupled from piston motion, and feature a separated oil-system and computer-controlled direct fuel injection. Critically, it required the ability to incorporate a cylinder-pressure transducer for future data acquisition. Numerous parts were designed in-house and machined both at the University of East Anglia and an external supplier, and these were coupled with select off-the-shelf parts to reduce manufacturing effort. The resulting engine is compact at less than 120 cm3 swept volume, with a maximum engine case dimension of less than 450 mm. Computational fluid dynamics simulations were also performed of the air side cylinder surfaces, generating a fuelling map that was used to program the engine control unit for testing. Useful indicators for real engine behaviour were gained in addition: for example, in a fuelled simulation case at 5000 rpm and 150 kPa scavenge pressure the required fuel was more than 40 % over-estimated. This suggested that scavenging performance decreases markedly at higher engine speeds and lower scavenge pressures. Conversely, at 1500 rpm and 120/150/180 kPa, and 3000 rpm and 150/180 kPa, results suggested the motored simulations were able to predict the required fuel within 2%. Furthermore, three-dimensional visual results indicated the swirling intake port geometry may be able to improve combustion rates, by distorting the flame front around the combustion chamber rather than letting it progress radially. The most significant results however were gained when the design and simulation work were tested by trying to fire the engine for the first time. Despite a persistent over-fuelling issue, the engine started and ran smoothly, proving the initial success of the design. It therefore represents a significant research contribution and opportunity for further engine research, however additional work is required before it can be fully commissioned. This includes resolving the over-fuelling issue, as well as remedial modification to the timing system to prevent timing belt failure. Following this, sustained running under a load whilst using the cylinder pressure transducer could provide vital information over how well the design works under different conditions.

Item Type:	Thesis (Doctoral)
Faculty \ School:	Faculty of Science > School of Engineering, Mathematics and Physics
Depositing User:	Chris White
Date Deposited:	24 Jun 2025 07:44
Last Modified:	24 Jun 2025 07:44
URI:	https://ueaeprints.uea.ac.uk/id/eprint/99686
DOI:

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