Experimental Analysis of a Uniflow Scavenged Two-Stroke Concept

Stefan Sturm*, Stephan Schmidt, Michael Lang, Roland Kirchberger

*Corresponding author for this work

Research output: Contribution to journalConference articlepeer-review


The target data for a modern two-stroke engine used in the automotive sector, for example as a hybrid compound in a Plugin Hybrid Electric Vehicle (PHEV) or Range Extender Electric Vehicle (REX), include a range of demands and challenges to be a viable alternative to the four-stroke engine. A modern two-stroke concept must achieve at least at the same level of the durability requirements and should have also advantages in terms of packaging, cost and weight. A major challenge is to generate a gas-exchange process which reduces the loss of fuel and air during the scavenging process to a minimum and enables a stochiometric exhaust gas. In a two-stroke engine, the in-cylinder burned gases of the previous combustion cycle are scavenged out of the cylinder by the inflow fresh air. Therefore, an implementation of a 3-way catalyst as an effective aftertreatment system with operation at a stochiometric combustion requires a highly efficient scavenging and fuel injection strategy throughout the entire operational range to avoid possible losses of fresh air and fuel towards the exhaust line.
One solution approach includes a novel uniflow scavenging concept with internal mixture preparation and separate auxiliaries. On the basis of a prior concept and simulation study, a promising two-stroke prototype was developed and prepared for testbench verification. In order to prove the functionality of this concept, a single cylinder research engine was built with an external electric scavenging blower, a separated cooling and lubrication system and an external high pressure fuel preparation. This method ensures a high level of design freedom during the development process and flexibility for the engine parameters on the testbench.
For validation the developed uniflow prototype concept was compared to a reference engine, a classic loop scavenging principle with the same geometrical dimensions. Both engine types are based on the same crankshaft, conrod, piston and crankcase with the same oil, fuel and blower periphery system. Only the developed and designed cylinder and cylinder head were different between the scavenging principle.
Original languageEnglish
Article number2022-32-0012
JournalSAE Technical Papers
Publication statusPublished - 3 Nov 2022
EventSETC Small Powertrain and Energy Systems Conference 2022: SETC 2022 - Himeji, Japan, Himeji, Japan
Duration: 30 Oct 20223 Nov 2022
Conference number: 2022

Fields of Expertise

  • Mobility & Production

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