Single-cylinder test engines are used extensively in engine research, and sparingly in engine development, as an inexpensive way to test or evaluate new concepts or to understand in-cylinder motion or combustion. They also allow good access to the cylinder for instrumentation, however, these single-cylinder engines differ significantly in rotational dynamics, gas intake dynamics, heat transfer dynamics, dynamic coupling between cylinders, and in other areas. Charge motion within the cylinder, even during the closed period differs from the multi-cylinder engine because of the differences in both instantaneous flow and momentum.

Researchers in the Powertrain Control Research Laboratory (PCRL) at the University of Wisconsin-Madison have developed single-cylinder engine transient test systems that control the instantaneous dynamic cylinder boundary conditions to replicate those in the target multi-cylinder engine. The overall goal is to exploit the benefits of the single-cylinder engine, while eliminating the negative aspects of this device, and to have the single-cylinder “think” it is dynamically operating within a multi-cylinder engine.

This paper describes the latest developments in controlling the intake gas dynamics of the single-cylinder engine to meet these goals. A combination of both rotary and proportional valves are used to accurately replicate the instantaneous intake airflow that exists in the multi-cylinder engine, including during transients. A Fourier-based approach instead of the previous time-based trajectory control is used to accomplish these goals. This is a third generation of intake air simulator (IAS3) that is a significant step forward in both simplifying the system, and in significantly expanding the operating envelop of the engine to include the full engine operating range of the multi-cylinder engine. A brief introduction of the entire transient test system will show the reader how rotational, heat transfer, and gas dynamics are controlled, and how the IAS3 fits into this overall system.

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