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Research Abstracts Online
January 2010 - March 2011

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University of Minnesota Twin Cities
College of Science and Engineering
Department of Mechanical Engineering

PI: Zongxuan Sun

Design, Modeling, and Control of an HCCI Free Piston Engine

A free piston engine (FPE) is a device where the linear motion of the piston is not constrained by a crankshaft. The advantage of this setup is the ability to run with varying compression ratios, thus enabling multi-fuel capability and homogeneous charge compression ignition (HCCI). The nature of this device requires precise control over the fuel, air, and piston motion. To enable this, a deep understanding of the constituent processes and hardware subsystems is necessary.

One of these processes is the in-cylinder mixing between fresh air/fuel mixtures and hot, residual exhaust gas. CFD analysis using KIVA is used to characterize the behavior of in-cylinder fluid motion as a result of a novel valve strategy. The results of this characterization are used to quantify the degree of mixing in the cylinder, which leads to the development and refinement of valve strategies.

The independent control of the intake and exhaust valves is enabled using a novel camless hydraulic engine valve actuation system. Experimental and simulation studies using a prototype system have motivated the redesign of a flow regulating spool valve to improve the performance of the hydraulic actuator. CFD analysis using FLUENT is currently being used to iterate between different designs and understand the flow dynamics inside the spool valve.

The power generated by FPE can be captured and transformed to electrical power using a linear alternator. To find the induced voltages and currents and also the opposing forces generated by the linear alternator, it is necessary to model its magnetic circuit. To do this Maxwell-2D was employed and two-dimensional axisymmetric analysis of the linear alternator was performed. Based on the coil flux linkages data obtained from this analysis, a Simulink model was developed using MATLAB that makes it easier to integrate the linear alternator model into FPE model and perform a thorough analysis of the device.

Group Members

Pradeep Kumar Gillella, Graduate Student
Matthew McCuen, Graduate Student
Ali Sadigni, Research Associate
Wilson Santiago, Graduate Student