Experimental engine characterization for spring design of novel automotive starter

Date of Award

2013

Degree Name

M.S. in Mechanical Engineering

Department

Department of Mechanical and Aerospace Engineering

Advisor/Chair

Advisor: David H. Myszka

Abstract

Automotive starting systems require substantial amounts of mechanical energy in a short period of time. Lead-acid batteries have historically provided that energy through a motor. Springs have been identified as an alternative energy storage medium and are well suited to engine-starting applications due to a long service life and the ability to rapidly deliver substantial mechanical power. Spring-based engine starters exist for large commercial diesel engines but are not readily available for automobiles. A conceptual spring-based engine starter has been developed at the University of Dayton, including assembly of a proof-of-concept prototype. This research continued the development of the spring-starter system, with the objective of determining whether a spring of acceptable size could provide the required torque and rotational speed to start an automobile engine. Engine testing was required to determine the torque and engine speed during cranking, followed by predicting engine response for several spring options. A 600 cm³ displacement inline 4-cylinder internal combustion engine was acquired as a scaled down approximation of an automobile engine. The starter motor was tested with a Prony brake to determine the torque produced as a function of current draw. The engine was then cranked by the starter, and current draw was measured with engine position over time. Engine torque over time was determined from current data. The polar moment of inertia of the rotating mass of the engine was found by observed data, and an equation relating engine torque, acceleration, and friction was developed to characterize the engine during cranking. This equation was used with spring design equations to build a Simulink model of predicted engine response for a spring of given stiffness and initial displacement. Results predict that the test engine could be started by a torsional spring of steel with diameter and length of approximately 6 in. This is similar in size to the electrical starting system of the engine, suggesting that a torsional spring of reasonable size is capable of starting an automobile engine. Work is still required to determine how such a spring would be mounted, rewound, and controlled in an automotive context.

Keywords

Springs (Mechanism), Automobiles Starting devices Design and construction, Internal combustion engines Design and construction, Energy development, Design; mechanical engineering; IC engine; internal combustion; engine; spring starter; engine modeling

Rights Statement

Copyright © 2013, author

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