A new internal combustion engine configuration - opposed piston with crank offset

Malpress, Ray (2007) A new internal combustion engine configuration - opposed piston with crank offset. [USQ Project] (Unpublished)

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Abstract

[Abstract]: The performance of a new engine configuration is assessed. The engine type is unique – details of similar engines have not been found in the open literature. The primary goal of this new engine design is to improve engine efficiency. It consists of two opposed pistons in a single cylinder controlled by two synchronously timed crankshafts at opposite ends of the cylinder. It makes use of crank offset to create the required piston motion aimed at engine efficiency improvements through thermodynamic performance gains. In particular, the engine employs full expansion. It also features a greater rate of volume change after combustion than a conventional 4-stroke engine for the same crank speed. The engine is a piston ported, spark ignition petrol engine. Thermodynamic and friction modelling using Matlab predicted net efficiencies in the order of 38%. Solid modelling and Finite Element Analysis were employed to build a prototype engine. Several facets of the engine build process resulted in the prototype differing from the design specifications. The original Matlab model was used to recalculate the predicted engine performance based on the prototype specifications. Deficiencies and errors in the original Matlab model were revealed by testing of the prototype and the data obtained allowed the original Matlab model to be reviewed. Modelling parameters used in the Matlab model were subsequently reevaluated allowing the Matlab model to be adjusted to reflect the performance of the prototype. Some constructive results were obtained with regard to the performance of the Matlab model. To date the engine has not been able to ‘power’ itself. The engine has overwhelmingly high friction relative to the original Matlab model predictions. When motored, the engine can maintain a consistent burn and the thermodynamic cycle delivers about half the originally predicted torque, which ‘unloads’ the powering motor. This torque represents about 40% of the torque required to motor the engine as measured in the prototype testing. Future work could address the thermodynamic deficiencies and reduce friction, but the engine as designed and constructed shows little potential as a viable engine. However the Matlab model and thermodynamic cycle have positive attributes as quantified by the engine test. Minor changes to the model structure and appropriate specification of parameters determined from the prototype test allowed the model to accurately reflect the performance of the prototype. The main feature of the thermodynamic cycle, full expansion was confirmed by the model to produce the extra work predicted relative to a conventional cycle, thereby allowing for improved efficiency if that work was obtained without excessive addition friction losses. The Matlab model and thermodynamic cycle may have future applications.


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Item Type: USQ Project
Refereed: No
Item Status: Live Archive
Additional Information: Appendix files have been loaded as Zip Files. Note that some of these files, eg. Matlab files, are unable to be opened in Windows. The folder Matlab files contains the functional software version of the project Matlab engine simulation program, and the folder ProE files contains functional versions of the ProEngineer solid model files. Familiarity with ProEngineer will be necessary to view these models. 'groundedanimation' is the main assembly file and can be operated as a mechanism. The models were compiled in Pro/Engineer Wildfire.
Depositing User: epEditor USQ
Faculty / Department / School: Historic - Faculty of Engineering and Surveying - Department of Mechanical and Mechatronic Engineering
Date Deposited: 19 Jun 2008 01:34
Last Modified: 02 Jul 2013 23:03
Uncontrolled Keywords: internal internal combustion design
Fields of Research (FOR2008): 09 Engineering > 0902 Automotive Engineering > 090201 Automotive Combustion and Fuel Engineering (incl. Alternative/Renewable Fuels)
URI: http://eprints.usq.edu.au/id/eprint/4218

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