Air motor for improved engine brake efficiency: design and preliminary experiments

Malpress, R. and Buttsworth, D. R. (2009) Air motor for improved engine brake efficiency: design and preliminary experiments. In: 3rd International Conference on Energy and Environment (ICEE 2009): Advancement Towards Global Sustainability, 7-8 Dec 2009, Malacca, Malaysia.


The brake efficiency of a throttled internal combustion engine is reduced at low load operation because of the engine work required to drop the intake manifold pressure. These throttling losses are experienced by all throttled engines operating at less than wide open throttle (WOT). By replacing the throttle plate with a suitable air motor, work can be recovered in an expansion process that reduces the induced air pressure to the same intake manifold pressure as the throttled engine. To maximize the benefits from coupling the air motor to the engine cycle, the air should be returned to a thermal state identical to that of the throttled case at some point prior to combustion. This might be achieved either: (i) prior to cylinder compression via regenerative heat transfer to the inducted air; or (ii) through cylinder compression at an increased compression ratio. The work generated by the Induction Air Motor (IAM) can be directly applied to the engine output thereby increasing the brake efficiency for the same indicated work. This paper reports on the performance of an IAM designed to reduce intake pressure of an engine for low load operation. Increased brake efficiency will be achieved. The IAM design specifications are explored using a numerical model including isentropic efficiency, friction and service life considerations. A prototype has been constructed and was bench tested at flows and pressures comparable to a throttled engine. These tests indicated that the modelled friction was lower than the friction measured during the experiments. From the experiments performed with the prototype, the net performance of an IAM will give efficiency improvements in excess of 5% for an equivalent throttled engine operating at loads in the range up to 10% of its WOT power.

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Item Type: Conference or Workshop Item (Commonwealth Reporting Category E) (Paper)
Refereed: Yes
Item Status: Live Archive
Additional Information: © 2009 IEEE. Personal use of this material is permitted. However, permission to print or republish this material for advertising or promotional purposes or for creating new collective works for resale or redistribution to servers or lists, or to reuse any copyrighted component of this work in other works must be obtained from the IEEE. TOC incorrect. Pagination is 128-135.
Faculty / Department / School: Historic - Faculty of Engineering and Surveying - Department of Mechanical and Mechatronic Engineering
Date Deposited: 05 Jan 2010 04:15
Last Modified: 23 Nov 2014 23:37
Uncontrolled Keywords: internal combustion engine; throttling losses; air motor; engine efficiency; induction air motor
Fields of Research : 09 Engineering > 0902 Automotive Engineering > 090203 Automotive Mechatronics
09 Engineering > 0902 Automotive Engineering > 090204 Automotive Safety Engineering
09 Engineering > 0913 Mechanical Engineering > 091307 Numerical Modelling and Mechanical Characterisation
Socio-Economic Objective: E Expanding Knowledge > 97 Expanding Knowledge > 970109 Expanding Knowledge in Engineering
Identification Number or DOI: 10.1109/ICEENVIRON.2009.5398658

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