Energy Balance and Power Loss Pathway Study of a 120cc Four-Stroke Internal Combustion Engine

[+] Author and Article Information
Jason R. Blantin

Air Force Institute of Technology, Wright-Patterson AFB, OH 45433

Marc D. Polanka

Air Force Institute of Technology, Wright-Patterson AFB, OH 45433

Joseph K. Ausserer

U.S. Air Force Test Pilot School, Edwards AFB, CA, 93523

Paul J. Litke

Air Force Research Laboratory, Wright-Patterson AFB, OH, 45433

Jacob A. Baranski

Innovative Scientific Solutions, Inc., Dayton, OH, 45459

1Corresponding author.

ASME doi:10.1115/1.4038881 History: Received September 27, 2017; Revised December 01, 2017


The high specific energy of hydrocarbon fuels (13000 W.h /kg for gasoline), but low fuel conversion efficiency for small ICEs means that relatively minor improvements in the fuel conversion efficiency of the engines can yield large improvements in range and endurance. More information is needed to quantify the efficiency of ICEs in the size range of interest for Group 2 UAVs. Most of the currently available efficiency data for 10-200 cm3 ICEs is for two-stroke engines. The goal of this study was to provide an in-depth probe of the efficiency and energy losses of a small displacement four-stroke engine which could be used to power a Group 2 UAV. Energy balances were performed on a Honda GX120 four-stroke engine using empirical research methods. The engine was a 118 cm3 displacement, single cylinder ICE. Energy pathways were characterized as a percentage of the total chemical energy available in the fuel. Energy pathways were characterized into four categories: brake power, cooling load, exhaust sensible enthalpy and incomplete combustion. The effect of five operating parameters were examined in the study. Fuel conversion efficiency ranged from 22.2% to 25.8% as engine speed was swept from 2000 - 3600 RPM, from 20.8% to 27.3% as equivalence ratio was swept from 0.85 to 1.25, and from 15.7% to 24.9% as throttle was swept from 28.5% to 100%. Combustion phasing and cylinder head temperature sweeps showed only minor changes in fuel conversion efficiency.

Section 4: U. S. Gov Employees
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