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Research Papers: Internal Combustion Engines

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

[+] Author and Article Information
Jason R. Blantin

Air Force Institute of Technology,
Wright-Patterson AFB, OH 45433
e-mail: Jason.Blantin.3@us.af.mil

Marc D. Polanka

Air Force Institute of Technology,
Wright-Patterson AFB, OH 45433
e-mail: Marc.Polanka@afit.edu

Joseph K. Ausserer

U.S. Air Force Test Pilot School,
Edwards AFB, CA 93523
e-mail: Joseph.Ausserer.2@us.af.mil

Paul J. Litke

Air Force Research Laboratory,
Wright-Patterson AFB, OH 45433
e-mail: Paul.Litke.3@us.af.mil

Jacob A. Baranski

Innovative Scientific Solutions, Inc.,
Dayton, OH 45459
e-mail: Jacob.Baranski.ctr@us.af.mil

Contributed by the IC Engine Division of ASME for publication in the JOURNAL OF ENGINEERING FOR GAS TURBINES AND POWER. Manuscript received September 27, 2017; final manuscript received December 1, 2017; published online April 24, 2018. Editor: David Wisler. This material is declared a work of the U.S. Government and is not subject to copyright protection in the United States. Approved for public release; distribution is unlimited.

J. Eng. Gas Turbines Power 140(7), 072803 (Apr 24, 2018) (10 pages) Paper No: GTP-17-1534; doi: 10.1115/1.4038881 History: Received September 27, 2017; Revised December 01, 2017

Efforts to improve the range and endurance of group 2 (10–25 kg), internal combustion engine (ICE) powered unmanned aerial vehicles (UAVs) have been underway for several years at Air Force Research Laboratory (AFRL). To obtain the desired performance improvements, research into improving the overall efficiency of the ICE powerplants is of great interest. The high specific energy of hydrocarbon fuels (13,000 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. Little information is available however for the efficiency of ICEs in the size range of interest (10–200 cm3 displacement volume) 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 potentially 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 was examined in the study. Fuel conversion efficiency ranged from 22.2% to 25.8% as engine speed was swept from 2000 to 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.

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References

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Figures

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Fig. 1

BMEP and overall engine efficiency at peak power for various ICE types and displacement volume. Adapted from Menon and Cadou [4] and modified by Ausserer [5]: (a) BMEP as a function of displacement volume and (b) efficiency at peak power as a function of displacement volume.

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Fig. 7

Honda GX120 equivalence ratio sweep energy balance: (a) overall energy in each pathway (kW) and (b) percentage of fuel energy in each pathway

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Fig. 8

IMEP (top) and CoV of IMEP (bottom) of GX120 from equivalence ratio sweep

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Fig. 9

Honda GX120 throttle sweep energy balance: (a) overall energy in each pathway (kW) and (b) percentage of fuel energy in each pathway

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Fig. 10

Combustion phasing and burn angles of throttle sweep: (a) combustion phasing of throttle sweep and (b) combustion duration burn angles for throttle sweep

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Fig. 3

Power curves of (a) Honda GX120 brake power versus engine speed and (b) Modellmotoren 3W-55i brake power versus engine speed engines across the manufacturer's recommended operation ranges [3]

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Fig. 6

BSFC of Honda GX120 four-stroke engine and 3W-55i two-stroke engine

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Fig. 11

Honda GX120 CA50 sweep energy balance: (a) overall energy in each pathway (kW) and (b) IMEP (top) and CoV of IMEP (bottom)

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Fig. 12

Combustion phasing and burn angles of CA50 sweep: (a) combustion phasing of CA50 sweep and (b) combustion duration burn angles for CA50 sweep

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Fig. 13

Honda GX120 cylinder head temperature sweep energy balance

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Fig. 4

Honda GX120 speed sweep energy balance: (a) overall energy in each pathway (kW) and (b) percentage of fuel energy in each pathway

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Fig. 5

3W-55i speed sweep energy balance: (a) 3W-55i percentage of fuel energy in each pathway and (b) 3W-55i percentage of fuel energy in each pathway with short circuiting removed

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