Accession Number:

ADA603432

Title:

Thermal Loss Determination for a Small Internal Combustion Engine

Descriptive Note:

Master's thesis

Corporate Author:

AIR FORCE INSTITUTE OF TECHNOLOGY WRIGHT-PATTERSON AFB OH GRADUATE SCHOOL OF ENGINEERING AND MANAGEMENT

Personal Author(s):

Report Date:

2014-03-27

Pagination or Media Count:

102.0

Abstract:

Three analysis techniques were used to measure the heat rejection of a 55 cc air-cooled two-stroke engine. This study was performed as part of a larger e ort aimed at extending range and endurance limitations of Group 1 2 Remotely Piloted Aircraft RPA. The engine selected for the study was a 55 cc gasoline-fueled, carbureted, spark-ignition engine made by 3W-Modellmotoren and is representative of RPA engines in these groups. With a surface area to volume ratio of 1.48 1 cm, the engine is in a size region where thermal losses begin to dominate engine e ciency and thermal e ciencies of less than 20 are common. The rst measurement method was an energy balance between the fuel energy entering the system and the various avenues for energy to leave the system. The second method used an enclosure around the engine and measured the enthalpy increase of the air owing past the cooling ns. The third method used heat ux gauges placed on the cylinder head to measure the heat ux at those locations. The energy balance method estimated heat rejection at approximately 30-40 of the total fuel energy for full and partial power settings. As part of the energy balance method, the engines tested achieved a maximum thermal e ciency of 13.7 and a maximum brake power value of 2.9 kW. The engine enclosure method measured heat rejection values to be approximately 2 kW at full and partial power settings. This equates to 8-11 of the fuel energy at full power and 20-26 at a 25 power setting. The heat ux gauge method measured heat ux values of up to 33 kW m2 . Applying the heat ux values over the surface area of the cylinder resulted in 1.2-2.1 kW of heat loss. As a percent of total fuel energy this represents 7-13 at full power and 22-30 at a 25 power setting.

Subject Categories:

  • Thermodynamics
  • Combustion and Ignition

Distribution Statement:

APPROVED FOR PUBLIC RELEASE