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Thesis (M.S.)—University of Nebraska—Lincoln, 1960. Department of Agricultural Engineering.


Copyright 1960, the author. Used by permission.


The objectives of this study: 1) to determine the theoretical effect of variations in the inlet air pressure and temperature on engine performance at less than full-power; and 2) to attempt to verify the theoretical effects by performance tests on a specific Diesel engine.

The problem analysis is presented in three sections.The first section presents the normal operating temperatures of a Diesel engine at both full and less than full-power.The second section includes an analysis of effects of increasing the inlet air temperature under conditions where less than full-power is used.Finally, the effects of reduced inlet pressure on low-power operation are analyzed in section three.

The engine used in this analysis is a one-cylinder engine operating on the four-stroke cycle.The bore and stroke are 3 1/8 and 3 3/4 inches respectively.The piston displacement is 28.7 cubic inches and the compression ratio is 15:1.The manufacturer’s rated engine speed is 1800 rpm and is governor controlled.The connecting rod length is 7 9/16 inches.

The following conclusions are based on the results from the Diesel engine used for this study:

  1. The rates of combustion pressure rise of consecutive cycles vary considerably. The rates of pressure rise need to be qualified and will require special techniques for analysis if they are to have any significance.

  2. Heating the inlet air 100°F reduced ignition delay at constant power output as much as four degrees of crankshaft rotation.

  3. Decreasing the inlet air pressure two inches of mercury increased specific fuel consumption 0.60 pound per horsepower-hour, exhaust temperature 350°F, and ignition delay eleven degrees of crankshaft rotation, but reduced the rate of pressure rise and audible detonation at constant power output of 0.30 horsepower.

Advisor: John J. Sulek