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In 1951, the Cummins Engine Company, Inc. conducted investigations concerning the application of turbochargers to our high speed diesel engines. Although several serious limitations of an operational nature were found to exist, the potential appeared to be very promising. This present paper outlines and discusses the subsequent developments to remove or extend the limitations and summarizes the current status of our turbocharged high speed diesel engines. The achievements have resulted in our production release of a line of high speed turbocharged diesel engines which are today establishing an enviable record of performance and economy in highway operation.

Cavitation-erosion is a peculiar form of corrosion or pitting which occurs on the water side of Diesel engine cylinder liners, on hydraulic turbines, on centrifugal pumps and on high speed ship propellers causing extensive and costly damage. As a result it has been the subject of numerous investigations. Despite these studies its mechanism is still unknown although it has been established that the following factors affect the pitting rate of the metals: (a) Hardness, (b) Porosity and surface discontinuities, (c) Viscosity, temperature and molecular size of the contacting liquid, (d) Amplitude of vibration, and (e) the addition of corrosion inhibitors. Some recent experimental data which illustrates some of the above effects is included.

Even though friction brakes are very necessary, they have certain limitations as to heat capacity that is especially noticeable on hills, but is also a factor in congested fast moving traffic. A 45,000 lb tractor and semi will generate about 300 hp going down an 8% grade at about 45 mph and less than one third of this if taken up by windage, rolling, and engine friction. The brakes must get rid of the rest as heat. This is where a supplementary brake, or retarder, comes in. An eddy current retarder will not stop or hold a vehicle but it can dissipate a lot of heat and so save the wheel brakes for the emergency, and also eliminate “engine braking” and so reduce wear and tear on engine and transmission. Even with retarders, however, it is advisable to distribute the force over the principally loaded axles.

The ability of cars to handle higher volatility fuels has been increased steadily through the years, but use of power accessories makes further improvements more difficult. Air conditioners are of particular concern because large amounts of heat are added to the engine using condensers which interfere, per se, with the cooling system. The effects of air conditioners on fuel volatility requirements are of immediate concern in Texas because the market has been concentrated: about one third of units sold to date are in Texas. Sales are spiralling, however, and they will be of general interest soon: total sales to date, 260,000; 57,000 in 1954; 176,000 in 1955; predicted sales of 1.0 million per year by 1959. Tests on twelve air conditioned cars showed that car RVP limits were reduced 0.7 on the average when the units were operated.

Correlation between laboratory and engine test results is discussed for seven (7) MIL-L-7808 type synthetic gas turbine oils, of varying engine performance. Improved correlation of these test results is needed to guide researchers in development of new and improved oils and because of the high cost and time of engine testing. Many present laboratory tests fall in the “go-no go” category or are meaningless in regards to predicting engine performance. Generally, best correlation is obtained where tests are conducted under simulated engine operating conditions.

Two phases of the U. S. Naval Engineering Experiment Station's current investigation of cavitation erosion in diesel engine coolant systems are described. The first phase is concerned with accelerated cavitation tests as conducted with a magnetostriction apparatus. Various materials and test arrangements were included in the studies. The second phase of the investigation covered the measurement of cylinder liner and block vibration in diesel engines wherein cavitation erosion damage was known to exist. This analysis indicated that the principal source of vibrational energy in the area of cavitation damage was the resonant vibration of the cylinder liners as excited by the impacts of piston slap and cylinder firing pulses.