Spyros I. Tseregounis

Comparison between Theoretical Calculations and Oil Film Thickness Measurements Using the Total Capacitance Method for Crankshaft Bearings in a Firing Engine

Comparisons were made between theoretical calculations and experimental measurements for minimum bearing oil film thickness (MBOFT) in main and connecting rod bearings of a typical automotive V6 engine running at 1500 rpm under three load conditions (64, 128, and 192 Nm.). Data for five oils (SAE grades 5W–20, 20W–20, 5W–30, 10W–30, and 20W–50) were obtained for the main bearing and for two oils (SAE 5W–30 and 10W–30) for the connecting-rod bearing. The theoretical calculations were done using the FLARE computer code while the measurements were made using the total capacitance method (TCM). Considering the complexities involved in a firing engine, overall, reasonably good agreement between theory and experiment was observed, especially for the absolute minimum of the MBOFT (MBOFTmin). The experimental data showed higher dependence on the Sommerfeld number than that of the theoretical calculations for the main bearing. The shapes of the MBOFT vs. crank angle curves were also similar between theoretical predictions and experimental measurements, although there were differences as well. Several causes of discrepancy affecting both the calculations and the measurements were investigated. Bearing non-circularity, cavitation, and crankshaft flexibility and dynamics were identified to be the main causes of the discrepancy. A novel approach based on analysis was developed for estimating the error in the based on analysis was developed for estimating the error in the oil film thickness measurements using TCM due to cavitation and bearing non-circularity, including the presence of holes and grooves. Presented at the 54th Annual Meeting Las Vegas, Nevada May 23–27, 1999

Wear and Galling of 356-T6 Aluminum-on-Steel in Low Amplitude Reciprocating Sliding in the Presence of Synthetic Lubricants in HFC-134a Atmosphere

The wear and galling of 356-T6 aluminum against steel in low amplitude reciprocating motion (5° oscillation) has been studied in a block-on-ring wear test machine. The lest utilized stepwise increasing loads (9-454 kg range) lubricants in CFC-12 or HFC-134a refrigerant atmospheres. For three lubricants utilized [a mineral oil (M100), a polyalkylene glycol (U8), and an esterified polypropylene oxide glycol (D1)] damage on the aluminum surface increased according to the sapience.: CFC-12/M100 < HFC-134a/M100 < HFC-134a/D1 < HFC-134a/U8 with the lowest wear and almost no galling for the CFC-12/M100 case and the highest wear and severe galling for the HFC-134a/U8 case. Formation of halide (mainly chloride) antiwear and FP films is responsible for protecting the aluminum surface in the CFC-12/M100 case. For the HFC-l34a/M100 case, the low solubility of HFC-134a in M100 (which prevents removal of the lubricant film from the surface) is most likely (although not observed directly in this work) responsible for lo...

Chemical effects of a polyglycol on brass surfaces as determined by XPS/depth profiling

Abstract Polyglycol compounds are compatible with alternative refrigerants which are replacing CFC-12 and thus are likely to be used for lubrication of automotive air-conditioning (A/C) compressors. A/C compressors may contain brass components which could be adversely affected by the polyglycol compounds. In this work, X-ray photoelectron spectroscopy (XPS) coupled with depth profiling with Ar + was used to investigate the effects of a polyglycol lubricant on brass. Oxidation of the lubricant at 150°C produces degradation products which preferentially remove Zn from the brass surface leaving behind a layer of soft, porous Cu, a corrosion phenomenon best known as brass dezincification. The soft Cu layer can wear off excessively in loaded sliding contacts thus producing early compressor failures. High-molecular-weight acids are the most likely candidates among the oil degradation products responsible for the attack on brass surfaces.