Further Results from the 1978 Fuel Economy Survey
Further analyses of the 1978 in-use fuel economy survey are presented. Effects of usage on 1978 model year cars are determined. The in-use fuel economies are then adjusted to standardize for usage. The adjusted fuel economies have lower variability and yield better relationships with metro-highway fuel economy ratings.
An Analysis of Ford Lease Fleet Fuel Economy Data Through 1986 Models
On-road fuel economy, given the variety of customer driving experiences, tends to be lower than that obtained under controlled laboratory conditions. Since the 1978 model year, Ford Motor Company (Ford) has been collecting and analyzing on-road fuel economy data from Ford vehicles leased to company employees for evaluation purposes. Based on data collected during the summer months, 1985-86 model passenger car on-road fuel economy was approximately 47% greater than that obtained with 1978 models. Also, on-road results continue to parallel laboratory values, remaining approximately 15% below the metro/highway value. City and highway fuel economy values are contained on a label affixed to all new cars. In 1985, the label values were adjusted to better represent the on-road customer fuel economy. An analysis of actual on-road results compared to the label values demonstrates that the adjustment factors are accomplishing the intended purpose.
Analysis of the stress wave effect during coal breakage by a high-pressure abrasive air jet
In view of the defects of borehole collapse, inhibition of gas desorption and migration of gas existing in hydraulic fracturing and other hydraulic permeability–increasing measures for soft coal seams with low-permeability technology is proposed for coal breakage by a high-pressure abrasive gas jet for relieving pressure and increasing permeability. The comparative analysis of gas jet flow field structure between convergent nozzle and Laval nozzle has been given by numerical simulation. For Laval nozzle, the expansion wave and compression wave alternate and move forward steadily in gas jet and vanish when potential core length reaches maximum. So, the Laval nozzle can form more stable flow filed structure of gas jet and avoid shock wave in gas jet. Furthermore, a high-speed camera is adopted to analyze the jet structure and verify the conclusion of numerical simulation. Based on thermodynamic theory, this article calculates and analyzes the critical local sound velocity and pressure generated from the stress wave during the process of coal breakage by the gas jet. Furthermore, experimental coal breakage by a high-pressure abrasive gas jet is carried out. The high-pressure abrasive gas jet impacts the coal body as a quasi-static load and a dynamic load and forms corrosion pits on the surface of the coal body. Penetrating cracks are formed within the coal in the pattern of the loaded stress wave which leads to coal breakage. The effects of porosity and permeability on the propagation of the stress wave in coal are analyzed by establishing the dispersion equation for the spread of the stress wave in coal. The results show that porosity has a significant effect on wave velocity and that the attenuation of the stress wave is intensified with an increase in porosity. Moreover, the stress wave attenuation is more obvious at high frequency. The effect of permeability on the wave velocity is not significant at low frequencies. In contrast, at high frequency and relatively low permeability, the wave velocity increases with the permeability, and the attenuation of the wave velocity initially increases and then decreases. When the permeability is greater than 10−11 m2, the wave velocity is not affected by the permeability. However, the stress wave is not attenuated.