Output Temperature Predictions of the Geothermal Heat Pump System Using an Improved Grey Prediction Model

Abstract

In high altitude regions, affected by low pressure and low temperature atmosphere, diesel knock is likely to be encountered in heavy-duty engines operating at low-speed and high-load conditions. Diesel knock is commonly measured through pressure transducers, while there is lack of direct evidence and visualization images, such that its fundamental formation mechanism is still unclear. In this study, optical experiments on the severe diesel knock with destructive pressure oscillations were investigated in an optical rapid compression machine. High-speed direct photography and simultaneous pressure acquisition were synchronically performed, and different injection pressure and ambient pressure conditions were considered. The results show that for the given ambient temperature and pressure, diesel knock becomes prevalent at higher injection pressures where fuel spray impingement is enhanced. For the given injection pressure satisfying spray impingement, knock intensity is increased as ambient pressure is decreased. Further analysis on visualization images shows diesel spray impingement leads to longer ignition delay time, by which near-wall autoignition and supersonic reaction front propagation are induced. Consequently, three distinguishing stages can be observed during diesel knock, i.e. ignition delay, reaction front propagation, and pressure oscillation. Both spray impingement and fuel evaporation processes are considered as the main influencing factors.

Prediction of Mine Dust Concentration Based on Grey Markov Model

“…It takes the grey system as the research object and makes scientific quantitative predictions for the prediction and control of the development of various grey systems. It is widely used in agriculture, industry, meteorology, and other fields [25,26].…”