Cold airflow experiments were conducted to investigate the aerodynamic field in a small-scale furnace of a down-fired pulverized-coal 300 MW(e) utility boiler arranged with direct flow split burners enriched by cyclones. By increasing the staged-air ratio, a deflected flow field appeared in the lower furnace; larger staged-air ratios produced larger deflections. Industrial-sized experiments on a full-scale boiler were also performed at different staged-air damper openings with measurements taken of gas temperatures in the burner region and near the right-side wall, wall heat fluxes, and gas components (O(2), CO, and NO(x)) in the near-wall region. Combustion was unstable at staged-air damper openings below 30%. For openings of 30% and 40%, late ignition of the pulverized coal developed and large differences arose in gas temperatures and heat fluxes between the regions near the front and rear walls. In conjunction, carbon content in the fly ash was high and boiler efficiency was low with high NO(x) emission above 1200 mg/m(3) (at 6% O(2) dry). For fully open dampers, differences in gas temperatures and heat fluxes, carbon in fly ash and NO(x) emission decreased yielding an increase in boiler efficiency. The optimal setting is fully open staged-air dampers.

No abstract

No abstract

Compared with traditional static Client/Server architecture, the P2P architecture is more suitable for anonymous communication systems because it is more flexible and can keep load balance better. However, in order to make the system usable and reliable, some system designs make tradeoffs between anonymity and performance such as reliability, latency and throughput. Tradeoffs are sometimes unavoidable in system design, but which tradeoffs are acceptable and which are not is very important for developers. This paper models the P2P anonymous communications and takes quantitative analysis of anonymity by information theory with entropy. Based on this analysis, it studies the effect of key system design strategies on anonymity in network architecture, routing and message relay, and measures which strategies should be used in anonymous communications and which are unreasonable. Some analysis results are contrary to our intuition. For example, it quantitatively concludes that in some cases the anonymity is not enhanced when the system scale increases, and too long an anonymous tunnel may not provide higher anonymity but lowers performance. These analysis results are valuable for developers of P2P anonymous communication systems.