Cold Start Conditions Research Articles

Water-promoted oxidation of carbon monoxide over tin(IV) oxide-supported palladium

CATALYTIC oxidation of CO, both by O2 and by nitrogen oxides (NOx), is of considerable relevance to the removal of toxic CO and/or NOx from exhaust gases. Certain applications such as automobile exhaust control in cold-start conditions, and the removal of CO from tobacco smoke by use of a catalytic filter, demand not only catalytic activity at moderately low temperatures, but also effectiveness in the presence of water vapour. The low-temperature activities of most catalysts are at best (for example precious metals) partially destroyed, or at worst (for example base metal oxides) totally destroyed by poisoning due to water vapour. The results presented here demonstrate that, not only is the low-temperature activity of the Pd–SnO2 system not poisoned by water vapour, but rather its presence causes a marked enhancement in activity for the oxidation of CO both by O2 and by NO.

Electrical demand due to on/off thermostatically controlled loads

The integrated demand due to a group of similar on/off loads, each switched by thermostat, e.g. electric space heaters, is obtained as a function of the load-cycle time and the electricity authority's registration period. Staggered switching from the cold-start condition must be adopted so that the maximum demand is determined by the steady-state cycling conditions. Subsequent demand perturbations due to failure of individual processes may be insignificant, although demand control will be necessary for the introduction of large blocks of power to the load. The variance of the demand may be decreased by a reduction of the cycle time, thus leading to closer demand control, and hence to economies in the maximum-demand tariff.

Some Investigations on Cold-Starting Phenomena in Diesel Engines

In this paper are recorded the findings on the more fundamental aspects of cold-starting work carried out in the laboratory at Acton during the past three years. It deals with both the criteria of an ignition under cold-starting conditions and how these criteria may be met by some practical forms of starting aid. From available ignition delay data and measured compression temperature it has been possible to correlate, in order of magnitude, the variation of starting time with both cranking speed and ambient temperature. The increase in compression temperature and pressure during continuous cranking with fuelling is found to be due partly to sealing action of the injected fuel and partly to the increased compression ratio. The effect of the slow oxidation of the fuel carried over from the previous cycle has been investigated and found to be insignificant. From these basic considerations, the effects of engine design and operating variables on cold starting have been discussed. The principles and limitation of intake air heating as a starting aid (both by burner as well as by electrical heating), heater plug, and heating the injected fuel have been investigated. For the engine used, the lowering of minimum starting temperature is about 20°C (for a fixed cranking speed) when using a burner aid, while a further reduction of 2° to 3°C may be expected if electric heating is used. It is found that the main function of a heater plug is to provide a high-temperature ignition source rather than a heat source. The failure of the fuel heating system is due to excessive heat loss both before the fuel enters the chamber and to the chamber wall due to impingement when it enters the chamber.