The deicing fluid flow rate varies with different[url=http://www.zjautoparts.net/product/Main-Nozzle/]Main nozzle [/url]  systems and the type of ice present. Given a relatively clean system with few protuberances or irregularities in the carburetor air passage, the throttle at cruise power, 40°F carburetor-air temperature and at 4,000 pounds of air per hour, a deicing fluid flow of 1 ~ 2% of the airflow insures throttling and fuel evaporation ice is removed within approximately 5 minutes after initial application.

Fluid deicing investigation of a different configuration showed similar recovery times for conditions of icing-air temperature and fluid flows comparable to those used for the investigation of cruise-power conditions. For rated-power conditions with impact icing at 25°F, full recovery within 5 minutes could not be accomplished in the second configuration with fluid flows as high as 1% of the airflow. An investigation of a larger induction system showed that deicing-fluid flows in excess of 1% of the airflow were required to remove impact icing alone.

Alcohol vapor was a potential deicing agent. This method gave slow recoveries and part of its small success do to the release of latent heat to the air stream by the vapor when it condensed. An analytical method determined the theoretical minimum amount of alcohol required to prevent carburetor icing or to compare the merits of fluids of determent composition. This method considers a number of factors, including the amount of alcohol required to lower the freezing point of water to the minimum surface temperature existing in the system, the adiabatic temperature drop due to throttling, the kinetic rise in the surface boundary layer, and the cooling effect of the evaporation of the deicing fluid.

This method determines only the minimum rate of deicing fluid as perfect distribution of the fluid. British investigators have reported considerable success eliminating fuel-evaporation icing by injecting alcohol with the fuel at a rate of from 2 ~ 5 % of the fuel consumption rate. If alcohol is added to the fuel supply, it must be free of water to prevent separation of the alcohol and the fuel.

In general, a fluid deicing system is inadequate and unreliable as a sole means of ice protection, and is an emergency deicing method. The recoveries obtained with heated air are usually much faster than the recoveries obtained when using a deicing fluid. If a fluid deicing system is to be need, it should be carefully designed both to satisfy the particular ice-prevention requirements of the induction system in which it is to be installed and to minimize the potential hazard common to this system of protection.

Take precautions to insure positive shut-off of the alcohol system on engine shutdown to prevent accumulation of alcohol-vapor in the induction system. The results of many fluid deicing experiments indicate that the requirements of each individual induction system must be separately determined with particular scrutiny of the spray characteristics of the nozzles used and the distribution of the fluid. There are several chemicals available to deice aircraft carburetors. Most of these chemicals are mixtures of isopropyl alcohol and methyl alcohol. Some brands include additional chemicals in small amounts. These fluids remove the ice by lowering the freezing point of the water, melting the ice that has formed and preventing ice as long as the fluid is flowing. There is a limit to the amount of fluid available; thereby limiting the amount of time that it is useable, as determined by the flow rate and pressure.

Both hot air and fluid deicers were tested and compared on a typical air induction system.The study found that the liquid deicers all worked to varying degrees, and all were corrosive on aluminum. When compared to heated air, they were less effective at returning the airflow to normal. These simulated tests were in typical ice-producing conditions where the raw inlet air temperature and atmospheric pressure were controlled, and water spray simulated the moisture levels found under various conditions.

The test setup used a variety of equipment to provide normal cruise airflow through the carburetor, heat and cooling where needed, and special test apparatus for taking measurements at various locations. The induction system tested consisted of a simulated air scoop, a Holley 1375H carburetor, a carburetor adapter, and a Wright R-1820 G-200 supercharger rear section. The deicing fluid injection devices used included the standard Holley alcohol vent ring (Holley Part No. 2383), a modified Holley vent ring (Holley part No.3089, a set of four standard Army nozzles (part AN-4023 and AN-4024), and a set of modified Army nozzles which were similar to the standard nozzles except for larger exit orifices.

The deicing fluids tested were Solox D-isopropyl alcohol®, anhydrous ethyl alcohol, S.D. 30, Shellacol®, and I. In most of the tests, maintaining the carburetor-air temperature at 40°F while spraying free water into the air stream at a rate of 250 grams per minute produced refrigeration icing. Overall, the best liquid deicer was isopropyl alcohol injected through US Army standard deicer spray nozzles into the airstream about two inches above the carburetor intake. High altitude conditions compounded the ice problem, indicating the need for a new type of carburetor. Enter the"floatless carburetor" and the "pressure carburetor" specifically designed for this application.

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