WO1986000592A1

WO1986000592A1 - A method for selecting and controlling the mixture ratio of water and glycol for deicing and anti-icing and an equipment for carrying it out

Info

Publication number: WO1986000592A1
Application number: PCT/FI1985/000061
Authority: WO
Inventors: Antti Kossila; Paavo Turtiainen; Timo Turunen; Lasse Jutila
Original assignee: Instrumentointi Oy; Finnair Oy
Priority date: 1984-07-06
Filing date: 1985-06-28
Publication date: 1986-01-30
Also published as: FI842720A; FI70842B; NO860819L; DK101286D0; EP0187838A1; FI70842C; DK101286A; FI842720A0

Abstract

The mixture ratio of water and glycol in the mixture of water and glycol for deicing and anti-icing of an aircraft is selected so, that the outdoors temperature and the temperature of the surface to be treated are measured, from these temperatures the lower one is selected and on basis of this temperature the mixture ratio is selected, the freezing point of which is in a predetermined manner dependent on the said lower temperature, the said ratio in the mixture is measured during the spraying of the mixture, the ratio measured is compared with the selected ratio and corrected to be the ratio selected.

Description

A METHOD FOR SELECTING AND CONTROLLING THE MIXTURE RATIO OF WATER AND GLYCOL FOR DEICING AND ANTI-ICING AND AN EQUIPMENT FOR CARRYING IT OUT

This invention relates to a method for selecting and controlling the mixture ratio of water and glycol in the mixture of water and glycol utilized for deicing and anti-icing the aircraft, whereby the mixture is sprayed to the surface of an aircraft and in which method the atmospheric temperature is measured and taken into account when selecting said ratio, the freezing point of said mixture being in a predetermined manner dependent on the said measured temperature, whereafter the mixture is mixed and sprayed onto the surface.

The ice, which in this application means also snow and hoarfrost, on the surface of an aircraft can be very detrimental to the performance, controllability and stability of the aircraft especially in the take off and therefore also detrimental to the safety. Especially harmfull the ice is in the front edge and on the upper surface of the wing as well as on the surfaces of the steering surfaces and between the steering surfaces and the fuselage of an aircraft. The ice can be also very dangerous in the air intake means of the engine.

In order to secure the safety during the take off an aircraft it is accordingly very important, that the surfaces of the aircraft are deiced and sufficiently anti-iced. Generally deicing is done with water, the temperature of which can be near the boiling point or with a mixture of water and a glycol, which usually is also hot. The stream of hot water or of the mixture of them is directed or sprayed onto the surfaces, and the ice is removed. After the deicing also anti-icing is done. The purpose of anti-icing is to prevent the ice-formation on the surfaces of an aircraft. Also this process is performed, with the spray of the hot mixture of water and a glycol.

In this application the glycol means ethylene and/or prophylene glycol liquids and the treatment means deicing and anti-icing.

The known method for selecting the mixture ratio of water and glycol for deicing and anti-icing are described for instance in the publication of Finnair OT-4370, November 1, 1983, in which the deicing and anti-icing of the aircrafts on the ground is described. The content of this publication is mainly based on the recommendations of the Association of European Airlines, which were in common accepted by its member airlines (Recommendations for deicing/anti-icing of aircraft on ground, second edition, September 1, 1983).

In example in accordance with the page 7 of the instructions of Finnair the outdoors temperature is devided in to the following temperature ranges: 0 - -7, -7 - -10, -10 - -14, -14 - -17, -17 - -20 and -20 - -25. The outdoors temperature is measured and the corresponding temperature range is selected.

For instance, if first deicing is done and thereafter anti-icing, the following instruction is given for selecting the mixture ratio for deicing: The freezing point of the mixture is allowed to exceed the outdoors temperature by max. 7°C. The following instruction is given for selecting the mixture ratio for anti-icing: The freezing point of the mixture must be not less than 10°C below the outdoors temperature. The freezing point means freezing temperature.

The above given temperatures 7°C and 10°C are margins, which make it certain, that the mixtures used for deicing and anti-icing will not freeze during the treatment nor after that.

One disadvantage of the method described hereinabove is the fact that it does not observe, the possibility, that the temperature of the surface, for instance of the wing, can be essentially lower than the outdoors temperature. The wing of a modern aircraft can be deemed to be a large fuel receiver. In case an aircraft sufficiently long flies at high altitude, in which the temperature is remarkable lower than the outdoors temperature on ground, the temperature of the fuel in the wing descends to the temperature of high altitude. When this aircraft has landed, the temperature of the wing remains long time below the outdoors temperature on ground. The corresponding situation can develop also when the fuel receiver in the wing is filled from the receiver on ground. Even this fuel can be very cold in case the outdoors temperature for a long time has been low. At the moment on tanking, however, the outdoors temperature can be remarkable higher. In this case the temperature of the wing is lower than the outdoors temperature. If now the mixture ratio for deicing and anti-icing is selected only on the basis of the outdoors temperature, the purpose of processes in question is not attained at and the flying safety is endangered.

In order to increase the safety of the known deicing and anti-icing methods, relatively large safety margins, 7°C and 10°C have been used when the mixture ratio are selected, as explained. above. This, however, results in higher cumption of glycol.

Another disadvantage of the known method is the discontinuous function, on the basis of which the mixture ratio is selected. This function describes the dependence of the freezing point allowed of the outdoors temperature stepwise or discontinuously. The outdoors temperature measured is frequently higher than the lower temperature of the temperature range, which includes the temperature measured. For safety reasons, however, the mixture ratio in accordance with the instruction is selected on the basis of the lower temperature of the pertinent temperature range. This results in unnecessary high share of glycol in the mixture of water and glycol. In the following the known equipment for deicing and anti-icing and its use is described:

In the deicing vehicle there is a water receiver and a glycol receiver. Both liquids can be heated for instance electrically. The water temperature is hold at about +90°C and the temperature of glycol at about +40°C. The temperature of the mixture will then be dependent on the mixture ratio. Both receivers are cσnne-cted with a conduit to the mixing valve. Between the mixing valve and the surface to be treated there is a pipe or a hose. From any of the above receivers the liquid can be pumped from the receiver to the mixing valve. With the mixing valve the flow rates of water and glycol can be regulated. The mixing valve is of conventional design, and it includes a turnable handle and a scale. The mixture ratio of water and glycol can be selected by turning the handle to a predetermined position on the scale. The mixture ratio has been selected in the manner described above. The mixture is applied, advantageously sprayed, onto the surface with a hose and nozzle in a conventional manner. As to the mixture ratio the worker can rely only to the position of the handle of the mixing valve and to the result of the treatment observed by him. The changes in the conditions, in other words all the factors, having effect to the mixture ratio and the result of the treatment are not sufficiently observed. The above described method results both in deicing and anti-icing in an uncertain result, which might be reason even forserious accidents. An object of this invention is to provide a more accurate method for selecting the mixture ratio of water and glycol for deicing and anti-icing of an aircraft.

An other object of the invention is to improve the flying safety.

Still another object of the invention is to economically utilize a glycol in the mixture of water and glycol.

According to the invention these objects are attained so, that also the temperature of the surface to be treated is measured, from the two measured temperatures the lower one is chosen and the said ratio is selected on the basis of it, the freezing point of this mixture being in a predetermined manner dependent on said lower temperature and that the said ratio in the mixture is measured during the spraying, the ratio measured is compared with the selected ratio and the ratio measured is corrected to correspond to the ratio selected.

The temperature of the surface can also be measured with the conventional temperature measuring instruments.

The background of the invention is the better understanding of different factors having effect on the temperature of such surfaces, which are near to the fuel receivers of an aircraft and also the understanding of the fact, that when selecting the mixture ratio of water and glycol both for deicing and anti-icing both the temperature of the surface to be treated and the outdoor temperature must be taken into account and that from these two temperatures the lower one is of decisive importance for selecting the mixture ratio. In this way the flying safety is essentially improved.

It was also understood that the temperature of the wing can also be higher than the outdoors temperature. This situation can develop for instance then, when the fuel is taken from an underground receiver. In this case the temperature of the fuel is about +4 - 6°C. At the same time the outdoors temperature can, however, be noticeably lower and, accordingly, also this must be taken into account.

By the method in accordance with the invention also the better accuracy in the selection of the mixture ratio is attained at. Due to the better accuracy the safety margin in the selection of the mixture ratio could be decreased from 10°C to 5°C. This means a noticeable saving in the consumption of glycol.

According to an advantageous embodiment of the invention the mixture ratio is selected on the basis of a continuous function describing the dependence of the freezing point of the mixture on the said lower temperature.

This results in very markable saving of glycol According to another advantageous embodiment of the invention is that the following functions are performed automatically according to a predetermined programme:

The said two temperatures are measured, the lower one is selected from them, on the basis of it the mixture ratio is selected for the said mixture, the freezing point of the mixture being in a predetermined manner dependent on said lower temperature, the mixture corresponding to the selected ratio is mixed, the mixture ratio is measured during the spraying of the mixture, the ratio measured is compared with the ratio selected and the ratio measured is corrected to correspond to .he ratio selected.

In this way one can always be sure that the fixture ratio is correct, which to the great extent increases the flying safety and maintains the economy of glycol in the mixture.

An object of the invention is also to provide an equipment for carrying out the invented method. Characteristic to this equipment is, that it comprises: A Means 1, 2 for measuring the atmospheric temperature and the surface temperature. B Means 3, 4 for measuring the real flow rates of glycol and water during the spraying. C Means 5, 6 for regulating th e real flow rates of the glycol and water. D A computer 7 comprising - means 8 for receiving and storing the atmospheric temperature and the temperature of the surface, - a programme 9 for selecting the mixture ratio for the mixture of water and glycol on the basis of said temperatures, - means for receiving and storing 10 the real flow rates of glycol and water from the measuring means 3, 4 of real flow rates, - a programme 11 for calculating the real mixture ratio of water and glycol, - a programme 12 for comparing the mixture ratio selected with the real mixture ratio, - a programme 13 for determining the data for correcting the real mixture ratio on the basis of said comparison, - means 14 for transferring said data to the means 5, 6 for regulating the real flow rates of glycol and water.

In the enclosed drawing one embodiment of the invented equipment is schematically shown. The equipment functions in the following way:

The outdoors temperature as well as the temperature of the surface of an aircraft are measured with temperature measuring instruments 1 and 2. The real flow rates of glycol and water are measured with the measuring equipments 3 and 4, which are located in the conduits. In the conduits there are also means 5 and 6, for instance valves, and their operating motors for regulating the flow rates of water and glycol.

The computer 7 receives and stores with the eq uipment 8 the data of the outdoors temperature and the temperature of the surface and selects on the basis of this information according to a predetermined programme 9 the mixture ratio of glycol and water. On the other hand the computer 8 receives and stores with the equipment 10 the data of the real flow rates of glycol and water and computes according to a predetermined programme 11 the real mixture ratio of glycol and water.

Further in the computer 7 there is a programme 12 according to which the computer 7 compares the real mixture ratio to the selected ratio and on the basis of this comparison according to the programme 13 determines the instructions for correcting the real mixture ratio. These instructions include at least the direction of the change and the spead of the change . With the equipment 13 the instructions for the correction are transferred to the operating means 5 and 6, which change the flow rates of glycol and/or water until the real mixture ratio corresponds to the mixture ratio selected. After the regulating points of the flow rates the flows of glycol and water are combined to a mixture, which then is used for deicing and anti-icing.

The equipment and programmes only mentioned in the above description are not closer described here, because they per se are known to the man skilled in the art.

The equipment according to the invention for selecting and controlling the mixture ratio of water and glycol for deicing

and anti-icing of an aircraft offers, when compared to the known equipment for the same purpose, an essential technical improvement, which decisively increases the flying safety.

Claims

Claims :

1. A method for selecting and controlling the mixture ratio of water and glycol in the mixture of water and glycol utilized for de-icing and anti-icing the aircraft, whereby the mixture is sprayed to the surface of an aircraft and in which method the atmospheric temperature is measured and taken into account when selecting said ratio, the freezing point of said mixture being in a predetermined manner dependent on the said measured temperature, whereafter the mixture is mixed and sprayed onto the surface, c h a r a c t e r i z e d in that also the temperature of the surface to be treated is measured, from the two measured temperatures the lower one is chosen and the said ratio is selected on the basis of it, the freezing point of this mixture being in a predetermined manner dependent o n said lower temperature and that the said ratio in the mixture is measured during the spraying, the ratio measured is compared with the selected ratio and the ratio measured is corrected to correspond to the ratio selected.

2. A method in accordance with claim 1, c h ar a c t e r i z e d in that the following functions are performed automatically according to a predetermined programme:

the said two temperatures are measured, the lower one is selected from them, on the basis of it the mixture ratio is selected for the mixture, the freezing point of the mixture being in a predetermined manner dependent on said lower temperature, the mixture corresponding to the selected ratio is mixed, the mixture ratio is measured during the spraying of the. mixture, the ratio measured is compared with the ratio selected and the ratio measured is corrected to correspond to the ratio selected.

3. An equipment to carry out the method as per claim 2 comprising:

A means (1, 2) for measuring the atmospheric temperature and the surface temperature,

means (3, 4) for measuring the real flow rates of glycol and water during the spraying,

means (5, 6) for regulating the real flow rates of the glycol and water,

a computer (7) comprising - means for receiving and storing (8) the atmospheric temperature and the temperature of the surface, - a programme (9) for selecting the mixture ratio for the mixture of water and glycol on the basis of said temperatures, - means for receiving and storing (10) the real flow rates of glycol and water from the measuring means (3, 4) of real flow rates - a programme (11) for calculating the real mixture ratio of water and glycol, - a programme (12) for comparing the mixture ratio selected with the real mixture ratio, - a programme (13) for determining the data for correcting the real mixture ratio on the basis of said comparison, - means (14) for transferring raid data to the means (5, 6) for regulating the real flow rates of glycol and water.