DE1049160B - Jet engine fuel and fuel - Google Patents

Description

The invention relates to prime movers of the type known as jet engines, their propulsion and the hydrocarbon fuel mixtures used therefor. In particular, the invention relates to improved hydrocarbon fuel mixtures for jet engines and their improved thereby Operation. In a very particular respect, the invention relates to improved propellants for ram nozzle machines.

Commonly there are three types of jet engines, namely turbo nozzles, ram nozzles and pulse nozzles. the the least complicated of these prime movers is the ram nozzle machine. While they are operating the Turbo nozzle is the same in terms of its duty cycle, the two machines differ in the compression levels. During compression for the turbo jet engine by means of a gas turbine driven Compressor is generated, which provides a flow of air to the combustion chamber with a desired at a regulated speed, the air flow through the combustion chamber of the ram nozzle machine regulated only by the speed of the ram nozzle machine moving through the air. Compression for the ram nozzle machine is caused by the ramming effect of the incoming air.

Heretofore, it was believed that operational difficulties arising with jet engines were primarily Line can be traced back to the machine design, and the greatest effort was devoted to development spent better designs for jet engines that overcome these difficulties could. Only recently, however, has it been found that not all hydrocarbons have the same properties in their use as fuel in jet engines and that they differ in their combustion properties differ enough to cause noticeable differences in the operation of jet engines.

One of the main goals in the development of ram nozzle machines is to provide a design create sufficient pressure to increase current airspeed. Other major goals are better fuel economy, with efficiency of fuel economy a Function of airspeed, and engine weight reduction. The thermal effectiveness of Ram jet machines operated at normal flight speeds is around 40%. Lower ignition temperatures and wide fuel-air ratios are highly for a fuel properties required to achieve these goals.

The invention relates to the composition of a jet engine fuel and igniter, which a higher percentage increase in thermal efficiency at the current airspeed

Jet engine fuel and ignition

Applicant:

Koppers Company, Inc.,
Pittsburgh, Pa. (V. St. A.)

Representative: Dr.-Ing. A. van der Werth, patent attorney,
Hamburg-Harburg 1, Wilstorfer Str. 32

Claimed priority:
V. St. v. America 7 June 1956

Ellsworth Elmer Kimmel, Pittsburgh, Pa. (V. St. Α.]
has been named as the inventor

speeds and greater pressures for a given engine design can develop, a lower ignition temperature a ^^ f, as well as under wide fuel-air limit ratios is usable and has a higher heat of combustion than fuels available now.

All research for fuel mixtures, which can give the optimum in engine performance, concerned additives whose properties in the combustion process firstly have a high heat of combustion and secondly high rate of flame and thirdly high density, fourthly low toxicity and fifthly low toxicity Possess volatility.

The jet engine fuel and igniter according to the invention is characterized in that it consists essentially of a normally liquid hydrocarbon and an aluminum alkyl of the formula
(R) ₁₁ AlH ,,,,,

where R is a hydrocarbon radical and η is an integer from 1 to 3.

Examples of such aluminum alkyls are trimethyl aluminum, dimethyl aluminum hydride, methyl aluminum dihydride, Triethyl aluminum, diethyl aluminum

hydride, ethyl aluminum dihydride, tributyl aluminum, Dibutyl aluminum hydride, butyl aluminum dihydride, triisobutyl aluminum, diisobutyl aluminum, isobutyl aluminum dihydride and higher homologous aluminum alkyls or their hydrides.

It has been found that the invention. Additives good igniters for hydrocarbon fuels, especially when using a jet engine. When used in this way, a small amount of the Aluminum alkyls into the combustion zone of the nozzle

809 730/137

injected where it meets a preheated, normally liquid hydrocarbon, what Ignition of the hydrocarbon caused. In addition to their usefulness for initial or cranking ignition aluminum alkyls can also be used to reignite the fuel when "blow out" or "cut" occurs.

In the first embodiment of the invention, the selected additive can be in the hydrocarbon fuel in an amount between about 5 to 30 percent by weight, preferably about 5 to 10 percent by weight, based on the weight of the fuel.

The fuel base consists of hydrocarbons, e.g. B. common mineral oil hydrocarbon jet engine fuels including kerosene and aviation fuel. In general, hydrocarbon fractions with boiling ranges from about 90 to 375 ° C can be used. A preferred fuel according to the invention consists of a hydrocarbon fraction with a boiling point between about 120 to 310 ^° C. which contains the mentioned proportions of aluminum alkyl.

The propellants according to the invention can be used in continuous jet machines as turbo nozzles, ram nozzles and pulse nozzles, in which a nebulization system is used to deliver the Fuel is used to the combustion chamber of the engine. In general, these machines are by injecting fuel and air into the combustion chamber of a jet engine in certain predetermined fuel-air ratios for ignition of the fuel to heat the air and the combustion gases, increasing the volume of the Gas mass is increased, which exits through the outlet zone of the jet engine. The exit of the gas mass from the rearwardly extending outlet conduit or nozzle opening occurs at a higher speed than the airspeed of the machine.

In order to demonstrate the advantages associated with the hydrocarbon fuel mixtures of the invention, tests were conducted to determine the temperatures at which the fuel mixtures self-ignite in air and the upper and lower limits of that required for combustion To determine the fuel-air ratio. The point at which combustion is no longer sustained is known as the blow-out or cut-out point. For comparison, the same tests were carried out with hydrocarbons without additives to show the advantages of the new mixtures.

To aid understanding, the following examples are presented for purposes of illustration and not limitation given. All parts and percentages are by weight unless otherwise specified.

Ignition tests example 1

Ignition tests were carried out with a fuel called JP 4 with no additive and with a 10 ° / ₀ by weight addition of triisobutylaluminum in JP fourth In the ignition tests, air was blown into a section of pipe approximately 250 cm in length with an internal diameter of approximately 36 cm. Gasoline was fed to this pipe section at a controlled flow rate and burned in the air stream to heat it. The air flow temperature was controlled by the amount of gasoline burned in the air flow. Hot gases from the preheating section were passed through another pipe section of the same length and diameter, which was equipped with a plurality of nozzles for injecting fuel. The nozzles were evenly distributed over a 15 cm length of this section. Adjacent to this section, the tube, about 36 cm in diameter, with a rectangular cross-section about 15 cm in diameter, was tapered over a piece of 30 cm with a single nozzle for injecting fuel during the ignition tests. From this section the gases were directed to another 36 cm internal diameter section ίο and then to the cooling section. The temperature of the air was gradually increased until ignition occurred. Proof of ignition was a blue flame on the injector. The following results were obtained:

fuel

JP4

JP4 with 10% triisobutylaluminum in JP 4

Ignition temperature

did not ignite at 1000 ⁰ C 425 to 525 ⁰ C

The foregoing is clear evidence of the substantial improvement in ignition conditions than immediate Result of using additives according to the invention. In particular, the drop lies in the ignition temperature on the order of 425 to 525 ° C.

Mixtures of alkyls having from 5 to 30 weight percent of various of the above-mentioned aluminum, such as triethylaluminum, Diisobutylaluminiummonohydrid and Diäthylaluminiumhydrid, ignition temperatures results in substantially less than 1000 ⁰ C. From these relevant results it is apparent that other aluminum alkyls and hydrides may be advantageously used for lowering Kohlenwasserstoffzündtemperaturen. Triethyl aluminum, diethyl aluminum monohydride, triisobutyl aluminum and diisobutyl aluminum monohydride have also been found to be very effective for this purpose.

Combustion tests example 2

In the rectangular part of the device described in Example 1, flame stabilizers from the Combustion tests used type used. The purpose of these exams was the upper and lower To determine limits of the fuel-air ratio, outside of which a combustion or Flame cannot be entertained. The air speed was about 60 m per second and they was preheated to about 525 ° C. To determine the lower limit, having a steady flame itself the fuel feed rate was reduced over a period of 10 to 15 seconds until the Flame went out. To determine the upper limit, the fuel feed rate was increased to the flame went out. The following table shows the results of the combustion tests.

fuel

JP4

10 ° / ₀ triisobutylaluminum in

J ^P4 '■■■

10 ° / ₀ triethylaluminum in

JP4:

Fuel flow l / hour

lower mixture

upper mixture

190 230 230

530 to 550. 625 700

In the previous combustion tests, the given fuel flows are those in which

blew out the flame. Any given value is the average of three to four determinations.

In additional combustion tests, mixtures of JP 4 in 10 and 20% triethylaluminum in a 5 cm diameter atomizing fuel combustion chamber. In any case, they burned Mixes when the pure fuel ran out.

The foregoing ignition and combustion test results make it clear that the fuel mixtures the invention have significantly lower ignition temperatures than the same fuel without additive and that the low ignition temperature is also an indication of superior combustion properties.

While an air speed of around 60 m / second was used, further tests have shown that a higher air speed of about 150 to 180 m / second gives even better results.

The foregoing also clearly illustrates that by using aluminum alkyls in hydrocarbon fuels according to the invention an extension of the upper fuel ratio is obtained, which is equivalent to the greater pressure obtained for a given engine design. The print size is proportional the amount of fuel that can be consumed per unit of time. Extension of the upper height of the fuel ratio without blowing out the flame leads to higher pressure. In the same way is ahead to see that for a given engine, addition of aluminum alkyl to the hydrocarbon will cause greater flight altitudes enables, as a result of, the expansion of the upper fuel ratio.

The aluminum alkyls are also very useful for the initial or cranking ignition or for the Reignition after a blowout. Considered excellent during ignition times of about 0.02 seconds each of the aluminum alkyls tested in accordance with the invention gave ignition times of about 0.01 seconds. Special aluminum alkyls which have given reduced ignition times include triethylaluminum, Triisobutyl aluminum, diethyl aluminum hydride and diisobutyl aluminum hydride. These exams ίο were carried out under normal operating conditions, whereby a small amount of the igniter was inserted into the combustion zone of a machine which preheated it Contained fuel-air mixture and the combustion time was recorded.

Claims (3)

Patent claims: 1. Jet engine fuel and igniter, characterized in that it consists essentially of a normally liquid hydrocarbon and an aluminum alkyl of the formula (R) “A1H ₃ _ _M , where R is a hydrocarbon radical and η is an integer from 1 to 3 , consists. 2. Jet engine fuel and igniter according to claim 1, characterized in that the aluminum alkyl Triisobutyl aluminum, diisobutyl aluminum monohydride, triethyl aluminum, diethyl aluminum monohydride or trimethylaluminum. 3. Jet engine fuel and igniter according to claim 1 and 2, characterized by a content of aluminum alkyl in amounts of 5 to 30 percent by weight based on the weight of the fuel.