US2717591A - Self powered space heater - Google Patents

Description

Sept. 13, 1955 c. F. BACHLE SELF POWERED SPACE HEATER 2 Sheets-Sheet l 1 INVENTOR. Y @r? FfiacZ/e 1 J 1 N 0 v V 4 \I f 44 X a 0 i 2 .4 -11 "1 S w 6 w HT/ m w m E I 3 E i as T lx ||L M u m m p 1955 c. F. BACHLE 2,717,591

SELF POWERED SPACE HEATER Filed Sept. 21, 1950 2 Sheets-Sheet 2 4 fair- .12 at} a INVEN TOR Unite States Patent SELF POWERED SPACE HEATER Carl F. Bachle, Grosse Pointe, Mich, assignor to Continental Aviation and Engineering Corporation, Dctroit, Mich, a corporation of Virginia Application September 21, 1950, Serial No. 186,090

2 Claims. (Cl. 126-110) This invention relates to a portable self-powered space heater and more particularly to one incorporating a gas turbine as the fundamental component thereof.

This problem of developing a reliable, light weight and compact self-powered space heater is one in which considerable attention has been given in the last few years, without obtaining the desired degree of portability and the quite essential requirement that they will start and operate satisfactorily under conditions of extreme cold. A recent attempt to produce a space heater, meeting the above requirements was based around the principle of the pulse jet type of engine and while they were proved outstanding from a portability standpoint, they were not regarded as wholly successful since characteristic high noise level of the resonator valves was very objectionable.

Other heaters were developed involving the use of a thermopile for producing the electric power required by the accessories. Models were constructed producing 40,000 B. t. u. per hour and they incorporated a thermopile generating 12 watts which were consumed by both a miniature circulating fan motor and a solenoid-operated impulse fuel pump. Such heaters have been unsatisfactory because of their low efficiency and their excessive use of critical materials.

Most types as developed up to date embody an auxiliary power plant to drive the accessories, and it has been proposed to only employ a gas turbine as an auxiliary power.

It is an object of the present invention to overcome the above difficulties by producing a portable, self-powered space heater of maximum efficiency, but which is compact, light in weight, which has excellent starting and operating characteristics, and which above all is reliable and capable of producing up to 400,000 B. t. u. per hour, and this has been accomplished utilizing a gas turbine which provides for unprecedented portability and superior low temperature starting characteristics and its ability to deliver 400,000 B. t. u. per hour at 40 F.

A further advantage is the use of a gas turbine in conjunction with an after-burner arrangement as a high capacity gun-type furnace burner, but which is relatively light in weight and very compact, having a general overall dimension of about 12 x 14 x 35 inches. The overall efficiency of this proposed unit is about 60 percent, and this eificiency is computed on the basis of usable heat discharged from the unit only and does not credit the unit with the power required by the circulating fan, lubricating and fuel oil pumps or the velocity energy of the flue gas.

It is the further object of the present invention to provide a portable light weight and compact space heater of maximum efiiciency adaptable for many military and civilian applications, operable under varying weather and atmospheric conditions, by providing an open cycle gas turbine housed within a casing in which a mass of external air is inducted and compressed, heated at a substantially constant pressure, adiabatically expanded back to the initial pressure and discharged.

The heating process is normally carried out within a combuster where fuel is injected and burned under pressure in an atmosphere of air three or four hundred percent in excess of stoichiometric proportion. Heat release rates well over 1,000,000 B. t. u.s per cubic foot per hour are not uncommon. It is this phenomenon, as much as any other characteristic of the gas turbine which accents its applicability to the problem of producing a high output heater while at the same time, preserving the element of portability.

By introducing a suitable heat exchanger in any of the hot gas circuits, circulating air can be made to extract and deliver apredetermined quantity of heat. T heoretically, the heat exchanger can be located in one or more of several locations, depending upon the simplicity desired and structural limitations. The efiiciency of the system as a heat producer is governed largely by the prescribed limitations of weight and size. Fundamentally, many combinations of basic components and heat exchanger locations will deliver a stipulated quantity of heat plus a small quantity of mechanical power. Therefore, since good thermal efiiciency, consistent with simplicity and small size, is an essential requisite, a few of the most satisfactory schemes are herein illustrated and described.

Calculations for the single point performance of these several schemes were made on the basis of several assumptions, in order to minimize development costs. These assumptions were used consistently in each case and although there is some possibility of minor discrepancies in the order of merit as determined by this method of approach, due to the individual rates of response of various cycles to changes in design parameters, the risk is minimized by taking the four best results rather than only one.

First, the output is taken as 400,000 B. t. u.s per hour or the amount of heat required to raise 6,670 pounds of dry air at F. to 320 F. This 250 temperature rise is accomplished at 10,000 feet of altitude and assumes a constant specific heat of 0.24 for the air.

Efficiency is defined as the ratio of the output (400,000 B. t. u.s per hour) to the product of pounds of fuel required per hour and the heating value of 18,700 B. t. u.s per pound. Net work extracted from the system in each case, as mechanical or electrical power, is treated separately and does not appear as output in the expression of efficiency, which is stated above at 60 percent.

Where combustion chamber gases are directed through a heat exchanger before entering a turbine, the gases are at a temperature of about 2000 F., but when delivered to the turbine first, the gas temperature is limited to about 1300 F. Pressure and mechanical losses in each circuit are negligible and heat exchangers are varied in effectiveness over a range of 10 to 55 percent in order to limit the heat output to the desired value while maintaining moderate physical dimensions. The compressor pressure ratios are about 3 to l, with an overall efiiciency of about 70 percent. Combustion efiiciency is about 95 percent with a fuel-air ratio of 0.02, and turbines have an overall efficiency of about percent.

For a more detailed understanding of this invention reference may be had to the accompanying drawings illustrating preferred embodiments of the invention, and in which Figure 1 is a front elevational view of the heater, with the lower portion ofthe housing broken away to show the power plant;

Fig. 2 is a plan view, looking down on Fig. 1, and partially broken away to show the hot air outlet;

Fig. 3 is a vertical sectional-elevational view of the heater, taken approximately on the planes indicated by the line 33 in Fig. 4, looking in the direction of the arrows;

Fig. 4 is a vertical sectional-elevational view, looking in the same direction as Fig. l, and taken approximately on the planes indicated by the line 4-4 in Fig. 3; and

Fig. is a schematic showing of the assembly.

The construction illustrated in Figs. 1 to 4 inclusive show a preferred embodiment of the invention similar to the schematic showing of Fig. 5 in which the exhaust from the turbine is directed through the heat exchanger.

This portable self-powered space heater is compact and comprises a casing 10, enclosing all component parts of the heater and is of a size enclosing a space of less than 6000 cubic inches. It is designed to put out a maximum of about 400,000 B. t. u.s per hour.

The casing is provided with an air inlet 11 and partitions which conduct the incoming air to a com pressor 12 and to a fan or blower 14. The outlet 15 of the compressor leads to a combuster 16 in which fuel is injected and burned with the compressed air. The relative high pressure gases produced in the combuster are led to the gas turbine 18 of conventional construction. The turbine 18 is mounted or otherwise secured on the shaft 19, the compressor 12 being directly driven by shaft 19. The fan or blower 14 is mounted on drive shaft 20 preferably positioned to extend cross-wise or substantially normal to shaft 19. The shaft 20 is drivingly connected with shaft 19 by means of reduction gearing 22 (see Fig. 4).

The exhaust from the turbine 18 is led to the tubes 24 bridging the air chamber 25 and thence out through the top of the heater casing. The fan or blower outlet is connected by duct 26 to the air chamber 25 of the heat exchanger E, and thus the clean air is forced over the hot exhaust tubes 24 and thence to the hot air exhaust 27 from where the heated air may be conducted as found desirable to various places which are to be heated. The unit may of course be located in a room or building and the hot air may be exhausted directly into the room to be heated.

The unit as constructed in accordance with the principles of the invention illustrated in the accompanying drawings has a total weight of approximately seventyfive pounds, and is preferably designed to stand upright, the compressor and turbine axes extending vertical and lengthwise of the generally rectangular casing 10. The cold air inlet and hot air outlet are preferably located in one or more side walls of the casing and burned gases are exhausted outwardly through the top wall of the casing. Thus the compressor and blower, the drive shafts therefor, the turbine, combuster and heat exchanger are mounted one above the other so that the unit occupies a minimum of floor space.

A clear understanding of the invention is shown in Fig. 5, schematically illustrating a preferred arrangement. Fig. 5 illustrates a very compact unit in which the gas turbine 18 exhausts into a heat exchanger E. The uncontaminated circulating air to be heated is passed through the chamber 25 of the heat exchanger, and

energy for driving the circulating air fan or blower 14 and all other accessories including the compressor 12 is derived from the energy produced by the turbine. This scheme is simple, uses few components and has an efficiency of about 60 percent.

If desired, a generator G (see Fig. 5) may be tied into the assembly, same to be operated by reason of a driving connection to the compressor drive shaft or to said blower drive shaft. This additional accessory may often be omitted from the assembly, but when included, it is obvious that it will require the use of some of the available energy produced by said combuster to drive same, thus reducing the amount of energy available for the heat exchanger.

It will be noted that in this construction, there is provided means for utilizing some of the available energy produced by the combuster to operate the compressor and blower, while the remainder of the energy is utilized to heat the circulating air. It will be apparent that various changes and modifications may be made herein without departing from the spirit of the invention or from the scope of the appended claims.

1 claim:

1. A self-powered space heater comprising a heat-energy producing combuster; a compressor having airconducting connections with said combuster for supplying compressed air directly thereto; a gas turbine disposed in vertical axial alinement with said compressor and operatively connected thereto to drive the same; a heat exchanger disposed above said turbine; a blower adjacent and driven by said turbine, and having airconducting connections with the heat exchanger whereby to circulate air therethrough; gas-conducting connections between the combuster and turbine, and between the turbine and heat exchanger, whereby the exhaust gases from the combuster will pass directly to the turbine to actuate the same, and thence to the heat exchanger to heat the air circulated therethrough by the blower; a casing enclosing all the aforementioned elements and having a cold air inlet communicating with the air intakes of the blower and the compressor, said casing also having separate outlets communicating respectively with the hot air and the exhaust gas outlets of the heat exchanger.

2. A self-powered portable space heater comprising a heat-energy producing combuster; a compressor having air-conducting connections with said combuster for supplying compressed air thereto; a gas turbine disposed in vertical axial alinement with said compressor and operatively connected thereto to drive the same; a vertically extending heat exchanger disposed above said turbine; a blower connected to and driven by said turbine, and having air-conducting connections with said heat exchanger for circulating air therethrough; gas-conducting connections between said combuster and turbine, and between the turbine and heat exchanger, whereby exhaust gases from the combuster will pass directly to the turbine to actuate the same, and thence to the heat exchanger to heat the air circulated therethrough by the blower; a vertical casing enclosing all the aforementioned elements, with the compressor, turbine and blower in the lower portion thereof, and the heat exchanger and combuster in its upper portion, a side Wall of said upper casing portion being provided with openings for admission of cold air into the casing and downward flow therein to the intakes of the compressor and the blower, and the front wall and top wall of said upper casing portion being each provided with an opening, such openings communicating respectively with the hot air outlet and the exhaust gas outlet of the heat exchanger.

References Cited in the file of this patent UNITED STATES PATENTS 2,068,111 Resek Jan. 19, 1937 2,364,935 Bandurski Dec. 12, 1944 2,395,416 McCollum Feb. 26, 1946 2,409,159 Singleton Oct. 8, 1946 2,414,828 McCollum Jan. 28, 1947 2,415,064 McCollum Jan. 28, 1947 2,554,228 Walker May 22, 1951

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