RU2065065C1 - Ac power generation process - Google Patents

Abstract

FIELD: power engineering; power generation by using gas-turbine engines. SUBSTANCE: in AC power generation process, torque is applied to electric generator from one of double-shaft gas-turbine engines and, in addition, from its other shaft; these torques are summed up through differential reduction unit. Relationship between reduction unit output shaft speed and speeds of engine shafts is given in description of invention. EFFECT: improved reliability of power supply. 2 dwg

Description

 The invention relates to the field of electric power, in particular to methods for generating alternating current, and can be used on board an aircraft.

 A technical solution is known [1] In this solution, the rotors of the electric generators are rotated by supplying torque through the gearboxes from the shafts of the gas turbine engines of a single gas turbine installation. The above system allows the economical use of energy supplied to a gas turbine plant to generate electricity.

 The disadvantage of the system is the low quality of electricity, in particular the instability of the frequency of the generated voltage and the voltage level when changing the operating modes of a gas turbine installation in a wide range. To ensure the required quality of electricity in this system, two separate independent servo systems for maintaining the speed of electric generators when changing the operating modes of a gas turbine installation are required.

 The problem to which the invention is directed, is to improve the quality of electricity generation, the technical result achieved by narrowing the range of variation of the frequency of the generated voltage.

This is achieved by the fact that the proposed method of generating alternating current by rotating the rotor of the electric generator by supplying torque from one of the shafts of a twin-shaft gas turbine engine. Moreover, in addition to the rotor of the electric generator, torque is supplied from the second motor shaft, and the torques from the motor shafts are summed through a differential gearbox. The speed of the output shaft of the gearbox is maintained in accordance with the formula N _o. (N _input. 1 N _input. 2), where N _input. 1 N _in. 2 rotational speeds of the first and second input shafts, respectively, i gear ratio of the gearbox. This coefficient is determined by the formula i = Nc / ΔNav, where N _{c is the} specified average rotor speed of the generator, ΔNav = (ΔNmax + ΔNmin) / 2 is the average slip value of the engine shafts between the maximum (ΔNmax) and minimum (ΔNmin) slip of the shafts for various engine operating conditions.

 In FIG. 1 shows a system for implementing a method for generating alternating current.

 The alternating current generation system contains (see Fig. 1) a double-circuit gas turbine engine 1, which contains a high-pressure rotor RVD 2 and a low-pressure rotor RND 3, an alternating current generator G 4 and a differential gearbox DR 5. The output shaft DR is connected to the shaft alternating current generator, the first input shaft of the DR is connected to the shaft of the high-pressure rotor of the WFD 2, and the second input shaft of the DR is connected to the shaft of the low-pressure rotor of the WFD 3.

 The operation of the system is based on the phenomenon that is inherent in dual-circuit gas turbine engines, and is illustrated by the graphs in figure 2. At all operating modes of operation of such an engine (from light gas to take-off mode) in all operating conditions (from ground to cruising), the difference in the rotational speeds of the high and low pressure rotor does not change significantly. In FIG. 2, by way of example, graphs of changes in ΔN = Nin-Nnd over the entire operating range of engines and under various operating conditions for three double-circuit gas turbine engines are shown.

In FIG. 2 designations introduced:
"MG" small gas
"max cruise" maximum cruising
"nom." nominal
vzl. take-off
The solid line indicates the graphs corresponding to ground conditions (height H 0), the dashed line for cruising operation (height H 11.0 km, flight speed M 0.8). All graphs are based on data in an international standard atmosphere (ISA). The data for constructing the graphs is taken from the altitude and speed characteristics of the engines.

The system operates as follows (see Fig. 1). The rotation of the high-pressure rotor of the engine is transmitted to the first input shaft of the gearbox 5, and the rotation of the low-pressure rotor to the second input shaft of the gearbox 5. The differential gearbox subtracts the rotation frequencies of the first and second input shafts, while the speed of the output shaft of the gearbox, taking into account its own gear ratio, is Nout. = iΔN = (Nin.1 - Nin.2) i., where i is the gear ratio of gear 5, which is determined from the following conditions:
i = Nc / ΔNav;
where Nc is the specified average rotor speed of the generator rotor, providing a given frequency of the generated voltage. Further, ΔNav - the average value of ΔN ,, which is determined from the conditions (see figure 2):
ΔNav = (ΔNmax + ΔNmin) / 2
The output shaft of the gearbox 5 is connected to the shaft of the alternator 4 and the frequency of the generated voltage is proportional to ΔN. Since in all engine operating modes the change in ΔN is insignificant, the proposed system thus allows improving the quality of electric power by narrowing the range of variation of the frequency of the generated voltage. In addition, the use as an oscillator 4, for example, of an asynchronized synchronous generator, makes it possible to maintain the frequency of the generated voltage at a given level by adjusting the relative frequency of rotation of the field of excitation and the rotor of the generator using a static frequency converter (HFC). In this case, the range of variation of the frequency of the generated voltage is reduced to a value determined by the accuracy of the regulation system of the asynchronous synchronous generator.

 Thus, in comparison with the prototype, the proposed method allows to improve the quality of the generated electricity by narrowing the range of variation of the generated voltage. This, in turn, allows to reduce the mass of consumers of alternating current electricity on board the aircraft (transformers, induction motors, secondary power supplies, static frequency converters).

Claims (1)

The method of generating alternating current by rotating the rotor of the generator by supplying torque from one of the shafts of the twin-shaft gas turbine engine, characterized in that the torque from the second shaft of the engine is additionally supplied to the rotor of the generator, and the torques from the engine shafts are summed through a differential gearbox, the output shaft speed which is supported in accordance with the formula

where N _{input 1} , N _{input 2} speed, respectively, of the first and second input shaft of the gearbox;

gear ratio, determined by the formula

where N _{with a} given average frequency of rotation of the rotor of the generator,
ΔN _cf = (ΔN _max + ΔN _min ) / 2 the average value of the slip of the engine shafts between the maximum (ΔN _max ) and the minimum (ΔN _min ) slip of the shafts under various engine operating conditions.

Images