LT5969B - Regenerator with direct heat exchange for multi-cylinder stirling cycle device - Google Patents

Abstract

The device belongs to heat exchangers that are used to realise a regenerative Stirling cycle. In the simplest Stirling cycle devices having two working chambers, a regenerator on thermal energy storage is arranged in the channel with periodica1circulation of the working fluid. In multi-cylinder Stir1ingdevices, the working fluid channels with simultaneous circulation of the working fluid in opposite directions are grouping in the pairs. In each such pairs of channels, the direct heat exchangers are arranged, that form the heat exchange regenerators@(instead of regenerators with therma1 energy storage). The heat exchange regenerators may be used in the multi-cylinder Stirling cyc1edevices (with no less than two pairs of the working chambers) varied in structure and purpose.

Description

The direct heat exchanger regenerator of the Stirling multicylinder unit belongs to the heat exchange units used in the regenerative thermodynamic cycle heat machines (including Stirling engines and Stirling reverse cycle units - refrigerators, heat pumps, cryogenic apparatus).

State of the art

In 1816 Robert Stirling invented a closed-thermodynamic thermal engine for alternating two isochores and two isothermal processes. (such a thermodynamic cycle is named after the inventor). Soon, the inventor improved his engine by installing a regenerator that accumulates thermal energy that is released in one isochor process and used in another isochor process. The regeneration process takes place in an element of the appropriate heat capacity, the regenerator, which is arranged in the channel of the gas working agent, and the working agent is periodically circulated between different working volumes of the heat machine with different temperatures. The regenerator increases the thermodynamic efficiency of the cycle, which in the case of an ideal regenerator equates to the Karn cycle. Therefore, regenerative power is used in the Stirling cycle power plant.

Although heat capacity regenerators increase the efficiency of the Stirling cycle unit, their use has drawbacks as well: the regenerator causes resistance (pressure drop) to the circulating working agent, which worsens the thermodynamic cycle performance; the internal volume of the regenerator increases the unchanged (so-called harmful) volume as well as worsens cycle performance; the use of a regenerator of specific properties (high heat capacity, anisotropic heat conductivity, etc.) complicates the construction and makes the Stirling installation more expensive; moreover, such a regenerator returns only part of the thermal energy. Therefore, many inventions have been patented to improve the design and materials of heat capacity regenerators. For example, patents US 4429732, 07.02.1984, Regenerator structure for Stirling-cycle, reciprocating thermal machine; US 6474075, 05.11.2002 Regenerator for a Stirling cycle based system; US 6591609, 15.07.2003 Regenerator for a Stirling engine.

The first Stirling engine was a single-cylinder with two pistons mounted on it, whose periodic motions differed by a quarter of a period. Two separate cylinders with single-acting pistons are used Stirling devices (so-called alpha type) where the periodic motions of the pistons also differ by a quarter of the period. The most compact and sophisticated are the modern multi-cylinder Stirling units with four cylinders with double-acting pistons. A schematic diagram of such a device is shown in Figs. 1a, where the crankshaft mechanism provides the pistons with periodic movement that varies quarter by quarter. Other mechanisms are used to provide the pistons with similar (as a rule, quasi-sinusoidal) motion. Such a four-cylinder unit corresponds to a set of four two-cylinder alpha-type Stirling units.

There are known multicylindrical six-cylinder Stirling units: for example, U.S. Pat. No. 3,811,283, issued May 21, 1974, to a multi-cylinder Stirling gas engine with double-acting pistons. Although such a device looks even more compact, its angle of pendulum phase difference between adjacent pistons is not optimal (instead of the optimum quarter-period difference a sixth-period difference is obtained).

Also known are combinations of Stirling thermal machines and oscillating electrical machines, which provide a more optimal range of motion. For example, U.S. Pat. No. 7,134,279, Nov. 14, 2006, discloses the use of oscillating linear electric generators in a Stirling multicylinder, using a double acting thennodynamically resonant free-piston multicylinder Stirling system and method. Patente LT 5404, 2007.03.26 The use of swinging rotary electric machines with Stirling cycle equipment is envisaged for the free swinging piston thermal machine.

In each of the above (and known) cases of Stirling multicylinder units, a separate heat capacity regenerator (excluding the heater and cooler elements) is provided in the channel connecting each pair of working volumes, as shown in Figs. la. Therefore, such multicylindrical Stirling cycle devices have the disadvantages described above caused by these regenerators.

Also known are more sophisticated multi-cylinder (or multi-chamber) Stirling cycle devices using valves or other technical elements that create unidirectional fluxes of the working agent. In such cases, direct heat exchanger regenerators (sometimes referred to as recuperators) can be used instead of heat capacity regenerators, in which the thermal energy of one channel working agent is directly transferred to the working agent of another channel, the pre-core. The negative impact of these regenerators on the Stirling cycle unit may be significantly less than that of the thermal capacitors. An example of such a technical solution is found in patent FR 2935155, 22.08.2008, "Machines a piston rotatif annulaire trilobique avec cycles thennodynamiques de Stirling" (Thermodynamic Stirling Cycle Machines with Rotary Triple Piston). Regardless of the advantageous regenerator used, such a device with unidirectional working agent flow formation loses the essential advantage of traditional Stirling devices with a smooth structure (or without otherwise switchable working agent channels), but the used direct heat exchanger regenerator is the closest analog of the present invention.

The essence of the invention

The essence of the invention is that in a multicylindrical Stirling cycle device, the working agent channels connecting variable temperature working chambers are grouped in pairs so that in one pair the channels are simultaneously (synchronously) flowing in the opposite direction of the working agent fluxes. in a set of work cameras connected by these channels. Each such pair of ducts shall be provided with heat exchanger elements constituting direct heat exchanger regenerators, which are different in design and function from the heat capacity regenerators used in Stirling cycle units. Direct heat exchanger regenerators can achieve lower working agent flow resistance (lower pressure drop), lower fixed volume, lower longitudinal heat conductivity, simpler and less costly construction, while returning more of the thermal energy. This results in the technical result of a higher thermodynamic cycle efficiency, a more efficient multi-cylinder Stirling cycle device and its performance.

Brief description of the drawings

Figure 1a shows a schematic diagram of a conventional multi-cylinder (four-cylinder) Stirling cycle unit with heat capacity regenerators, and Figure 1b shows an analogue unit with grouped pair ducts including direct heat exchanger regenerators.

Figure 2 is a schematic diagram of a Stirling cycle unit design of a multi-chamber (multicylinder) free oscillating blade piston, wherein the blade pistons are directly connected to the rotors of a swinging electric machine and direct heat exchanger regenerators are provided between respective pairs of channels in the Stirling heat machine.

DETAILED DESCRIPTION OF THE INVENTION

The direct heat exchanger regenerators are installed in a multi-cylinder Stirling cycle unit, the conventional design of which is illustrated in FIG. 1a. the unit consists of four cylinders with double acting pistons forming eight variable volume working chambers 1 and T, 2 and 2 ', 3 and 3', 4 and 4 '(in four cylinders respectively). The phases of the periodic movement of successively numbered pistons differ by a quarter of the period, such periodic movement being created by a crankshaft mechanism (as shown in Fig. 1a) or by other means. A coupling passage for each pair of working chambers (1-2 ', 2-3', etc.) corresponding to an elementary alpha-type Stirling machine is provided with a heat capacity regenerator in which the working agent flux periodically changes direction.

By replacing conventional heat capacity regenerators with direct heat exchanger regenerators, the channels linking the above working chamber pairs are grouped as shown in Figs. 1b - The channels are derived from the same temperature working chambers, whose phase changes differ by half a period, forming one pair. In one group of channels, the working agent circulates in opposite directions during isochoric processes in the respective elementary Stirling machines, as shown by the arrows in Figs. 1b. By installing a heat exchanger element (i.e., a direct heat exchanger regenerator of any design) between these channels, the heat energy W _{r is} transferred between the channels during said isochore processes, thereby implementing a regenerative thermodynamic cycle. Briefly, FIG. The piston motion device 1b generates a difference in the phase of the quarterly periodic motion of the sequentially numbered pistons (as in Fig. 1a in the thermal machine).

Similarly, the direct heat exchanger regenerators are installed in a free-fluctuating blade piston piston in the Stirling cycle device shown in Fig. 2. Here, two sets of thermal machines 5 and 5 'operating with pivoting rotary electric machines 6 and 6' are used. In this way, eight variable-volume work chambers are formed (as in Fig. 1 in a linear piston heat machine). That's it

The Stirling Cycle unit and its direct heat exchanger regenerators operate in the same manner as Figs. 1b linear piston assembly.

Similarly to the cases described, heat exchanger regenerators may be installed in other designs of multi-cylinder Stirling cycle units with at least two pairs of work chambers.

The use of direct heat exchanger regenerators with the above mentioned advantages instead of heat capacity regenerators allows to achieve higher performance of the multi-cylinder Stirling cycle unit, simplify it, and reduce the cost of the unit. Such units can be used as motors (especially for cogeneration units supplying electric and thermal energy) as refrigerators, air conditioners, heat pumps, cryogenic apparatus.

Definition of the Invention

Claims (1)

Definition of the Invention 1. Multi-cylinder Stirling Cycle Direct Heat Exchanger regenerator installed in variable volume work chamber interconnecting channels, characterized in that the channels are derived from uniform temperature operating chambers with varying phase phases in pairs and heat exchanger elements between each group of channels; capable of transmitting thermal energy from a single-channel operating agent stream to another-channel operating agent stream. 1/1