EA001492B1 - Process for transformation of vapour energyinto mechanical energy - Google Patents

Abstract

1. A process for the transformation of vapour energy into mechanical energy comprising steam generating, feeding pressurized superheated steam to a steam-powered helical steam engine steam expansion with transformation of potential steam energy directly into mechanical energy, characterized in that prior to feeding of superheated steam to the helical steam engine water is injected into preheated steam at the rate of "D", as defined by the equation: D >= (i" i') Qs /[C(tS tO) + r], where i", i' - respectively represent the steam enthalpy in superheated and saturated form, provided that P-const, kcal/kg; Qs - rate of steam flow, kg/s; C - heat capacity of water, kcal/kg degree C; r - heat of evaporation, kcal/kg; tS - boiling temperature; tO -temperature of injected water prior to injection, the evaporation of the injected water causes the temperature of the superheated steam to drop to the level at which steam is transformed into a wet state. 2. The process according to claim 1, characterized in that prior to injecting water the initial overpressure of superheated steam is reduced to a pressure of 5 to 20 Atm, by passing it via a hydraulic friction. 3. The process according to claim 1, characterized in that after injecting water the initial overpressure of wet steam is reduced to a pressure of 5 to 20 Atm, by passing it via a hydraulic friction. 4. The process according to claim 1, characterized in that steam is injected into the helical steam engine by portions. 5. The process according to claim 1, characterized in that the water produced in the process of steam expansion in the helical steam engine is used as packing of clearances between friction parts of the engine blocking steam leakage.

Description

Technical field

The invention relates to power engineering, in particular, to methods for converting steam energy into mechanical energy in relation to a steam screw machine. The invention is intended for small-sized mobile thermal power plants, mainly low power - up to 6 MW.

A thermal power plant with a stationary steam boiler and a turbogenerator is known (see Soloviev, Yu.P. Design of heat supply plants for industrial enterprises, Moscow, 1968, p. 38). The method of converting steam energy used in it does not allow it to work on an acute pair of low pressure, equal to 5-20 atm. In addition, power plants of this type have large dimensions and weight.

There is also a method of converting steam energy into mechanical energy, which consists in generating steam, supplying superheated steam under pressure to a steam screw machine (FDA), expanding the steam by converting the potential energy of the steam directly into mechanical energy (8ϋ, USSR patent No. 1838632, 1993).

However, in the known method, superheated steam has a high temperature, which causes a large thermal expansion of PVM parts. Uneven heating of parts causes jamming of the rotors of the machine.

Disclosure of invention

The problem to which the invention is directed, is to develop a method for converting steam energy into mechanical energy, providing increased reliability and durability of the machine components and parts while increasing its efficiency. The technical result consists in the ability to control the temperature of superheated steam entering the steam screw machine, and to reduce the thermal expansion of nodes and parts of the FDA in the optimal range.

To achieve the above technical result in the known method of converting steam energy into mechanical energy, which consists in generating superheated steam, supplying superheated steam under pressure to a steam screw machine, expanding the steam with converting the potential energy of the steam directly into mechanical energy, before applying superheated steam to steam a screw machine is injected with superheated steam, the flow rate Ό of which is determined from the ratio

Ό> (ί - GShESA - ίο) + r], where ί, 1 'is the vapor enthalpy in the overheated and saturated state, respectively, provided Ρ-οοηκί, kcal / kg;

О ,, - steam consumption, kg / s;

C is the heat capacity of water, kcal / kg deg; g is the heat of vaporization, kcal / kg;

G is the boiling point;

ίο - temperature of water injected into steam before injection;

reduce the temperature of superheated steam due to evaporation of the injected water to a temperature at which the steam goes into a wet state.

In addition, before injecting portions of water, the initial excessive pressure of the superheated steam is reduced by passing it through the hydraulic resistance to a pressure value of 5-20 atm.

In addition, after injection, portions of water reduce the excessive pressure of wet steam by passing it through the hydraulic resistance to a pressure value of 5-20 atm.

In addition, steam is injected in portions into a steam screw machine.

In addition, the water generated during the expansion of steam in a steam screw machine is used as a sealant of the gaps between the rubbing parts of the machine on the path of steam leakage.

Brief Description of the Drawings

In FIG. 1 shows isotherms in the ί-8 diagram, characterizing changes in the state of steam during water injection;

in FIG. Figure 2 shows isobars in the ί-8 diagram, characterizing changes in the state of superheated steam when passing it through hydraulic resistance;

in FIG. Figure 3 shows isobars in the ί-8 diagram characterizing changes in the state of wet steam when it is passed through the hydraulic resistance.

The best embodiment of the invention

The method of converting steam energy into mechanical energy is intended for use in low-power thermal power plants, mainly up to 6 MW. Such power plants have a source of 1 sharp low-pressure steam equal to 5-20 atm. As source 1, a steam boiler can be used.

The initial and final state of steam (Fig. 1) are characterized by points 1 and 2, which are respectively in the areas of superheated and wet steam. Line 3 corresponds to the state of saturated steam and separates the regions of superheated and wet steam. The curves passing through points 1, 2 are isotherms, and ί1> ί2

In FIG. 2, 3 points of the initial 1 and final 2 state of the vapor are respectively in the region of superheated and wet steam and lie on different isobars, with Ρ1> Ρ2.

The claimed method is as follows. The source generates sharp steam with a pressure not exceeding 20 atm, an example of 3, P ₁ = 12 atm. Acute steam enters through the inlet windows in the FDA housing located at one end of the rotors. After filling the next helical groove between the teeth, steam is cut off, and with further rotation of the rotors in the groove, a volume expansion of the portion of steam occurs with a geometric degree of expansion ε, for example, equal to ε = 4. At the end of expansion of the vapor pressure in the FDA, the geometric degree of expansion is P _C = P | A '= 12/4 = 3 atm. When opening the exhaust channel of the FDA, the vapor pressure is released.

Before supplying superheated steam to a steam screw machine, water is injected into superheated steam, the flow rate Ό of which is determined from the relation

О> (ί - 1 ') rp / [С (1 ₈ - 1 _О ) + r], where ί, 1' is the vapor enthalpy in superheated and saturated state, respectively, under condition of R-SOI81, kcal / kg;

О ,, - steam consumption, kg / s;

C is the heat capacity of water, kcal / kg · deg; g is the heat of vaporization, kcal / kg;

I, is the boiling point;

1 _О - temperature of water injected into steam before injection.

When water is injected (Fig. 1) into superheated steam, the droplets begin to evaporate intensively. In this case, the vapor enthalpy decreases. The vapor from state 1 goes into state 4, corresponding to a saturated pair. The temperature of the steam decreases from ί ₁ to ί ₂ .

Unevaporated drops are distributed in the volume of steam, and its state is characterized by point 2, corresponding to a certain amount of unevaporated water in the steam. The presence of water in the steam favorably affects the operation of the FDA, contributes to an increase in its efficiency. Water in this FDA design acts as a sealant, since filling the gaps between the rotors and the FDA housing prevents steam leakage. The lower temperature of the wet steam compared with superheated does not cause a large thermal expansion of the FDA parts and does not lead to jamming of the rotors.

When using the inventive method, it should be noted that if the initial pressure of the superheated steam is too high, then lowering its temperature by injecting water to a saturation state and then to a wet state may not give a sufficient effect. In this case, it is necessary to reduce the pressure of the superheated (Fig. 2) or wet (Fig. 3) steam to a value determined from the range of 5-20 atm. This is achieved by passing a portion of water superheated before injecting into it or wet steam after injecting a portion of water into it through hydraulic resistance. In this case, the vapor pressure decreases, its enthalpy remains unchanged, and the entropy increases. Thus, the temperature of wet steam decreases, and superheated - remains unchanged.

We illustrate this method with the following example.

There is superheated steam at P = 1.5 MPa and a temperature of 1 = 250 ° C. The steam flow rate is 0 ,, = 3.6 t / h = 1 kg / s. In this steam jetted water with a temperature _of 1 = 80 ° C. According to existing dependencies for these parameters of steam ί = 698 kcal / kg; ί = 667 kcal / kg; g = 466 kcal / kg; ί, = 197 ° С, С = 1 kcal / kg

Then

Ό = {(698-667) kcal / kg · 1kg / s} / {1 kcal / kg · deg (197-80) deg + 466 kcal / kg} = 0.053 kg / s.

If you increase the amount of injected superheated water, then the excess water will heat up to a temperature - ί ,, however, its evaporation will not occur. Steam will go wet.

Industrial applicability

The invention meets the eligibility condition for industrial applicability, since it is feasible using existing means of production.

Application of the proposed technology for converting steam energy into mechanical energy in low-power thermal power plants with low weight and dimensions, provides increased efficiency, operational reliability and durability.

Claims (5)

CLAIM 1. A method of converting steam energy into mechanical energy, which consists in generating steam, supplying superheated steam under pressure to a steam screw machine, expanding steam with converting the potential energy of steam directly into mechanical energy, characterized in that before supplying superheated steam to a steam screw machine superheated steam inject water, the flow rate of which is determined from the ratio Ό> (ί - 1 ^ 0п / [С (1 ₈ - ίο) + g], where ί, 1 'is the vapor enthalpy, respectively, in superheated and saturated states, provided P-coy, kcal / kg; 0 „- steam consumption, kg / s; С - heat capacity of water, kcal / kkgrad; g is the heat of vaporization, kcal / kg; ί, is the boiling point; ίο is the temperature of the water injected into the steam before the injection; reduce the temperature of superheated steam due to evaporation of the injected water to a temperature at which the steam goes into a wet state. 2. The method according to p. 1, characterized in that before injecting a portion of water, reduce the initial excessive pressure of superheated steam by passing it through the hydraulic resistance to a pressure of 5-20 atm. 3. The method according to claim 1, characterized in that after injecting portions of water, the excessive pressure of the wet steam is reduced by passing it through the hydraulic resistance to a pressure of 5-20 atm. 4. The method according to claim 1, characterized in that the steam is injected into the steam screw machine in portions. 5. The method according to p. 1, characterized in that the water formed in the process of steam expansion in a steam screw machine is used as a seal of the gaps between the friction parts of the machine in the path of steam leaks.