BR102012013088A2 - COMBINED CYCLE ENGINE - Google Patents

Abstract

COMBINED CYCLE ENGINE. It is an internal combustion engine that combines the Otto or Diesel cycle with the Rankine cycle on the same device. The steam generated with the engine's own cooling thermal power and with the thermal power available in the exhaust gases is injected into the cylinders primarily in the flue gas expansion phase. Mass and energy balances of the Otto and Rankine cycle indicate that this procedure, of re-producing heat rejected by the system again in the thermodynamic cycle, provides fuel consumption gains of up to 36%. It also opens up the possibility of applying other technologies to further improve efficiency in relation to the cases presented, considerably reducing both thermal pollution and the emission of particulate and polluting gases by internal combustion engines.

Description

COMBINED CYCLE ENGINE

The present patent relates to the application of the combined cycle concept of thermoelectric power stations to internal combustion engines, combining the Otto / Diesel cycle with the Rankine cycle, with a view to improving thermal efficiency and consequently reducing fuel consumption.

Since the 1980s, the combined cycle concept in thermoelectric plants has been used with which fossil fuel has been burned in gas turbines with efficiency around 30%, and thermal waste, around 70%, has been used. used in steam generation to drive steam turbines. The previous 10 thermal plants based only on the Rankine cycle had an approximate efficiency of 35%, and with the combined cycle design have a thermal efficiency of up to 60%.

The use of the Otto and Diesel cycle combined with the Rankine steam cycle is made with a waste heat recovery system rejected by the exhaust gases to generate steam and use this steam as the driving fluid of a turbine. In the concept presented, the heat of the engine cooling system is also fully reused.

Messingger, EP0076885, proposed the injection of steam into the four-stroke engine, transformed into a six-stroke, four-stroke engine for the Otto or Diesel cycle, interspersed with two-stroke steam engine (steam injection and exhaust).

The combined cycle engine is an engine that combines the Otto or Diesel cycle with the Rankine cycle without the need for a turbine as in the Messinger design, but injections occur at the end of the second half (compression) and / or at the beginning of the third. time (combustion / expansion) at high pressure, and the engine remains 4 stroke.

The combined-cycle engine has the following advantages over the Messinger or multi-cylinder concept that dedicates one or more steam-only cycles:

1. There is no significant change from the combustion engine to the

combined cycle motor.

2. The dynamics of compression / expansion of the steam engine and the combustion engine are different. In the combined cycle engine, the Otto or Diesel cycle occurs simultaneously at the same control volume.

3. Possibility of increased compression ratio.

4. Possibility to preheat combustion air.

The power gain of the combined cycle motor depends on a number of factors. To illustrate the effects of these factors, two cases of mass and energy balance are presented: the Maria Fumaça Case, characterized by minimal modifications compared to conventional engines, and the Advanced Case 10, which shows the possibility of increasing performance with some improvements. . Both cases refer to a gasoline engine that develops 50 kW (70 HP), consuming 14.9 l / h of gasoline in the Otto cycle.

The Maria Fumaça Case is shown schematically in Figure 1, whose main equipment legend is:

1. Water reservoir

2. Feed water pump

3. Collector (similar to sealed cooling system vessel)

4. Recirculating water pump, the same as the recirculating water

cooling.

5. Cooling system discharge. Biphasic flow

condensate and steam

6. Condensate pump, not depend on natural circulation

7. Engine exhaust manifold with hot gases

8. Evaporator

9. Steam Discharge

10. Exhaust - Exhaust

11. Steam Injection

Replacement water is pumped from the reservoir, item 1 of fig. 1 for the suction circulating water pump, item 4 of fig. 1. The replacement flow that is equal to the injected steam flow, is much smaller than the cooling flow, and the feed water pump power, item 2 of fig. 1 is low. About 50% of the feed water flow rate is evaporated in the engine block and discharged, item 5 of fig. 1, in the collecting vessel, item 3 of fig. 1.

Approximately 50% of the feed water flow is pumped by the condensate pump, item 6 of fig. 1 for the evaporator, item 8 of fig. 1, which sends steam to the collecting vessel, item 9 of fig. 1. Item 10 of fig. 1 represents the exhaust from the flue gas exhaust plus steam.

In the mass and energy balance summarized in Table 1 below, it is shown that consumption of 14.9 l / h of gasoline produces a thermal power of 147.6 kW in the Otto cycle (row 1 column B of table 1). % are rejected by the radiator (line 2), 30% by the exhaust gases (line 3) and 6.1% by radiation and

motor block convection (line 5), leaving 33.9% which are transformed into shaft power (line 6).

In the combined cycle all the thermal power of the engine cooling is used to preheat the supply water and generate steam and therefore the values of row 2 columns DeE are zero.

In large thermoelectric plants, the loss of exhaust gases from

combustion represents less than 10% of combustion power. The typical value for the Otto cycle is 30% and for the Maria Fumaça case, 15% recovery was considered through a compact heat exchanger, and simple item 8 of fig. 1.

In combustion steam is generated which is considered as a component

of flue gas. Injected steam is treated separately from combustion steam for Rankine cycle energy and mass balance calculations. The steam from the manifold item 3 of fig. 1 is injected directly into the engine cylinders, item 11 of fig.1.

Figure 2 shows schematically the position of the piston in the 4-stroke engine.

times:

(a) end of admission,

b) compression,

c) Beginning of Expansion after ignition and,

d) Exhaustion

In position a) of fig. 2 shows the end of the intake when the air intake valve 1 is closed initiating compression; in b) shows the compression, in the end this process occurs the ignition; na c) the start of expansion, with steam injection through valve 2 (occurs after ignition and start of expansion). In position d) the flue gas and the injected vapor are discharged to the manifold, item 7 of figure 1, by valve 3 of fig. 2.

Row 3 of Table 1 shows that 22.1 kW of combustion power is

rejected by the flue gas.

The mass and energy balance of the Rankine cycle shows that the injected vapor discharge rejects 55.3 kW, 38% of the combustion power (row 4 of table 1) by the exhaust, item 10 of fig. 1.

The heat loss by convection and radiation was kept equal for both

cycles (line 5).

The shaft power of the combined cycle (row 6 column D) is determined by the sum of the power of the Otto cycle (row 6 column B) and that of the steam cycle (row 12) minus the loss of the Otto cycle (row 13) and the power of the feed water pump (line 14).

The thermal power absorbed in steam generation (line 10) is lower than the 45% rejected by the Otto cycle (30% of the radiator + 15% of the exhaust), because in the combined cycle part of this energy is transformed into shaft power.

The combined cycle steam generation thermal power is adjusted interactively so that the axle power plus the rejected power of the combined cycle engine is equal to the combustion power. This value plus the pumping power (line 15) is used to determine the Rankine cycle water / vapor flow rate (lines 17 to 20 column E).

Injected saturated steam (line 18) is mixed with the flue gas and overheated to 800 C (line 19 column C), removing heat from the Otto cycle (line 11). The temperature of 800 C was defined by the program limitation of determining the physical properties of steam according to IAPWS-IF97.

The shaft power of the steam cycle (line 12) is determined by the Rankine cycle mass and energy balance, lines 17 to 20. The power transferred from the flue gas to the steam overheat (line 11) is no longer converted to shaft power in the Otto cycle. The determination of this loss (line 13) is made conservatively considering the Otto cycle efficiency of 33.9%.

Table 1: - Maria Smoke Case Constant Consumption

Columns WABCDE Petrol consumption [l / h] 14.9 Otto cycle Combined cycle [kW] [%] [kW] [%] 1 Thermal power combustion 147.6 100% 147.6 100% 2 Radiator 44.3 30, 0% 0 0% 3 Exhaust combustion gas 44.3 30.0% 22.1 15% 4 Exhaust steam injected 55.3 38% other 9.0 6.1% 9.0 6.1 6.1% 6 Axle power 50.0 33.9% 61.1 41.4% 7 8 Steam Cycle and Otto 9 Cycle Effect [kW] Absorbed Thermal Power Injected Steam Generation 50.0 11 Super Absorbed Thermal Power steam heating 25.0 12 Mechanical power of steam cycle 19.7 13 Loss of Otto cycle 8.5 14 Feed water pump power (BAA) 0.146 Convergence criterion 0.000 Pot BAA 0.146 16 Temp pressure Enthalpy flow [ bar abs] [C] [kJ / kg] [kg / h] 17 feed water 40 25.0 108.5 67.1 18 injection steam 40 250.4 2800.9 67.1 19 steam in the cylinder 40 800 4142.5 67.1 Cylinder Steam Discharge 2.3 307 3086.5 67.1 The Maria Fumaça Case's steam cycle is as simple as possible, very similar to the old steam engines. Water at atmospheric pressure and at room temperature (row 17 column C of table 1 and item 1 of fig. 1) is pumped to 40 bar abs (row 17 column B of table 1) to generate saturated steam.

At a pressure of 40 bar abs, the saturated vapor temperature will be 250.4 C (row 18 column C of table 1), a temperature low enough to cool the engine block.

Cylinder discharge pressure (row 20 in Table 1) is the partial pressure of the injected vapor, determined as a function of the molar fraction of each exhaust gas component (CO2, combustion H2O, N2 and injected H2O).

In the Maria Fumaça case, there is no water recovery and gain in

engine power is 22% or as shown in table 2 below, for the same power, the combined cycle consumption is 18% lower compared to the Otto cycle.

This simple design of the combined-cycle engine with good efficiency has one major drawback: excessive water consumption, 67 l / h, ie 270 liters of water for a 4-hour autonomy, typical of “Maria Fumaças”. ”, Old trains run on coal or wood. Table 2: - Maria Smoke Case Constant Power

ABCDE Columns Petrol consumption [l / h] 14.9 12.2 Otto cycle Combined cycle [kW] [%] [kW] [%] 1 Thermal power combustion 147.6 100% 120.8 100% 2 Radiator 44 , 3 30.0% 0 3 Exhaust flue gas 44.3 30.0% 18.1 15% 4 Exhaust steam injected 45.3 38% other 9.0 6% 7.4 6% 6 Axle power 50, 0 33.9% 50.0 41.4% 7 8 Steam cycle and effect on Otto 9 cycle [kW] Thermal power absorbed injected steam generation 4 1.0 11 Absorbed thermal power Steam overheat 20.5 12 Mechanical power of steam cycle 16.1 13 Loss of Otto cycle 6.9 14 Feed water pump power (BAA) 0.119 Convergence criterion 0.000 Pot estimated BAA 0.119 16 Temp pressure Enthalpy flow [bar abs] [C] [kJ / kg] [kg / h] 17 feed water 40 25.0 108.5 54.9 Injection steam 40 250.4 2800.9 54, 9 19 Steam in the cylinder 40 800 4142,5 54.9 Discharge steam from the cylinder 2,3 307 3086,5 54.9 In fig. 3 shows the Advanced design schematically:

1. Condensate Collector

2. Feed water pump 1

3. Collector (similar to sealed cooling system vessel)

4. Recirculating water pump, the same as the recirculating water

cooling

5. Cooling system discharge. Biphasic flow

condensate and steam

6. Feed water pump 2

7. Engine exhaust manifold with hot gases

8. Steam generator (superheated steam evaporator)

9. Steam Discharge

10. Exhaust - Exhaust

11. Medium Steam Injection

12. Condenser (in radiator position)

13. Desuperheater

14. Preheater

15. Discarding excess condensate 16.0 high pressure vessel

17. High Steam Injection

The most important improvement over the Maria Fumaça case is the recovery of condensate.

The water tank is replaced by the condensate collector (item1 in fig. 3) and the function of the feed water pump 1 (item 2 in fig. 3) is the same as in the Maria Fumaça case. Collector (item 3 of fig. 3) now works at lower pressure as this vapor will be injected before ignition to inhibit self ignition and to decrease maximum temperature after ignition in order to minimize NOx generation.

Fig. 4 schematically shows the position of the piston in the 4 stroke engine with 4 valves per cylinder, valve 1 is the air intake, 2 medium steam injection, 3 high steam injection and 4 exhaustion:

a) End of admission, b) Compression,

c) Beginning of Expansion after ignition and,

d) Exhaustion

The pump 4 of fig. 3 continues with the circulating water function but

with less power. Just over 10% of the cooling heat is removed with this system to generate 10 kg / h of medium pressure steam.

The pump of item 6 of fig. 3 has the function of feed water pump, pumping the condensate through the cooling channels of the motor block, removing almost 90% of the cooling power. The condensate leaves the block and enters the steam generator (item 8 of fig. 3) for full evaporation and overheating and is then discharged into the high pressure vessel (item 16 of fig. 3).

The exhaust gas is routed through the manifold (item 7 of fig. 3) to the steam generator (item 8 of fig. 3), which in counter current generates overheated steam.

From the steam generator, the exhaust gas passes through the preheater (item

14 of fig. 3) by the desuperheater (item 13 of fig. 3), by the condenser (item 12 of fig. 3) to finally be discharged into the condensate tank (item 1 of fig. 3).

The vapor contained in the exhaust gas leaves the preheater (item 14 of Fig. 3) overheated, and the use of desuperheater is important for compacting the condenser (the higher condensation heat transfer coefficient).

To recover condensate, the exhaust gas must be

cooled below 100C by the air condenser.

From the condensate tank, the flue gas is released to the atmosphere. The condensate tank has a vent that discharges excess condensate (the combustion water) and a continuous purge from the bottom of the tank.

Tables 3 and 4 show the mass and energy balances of the advanced case. The power gain in the advanced case is 57%, from 70 HP Otto cycle to 106 HP1 or maintaining the power of 70 HP1 a 36% fuel economy.

In the presented calculations the following approximations were adopted:

1. Conservatively it was assumed that the loss of the Otto cycle is proportional to the power transferred to the steam, considering the nominal efficiency of the combustion cycle (33.9%).

2. Vapor temperature after mixing with flue gas: 800 C due to program limitation to determine the physical properties of vapor according to IAPWS-IF97.

3. During expansion, two volumes of thermally insulated controls were considered for flue gas and injected steam respectively.

4. The exhaust gas vapor was considered to leave the preheater at 150 ° C.

Combined-cycle motor efficiency can be increased over the advanced case by considering the following:

1. Minimize radiation and convection losses

2. Compression ratio change benefiting from medium pressure steam injection

3. Flue gas preheating also benefiting from medium pressure steam injection

The purpose of the high pressure of the main injection steam is to reduce the steam flow (lower heat rejection of the Rankine cycle) as well as to store a large amount of mechanical energy in the thermally insulated pressure vessel.

The pressure of the high-pressure steam system provides enough torque to move the car with the transmission in gear, a very important feature for traffic in large urban centers where car efficiency approaches zero (near-zero fuel burn).

In the combined-cycle engine, fuel burning would only be done to recover vapor pressure, preferably by pulling the car to use the efficiency of the Otto or Diesel cycle. With the car stopped combustion off and steam blocked, there will be no power consumption.

The pressure vessel system may also perform the function of the racing car booster, which is used to increase power for short periods.

Larger cycle engine exhaust discharge pressure

Combined due to steam injection is an important parameter for sizing steam generator and condenser, making equipment compact.

In combustion steam is generated which will be condensed together with the injected steam, and even with continuous purge, there will be no need for water replacement (only additive to protect the engine).

The pollutants contained in the condensate resulting from the flushing of the exhaust in the condensate manifold can be filtered off or concentrated in a liquid to be disposed using reverse osmosis technology.

The use of combined-cycle engines will significantly reduce fuel consumption and greatly impact on environmental protection by reducing thermal pollution as well as particulate emissions into the atmosphere.

25 CO 03

SZ ■

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1

2

3

4

5th

6th

7th

8th

9th

10

11

12

13

14th

15

16

17

18

19

20

21

22

23

24

25

26

12/13

Table 3: - Advanced Case Constant Consumption

Columns

THE

B

D

Petrol Consumption [l / h]

14.9

Otto cycle

Combined cycle

[kW]

[%]

[kW]

[%]

Thermal power combustion

147.6

100%

147.57

100%

Radiator

44.3

30.0%

0

Exhaust flue gas

44.3

30.0%

10.3

7%

Steam Injected Exhaust

49.8

34%

others

9.0

6%

9.0

6%

Shaft power

50.0

33.9%

78.4

53.1%

Steam cycle and effect on Otto cycle

[kW]

Thermal power absorbed injected steam generation

73.3

Thermal power absorbed steam overheating

17.4

Mechanical power of steam cycle

36.3

Loss of Otto Cycle

5.9

Feed Water Pump Power (BAA1)

0.37

Feed Water Pump Power (BAA2)

1.61

Convergence Criterion

0.000

Pot Vopor GV

1.560

Pressure [bar abs]

Temp

[Ç]

Enthalpy

[kJ / kg]

flow rate

[kg / h]

feed water

30

99.5

419

109.6

Condensed average

30

234

1,008

109.6

Medium Injected Steam

30

234

2,803

10.0

Average steam in cylinder

30

800

4,147

10.0

Average steam discharge

420

3,316

10.0

feed water

150

240

1,037

99.6

Steam injection

150

600

3,583

99.6

Steam in the cylinder

150

800

4,091

99.6

High steam discharge

3.8

201

2,864

99.6 Table 4: - Advanced Case Constant Power

ABCDE columns (/) Petrol consumption [l / h] 14.9 9.5 CO C Otto cycle Combined cycle [kW] [%] [kW] [%] 1 Thermal power combustion 147.6 100% 94.2 100 % 2 Radiator 44.3 30.0% 0 3 Exhaust combustion gas 44.3 30.0% 6.6 7% 4 Exhaust steam injected 31.8 34% other 9.0 6% 5.8 6% 6 Power 50.0 33.9% 50.0 33.9% 7 8 Steam cycle and effect on cycle Otto 9 [kW] Po Absorbed thermal power Injected steam generation 44.6 11 Absorbed thermal power Steam overheat 11.0 12 Mechanical steam cycle power 22.9 13 Loss of Otto cycle 3.7 14 Feed water pump power (BAA1) 0 .22 Feeding water pump power (BAA2) 0.88 16 Convergence criterion 0.000 Pot Vopor GV 1,082 17 Temp pressure Enthalpy flow [bar abs] [C] [kJ / kg] [kg / h] 18 feeding water 30 99.5 419 64.4 19 Average condensate 30 234 1,008 64.4 Average injected steam 30 234 2,803 10,0 21 Average steam in the cylinder 30 800 4,147 10,0 22 Discharge average steam 2 342 3,157 10, 0 23 feed water 150 240 1,037 54,4 24 Injection steam 150 600 3,583 54,4 Steam in the cylinder 150 800 4,091 54,4 26 High steam discharge 2,2 145 2,757 54,4

Claims (12)

1. COMBINED CYCLE ENGINE characterized by injections of steam generated with the waste heat recovery system (cooling, exhaust, radiation and convection engine) into the cylinder of the internal combustion engine itself; COMBINED CYCLE ENGINE according to claim 1, characterized by the generation of medium pressure steam (10 to 40 bar abs) and high pressure steam (above 40 bar abs) as required, medium pressure steam in the saturated condition with temperature between 180 and 250 C, overheated high pressure vapor; COMBINED CYCLE MOTOR according to claims 1 and 2, characterized in that the engine cooling system is used as a steam generator, that is, the engine block cooling channels as a heat exchanger; COMBINED CYCLE ENGINE according to claims 1 and 2, characterized by the injection of medium pressure steam at the end of compression before ignition in order to inhibit self ignition and formation of NOx after ignition, the vapor flow is used to control temperature before and after ignition; COMBINED CYCLE ENGINE according to claim 4, characterized by the use of medium pressure vapor flow to enable high compression ratio, compression ratio means the compression of the combustion air without considering the partial pressure of injected steam; COMBINED CYCLE ENGINE according to claim 4, characterized by the use of medium pressure steam flow to allow use of heated combustion air, the combustion air temperature must be as high as possible, but the combustion air ratio / fuel must not be smaller than the design; COMBINED CYCLE ENGINE according to claims 1 and 2, characterized by injection between the ignition and the expansion of high pressure steam in the cylinder, called motive steam, to provide the highest possible output; COMBINED CYCLE ENGINE according to claims 1 and 2, characterized by the injection of high-pressure steam called motive steam with sufficient flow and pressure to operate as a low-speed steam engine (up to 3000 rpm); COMBINED CYCLE ENGINE according to claims 1 and 2, characterized by the injection of high pressure steam called driving steam to provide sufficient torque to move a car without the aid of combustion; COMBINED CYCLE MOTOR according to claims 2, 7, 8 and 9 having heat insulated pressure vessel (s) for storing energy in the form of high pressure steam; COMBINED CYCLE ENGINE according to any one of claims 7 to 9, characterized in that it can switch off combustion in congestion, using combustion only after exhausting energy stored in the pressure vessel (s); A COMBINED CYCLE ENGINE according to claim 7, to strategically utilize as needed the energy stored in the vessel (s) as a booster, increasing the engine power for a short period of time.