EP3721069A1

EP3721069A1 - Device for reducing the quantity of emitted nitrogen oxides of a diesel engine

Info

Publication number: EP3721069A1
Application number: EP17835486.6A
Authority: EP
Inventors: Ravi VINAYAGAM
Original assignee: ENERIA
Current assignee: ENERIA
Priority date: 2017-12-08
Filing date: 2017-12-08
Publication date: 2020-10-14
Also published as: WO2019110877A1

Abstract

A device for reducing the quantity of nitrogen oxides emitted in the exhaust fumes of a diesel engine, said diesel engine comprising a combustion chamber (34) and an air compressor (29), said device comprising: - a water treatment system, for demineralising the water to be injected, - a water injection system, for injecting the demineralised water into said diesel engine, said water injection being carried out after said air compressor (29) and before said combustion chamber (34), said water injection into the combustion air enabling a lowering of the combustion temperature and thus of the emissions of nitrogen oxides, - safety means, such as probes and solenoids, for limiting and/or preventing the risks of malfunction of said diesel engine because of said device, and - a control system, comprising control means for determining the water injection parameters and/or for managing said safety means.

Description

Device for reducing the amount of nitrogen oxides emitted from a diesel engine

The present invention relates to a device for reducing the amount of nitrogen oxides emitted in the exhaust fumes of a diesel engine or generator, as well as an assembly formed of such a device associated with an engine or generator set running on diesel.

Generating sets using diesel as fuel emit more or less nitrogen oxides (called NOx), whose releases to the atmosphere are increasingly regulated through the new emission limit values (ELVs) specific to every geographical area in the world.

In some territories, ELVs fall below the emissions of generators in the market.

In order to remedy this environmental non-conformity, the present invention aims to provide a device whose purpose is to reduce the amount of nitrogen oxides emitted in the exhaust fumes of a diesel engine.

The present invention also aims to provide such a device that is simple and inexpensive to manufacture and assemble.

The present therefore relates to a device for reducing the amount of nitrogen oxides emitted in the exhaust fumes of a diesel engine, said diesel engine comprising a combustion chamber and an air compressor, said device comprising:

a water treatment system for demineralizing the water to be injected,

a water injection system for injecting deionized water into said diesel engine, said water injection being carried out after said air compressor and before said combustion chamber, said injection of water into the combustion air to lower the combustion temperature, and thus the emissions of nitrogen oxides,

safety means, such as probes and electro valves, for limiting and / or preventing the risks of malfunction of said diesel engine because of said device, and a control system comprising control means for determining the parameters of the water injection and / or for managing said safety means.

Advantageously, said water treatment system comprises a bottle containing strongly acidic and strong base anionic cationic resins for capturing the mineral salts of the water and thus demineralizing said water.

Advantageously, said water injection system comprises at least one spray nozzle generating a spray.

Advantageously, said spray forms an angle of approximately 45 °.

Advantageously, said spray has an average droplet size of about 0.5 μm.

Advantageously, said water injection system comprises an injection manifold comprising a water collecting tube provided with a plurality of connectors for connecting said tube to spray nozzles via flexible tubes.

Advantageously, said connectors are arranged on the top of said injection rail, to avoid any risk of gravity injection of the water present in the injection rail.

Advantageously, said security means comprise means for measuring one or more of the following parameters:

the volume of water treated by said water treatment system,

- the conductivity of the water,

- the water pressure,

- the temperature at the point of injection of water,

- the temperature at the intake manifold of the engine.

Advantageously, said safety means comprise at least a first electro-gap valve adapted to close the water supply in the event of power supply failure or at the request of the control system, at least one two-way valve that redundant the function said first solenoid valve, and at least one three-way valve to ensure the discharge of non-compliant water contained in the pipes to the sewer in case of malfunction of said water treatment system. Advantageously, said control means calculate the flow rate of water to be injected into the engine according to predetermined conditions.

Advantageously, said device comprises an air cooler disposed after said air compressor and before said combustion chamber, said water injection being performed after said air compressor and before said air cooler.

The present invention also relates to an assembly comprising a diesel engine and a device as described above.

These and other features and advantages will appear more clearly in the following detailed description, with reference to the accompanying drawings, given as non-limiting examples, and in which:

FIG. 1 is a schematic overview of the present invention, according to a first advantageous embodiment,

FIG. 2 is a schematic diagram of a different generator set that can be associated with the device of the present invention, forming a second advantageous embodiment,

FIG. 3 is a schematic perspective view of part of the device of FIG. 1,

FIG. 4 is a schematic representation of the measurement conditions of a device according to the present invention,

FIG. 5 is a detail view in cross section of a part of the device of FIG. 1,

FIG. 6 is a detailed view of the device of FIG. 1, illustrating advantageous security means,

FIG. 7 is a graph illustrating an example of mapping with three parameters, and

FIG. 8 is a graph illustrating an example of result obtained with the present invention.

In the description, the terms "high" and "low" refer to the right position of normal use of a motor, shown in FIGS. 1 to 3 and 5. The invention applies to diesel engines and generators. The following description will be made primarily with reference to a particular generator, namely the Caterpillar 3516 BHD engine, shown in Figure 1, but it is understood that the present invention could be applicable to any type of diesel engine. Thus, Figure 2 illustrates another generator, namely the Caterpillar 3516E engine, and will be described later the differences induced by this second embodiment.

In known manner, a diesel engine is an internal combustion engine whose ignition is spontaneous during the injection of fuel, by self-ignition phenomenon related to high temperatures in the combustion chamber or cylinder 34. These are achieved thanks to a high compression rate generated by an air compressor 29. The purpose of the compressor 29 is to increase the energy density in the combustion chamber 34, which makes it possible to increase the power of the engine without increasing its size or using a smaller engine (and therefore cheaper) for a given target power. By corollary effect, the ignition is facilitated.

An object of the invention is to lower the combustion temperatures because the temperature has been identified as a powerful catalyst for the formation of nitrogen oxides.

The principle of the invention is to supplement the humidity of the combustion air by the addition of water after the air compressor 29.

Introducing water in the form of fog, with a target droplet size of about 0.5 qm, in an enclosure at more than 200 ° C allows fine droplets to evaporate almost instantaneously by mixing with combustion air.

The lowering of the air temperature, due to the endothermic nature of the evaporation of the water, increases its density. This principle makes it possible to maintain the nominal oxygen supply despite the additional contribution of water vapor in the combustion air. As a result, the nominal power of the generator set is not impaired. The lowering of the air temperature has another consequence: it allows to lower the combustion temperature.

This principle is obtained by two phenomena:

the air cooled by evaporation, then by the exchanger, arrives less hot in the cylinder 34;

during the explosion in the cylinder 34, the heat capacity of the air over humidified is greater; the consequence is that its capacity to absorb the thermal energy released by the explosion is improved; this makes it possible to attenuate the rise in temperature in the cylinder 34 after explosion.

Thus, the nitrogen contained in the air is less oxidized and therefore there is less NOx production in the exhaust.

The device of the present invention takes into account the ambient conditions to adapt the injection of water to the relative humidity of the ambient air.

The device according to the invention comprises:

- a water treatment system;

an injection system;

safety means, such as probes and solenoid valves;

- a control system.

The system is designed to avoid any risk of non-start of the generator whose emergency function is often essential.

Water treatment system:

To avoid any risk of damaging the engine, it is necessary to inject the purest water possible, so without limescale or other ion that can cause deposits.

The demineralized water is obtained from a bottle made of strong acidic and strong base anionic cationic resins. The mineral salts are thus captured by the bottle allowing the production of demineralised water.

The quality of the produced water is measured by a communicating conductivity sensor with the control system. Injection principle:

The injection is carried out by nozzles placed between the air compressor 29 and the combustion chamber or cylinder 34, preferably between the air compressor 29 and the air cooler 33.

Preferably a nozzle is chosen at an angle of approximately 45 °, that is to say generating a spray forming an angle of approximately 45 °, to be adapted according to the configuration of the pipes.

The angle must be adapted to the tube in which it is desired to place the nozzle. An angle too small decreases the exchange surface and therefore the amount of evaporable water. An excessive angle projects water droplets on the walls, with a loss of efficiency.

Hereinafter, a first specific embodiment will be presented for a particular generator, namely the Caterpillar 3516 BHD engine shown in FIG.

The usual engine parts are drilled to place the nozzles, as shown in Figures 3 and 5. The position of the nozzle and its orientation is defined to maximize the nozzle / wall distance to optimize the heat exchange time between the air and water, and thus maximize the share of water that is vaporized.

Figure 5 illustrates the placement of a nozzle in a hollow bend member typically having a wall thickness of 6 mm.

A hole is machined in the curved upper part of the part, as shown in Figure 5.

Advantageously, the dimensions in this first embodiment may be the following:

d1 is between 90 mm and 120 mm, preferably 105 mm;

d2 is between 180 mm and 200 mm, preferably 193 mm; d3 is between 190 mm and 220 mm, preferably 205 mm; d6 is between 230 mm and 260 mm, preferably 245.1 mm;

d4 = d5 = d6 / 2; the diameter d7 of the hole is between 20 mm and 30 mm, preferably 25 mm;

the angle α of the axis of the hole with the vertical is between 15 ° and 25 °, preferably 19.5 °.

A nozzle-holder sleeve 20 is then welded into said hole to receive a suitable nozzle 4.

Figure 2 illustrates a second embodiment, with another model of generator set. In this variant, the nozzle 4 can be arranged in a flat vertical portion of the motor manifold, and the angle α of the axis of the hole with the vertical can then be 90 °. Alternatively, one could consider several nozzles, for example two, to distribute the flow and thus better evaporate. In this case, these nozzles could form a different angle, for example bias injection, as described above with reference to the first embodiment.

Hereinafter, it will be explained how the present invention calculates the amounts of water to be injected and which safety systems are provided.

Mobile parameters measured:

These parameters are measured by sensors included in the device, independent of the motor.

• HRi: relative humidity of the ambient air

• Ti: ambient air temperature

• Pi: ambient pressure

• MAP: boost pressure (after cooling, motor input)

• TOC: compressor outlet temperature (water injection point)

• MAT: inlet manifold temperature (after cooling, motor inlet)

• P: electrical power output alternator

• C: conductivity of the treated water

• Po: network water pressure Main calculated mobile parameters:

Td2: Dew point temperature

PWS: saturation vapor pressure

m is _INJECTI _Redie: water mass hourly Injection

Half _water : hourly water mass to be injected

PWi: ambient water vapor pressure

PWair: partial pressure of the air

Fixed parameters:

MaxNox: Nox level required by the client

D: hardness of the water used

CE: exchange capacity of the water treatment bottle

Parameters resulting from the cartography:

_{Carto injection} : the hourly water mass to be injected for the required MaxNox value and for each power

P _arto : Atmospheric pressure at the time of mapping

T _arto : Ambient temperature at the time of mapping

HR _carto : Ambient humidity at the time of mapping

Motor parameter:

m _air : hourly mass of air absorbed by the engine according to its technical data sheet, for each power

Figure 4 shows schematically the measurement conditions. Determination of the quantity of water to be injected:

The amount of water to be injected is defined experimentally by factory calibration. The conditions of this calibration are called "map conditions".

Once the engine is in production at the customer, the conditions may have changed and are then noted "real conditions".

Implementation of the cartography:

The hourly flow rate of water injected into the engine denoted m _{injection carto} is a function f of the power P and the level of Nox required:

™ -injection _carto = fiP Ma ^c NqC) f is defined experimentally for a humidity HR _carto and a temperature T _carto ·

Measurements are carried out in 100 kW increments between the nominal power of the motor and the motor power which leads to not injecting water because the production of Nox produced is less than MaxNox.

In practice, an injection pump 112 is controlled and, for each engine power level measured by sensors 35, the analog control signal of the pump 112 and the water injection flow rate (measured by a flowmeter 106) are defined. ).

Figure 7 shows a graph illustrating an example of mapping.

In this example, the experimental curves allow to define a polynomial equation of degree 5 to model the link between the three parameters of the cartography.

For the analog signal:

y = -293, 62x ⁵ + 2501 6x ^4-8108, 5x ³ + 12841c ² - 10010c + 3073.3

For the water flow:

y = -7.0304x ⁵ + 54.842x ⁴ - 166, 85x ³ + 248.5 lx ² - 181.59c + 52.149

The control system thus knows, on the basis of the engine power, the other two parameters in real time. The man-machine interface implemented makes it possible to enter in expert mode the coefficients of the two polynomials.

Corrective factor:

The _{cardboard injection} flow rate resulting from the mapping is advantageously corrected for the water flow rate brought by the presence of moisture in the combustion air if HRi is not identical to HR _carto .

The flow rate is also advantageously corrected for the ambient air temperature Ί \ if it differs from T _carto .

The control system can, if necessary, perform a correction of the mapping and refine the amount of water needed to inject.

Initiation start hysteresis:

A hysteresis of 40 kW is added at the start of the pump, to avoid a beat of the pump around the power value corresponding to the beginning of injection.

Injection control:

The injection is ordered by the control system if:

- the generator is running,

the outlet temperature TOC of the air compressor 29 is greater than 135.degree.

- MAT> Td ₃ + 4 ° C

the reading of the electrical power is greater than the minimum value of injection of the curve of the cartography,

the depollution order is activated by the user,

- there is no critical alarm.

Security:

In general, a generator is a tool of security of electrical supply. We do not want the modification of this emergency production tool for environmental purposes may degrade the security of electricity supply.

Accordingly, the device of the invention is designed to minimize the risk of loss of availability of the generator while ensuring its function to limit the production of NOx when it is put into operation.

For this, specific provisions have been deployed and are described below, with particular reference to FIG.

In this figure 6, the following elements are represented:

101: regulator

102: solenoid valve missing

103: pressure indicator

104: prefilter 25 qm

105: pressure switch

106: water meter

107: bottle of resin

108: conductivity meter

109: 1 qm filter

110: two-way motorized valve

111: three-way motorized valve

112: injection pump

Calculation of the remaining capacity of the resin:

In order to anticipate the saturation of the resin, the quantity of water injected by the water meter is measured and compared with the exchange capacity of the bottle 107, calculated from the hardness of the water. mains water according to the manufacturer's instructions.

The range Cp of the bottle expressed in liters is defined by the following formula:

With: CE: capacity of exchange for a water of 1 ° f of the bottle expressed in liter. French degree

D: hardness of water expressed in French degree

The control system may sound an alarm when the total processed volume reaches Cp.

Safety in case of non-compliant conductivity:

A second level of security exists in that a real-time conductivity measurement verifies the conductivity of the water. If it is not correct (if C> 50 qS / cm), the injection of water is stopped by the control system (sending treated water to the sewer).

We want to ensure that there can not be any water flow to the water collector from the device of the invention when the generator is off or in sleep mode, even in case of failure of the water network, which could cause a hydraulic plug involving the breakage of the engine at startup.

For this purpose a first solenoid valve 102 (solenoid valve normally closed at rest and acting in all or nothing) passively closes the water supply in case of power failure or on request of the control system, ensuring the shutdown. water injection as quickly as possible.

Downstream of this first electro valve 102, there is provided a two-way motorized valve 110 with cam position sensor that informs the state of the valve position (passing or not), this two-way valve 110 redundant the function of the first solenoid valve 102. It also allows a gradual closure of the network avoiding water hammers.

This two-way valve 110 is closely followed in series by a three-way valve 111 with a cam position sensor which indicates either the state to purge 150 or to the engine. By default, the position of this valve 111 is always oriented towards the purge position.

The presence of this three-way valve 111 ensures the emptying of the non-compliant water contained in the pipes to the sewers in case of malfunction of the treatment bottle 107. It also purges the pipes when the generator is stopped.

In idle mode (no water injection), the solenoid valves are closed and to ensure that there is no filling in the cylinders 34, the three-way valve 111 is closed on the engine side and open on the evacuation side 150.

The positions of the two-way valves 110 and three channels 111 are monitored and if there is any discrepancy of position, the injection is stopped by the control system and an alarm is triggered.

And to reinforce this overall strategy of valves in series, a final solenoid valve can be activated only by order of the control system (analog signal greater than 0.1V).

Motorized valves are preferred to solenoids to avoid the phenomenon of "glue effect" following a high differential pressure in the conduit.

Voltage monitoring:

If the device of the invention was to lose its power supply, an autonomous block ensures the continuity of operation of the control system. In the event of a voltage drop, the valves are closed by the control system and a "Nox Not Compliant" alarm is issued.

If the power supply to the control system should be corrupted, a nonconformity alarm may be issued and any injection stopped.

Loss of probe:

If any of the analog probes are not working properly such as MAT, MAP, TOC, HR, P, C, Po, a nonconformity alarm can be issued and any injection stopped.

Water pressure of the non-compliant network:

The device of the invention comprises a pressure reducer 101 disposed just behind the water inlet. It is ensured that the water pressure of the network Po after the pressure reducer 101 is preferably in the following range:

2 bar <Po <2.5 bar

In case of non-compliance, the injection of water can be cut off.

Buses:

A nozzle having a calibrated orifice whose flow is capped is preferably chosen, even in case of overpressure upstream of the nozzle, in order to avoid any risk of accumulation of water in the engine.

TOC monitoring (temperature at the point of water injection:

The water injection is performed with a positive displacement pump 112, so that at low flow, it is low pressure. As a result, the quality of the droplets produced can be degraded, with the size of the droplets that may no longer be guaranteed.

In order to avoid a lack of water vaporization, the control system may prohibit the injection of water if the TOC is less than 120 ° C, preferably less than 135 ° C. MAT temperature (temperature at the intake manifold:

We want to ensure that there is no risk of condensation of water in the collector and therefore in the cylinders 34. For this, we must ensure that the measured temperature MAT remains higher than the dew point. The challenge is to calculate the temperature of the dew point Td ₃ at the riskiest point, that is to say after cooling.

The following points are noted with reference to FIG. 4:

The theoretical dew point temperature Td _{3 is} first calculated.

We begin by calculating the saturated water vapor pressures PWSi and PWS ₃ at points 1 and 3 according to the approximate equation of W. Wagner and A. Pruf: "The IAPWS Formulation 1995 for the Thermodynamics Properties of Ordinary Water Substance for General and Scientific Use, "Journal of Physics and Chemical Reference Data, June 2002, Volume 31, Issue 2, pp. 387535. PWSi, i = 1 or 3, expressed in hPa, is calculated as follows:

With:

Ti

ΰ = 1 -

T _c

Tc = Critical Temperature expressed in K equal to 647.096 K

Pc = Critical pressure expressed in hPa equal to 220 640 hPa

MAT expressed in K

T _; the temperature T, or MAT according to the desired point i

C1 to C6 the following unitless coefficients:

The number of moles of water is then calculated and injected per hour without the addition of water, solely by the presence of water from the ambient atmosphere, using the ideal gas law and Dalton's law.

With:

HRi the moisture level in point 1

See the volume of air injected per hour

R = 8.3 JK mol ¹

PWi the partial pressure of the water calculated by the formula:

PW ₁ = HR _± * PWS ₁

The number of moles n injected per hour at point 2 is calculated by the formula:

mÎnjectÎon _SOE u _e

n = -

Skin

With:

Real _{injection time} the mass of water injected per hour in gram

g _water the molar mass of water is 18.0153 g / mol

N3 is the number of moles of water at point 3 per hour:

n ₃ = + n

N is computed _ai, the number of moles of air, including its moisture absorbed by the motor per hour, calculated as:

From this it is deduced, considering the gases as perfect, the vapor pressure PW ₃ at point 3 by Dalton's law:

The temperature of the dew point Td _{3 is} deduced from it by the following empirical formula, published by Vaisala Oyj in the document entitled "HUMIDITY

CONVERSION FORMULAS "(B210973EN-F - Vaisala 2013):

With:

T _n , M and A: constants as a function of the temperature T ₃ according to the values of the following table:

PW ₃ the vapor pressure expressed in mbar. Temperature control:

Temperature control ensures that the MAT temperature is maintained above the dew point to prevent condensation.

We take a guard of + 4 ° C; that is to say that we make sure that:

MAT> Td3 + 4 ° C Power measurement:

The measurement of the power P is performed by a current transformer at each phase and by a reference voltage measurement supplying a dedicated power converter. In this way, the power measurement is independent of the motor. This strategy, in which one does not connect to the power measurement means of the engine itself, eliminates a risk of wiring error that could be detrimental to the safety function of the generator itself. Design of the initiation ramp:

The device comprises an injection manifold 1 visible in FIG. 3. This injection manifold 1 comprises a water collecting tube 2 provided with a plurality of connectors for connecting said tube 2 to spray nozzles 4, via suitable flexible tubes. Each nozzle 4 is supported by a nozzle holder 3, which is fixed in the sleeve 20 assembled in the engine part 10, here a bend.

The injection manifold 1 is advantageously designed with a water inlet from above to avoid any risk of injection by gravity of the water present in the injection manifold, in case of anomaly. Hysteresis:

Hysteresis around the power curve, formed of a dead band at +/- 40 kW, is preferably provided to prevent rapid start / stop of the injection pump 112 around the injection start point. Crankcase gas:

A crankcase de-oiling system 30 is associated with the device of the invention. Indeed, it has been found a significant presence of water in the housing when using the device of the invention, given the fact that the piston / cylinder connection is never completely hermetic. Priority management of emergency stops:

The priority management in case of actuation of an emergency stop by the user is as follows:

If emergency stop of the device of the invention: shutdown of the device, no stop of the generator;

If generator set shutdown: device and generator set off.

Check hvdro:

A sequence of opening and closing the water valves, called "check hydro", is preferably performed at regular intervals (for example every month), so as to:

- test their correct operation (generation of an alarm in the event of a fault),

- evacuate the water to allow the water not to stagnate too long. Natural stop of the iniection system:

The so-called "cooling time" generator shutdown delay is set so that the shutdown lasts for 3 minutes, so as to evacuate the humid air and avoid any condensation of water. Obtained result :

Figure 8 illustrates an example obtained with a Caterpillar 3516 BHD engine for an MAxNox value of 1700 mg / Nm3.

It can be seen that whatever the power, the device of the invention makes it possible to remain below the limit value of 1700 mg / Nm3.

The present invention has been described with reference to advantageous embodiments, but it is understood that a person skilled in the art can make any modifications, without departing from the scope of the present invention as defined by the appended claims.

Claims

claims

1.- A device for reducing the amount of nitrogen oxides emitted in the exhaust fumes of a diesel engine, said diesel engine comprising a combustion chamber (34) and an air compressor (29), characterized in what said device comprises:

a water treatment system for demineralizing the water to be injected,

a water injection system, for injecting deionized water into said diesel engine, said water injection being carried out after said air compressor (29) and before said combustion chamber (34), said injection water in the combustion air to lower the combustion temperature, and thus the emissions of nitrogen oxides,

safety means, such as probes and electro rings, for limiting and / or preventing the risks of malfunction of said diesel engine because of said device, and

a control system comprising control means for determining the parameters of the water injection and / or for managing said safety means.

2.- Device according to claim 1, wherein said water treatment system comprises a bottle (107) containing strongly acidic and strong base anionic cationic resins for capturing the mineral salts of the water and thus demineralizing said water.

3.- Device according to claim 1 or 2, wherein said water injection system comprises at least one spray nozzle (4) generating a spray.

4.- Device according to claim 3, wherein said spray forms an angle of about 45 °.

The device of claim 3 or 4, wherein said spray has an average droplet size of about 0.5 μm.

6.- Device according to any one of the preceding claims, wherein said water injection system comprises an injection ramp (1) comprising a water collecting tube (2) provided with a plurality of connectors for connecting said tube (2) to spray nozzles (4) via flexible tubes (5).

7.- Device according to claim 6, wherein said connectors are disposed on the top of said injection rail, to avoid any risk of gravity injection of the water present in the injection rail.

8.- Device according to any one of the preceding claims, wherein said security means comprise means for measuring one or more of the following parameters:

the volume of water treated by said water treatment system,

- the conductivity of the water,

- the water pressure,

- the temperature at the point of injection of water,

- the temperature at the intake manifold of the engine.

9.- Device according to claim 8, wherein said security means comprise at least a first electro-gate valve (102) adapted to close the water supply in case of power failure or on request of the system. control, at least one two-way valve (110) redundant the function of said first solenoid valve (102), and at least one three-way valve (111) to ensure the discharge of non-compliant water contained in the pipes to the sewer in case of malfunction of said water treatment system.

10.- Device according to any one of the preceding claims, wherein said control means calculate the flow of water to be injected into the engine according to pre-established conditions.

11.- Device according to any one of the preceding claims, comprising an air cooler (33) disposed after said air compressor (29) and before said combustion chamber (34), said water injection being performed after said air compressor (29) and before said air cooler (33).

12. An assembly comprising a diesel engine and a device according to any one of the preceding claims. j? J? J?