COMMON-RAIL ENGINE

Technical Field The invention relates to systems enabling use of liquefied petroleum gas in diesel common-rail engines, and in particular to fueling diesel engines with diesel LPG dual-fuel or only LPG instead of diesel fuel. Background Art

With increasing environmental impact on transportation, the demand for sustainable fuels and fuel systems is increasing. The liquid petroleum gas (LPG) is known as a cleaner alternative fuel for a production engine.

The engine using both diesel fuel and LPG, is referred to as LPG-diesel dual fuel engine. LPG fuel in such engines is typically used as primary fuel and diesel - as secondary fuel. LPG dual fuel engines have a good thermal efficiency at high output but the performance is less during part load conditions because of poor utilization of charges. This problem is tried to be solved by several researchers. Some researchers proposed to vary such factors as pilot fuel quantity, injection timing, composition of the gaseous fuel and intake charge conditions, for improving the performance.

One of more creative approaches was adding water to internal combustion engine (Lestz SJ, etal. Feasibility of cooling diesel engines by introducing water into the combustion chamber. SAE Trans 1975:606-19). This study showed that 5.5 lb of water injection is required per lb of fuel in order to provide removal of the waste heat, which is normally removed by jacket cooling. Lanzafame’s study (Lanzafame R. Water injection effects in a single-cylinder CFR engine. SAE 1999) showed that water injection in the intake pipe can be a way to avoid detonation, to reduce compression work and to control NOx production in spark ignition engines.

There is known an in-cylinder water injection engine (US 5937799) utilizing direct, in- cylinder water injection and an optional oxygen enriched air supply. According to the inventor, the in-cylinder low-temperature water injection lowers compression temperatures, which permits increased compression ratios while avoiding preignition. As well, the low-temperature water injected air/fuel increases overall engine efficiency. The known engine comprising: an internal combustion engine having at least one combustion chamber, at least one cylinder head secured to the combustion chamber and at least one piston disposed within said combustion chamber; an air/fuel intake manifold in fluid communication to the combustion chamber through the cylinder head; at least one water injector in fluid communication to the combustion chamber; a constant pressure water source connected to the water injector by a water conduit; a valve in the water conduit responsive to the compression cycle of the engine to open and let water flow to the water injector during each compression cycle of the engine; a source of enriched oxygen connected to air to the air/fuel intake manifold by an enriched air conduit; and a turbocharger compressor operatively connected to the exhaust conduit and the enriched oxygen source to compress the air passing to the enriched oxygen source.

There is known an internal combustion engine with steam expansion stroke (US6986252), the engine having at least one cylinder, a reciprocating piston arranged in the cylinder, a combustion chamber delimited by the cylinder and the piston, and inlet and outlet valves that are controlled by a computer-based control system. The combustion engine includes elements for injecting water or water steam into the combustion chamber), and the control system is arranged to control the inlet and outlet valves and the elements for injection of water or water steam such that power strokes that are mainly based on expanding combustion gases are alternated with power strokes that are mainly based on expanding water steam. There is known a water injection device of an internal combustion engine, and method for operating a water injection device (US10378435). The water injection device comprising: a water tank configured to store water; a conveying element configured to convey the water, the conveying element connected to the water tank; at least one water injector configured to inject water, the at least one water injector connected to the conveying element; a pressure sensor arranged in a line region between the conveying element and the at least one water injector; and a control unit configured, based on pressure data of the pressure sensor, to determine a formation of steam in the line region when the at least one water injector is closed and the conveying element is switched off.

Summary of Invention

The present invention is an improvement provided to solve the conversion problem of existing diesel engines to diesel and LPG dual-fuel or only LPG fuel engines.

An LPG ultrasonic transducer system for operating a diesel common-rail engine, comprises an electronic control unit; a water tank; an LPG tank with LPG supply shut-off valve; an LPG level sensor; an LPG pump operably connected with the LPG tank; a water pump operably connected with the water tank; a mixer comprising a water level sensor and an ultrasonic transducer adapted to generate water vapor and LPG mixture; wherein the mixer comprises two compartments: the upper compartment and the lower compartment; the means for separation of the upper and the lower compartments comprising an antireflux valve adapted to allow micro drops of water from the lower compartment to pass through the anti-reflux valve to the upper compartment and to prevent any macro drops of water from flowing into the upper compartment; wherein the upper compartment of the mixer comprises an outlet operably connected with engine intake manifold; wherein the outlet of the LPG pump is operably connected with the upper compartment of the mixer, the outlet of the water pump is operably connected with lower compartment of the mixer, where the ultrasonic transducer is located below the anti-reflux valve. The controlled interaction between elements of the system and vehicle elements results in an LPG-water vapor mixture. In case of embodiment with dual fuel, the water LPG mixture is calculated on the grounds of information received by the electronic control unit of the system from the engine common-rail (pressure from the rail (bar)), from the engine temperature sensor (temperature), from the air flow meter sensor (air flow - m ³ /s), from the acceleration pedal block (pedal position). In case of embodiment with LPG only, the mixture is calculated on the grounds of information received by the electronic control unit of the system from the engine common-rail (pressure from the rail (bar)), from the engine temperature sensor (temperature), from the air flow meter sensor (air flow - m ³ /s), from the acceleration pedal block (pedal position), from the crankshaft (engine rpm).

Brief Description of Drawings Fig. 1 is a schematic representation of the proposed LPG ultrasonic transducer system; Fig.2 is a block diagram, representing elements of the proposed LPG ultrasonic transducer system as installed in a vehicle having a diesel common-rail engine and operating as diesel and LPG dual-fuel engine;

Fig. 3 is a block diagram of another embodiment; representing elements of the proposed LPG ultrasonic transducer system as installed in a vehicle having a diesel common-rail engine and operating as LPG fuel engine;

Fig. 4 is a graph, showing examples of common-rail signals causing the system to enter standby mode (A) and operation mode (B);

Fig. 5 shows a flow chart of a method for operating a diesel common-rail engine using lpg ultrasonic transducer system. Detailed Description of Invention

According to one embodiment the proposed LPG ultrasonic transducer system for operating a diesel common-rail engine (Fig. 1-2), comprises: an electronic control unit 101; an LPG supply subsystem, comprising operably connected: an LPG tank 207, an LPG shut-off valve 213, an LPG pressure regulator 212, an LPG pump 102, an LPG level sensor 208; awatersupply subsystem, comprising operably connected: a water tank 209, awater pump 103, a water level sensor 105. The LPG ultrasonic transducer system for operating a diesel common-rail engine further comprising a mixer 104 comprising the water level sensor 105 and an ultrasonic transducer 106 adapted to generate water vapor and LPG mixture. The outlet of the LPG pump 102 is operably connected with the upper compartment of the mixer 104, the outlet of the water pump 103 is operably connected with lower compartment of the mixer 104.

The mixer 104 (Fig. 1) comprises two compartments: the upper compartment and the lower compartment, the means for separation of the upper and the lower compartments comprising an anti-reflux valve 109 adapted to allow micro drops of water from the lower compartment to pass through the anti-reflux valve 109 to the upper compartment and to prevent any macro drops of water from flowing into the upper compartment; wherein the upper compartment of the mixer 104 comprises an outlet 108, which is operably connected with automobile engine intake manifold 205. The ultrasonic transducer 106 is located below the anti-reflux valve 109. In the air intake manifold 205 the LPG and water vapor mixture is transported with the air to the engine combustion chamber, where the LPG and water vapor mixture ignites together with the air and the diesel fuel spray.

The system further comprising an air flow meter sensor 204 operably connected between the mixer 104 outlet 108 and the engine intake manifold 205, the air flow meter sensor 204 is further connected with the electronic control unit 101 and is adapted to measure the gas mixture flow and to send respective signals to the electronic control unit 101 (Fig. 2). The electronic control unit 101 is electrically connected with the rail 201 and is designed to receive and read the common-rail pressure signal from the rail 201. Also, the rail 201 signal may be used to control operation of the proposed system (i.a. entering operation mode and stand-by mode). The electronic control unit 101 is further electrically connected with the LPG pump 102 to be able to control its operation. The electronic control unit 101 is further electrically connected with the acceleration pedal block 202 to be able to receive and read a signal from the acceleration pedal block 202. The electronic control unit 101 is further electrically connected with the engine temperature sensor 203 to be able to receive and read a temperature signal from the engine temperature sensor 203. The electronic control unit 101 is further electrically connected with the automobile throttle valve 206 to be able to control its opening and closing. The LPG and water vapor mixture is distributed into the air intake manifold 205, where the air flow is regulated by the throttle valve 206.

The electronic control unit 101 is further electrically connected with the water level sensor 105 to be able to receive and read a signal from the water level sensor 105. The water supply subsystem is designed to maintain the necessary water level for working of the transducer 106 in any conditions.

The electronic control unit 101 is further electrically connected with the transducer 106 and is designed to be able to send an output signal to the transducer 106; the electronic control unit 101 is further electrically connected with the LPG level sensor 208 to be able to receive and read a signal from the LPG level sensor 208; the electronic control unit 101 is further electrically connected with the LPG supply shut-off valve 213 to be able to send output signals to control opening and closing of the shut-off valve 213.

The electronic control unit 101 is adapted to calculate an LPG and water vapor mixture composition for the mixer 104, according to pre-set parameters and the information (input signals) received from the acceleration pedal block 202, the rail 201, the water level sensor 105, the transducer 106, the LPG level sensor 208 and the air flow meter sensor 204.

According to yet another embodiment the electronic control unitlOl is further electrically connected with the built-in car central electronic control unit 210. When the rail 201 sends a signal (e.g. 0,55 V] to the electronic control unit 101 (used together with the e.g. 5V signal from the built-in car central electronic control unit 210) - the system enters stand-by mode, while when the e.g. 0,9 V is received from the rail 201 (aprox. 230 bar pressure in the rail 201 +/- 10%) the motor is running and the proposed system starts after two second delay (Fig. 4). When the signal from the rail 201 is below e.g. 0,9V, the electronic control unit 101 enters the proposed system to stand-by mode. According to the embodiment the rail 201 signal (e.g. 0,55 V) and built-in car central electronic control unit 210 signal (e.g. of 5V) is used together to enter stand-by in order to prevent system malfunctions. When one of the signals is not present, the proposed system does not start stand-by mode. For the skilled person it is obvious that the voltage level indicated above is just indicative and may have different values.

According to the preferred embodiment of the invention, the system comprises a kit, comprising: the electronic control system 101; the mixer 104 comprising the water level sensor 105 and the transducer 106; the water pump 103 and the LPG pump 102 adapted to be installed on an automobile having a diesel common-rail engine. According to this embodiment the water tank 209 is a windshield fluid tank already present in an automobile and the water level sensor 105 is the windshield fluid level sensor already present in the automobile’s windshield fluid tank. The system can be adapted to be powered by the automobile battery. Thus, the LPG pump 102 is adapted to be operably connected to the LPG tank 207 already present in the vehicle. The water pump 103 is adapted to be operably connected to the water tank 209 already present in the vehicle. The electronic control unit 101 id adapted to be electrically connected to the following elements of the vehicle: rail 201, engine temperature sensor 206, acceleration pedal block 202, LPG level sensor 208, LPG supply shut-off valve 213 and gas pressure regulator 212, air flow meter sensor 204, throttle valve 206, vehicle battery 211.

The module operates as follows. The water pump 103 fills the mixer 104, the water level sensor 105 maintains the pre-set constant level of water in the lower compartment, the ultrasonic transducer 106 turns on and begins to nebulize water towards the upper compartment of the mixer 104. The anti-reflux valve 109 in the mixer 104 prevents any macro drop of water from flowing into the upper part of the mixer 104. After receiving a signal from the car acceleration pedal block 202, the electronic control unit 101 sends a signal to the LPG pump 102, which introduces the LPG tangentially to the upper compartment of the mixer 104. The mixed LPG and nebulized water leaves from the mixer 104 through the outlet 108 to the engine intake manifold 205, through the throttle valve 206, being controlled by the electronic control unit 101. A non-return valve 110 located before the water pump 103 ensures that the water does not return to the water tank 209 and the gas escapes when the LPG pump 102 is in operation.

According to another embodiment, a diesel common-rail engine can be converted to operate only as LPG fuel engine. According to this embodiment the system (Fig. 2) further comprises a spark plug 301 and ignition coil 302 replacing the engine’s glow plug. The electronic control unit 101 is electrically connected with the spark plug 301 and the ignition coil 302 to be able to send an output signal to the spark plug 301 and the ignition coil 302. The electronic control unit 101 is further electrically connected with engine’s camshaft 303 and engine’s crankshaft 304 to be able to receive and read a signal from the camshaft 303 and the crankshaft 304. Replacing the engine’s glow plug by a spark plug 301 and the ignition coil 302 transforms the ignition chamber to an Otto cycle engine and the detonation is started by spark using only air and the LPG and water vapor mixture instead of diesel fuel. According to the present embodiment the correct moment for ignition with spark plug 301 is calculated by the electronic control unit 101 using signal from the camshaft 303 and the crankshaft 304, where the ignition process is equal to Otto cycle. A method for operating a diesel common-rail engine, using the proposed LPG ultrasonic transducer system comprises the following steps:

(i) with electronic control unit 101 collect common rail 201 pressure signal;

(ii) with electronic control unit 101 collect acceleration pedal signal from the acceleration pedal block 202;

(iii) with electronic control unit 101 collect air flow signal from the air flow meter sensor 204;

(iv) with electronic control unit 101 based on common rail pressure signal, acceleration pedal signal and air flow signal collected on previous steps, calculate water-vapour and LPG mixture;

(v) with electronic control unit 101 send a signal to the LPG pump 102 and water pump 103 to inject into the mixer 104 the pre-setamount ofwater and calculated amountof LPG;

(vi) with electronic control unit 101 to send a signal to ultrasonic transducer 106 to generate water vapor and LPG mixture;

(vii) conveying the generated water vapor and LPG mixture through the mixer 104 outlet 108 to the engine intake manifold 205.

Accordingto one embodimentthe calculation ofwater-vapour and LPG mixture atthe step (iv) can be made using the following formula: G = (A+B)/2 - C, wherein A is the common- rail pressure signal, B - acceleration pedal signal, C - air flow signal and G - the effective LPG volume, wherein water volume is a pre-set constant value. It should be noted that other ways, formulas and principles of calculation of water-vapour and LPG mixture are possible.

According to yet another embodiment (Fig. 5) the method further comprises the following steps before the step (i):

(a) with electronic control unit 101 collect engine temperature signal from the engine temperature sensor 203, if the signal corresponds to the set value, proceed to step (b), if not - return to the step (a); (b) with electronic control unit 101 collect common rail 201 signal, if the signal corresponds to the set value, proceed to the step (c), if not - return to the step (b);

(c) with electronic control unit 101 collectengine electronic control unit210 signal, if the signal corresponds to the set value, proceed to the step (d), if not - return to the step (b); (d) the system enters standby mode; with electronic control unit 101 collect water lever sensor 105 signal, if the signal corresponds to the set value, proceed to the step (e), if not - return to the step (d);

(e) with electronic control unit 101 collect engine common-rail 201 signal, if the signal corresponds to the set value, proceed to the step (f), if not - return to the step (d); (f) the system enters operating mode; with electronic control unit 101 send a signal to the

LPG shut-off valve 213 causing valve 213 opening; further proceed to step (i) as described above.

According to the same embodiment the method further comprising the following step after the step (vii) of conveying the generated water vapor and LPG mixture through the mixer 104 outlet 108 to the engine intake manifold 205: (z) with electronic control unit 101 collect common rail 201 signal; if the signal corresponds to the set value one, return to the step (ii) of collecting acceleration pedal signal from the acceleration pedal block 202; if the signal corresponds to the set value two - return to the step (c) of collecting engine electronic control unit 210 signal; if the signal does not correspond to the set value one and two - end process.

Accordingto one embodimentthe calculation ofwater-vapour and LPG mixture atthe step (iv) can be made using the following formula: G = (A+B) /2 - C, wherein A is the common- rail pressure signal, B - acceleration pedal signal, C - air flow signal and G - the effective LPG volume, wherein water volume is a pre-set constant value. It should be noted that other ways, formulas and principles of calculation of water-vapour and LPG mixture are possible. According to yet another embodiment (Fig. 5) the method further comprises the following steps before the step (i):

(a) with electronic control unit 101 collect engine temperature signal from the engine temperature sensor 203, if the signal corresponds to the set value, proceed to step (b), if not - return to the step (a);

(b) with electronic control unit 101 collect common rail 201 signal, if the signal corresponds to the set value, proceed to the step (c), if not - return to the step (b);

(c) with electronic control unit 101 collectengine electronic control unit210 signal, if the signal corresponds to the set value, proceed to the step (d), if not - return to the step (b);

(d) the system enters standby mode; with electronic control unit 101 collect water lever sensor 105 signal, if the signal corresponds to the set value, proceed to the step (e), if not - return to the step (d);

(e) with electronic control unit 101 collect engine common-rail 201 signal, if the signal corresponds to the set value, proceed to the step (f), if not - return to the step (d);

(f) the system enters operating mode; with electronic control unit 101 send a signal to the LPG shut-off valve 213 causing valve 213 opening; further proceed to step (i) as described above.

According to the same embodiment the method further comprising the following step after the step (vii) of conveying the generated water vapor and LPG mixture through the mixer 104 outlet 108 to the engine intake manifold 205: (z) with electronic control unit 101 collect common rail 201 signal; if the signal corresponds to the set value one, return to the step (ii) of collecting acceleration pedal signal from the acceleration pedal block 202; if the signal corresponds to the set value two - return to the step (c) of collecting engine electronic control unit 210 signal; if the signal does not correspond to the set value one and two - end process. For the correct ignition moment in the ignition chamber for the generated water vapor and LPG mixture, the electronic control unit 101 collects signal the from the camshaft 303 and the crankshaft 304. Based on the collected signals the electronic control unit 101 sends a signal to the spark plug 301. The processing of the signals from the camshaft 303 and the crankshaft 304 is made according to the known from the prior art Otto-cycle.