Gas feed method for a gas engine or dual-fuel engine, and gas supply apparatus for same

Abstract

A gas feed method for a gas engine or dual-fuel engine in which combustion gas (G) is burned with combustion air (L). A gas valve (1) for the feed of combustion gas (G) into the combustion air (L) is arranged upstream of the gas engine or dual-fuel engine. The combustion gas (G) is fed in uncontrolled fashion to the gas valve (1) independently of the operating state of the gas engine or dual-fuel engine. The invention furthermore relates to a gas supply apparatus. A gas valve (1) for the feed of combustion gas (G) into the combustion air (L) is arranged in the gas feed (10) upstream of the gas engine or dual-fuel engine. Control of the gas pressure in a manner dependent on the operating state of the gas engine or dual-fuel engine is not provided upstream of the gas valve (1).

Claims

1. A gas pressure control system free gas feed method for a gas engine or dual-fuel engine in which combustion gas (G) is combusted with combustion air (L), comprising arranging a gas valve (1) for supplying combustion gas (G) in the combustion air (L) upstream of the gas engine or dual-fuel engine, and supplying the combustion gas (G) to the gas valve (1) without a gas pressure control system regulated by the load situation and charge air pressure of the gas engine or dual-fuel engine, wherein the gas metering occurs solely via the precise control of the gas valve, wherein during operation of the gas engine or dual-fuel engine, the pressure before and after the gas valve (1) as well as the temperature of the supplied combustion gas are measured, the engine operating point is detected and from this at least one of an opening duration and an unblocked opening cross-sectional area of the gas valve (1) are controlled, and wherein the gas valve (1) is provided immediately upstream of the inlet area of the gas engine or dual-fuel engine.

2. The method according to claim 1, wherein a previously detected flow performance map of the gas valve (1) is stored and at least one of the opening duration and the unblocked opening cross-sectional area of the gas valve (1) is controlled according to instantaneous measured values, the current engine operating point and the flow performance map.

3. The method according to claim 1, wherein the gas valve (1) is a pressure-balanced valve.

4. A gas engine or dual-fuel engine of the type having no gas pressure control system in the gas feed, in which combustion gas (G) is burned with combustion air (L), with a source of pressurized combustion gas, a source of combustion air (L), a gas engine or dual-fuel engine having an inlet area, a pressure-balanced gas valve (1) provided immediately upstream of the inlet area of the gas engine or dual-fuel engine, the gas valve (1) supplying combustion gas (G) in the combustion air (L) upstream of the gas engine or dual-fuel engine, a gas feed (10) connecting the source of pressurized combustion gas to the gas valve (1), the gas feed (10) having no gas pressure control system for control of the gas pressure upstream of the gas valve (1) in dependence on the operating state of the gas engine or dual-fuel engine, and a gas pressure control system comprising control logic wherein a previously detected flow performance map of the gas valve (1) is stored, the control logic programmed to receive measurements during operation of the gas engine or dual-fuel engine including the pressure before and after the gas valve (1) as well as the temperature of the supplied combustion gas are measured, wherein at least one of the opening duration and the unblocked opening cross-sectional area of the gas valve (1) is controlled according to instantaneous measured values, the current engine operating point and the flow performance map independent of the actual pressure differential, wherein gas metering in the gas pressure control system occurs solely via precise control of the gas valve (1).

5. The gas feed apparatus according to claim 4, wherein in the gas feed (10), a pressure limiter or a pressure reducer independent of the operating state of the gas engine or dual-fuel engine is provided upstream of the gas valve (1).

6. The gas feed apparatus according to claim 4, wherein the gas valve (1) is designed to be actuated independently of the there impinging pressure difference.

7. The gas feed apparatus according to claim 6, wherein the gas valve (1) is a pressure-balanced valve.

8. The gas feed apparatus according to claim 6, wherein the gas valve (1) is a poppet valve (11) and has an opposing piston (12), wherein the opposing piston (12) has approximately the same effective cross-sectional area as the poppet valve (11).

9. The gas feed apparatus according to claim 7, wherein the poppet valve (11) and the opposing piston (12) are provided on a shaft (13), wherein the poppet valve (11) and the opposing piston (12) of the gas valve (1) are guided with the shaft (13) in a housing (14).

10. The gas feed apparatus according to claim 7, wherein the gas valve (1) has a poppet valve (11) and a pressure diaphragm (15), wherein the pressure diaphragm (15) has approximately the same effective cross-sectional area as the poppet valve (11).

11. The gas feed apparatus according to claim 10, wherein the poppet valve (11) and the pressure diaphragm (15) are arranged on a shaft (13), wherein the poppet valve (11) with the shaft (13) are guided in a housing (14) and the pressure diaphragm (15) is secured in the housing (14).

12. The gas feed apparatus according to claim 7, wherein for the gas valve (1) an auxiliary valve (23) with auxiliary actuator (22) is provided, which in a rest position forms a fluid connection to one side of the opposing piston (12) or pressure diaphragm (15) and in a activated position provides a fluid connection to a reduced pressure (p.sub.3).

13. The gas feed apparatus according to claim 9, wherein an actuator (2) acting on the shaft (13) is provided for positioning the gas valve (1).

Description

(1) Therein there is shown in:

(2) FIG. 1 a test rig construction for determining the flow behavior of the gas valve,

(3) FIG. 2 a determined flow performance map,

(4) FIG. 3 a first embodiment of a gas valve in a sectional, schematic side view,

(5) FIG. 4 a second embodiment of a gas valve,

(6) FIG. 5 a third embodiment of a gas valve,

(7) FIG. 6 a fourth embodiment of a gas valve and

(8) FIG. 7 a fifth embodiment of a gas valve.

DETAILED DESCRIPTION OF THE INVENTION

(9) In FIG. 1, a test stand is shown with which the flow behavior of the gas valve 1 to be used can be determined. The test bench consists of a measuring section into which the gas valve 1 is initially mounted in the closed state and then subjected to a defined source and reduced pressure. Care must be taken to ensure that the source and reduced pressure (i.e., the pressure ratio across the valve) always correspond to values that can also occur in real engine operation. The reduced pressure, which corresponds to the charge air pressure, is in this case generally in a range between 1 bar.sub.abs and 6 bar.sub.abs, while the source pressure corresponds to the (reduced) tank pressure of the gas tank, minus the system pressure losses. As a rule, the tank pressure is max. 10 bar.sub.abs, but this can vary. The valve is now opened for different pressure conditions, gas temperatures and opening times, and the through-flow is determined by measurement. The variation of the opening intervals of the valve is important, especially since with short opening times (e.g., in part-load operation) the proportion of closing and opening operation within the total flow time is significantly greater than at large opening times, which are characterized in that the valve is completely open over a relatively long period of time and the through-flow behavior consequently does not change for a corresponding length of time. Accordingly, the volume through-flow in these (part-load) operating points is very dynamic and thus also valve-specific, which makes calculation significantly more difficult. Furthermore, it is theoretically possible, depending on the valve design and pressure ratio, that in the narrowest cross section the flowing medium reaches the velocity of sound, and thus a limit value for the volumetric flow through of the valve to be reached. This phenomenon can influence the structure of the map.

(10) After determining a sufficient number of sampling points, the valve flow characteristic map can be produced (FIG. 2). Now the gas volume that passes through the valve is known as a function of the opening duration and the pressure ratio in each theoretically possible operating point of the machine. Taking into account the temperature and density and calorific value of the fuel gas, the supplied energy flow or the amount of energy supplied per cycle can now be determined. By storing said map in the engine control, a control strategy is conceivable, as has long been used in diesel engines (Note: Here, the amount of energy supplied is known, since it is proportional to the volume of fuel which is in the liquid state in the equipment).

(11) The inventive method makes it possible to replace the pressure regulator from the original configuration with a simple pressure reducer or to completely dispense with this component. By eliminating the control tasks, there is no need to incorporate an additional component in the engine control. Furthermore, there is no longer any need to position the remaining gas fittings in the immediate vicinity of the engine.

(12) In the implementation of the method according to the invention, the flow performance map is to be stored in the controller, so that the gas mass for each injection process and thus the amount of energy supplied can be measured either in good approximation or even exactly (if the gas composition and thus the calorific value are known). The method assumes that the volume flow through the valve is known at any time in dependence on the pressure difference across the valve. By means of a temperature and pressure measurement, the density of the gas can be determined. The product of density and volume flow provides the gas mass flow, which, multiplied by the calorific value, gives the energy flow supplied to the engine.

(13) In FIG. 3 is shown in a schematic cross section of a gas valve 1 with a gas feed 10 for combustion gas as well as a mixing chamber 16, which is set immediately upstream of a cylinder, not shown in detail, of a gas engine or dual-fuel engine. In the gas feed 10, the combustion gas G is at a gas pressure p.sub.1. In the mixing chamber 16 there is a boost pressure p.sub.2, which depends on the respective currently requested operating point of the gas engine or dual-fuel engine. In the mixing chamber 16 is combustion air L, which is sucked, via the engine intake valves (not shown), into the combustion chamber of the cylinder or the engine together with the combustion gas G, as required, supplied via the gas valve 1 during operation of the gas engine or dual-fuel engine.

(14) The gas valve 1 has a substantially cylindrical housing 14, in which a poppet valve 11 is displaceable along the cylinder axis via an actuator 2 and can be adjusted from a closed position, as shown in FIG. 3, into an open position (in FIG. 3 shifted upward). Here the poppet valve 11 is connected with the actuator 2 via a shaft 13 located in the cylinder axis. Further, on the shaft 13 an opposing piston 12 is arranged, which is mounted also sealingly in the housing 14 and in its displacement from the closed position to the open position in the housing 14 is guided sealingly. The housing 14 of the gas valve 1 is however designed so that the gas pressure p.sub.1 pressing on the poppet valve 11 from above also presses on the opposite piston 12 from the bottom. Because the opposing piston 12 in the embodiment of FIG. 3 is only slightly smaller than the poppet valve 11, the pressure forces caused by the gas pressure p.sub.1 on the gas valve 1 are essentially balanced. On the opposite sides of the poppet valve 11 and the opposing piston 12 there act opposing pressure forces of the boost pressure p.sub.2, so that these also substantially balance. This constitutes a pressure-balanced valve 1.

(15) To open the valve, the actuator 2 thus requires only a relatively small force on the shaft 13 acting upwards in drawing plane according to FIG. 3. Due to the slightly smaller opposing piston 12 in contrast to the poppet valve 11, however, when opening the valve 1 a force in the direction of the closed position is always to be overcome, since the gas pressure p.sub.1 is always greater than the boost pressure p.sub.2. In so far, the pressure-balanced valve 1 is slightly loaded in its closed position by p.sub.1>p.sub.2.

(16) In the second exemplary embodiment according to FIG. 4, in which the same effective components are referred to with the same reference numerals, the gas valve 1 is also designed as a poppet valve 11 with opposing piston 12, guided in a housing 14. In this embodiment, although the diameter of the poppet valve 11 is again slightly larger than the opposing piston 12, however this valve 1 has next to the actuator 2 a spring 21 seated on the shaft 13, which as a pre-loaded pressure spring urges the shaft 13 with opposing piston 12 and poppet valve 11 downwards in the plane of drawing in FIG. 4. This design ensures that even at approximately the same gas pressure p.sub.1=boost pressure p.sub.2 the gas valve 1 remains in its closed position. When the valve is actuated via actuator 2 this causes the actuator to open the gas valve 1 by lifting the shaft 13 against the pressing forces acting on poppet valve 11 and opposing piston 12 (approximately balanced pressure relief) and the force of the spring 21.

(17) In FIG. 5 there is shown a third embodiment of the invention with a gas valve 1, which has shaft 13 extending through both sides by the housing 14 of the gas valve 1. Here on both sides of the housing 14, on the outwardly protruding ends of the shaft 13, respectively, an actuator 2, 2′ is provided, which together can switch the shaft 13 from the closed position into the open position and back again. Otherwise, the gas valve 1 is equipped, as in the embodiments 1 and 2 as shown in FIGS. 3 and 4, with a poppet valve 11 and the opposing piston 12.

(18) In FIG. 6 a fourth embodiment of a gas valve 1 is shown on a gas engine or dual-fuel engine, in which in the housing 14 of the gas valve 1 is a pressure diaphragm 15 is arranged so that the pressure diaphragm 15 faces the poppet valve 11 and is anchored at its outer circumferential edge in the housing 14, whereas the pressure diaphragm 15 communicates in the center with the shaft 13. With appropriate pressure difference between p.sub.1 and p.sub.2 with p.sub.1>p.sub.2 thus on the one hand forces act on the poppet valve 11 from top to bottom and via the pressure diaphragm 15 from the bottom to the top in drawing plane of FIG. 4, which compensate each other exactly due to the matching areas. Analogously, on the opposite sides of the pressure diaphragm 15 or the poppet valve 11 the boost pressure p.sub.2 acting in opposite directions is likewise effective to also balance. Thus, there is a pressure-balanced valve 1, which can be positioned in the open position or the closed position via the actuator 2 with relatively small actuating forces. In order to achieve a preload in the direction of the closed position there is also arranged a compression spring 21 on the shaft 13 between the housing and the pressure diaphragm 15. The overall force acting on the valve seat 17 via the shaft 13 and poppet valve 11 is thus essentially caused by the compression spring 21. Accordingly, the actuating force of the actuator 2 can be coordinated with the counterforce of the compression spring 21.

(19) In FIG. 7 a fifth embodiment of a gas valve 1 on a gas engine or dual-fuel engine is shown, in which within the housing 14 of the gas valve 1 again a poppet valve 11 and an opposing piston 12 are arranged on a common shaft 13, which provides a pressure relief on the valve 1 between the combustion gas G which is under a pressure p.sub.1 and the combustion air L under the lower pressure p.sub.2. In contrast to the embodiments one, two and three, however, the shaft 13 of the gas valve 1 is not actuated directly by an actuator. Rather, in the fifth embodiment an auxiliary actuator 22 is provided, which actuates an auxiliary valve 23. The auxiliary valve 23 has a valve block 24, which in its resting position, as shown in FIG. 7, allows a fluid connection from the mixing chamber 16 with the combustion air L located there to the top of the opposing piston 12 and thus creates a pressure compensation at the gas valve 1. Due to the slightly larger area of the poppet valve compared to the opposing piston, the gas valve 1 lies with a small force against the seat in its closed position.

(20) If then the auxiliary actuator 22 is energized and the auxiliary valve 23 with its valve block 24 shifted to the right (in the drawing plane of FIG. 7), the space above the opposing piston 12 is pressure relieved via the then newly created fluid connection to a reduced pressure p.sub.3, for example, the ambient pressure. This eliminates the approximate pressure balancing at the gas valve 1, so that the gas valve 1 opens out of the closed position.

(21) Next the auxiliary valve 23 is again adjusted to its resting position via auxiliary actuator 22, pressure (p.sub.2) acting at the moment in the mixing chamber 16 builds again on the top of the opposing piston 12, so that due to the slightly larger effective area of the poppet valve 11 compared to the opposite piston 12 the valve 1 closes again. Optionally, the closing of the gas valve 1 is supported by a pressure-tension spring or torsion spring in the direction of the closed position, which is however not explicitly shown in FIG. 7.

(22) In all five embodiments no gas control system is provided in the gas feed 10 upstream in the figures. The gas pressure p.sub.1 of the combustion gas G does not need to be adjusted against the ever-changing boost pressure p.sub.2 due to the effective pressure relief of the gas valve 1. In that regard, a gas pressure control for supplying gas engines or dual-fuel engines, as has been done so far, is not required especially with the pressure-balanced gas valve 1. In the gas feed, of course a gas filtration and optionally a safety shutoff may be provided. In that regard—according to the mandated safety regulations and the quality of gas being processed—although a pretreatment of the gas and a possible safety shutoff may be provided, however, a gas pressure control in dependence on in the gas engine or dual-fuel engine existing boost pressure and operating condition is not required. This considerably simplifies the operation of the gas engine or dual-fuel engine, reduces the maintenance time and effort and improves the reliability of the gas engine or dual-fuel engine during gas operation, so that any redundancies prescribed in the case of, for example, marine drives for safety reasons may no longer be necessary.

LIST OF REFERENCE NUMBERS

(23) 1 gas valve, pressure-balanced valve 10 gas feed 11 poppet valve 12 opposing piston 13 shaft 14 housing 15 pressure diaphragm 16 mixing chamber 17 valve seat 2, 2′ actuator 21 spring 22 auxiliary actuator 23 auxiliary valve 24 manifold G combustion gas L combustion air p.sub.1 gas pressure p.sub.2 air boost pressure p.sub.3 reduced pressure, ambient pressure