Split-cycle engine

Abstract

To provide a split cycle internal combustion engine capable of improving the efficiency and reducing NOx.SOLUTION: A split cycle internal combustion engine comprises a compression cylinder 10, a combustion cylinder 20, a crossover passage 30 for supplying working fluid to the combustion cylinder, a suction valve 18 for controlling a flow of the working fluid flowing from the crossover passage to the combustion cylinder, and a controller 60 disposed to receive at least one value of the pressure and temperature of the working fluid in the crossover passage. The controller is configured to, based on the received value, control the pressure and / or the temperature of the working fluid so that the working fluid flows in the combustion cylinder at a speed exceeding a speed threshold, in response to determination that the pressure and / or the temperature of the working fluid in the crossover passage is less than an input threshold.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present disclosure relates to a split cycle internal combustion engine and a method of operating a split cycle internal combustion engine.

Background Art

[0002] Conventional internal combustion engines operate based on the Otto cycle or the Diesel cycle. In these cycles, improvements in efficiency (i.e., performance) are, in principle, accompanied by an increased generation of exhaust gases of NOx, particulate matter, and carbon dioxide. In recent years, with the increasing concern about air pollution and global warming, regulations regarding exhaust gases have been continuously strengthened. Considering the above-mentioned engine cycles from this perspective, an improvement in cycle efficiency brings about a temperature rise and more NOx is formed. Therefore, performance is severely limited with respect to efficiency. In order to suppress the formation of NOx, post-treatment of exhaust gas has been proposed, but the complexity of the manufacturing process is inevitable.

[0003] For both the Otto cycle and the Diesel cycle, efficiency is based on the pressure at the end of compression. The efficiency of the Diesel cycle is also based on the combustion ratio because the rpm and the combustion ratio affect the volume ratio at the start and end of combustion. Therefore, improving the efficiency of conventional engines involves substantial significant limitations. This is because the peak temperature and pressure associated with the engine can reach very high levels.

[0004] The formation of NOx compounds occurs in regions where the temperature of the mixture of air and fuel rises above 2100K. For example, it may occur in local "hot spots" or, on a larger scale, throughout the entire engine cylinder. NOx compounds are related to health problems in the human respiratory system, and the generation of these compounds and their emission into the atmosphere pose important health risks. Also, the formation of these compounds is endothermic and is essentially useless with respect to maximizing the conversion of chemical energy into power.

[0005] UK Patent Application No. 1622114.5, UK Patent Application No. 1706792.7, and UK Patent Application No. 1709012.7 disclose a split-cycle internal combustion engine that uses a coolant injector for a cryogenic fluid (a fluid condensed into a liquid phase by a refrigeration process). [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] UK Patent Application No. 1622114.5 [Patent Document 2] UK Patent Application No. 1706792.7 [Patent Document 3] UK Patent Application No. 1709012.7 [Overview of the project]

[0007] Aspects of the present invention are shown in the independent claims, and optional features are shown in the dependent claims. Aspects of the present invention may be used in combination with each other, and features of one aspect may be applied to other aspects.

[0008] Herein, embodiments of the present disclosure will be described as examples with reference to the attached drawings below. [Brief explanation of the drawing]

[0009] [Figure 1] This is a schematic diagram of an exemplary split-cycle internal combustion engine. [Figure 2] This is a schematic diagram of an exemplary split-cycle internal combustion engine. [Figure 3] This is a temperature entropy diagram illustrating the operation of an exemplary split-cycle internal combustion engine. [Figure 4] Figure 3 is a temperature entropy diagram with isobars added to the graph. [Figure 5] This graph shows example scenarios for the use of a split-cycle internal combustion engine, based on the equivalence ratio, start temperature, and end temperature. [Figure 6]This flowchart illustrates an example of how to operate a split-cycle internal combustion engine. [Figure 7] This flowchart illustrates an example of how to operate a split-cycle internal combustion engine. [Figure 8] This flowchart illustrates an example of how to operate a split-cycle internal combustion engine. [Figure 9] This flowchart illustrates an example of how to operate a split-cycle internal combustion engine. [Figure 10] This flowchart illustrates an example of how to operate a split-cycle internal combustion engine. [Figure 11] This flowchart illustrates an example of how to operate a split-cycle internal combustion engine. [Figure 12] This flowchart illustrates an example of how to operate a split-cycle internal combustion engine. [Modes for carrying out the invention]

[0010] In one example, a split-cycle internal combustion engine is disclosed, comprising a controller configured to control the cooling system so that the peak combustion temperature in the combustion cylinder falls below a selected threshold. The controller may also control the peak combustion temperature to suppress the generation of NOx and particulate matter during combustion. This control is clearly environmentally beneficial, as these chemicals are known to be harmful to human health.

[0011] In one example, a split-cycle internal combustion engine is disclosed, comprising a controller configured to control the opening and closing of an intake valve that controls the flow of working fluid to a combustion cylinder. The controller may control the intake valve to open and close at selected timings to control the peak temperature of combustion in order to suppress the generation of NOx and particulate matter during combustion. This control is clearly environmentally beneficial, as these chemicals are known to be harmful to human health.

[0012] In one example, a split-cycle internal combustion engine is disclosed, comprising a controller configured to control a reactivity regulator that adjusts the reactivity of the fuel based on received engine operating condition instructions. The controller may control the reactivity regulator to increase the fuel reactivity when the fuel reactivity is low. This allows for improved efficiency because combustion of the fuel can be achieved at a higher fuel ratio.

[0013] In one example, a split-cycle internal combustion engine is disclosed, comprising a controller configured to control the injection timing of a fuel injector that injects fuel into a combustion cylinder. The controller may control the injector timing to control the peak combustion temperature in the combustion cylinder. This makes it possible to achieve a lower peak temperature, allowing the controller to suppress the generation of NOx and particulate matter during combustion. This has a clear environmental benefit, as these chemicals are known to be harmful to human health.

[0014] In one example, a split-cycle internal combustion engine is disclosed, comprising a controller configured to control the cooling system based on an estimate of the peak combustion temperature, such that the peak combustion temperature falls within a selected range. This may enable the controller to prevent the engine from operating at temperatures high enough to release NOx and particulate matter during combustion. Furthermore, it may enable the engine from operating at temperatures low enough to degrade engine performance.

[0015] In one example, a split cycle internal combustion engine is disclosed that includes a controller configured to control a cooling system such that a working fluid within a crossover passage flows into a combustion cylinder at a speed that exceeds a speed threshold. Thereby, better mixing of fuel and the working fluid becomes possible prior to combustion. Thereby, the richness of the fuel can be reduced, and as a result, a leaner air-fuel mixture is achieved such that the fuel burns completely and the generation of particulates such as soot is suppressed. Further, the occurrence of "hot spots" where combustion occurs at a higher peak temperature, generating undesirable pollutants such as NOx, can be reduced.

[0016] In one example, a split cycle internal combustion engine is disclosed that includes a controller configured to control the cross-sectional area defined by an intake valve to a combustion cylinder such that a working fluid flows into the combustion cylinder at a speed that exceeds a speed threshold. Thereby, better mixing of fuel and the working fluid becomes possible prior to combustion. Thereby, the richness of the fuel is reduced, and the occurrence of "hot spots" where NOx or particulates are generated by combustion can be reduced.

[0017] FIG. 1 shows a first example of a split cycle internal combustion engine 100 arranged to control the peak temperature of combustion so as to be below a selected threshold. The engine 100 is arranged to provide an indication of the peak temperature of combustion to a controller 60. The controller 60 determines the peak temperature of combustion based on the indication. Based on the determined peak temperature of combustion, the controller 60 controls a cooling system to adjust the temperature of the working fluid supplied to the combustion cylinder 20 of the engine 100. In particular, the cooling system is arranged to control this temperature such that the working fluid in the crossover passage 30 between the compression cylinder 10 and the combustion cylinder 20 of the engine 100 becomes sufficiently cold when used in the combustion cylinder 20 as part of the combustion process, and the peak temperature of combustion does not exceed the selected threshold. The controller 60 may operate based on a feedback loop that controls the operation of the cooling system such that the temperature of the working fluid supplied to the combustion cylinder 20 can be controlled within a selected range. Thereby, control of the peak temperature of combustion may be enabled, for example, such that the generation of NOx compounds can be suppressed. The feedback loop may be based on a cooling threshold, and in response to a determination by the controller that the peak temperature of combustion is below the cooling threshold, the controller adjusts the temperature of the working fluid to control the cooling system such that the peak temperature of combustion exceeds the cooling threshold. Thereby, the controller may be able to control the engine to operate within a selected peak temperature range.

[0018] As shown in the figure, Figure 1 shows the apparatus of a split-cycle internal combustion engine 100 comprising a compression cylinder 10 and a combustion cylinder 20. The compression cylinder 10 houses a compression piston 12 connected to each crank on a portion of the crankshaft 70 via a connecting rod 52. The combustion cylinder 20 houses a combustion piston 22 connected to each crank on a portion of the crankshaft 70 via a connecting rod 54. The compression cylinder 10 is connected to the combustion cylinder 20 via a crossover passage 30. The crossover passage 30 may include a recuperator which can be used for heat conduction. The compression cylinder 10 includes an intake port 8 that receives fluid from outside the engine 100 and an outlet port 9 connected to the crossover passage 30. The outlet port 9 is equipped with a valve, for example, a backflow prevention valve, to prevent the compressed fluid from flowing back into the compression cylinder 10. The combustion cylinder 20 includes an intake valve 18 connected to the crossover passage 30 and an exhaust valve 19 that allows exhaust gas to pass from the combustion cylinder 20 to the exhaust port. These connections constitute a fluid flow path between the compression cylinder 10 and the combustion cylinder 20 via the crossover passage 30.

[0019] The engine 100 further comprises a cooling system. The cooling system is illustrated to include a coolant reservoir 40 connected to the compression cylinder 10 via a coolant injector 14 that defines a fluid passage. The cooling system may further include an injector that injects coolant into a crossover passage 30, although this is not shown in Figure 1. The cooling system may include the use of heat conduction via a recuperator. For example, this may include the utilization of heat at the exhaust port from the combustion cylinder to heat the recuperator. This may include the utilization of a recuperator to transfer heat escaping from the split-cycle internal combustion engine 100. The engine 100 may further comprise a fuel reservoir 80 connected to the combustion cylinder 20 via a fuel injector 82 such that a fluid passage is defined between the fuel reservoir 80 and the combustion cylinder 20.

[0020] The engine 100 comprises a controller 60 and a number of sensors, shown by black dotted lines, connected to the controller 60. However, the sensors shown are illustrative only, and it should be understood that a different number of sensors may be provided and that they may be located in different places. For example, the intake port 8 may further include a temperature sensor. The sensors may be coupled to the controller 60 via physical wiring or may be wirelessly connected. In the example shown in Figure 1, a compression sensor 11 is located in the compression cylinder 10. The compression sensor 11 may be located, for example, near the intake port 8 or near the coolant injector 14. The compression sensor 11 may also include a temperature sensor. The exemplary engine 100 shown in Figure 1 further includes a combustion sensor 21 in the combustion cylinder 20. The compression sensor 21 may also include a temperature sensor and may also include a pressure sensor. Furthermore, a crossover sensor 31 in the crossover passage 30 is shown. The crossover sensor 31 may also include a temperature sensor and may also include a pressure sensor. Furthermore, the engine 100 includes a crank sensor 71 mounted on the crankshaft 70. The crank sensor may provide an indication of torque requests from the engine. Additionally, an exhaust sensor 91 is shown downstream of the exhaust valve 19 of the combustion cylinder 20. The exhaust sensor 91 may include a temperature sensor, a pressure sensor, or a lambda sensor configured to provide an indication of the NOx concentration in the engine exhaust. In some examples, the coolant reservoir 40 may further include sensors that measure quantities, such as mass, of the liquid contained in the reservoir 40. The controller 60 is further coupled to the coolant injector 14 and the fuel injector 82 and / or the reservoir 80.

[0021] Multiple sensors are configured to transmit at least one signal to the controller 60, providing an indication of at least one parameter associated with the engine 100. The engine 100 parameter may include the temperature of the working fluid within the engine (e.g., at different locations such as the exhaust, compression cylinder 10, and crossover passage 30). This may include the pressure of the working fluid within the engine, the demands on the engine, the value of NOx generation within the engine, the timing of opening and closing the intake valve 18, and the timing of fuel injection into the combustion cylinder. The engine 100 parameter may also include an indication of engine knocking, which may, for example, be based on a received audio signal of engine operation. Engine knocking can occur when fuel is not ignited at the appropriate timing during the piston cycle and may be detected based on listening to engine noise; the engine knocking indication may be considered an engine parameter.

[0022] For example, in the example shown in Figure 1, the compression sensor 11 is configured to measure at least one parameter associated with the compression cylinder 10. The combustion sensor 21 is configured to measure at least one parameter associated with the combustion cylinder 20. The crossover sensor 31 is configured to measure at least one parameter associated with the crossover passage 30. Furthermore, the crank sensor 71 is configured to measure the RPM of the engine 100, and the exhaust sensor 91 is configured to measure at least one parameter of the exhaust gas discharged from the exhaust valve 19 of the combustion cylinder 20. Measuring at least one parameter in this way provides an indication of the peak temperature of combustion in the combustion cylinder 20. Each sensor may provide the controller 60 with the indication of the peak temperature so that the controller 60 can determine the peak temperature of combustion in the combustion cylinder 20.

[0023] The engine 100 is configured such that air is drawn into the compression cylinder 10 through the intake port 8 of the compression cylinder 10. A compression piston 12 is positioned to compress this air, and coolant may be added to the compression cylinder 10 during the compression phase. A crossover passage 30 is positioned to receive the working fluid through the outlet 9 and send it to the combustion cylinder 20 through the intake valve 18. The engine 100 is further configured to add fuel from the fuel storage unit 80 to the working fluid in the combustion cylinder 20 via a fuel injector 82, burn the mixture of fuel and working fluid (for example, by the operation of an ignition source not shown), and extract effective power through the rotation of the crankshaft 70.

[0024] The fuel storage unit 80 is connected to the controller 60 so that the controller 60 controls the supply of fuel to the combustion cylinder 20. In some examples, the controller 60 is configured to determine the amount of fuel to be injected based on instructions for at least one engine parameter 100 received. For example, the controller 60 may be configured to obtain instructions for at least one parameter, such as an instruction signal for the peak combustion temperature received from the exhaust sensor 91, or an instruction signal for engine requests received from the crank sensor 71.

[0025] During operation, the controller 60 is configured to receive an indication of the peak combustion temperature. The signal is received from at least one of the multiple sensors shown in Figure 1. For example, the controller 60 may receive an indication of the exhaust temperature from the exhaust sensor 91. If the controller receives an indication from a sensor that does not directly measure the peak combustion temperature, the controller determines an estimate of the peak combustion temperature in the combustion cylinder 20 based on this received indication. For example, an indication of the temperature in the exhaust received may be used to estimate the peak combustion temperature in the combustion cylinder. If the controller receives an indication from a sensor that directly measures the peak combustion temperature (e.g., the combustion sensor 20), the controller may use this peak temperature indication rather than determining the peak temperature individually.

[0026] The peak temperature of combustion typically occurs towards the end of the piston 22's movement from top dead center (TDC) to bottom dead center (BDC). If the controller 60 receives an indication from a sensor that cannot directly measure this peak temperature (e.g., a sensor not located inside the combustion cylinder 20), the controller 60 may be configured to determine an estimate of the peak temperature based on the received indication. This may involve using a mathematical model capable of estimating the peak temperature of combustion based on values ​​of engine parameters (e.g., the temperature of the working fluid in the crossover passage). For example, such a model may involve determining values ​​based on historical data for heat generation throughout the engine cycle and / or heat dissipation and resulting cooling after combustion has occurred. The sensor may measure system and / or working fluid parameters (e.g., temperature, pressure), which may also be indications provided to the controller 60. Based on these indications, the controller 60 may use known thermodynamic relationships to determine an estimate of the peak temperature inside the combustion cylinder 20. For example, the concentration of the working fluid may be determined based on the received pressure and temperature indications of the working fluid (for example, based on a state equation that links pressure, temperature, and concentration).

[0027] In one example, the controller 60 may receive an indication of the peak combustion temperature from a sensor that measures parameters of the working fluid after combustion. For example, this measurement may be performed by an exhaust sensor 91. The exhaust sensor 91 may be configured to measure the temperature of the working fluid in the exhaust. The post-combustion temperature provides an indication of the peak combustion temperature. An estimate of the peak combustion temperature may be determined based on past data, for example, post-combustion temperatures using a lookup table. It will be understood that this can provide a value very close to the peak temperature of the working fluid during combustion, since the point in time when the working fluid passes from the combustion cylinder 20 through the exhaust valve 19 is immediately after the point in time when the peak combustion temperature is reached. Therefore, the exhaust sensor 91 may measure the post-combustion temperature and, based on this measurement, provide the controller 60 with an indication of the peak combustion temperature. The controller 60 then measures the peak combustion temperature based on the post-combustion temperature. The peak combustion temperature is higher than the post-combustion temperature. The peak combustion temperature may be determined using a lookup table that includes the correlation between the post-combustion temperature value and the corresponding peak combustion temperature value.

[0028] In another example, the controller 60 may receive an indication of the peak combustion temperature from a sensor that measures the working fluid parameters before combustion. For example, this measurement may be performed by a supply sensor, where the supply sensor refers to any sensor that provides engine parameters or an indication of the working fluid before combustion, for example, the indication may come from the compression sensor 11 or from the crossover sensor 31. The crossover sensor 31 may be configured to measure the temperature of the working fluid in the crossover passage 30 before it flows into the combustion cylinder 20. The crossover sensor 31 may therefore measure the temperature of the working fluid before combustion and provide an indication of this temperature to the controller 60. The controller 60 then determines an estimate of the peak combustion temperature in the combustion cylinder 20 based on the pre-combustion temperature. The pre-combustion temperature is lower than the peak combustion temperature. The controller 60 may determine the estimate of the peak combustion temperature using a lookup table that includes a correlation between the pre-combustion temperature value and the corresponding peak combustion temperature value. The correlation value may be determined using a mathematical model that models the thermodynamics of the system for temperature prediction. This value may include values ​​determined empirically.

[0029] It will be understood that the lookup tables used in any of the examples may also include other parameters. The lookup tables may enable the controller 60 to determine an estimate of the peak combustion temperature based on the current conditions of the engine 100 and the working fluid temperature (e.g., pre-combustion or post-combustion temperature). For example, one of the other parameters may include an instruction for a request to the engine 100, which can be determined based on a signal received from the crank sensor 71. One parameter may include a timer indicating the period during which the engine 100 is operating. This may include an instruction for the engine temperature, which will be lower during engine startup and while the engine is warming up. Therefore, the time the engine is operating may provide an instruction for the expected temperature of the engine itself. One parameter may include an instruction for the overall temperature of the engine 100. It will be understood that the other parameters may include any appropriate parameters that may affect the determination of the peak combustion value in the combustion cylinder 20. For example, during engine 100 startup, the combustion cylinder 20 is colder than during normal operation, and the rise in working fluid temperature between the pre-combustion temperature and the peak combustion temperature may be smaller than when the combustion cylinder 20 becomes hot after prolonged use or under high demand. Based on the temperature indicator of the engine 100 (e.g., the combustion cylinder 20), or based on a timer indicating how long the engine 100 has been running, for example, a correlation from the pre-combustion temperature to the peak combustion temperature may provide a more accurate estimate of the peak combustion temperature in the combustion cylinder 20.

[0030] The controller 60 is configured to control the cooling system to cool the working fluid in response to a determination that the working fluid temperature exceeds a selected threshold. During engine 100 startup, the engine 100 operates at a lower temperature, and therefore the controller 60 may determine that the estimated peak combustion temperature is considerably lower than the selected threshold. In this case, the controller 60 may control the cooling system so that little or no cooling is performed.

[0031] When the engine 100 moves from the starting state to the normal operating mode, the controller 60 is configured to determine the peak combustion temperature and control the cooling system to adjust the working fluid temperature. The control of the cooling system is based on a feedback loop that includes routine monitoring of the peak combustion temperature and working fluid cooling control, ensuring that the peak combustion temperature does not exceed a selected threshold. In response to the determination that the peak combustion temperature exceeds a selected threshold, the controller 60 is configured to activate the cooling system to improve the cooling of the working fluid. In the example shown in Figure 1, this includes controlling the coolant injector 14 to inject more coolant into the compression cylinder 10. However, it will be understood that other methods of controlling the working fluid temperature (e.g., by heat conduction using a recuperator) may also be provided. When the working fluid in the compression cylinder 10 is compressed, some of the rise in the working fluid's temperature may be absorbed by the injected coolant. The coolant absorbs a certain amount of heat to overcome the latent heat of evaporation, which acts to suppress the rise in temperature in the combustion cylinder 20. Therefore, the controller 60 can control the heat of the working fluid by controlling the amount of coolant injected into the combustion cylinder 20. In particular, the controller 60 can influence the heat of the working fluid in the crossover passage 30 before it flows into the combustion cylinder 20.

[0032] The selected threshold includes a criterion for the peak temperature of combustion. The controller may determine whether the criterion is met based on a comparison that includes the estimated peak temperature of combustion and the criterion. The selected threshold may also be a maximum temperature value, such that a peak temperature of combustion above this maximum temperature does not meet the criterion. The value of the selected threshold may be chosen to suppress the formation of NOx compounds. The controller may also compare the value of the peak combustion temperature to the selected threshold, and this comparison is based on the average value of the peak temperatures of combustion, i.e., the "inclusive" value of the peak temperatures of the entire cylinder. In other examples, the controller may also compare the value of the peak combustion temperature to the selected threshold, and this comparison is based on the local peak value of the peak temperature of combustion. The local peak value may include the value of the highest peak temperature of combustion in any region of the combustion cylinder 20. In some examples, the selected threshold may include indications for both values. The selected threshold may be a temperature of 2200 Kelvin or less, less than 2150 Kelvin, less than 2125 Kelvin, less than 2100 Kelvin, less than 2075 Kelvin, less than 2050 Kelvin, less than 2000 Kelvin, or less than 1900 Kelvin. It will be understood that this value may be determined by the equivalent ratio of the mixture of the working fluid and the fuel, and therefore may vary.

[0033] The controller 60 controls the cooling system to adjust the temperature of the working fluid supplied to the combustion cylinder 20 in response to a determination that the peak combustion temperature exceeds a selected threshold. As previously stated, the temperature is adjusted using the cooling system. In one example, this may be done by increasing the amount of coolant injected into the compression cylinder 10, or, in addition to or instead of this, by controlling heat conduction away from the recuperator in the crossover passage. The controller 60 may be configured to determine the degree of cooling based on the determined peak combustion temperature indication. The cooling system may be operated continuously such that the amount of injected coolant is proportional to the amount of cooling required to cool the working fluid temperature to below a selected threshold. The cooling system may also be operated individually such that a first amount of coolant is injected above a first selected threshold, and a second amount of coolant is injected above a second selected threshold. There may be multiple such thresholds.

[0034] The controller 60 may control the split-cycle internal combustion engine 100 so that the combustion process is carried out at a lower temperature to reduce the generation of NOx compounds, by controlling the cooling system to adjust the peak combustion temperature in the combustion cylinder 20.

[0035] While the controller is described as controlling the cooling system to inject more coolant, it will be understood that similar results can be achieved by other means. For example, this could be achieved by injecting a different type of coolant or by injecting the coolant at a different temperature. Furthermore, it will be understood that the sensor is configured to provide the controller 60 with an indication of the peak temperature of combustion. However, this indication does not necessarily have to include temperature, but could include the measurement of any suitable thermodynamic parameters from which the peak temperature of combustion can be determined. For example, the temperature value may be determined from the pressure value using a known thermodynamic relationship.

[0036] In another embodiment, the split-cycle internal combustion engine 100 of Figure 1 may operate to regulate the temperature of the working fluid in the combustion cylinder 20 using the timing of the intake valve 18. The intake valve 18 is operable to move from a closed position in a first position during the piston cycle to an open position in a second position during the piston cycle. When the intake valve 18 is open, the working fluid in the crossover passage 30 flows into the combustion cylinder 20, and when the intake valve 18 is closed, no working fluid flows in. During operation, the controller 60 may select the first and second positions based on selected thresholds and / or cooling thresholds. These two positions may be selected so that they are separated by a selected period, which may be fixed as a constant and / or variable. Combustion in the combustion cylinder 20 typically occurs at or near the TDC position of the piston during the cycle. Therefore, the first position is selected to be before TDC so that there is time for the working fluid in the crossover passage 30 to flow into the combustion cylinder 20 before combustion occurs. The second position may be selected to be at or before TDC so that a greater force is applied to the piston by combustion. This is because the expansion of the working fluid during combustion moves the combustion piston 22 to the BDC position. If the intake valve remains open during combustion, some of the working fluid may flow back into the crossover passage rather than apply a greater force to the combustion piston 22. Therefore, if the second position is selected so that the intake valve closes before the expansion of the working fluid occurs, a greater force is supplied to the combustion piston 22.

[0037] Since the first position is before TDC, the working fluid in the combustion cylinder 20 is compressed somewhat before combustion occurs. This causes the temperature of the working fluid to rise. Since the temperature of the working fluid before combustion affects the peak combustion temperature in the combustion cylinder 20, the controller 60 can adjust the peak combustion temperature in the combustion cylinder 20 by controlling the temperature rise in the combustion cylinder 20 caused by this compression. The amount of temperature rise caused by the compression in the combustion cylinder 20 is determined by the first position. The closer the first position is to BDC, the greater the amount of heating of the working fluid. Therefore, the controller 60 may select the first position based on a determined required amount of heating. This may be determined based on the determined peak combustion temperature in the combustion cylinder 20, and therefore, the working fluid is additionally heated by a desired amount to reach the selected temperature before combustion so that the peak combustion temperature falls within the selected range.

[0038] For example, in response to a determination that the estimated peak combustion temperature exceeds a selected threshold, the controller 60 selects a first position that is further back in the piston's cycle. In response to a determination that the peak combustion temperature falls below a cooling threshold, the controller 60 selects a first position that is further forward in the piston's cycle so that the working fluid can receive more heat. Similarly, the controller 60 may control a second position based on the peak combustion temperature, the cooling threshold, and a selected threshold.

[0039] In another embodiment, the split-cycle internal combustion engine 100 of Figure 1 may operate using the timing of fuel injection by the fuel injector 82 to regulate the temperature of the working fluid in the combustion cylinder 20. Fuel injection may occur at injection positions during the piston cycle. This injection may occur over a set period of time or over a variable period of time, which may be based on the amount of fuel injected. The controller 60 is configured to select an injection position based on a determined estimate of the peak combustion temperature. For example, the controller 60 may control the fuel injector 82 to inject fuel at a delayed injection position during the piston cycle in response to a determination of an estimate of the peak combustion temperature above a selected threshold. Delayed injection positions may include positions during the piston cycle that are behind the current injection position. The controller 60 may control the fuel injector 82 to inject fuel at an early injection position during the piston cycle in response to a determination of an estimate of the peak combustion temperature below a cooling threshold. Early injection positions may include positions during the piston cycle that occur before the current injection position.

[0040] Typically, combustion occurs at or immediately after the TDC position of the combustion piston 22. By controlling combustion to occur at the TDC position, a longer-lasting expanding force is exerted on the combustion piston 22 as it returns to its BDC position. The volume of the combustion cylinder 20, defined by the position of the combustion piston 22, changes during the piston stroke and is minimum at the TDC position of the combustion piston 22. Combustion at this TDC position can result in a greater expansion of the working fluid compared to combustion at a later position in the piston cycle. Combustion near TDC can result in a greater temperature change from the starting temperature compared to combustion after TDC. As a result, the peak temperature of combustion in the combustion cylinder 20 may be higher than that of combustion that starts earlier. Combustion does not occur without fuel.

[0041] The controller 60 is configured to control the fuel injector 82 so that fuel is injected into the combustion cylinder 20 at the injection position during the piston cycle. The controller may delay fuel injection so that it is injected at a later position in the piston cycle (for example, after TDC). Based on the determined estimate of the peak combustion temperature in the combustion cylinder 20, the controller may determine that the estimated peak temperature is too high and NOx may be generated. As a way to regulate the temperature in the combustion cylinder 20, the controller may delay fuel injection so that combustion occurs at a later position in the piston cycle. This can lower the peak combustion temperature and suppress NOx generation.

[0042] In another embodiment, the split-cycle internal combustion engine 100 of Figure 1 may operate with a controller 60 to control the cooling system to adjust the peak temperature of the working fluid supplied to the combustion cylinder 20 based on an estimate of the peak combustion temperature in the combustion cylinder 20. The controller 60 may use the estimate so that the peak combustion temperature in the combustion cylinder 20 falls within a selected range. In particular, during normal operation of the engine 100, the controller may select a selected range so that the peak combustion temperature in the combustion cylinder does not exceed a selected threshold and / or fall below a cooling threshold. The selected range may be selected to be within a range of values ​​between the cooling threshold and the selected threshold. This allows the controller 60 to control the operation of the engine so that both efficiency and NOx generation meet selected criteria.

[0043] The controller 60 may determine an estimate of the peak combustion temperature based on the received engine parameter instructions. For example, the controller 60 may determine the estimate based on the received engine request instructions. In this case, the controller 60 may predict an estimate of the peak combustion temperature to be reached in the combustion cylinder 20 based on the engine request instructions (e.g., instructions for the temperature of the working fluid supplied to the combustion cylinder 22).

[0044] This prediction may be based on historical data associated with the engine 100. For example, the controller 60 may access a lookup table containing correlations between one or more values ​​for at least one engine parameter and corresponding peak temperature estimates. The controller 60 may also include a machine learning element that has a model for predicting the peak combustion temperature based on input data about the engine (e.g., each engine parameter, or a log of engine measurements since the engine started). This machine learning element may be "trained" on data in which known peak combustion temperatures associated with the input data exist. This allows the predictive model of the machine learning element to learn and update based on the training data, potentially providing a more reliable and accurate system for predicting the peak temperature. Based on this estimate, the controller may control the cooling system so that the peak combustion temperature in the combustion cylinder 20 falls within a selected range.

[0045] The split-cycle internal combustion engine 100 in Figure 1 may also have its working fluid temperature adjusted according to the previously described example. The temperature adjustment may be based on a combination of the previously described example.

[0046] Figure 2 shows a second example of a split-cycle internal combustion engine 100 configured to control the combustion peak temperature so that it falls below a selected threshold. Since the engine 100 in Figure 2 is similar to the engine 100 in Figure 1, components that perform substantially the same function are indicated by the same reference numerals and their descriptions are omitted.

[0047] The split-cycle internal combustion engine 100 in Figure 2 further comprises a reactivity regulator 85. The reactivity regulator 85 is connected to the controller 60 so that the controller 60 can control the operation of the reactivity regulator 85. The reactivity regulator 85 is operable to regulate the reactivity of the fuel used during the combustion process. The reactivity regulator 85 is shown as operable to act on the fuel (e.g., in the fuel storage unit 80) injected into the combustion cylinder 20. The reactivity regulator 85 is further shown as operable to act directly on the fuel in the combustion cylinder 20. The reactivity regulator 85 is operable to improve the ignition ability of the fuel. This may include at least one of improving the reactivity of the fuel and providing an additional means for igniting the fuel in the combustion cylinder 20. The controller 60 may further control the operation of the reactivity regulator 85 in response to a determination that the reactivity of the fuel exceeds an over-reactivity threshold. This can contribute to suppressing NOx formation because over-reactive fuel can increase the peak combustion temperature.

[0048] In the illustrated example, the reactivity controller 85 includes a system for directing electromagnetic radiation (e.g., laser or microwave radiation) onto the fuel to provide an additional ignition source for the fuel in the combustion cylinder 20. This enables a more precise ignition mechanism, allowing ignition of the fuel even under undesirable ignition conditions, such as when the combustion cylinder 20 is below the ignition threshold temperature. The controller 60 may be configured to control the reactivity controller 85 to provide an additional ignition source for the fuel in response to a determination that the temperature in the combustion cylinder 20 and / or the working fluid temperature is below the ignition threshold. The reactivity controller 85 may include a selective energy transfer system. The selective energy transfer system may provide targeted radiation to certain compounds present in the fuel-working fluid mixture to improve the reaction rate. This may include targeted radiation to improved combustion by decomposing compounds (e.g., decomposing CH4 (methane)) so that combustion occurs at a lower onset temperature and the peak combustion temperature is lower, thereby suppressing NOx production.

[0049] In some examples, the reactivity regulator 85 may include a system for supplying an oxidizer or free radicals to the fuel. This supply may be supplied into the combustion cylinder 20 or into the fuel storage unit 80 (for example, before fuel is injected into the combustion cylinder 20). The supply of an oxidizer can improve the likelihood of initial fuel ignition by allowing a higher proportion of the fuel to ignite. For example, suitable oxidizers include oxygen or ozone, but it will be understood that any suitable oxidizer may be added.

[0050] The controller 60 is configured to receive at least one instruction of the working fluid's pressure, concentration, and temperature, and to determine the ignition parameter of the working fluid based on this instruction. The determined ignition parameter may provide an instruction of the fuel's ignition capability. For example, the ignition parameter may provide an instruction of the planned proportion of fuel to ignite. The controller 60 is configured to determine the ignition parameter based on the received instruction. For example, this may include using a lookup table to determine the value of the ignition parameter based on one or more values ​​of the working fluid's thermodynamic properties. These values ​​may be determined theoretically and / or empirically. For example, the controller 60 may determine that when the fuel is cold, the likelihood of ignition is low, and therefore, in response to receiving an instruction that the working fluid temperature is low, it may determine that the ignition parameter is a low value.

[0051] The controller 60 is configured to activate the reactivity regulator 85 in response to a determination that the ignition parameter is below the ignition threshold. The operation of the reactivity regulator 85 increases the value of the ignition parameter, thereby improving the likelihood of fuel ignition. The controller 60 may be configured to determine the degree of operation of the reactivity regulator 85 based on the determined ignition parameter. For example, the degree of operation of the reactivity regulator 85 may be determined based on the magnitude of the difference between the ignition parameter and the ignition threshold. There may be multiple ignition thresholds, and the controller 60 may determine the degree of operation of the reactivity regulator 85 based on which threshold the ignition parameter satisfies. The reactivity regulator 85 can be particularly useful when the ignition parameter is below or significantly below the ignition threshold, especially during engine 100 startup. For example, the temperature of the combustion cylinder 20 may be very low, and the operation of the reactivity regulator 85 allows fuel ignition and combustion to occur even at very low temperatures.

[0052] Figure 3 shows an exemplary temperature-entropy diagram of the operation of a split-cycle internal combustion engine as shown in Figure 1 or Figure 2. The dotted line represents the engine cycle without cooling, and the solid line represents the cycle with cooling. This figure is based on approximations of an engine using a nitrogen-only cycle. These cycles output the same amount of heat. In the cycle with added coolant, the lower left point shows lower values ​​for both temperature and entropy compared to the cycle without cooling. This is due to the increase in mass and decrease in temperature caused by the addition of coolant. Therefore, the upper right point of the cycle with cooling shows lower temperature and entropy than the cycle without cooling. This point indicates the peak temperature of combustion. Therefore, the amount of cooling may be controlled so that this peak temperature of combustion falls below a selected threshold. This suppresses NOx generation, while at the same time avoiding a decrease in engine efficiency because the same amount of heat is released. This is because the ratio of the initial pressure to the final pressure in the combustion cylinder can be the same for both the cycle with and without cooling, and the engine cycle efficiency is determined based on this ratio. The slope of the line extending from the top-left point to the top-right point in each cycle indicates the efficiency of the conversion from thermal energy to pressure. A gentler slope indicates higher conversion efficiency. As shown in Figure 3, cycles with cooling have a shallower slope, suggesting that the efficiency of the conversion from thermal energy to pressure may be higher.

[0053] Figure 4 shows an exemplary temperature entropy diagram of the operation of the split-cycle internal combustion engine shown in Figure 3, with isobars added. The isobars indicate that the ratio of the final pressure to the initial pressure of combustion is the same for both the cooled and uncooled cycles. As a result, both cycles operate at the same level of engine efficiency. However, the maximum combustion temperature can be lower because the temperature in the cooled cycle is controlled to be lower than that in the uncooled cycle. Furthermore, this can suppress the generation of NOx and / or particulate matter.

[0054] Figure 5 is a graph showing examples of different initiation temperatures and their corresponding final temperatures in the combustion correlation for N-dodecane, methane (CH4), and isooctane. The graph also indicates the equivalent ratios of each of these fuels at their initiation temperatures. Furthermore, the graph shows the region of final temperatures beyond which NOx is typically produced, with the line indicating a final temperature of approximately 2200 Kelvin. Typically, the temperature values ​​for NOx production are the same for each fuel listed herein. For example, the selected threshold may be chosen based on the typical temperature at which NOx production occurs. The graph further shows the region of initiation temperatures where complete combustion of the fuel typically occurs. As shown, this region extends from approximately 690 Kelvin to approximately 1600 Kelvin. For example, the cooling threshold may be chosen based on the lower end of the range in which complete combustion occurs. This is because if the combustion initiation temperature falls below this lower value, the fuel may not ignite and burn completely, resulting in inefficient combustion.

[0055] The graph shows that when N-dodecane is the fuel and the starting temperature range is from 690 Kelvin to 820 Kelvin, complete combustion can occur without reaching the final combustion temperature in the NOx range. The graph shows that this occurs over the equivalence ratio temperature range of 0.4–0.48. For equivalence ratios of 0.5 and 0.52, at lower starting temperatures within this temperature range, the final combustion temperature does not reach the NOx range. However, at higher starting temperatures, the final combustion temperature may reach the NOx range. As an example, with an equivalence ratio of 0.5 and a starting temperature of approximately 690 Kelvin, the final combustion temperature is approximately 2100 Kelvin, which is outside the NOx range. As another example, with an equivalence ratio of 0.5 and a starting temperature of 820 Kelvin, the final combustion temperature is approximately 2220 Kelvin, which is inside the NOx range. This shows that by controlling the starting temperature to stay within a certain range, it is possible to avoid the final combustion temperature entering the NOx range for a given equivalence ratio, and thus suppress NOx generation.

[0056] As shown in the graph, the equivalent ratio is the fuel-air equivalent ratio (φ). For dodecane, if the fuel-air equivalent ratio is 0.4, the air-fuel equivalent ratio (λ) is 2. The fuel-air equivalent ratio may be selected based on a lean threshold. The lean ratio may be defined based on the fuel-air equivalent ratio. For example, the lean threshold may be selected based on a fuel-air equivalent ratio of 0.4, which may be 0.42, 0.44, 0.46, 0.48, or 0.5. If the leanness of the fuel-working fluid mixture falls below a certain value, particulate matter formation may occur. The lean threshold may be selected based on this value. Particulate matter formation may include soot generation in the engine. The leanness of the working fluid-fuel mixture may be controlled so that the mixture is lean enough to avoid particulate matter formation. Typically, particulate matter formation occurs as a result of the "rich region" of the fuel, where the fuel is not mixed with enough oxygen and incomplete combustion occurs. Furthermore, combustion can be controlled to avoid the formation of compounds HC and CO (these usually make combustion inefficient). The equivalence ratio may be based on the local equivalence ratio, the average equivalence ratio for the combustion cylinder, or both.

[0057] In another embodiment, the engine 100 in either Figure 1 or Figure 2 may be configured such that the controller 60 controls at least one thermodynamic property of the working fluid in the crossover passage 30 so that the flow of working fluid into the combustion cylinder 20 meets selected criteria. In particular, the controller 60 is configured to control at least one of the pressure and concentration of the working fluid in the crossover passage 30 so that the working fluid flows into the combustion cylinder 20 at a velocity exceeding a velocity threshold. The velocity threshold is selected so that the working fluid flowing into the combustion cylinder 20 achieves a lean mixture of fuel and the working fluid in the combustion cylinder 20. For example, the working fluid may flow through the intake valve 18 at a velocity that generates a large amount of turbulence and results in a fast flow of fluid over the fuel injector 82. Once fuel is injected into the combustion cylinder 20, this fuel may be suitably dispersed according to the flow velocity of the working fluid. This can reduce the number of "fuel pockets" that burn at a higher temperature than the ambient temperature, and therefore reduce the amount of NOx and / or soot formed. Furthermore, this allows the fuel to react completely, leaving no pyrolysis products, and therefore a higher proportion of the fuel to be consumed to produce useful power.

[0058] During operation, the controller 60 is configured to receive an indication of at least one of the pressure and / or concentration of the working fluid in the crossover passage 30. This indication may be received from a crossover sensor 31, which may be configured to measure a suitable thermodynamic parameter from which the pressure and / or concentration can be determined. The controller 60 may determine the pressure and / or concentration using a lookup table or mathematical model that shows the correlation between the measured parameter and the corresponding value of pressure and / or concentration. The controller 60 is configured to compare this determined value with an input threshold. The input threshold may be a value of the measured parameter in the crossover passage that is expected to cause the working fluid to flow into the combustion cylinder at a speed above a speed threshold. Based on this comparison, the controller 60 is configured to control the pressure and / or concentration of the working fluid. The pressure and / or concentration of the working fluid is controlled so that the fluid flows into the combustion cylinder 20 at a speed above the speed threshold.

[0059] The velocity threshold is selected to be a velocity that causes turbulence in the fluid into and within the combustion cylinder 20 in order to achieve a lean mixture of fuel with the working fluid. The value of the velocity threshold may be determined based on the pressure and / or concentration of the working fluid in the crossover passage 30, and further based on the dimensions between the combustion cylinder 20 and the intake valve 18, and can be used to model the fluid flow into the combustion cylinder 20. Thus, the value of the velocity threshold is selected so that a lean mixture of fuel is achieved by the flow of working fluid into the combustion cylinder 20 at the velocity threshold. The lean mixture of fuel is selected so that complete combustion occurs and the generation of particulate matter is suppressed. Optionally, the degree of lean may be selected so that the ignition of the fuel occurs staggered over the combustion stroke period rather than all the fuel igniting at once, thereby allowing a more constant power output from the engine 100. For example, the speed threshold may be greater than 350 meters / second (m / s), 345 m / s, 343 m / s, 340 m / s, 335 m / s, 330 m / s, 325 m / s, 320 m / s, 310 m / s, or 300 m / s. However, it should be understood that this value can be very high or very low, as it depends on different engine parameters. For example, pressure or concentration can affect the speed threshold value. Typically, at these speeds, the fluid flow into the combustion cylinder 20 becomes a choke flow, which is a supersonic phenomenon that interferes with the working fluid flow into the combustion cylinder 20.

[0060] The input threshold is selected based on a velocity threshold and / or a selected level of turbulence within the combustion cylinder 20. For example, the input threshold may be selected based on empirical data and / or a mathematical model that provides indication of the associated level of turbulence within the combustion cylinder 20. The input threshold may be selected such that a working fluid having a pressure and / or concentration at the input threshold flows into the combustion cylinder 20 at the velocity threshold.

[0061] Controller 60 is configured to control the pressure and / or concentration of the working fluid in response to a determination that the pressure and / or concentration of the working fluid exceeds an input threshold. Controller 60 may also control the pressure and / or concentration of the working fluid using a cooling system. Controller 60 is configured to control the operation of the cooling system in response to a determination that the pressure and / or concentration falls below an input threshold. This may lower the temperature of the working fluid, allowing for greater pressure and / or higher concentration within the crossover passage 30. For example, in engine 100 at 973K and 7MPa, lowering the temperature to 700K results in a 40% increase in concentration. The degree of operation of the cooling system may be determined based on the degree of difference between the working fluid pressure and / or concentration and the input threshold. In the example in Figures 1 and 2, the cooling system includes a coolant injector 14 that injects coolant into the compression cylinder 10 of engine 100. The operation of this cooling system may include increasing the amount of coolant injected into the compression cylinder 10. The controller 60 may further control the amount of coolant injected based on the determined fluid pressure and / or concentration.

[0062] The increase in pressure within the crossover passage 30 increases the pressure difference between the crossover passage 30 and the combustion cylinder 20, and therefore, as the intake valve 18 to the combustion cylinder 20 moves to the open position, the flow of working fluid into the combustion cylinder 20 becomes faster. The increase in concentration increases the concentration of oxygen transporting the gas within the combustion cylinder 20. The increase in concentration further lowers the initial temperature of the working fluid within the combustion cylinder 20, reducing the possibility of NOx generation. This increase in concentration increases the mass of the gas, resulting in an increase in pressure during combustion and a suppression of the temperature rise. This reduces the peak temperature of combustion and thus suppresses the generation of NOx.

[0063] In another embodiment, the split-cycle internal combustion engine 100 may operate based on selected valve opening and closing timings. The valve opening and closing timings include timings associated with a first position in the piston cycle when the intake valve 18 moves from a closed position to an open position, and timings associated with a second position in the piston cycle when the intake valve 18 moves from an open position to a closed position. The first and second positions may be fixed so that the intake valve 18 moves to a selected position that is not controlled by the controller 60. Thus, the controller 60 may determine an input threshold based on the selected position. This includes determining a value for the input threshold based on the conditions of the engine 100 at each position so that, after the intake valve 18 has moved to an open position at the first position, the working fluid in the crossover passage 30 at the input threshold can flow into the combustion cylinder 20 at a speed faster than the speed threshold.

[0064] In another embodiment, the split-cycle internal combustion engine 100 may operate based on the control of the movement of an intake valve 18 relative to a combustion cylinder 20. The intake valve 18 may move from a closed state to an open state. Movement to the open state involves movement of the valve such that a cross-sectional area is provided for the working fluid in a crossover passage through which the fluid flows into the combustion cylinder 20. The intake valve 18 may be configured to move between a closed state and a plurality of open states. The plurality of open states may include a series of separate states, each defining a different cross-sectional area, or may include a series of states through which the cross-sectional area changes continuously. The controller 60 is configured to control the movement of the intake valve 18 such that a cross-sectional area selected for the working fluid to flow through it into the combustion cylinder 20 is defined.

[0065] The controller 60 is configured to control the movement of the intake valve so that a selected cross-sectional area is determined. The controller is configured to select a selected cross-sectional area so that the working fluid in the crossover passage 30 flows through the cross-sectional area into the combustion cylinder 20 at a speed exceeding a speed threshold. The controller 60 may determine the selected cross-sectional area based on instructions for the engine parameters received. For example, the controller 60 may be configured to determine an estimate of the speed of the fluid flowing into the combustion cylinder 20 using a mathematical model (e.g., based on Bernoulli flow). The controller 60 may determine, for example, based on a mathematical model or a lookup table, that the cross-sectional area must be limited to the selected cross-sectional area in order for the working fluid to flow into the combustion cylinder 20 at a speed below a speed threshold. Therefore, the controller 60 may control the intake valve 18 to move to an open state, which involves opening the valve, but does not necessarily have to be opened to a fully open state. Rather, the valve may be opened to some extent of the fully open state, for example, the intake valve may move to a half-open state. The extent to which the intake valve 18 is moved may be based on the pressure indication in the crossover passage 30 received. For example, if the pressure in the crossover passage 30 is very high, the controller 60 may control the intake valve 18 to open to the fully open position, so that even with a larger cross-sectional area, the working fluid can still flow into the combustion cylinder 20 at a speed faster than the velocity threshold. In another example, the controller 60 may determine that the pressure in the crossover passage 30 is not very high, and therefore control the intake valve 18 to open to a slightly open position, such that the defined cross-sectional area is very small and the flow of working fluid into the combustion cylinder 20 is much faster.

[0066] The controller 60 is configured to control the valve lift so that the working fluid flows into the combustion cylinder at a velocity exceeding a velocity threshold. The velocity at which the working fluid flows into the combustion cylinder may typically be determined as the peak flow velocity that occurs when the intake valve 18 opens or immediately thereafter. This velocity may also be determined based on measurements from an exhaust sensor. For example, if the exhaust sensor determines that NOx and / or particulate matter generation exceeds a threshold level, the flow velocity is too low. By controlling the movement of the intake valve 18 so that the flow velocity of the working fluid flowing into the combustion cylinder 20 exceeds the velocity threshold, the mixture of air and fuel in the combustion cylinder may have a lean ratio that exceeds a lean threshold. The lean threshold is such that when the fuel and working fluid are well mixed, sufficient oxygen is supplied to each unit of fuel to cause complete combustion and suppress particulate matter generation. Controlling the flow velocity to exceed the velocity threshold may reduce the stress on the fuel injector 82 because it reduces the requirements on the fuel injector 82 for mixing the fuel and working fluid. This may extend the life of the injector. Furthermore, by continuing to open the intake valve 18 with a low lift, the distance traveled is reduced, which can shorten the time required for the intake valve 18 to move from the closed state to the open state. This speeds up the process of supplying the working fluid from the crossover passage 30 to the combustion cylinder 20. As a result, the intake valve 18 may be opened at a later timing in the piston cycle.

[0067] The controller 60 may determine the movement of the intake valve 18 based on data relating to the design of the intake valve 18. For example, dimensions such as the shape of the valve or the surface friction level may be considered. It will be understood that details of the fluid flow path from the crossover passage 30 to the combustion cylinder 20 (e.g., shape, length, diameter, etc.) may affect the flow velocity. When determining the cross-sectional area defined by the intake valve 18 for the fluid flow, the controller 60 may access a lookup table specific to the intake valve 18.

[0068] In another embodiment, the split-cycle internal combustion engine 100 may operate based on variable valve opening and closing timing. This may include the controller 60 selecting a first position and a second position based on a determined value of the pressure and / or concentration of the working fluid, such that after the intake valve 18 moves to the open position in a selected first position, the working fluid flows into the combustion cylinder 20 at a speed faster than a speed threshold.

[0069] The operation method of a split-cycle internal combustion engine, for example, the split-cycle internal combustion engine 100 shown in Figures 1 and 2, will be described below with reference to Figure 6. The method begins in step 600 and proceeds to step 610, where a peak temperature instruction is received. As previously mentioned, this instruction may be received from one or more sensors and may provide information about engine parameters. In step 620, the peak temperature of combustion in the combustion cylinder 20 is determined based on the instruction received in step 610. The peak temperature may be determined as previously mentioned. In step 630, the determined peak temperature is compared to a selected threshold. If the determination is that the peak temperature is below the selected threshold, the method proceeds to step 640, where the peak temperature is compared to a cooling threshold. In step 640, if the determined peak temperature is above the cooling threshold, it is determined that the engine's peak temperature is within a suitable range. The method then returns to the first step, where another peak temperature instruction is received. This return may be performed on a variable time scale; for example, instructions may be received during a selected period, and instructions may be received more frequently during startup when the fluctuations in engine parameter values ​​are greater. In response to the determination in step 630 that the peak temperature determined is above a selected threshold, or in response to the determination in step 640 that the peak temperature determined is below a cooling threshold, the method proceeds to step 650. In step 650, the cooling system is controlled to adjust the temperature of the working fluid based on the determined peak temperature. This temperature may be adjusted to move the peak temperature of combustion within a suitable range. The method then returns to step 610. The frequency of received instructions may be higher for the return from step 650 than for step 640.

[0070] The operation method of a split-cycle internal combustion engine, for example, the split-cycle internal combustion engine 100 shown in Figures 1 and 2, will be described below with reference to Figure 7. Steps 700-740 of this method correspond to steps 600-640 in Figure 6, respectively, and therefore their description will be omitted. In step 750, first and second positions for opening and closing the intake valve are selected to adjust the temperature of the working fluid in response to the determined peak temperature exceeding a selected threshold, or to the determined peak temperature falling below a cooling threshold. The temperature of the working fluid may be adjusted to move the peak temperature of combustion within a suitable range (e.g., between a cooling threshold and a selected threshold).

[0071] The operation method of a split-cycle internal combustion engine, for example, the split-cycle internal combustion engine 100 shown in Figures 1 and 2, is described below with reference to Figure 8. The method begins in step 800 and proceeds to step 810, where instructions for engine parameters are received. In step 820, the fuel ignition parameters are determined based on the instructions received in step 810. The ignition parameters may be determined as described above. In step 830, the ignition parameters are compared to an ignition threshold. If the ignition parameters are determined to be above the ignition threshold, the method proceeds to step 840, where the ignition parameters are compared to an over-reactivity threshold. If the ignition parameters are below the over-reactivity threshold, the ignition parameters are considered to be within a suitable range, and the method returns to step 810, which is performed as described above. Depending on whether the ignition parameters are below the ignition threshold or above the over-reactivity threshold, the method proceeds to step 850, where, for example, a reactivity regulator is activated to adjust the working fluid so that the reactivity falls within a suitable range for engine operation.

[0072] The operation method of a split-cycle internal combustion engine, for example, the split-cycle internal combustion engine 100 shown in Figures 1 and 2, will be described below with reference to Figure 9. Steps 900-940 of this method correspond to steps 600-640 in Figure 6, respectively, and therefore their explanation will be omitted. In step 950, the injection position of the injector is selected depending on whether the determined peak temperature exceeds a selected threshold or whether the determined peak temperature falls below a cooling threshold. The injection position is selected to adjust the temperature of the working fluid, as described above.

[0073] The operation method of a split-cycle internal combustion engine, for example, the split-cycle internal combustion engine 100 shown in Figures 1 and 2, will be described below with reference to Figure 10. This method begins in step 1000 and proceeds to step 1010, in which a peak temperature instruction is received. Based on the instruction received in step 1010, an estimate of the peak combustion temperature may be determined as described above. In step 1030, the cooling system is controlled so that the peak combustion temperature falls within a selected range. This step may include increasing and / or decreasing the cooling of the working fluid based on whether the peak combustion temperature is lower or higher than the selected range.

[0074] The operation method of a split-cycle internal combustion engine, for example, the split-cycle internal combustion engine 100 shown in Figures 1 and 2, is described below with reference to Figure 11. The method begins in step 1100 and proceeds to step 1110, where an engine parameter instruction is received. In step 1120, based on this engine parameter instruction, the values ​​of the engine parameters (pressure and / or temperature in the example in Figure 11) may be determined. This determination depends on the content of the instruction. This may involve the use of thermodynamic relationships to process the value of one engine parameter to determine the value of another parameter (pressure or temperature). In step 1130, the determined parameters (pressure and / or temperature) are compared to an input threshold. Depending on whether the parameters are above the input threshold, the working fluid is considered suitable for use in the combustion cylinder, and the method returns to step 1110. Depending on whether the parameters are within the input threshold, the method proceeds to step 1140, where the working fluid parameters (pressure / temperature) are controlled so that the working fluid is within a range suitable for flowing into the combustion cylinder 20 at a speed faster than a speed threshold. Next, the method returns to step 1110.

[0075] The operation method of a split-cycle internal combustion engine, for example, the split-cycle internal combustion engine 100 shown in Figures 1 and 2, will be described below with reference to Figure 12. Steps 1200-1230 of this method correspond to steps 1100-1130 in Figure 11, respectively, and therefore their explanation will be omitted. In step 1240, the movement of the intake valve is controlled to define the cross-sectional area of ​​the intake valve opening through which the working fluid flows from the crossover passage 30 to the combustion cylinder 20. The cross-sectional area is selected so that the working fluid flows into the combustion cylinder 20 at a speed exceeding a velocity threshold, as described above.

[0076] While we have discussed NOx, it should be understood that the term NOx can be considered to encompass any suitable nitrogen oxide compound, such as N2O or any other combination of nitrogen and oxygen. It is not meant to be interpreted as being limited only to compounds containing a single nitrogen atom.

[0077] It will be understood that the piston cycle is a periodic cycle, and therefore, occurring later in the piston cycle can indicate occurring later in time. Each piston cycle can be considered to begin with the combustion piston 22 at its bottom dead center ("BDC") position. During the piston cycle, the combustion piston 22 then moves from the BDC position to the top dead center (TDC) position, and then returns to the BDC position. Therefore, descriptions such as an injector injecting fuel at an earlier / later position in the piston cycle, or opening / closing an intake valve at an earlier / later position in the piston cycle, are based on the piston cycle moving from BDC to BDC.

[0078] Referring to the drawings as a whole, it will be apparent that schematic functional block diagrams are used to illustrate the functionality of the systems and apparatus described herein. However, it will be apparent that this functionality does not need to be divided as shown and should not be interpreted as implying any specific hardware configuration other than those described or claimed below. The functionality of one or more components shown in the drawings may be further divided and / or distributed throughout the apparatus of this disclosure. In some embodiments, the functionality of one or more components shown in the drawings may be integrated into a single functional body.

[0079] In some examples, one or more memory elements may store data and / or program instructions used to perform the operations described herein. Embodiments of this disclosure provide a tangible non-temporary storage medium that includes program instructions operable to program a processor to perform one or more of the methods described herein and / or in the claims, and / or to provide a data processing device described herein and / or in the claims.

[0080] The operations and devices outlined herein may be implemented using fixed logic, such as assemblies of logic gates, or programmable logic, such as software and / or computer program instructions executed by a processor. Other examples of programmable logic include programmable processors, programmable digital logic (e.g., field-programmable gate arrays (FPGAs), erasable programmable read-only memory (EPROMs), electrically erasable programmable read-only memory (EEPROMs)), application-specific integrated circuits (ASICs), or any other type of digital logic, software, code, electronic instructions, flash memory, optical discs, CD-ROMs, DVD-ROMs, magnetic cards or optical cards, other types of machine-readable media suitable for storing electronic instructions, or any combination thereof.

[0081] From the foregoing description, it will be apparent that the embodiments shown in the drawings are merely illustrative and include features that may be generalized, omitted, or substituted as described herein and in the claims. In the context of this disclosure, other examples and variations of the apparatus and methods described herein will be obvious to those skilled in the art.

Claims

1. A compression cylinder housing a compression piston, A combustion cylinder housing a combustion piston, A crossover passage is provided between the compression cylinder and the combustion cylinder to supply working fluid to the combustion cylinder, An intake valve that controls the flow of the working fluid flowing from the crossover passage to the combustion cylinder, the intake valve being operable to move between an open state and a closed state, A controller is positioned to receive the pressure value of the working fluid in the crossover passage, A cooling system is arranged to regulate the temperature of the working fluid supplied to the combustion cylinder, Equipped with, The cooling system is, A coolant injector that injects coolant into at least one of the compression cylinder and the crossover passage so as to increase the pressure of the working fluid in the crossover passage, Equipped with, The crossover passage includes a recuperator that utilizes heat from the exhaust fluid discharged from the combustion cylinder. The recuperator utilizes the heat to heat the working fluid supplied from the compression cylinder to the combustion cylinder, Based on the received pressure value, the controller is configured to control the pressure of the working fluid in the crossover passage using the coolant injected by the coolant injector, in response to a determination that the pressure of the working fluid in the crossover passage is below an input threshold, so that the working fluid flows into the combustion cylinder at a speed exceeding a speed threshold. A split-cycle internal combustion engine characterized by the following:

2. The control of the aforementioned pressure is The pressure of the working fluid increases so that the working fluid flows into the combustion cylinder at a speed exceeding the speed threshold, including, The split-cycle internal combustion engine according to claim 1.

3. The control of the aforementioned pressure is The operation of the cooling system such as cooling the working fluid supplied to the combustion cylinder, including, The split-cycle internal combustion engine according to claim 1.

4. The operation of the aforementioned cooling system is as follows: Cooling of the working fluid in at least one of the compression cylinder and the crossover passage, including, A split-cycle internal combustion engine according to claim 1 or 3.

5. The controller is arranged to receive both the pressure and the temperature values. A split-cycle internal combustion engine according to any one of claims 1 to 3.

6. The controller is configured to control the pressure of the working fluid such that the peak velocity of the working fluid flowing into the combustion cylinder exceeds the velocity threshold. A split-cycle internal combustion engine according to any one of claims 1 to 3.

7. A method for operating a split-cycle internal combustion engine, wherein the split-cycle internal combustion engine is A compression cylinder housing a compression piston, A combustion cylinder housing a combustion piston, A crossover passage is provided between the compression cylinder and the combustion cylinder to supply working fluid to the combustion cylinder, An intake valve that controls the flow of the working fluid flowing from the crossover passage to the combustion cylinder, the intake valve being operable to move between an open state and a closed state, A cooling system is arranged to regulate the temperature of the working fluid supplied to the combustion cylinder, Equipped with, The cooling system is, A coolant injector that injects coolant into at least one of the compression cylinder and the crossover passage so as to increase the pressure of the working fluid in the crossover passage, Equipped with, The crossover passage includes a recuperator that utilizes heat from the exhaust fluid discharged from the combustion cylinder. The recuperator utilizes the heat to heat the working fluid supplied from the compression cylinder to the combustion cylinder, The aforementioned method, A step of receiving the value of the pressure of the working fluid in the crossover passage, A step of determining the pressure of the working fluid in the crossover passage based on the received pressure value, A step of controlling the pressure of the working fluid in the crossover passage using the coolant injected by the coolant injector so that the working fluid flows into the combustion cylinder at a speed exceeding a speed threshold, in response to a determination that the pressure of the working fluid in the crossover passage falls below an input threshold, Having, A method for operating a split-cycle internal combustion engine, characterized by the following:

8. Includes a program instruction configured to program a processor to carry out the method described in claim 7, A computer program product characterized by the following features.

Images