Method for characterizing a five-stroke engine for a vehicle.

Abstract

The present invention relates to a method for characterizing a five-stroke engine (2) for a vehicle, comprising the implementation by data processing means (11) of a server (10) of steps of: Obtaining a value of at least one configuration parameter of the five-stroke engine (2); Calculating, for at least one value of at least one operating parameter of said five-stroke engine (2), a value of at least one parameter representative of the performance of a simulated four-stroke engine (2'), using a simulation model of said four-stroke engine (2') configured with said obtained value of at least one configuration parameter of the five-stroke engine (2), wherein, for each connecting rod (21) of the five-stroke engine (2), the simulated four-stroke engine (2') comprises a corresponding virtual connecting rod (21') having a variable length so as to reproduce the operation of the five-stroke engine (2);Processing said received configuration parameter value as a function of at least one calculated parameter value representative of the performance of the simulated four-stroke engine (2'), and rendering the result on an interface (13) of the server (10). [Fig. 1a];

Description

Title of the invention: Method for characterizing a five-stroke engine for a vehicle. [0001 ] GENERAL TECHNICAL FIELD

[0002] The present invention relates to the field of internal combustion engines. More specifically, it relates to a method for characterizing a five-stroke engine for a vehicle.

[0003] STATE OF THE ART

[0004] To achieve the energy transition, particularly in the field of mobility, hydrogen engines are being developed.

[0005] These engines are internal combustion (or "explosion") engines using dihydrogen as fuel instead of a hydrocarbon. Indeed, the combustion of dihydrogen normally produces only water and not CO2. These engines should not be confused with electric motors which would be powered by a fuel cell (hydrogen).

[0006] However, the conventional piston engine is not very suitable for the combustion of gaseous hydrogen. In fact, the temperature rises sharply and the formation of nitrogen oxides (NOx, from nitrogen in the air mixed with dihydrogen) and notorious pollutants is observed, or even problematic self-ignition ("knocking") which degrades performance.

[0007] To solve these problems, a new type of internal combustion engine was developed: the five-stroke engine.

[0008] While a conventional engine is four-stroke (intake, compression, expansion, exhaust), a five-stroke engine also has a fifth "cooling" stroke for the combustion chamber which makes it possible to avoid the aforementioned problems, and proves to be very efficient.

[0009] To further improve its efficiency, it is desirable, like all modern internal combustion engines, to further optimize their design so as to improve their performance, and in particular the values ​​of configuration parameters such as the compression ratio, displacement volumes / dead volume, etc.

[0010] Design assistance systems are known for this purpose which simulate the operation of the engine as a function of its configuration parameters and operating conditions, and which optimize the value of said configuration parameters so as to maximize engine performance for said operating conditions.

[0011] The problem is that existing simulators are designed for four-stroke engines, and prove unsuitable for the five-stroke engine, because the operating paradigm is too different.

[0012] There is therefore currently no solution for effectively optimizing the configuration parameters of a five-stroke engine.

[0013] One could of course design a new design aid system for a five-stroke engine from a blank page, but this would be long and complex, and its effectiveness would not be guaranteed.

[0014] The present invention improves this situation. PRESENTATION OF THE INVENTION

[0015] The present invention therefore relates, according to a first aspect, to a method for characterizing a five-stroke engine for a vehicle, comprising the implementation by data processing means of a server of steps of: a. Obtaining a value of at least one five-stroke engine configuration parameter; b. Calculation, for at least one value of at least one operating parameter of said five-stroke engine, of a value of at least one parameter representative of the performance of a simulated four-stroke engine, using a simulation model of said four-stroke engine configured with said value obtained from at least one configuration parameter of the five-stroke engine, wherein, for each connecting rod of the five-stroke engine, the simulated four-stroke engine comprises a corresponding virtual connecting rod having a variable length so as to reproduce the operation of the five-stroke engine; c. Processing said received configuration parameter value as a function of at least one calculated parameter value representative of the performance of the simulated four-stroke engine, and rendering the result on a server interface.

[0016] According to advantageous and non-limiting characteristics:

[0017] The five-stroke engine comprises a rotating real crankshaft and, for each real connecting rod, a real cylinder and a real piston translating in the real cylinder, the real connecting rod being of fixed length and connecting the real crankshaft to the real piston.

[0018] The simulated four-stroke engine comprises a rotating virtual crankshaft and, for each virtual connecting rod, a virtual cylinder and a virtual piston translating in the virtual cylinder, the virtual connecting rod of variable length connecting the virtual crankshaft to the virtual piston.

[0019] The real crankshaft is of the epicyclic type, while the virtual crankshaft is of the conventional type.

[0020] For each real connecting rod, the variable length of said corresponding virtual connecting rod is such that for any angle of the virtual crankshaft, the displacement of the virtual piston in the virtual cylinder is equal to the displacement of the real piston in the real cylinder, at the same angle of the real crankshaft.

[0021] For each real connecting rod, the variable length 1' of said corresponding virtual connecting rod is expressed as a function of the angle 0 of the virtual crankshaft by the formula r(0)=l+f4(0)-f5(0), where 1 is the fixed length of the real connecting rod, f5(0) is the displacement of the real piston in the real cylinder, and f4(0) is the displacement that the virtual piston would have in the virtual cylinder if the real connecting rod length were fixed and equal to the length of the real connecting rod.

[0022] Said displacement that the virtual piston would have in the virtual cylinder if the real connecting rod length were fixed and equal to the real connecting rod length, is a sinusoidal displacement of a four-stroke engine piston.

[0023] Step (b) comprises, for any angle of the virtual crankshaft, the following sub-steps:

[0024] (bl) calculating the length of each virtual connecting rod as a function of the angle of the virtual crankshaft;

[0025] (b2) implementing said four-stroke engine simulation model using said calculated length of the virtual connecting rods.

[0026] Step (b2) comprises updating the length of the virtual connecting rods as a parameter of said four-stroke engine simulation model.

[0027] Said five-stroke engine includes intake, compression, expansion, exhaust and cooling strokes.

[0028] Said five-stroke engine is a hydrogen engine.

[0029] Step (a) comprises obtaining a plurality of values ​​of the at least one configuration parameter of the five-stroke engine; step (b) being implemented for each of said obtained values ​​of the at least one configuration parameter of the five-stroke engine; and step (c) comprising selecting an optimized value of the at least one configuration parameter of the five-stroke engine from among said obtained values ​​of the at least one configuration parameter of the five-stroke engine, as a function of the calculated values ​​of the parameters representative of the performance of the simulated four-stroke engine.

[0030] Said simulation model calculates the value of the at least one parameter representative of the performance of said simulated four-stroke engine as a function of said value of the at least one operating parameter, in particular at least one first operating parameter and at least one second operating parameter.

[0031] Step (b) is implemented for at least one value of at least one first operating parameter of said five-stroke engine, and comprises determining the value of at least one second operating parameter of the five-stroke engine as a function of said value of the at least one first operating parameter of the engine.

[0032] Step (b) comprises determining optimized values ​​of the at least one second operating parameter of the five-stroke engine, using the simulation model.

[0033] The at least one first operating parameter is a parameter representative of the operating environment or a parameter imposed by the vehicle (1) such as a target power; and / or the at least one second operating parameter is chosen from ignition timing, fuel injection flow rate, and supercharging parameters.

[0034] Step (b) is implemented for a plurality of values ​​of the at least one first operating parameter.

[0035] According to a second aspect, the invention relates to a server, characterized in that it comprises data processing means configured to: - Obtain a value of at least one configuration parameter of a five-stroke engine; - Calculating, for at least one value of at least one operating parameter of said five-stroke engine, a value of at least one parameter representative of the performance of a simulated four-stroke engine, using a simulation model of said four-stroke engine configured with said value obtained from at least one configuration parameter of the five-stroke engine, wherein, for each connecting rod of the five-stroke engine, the simulated four-stroke engine comprises a corresponding virtual connecting rod having a variable length so as to reproduce the operation of the five-stroke engine; - Process said received configuration parameter value as a function of at least one calculated parameter value representative of the performance of the simulated four-stroke engine, and return the result to a server interface.

[0036] According to a third aspect, the invention relates to a test bench comprising said engine and the server according to the second aspect.

[0037] According to a fourth and a fifth aspect, the invention provides a computer program comprising code instructions for executing a method according to the first aspect of characterizing a five-stroke engine for a vehicle; and a storage means readable by computer equipment on which is recorded a computer program product comprising code instructions for executing a method the first aspect of characterizing a five-stroke engine for a vehicle. PRESENTATION OF FIGURES

[0038] Other characteristics and advantages of the present invention will appear on reading the following description of a preferred embodiment. This description will be given with reference to the appended drawings in which:

[0039] [Fig. la]la [Fig.la] is a diagram of a system for implementing the method according to the invention.

[0040] [Fig.lb] [Fig.lb] is a diagram of a real engine and a virtual engine.

[0041] [Fig.2] [Fig.2] represents the cylinder volume over two crankshaft revolutions for a five-stroke engine and a four-stroke engine, respectively in solid line and dotted line.

[0042] [Fig.3a] [Fig.3a] is a flowchart illustrating the steps of a first embodiment of the method according to the invention.

[0043] [Fig.3b] [Fig.3b] is a flowchart illustrating the steps of a second embodiment of the method according to the invention.

[0044] [Fig.4] [Fig.4] represents the valve openings over two crankshaft revolutions for a five-stroke engine DETAILED DESCRIPTION

[0045] Architecture

[0046] The present invention relates to a method for characterizing a five-stroke engine 2 for a vehicle, in a system as shown in Figure 1.

[0047] It is understood that said engine 2 is intended for a vehicle, and it could already be integrated into a vehicle, but generally, and as can be seen in Figure 1, it is for the moment integrated into a test bench 1. Note that the engine 2 may comprise a computer in particular configured to implement a method for controlling said engine 2, i.e. adapting the values ​​of certain of its operating parameters while it is running (i.e. in operation). By control, we mean the determination and application of adequate values ​​of said operating parameters to the engine 2 (see below), so as to change its behavior for example to react to different operating conditions. To rephrase, the possible computer has the role of managing the values ​​of the operating parameters of the engine 2.

[0048] The vehicle is typically a land vehicle, wheeled or tracked, such as a car, a truck, etc. It will be understood that it could alternatively be a ship, an airplane, etc. The engine 2 is for the propulsion of the vehicle.

[0049] Said five-stroke engine 2 is an internal combustion engine, generally hydrogen, either pure or dual-fuel hydrogen / diesel, hydrogen / bioethanol, hydrogen / B100. B100 is a fuel composed of up to 100% fatty acid methyl esters, well known to those skilled in the art. Note that the engine 2 could be gasoline, although the five-stroke operation is particularly suitable for hydrogen which causes a high temperature rise.

[0050] Said engine 2 comprises, like any internal combustion engine, at least one assembly of a piston 20, a connecting rod 21 and a cylinder 22. Said assemblies share a crankshaft 23. In each assembly, the connecting rod 21 connects the crankshaft 23 to the piston 20 so as to transform a continuous rotational movement of the crankshaft 23 into an alternating translational movement of the piston 20 in the cylinder 22. The end of the cylinder defines a combustion chamber for the fuel (typically hydrogen). Note that said piston 20, connecting rod 21, cylinder 22 and crankshaft 23 of the engine 2 will be called "real" as opposed to virtual equivalents which will be described later.

[0051] As explained previously, a five-stroke engine includes, in addition to the four classic strokes (intake, compression, expansion, exhaust), a fifth "cooling" stroke for the combustion chamber which makes it possible to avoid the aforementioned problems, and proves to be very efficient.

[0052] With reference to [Fig.2], which represents the volume of the cylinder 22 and therefore the displacement of the piston 20 (the two quantities are proportional) as a function of the angle of the crankshaft 23 (over 720°, i.e. 2 revolutions) of the five-stroke engine 2, each stroke lasts approximately 144° crankshaft, and we notice over the interval [630°, 90°] substantially a plateau, which corresponds to this fifth stroke: the piston 20 hardly moves any more, which allows the air to circulate in the cylinder 22 and gives the chamber time to cool. In addition, as during cooling the intake and exhaust valves are open at the same time, we end up with valves open for approximately 288° crankshaft. (These values ​​are variable depending on the opening advances and closing delays that we define according to our combustion).By contrast, in a four-stroke engine the piston displacement is sinusoidal (with each stroke over 180° crankshaft), see the dotted curve in [Fig.2].

[0053] To achieve such a movement, a five-stroke engine comprises, for example, an epicyclic mechanism (called planetary-satellite): the crankshaft 23 acts as a planet carrier and the connecting rod foot 21 is articulated on an eccentric linked to the satellite. It then describes a conchoidal trajectory of a circle which allows the observed slowing down.

[0054] The engine 2 further advantageously comprises conventional equipment of an internal combustion engine such as pipes, valves, injectors, manifolds, a turbocharger, etc.

[0055] As will be seen, preferably the possible test bench 1 (and potentially directly the engine 2) is equipped with at least one sensor 3 of a first operating parameter of the engine 2 (see below). Alternatively, it is possible to have a software sensor 3, i.e. virtual.

[0056] Furthermore, there is a server 10 for implementing the present method. Conventionally, this server 10 is a computer device connected to the engine 2 and to the possible sensor 3, comprising data processing means 11 such as a processor, and generally data storage means 12 such as a memory. The server 10 further comprises an interface 13, for data entry / restitution (for example a touch screen).

[0057] The server 10 is preferably connected to the engine 2, in particular via its computer, even if it could alternatively be directly connected to the sensor 3.

[0058] Principle

[0059] The present method aims to characterize the engine 2 so as to maximize its performance. By characterization, we mean the definition or at least the validation of a design of the engine 2 (and more precisely of configuration parameter values ​​of this engine 2) so as to optimize its performance. In other words, this method is intended to anticipate the real and not theoretical performance of an engine 2 in design, and more precisely to test or even improve the design of this engine in an operating context on the basis of data to which we will return. It is noted that this method is based on real data and is opposed to pure modeling which would make it possible to define a design of engine 2 solely by mathematical considerations.

[0060] It is assumed that engine 2 has three types of parameters, each being in all cases a technical physical quantity associated with engine 2: - at least one engine configuration parameter 2, which is the parameter that we will currently seek to validate or even improve (output parameter), and which generally applies to both a five-stroke engine and a four-stroke engine. These include the type of fuel, the number of cylinders 22, a type of architecture (in-line or V), the diameter of each cylinder 22 (bore), the maximum distance traveled by each piston 20 (stroke), the compression ratio, the displacement volumes / dead volume, maps and type of turbocharger, the maximum flow characteristics of the injectors, the volume of the manifolds, the diameters of the pipes, etc. These are the parameters that physically define the engine 2 and all its components, we also speak of structural parameters. - at least one operating parameter. As opposed to structural parameters, operating parameters are variable parameters, representative of the environment in which the engine 2 operates (operating conditions) and the controls applied to it. A distinction is made between: • the first parameter(s), which are undergone parameters, in particular either external parameters typically representative of the operating environment (for example the external temperature of the engine), or parameters imposed by the vehicle 1, in particular a target power. • the second parameter(s), which are on the contrary controllable operating parameters, which can be adjusted. Preferably, the second parameter(s) are chosen from ignition timing, fuel injection flow rate, and supercharging parameters. - finally, at least one parameter representative of the performances, which is a parameter relating to a predefined criterion making it possible to evaluate the engine 2. Preferably this criterion is the energy efficiency and / or the emissions, so that this parameter can be the fuel consumption, the quantities produced of C02 / N0x, etc.

[0061] In a known manner, a simulation of the engine 2 will be implemented so as to test values ​​of the configuration parameter(s) making it possible to optimize (i.e. maximize / minimize as appropriate, or at least respect expected thresholds) the parameter(s) representative of the performances, for given values ​​of at least one operating parameter. Preferably, there are a plurality of operating parameters including at least a first parameter and at least a second operating parameter of which at least one can be fixed (in particular the first), i.e., it is sought to find the best values ​​of the configuration parameters regardless of the values ​​of the other operating parameters, so as to obtain a versatile configuration.

[0062] It will be understood that the present method is not limited to any combination of configuration parameters / operating parameters / performance representative parameters, as long as these are physical quantities linked to the engine 2 with a technical interest. Limiting oneself to certain parameters would unduly limit the scope of the present application, especially since a great many strategies for optimizing configuration parameters have been known for a long time.

[0063] Indeed, the object of the present method is not a new strategy for testing / optimizing parameters by simulation, but a trick allowing the agnostic use of a four-stroke engine simulator to simulate a five-stroke engine. Thus, a high-performance simulator can be reused simply and effectively. This makes it possible to minimize the work required to obtain a design tool for a five-stroke engine, while having guarantees on its performance.

[0064] Method

[0065] In this respect, with reference to [Fig.3a], the method begins with a step (a) of obtaining (by the data processing means 11 of the server 10) a value of at least one configuration parameter of the engine 2, which will be called a candidate value.

[0066] Note that step (a) may concern several configuration parameters, and / or several values ​​of the configuration parameter(s), so as to be able to compare these values. We will see later an embodiment aimed at determining an optimal value of the configuration parameter(s).

[0067] According to a particular embodiment, said received configuration parameter value is that of the engine 2 of a test bench 1 connected to said server 10 (it is in particular the possible computer of the engine 2 which is connected to the server 10), said engine 2 then being to be tested. It is understood that each engine 2 has a set of fixed values ​​of configuration parameters.

[0068] In all cases this step must be understood broadly as encompassing either directly the reception of said values, in particular from said computer of the engine 2, or their entry via an interface 13 of the server 10.

[0069] Again, this is well known to those skilled in the art and will not be re-discussed.

[0070] According to one embodiment, step (a) may further comprise obtaining a value of at least one operating parameter of the engine 2, again either from the interface 13 of the server, or from the engine 2, in particular a sensor 3 of the engine 2.

[0071] Then, in a main step (b), the means 11 calculate for at least one value of at least one operating parameter of said five-stroke engine 2, values ​​of at least one parameter representative of the performance of a simulated four-stroke engine 2', using a simulation model of said four-stroke engine 2' configured with said value obtained from at least one configuration parameter of the five-stroke engine 2.

[0072] It is understood that said simulator calculates the values ​​of the parameter(s) representative of the performance of said simulated engine 2' as a function of said values ​​of the operating parameters.

[0073] Preferably, there are a large number of values ​​of said operating parameters, in particular so as to test varied operating conditions. They can for example be obtained in step (a) as explained, but alternatively they can be chosen in step (b) (directly by the server 10) randomly or according to a given distribution. For example, transients can be studied, i.e. variations over time of the values ​​of the operating parameters corresponding to start-up, acceleration or deceleration phases, or even the effects of rapid changes in load or engine speed.

[0074] According to another mode of operation, the values ​​of all or part of the operating parameters (and in particular the first operating parameters) can be fixed or received from possible sensors 3 of the engine 2 to which the server 10 is preferably connected.

[0075] In any case, it is important to understand that the real engine 2 is a five-stroke, while the simulated engine 2', called a virtual engine, is a four-stroke. We can therefore use any existing four-stroke engine simulator, for example AMEsim, configured with the engine configuration parameters mentioned above (whether the engine is a four-stroke or five-stroke, the values ​​of these parameters do not change except possibly those linked to the valve opening phases, see below), and any known optimization algorithm.

[0076] To reformulate, despite the time difference, the simulation model can be configured with said value obtained from at least one configuration parameter of the five-stroke engine 2, i.e. directly using the value(s) of the configuration parameter(s) of the five-stroke engine 2 as values ​​of the corresponding parameters of the simulated four-stroke engine 2' (in other words, these values ​​obtained are considered as those of the parameters of the simulated engine).

[0077] Thus, the simulated four-stroke engine 2' comprises for each real component 20, 21, 22, 23 of the real engine 2, a virtual equivalent 20', 21', 22', 23'.

[0078] More precisely, the simulated engine 2' comprises a rotating virtual crankshaft 23' and, for each piston 20, connecting rod 21 and cylinder 22, respectively a virtual piston 20', a virtual connecting rod 21' and a virtual cylinder 22'. The virtual piston 20' is therefore in translation in the virtual cylinder 20', the virtual connecting rod 21' connecting the virtual crankshaft 23' to the virtual piston 20'. For each real member 20, 21, 22, 23, the "corresponding" virtual member 20', 21', 22', 23' in the simulated engine 2' will be designated. It is recalled that the real crankshaft 23 is typically of the epicyclic type (which allows an “irregular” movement of the piston 20 and thus the fifth stroke), whereas the virtual crankshaft 23' is a “classic” crankshaft of a four-stroke engine (which causes a sinusoidal movement of the virtual piston 20').

[0079] The trick is that, for each connecting rod 21 of the five-stroke engine 2, the corresponding virtual connecting rod 21' has a variable length so as to reproduce the operation of the five-stroke engine 2. To rephrase, during the simulation the length of the virtual connecting rods 21' will vary in real time, which will modify the displacement of the virtual pistons 20' (we will no longer have the classic sinusoidal displacement) and make it possible to simulate a five-stroke engine. We understand that this is to trick the simulator: of course, there is no connecting rod of variable length in reality, neither in a four-stroke engine nor in a five-stroke engine, and no simulator is designed to dynamically manage this length (the length of the connecting rod is supposed to be entered as a configuration parameter among others - i.e. present a fixed value, and not be a signal).

[0080] This is thus a matter of artificially altering the operation of the simulator, because if the variable length is correctly chosen we will see that the simulator will simulate a five-stroke engine instead of a four-stroke engine in spite of itself, and this in a completely agnostic manner. We repeat that the simulation itself is done in an unchanged manner, the simulator not being bothered by this variable length although it is absolutely not provided for, and allowing it to operate in a normal manner.

[0081] More precisely, if we return to [Fig.2], it is a question, starting from the sinusoidal curve of a 4-stroke engine, of modifying the length of the virtual connecting rod 21' as a function of the crankshaft angle 23 / 23' so as to find the more complex curve of the five-stroke engine.

[0082] To reformulate, for each real connecting rod 21, the variable length of said corresponding virtual connecting rod 21' is such that, for any angle of the virtual crankshaft 23', the displacement of the virtual piston 20' in the virtual cylinder 22' is equal to the displacement of the real piston 20 in the real cylinder 22, at the same angle of the real crankshaft 23'.

[0083] Mathematically, we assume that we have: - a first function d5=f5(0), where d5 is the displacement of the real / virtual piston 20 / 20' and 0 the angle of the real / virtual crankshaft 23 / 23' modulo 720° (which is not necessarily a defined function, we can just have a list of the values ​​of d for each value of 0); - a second function d4=f4(0), where d4 is the displacement of the piston of a four-stroke engine (i.e. the displacement that the virtual piston 20' would have if the virtual connecting rod 21' were of constant length), which is preferably a sinusoidal function, typically of the form f4(0)=a*sin(0 / 2)+b, with a and b predefined constants; - by noting 1 the (fixed) length of the real connecting rod 21 and 1' the (variable) length of the virtual connecting rod 21', we can express the latter as a function of 0 as l'(0)=lA(0), where A is the observed displacement difference d-d', ie 1'(0)=l+f4(0)-f5(0). Indeed, because we use a virtual connecting rod 21' of variable length, the displacement noted d4' observed becomes d4'= d4+(l-l'). And because we require that the displacement of the virtual piston 20' in the virtual cylinder 22' be equal to the displacement of the real piston 20 in the real cylinder 22, at the same angle of the real crankshaft 23', ie d5= d4', ie f5(0)= f4(0)+(l-l'), hence r(0)=l+f4(0)-f5(0).

[0084] It is therefore sufficient, during step (b), to “reparameterize” at each time step the length of the virtual connecting rod 21' in the simulator.

[0085] In this respect, step (b) advantageously comprises, for any angle 0 of the virtual crankshaft 23' (and in practice for any time step, the angle 0 being recalculated at each time step as a function of time, knowing the rotation speed of the crankshaft) two sub-steps. First of all, there is a step (bl) of calculating the length of each virtual connecting rod 21' as a function of the angle of the virtual crankshaft 23'. This typically involves applying the above formula.

[0086] Then, in a step (b2) said simulation model of the four-stroke engine 2' is implemented using said calculated lengths of the virtual connecting rods 21' and the other predefined configuration parameters. As explained, this step is generally implemented continuously, step (b) comprising in practice the updating of the length of the virtual connecting rods 21' as a parameter of said simulation model of the four-stroke engine 2'. In other words, at each time step the value of the connecting rod length parameter in the simulator is corrected, which makes this parameter dynamic and therefore makes it possible to obtain the variable character of the virtual connecting rod length 21'.

[0087] The only other difference that can possibly be foreseen in the parameterization of the simulation model is that of the valve opening phases, because the valve opening time as well as the scavenging time (which corresponds to the additional cooling time) are much longer on the five-stroke engine. In the context of this engine, it should be noted that the opening of the intake port is spread over two consecutive times, as shown in [Fig.4] (representing the intake and cooling times). Similarly, the opening of the exhaust port takes place over two consecutive times (exhaust and cooling). This configuration differs from the classic four-stroke engine configuration, where each valve traditionally opens during a specific phase.The simulation model can therefore be directly configured to apply a valve opening control law adapted to the five-stroke engine, or even to optimize some of its parameters as second operating parameters.

[0088] Finally, in a final step (c) which is again conventional, the method processes said so-called candidate configuration parameter value (obtained in step (a)) as a function of the at least one calculated parameter value representative of the performance of the simulated four-stroke engine 2', and returns the result to the interface 13 of the server 10.

[0089] By processing, we mean making a decision in the broad sense on the received value. It may only be a validation test of the engine 2 consisting of verifying that the calculated value of the parameter representing the performances is in accordance with a predefined threshold, and thus validating the candidate value obtained in step (a). The output is therefore a boolean. Thus, if the design of the engine is validated, the interface 13 returns this result.

[0090] Advantageously, it is possible to have several calculated values ​​of parameters representative of the performances corresponding to several parameter values ​​of the operating parameters of said five-stroke engine (or even several n-tuples of values ​​of the operating parameters of said five-stroke engine 2), including values ​​which are functions of time. Some operating parameters can be fixed and others not.

[0091] It is then possible to seek to verify that the said predefined threshold(s) of the parameter representative of the performances are respected whatever the values ​​of the operating parameters. Step (c) can in particular determine the most unfavorable value (in other words the worst, i.e. the lowest if one seeks to maximize the parameter and the highest if one seeks to minimize this parameter) of the parameter representative of the performances (among all the values ​​calculated for the various values ​​of the operating parameters), then compare this value with said threshold. For example, if the parameter representative of the performances is the level of exhaust emissions, one wishes to identify what is the maximum emission level that will be encountered in operation.Again, the output can be a boolean (we check that the threshold is respected whatever the operating parameters for the candidate value of the configuration parameters), or a range of values ​​of the operating parameters in which the threshold is respected.

[0092] Note that the values ​​of the second operating parameters are controllable by the engine 2 and normally adapted to the values ​​of the first operating parameters, so that certain combinations of values ​​of the first and two second parameters are in practice absurd. For example, for a low target power, the engine will logically lower the fuel injection flow rate, so that there is no point in testing a combination in which the flow rate is high.

[0093] In this respect, it is possible to vary only the values ​​of the first operating parameters (which, as we recall, correspond to the parameters undergone - varying the latter makes it possible to "test" the engine 2 in all circumstances) and:

[0094] - either, use engine 2 and its calculator to determine the appropriate values ​​of the second parameters (i.e. the server 10 sends to the engine a combination of values ​​of the first parameters and receives in response the corresponding combination of values ​​of the second parameters - the one that would be applied by the engine 2 in operation), and then calculate the corresponding value of the parameter representing the performances. This embodiment makes it possible to limit the number of variables (we only have the first parameters, since the second parameters become constrained) and therefore greatly accelerates the process.

[0095] - either optimize, using said four-stroke engine simulation model 2, the value of the performance representative parameter for these values ​​of the first parameters, i.e. determining the best value of the performance representative parameter that can be obtained for these values ​​of the first parameters. This is typically a step of constrained optimization of the values ​​of the second operating parameters, using the simulator to predict the value of the parameters representative of the performance of the engine 2 for candidate values ​​of the second operating parameters. In summary, for each combination of values ​​of the first parameters and the best value of the performance representative parameter is calculated, and the "worst of the best values" is determined.

[0096] In the latter case, for example, candidate values ​​of the second parameters are dynamically tested until optimized values ​​are found which allow the best values ​​of the parameters representative of the performances (for example the lowest CO2 / NOx emissions), or at least those which are sufficiently good (respecting a given criterion, for example below a legal emissions threshold). Again, any optimization technique of any existing simulator can be used, the invention relating to the idea of ​​introducing the virtual connecting rod 21' of variable length and not a simulation / optimization strategy in itself. We can therefore take the existing simulators, by just adding the brick for calculating the variable length as a function of the crankshaft angle and applying it in the simulator.

[0097] Optimization of configuration parameters

[0098] As explained, the present method is perfectly suited for testing values ​​of configuration parameters.

[0099] According to a more complex embodiment, illustrated by [Fig.3b], it is possible to seek to determine optimal values ​​of the configuration parameters, in particular so as to guide the design.

[0100] In this respect, step (b) can be implemented repeatedly for several values ​​of the configuration parameter(s), i.e. several candidate values ​​(or n-tuples of values) of the configuration parameters are obtained at once or during of several successive occurrences of step (a) (for example, we can repeat (a) and (b)). In other words, we test several configurations of the engine 2. Note that we can also have an engine 2 for each configuration, and in particular a test bench 1 comprising said different engines 2 so as to compare it using said simulation model. The processing of step (c) is then a determination of optimized value(s) of the configuration parameters, i.e. the selection, among the candidate values, of values ​​which allow the best values ​​of the parameters representative of the performances (for example the lowest CO2 / NOx emissions), or at least those sufficiently good (respecting a given criterion, for example below a legal emissions threshold)

[0101] In other words, preferably step (c) comprises the identification of the candidate value(s) making it possible to obtain the optimal values ​​of the parameters representative of the performances.

[0102] Thus, for each candidate value, the server 10 calculates the value of said parameter representative of the performances, which as we recall is preferably the worst obtained by varying the operating parameters (in particular the first parameters - which are undergone parameters).

[0103] In a similar manner to what has been proposed previously, any known optimization technique can be implemented to allow the process steps to be repeated until the optimized values ​​are obtained.

[0104] To return to the example of emissions to be minimized, in a particularly preferred embodiment:

[0105] 1 / provide a plurality of combinations of values ​​of the configuration parameters of engine 2 (candidate values).

[0106] 2 / for each of these combinations of values ​​of the configuration parameters to be tested, calculate the maximum predicted emissions by varying the values ​​of the first operating parameters, it being understood that for each combination of the values ​​of the first parameters, the minimum possible emissions are determined by optimizing the values ​​of the second operating parameters.

[0107] 3 / identify the values ​​of the configuration parameters of engine 2 minimizing the maximum emissions (i.e. the “best of the worst values”).

[0108] Note that we can have a single occurrence of step (c) at the end, or directly have an optimization strategy constructed in which after each step (b) we implement a step (c) combined with a following step (a), in which we determine the next candidate value of the configuration parameters based on the results of the previous steps (b), so as to converge. We then implement step (b) on the new candidate value obtained.

[0109] Server and test bench

[0110] According to a second aspect, the invention relates to the server 10 for implementing the method according to the first aspect.

[0111] The server 10 comprises data processing means 11 and generally data storage means 12, as well as an interface 13.

[0112] The data processing means 11 are configured to: - Obtain a value of at least one configuration parameter of a five-stroke engine 2; - Calculating, for at least one value of at least one operating parameter of said five-stroke engine 2, a value of at least one parameter representative of the performance of a simulated four-stroke engine 2', using a simulation model of said four-stroke engine 2' configured with said value obtained from at least one configuration parameter of the five-stroke engine 2, wherein, for each connecting rod 21 of the five-stroke engine (2), the simulated four-stroke engine 2' comprises a corresponding virtual connecting rod 21' having a variable length so as to reproduce the operation of the five-stroke engine 2; - Process said received configuration parameter value as a function of at least one calculated parameter value representative of the performance of the simulated four-stroke engine 2', and return the result to an interface 13 of the server 10.

[0113] According to a third aspect, the invention relates to a test bench assembly 1 comprising said server 10 and said engine 2 (or even several engines 2). The test bench 1 may further comprise sensors 3.

[0114] Computer program product

[0115] According to a fourth and a fifth aspect, the invention relates to a computer program product comprising code instructions for the execution (on the data processing means 11 of the server 10) of a method according to the first aspect of characterizing a five-stroke engine 2 of a vehicle 1; and a storage means (for example the data storage means 12 of the server 10) on which this computer program product is found.

Claims

Claims

1. Method for characterizing a five-stroke engine (2) for a vehicle, comprising implementing by data processing means (11) of a server (10) steps of: a. Obtaining a value of at least one configuration parameter of the five-stroke engine (2); b. Calculating, for at least one value of at least one operating parameter of said five-stroke engine (2), a value of at least one parameter representative of the performance of a simulated four-stroke engine (2'), using a simulation model of said four-stroke engine (2') configured with said obtained value of at least one configuration parameter of the five-stroke engine (2), wherein, for each connecting rod (21) of the five-stroke engine (2), the simulated four-stroke engine (2') comprises a corresponding virtual connecting rod (21') having a variable length so as to reproduce the operation of the five-stroke engine (2); c.Processing said received configuration parameter value as a function of at least one calculated parameter value representative of the performance of the simulated four-stroke engine (2'), and restitution of the result on an interface (13) of the server (10).

2. Method according to claim 1, wherein - the five-stroke engine (2) comprises a real crankshaft (23) in rotation and, for each real connecting rod (21), a real cylinder (22) and a real piston (20) in translation in the real cylinder (22), the real connecting rod (21) being of fixed length and connecting the real crankshaft (23) to the real piston (20), - the simulated four-stroke engine (2') comprises a virtual crankshaft (23') in rotation and, for each virtual connecting rod (21'), a virtual cylinder (22') and a virtual piston (20') in translation in the virtual cylinder (22'), the virtual connecting rod (21') of variable length connecting the virtual crankshaft (23') to the virtual piston (20').

3. Method according to the preceding claim, in which the real crankshaft (23) is of the epicyclic type, while the virtual crankshaft (23') is of the conventional type.

4. Method according to one of claims 2 and 3, in which, for each real connecting rod (21), the variable length of said corresponding virtual connecting rod (21') is such that for any angle of the virtual crankshaft (23'), the displacement of the virtual piston (20') in the virtual cylinder (22') is equal to the displacement of the real piston (20) in the real cylinder (22), at the same angle of the real crankshaft (23).

5. Method according to claim 4, wherein, for each real connecting rod (21), the variable length 1' of said corresponding virtual connecting rod (21') is expressed as a function of the angle 0 of the virtual crankshaft (23') by the formula r(0)=l+f4(0)-f5(0), where 1 is the fixed length of the real connecting rod (21), f5(0) is the displacement of the real piston (20) in the real cylinder (22), and f4(0) is the displacement that the virtual piston (20') would have in the virtual cylinder (22') if the real connecting rod length (21') were fixed and equal to the length of the real connecting rod (21).

6. A method according to claim 5, wherein said displacement that the virtual piston (20') would have in the virtual cylinder (22') if the actual connecting rod length (21') were fixed and equal to the length of the actual connecting rod (21), is a sinusoidal displacement of a four-stroke engine piston.

7. Method according to one of claims 2 to 6, wherein step (b) comprises, for any angle of the virtual crankshaft (23'), the following sub-steps: (bl) calculating the length of each virtual connecting rod (21') as a function of the angle of the virtual crankshaft (23'); (b2) implementing said simulation model of the four-stroke engine (2') using said calculated length of the virtual connecting rods (21').

8. A method according to claim 7, wherein step (b2) comprises updating the length of the virtual connecting rods (21') as a parameter of said simulation model of the four-stroke engine (2').

9. A method according to one of claims 1 to 8, wherein said five-stroke engine (2') comprises intake, compression, expansion, exhaust and cooling strokes.

10. A method according to one of claims 1 to 9, wherein said five-stroke engine (2') is a hydrogen engine.

11. A method according to one of claims 1 to 10, wherein step (a) comprises obtaining a plurality of values ​​of the at least one configuration parameter of the five-stroke engine (2); step (b) being implemented for each of said values ​​obtained from the at least one configuration parameter of the five-stroke engine (2); and step (c) comprising selecting an optimized value of the at least one configuration parameter of the five-stroke engine (2) from among said values ​​obtained from the at least one configuration parameter of the five-stroke engine (2), as a function of the calculated values ​​of the parameters representative of the performance of the simulated four-stroke engine (2').

12. Method according to one of claims 1 to 11, wherein said simulation model calculates the value of the at least one parameter representative of the performance of said simulated four-stroke engine (2') as a function of said value of the at least one operating parameter, in particular at least one first operating parameter and at least one second operating parameter.

13. Method according to one of claims 1 to 12, wherein step (b) is implemented for at least one value of at least one first operating parameter of said five-stroke engine (2), and comprises determining the value of at least one second operating parameter of the five-stroke engine (2) as a function of said value of the at least one first operating parameter of the engine (2).

14. A method according to claim 13, wherein step (b) comprises determining optimized values ​​of the at least one second operating parameter of the five-stroke engine (2), using the simulation model.

15. Method according to one of claims 13 to 14, in which the at least one first operating parameter is a parameter representative of the operating environment or a parameter imposed by the vehicle (1) such as a target power; and / or the at least one second operating parameter is chosen from ignition timing, fuel injection flow rate, and supercharging parameters.

16. Method according to one of claims 13 to 15, in which step (b) is implemented for a plurality of values ​​of the at least one first operating parameter.

17. Server (10), characterized in that it comprises data processing means (11) configured to: - Obtain a value of at least one configuration parameter of a five-stroke engine (2); - Calculate, for at least one value of at least one operating parameter of said five-stroke engine (2), a value of at least one parameter representative of the performance of a simulated four-stroke engine (2'), using a simulation model of said four-stroke engine (2') configured with said obtained value of at least one configuration parameter of the five-stroke engine (2), wherein, for each connecting rod (21) of the five-stroke engine (2), the simulated four-stroke engine (2') comprises a corresponding virtual connecting rod (21') having a variable length so as to reproduce the operation of the five-stroke engine (2);- Process said received configuration parameter value as a function of at least one calculated parameter value representative of the performance of the simulated four-stroke engine (2'), and return the result to an interface (13) of the server (10).;

18. Test bench (1) comprising said engine (2) and the server (10) according to claim 17.

19. Computer program product comprising code instructions for executing a method according to one of claims 1 to 16 for characterizing a five-stroke engine (2) for a vehicle, when said program is executed on a computer.

20. Storage means readable by computer equipment on which is recorded a computer program product comprising code instructions for the execution of a method according to one of claims 1 to 16 for characterizing a five-stroke engine (2) for a vehicle.

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