DE102023124041A1 - HYDROGEN COMBUSTION ENGINE - Google Patents

Abstract

Hydrogen internal combustion engine (100) with at least one closed control loop (101), with a sensor (103) for measuring the relative air-fuel ratio and / or the NOx concentration in the exhaust gas (105), which is connected downstream to a catalytic converter (107 ) is arranged; and a control unit (109) for controlling the supplied fuel quantity (111), the ignition angle, and/or the intake air mass flow based on the measured air-fuel ratio and/or the NOx concentration in the closed control loop (101).

Description

The invention relates to a hydrogen internal combustion engine and a method for controlling a hydrogen internal combustion engine.

Hydrogen combustion engines often operate on lean air/fuel ratios to achieve desired fuel efficiency. However, lean engine operation can produce nitrogen oxides (NOx). Nitrogen oxides are conventionally reduced to elemental nitrogen and oxygen in aftertreatment devices. However, the efficiency and effectiveness of these aftertreatment devices depend on the operating conditions of the hydrogen internal combustion engine. A measurement of the relative air-fuel ratio with a lambda sensor, which is arranged upstream in the exhaust gas in front of a catalytic converter, is not possible in these hydrogen combustion engines because the measurement accuracy is influenced by the hydrogen content in the exhaust gas.

The hydrogen internal combustion engine according to the invention with at least one closed control loop comprises a sensor for measuring the relative air-fuel ratio and/or the NOx concentration in the exhaust gas, which is arranged downstream of a catalytic converter, and a control unit for controlling the quantity of fuel supplied, the ignition angle and/or the intake air mass flow based on the measured air-fuel ratio and/or the NOx concentration in the closed loop. The hydrogen combustion engine achieves the technical advantage that it can be ensured that the relative air-fuel ratio in the closed control loop can be influenced by regulating the amount of fuel supplied and that nitrogen oxide emissions and the risk of abnormal combustion phenomena can be reduced, such as a knocking operation of the hydrogen combustion engine.

In an advantageous embodiment, the sensor (103) is a lambda sensor or a NOx sensor. This enables the technical advantage that the relative air-fuel ratio and/or the NOx concentration in the exhaust gas can be determined in a simple and reliable method.

In an advantageous embodiment, the control unit is designed to adjust a supplied amount of fuel such that the relative air-fuel ratio is above a predetermined lower limit. This adjustment can take place, for example, during a positive transient load jump of the hydrogen combustion engine. This enables the technical advantage of ensuring in a simple manner that the specified lower limit of the relative air-fuel ratio is never undershot. This reduces NOx emissions and the risk of abnormal combustion phenomena such as knocking or pre-ignition of the hydrogen combustion engine.

In a further advantageous embodiment, the control unit is designed to adapt an ignition point and/or a quantity of fuel supplied such that the NOx concentration is below a predetermined upper limit. This adjustment can take place, for example, during a positive transient load jump of the hydrogen combustion engine. This enables the technical advantage of ensuring in a simple manner that the specified upper limit of the NOx concentration is not exceeded at any time. This allows NOx emissions to be monitored and the risk of abnormal combustion phenomena, such as knocking or pre-ignition of the hydrogen combustion engine, to be reduced.

In a further advantageous embodiment, the control unit is designed to adapt an inlet air mass flow such that the relative air-fuel ratio is at a target value or in a target range. This enables the technical advantage that the stationary setpoint of the relative air-fuel ratio can be set in a simple manner without significantly influencing the engine torque.

In a further advantageous embodiment, the control unit is designed to increase an inlet pressure or an inlet air flow during the positive transient load jump. This enables the technical advantage of achieving a stationary airflow requirement.

In a further advantageous embodiment, the control unit is designed to calculate a maximum amount of fuel for the cylinder based on an amount of air supplied and/or a lower limit of the relative air-fuel ratio. This enables the technical advantage that the amount of fuel is limited in a simple manner even at the beginning of a positive transient load jump. This can be done, for example, before the lambda probe or the NOx sensor has obtained extensive measured values of the relative air-fuel ratio or the NOx concentration in the exhaust gas.

In a further advantageous embodiment, the control unit is designed to calculate the ignition point and/or a lower limit of the relative air-fuel ratio from an upper limit of the NOx concentration. This can be the case For example, using an inverse NOx model. This enables the technical advantage that the upper limit of the NOx concentration is taken into account even without regulation in the ignition timing of the hydrogen engine as well as in the lower limit of the relative air-fuel ratio.

In a further advantageous embodiment, the control unit is designed to detect a steady state when the inlet pressure, the inlet air flow and/or the air-fuel ratio are in a predetermined range, such as over a predetermined period of time. This enables the technical advantage that the stationary state is recognized in a simple manner and the control can be quickly adjusted.

In a further advantageous embodiment, the control unit is designed to carry out a closed-loop control or adjustment of the target air mass based on the measured relative air-fuel ratio. This can be done, for example, in the stationary state of the hydrogen combustion engine. This enables the technical advantage of reducing deviations of the relative air-fuel ratio from its steady-state setpoint.

In a further advantageous embodiment, the hydrogen internal combustion engine comprises a pressure sensor for measuring the inlet pressure. This enables the technical advantage that the pressure sensor can be used for control when no relative air-fuel ratio or NOx concentration sensor signal is available or the measured relative air-fuel ratio or NOx concentration sensor signal is available has excessive fluctuations or inaccuracies.

In a further advantageous embodiment, the hydrogen combustion engine is a lean hydrogen engine. This enables the technical advantage that the formation of nitrogen oxides in lean hydrogen engines can be regulated in a simple manner.

A vehicle according to the invention with the hydrogen internal combustion engine achieves the same technical advantages as the hydrogen internal combustion engine.

The method according to the invention for controlling a hydrogen internal combustion engine with at least one closed control loop comprises the steps of measuring the relative air-fuel ratio and / or the NOx concentration in the exhaust gas by means of a sensor which is arranged downstream of a catalytic converter; and controlling the amount of fuel supplied, the ignition timing and/or the intake air mass flow based on the air-fuel ratio and/or the measured NOx concentration in the closed loop. This process achieves the same technical advantages as the hydrogen combustion engine.

• 1 eine schematische Darstellung eines Wasserstoff-Verbrennungsmotors mit einem geschlossenen Regelkreis;
• 2 eine graphische Darstellung verschiedener Betriebsparameter eines Wasserstoff-Verbrennungsmotors; und
• 3 eine schematische Darstellung eines Verfahrens zum Steuern eines Wasserstoff-Verbrennungsmotors mit einem geschlossenen Regelkreis.

Embodiments of the invention are explained in more detail using the following figures. Show:

• 1 a schematic representation of a hydrogen internal combustion engine with a closed loop;
• 2 a graphical representation of various operating parameters of a hydrogen internal combustion engine; and
• 3 a schematic representation of a method for controlling a hydrogen internal combustion engine with a closed control loop.

1 shows a schematic representation of a hydrogen internal combustion engine 100 with a closed control loop 101. The air is passed into the combustion chamber 119 via a throttle valve 117. The air is filtered using an air filter 121 and cooled via a charge air cooler 123 (CAC - Charge Air Cooler). Gaseous hydrogen is supplied under increased pressure via a hydrogen supply through a storage injection 125 (common rail) directly into the combustion chamber 119 and mixed there with the introduced air. The charge mixture generated in this way is ignited using spark plugs and ignition coils, so that the hydrogen internal combustion engine 100 is driven.

The resulting exhaust gas 105 drives a turbocharger 127 with variable geometry (VGT - Variable-Geometry Turbocharger) and is directed to the exhaust through the catalytic converter 107 and an exhaust silencer 129. The catalyst 107 is formed, for example, by an oxidation catalyst (OC - Oxidation Catalyst), a three-way catalyst (TWA - Three Way Catalyst) or a passive NOx absorber (PNA - Passive NOx Absorber). The turbocharger 127 drives a compressor 131, which brings the pressure of the supplied air to the increased pressure level.

The relative air-fuel ratio λ in the exhaust gas is measured by means of a lambda sensor 103 or a NOx sensor arranged downstream of the catalytic converter 107. The lambda sensor 103 determines the residual oxygen content in the exhaust gas with the oxygen content of a reference, usually the current outside air. From this the combustion air ratio λ (ratio of Ver combustion air to fuel) can be determined and adjusted. Corresponding measured values for the air-fuel ratio are sent to the control unit 109 as a feedback signal. In addition to the relative air-fuel ratio, a NOx sensor can also determine the NOx concentration in the exhaust gas and deliver corresponding measured values to the control unit 109.

The electronic control unit 109 uses the measured values obtained to control or adjust the supplied fuel quantity 111 so that a predetermined lower limit of the relative air-fuel ratio is not exceeded during a positive transient load jump of the hydrogen internal combustion engine 100; and/or to control or adjust the ignition timing and the amount of fuel supplied so that a predetermined upper limit of the NOx concentration is not exceeded. The control or adjustment of the supplied fuel quantity 111 and the ignition timing in turn influence the relative air-fuel ratio and the NOx concentration in the exhaust gas. In this way, the closed control loop 101 is established based on the measured values and the air-fuel ratio remains above the predetermined lower limit and a NOx concentration remains below the predetermined upper limit.

The exhaust gas behind the catalytic converter 107 is free of hydrogen, so that the lambda sensor or the NOx sensor 103 is suitable for control downstream of the catalytic converter 107. This arrangement of the lambda probe or the NOx sensor 103 can ensure a higher measurement accuracy of the lambda probe or the NOx sensor.

2a until 2d show graphic representations of various operating parameters of the hydrogen combustion engine, namely a time course 133 of the torque in Nm ( 2a) , a time course 135 of the relative air-fuel ratio in the exhaust gas ( 2 B) , a time course 137 of the air mass supplied in mg per stroke (mgs/str - milligrams per stroke) ( 2c ) and a time course 139 of the fuel mass in mg per stroke ( 2d ). These operating parameters are shown during a stationary operating state in areas A and C and during a positive transient load jump in the dynamic operating state of the hydrogen internal combustion engine 100 in area B.

The steady-state operating state occurs when no additional torque is requested. The requested torque 141 and the generated torque 133 match in this case. The hydrogen combustion engine 100 is driven at a constant speed. The stationary operating state occurs, for example, when a vehicle travels at a constant speed.

In the stationary operating state, the curve 135 of the relative air-fuel ratio in the exhaust gas is constant. In the stationary operating state, control of the air-fuel ratio can then be carried out with an open control loop to adapt the supplied fuel quantity 101 on the basis of a predetermined stationary setpoint 143. At lean relative air-fuel ratios, for example greater than 2, NOx emissions are lower and the requirements for accuracy of the relative air-fuel ratio control are correspondingly lower. In addition, the setpoint 143 for the air-fuel ratio can be adjusted depending on the operating situation of the hydrogen internal combustion engine 100 and therefore differ over time.

In the stationary operating state, the time profile 137 of the air mass supplied is also constant and corresponds to a predetermined target value 145 for the air mass supplied. The setpoint 145 for the supplied air mass can also be adjusted depending on the operating situation of the hydrogen combustion engine 100 and therefore also differ over time. The same applies to the time course 139 of the supplied fuel mass and the setpoint 147 for the fuel mass.

In the dynamic operating state, which lies between the two stationary operating states, a torque is suddenly requested. This creates a positive transient load jump. The requested torque 141 and the generated torque differ in this case and the speed of the hydrogen internal combustion engine 100 increases until the requested torque 141 and the generated torque match again (area B in 2a) .

Since in the dynamic operating state during the positive transient load jump the relative air-fuel ratio drops suddenly due to an increase in the amount of fuel supplied, the control unit 109 regulates the amount of fuel 111 supplied based on the measured air-fuel ratio with a closed control loop 101 through. The air-fuel ratio is regulated so that it does not fall below a predetermined lower limit 113. With a NOx sensor, the ignition timing and the supplied fuel quantity 111 can also be controlled or adjusted based on the measured NOx concentration, in order not to exceed a specified upper limit.

At the beginning of the dynamic operating state, the setpoint 143 for the air-fuel ratio, the setpoint 145 for the supplied air mass and the setpoint 147 for the supplied fuel mass can also be changed by the control unit 109. Accordingly, the time course 137 of the supplied air mass and the time course 139 of the supplied fuel mass also increase in the dynamic operating state.

A maximum upper limit 149 for the fuel mass supplied can be calculated by the control unit 109 from the limit value for the lower limit 113 of the relative air-fuel ratio and the air mass actually supplied. The actual air mass supplied can be calculated from a filling model using an inlet pressure sensor. At the beginning of the transient load step, this value limits the fuel mass and is adjusted as soon as the controls for the relative air-fuel ratio and/or the NOx concentration are active.

During the transient load jump, the intake pressure and/or the intake airflow are increased, for example by opening the throttle valve 117 (de-throttling or boosting), to achieve the steady-state target intake airflow. The target intake airflow is determined by the target steady-state fuel mass and the relative air-fuel ratio. Since the inlet pressure and the inlet air flow cannot be used to control the relative air-fuel ratio during the transient load jump, the fuel mass is used as a control variable. Thereby, the limit value for the lower limit 113 of the air-fuel ratio can be secured. The feedback signal from the lambda sensor or the NOx sensor 103 is used.

The controls for the amount of fuel supplied and the ignition timing to maintain the air ratio and/or the NOx concentration can be activated permanently or only during a transient load jump.

In the case of the transient load jump, the control loop 101 may be activated for a predetermined time after a load request that reaches the lower limit limit 113 or when a measured relative air-fuel ratio reaches the lower limit limit 113. The signal for the control circuit 101 is generated by either the lambda sensor or the NOx sensor 103 in the exhaust gas of the hydrogen internal combustion engine 100.

The control loop 101 may be deactivated when it is detected by the control unit 109 that the actual intake pressure, intake airflow, or relative air-fuel ratio reaches the steady-state range. The control device 109 recognizes this, for example, if the values again assume a constant course after a positive transient load jump and lie in a predetermined range over a predetermined time.

On the other hand, permanently or in the stationary state of the hydrogen combustion engine, the control unit can activate a closed control or adjustment of the target air mass based on the measured relative air-fuel ratio. Using intake airflow to control the relative air-fuel ratio has a smaller impact on engine torque compared to using fuel flow and is therefore less noticeable to an operator. The adjustment of the setpoint for the inlet air flow is limited by the expected tolerances when detecting the inlet air flow. For this purpose, a plausibility check of the inlet air flow and exhaust gas recirculation (EGR) can be carried out with a model and sensor tolerances.

If a control error in the relative air-fuel ratio is higher than would be expected from the tolerances and cannot be caused by inaccuracies in the air path, the fuel mass 111 delivered may be adjusted to achieve the steady state range. In addition, it can be determined whether there is a general fuel error in the injectors if it is also assumed that a valid signal from the lambda sensor or the NOx sensor 103 is present. This can be determined by using a second oxygen sensor or NOx sensor 103 located further downstream in the aftertreatment system.

The hydrogen internal combustion engine 100 corrects errors in the amount of fuel supplied and the actual actual intake air flow to ensure the air-fuel ratio and NOx emissions. In transient operation, the amount of fuel supplied and/or the ignition timing are adjusted and in steady-state operation, the intake air flow or a model for the intake air flow in the cylinder, which is used to calculate the maximum limit, is corrected accordingly

3 shows a schematic representation of a method for controlling the hydrogen internal combustion engine 100 with the closed Control circuit 101. In step S101, the relative air-fuel ratio in the exhaust gas is first measured using the lambda sensor 103 or the NOx sensor, which is arranged downstream of the catalytic converter 107. In the subsequent step S102, the supplied fuel quantity 111 is controlled based on the measured air-fuel ratio in the closed control loop 101.

The method enables the advantage of ensuring that the relative air-fuel ratio can be maintained above a predetermined critical lower limit 113 in a simple manner. Falling below this lower limit 113 can produce high NOx emissions that exceed a possible urea dosage and conversion capability of the SCR aftertreatment system. A similar and additional control loop for adjusting the ignition timing and fuel quantity based on the measured NOx concentration can ensure that NOx emissions do not exceed a predetermined critical upper limit.

The process reduces unusual combustion phenomena such as knocking and pre-ignition and limits NOx emissions. Abnormal combustion in dynamic operating conditions is reduced, for example in the event of a positive transient load jump. Furthermore, resulting engine tolerances can be compensated for over the service life of the hydrogen internal combustion engine 100 by regulating the relative air-fuel ratio. Through this method, the steady state of the relative air-fuel ratio can be enabled by controlling or adjusting the intake air flow, for example by adjusting the intake pressure, the cylinder charge or the mixture via the throttle valve. Control can also be based on the turbocharger 127 with variable geometry (VGT), exhaust gas recirculation (EGR), variable valve timing (WT - Variable Valve Timing) and / or a variable valve lift (WL - Variable Valve Lift).

All features explained and shown in connection with individual embodiments of the invention can be provided in different combinations in the object according to the invention in order to simultaneously realize their advantageous effects.

All method steps can be implemented by devices that are suitable for carrying out the respective method step. All functions that are carried out by physical features can be a procedural step of a process.

Claims (10)

Hydrogen internal combustion engine (100) with at least one closed control loop (101), with: - a sensor (103) for measuring the relative air-fuel ratio and/or the NOx concentration in the exhaust gas (105), which is arranged downstream of a catalytic converter (107); and - a control unit (109) for controlling the quantity of fuel supplied (111), the ignition angle and/or the intake air mass flow based on the measured air-fuel ratio and/or the NOx concentration in the closed control loop (101). Hydrogen combustion engine (100). Claim 1 , wherein the sensor (103) is a lambda sensor or a NOx sensor. Hydrogen internal combustion engine (100) according to one of the preceding claims, wherein the control unit (109) is designed to adjust a supplied fuel quantity (111) such that the relative air-fuel ratio is above a predetermined lower limit (113). Hydrogen internal combustion engine (100) according to one of the preceding claims, wherein the control unit (109) is designed to adjust an ignition point and / or a supplied fuel quantity (111) such that the NOx concentration is below a predetermined upper limit. Hydrogen internal combustion engine (100) according to one of the preceding claims, wherein the control unit (109) is designed to adjust an intake air mass flow such that the relative air-fuel ratio is in a target range. Hydrogen internal combustion engine (100) according to one of the preceding claims, wherein the control unit (109) is designed to increase an intake pressure or an intake air flow during the positive transient load jump. Hydrogen internal combustion engine (100) according to one of the preceding claims, wherein the control unit (109) is designed to calculate a maximum amount of fuel for the cylinder based on an amount of air supplied and / or a lower limit of the relative air-fuel ratio. Hydrogen internal combustion engine (100) according to one of the preceding claims, wherein the control unit (109) is designed to control the ignition timing and/or a lower limit of the relative Air-fuel ratio to be calculated from an upper limit of the NOx concentration. Hydrogen combustion engine (100). Claim 5 , wherein the control unit (109) is designed to detect a steady state when the inlet pressure, the inlet air flow and / or the air-fuel ratio are in a predetermined range. Method for controlling a hydrogen internal combustion engine (100) with at least one closed control loop (101), with the steps: - Measuring (S101) the relative air-fuel ratio and/or the NOx concentration in the exhaust gas by means of a sensor (103) which is arranged downstream of a catalytic converter (107); and - Controlling (S102) the quantity of fuel supplied (111), the ignition timing and/or the intake air mass flow based on the air-fuel ratio and/or the measured NOx concentration in the closed control loop (101).

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