The present disclosure relates to fixed-speed engines and methods of cranking a fixed- speed engine and controlling a cylinder cut-out mode for an engine.

Background to the Disclosure

Fixed-speed engines are engines designed and configured to run at one fixed speed, or a limited number of fixed speeds. Fixed-speed engines may be used, for example, for electricity generation either as part of a main power generation scheme or as part of a standby/back-up power generation scheme. In one example use, fixed-speed engines may be used to generate electricity in the event of a failure of a mains power supply.

Consequently, some fixed-speed engines may be used occasionally and infrequently but must be reliable in order to be able to satisfactorily function as a standby/back-up power generator. It may be a primary requirement for a standby/back-up power generator that it can be started reliably and quickly in the event of a failure of a mains power supply.

In addition, fixed-speed engines may be used in a wide variety of environmental conditions. For example, fixed-speed engines used as standby/back-up power generators may be located inside or outside and may need to function in a variety of ambient conditions, including cold ambient conditions.

Summary of the Disclosure

An embodiment of the present disclosure provides a method of cranking a fixed-speed engine comprising the steps of: a) providing an engine start command; b) activating one or more cylinders of the fixed-speed engine; and c) activating a pilot injection mode during cranking of the engine wherein in the pilot injection mode each cylinder cycle of the one or more activated cylinders comprises one or more pilot injections followed by a main injection.

Another embodiment of the present disclosure provides a fixed-speed engine comprising a plurality of cylinders and a controller, the controller being configured, during cranking of the engine, to: activate one or more cylinders of the fixed-speed engine; and activate a pilot injection mode; wherein in the pilot injection mode each cylinder cycle of the one or more activated cylinders comprises one or more pilot injections followed by a main injection.

Another embodiment of the present disclosure provides a method of controlling a cylinder cut-out mode for a fixed-speed engine comprising the steps of: a) activating a cylinder cut-out mode in which one or more cylinders of the engine are deactivated while one or more cylinders of the engine remain activated; b) while the cylinder cut-out mode remains active injecting a main injection and optionally one or more pilot injections into the one or more activated cylinders during each cylinder cycle; and c) while the cylinder cut-out mode remains active injecting one or more pilot injections, but no main injection, into the one or more deactivated cylinders during each cylinder cycle.

Another embodiment of the present disclosure provides a fixed-speed engine comprising a plurality of cylinders and a controller, the controller being configured to: a) activate a cylinder cut-out mode in which one or more cylinders of the engine are deactivated while one or more cylinders of the engine remain activated; b) while the cylinder cut-out mode remains active, inject a main injection and optionally one or more pilot injections into the one or more activated cylinders during each cylinder cycle; and c) while the cylinder cut-out mode remains active, inject one or more pilot injections, but no main injection, into the one or more deactivated cylinders during each cylinder cycle.

Brief Description of the Drawings

One or more embodiments of the disclosure will now be described, by way of example only, with reference to the accompanying drawings in which:

Figure 1 is a schematic view of an engine and a controller;

Figure 2 is a schematic representation of various cylinder layouts for engines; Figure 3 is a schematic flow chart of an embodiment of a cylinder cut-out mode; Figure 4 is a graph of engine speed versus time for two engine configurations, A and B; and

Figure 5 is a graph of total hydrocarbon count versus time for the two engine configurations A and B. Detailed Description

Unless defined otherwise, all technical and scientific terms used in this specification have the same meaning as is commonly understood by the reader skilled in the art to which the claimed subject matter belongs. It is to be understood that the foregoing summary of the disclosure and the following examples are exemplary and explanatory only and are not restrictive of any subject matter claimed.

The following description is directed to embodiments of the disclosure. The description of the embodiments is not meant to include all the possible embodiments of the disclosure that are claimed in the appended claims. Many modifications, improvements and equivalents which are not explicitly recited in the following embodiments may fall within the scope of the appended claims. Features described as part of one embodiment may be combined with features of one or more other embodiments unless the context clearly requires otherwise.

In this specification, the use of the singular includes the plural unless the context clearly dictates otherwise. In this application, the use of “and/or” means “and” and “or” unless stated otherwise.

Figure 1 shows a schematic view of an engine 40 and a controller 41 for illustrating the present disclosure. The engine 40 may comprises a plurality of cylinders 42.

The engine 40 is a fixed-speed engine. The engine 40 may form part of generator, also referred to as a genset. The generator may be a stationary generator or mobile generator. The generator may be a standby generator. The generator may be used to generate electricity or electricity and useful heat in combination as part of a combined heat and power (CHP) generator.

Alternatively, the engine 40 may form part of a machine or may be a stand-alone engine. The machine may comprise a mobile or stationary machine. The machine may comprise a wheeled or tracked machine. The machine may be for use in the construction and/or mining industries. The machine may comprise a tractor, bulldozer, pipelayer, motorgrader, wheeled scraper, excavator, backhoe loader, track loader, wheel loader, articulated dump truck, rigid dump truck or roller, by way of example. The machine may comprise a locomotive. The engine 40 may be or comprise an internal combustion engine (ICE). The ICE may use diesel as its primary fuel. The diesel may, for example, be conventional diesel or biodiesel.

The engine 40 may have multiple cylinders 42. The engine may have 2 or more cylinders 42, optionally 4 or more cylinders 42, optionally 6 or more cylinders 42, optionally 8 or more cylinders 42, optionally 12 or more cylinders 42, optionally 16 or more cylinders 42, optionally 24 or more cylinders 42.

The engine 40 may have a fixed speed of, for example, 1500 to 1800 rpm. The fixed-speed may be 1500 rpm. The fixed-speed may be 1800 rpm. The engine 40 may have a single fixed-speed or may be configured to adopt a limited number of fixed-speeds. For example, the engine 40 may be switchable between running at 1500 rpm and running at 1800 rpm.

The engine 40 may have a compression ratio of less than 14:1.

The engine 40 may have a power density of greater than 20 bar gross BMEP, optionally greater than 28 bar gross BMEP, optionally greater than 30 bar gross BMEP.

The engine 40 may have a cylinder displacement of 3 litres or more per cylinder 42.

The engine 40 may have an engine displacement of 23 litres or more, optionally 23 to 61 litres.

The controller 41 may comprise hardware and/or software. The controller 41 may comprise a control unit or may be a computer program running on a dedicated or shared computing resource. The controller 41 may comprise a single unit or may be composed of a plurality of sub-units that are operatively connected. The controller 41 may be located on one processing resource or may be distributed across spatially separate computing resources. The controller 41 may comprise one or more programmable and or non-programmable memory units or sub-units. The controller 41 may comprise data storage and handling units or sub-units. The controller 41 may comprise or form part of an engine electronic control module (ECM) operatively connected to the engine 40. The controller 41 may utilise one or more variables associated with operation of the engine 40. The variables may comprise one or more of an engine speed 43, an engine coolant temperature 44, an engine intake manifold temperature 45 and an engine load factor 46.

The engine 40 and/or controller 41 may comprise one or more associated sensors for detecting, determining, calculating or inferring the aforementioned variables. For example, one or more of an engine coolant temperature sensor, an engine intake manifold temperature sensor, an engine speed sensor, an engine manifold absolute pressure sensor, a throttle position sensor and an air intake sensor may be provided.

A method of cranking the fixed-speed engine 40 is provided. The method comprises the steps of providing an engine start command, activating one or more cylinders 42 of the engine 40 and activating a pilot injection mode during cranking of the engine 40.

The fixed-speed engine 40 may comprise a starter motor to assist activation of the one or more cylinders 42 on receipt of the engine start command.

In the pilot injection mode each cylinder cycle of the one or more activated cylinders comprises one or more pilot injections followed by a main injection. The pilot injection mode may also be referred to as a “two shot” mode since it comprises at least two injections. A main injection mode (without any pilot injections) may also be referred to as a “one shot” mode.

In the present specification the term “cranking” means the period, following engine start, during which the engine speed is run up to obtain its desired fixed-speed.

In the present specification the term “activated”, “activating” and derivatives thereof with respect to the one or more cylinders 42 means that the one or more cylinders 42 is configured to receive at least a main injection per cycle that is combusted to provide useful power. In contrast, one or more of the cylinders 42 may be “deactivated” or “cut-out” so as not to receive a main injection per cycle that is combusted to provide useful power.

Cylinder deactivation/cut-out may be achieved, for example, by keeping the intake and exhaust valves closed for a particular cylinder 42 or by disabling the fuel injectors of a particular cylinder 42. The controller 41 may be configured to activate the pilot injection mode every time the engine 40 is cranked.

Alternatively, the controller 41 may be configured to check one or more entry conditions to determine whether to activate the pilot injection mode during cranking of the engine 40. In some embodiments the controller 41 may be configured to determine whether the engine coolant temperature 44 is below a pilot mode threshold temperature. If yes, the pilot injection mode may be activated during cranking; if no, the pilot injection mode may not be activated during cranking. The pilot mode threshold temperature for the engine coolant temperature 44 may be, for example, 60°C.

The engine start command may be provided by actuation of a virtual or physical key, switch, button or other actuator. In some embodiments the engine start command is provided by a key that is used to operate an ignition controller. Starting of the engine 40 may be under the control of the controller 41.

In the pilot injection mode, the one or more pilot injections may be injected, for example, at 13° to 17°, optionally at 15°, BTDC. The one or more pilot injections may, for example, have a total volume per cylinder per cycle of 30 mm ³ to 200 mm ³ , optionally 30 mm ³ to 80 mm ³ , optionally 30 mm ³ to 75 mm ³ , optionally 35 mm ³ , optionally 75 mm ³ to 200 mm ³ , optionally 80 mm ³ to 200 mm ³ .

The one or more pilot injections may, for example, have a total volume per cylinder per cycle that is 10% to 25% of the volume of the main injection.

In the pilot injection mode, the main injection may, for example, be injected at 3° to 7°, optionally at 5°, BTDC. The main injection may, for example, have a total volume per cylinder per cycle of 300 mm ³ to 800 mm ³ .

The pilot injection mode may remain active during the whole period of cranking of the engine 40. Alternatively, the pilot injection mode may be deactivated and a main injection mode (e.g. a one shot mode) commenced on the one or more activated cylinders 42 once the engine 40 obtains a speed within 250 rpm of its fixed-speed, optionally within 200 rpm of its fixed-speed, optionally within 100 rpm of its fixed-speed. In the main injection mode, for example, each activated cylinder 42 may receive only a main injection per cycle and no pilot injections. Such a main injection may, for example, be injected at 15°, BTDC. A comparison of the timings for an example of the pilot injection mode and an example of the main injection mode is provided in the table below:

The pilot injection mode may, for example, have a start of injection pressure of 30 to 40 MPa, optionally of 35 MPa.

In some embodiment the method may further comprise activating a cylinder cut-out mode during the cranking of the engine, wherein in the cylinder cut-out mode one or more cylinders of the engine are deactivated.

In the cylinder cut-out mode one pair or two pairs of cylinders may be deactivated, optionally an outermost one pair or two pairs of cylinders may be deactivated.

Figure 2 illustrates schematically four examples of configurations of deactivated cylinders.

In a) an inline 6-cylinder engine is shown with a cut-out mode in which one pair, the outermost pair, are deactivated (shown shaded) and the remaining cylinders are active (shown unshaded).

In b) an inline 8-cylinder engine is shown with a cut-out mode in which two pairs, the outermost pairs, are deactivated (shown shaded) and the remaining cylinders are active (shown unshaded).

In c) a V12-cylinder engine is shown with a cut-out mode in which two pairs, the outermost pair of each cylinder bank, are deactivated (shown shaded) and the remaining cylinders are active (shown unshaded).

In d) a V16-cylinder engine is shown with a cut-out mode in which four pairs, the outermost two pairs of each cylinder bank, are deactivated (shown shaded) and the remaining cylinders are active (shown unshaded). A cylinder cut-out mode may be activated during cranking of the engine 40 in combination with activation of the pilot injection mode as described above. In some embodiments the cylinder cut-out mode may always be activated during cranking of the engine 40 absent any error conditions. Alternatively the cylinder cut-out mode may be activated during cranking dependent on one or more entry conditions being met.

The cylinder cut-out mode may also be activated during idling of the engine 40 and/or during low load conditions of the engine 40 as discussed further below.

The cylinder cut-out mode may be activated at the start of cranking or after a time delay following the start of cranking. The cylinder cut-out mode may remain activated for the remainder of the cranking of the engine 40. In some embodiments the cylinder cut-out mode may be activated for the whole of the cranking period.

Optionally the cylinder cut-out mode may be deactivated during cranking dependent on one or more thresholds or variables or on encountering one or more error conditions.

Non-limiting examples of activation and deactivation of a cylinder cut-out mode will now be described.

Figure 3 shows a schematic flow chart of an embodiment of a cylinder cut-out mode according to the present disclosure.

At step 1 an engine start command is provided. As noted above, the engine start command may comprise actuation of a virtual or physical key, switch, button or other actuator.

At step 2, the controller 41 may check whether the enablement conditions for the cylinder cut-out mode are deemed as OK. The enablement conditions may be deemed as OK when one or more of the following statements are TRUE:

• the cylinder cut-out mode is enabled in the controller 41 ;

• no fault conditions are detected in the fuel injectors associated with the cylinders 42 of the engine 40;

• no fault conditions are detected associated with the engine speed 43 or engine speed sensor; and

• the engine speed 43 is not zero. Optionally, the enablement conditions may be deemed as OK only when all of the above statements are TRUE.

The cylinder cut-out mode may be enabled only once the enablement conditions have been deemed as OK.

If the enablement conditions are deemed as OK the method may move on to step 3.

If at step 2 the enablement conditions are not deemed as OK the method may move via arrow 21 to step 10. At step 10 the controller may designate the cylinder cut-out mode as OFF. The method may then move to step 11 in which the engine 40 may be cranked and/or run with the cylinder cut-out mode deactivated (i.e. with all cylinders 42 of the engine 40 being active) until the engine 40 is stopped by operation of the key (or other actuator).

At step 3, with the enablement conditions deemed as OK, the controller 41 may check whether entry conditions for the cylinder cut-out mode are MET. The entry conditions may be deemed as MET when one or more of the following statements are TRUE:

• the engine coolant temperature 44 is below or equal to an engine coolant temperature threshold;

• the engine intake manifold temperature 45 is below or equal to an engine intake manifold temperature threshold; and

• the engine load factor 46 is below or equal to an engine load factor threshold.

Optionally, the entry conditions may be deemed as MET only when all of the above statements are TRUE.

The cylinder cut-out mode may be entered only once the entry conditions have been deemed as MET.

The engine coolant temperature threshold may be set at a temperature of -60 to 150°C, optionally -40 to 90°C. The engine intake manifold temperature threshold may be set at a temperature of -60 to 300°C, optionally -40 to 60°C. The engine load factor threshold may be set at a percentage of 0 to 120%, optionally 1 to 100%. Optionally, one or more of the variables of the engine speed 43, the engine coolant temperature 44, the engine intake manifold temperature 45 and the engine load factor 46 may be associated with a debounce variable that may function to prevent the controller 41 calling on the respective variable too frequently or acting too hastily to the respective variable exceeding its threshold value. For example, the variable of the engine coolant temperature 44 may have a debounce variable set at a time of 0 to 60 seconds. For example, the engine intake manifold temperature 45 may have a debounce variable set at a time of 0 to 60 seconds. For example, the engine load factor 46 may have a debounce variable set at a time of 0 to 10 seconds.

At step 3, if the entry conditions are MET the method may move on to step 4.

At step 3, if the entry conditions are NOT MET the method may move via arrow 22 to step 10. At step 10 the controller may designate the cylinder cut-out mode as OFF. The method may then move to step 11 in which the engine 40 may be cranked or run with the cylinder cut-out mode deactivated until the engine 40 is stopped by operation of the key (or other actuator).

At step 4 the controller 41 may determine whether the engine speed 43 is below or equal to an engine speed threshold. The engine speed threshold may be a speed of 0 to 2000 rpm. At step 4, if the engine speed 43 is below or equal to the threshold then the method may optionally move via arrow 23 to step 10. At step 10 the controller may designate the cylinder cut-out mode as OFF. The method may then move to step 11 in which the engine 40 may be cranked/run with the cylinder cut-out mode deactivated (i.e. with all cylinders of the engine 40 being active) until the engine 40 is stopped by operation of the key (or other actuator).

At step 4, the controller 41 may determine whether the engine 40 is cranking or running. If the engine 40 is cranking, the method may move via arrow 24 to step 5. If the engine 40 is running, the method may move via arrow 25 to step 6.

The controller 41 may, for example, determine whether the engine 40 is cranking or running by monitoring the engine speed. The determinant may be, for example, a specified rpm engine speed or a predetermined offset from a desired rpm engine speed. For example, if a desired running speed (for example a fixed desired running speed) for the engine 40 is 1800 rpm the controller 41 may be configured to treat engine speeds below, for example, 1600 rpm as the engine 40 undergoing cranking and speeds above 1600 rpm as the engine 40 running. In another example, the controller 41 may be configured to treat engine speeds within, for example, 100 rpm or 200 rpm of a desired running speed as the engine 40 running and all lower speeds as cranking. The controller 41 may be configured such that once the engine 40 is determined to be running, the engine 40 cannot be determined to be cranking until the engine 40 is shut-off and restarted.

At step 5 the controller 41 may monitor a cranking functionality of the engine 40. The cranking functionality may be encountered, as noted above, during start-up of the engine 40.

At step 5 the controller 41 may check whether the enablement conditions for the cylinder cut-out mode are deemed as NOT OK. The enablement conditions may be deemed as NOT OK when one or more of the following statements are NOT TRUE:

• the cylinder cut-out mode is enabled in the controller 41 ;

• no fault conditions are detected in the fuel injectors associated with the cylinders 42 of the engine 40;

• no fault conditions are detected associated with the engine speed 43 or engine speed sensor;

• the engine speed 43 is not zero;

• the cylinder cut-out mode has been active for a time longer than 10 to 30 seconds.

Optionally, the enablement conditions may be deemed as NOT OK only when any one of the above statements are NOT TRUE.

If the enablement conditions are deemed as NOT OK the method may move on to step 10. At step 10 the controller may designate the cylinder cut-out mode as OFF. The method may then move to step 11 in which the engine 40 may be run with the cylinder cut-out mode deactivated (i.e. with all cylinders 42 of the engine 40 being active) until the engine 40 is stopped by operation of the key (or other actuator).

Additionally or alternatively the method may move via arrow 26 to step 10 if the cylinder cut-out mode is no longer requested by the controller 41, for example if the engine 40 is in a droop mode. Droop mode may be used as an engine load vs speed factor feature which allows the engine 40 to receive load as a function of engine speed. This may function as an open loop engine governor.

At step 5 if the enablement conditions are OK and the cylinder cut-out mode is still requested by the controller 41 then the cylinder cut-out mode may be activated during cranking and run up to the desired engine speed.

At step 5 if, during cranking, the engine coolant temperature 44 exceeds the aforementioned engine coolant temperature threshold then the method may move via arrow 28 to step 7. At step 7 the cylinder cut-out mode may be suspended (i.e. any de activated cylinders 42 may be reactivated) until the engine coolant temperature 44 returns under the engine coolant temperature threshold. Optionally, a coolant temperature hysteresis variable may be provided. The coolant temperature hysteresis variable may be for example 20°C. Optionally, the method may only return to step 5 via arrow 28 when the engine coolant temperature 44 has returned under a temperature equalling ‘the engine coolant temperature threshold minus the coolant temperature hysteresis variable’. For example, when:

Engine coolant temperature threshold = 90°C Coolant temperature hysteresis variable = 20°C the cylinder cut-out mode will be suspended when the engine coolant temperature 44 exceeds 90°C and will be reactivated once the engine coolant temperature 44 returns below 70°C (90°C - 20°C = 70°C).

As noted above, the engine coolant temperature 44 may have a debounce variable set at a time of 0 to 60 seconds. As such, the method may not move from step 5 to step 7 unless the engine coolant temperature 44 persists above the engine coolant temperature threshold for a period of at least that set as the debounce variable.

At step 5, the method may move via arrow 27 to step 6 once cranking has been completed. As noted above the point of moving from step 5 to step 6 may be determined by the controller 41 by monitoring the engine speed. The determinant may be, for example, a specified rpm engine speed or a predetermined offset from a desired rpm engine speed. As noted above, the cylinder cut-out mode may also be activated, or remain activated, during idling of the engine 40 and/or during low load conditions of the engine 40.

At step 6 the controller 41 may monitor an idle mode of the engine 40. The idle mode may be encountered, for example, during running of the engine 40 after start-up cranking and in particular may be encountered during idling of the engine 40 or when the engine is under low load conditions.

At step 6 if, during idling, the engine load factor 46 exceeds the aforementioned engine load factor threshold the method may move via arrow 33 to step 9 in which the controller 41 may monitor a loading functionality of the engine 40. As noted above, the engine load factor 46 may have a debounce variable set at a time of 0 to 10 seconds. As such, the method may not move from step 6 to step 9 unless the engine load factor 46 persists above the engine load factor threshold for a period of at least that set as the debounce variable.

At step 6 if, during idling, the engine coolant temperature 44 exceeds the aforementioned engine coolant temperature threshold then the method may move via arrow 29 to step 7. Step 7 functions in the same manner as described above, except that the method may return via arrow 29 to step 6 when the engine coolant temperature 44 returns under the engine coolant temperature threshold or engine coolant temperature threshold plus the coolant temperature hysteresis variable. The move from step 6 to step 7 may comprise a debounce variable as discussed above with respect to the move from step 5 to step 7.

At step 6 if, during idling, the engine speed 43 exceeds a desired engine speed (for example a desired engine idle speed) by greater than an engine speed threshold amount the method may move via arrow 30 to step 8 in which the controller 41 may pause the cylinder cut-out mode (i.e. temporarily reactivate any deactivated cylinders 42). The engine speed threshold amount may be a fixed value of rpm, a percentage value of the desired engine speed rpm, etc. For example, the engine speed threshold amount may be set at a value of 1 to 300 rpm. In one example the threshold amount is set as 30 rpm.

At step 8 the method may return to step 6 once the engine speed 43 has returned to within the engine speed threshold amount of the desired engine speed, optionally for a debounce time. On return to step 6 the cylinder cut-out mode may be un-paused. The debounce time may be for example a time from 0 to 10 seconds. The controller 41 may be configured with a pause limit variable to limit the number of times the method may visit step 8 before disabling the cylinder cut-out mode completely until the engine 40 is stopped and re-started. The pause limit variable may be 2, 3, 4 or 5 for example.

For example, when:

Desired engine idle speed = 1200 rpm Engine speed threshold amount = 200 rpm

Debounce time = 5 seconds Visit limit = 2 the method may function as follows:

At step 9 the controller 41 may monitor a loading functionality of the engine 40. The loading functionality may be encountered, for example, during running of the engine 40 when the engine is under medium or high load conditions. At step 6 and/or at step 9 the controller 41 may check whether the enablement conditions for the cylinder cut-out mode are deemed as NOT OK. The enablement conditions may be deemed as NOT OK when one or more of the following statements are NOT TRUE:

• the cylinder cut-out mode is enabled in the controller 41 ;

• no fault conditions are detected in the fuel injectors associated with the cylinders 42 of the engine 40;

• no fault conditions are detected associated with the engine speed 43 or engine speed sensor;

• the engine speed 43 is not zero;

Optionally, the enablement conditions may be deemed as NOT OK only when any one of the above statements are NOT TRUE.

If the enablement conditions are deemed as NOT OK the method may move from step 6 and/or from step 9 to step 10 via respective arrows 32 and 34. At step 10 the controller may designate the cylinder cut-out mode as OFF. The method may then move to step 11 in which the engine 40 may be run with the cylinder cut-out mode deactivated (i.e. with all cylinders 42 of the engine 40 being active) until the engine 40 is stopped by operation of the key (or other actuator).

Additionally or alternatively the method may move via respective arrows 32 and 34 to step 10 if the cylinder cut-out mode is no longer requested by the controller 41, for example if the engine 40 is in a droop mode.

Additionally or alternatively the method may move via respective arrows 32 and 34 to step 10 if the engine speed 43 exceeds an engine speed maximum threshold for the engine 40, which may be for example 50 rpm above the engine’s rated maximum speed and/or the engine load factor 46 exceeds an engine load factor maximum threshold for the engine 40, which may be for example 25% above the engine’s maximum rated load factor.

Additionally or alternatively the method may move via respective arrows 32 and 34 to step 10 if the controller 41 detects that a cylinder’s ability to combust fuel is compromised and/or if the controller 41 detects receipt of a Controller Area Network (CAN) Bus message indicating an intention to apply load to the engine 41. In some embodiments of the present disclosure there is provided a method of controlling the cylinder cut-out mode for the fixed-speed engine 40 which comprises the steps of: a) activating a cylinder cut-out mode in which one or more cylinders 42 of the engine 40 are deactivated while one or more cylinders 42 of the engine 40 remain activated; b) while the cylinder cut-out mode remains active injecting a main injection and optionally one or more pilot injections into the one or more activated cylinders 42 during each cylinder cycle; and c) while the cylinder cut-out mode remains active injecting one or more pilot injections, but no main injection, into the one or more deactivated cylinders 40 during each cylinder cycle.

This method may find particular application during running of the engine 40, i.e. after cranking of the engine 40 has been completed and the engine speed has reached or substantially reached the fixed-speed of the engine 40. However, this method may also additionally or alternatively be applied during cranking of the engine 40.

This method may be applied during running of the engine irrespective of whether a cylinder cut-out mode has been activated during cranking of the engine 40.

The one or more pilot injections that are injected into the one or more deactivated cylinders 42 may be injected at 30° to 40°, optionally at 35°, BTDC.

The one or more pilot injections that are injected into the one or more deactivated cylinders 42 may be injected at 10° to 30° prior to the main injection that is injected into the one or more activated cylinders 42.

The one or more pilot injections that are injected into the one or more deactivated cylinders 42 may have a total volume per cylinder per cycle of less than 50 mm ³ , optionally less than 40 mm ³ , optionally of 20 mm ³ to 40 mm ³ , optionally of 25 mm ³ to 35 mm ³ , optionally of 30 mm ³ .

The one or more pilot injections that are injected into the one or more deactivated cylinders 42 may have a total volume per cylinder per cycle that is 10% to 25% of the volume of the main injection that is injected into the one or more activated cylinders 42. The main injection may be injected at 3° to 7°, optionally at 5°, BTDC.

Industrial Applicability

The present disclosure may find application in fixed-speed engines and methods of cranking a fixed-speed engine and controlling a cylinder cut-out mode of a fixed-speed engine.

The engine may be or comprise an internal combustion engine (ICE). The ICE may use diesel as its primary fuel. In some examples the engine may be a diesel genset engine.

The present disclosure may find particular benefit where the engine is operated in cold conditions - for example where an ambient temperature surrounding the engine is less than 10°C. In such conditions, it can be a challenge to start an engine without starting aids, especially for ICEs that use diesel as the primary fuel. For example, in cold conditions there may be multiple cylinders that do not combust until load is applied to the engine or the engine coolant warms up. Poor incomplete combustion may lead to unfavourable conditions such as increased vibration, noise and emission of white smoke - indicative of unburnt hydrocarbons.

According to the present disclosure there is provided a method of cranking a fixed-speed engine comprising the steps of: a) providing an engine start command; b) activating one or more cylinders of the fixed-speed engine; and c) activating a pilot injection mode during cranking of the engine wherein in the pilot injection mode each cylinder cycle of the one or more activated cylinders comprises one or more pilot injections followed by a main injection.

Beneficially the one or more pilot injections may be injected at 13° to 17°, optionally at 15°, BTDC. Beneficially the one or more pilot injections may have a total volume per cylinder per cycle of 30 mm ³ to 200 mm ³ , optionally 30 mm ³ to 80 mm ³ , optionally 30 mm ³ to 75 mm ³ , optionally 35 mm ³ , optionally 75 mm ³ to 200 mm ³ , optionally 80 mm ³ to 200 mm ³ . Beneficially the one or more pilot injections may have a total volume per cylinder per cycle that is 10% to 25% of the volume of the main injection. Beneficially the main injection maybe injected at 3° to 7°, optionally at 5°, BTDC. Beneficially the main injection may have a total volume per cylinder per cycle of 300 mm ³ to 800 mm ³ . Beneficially the method may further comprise deactivating the pilot injection mode and commencing a main injection mode once the engine obtains a speed within 250 rpm of its fixed-speed, optionally within 200 rp of its fixed-speed, optionally within 100 rpm of its fixed-speed.

According to the present disclosure there is also provided a fixed-speed engine comprising a plurality of cylinders and a controller, the controller being configured, during cranking of the engine, to: activate one or more cylinders of the fixed-speed engine; and activate a pilot injection mode; wherein in the pilot injection mode each cylinder cycle of the one or more activated cylinders comprises one or more pilot injections followed by a main injection.

Advantageously, the method and engine of the present disclosure may enable faster start up of a fixed-speed engine allowing for a reduced cranking time, even in cold ambient conditions wherein an ambient temperature surrounding the fixed-speed engine is less than 10°C. This may enable a reduction in the total unburnt hydrocarbons (THC) emitted by the engine during cranking and may also reduce the vibration and noise of the engine.

Figures 4 and 5 and the table below provide test results for two engine configurations, A and B, where configuration B was configured with a pilot injection mode according to the present disclosure to be activated during cranking. In configuration A no pilot injection mode was active during cranking. In each configuration the engine was a Perkins 4006- 23TAG, an inline 6-cylinder engine with an engine displacement of 23 litres.

As demonstrated, the use of the pilot injection mode according to the present disclosure with configuration B resulted in a significantly faster start-up, resulting in the fixed-speed of the engine of 1500 rpm being obtained in 6.5 seconds after engine start compared to 14.5 seconds for configuration A. In addition, the total unburnt hydrocarbons were significantly reduced for configuration A, both with respect to the peak count and total count. In another test using the same engine, the timing of the main injection was varied for an engine running the pilot injection mode according to the present disclosure:

As demonstrated, the use of the pilot injection mode according to the present disclosure was found to be particularly beneficial when combined with a main injection timing of 3° to 7°, preferably 5°, BTDC.

According to the present disclosure there is provided a method of controlling a cylinder cut out mode for a fixed-speed engine comprising the steps of: a) activating a cylinder cut-out mode in which one or more cylinders of the engine are deactivated while one or more cylinders of the engine remain activated; b) while the cylinder cut-out mode remains active injecting a main injection and optionally one or more pilot injections into the one or more activated cylinders during each cylinder cycle; and c) while the cylinder cut-out mode remains active injecting one or more pilot injections, but no main injection, into the one or more deactivated cylinders during each cylinder cycle.

Beneficially the one or more pilot injections that are injected into the one or more deactivated cylinders may be injected at 30° to 40°, optionally at 35°, BTDC. Beneficially the one or more pilot injections that are injected into the one or more deactivated cylinders may be injected at 10° to 30° prior to the main injection that is injected into the one or more activated cylinders. Beneficially the one or more pilot injections that are injected into the one or more deactivated cylinders may have a total volume per cylinder per cycle of less than 50 mm ³ , optionally less than 40 mm ³ , optionally of 20 mm ³ to 40 mm ³ , optionally of 25 mm ³ to 35 mm ³ , optionally of 30 mm ³ . Beneficially the one or more pilot injections that are injected into the one or more deactivated cylinders may have a total volume per cylinder per cycle that is 10% to 25% of the volume of the main injection that is injected into the one or more activated cylinders. Beneficially the main injection may be injected at 3° to 7°, optionally at 5°, BTDC. According to the present disclosure there is also provided a fixed-speed engine comprising a plurality of cylinders and a controller, the controller being configured to: a) activate a cylinder cut-out mode in which one or more cylinders of the engine are deactivated while one or more cylinders of the engine remain activated; b) while the cylinder cut-out mode remains active, inject a main injection and optionally one or more pilot injections into the one or more activated cylinders during each cylinder cycle; and c) while the cylinder cut-out mode remains active, inject one or more pilot injections, but no main injection, into the one or more deactivated cylinders during each cylinder cycle.

Advantageously, the method and engine of the present disclosure may enable improved transient response of the engine when transitioning from a cylinder cut-out mode being active to being deactivated. In particular, while the quantity of the one or more pilot injections may not be sufficient to generate enough torque to maintain engine speed it can be enough to burn and therefore warm up the deactivated cylinders meaning that transient response will be improved when the deactivated cylinders are reactivated. Thus, beneficially even small volumes of pilot injection, e.g. less than 50 mm ³ can be utilised to improve engine performance.

It is to be understood that at least some of the figures and descriptions of the disclosure have been simplified to focus on elements that are relevant for a clear understanding of the disclosure, while eliminating, for purposes of clarity, other elements that the reader skilled in the art will appreciate may also be required. Because such elements are well known to the reader skilled in the art, and because they do not necessarily facilitate a better understanding of the disclosure, a description of such elements is not provided herein.

Further embodiments of the present disclosure are set out in the following clauses:

A1. A method of cranking a fixed-speed engine comprising the steps of: a) providing an engine start command; b) activating one or more cylinders of the fixed-speed engine; and c) activating a pilot injection mode during cranking of the engine wherein in the pilot injection mode each cylinder cycle of the one or more activated cylinders comprises one or more pilot injections followed by a main injection.

A2. The method of clause A1, wherein the one or more pilot injections are injected at 13° to 17°, optionally at 15°, BTDC.

A3. The method of clause A1 or clause A2, wherein the one or more pilot injections have a total volume per cylinder per cycle of 30 mm ³ to 200 mm ³ , optionally 30 mm ³ to 80 mm ³ , optionally 30 mm ³ to 75 mm ³ , optionally 35 mm ³ , optionally 75 mm ³ to 200 mm ³ , optionally 80 mm ³ to 200 mm ³ .

A4. The method of any preceding clause, wherein the one or more pilot injections have a total volume per cylinder per cycle that is 10% to 25% of the volume of the main injection.

A5. The method of any preceding clause, wherein the main injection is injected at 3° to 7°, optionally at 5°, BTDC.

A6. The method of any preceding clause, wherein the main injection has a total volume per cylinder per cycle of 300 mm ³ to 800 mm ³ .

A7. The method of any preceding clause, further comprising deactivating the pilot injection mode and commencing a main injection mode once the engine obtains a speed within 250 rpm of its fixed-speed, optionally within 200 rpm of its fixed-speed, optionally within 100 rpm of its fixed-speed.

A8. The method of any preceding clause, wherein in the pilot injection mode a start of injection pressure is 30 to 40 MPa, optionally 35 MPa.

A9. The method of any preceding clause, further comprising activating a cylinder cut-out mode during the cranking of the engine; wherein in the cylinder cut-out mode one or more cylinders of the engine are deactivated.

A10. The method of clause A9, wherein in the cylinder cut-out mode one pair or two pairs of cylinders are deactivated, optionally an outermost one pair or two pairs of cylinders are deactivated.

A11. The method of any preceding clause, wherein the fixed-speed engine has a fixed speed of 1500 to 1800 rpm.

A12. The method of any preceding clause, wherein the fixed-speed engine is a diesel engine.

A13. The method of any preceding clause, wherein the fixed-speed engine has a compression ratio of less than 14:1.

A14. The method of any preceding clause, wherein the fixed-speed engine has a power density of greater than 20 bar gross BMEP, optionally greater than 28 bar gross BMEP, optionally greater than 30 bar gross BMEP.

A15. The method of any preceding clause, wherein the fixed-speed engine has a cylinder displacement of 3 litres or more per cylinder; and/or wherein the fixed-speed engine has an engine displacement of 23 litres or more, optionally 23 to 61 litres.

A16. The method of any preceding clause, wherein an ambient temperature surrounding the fixed-speed engine is less than 10°C. A17. The method of any preceding clause, further comprising on receipt of the engine start command determining whether to activate the pilot injection mode during the cranking of the engine based on one or more pilot injection mode entry conditions; wherein the one or more pilot injection mode entry conditions are based at least on an engine coolant temperature.

A18. The method of clause A17, wherein if the determination is not to activate the pilot injection mode, activating a main injection mode during cranking of the engine such that each cylinder cycle comprises a main injection but no pilot injections.

A19. The method of clause A9 or clause A10, further comprising determining whether to activate the cylinder cut-out mode during the cranking of the engine, based on one or more cylinder cut-out mode entry conditions; wherein the one or more cylinder cut-out mode entry conditions are based on one or more of an engine coolant temperature, an engine intake manifold temperature and an engine load factor.

A20. A fixed-speed engine comprising a plurality of cylinders and a controller, the controller being configured, during cranking of the engine, to: activate one or more cylinders of the fixed-speed engine; and activate a pilot injection mode; wherein in the pilot injection mode each cylinder cycle of the one or more activated cylinders comprises one or more pilot injections followed by a main injection.

A21. The fixed-speed engine of clause A20, wherein the one or more pilot injections are injected at 13° to 17°, optionally at 15°, BTDC.

A22. The fixed-speed engine of clause A21 or clause A22, wherein: the fixed-speed engine is a diesel engine, optionally a diesel genset engine; and/or the fixed-speed engine has a fixed speed of 1500 to 1800 rpm; and/or the fixed-speed engine has a compression ratio of less than 14:1; and/or the fixed-speed engine has a power density of greater than 20 bar gross BMEP, optionally greater than 28 bar gross BMEP, optionally greater than 30 bar gross BMEP; and/or the fixed-speed engine has a cylinder displacement of 3 litres or more per cylinder; and/or the fixed-speed engine has an engine displacement of 23 litres or more, optionally 23 to 61 litres.

B1. A method of controlling a cylinder cut-out mode for a fixed-speed engine comprising the steps of: a) activating a cylinder cut-out mode in which one or more cylinders of the engine are deactivated while one or more cylinders of the engine remain activated; b) while the cylinder cut-out mode remains active injecting a main injection and optionally one or more pilot injections into the one or more activated cylinders during each cylinder cycle; and c) while the cylinder cut-out mode remains active injecting one or more pilot injections, but no main injection, into the one or more deactivated cylinders during each cylinder cycle.

B2. The method of clause B1 , wherein the one or more pilot injections that are injected into the one or more deactivated cylinders are injected at 30° to 40°, optionally at 35°, BTDC.

B3. The method of clause B1 or clause B2, wherein the one or more pilot injections that are injected into the one or more deactivated cylinders are injected at 10° to 30° prior to the main injection that is injected into the one or more activated cylinders.

B4. The method of any one of clauses B1 to B3, wherein the one or more pilot injections that are injected into the one or more deactivated cylinders have a total volume per cylinder per cycle of less than 50 mm ³ , optionally less than 40 mm ³ , optionally of 20 mm ³ to 40 mm ³ , optionally of 25 mm ³ to 35 mm ³ , optionally of 30 mm ³ .

B5. The method of any one of clauses B1 to B4, wherein the one or more pilot injections that are injected into the one or more deactivated cylinders have a total volume per cylinder per cycle that is 10% to 25% of the volume of the main injection that is injected into the one or more activated cylinders.

B6. The method of any one of clauses B1 to B5, wherein the main injection is injected at 3° to 7°, optionally at 5°, BTDC. B7. The method of any one of clauses B1 to B6, wherein while the cylinder cut-out mode is active one pair or two pairs of cylinders are deactivated, optionally an outermost one pair or two pairs of cylinders are deactivated.

B8. The method of any one of clauses B1 to B7, wherein the fixed-speed engine has a fixed speed of 1500 to 1800 rpm.

B9. The method of any one of clauses B1 to B8, wherein the fixed-speed engine is a diesel engine.

B10. The method of any one of clauses B1 to B9, wherein the fixed-speed engine has a compression ratio of less than 14:1.

B11. The method of any one of clauses B1 to B10, wherein the fixed-speed engine has a power density of greater than 20 bar gross BMEP, optionally greater than 28 bar gross BMEP, optionally greater than 30 bar gross BMEP.

B12. The method of any one of clauses B1 to B 11 , wherein the fixed-speed engine has a cylinder displacement of 3 litres or more per cylinder.

B13. The method of any one of clauses B1 to B12, wherein the fixed-speed engine has an engine displacement of 23 litres or more, optionally 23 to 61 litres.

B14. The method of any one of clauses B1 to B13, wherein an ambient temperature surrounding the fixed-speed engine is less than 10°C.

B15. A fixed-speed engine comprising a plurality of cylinders and a controller, the controller being configured to: a) activate a cylinder cut-out mode in which one or more cylinders of the engine are deactivated while one or more cylinders of the engine remain activated; b) while the cylinder cut-out mode remains active, inject a main injection and optionally one or more pilot injections into the one or more activated cylinders during each cylinder cycle; and c) while the cylinder cut-out mode remains active, inject one or more pilot injections, but no main injection, into the one or more deactivated cylinders during each cylinder cycle. B16. The fixed-speed engine of clause B15, wherein: the fixed-speed engine is a diesel engine, optionally a diesel genset engine; and/or the fixed-speed engine has a fixed speed of 1500 to 1800 rpm; and/or the fixed-speed engine has a compression ratio of less than 14:1; and/or the fixed-speed engine has a power density of greater than 20 bar gross BMEP, optionally greater than 28 bar gross BMEP, optionally greater than 30 bar gross BMEP; and/or the fixed-speed engine has a cylinder displacement of 3 litres or more per cylinder; and/or the fixed-speed engine has an engine displacement of 23 litres or more, optionally 23 to 61 litres.

C1. A method of controlling a fixed-speed engine comprising the method of cranking a fixed-speed engine according to any one of clauses A1 to A19 in combination with the method of controlling a cylinder cut-out mode for a fixed-speed engine according to any one of clauses B1 to B14.

D1. A fixed-speed engine according to any one of clauses A20 to A22 in combination with clause B15.