Configurable fuel injection system in an opposed piston engine

This disclosure describes a fully configurable injection system which can accomplish additional application cases than what is mentioned in US 2013/0104848, specifically the case where an injector is fired less than 2 times per engine rev

Inventor: Daniel Schum

Date of disclosure: Oct 7, 2015 Rev 1: Nov 13, 2015

Date of Invention: March 19, 2015

Background

An opposed piston engine can have more than one fuel injector mounted in each cylinder.  With multiple fuel injectors there is increased flexibility with how fuel is delivered to the cylinder with respect to a tradition system that has a single injector.  This disclosure describes a fuel injection system which can take advantage of this flexibility for various applications each having their own requirements.

Achates has filed an application number US 2013/0104848 titled “fuel injection strategies in opposed piston engines with multiple fuel injectors” describing various fuel injection strategies.  This application focuses on applications where every injector is firing more than once per engine rev, meaning every injector is firing at least a pilot + main event.

Achates has filed disclosure number 365 titled “FI Strategy for an OPE” describing a system which can have different flow rate injectors within a single cylinder.  This disclosure also has a flow chart showing how to split the fuel quantity between the two injectors in a cylinder

Novelty:

This disclosure describes a fully configurable injection system which can accomplish additional application cases than what is mentioned in US 2013/0104848, specifically the case where an injector is fired less than 2 times per engine rev (main only).

Additionally US 2013/0104848 focuses on the time at which different injections or injectors fire without discussing much about the quantity of fuel for each injection.

Invention:

Achates has developed a fully configurable fuel injection system.  Figures 5a, 5b, 6, 7 in disclosure 365 detail the software flow for a given cylinder.  This system can be applied to any number of injectors per cylinder and any number of engine cylinders.

A follow disclosure to D365 titled “Injection strategy with duel fuel pressures for opposed piston engine” has been filed by Achates which details our fuel control system in figures 5a, 5b, 6, 7 for a system which can have different rail pressures on bank A vs bank B.  The difference from D365 is just this, different rail pressures as an option.  These figures are reproduced below:

1

Figure 2

Figure 3

The Achates injection system is unique because the different injectors can be controlled completely independently of each other.  This means the following can be achieved:

  1. Different injectors within a given cylinder can have different fuel quantities relative to each other, per injection event.  For example if there are two injectors then #1 may have a larger main injection quantity than #2.  Or they may have the same quantity.  Or the pilots may have a different quantity while the mains have the same quantity.  This applies to all events possible: pilot, main, post, and any other names that apply to injection events within an engine revolution.  See Figure 1

Figure 1

Figure 1

2. Different injectors within a given cylinder can have different fuel injection angles relative to each other, per injection event.  For example if there are two injectors then #1 may have a main injection that starts at 5 deg before top dead center (TDC) while #2 starts at 2 deg.  Or they may start at the same angle.  Or the pilots may start at different angles while the mains do not.  This applies to all events possible: pilot, main, post, and any other names that apply to injection events within an engine revolution.  See Figure 2

Figure 2

Figure 2

3. Different injectors within a given cylinder can have a different number of injection events relative to each other.  For example if there are two injectors then #1 may have a main injection only while #2 has both a pilot and main.  Or the injectors may have the same number of events.  They all may have a main injection only or all have pilot plus main.  This applies to all events possible: pilot, main, post, and any other names that apply to injection events within an engine revolution.  See Figure 3

Figure 3

Figure 3

a.  A subcase to this is when less fuel is required than two injectors can deliver.  In this case all events can be turned off except for one injection in one injector per cylinder.  This may be required in very low flow situations like idle.  For example if there are two injectors in a cylinder then #1 can fire a main injection event only while #2 does not fire.  See Figure 4

Figure 4

Figure 4

4.  These above 3 methods can be combined with each other.  See Figure 8

Figure 8

Figure 8

Additionally the Achates system can adjust the fueling parameters (quantity, angle, number of events) per cylinder.  So every injector can be controlled independent on the other injectors on the engine.

Different applications have different requirements.  US 2013/0104848 describes many cases involving two injectors in a cylinder each firing at least 2 events per revolution.  Some additional cases not mentioned there which our system can support (for these examples we will use two injectors per cylinder referred to as A and B):

1. A and B both have only main injections.  See figure 9

a. Main injections start at the same and deliver the same quantity
b. Main injections start at the same and deliver different quantities
c. Main injections start at different angles and deliver the same quantity
d. Main injections start at different angles and deliver different quantities

Figure 9

Figure 9

2. A has both a pilot and main injection while B has only main injection.  Or B has both a pilot and main injection while A has only main injection.  See figure 10

a. Main injections start at the same and deliver the same quantity

b. Main injections start at the same and deliver different quantities

c. Main injections start at different angles and deliver the same quantity

d. Main injections start at different angles and deliver different quantities

Figure 10

Figure 10

3. A has both a post and main injection while B has only main injection.  Or B has both a post and main injection while A has only main injection.  See figure 11

a. Main injections start at the same and deliver the same quantity

b. Main injections start at the same and deliver different quantities
c. Main injections start at different angles and deliver the same quantity
d. Main injections start at different angles and deliver different quantities

    Figure 11Figure 11

    4. Only injector A fires.  Or only injector B fires.  See figure 4.

    Control system architecture:

    This fuel injection control system can be implemented in any number of systematic ways as far as the hardware layout is concerned.  Claim 21 of US 2013/0104848 discusses a control unit and injector driver as if they are separate devices, however this does not have to be the case so we do not want to limit our scope to that implementation.  There could be any number of control units >= 1 and there could be any number of injector drivers >= 1.  The injector driver could be inside the control unit or outside.  There could be one control unit for each side of the engine or one total.  There could be a specific injector driver for each injector.  There could be any number of control units and internal or external injector drivers connected together to form the system.  The only binding quality is electronic control of the system and hardware necessary to drive the injectors.