The dual fuel system substitutes diesel by gas in order to significantly reduce fuel cost. The investment for the conversion is in general paid back within a few months.
Lambda Control International (LCI) offers 3 dual fuel system configurations for industrial engines.
In all 3 configurations the ratio between diesel and gas can be programmed throughout the entire speed and load range of the engine. This is made possible while maintaining original engine performance. The dual fuel will give customers the ability to return to full diesel operation at any desired time.
- Single Point Trim (SPT) for engine speed over 1200 rpm and typical smaller than 600kW
- Single Point Injection (SPI) for engine speed over 1200 rpm and typical larger than 250 kW
- Multipoint Injection (MPI) for engine speed below 1200 rpm or any application where emission limits are critical.
The SPI and SPT systems requires minimal mechanical conversion of the engine as it consists of “bolt on components” only. The MPI-solution requires installation of a gas injector near each cylinder head. MPI Engine conversion is therefore considered more invasive.
The dual fuel system incorporates significant amount of sensors, which are not only used to control the gas flow, but also provide engine protection. The dual fuel system monitors the following parameters:
- Exhaust temperature
- Intake manifold temperature
- Jacket water temperature
- Engine speed and irregularity (misfire)
- Air cleaner restriction
- Diesel supply temperature
- Turbo boost pressure
- Diesel flow or diesel actuator position
- Power signal (kW-transducer for generator sets)Initially the dual fuel control reduces the gas flow rather than stopping the gas flow when the engine operates outside normal conditions. The amount of reduction is tunable by the commissioning engineer. If the automatic reduction of the dual fuel system does not achieve the desired result, the system will return to full diesel operation or shutdown the engine.
On top of the above listed standard protection, LCI believes that a detonation detection system is required for dual fuel operated engines.
The standard dual fuel system operates with a highly accurate knock detection system. For smaller engines a low cost vibration sensor protection solution can be provided, although effectiveness of the latter requires evaluation per engine model.
Knock Control (Conventional)
In the event of detonation, the dual fuel system will instantly reduce the gas flow by fixed amount and after a set timer return to the ratio as before the detonation event. At continued detonation or repetition, the system will return to full diesel operation.
Knock Border Control
For SPI and MPI an alternative detonation control algorithm can be offered. With Knock Border Control the gas amount is increased in small steps right up to the knock border and operation is maintained at that point, maximizing the substitution rate. This algorithm is only active above a minimum load to avoid excessive unburned emissions.
The Knock Border Control can be offered for the SPI and MPI systems in combination with the AKR-3 knock control only, as accurate gas control and detonation detection is crucial.
The Knock Border Control algorithm made it possible to operate a Caterpillar D3512 on crude and its “break out”-gas. Gas parameters such as quality, availability and general very low methane number vary continuously on site and the dual fuel system deals with all these variations without any human intervention.
The dual fuel systems use predominantly existing Woodward hardware. The same hardware which is supplied to engine manufactures around the globe with many years of trouble free operation on gas engines.
At operation of the engine outside normal OEM specifications i.e. high aftercooler or jacket water temperature, the gas flow will either be reduced or stopped to ensure safe engine operation. At any time it is possible to return to full diesel operation to ensure reliability of the unit.
Gas introduction into a diesel engine impacts the exhaust emissions. In general the NOx emission reduces as well as CO2, which is beneficial. LCI programs a curve in the dual fuel control to minimize the CO and unburned emissions at low load levels. Also the dual fuel system is compatible with existing emission reduction technologies such as DOC and SCR to optimize emissions as desired. Maximum fuel efficiencies can be achieved with the multipoint injection system where the gas injection is perfectly timed for each cylinder individually. Typical diesel substitution curve which is programmed in the control to maximize fuel cost savings, minimizes unburned emissions and provides sufficient detonation margin.
Natural gas and continue variable gas qualities
All dual fuel systems supplied by LCI can operate with either fixed or varying quality gasses. The systems compensates the gas flow in order to maintain the predefined diesel gas ratio automatically. The automatic compensation makes the dual fuel system therefore suitable for natural, CNG, LNG, coal bed methane/coal seam and variable gases like bio, sewage, landfill, mine and syngas.
The dual fuel system has been designed for any industrial application, being fixed or variable speed and even mobile applications:
Generator sets / drill rigs Variable speeds:
* Continues operation * Compressor applications
* Prime power * Water pump applications
* Standby power * Mining trucks and off road vehicles
Variable Gas Diesel Ratio
Standard in our dual fuel controls, the gas diesel ratio is variable versus speed and load by using either a 2- or 3-dimensional table. This allows the commissioning engineer to optimal balance maximum substitution of diesel while controlling emissions and maintain sufficient margin to detonation.
Standard Speed Control
Traditional Diesel-Gas conversions for generator sets leave the standard diesel governor in place. The diesel governor operates independently from the gas flow whereby the governor simply throttles back when gas is introduced. Ultimately leaving the original diesel governor in full control over load and speed.
Dual Fuel integrated speed control
For the majority of applications the existing diesel governor dynamics suffices however where speed or load instabilities or very rapid load changes are needed, the imbedded speed control algorithms can be enabled.
These algorithms use the same highly accurate and flexible speed control loops as found throughout the other modern range of Woodward controllers.
Direct diesel control
Where the imbedded governor of the dual fuel control is set to drive both the diesel and gas actuators, it drives both actuators in calculated ratio. This results in optimal engine performance and emissions during transients. It is particular suitable for dynamic load applications such as found at drill rig applications.
Direct diesel control can be used for both SPI and MPI systems whereby the engine speed is controlled by means of an electronic actuator or ADEM style CAT engines enabled with Direct Fuel Control.
LCI offers the possibility of tuning the engine with a Kistler piezoelectric cylinder pressure sensor. Typically this is performed at the development stage of the first engine. Once the diesel gas conversion is completed there is no requirement for the sensor anymore and the sensor will be removed.
The Kistler sensor allows optimal tuning of the Gas/Diesel ratio, by measuring and visualizing the combustion pressure versus crank angle.
Click on the video below video for cylinder pressure differences between full diesel operation and diesel gas operation. The second part of the video shows the cylinder pressure and Dual Fuel/AKR-3 system response when heavy audible knock is initiated by additional propane injection. That part of the video is played in slow motion as the system response is very fast. It reduces the overall gas flow, but only the amount which is required, to eliminate the knock. The engine remains in diesel gas mode. There is no need to stop the gas flow entirely.