21–22 Latest Review And Best Future Of | Diesel Gas Engines

Diesel Gas Engines

Introduction;- In this post on | diesel gas engines we will discuss about the Liquefied Natural Gas,Principles of Gas Engines and Engine Control Gas System. The post on diesel gas engines will provide the relevant information about the topics related to gas engines and generators used on board ships and Industries.

Advantages of Diesel Gas Engines

Marine and commercial power generation industry prefers the Gas engines for the following facts.

1. To meet the compliance with the stringent emission regulation limits of SOX and NOX.
2. Smoke pollution
3. Particulates.

Transportation Liquefied Natural Gas (LNG) is at -1630 to -1650 C at atmospheric pressure. This fuel has become popular as an energy source globally.

What is boil-off Gas?

Due to the imperfect insulation of the tanks, and the effect of heat causes the LNG to evaporate inside the tank producing the boil-off gas. Boil-off gas mixes up with the gas and increases the pressure inside the tank. To handle the pressure an alternative source is to release the pressure in to the LNG tank. BOG fuel is subject to reliquefaction and supplied to engines as fuel.

The LNG production is by following processes.

Natural Boil-off gas

In this process Boil-off gas is taken from the tank above the liquid gas. Natural boil-off gas contains Nitrogen and high methane contents and will have high resistance to knocking? The lower calorific value will be around 35MJ/nm3.

Forced Boil-off gas

In this process LNG is evaporated separately after extracting from the bottom of the tank. This gas will contain hydrocarbons in the liquid gas. The knocking properties will vary from case to case and engine to engine. This gas will have methane no. of 80 and LCV around 39 MJ/mn3. Forced boil-off gas is more popular as fuel than the Natural boil-of gas for the general shipping.

The most suitable gas as engine fuel is Natural boil-off gas since it has the better knocking stability due to the high methane contents contained in it. But the natural boil off gas is not available in plenty.

Hence the engine design preference is for the forced boil-off gas.

Principles of Diesel Gas Engines

Operating principles of the Gas Engines is of following two types.

• Otto gas Engines
• Spark Ignition Gas Engines
• Diesel Ignition Gas Engines.

Otto Cycle gas engines

Otto Cycle gas engines are with low NOX emissions with high efficiency. These engines meet the latest IMO compliance. These engines work differently with respect to efficiency at low load operations.

Diesel Cycle gas engines

On completion of the diesel pilot fuel ignition, high pressure gas injection in to the cylinders takes place. This type of design is compatible for the dual fuel operation also and can run satisfactorily 100 % on Diesel/HFO (Heavy Fuel Oil). High pressure gas at 300 bar is the requirement with the post exhaust treatment to comply with the emission regulations.

Advantages of spark ignition Gas engines.

• Use of low pressure gas supply at 4to 5 bar.
• Efficient at higher load.
• Low emissions and meats the regulations.
• Sensitive to Methane Number ( Gas quality)

Advantages of Diesel Gas Engines with high pressure direct gas injection.

• Can operate on multi fuels ( HFO, MDO, LNG)
• Maintain Diesel Engine performance with high pressure gas injection at 300 to 350 bars.
• These engines are not sensitive to Gas quality.
• Simple evaporation with pumping of LNG to 350 bars.
• Fuel mixing flexibility.

Conversion to existing engine retrofitting is simple

Gas Engine Operation

Engine Control gas consists of following controls.

Speed & Power control:-

Engine control system adjusts the amount of gas injection by regulating the duration of gas admission valve for speed and power control.

Air Fuel Ratio Control

Opening of Waste-gate ratio will control the Air fuel ratio. The waste-gate controls the amount of bypassed exhaust gas to Turbocharger. The charge air pressure at each load point will decide the operation point.

Ignition system Control

Spark plug in the pre-combustion chamber is the ignition source of combustion. Engine control system controls tthe precise ignition timing and energy of ignition system

Gas Pressure and Valve control

Engine control system manages the control of gas pressure regulation, sequential gas valve operation and the operation of gas admission valve.

Cylinder Balancing and Knocking Control

In Gas engine control system is integrated with knock detection and monitoring of cylinder pressure. Engine control system transmits the pressure and knocking signals to the pane.

Introduction;- The Diesel Gas Engines power plants consists of following systems.

• Engine Control system
• Engine generator control panel
• Plant control and monitoring system

All the above systems are interfaced through Ethernet.

System Overview

The engine control system consists of following panels and modules.

• Main Control panel
• Injection control module
• Spark ignition control module
• Cylinder monitoring Panel
• Local operating and Power supply panel.

Main control panel is mounted on the Engine and consists of following controls.

• Main control of Gas
• Engine safety control
• Engine shutdown control
• Governor control
• Gas regulating unit control
• Cooling water valves control
• Air fuel ratio control Waste –gate
• Interface with LOSP (local operating & Power supply panel) and Engine generator control panel.

ICM (Injection control module) mounted on the engine and connected with the Gas admission valves and exhaust sensors temperature on each cylinder unit. The ICM performs the following functions.

• Drives the gas admission valve
• Measures the exhaust gas temperature
• Transmits the data to main control panel via CAN communication.

CMP monitors the combustion characteristics and intensity of knock at each cylinder & communicates the information with main control panel for monitoring and control for Diesel Gas Engines

CMP’s location is on Engine. CMP performs the following functions.

• Cylinder pressure signal measurement
• Process and measurement of knock signal
• Combustion characteristic calculation
• Calculation of knock characteristic
• Transmission of data to main control panel

Local Operating and Power supply panel

Operators use this panel mounted in self standing cabinet for the local operation and monitoring the engine.

LOSP performs the following functions on Diesel Gas Engines

• Local operation for starting, stopping and resting of alarms on engine.
• Display of Engine measurement and status.
• Display of alarms
• Display of events
• Test of actuators and valves in engine stop mode.
• Power distribution control to MCP, ICM, SIC ,CMP

Interface with main control panel

Engine Generator Control panel

Engine generator control panel for Diesel Gas Engines is installed in control room as self standing cabinet. Main functions of EGCP are as under.

• Remote operation for starting, stopping, and resting of alarms.
• Voltage control with the help of AVR.
• Opens and closes the generator circuit breakers.
• Emergency stopping of the engine. Safety control and protection of engine.
• Synchronization on auto and manual mode.
• Selection of power control mode.
• Setting of demand power.
• Engine and Generator measurement display.
• Display of electrical parameters.
• Displaying of alarm and events.
• Interface with plant control monitoring system

Monitoring and Plant control system for Diesel Gas Engines

PCMS is installed in control room. PCMS consists of Station PLC and operation station. PCMS controls and monitors the Engine and generator set.

Functions of PCMS are as under.

• Remote operation
• Auto or manual operation
• Emergency stop of engine
• Auto synchronisation
• Section of power control mode.
• Setting of power demand
• Engine and generator status display
• Display of electrical parameters
• Auxiliary equipment and switchgear display
• Tank level display
• Display of Alarms
• Trending

Conclusion;- I hope the post on Diesel Gas Engines has provided the usefu information to the reares.

Good Luck!!!