A gas engine generator or GEG, also known as a genset or gas generator set, is a machine equipment that converts fuel into electrical energy using an internal combustion engine coupled with an electric generator.
Main Components of Gas Engine Generator
The specific components can vary depending on the type and size of the generator, but here are the main components commonly found in gas engine generators.
- Engine: Primary component responsible for converting the internal heat energy into mechanical energy.
- Turbocharger: From the picture above, it is a turbocharger with one radial turbine stage and one radial flow compressor stage. The function of the turbocharger rotor by convert the exhaust gases into energy. Simultaneously, it will draw the fresh air and compress it into compressed air.
- Alternator or Generator: Secondary component responsible for converting the mechanical energy to electrical energy.
- Fuel System: The purpose of the fuel system is to deliver the fuel and mix the fuel with air before combustion.
- Cooling System: A cooling system is necessary to maintain the engine’s temperature within a safe range. (e.g. intercooler)
- Lube Oil or lubricating system: It serves several essential purposes in machinery. (e.g. friction reduction, wear protection, heat dissipation, Corrosion prevention, sealing, etc.)
- Air Intake System: The intake air is regulated by the throttle which controls the amount of air entering to engine. The throttle control is essential for managing engine power.
- Exhaust System: The exhaust system is responsible for guiding the exhaust gaseous after combustion out of the engine safely.
- Governor: The governor is a control system that regulates the speed of the engines. It adjusts the fuel supply to maintain a constant speed under varying load conditions, ensuring a stable and reliable power output. Governor is commonly used in engines to prevent overspeeding scenarios.
- Bypass valve: Also known as a wastegate regulator, is a valve that controls the flow of gases in a system. A bypass valve is often associated with turbochargers. It controls the amount of exhaust gases that bypass the turbine, regulating the speed and pressure of the turbocharger.
Type and application of Turbocharger
The different types of turbochargers impact power generation in various ways. Each type has its unique characteristics and advantages. Here’s a brief overview of each type of turbocharger.
| Single Turbo | – Used in a wide range of applications; – Efficient for providing a power boost, at high speed engine; – Exhibit some turbo lag at the lower speed. |
| Twin Turbo | – Uses to increase power output in larger engines; – Improve responsiveness across a boarder range of engine speeds. |
| Sequential | – Aim to address turbo lag issues; – Commonly used in diesel engines; – Uses two turbos, a smaller turbo provides quick response at low-speed and a larger one takes over at higher speed. |
| Twin-scroll | – Help optimize exhaust gas flow by dividing the inlet passages; – Enhance power generation, especially at lower engine engine speed |
Design Codes and International Standards
NFPA 37: Standard for installation and use of stationary combustion engines and gas turbines e.g. gas trains for engines shall contain at least the following safety components: an equipment isolation valve, a regulator, and two automatic safety shutoff valves. [NFPA 37 – 5.2]
Hazard of Gas Engine Generator
- Fire and Explosion: Any leakage or malfunction in the fuel system and loss of containment can lead to fire or explosion hazards.
- Equipment damages: One of the most significant consequences is the risk of over-boosting and over-speeding if the bypass valve of the turbocharger fails in the closed position.
- Loss of production: Too much or air or fuel supply to cylinder or inadvertently close of fuel solenoid valve to cylinder will result in wrong fuel-air ratio and misfiring. This will lead to equipment stop (knocking).
- Exhaust Emission: GEG produces exhaust gases that can be harmful if inhaled. Exhaut gas with the dangerous constitutes NOx, SO2, CO, HC2, and soot are a particularly dangerous gas produced during combustion which can result in Noxious. (Negative effect on the environment)
- Electrical Hazards: There is a risk of electrical shock or electrocution if electrical resistance insulation loses integrity.
- Hot surfaces: The engine and accessories can become very hot during operation.
- Mechanical Hazards: Moving parts in the generator can pose a risk of injury if not properly guarded.
- High Pressure Hazards: GEG during start-up needs to use the compressed air since it is required to overcoming the initial inertia, assisting in crankshaft rotation, aiding compression stroke, and ignition facilitation. Hence, operator expose to the starting air system will have a risk of high-pressure hazards.
- Generator damage: If the GEG connected to the generator and connected to the grid (parallel mode), malfunction of GEG will result to unable to drive the crank shaft and cause of reverse power to generator.
General problem Gas Engine Generator (GEG) and possible causes
Engine does not crank.
- Failure of starter solenoid;
- DC battery dead; and
- Water filled cylinder
Engine does not start.
- Fuel starvation;
- Air leak in to fuel system; and
- Fouled spark plug.
Engine hunts.
- Air leaks into fuel system;
- Loss of fuel supply; and
- Low octane fuel.
Engine misfires or backfires.
- Low octane fuel;
- Less pressure of fuel supply;
- Less of air intake i.e. dirty air intake screen; and
- Exhaust gaseous restriction.
Engine overheats
- Loss of coolant flow;
- Coolant pump belt loose/broken; and
- Faulty of pump impeller
Compressor surging
- Turbine wheel heavily fouled;
- Foreign material in turbine or in compressor;
- Low air inlet temperature (higher air density);
- Exhaust gas backpressure after turbine too high.
Compressed air pressure too low
- Silencer or air filter fouled;
- Compressor fouled;
- Turbine wheel heavily fouled;
- Rotor rubbing;
- Foreign material in turbine or in compressor;
- High air inlet temperature (low gas density);
- Exhaust gas backpressure after turbine too high.
Compressed air pressure too high
- Low air inlet temperature (high gas density)
Turbocharger speed too low
- Silencer or air filter fouled;
- Compressor fouled;
- Turbine wheel heavily fouled;
- Defective bearing, imbalance of the rotor; and
- High air inlet temperature (low gas density)
Turbocharger speed too high (over-boosting)
- More fueling;
- Low air inlet temperature (high gas density, high momentum)
PROcess Safety TASK 