ComAp's simple Bi-Fuel conversion modifies your original diesel engine so that it uses natural gas as the main fuel - substantially reducing operating costs. It works by introducing gas to the engine via various technologies and then electronically controlling flow dependent on engine speed and output.
Bi-Fuel conversion requires virtually no engine modification and bring double benefits in every application:
• Affordable diesel engines combines with inexpensive natural gas
• Economic solution for slow-speed, middle-speed and high-speed engines
• Flexible use of fuel
• Guaranteed power output
• Efficient and safe operation with lower emissions
• Longer engine life and reduced maintenance costs makes it the perfect investment
WHAT DOES BI-FUEL OPERATION MEAN?
Bi-Fuel operation means the engine uses two fuels (gas and diesel oil) at the same time. Natural gas is intended as the main fuel and diesel oil is used for the ignition of the gas/air mixture inside the cylinder (a portion of diesel oil is injected at the end of the compression stroke, thereby maintaining the original diesel operation principle).
WHAT TECHNOLOGIES ARE EMPLOYED IN THE BI-FUEL CONVERSION?
ComAp provides two conversion technologies - one for slow/middle-speed engines (up to 1000rpm) and the second for high-speed engines (1200 to 1800rpm). Therefore the choice of the appropriate ComAp solution is determined by the engine speed and consequent suction/exhaust valve overlap (i.e. opening of suction and exhaust valves at the same time).
Slow/middle-speed engines normally feature a large valve overlap when the pure air is flushing (cleaning) and cooling the cylinder. After dual-fuel conversion, it is necessary to continue cylinder flushing/ cooling by pure air, i.e. gas flow into the cylinder during the valve overlap must be interrupted to avoid the presence of gas in the hot exhaust manifold (this would cause a potentially dangerous situation and result in substantial fuel losses).
Therefore, typically for slow and middle-speed engines, each cylinder is equipped with the patented electromagnetic gas valve with variable gas injection timing controlled by a ComAp electronic control system INCON.
In contrast, high-speed engines have only a small valve overlap, so it is possible to install just a centre mixer before the turbocharger for the continuous flow of the gas/air mixture. Gas injection is controlled by a throttle operated by the ComAp electronic control system InteliDrive BF according to the required engine output and speed.
IS IT NECESSARY TO OPERATE A CONVERTED GEN-SET ON NATURAL GAS ONLY?
No, transitions between the two modes (from dual-fuel to diesel and vice versa) can be achieved while the engine is running (i.e. without interruption of the load supply) and is a very smooth process. Note the engine will always start on diesel and the operation mode is switched to dual-fuel upon a predefined output level. In case of gas shortage, the transition is immediate and seamless at the actual engine load, gas valves are shut off automatically and the engine continues on pure diesel operation. Once the gas supply has returned the engine is switched back to dual-fuel operation.
WHAT IS A DE-RATING FACTOR (OUTPUT REDUCTION) FOR A CONVERTED GEN-SET?
After the conversion, the engine nominal output is not de-rated and all engine parameters (e.g. exhaust temperature, engine temperature etc.) and behavior (e.g. response to a load steps) remains within the limits stated by the engine manufacturer for the original diesel engine (provided these parameters were within limits before the conversion). The de-rating factor according to the ambient conditions remains the same.
HOW DOES THE CONVERSION AFFECT MAINTENANCE COSTS?
Maintenance costs after conversion will not be increased at all. Substantial parts of the engine remain unchanged, new mechanical parts are of heavy duty design (e.g. service interval for the electromagnetic gas valves is 6000 running hours), and the electronic control systems are fully automatic. Moreover, the gas operation means less carbonisation of combustion chambers and turbochargers, so that the interval for de-carbonisation and overhauling of the engine is prolonged.
WHAT WARRANTY DOES COMAP PROVIDE FOR THE CONVERSION?
Standard warranty is 12 months from the date of start up, 4000 running hours, whichever expires earlier. The warranty covers equipment related to the conversion.
CAN BIOGAS BE USED FOR BI-FUEL ENGINE OPERATION?
In general, yes it can. We need to know biogas composition and calorific value to evaluate if the particular biogas type is really suitable. Calorific value may be an issue as biogas is derived from different sources and there is low calorific value in many cases. You can imagine we have to inject sufficient volume of gas into the cylinder to substitute diesel oil (or, better to say, substitute energy delivered by diesel oil). If the quality or quantity of the BioGas changes, the system dynamically adjusts the system to keep the power output consistent.
