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Diesel Engine Operation
The diesel engine process begins with air being taken into the engine's cylinders, where it is compressed by a piston to a much higher degree than in a petrol engine. This high "compression ratio" makes a diesel engine more efficient than a petrol engine. Near the point of maximum compression, diesel fuel is injected into the cylinder at high pressure. This high pressure, when combined with the temperature of the compressed air, makes the diesel fuel ignite spontaneously and burn rapidly. This increases the pressure and temperature in the cylinder, driving the piston back down the cylinder with great force. This energy release generates the power of the engine, while the combustion process generates emissions.
What changes?
The diesel engine itself is virtually unchanged, except for the addition of the gas injection system and the ECU, fitted externally to the engine. The Dual-Fuel™ in-cylinder temperatures and pressures are within those of pure diesel operations, so the converted engine operates within the designed limits of the original engine.
Engine System Hardware
The Dual-Fuel™ components will not affect the base engine's robustness and durability, enabling a quick and economic return to pure diesel at the end of ownership, maintaining residual value.
Dual-Fuel™ Electronic Control Unit (ECU) |
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Turbocharger Air Bypass (TAB) |
Gas Injection System |
- Controls/Interfaces with engine OEM’s ECU
- The Hawk® ECU - a new generation in Dual-Fuel™ control
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- Fast and accurate
control of air-fuel ratio
- High performance actuators
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- Electronically controlled
gas injectors installed in
modified air inlet manifold
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Dual-Fuel™ Control System
The new generation Dual-Fuel™ ECU, the Hawk® was developed in 2007 and is now being applied to both Genesis and the C-15 interfaced systems. The Hawk® is a powerful and robust controller, with ECU hardware supplied by Mototron Inc. with industry-standard software engineering by Ricardo. The Hawk® meets or exceeds OEM standards for robustness and operation, providing the ideal platform for heavy-duty stand-alone retro-fit systems or OEM interfaced systems. The development of the Hawk® is described in the Technical paper “Development Of The Hawk® Advanced Dual-Fuel™ Engine Management System to Enable the Use of Natural Gas in Today’s Heavy-Duty Vehicles” from the IANGV 2008 conference in Rio De Janeiro.
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Natural Gas Injection
Clean Air Dual-Fuel™ injectors are controlled by pulse-width modulated signals from the ECU. The signals are based on manifold pressure, charge air temperature, gas pressure, gas temperature, and fuel mapping, providing the best combination of emissions and efficiency.
All Dual-Fuel™ engines will run with either Compressed Natural Gas or Liquefied Natural Gas.
Super-cooled LNG requires vacuum-insulated low-pressure fuel tanks and requires less on-board space than compressed CNG gas tanks.
CNG tanks are three times larger than LNG tanks for the same basic fuel capacity.
Either fuel delivers the same engine performance.
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CNG and LNG
As part of the development of the Dual-Fuel™ technology, Clean Air Power has developed vehicle systems for the containment and delivery of both CNG and LNG. Building on the existing expertise, valuable experience has been gained by working with manufacturers to install the systems onto vehicles around the world. They are integrated from hardware supplied by specialist component suppliers and include LNG tanks, CNG tanks, premium industry-standard fitting and fixtures. The ability to use both forms of natural gas is essential for commercial success in an ever-growing and changing market.
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Addressing key industry issues
The quality and composition of natural gas is an issue for the transport industry. The presence of heavier gases, such as ethane and propane in the mix, can lead to combustion knock in the engine. If left unchecked, this phenomenon can lead to engine failure. Presently, adequate gas composition cannot be assured as there are no national standards regulating gas quality. However, Clean Air Power has developed a countermeasure to protect the engine from poor quality gas.
The system uses an engine-mounted knock-sensor that is integrated into the electronic control system. If a combustion knock is detected, the system will automatically change the operating mode of the combustion, immediately stopping the knock, and protecting the engine.
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