LNG Blue Corridors
Demonstration of heavy duty vehicles running with liquefied methane

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Hardstaff Mercedes Benz Actros

Hardstaff Mercedes Benz Actros

The Hardstaff technology, originally conceived in 1999, is an electronic system that reduces the amount of diesel injected into a cylinder of a diesel engine, equally replacing the fuel with natural gas without affecting engine power and characteristics of the original diesel engine.  The technology has been developed to utilise natural gas (compressed-CNG or liquefied-LNG) and bio-methane (LBM/LBG) as the primary fuel source.

Technical Background

The Hardstaff dual fuel system intercepts the diesel injector signals and emulates the diesel injector to satisfy the OEM ECU’s expected injector return signal. This allows complete control of the quantity of fuel injected and the timing of each injection. For each injector signal received the desired mass of diesel to be injected is calculated. A complex model determines the maximum available diesel reduction. A reduced diesel injection signal is sent to the injector, and a gas injector signal is sent to provide an equivalent energy content of the diesel removed. Clearly gas injection must commence prior to diesel injection, as the gas is injected during the induction stroke. Hence the dual fuel operation is delayed for the next available cylinder cycle.

The gas injection system functions with a sequential operation and has been developed in conjunction with UK universities to provide fully optimised strategies and mixing fields, ensuring accurate delivery of natural gas. The system comprises of two gas injectors per cylinder; this enables sufficient mass and optimises the gas mixing process.  Since the calculations are on a mass basis accurate gas injection is achieved with automatic compensation for gas temperature and pressure.

Operation

The technology has many built in safety features to ensure engine operation is not affected. The unit operates as a slave to the OEM ECU. If any fault occurs (e.g. gas injector failure) the system will hibernate and revert to 100% diesel operation. Similarly if a diesel injector fault occurs the technology will hibernate.

Part of the technology solution developed is a bespoke exhaust after-treatment reducing both Non-Methane Hydrocarbons and Methane below current European emission limits. The after-treatment systems are designed to work in conjunction with Selective Catalytic Reduction systems at OBD1 and OBD2 levels and offer significant enhancement to current systems.

In order to accommodate the addition of methane catalysts in the exhaust system the Ad Blue injector location has to be re-engineered. The methane catalysts must be installed upstream of the SCR system, hence the injector is positioned after the methane catalysts. This repositioning has no effect on performance of the SCR system, emissions or noise. In dual fuel mode the Ad Blue injection benefits from the NO to NO2 conversion resulting from the addition of the methane catalyst.