Jacobs Vehicle Systems, a leading manufacturer of heavy-duty diesel engine retarding systems and valve actuation systems, will introduce its new Cylinder Deactivation (CDA) technology to the European market at IAA Commercial Vehicles 2018 (Hannover, Germany, 20-27 September).
CDA uses the proven componentry of Jacobs’ High Power Density (HPD) engine brake, but in a new application and for a new purpose. Whereas HPD’s advantage is that it equals or exceeds the braking capabilities of a driveline retarder at a fraction of the cost, CDA’s benefits are reduced tailpipe emissions plus better fuel economy. CDA and HPD technologies are modular and can be integrated into an engine individually or together.
For CDA, cylinder deactivation mechanisms originally designed for HPD applications are used in the valvetrain to disable the opening of the intake and exhaust valves.
The hydraulically-activated mechanism is integrated in a collapsing valve bridge system for overhead camshaft engines or with a collapsing pushrod system for cam-in-block engines. When this is combined with disabled injection in selected cylinders, the deactivated cylinders act as a gas spring and return the compressed energy of the air back to the crank.
CDA reduces emissions by achieving higher exhaust temperatures in the operating cylinders. This makes it possible to maintain after-treatment temperatures when the engine is in low load operation.
It also enables faster warm-up of the after-treatment system after engine start-up and minimizes cooling during coasting. Temperature increases of 100-200 °C are achieved in low load conditions and 250 °C is consistently maintained at loads of approximately 15 kW or more.
CDA simultaneously enables large engines to have the fuel economy of smaller engines because it:
increases exhaust temperatures for optimal SCR (Selective Catalytic Reduction) operation;
reduces pumping losses in part-load conditions; and
can reduce or eliminate use of the intake throttle.
One, two or three cylinders can be deactivated as needed. At the lowest engine loads and with three of six cylinders deactivated, fuel consumption improves by up to 20%.
During vehicle coasting conditions, CDA can be applied to some or all cylinders to further reduced the air mass flow going through the aftertreatment system to both reduce the cooling, and also reduce engine pumping losses, allowing the vehicle to coast further with less fuel.
Jacobs’ Cylinder Deactivation mechanism has proven its effectiveness and reliability in evaluation programs on seven different engine platforms with manufacturers in North America, Europe, China, Japan and Korea. During these trials, CDA hardware has been subjected to more than 4,300 hours of durability testing, more than 1.2 billion component cycles, and 500 million cycles of fatigue and overload testing. These tests have shown that CDA is production-ready, the company said.
Posted on 10 September 2018 in Diesel, Engines, Fuel Efficiency, Heavy-duty, Vehicle Systems | Permalink | Comments (1)
I would like to see an engine brake which manages to provide more braking horsepower than the rated max output of the engine. It should be possible. In braking mode, the exhaust valve is opened near TDC on the compression stroke by activation of an extra cam lobe. Given that the intake valves on these engines are usually vacuum-operated and not cam-driven, it would be a simple matter to operate the compression brake as a 2-cycle air compressor. Combined with use of the turbocharger to modulate the air flow through the system, it should be possible to dissipate more power than the engine is capable of producing at the same RPM.
If the compression brake can be activated on a per-cylinder basis it would allow for fairly fine-grained control of braking force. This goes double if it could be triggered on a 4-cycle vs. 2-cycle mode; a 6-cylinder engine would have 12 steps of engine braking force, plus whatever control is exercised over boost pressure.
Posted by: Engineer-Poet | 10 September 2018 at 06:05 AM
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