Ricardo and Doosan DL06 diesel with TVCS achieves Tier 4f emissions without need for DPF
9 October 2013
|Ricardo’sTwin Vortex Combustion System (TVCS) reduces soot by 45- 50% compared to a conventional approach. Source: Ricardo. Click to enlarge.|
The Doosan DL06 engine is a turbocharged and intercooled 5.9-liter, in-line 6-cylinder diesel engine used in both on-highway and off-highway applications. The new US Tier 4 Final (Tier 4f) version of the DL06 includes an ultra-low particulate combustion system featuring the Ricardo Twin Vortex Combustion System (TVCS) (earlier post); the engine achieves compliance with Tier 4 Final particulate emissions levels without requiring a DPF—thereby providing a cost-effective solution.
The engine features a 4-valve/cylinder head, with a central vertical injector location and high pressure common rail fuel injection system. Typical off-highway applications for the engine are excavators and wheeled loaders, made by Doosan and its subsidiaries such as US manufacturer, Bobcat.
First introduced in 2005, the most recent version of the DL06 is certified to Tier 4 interim exhaust emissions regulations, and is equipped with cooled EGR to reduce NOx emissions and a DPF to minimize particulate. With the substantially reduced NOx levels required for Tier 4 Final compliance, Doosan has, like many of its competitors, opted to include Selective Catalytic Reduction (SCR) as part of its aftertreatment technology package.
However, using advanced simulation tools including the WAVE engine performance simulation and VECTIS CFD package, Doosan and Ricardo engineers were able to develop the Tier 4 Final version of the new DL06 engine without the need for a Diesel Particulate Filter.
The ultra-low particulate combustion concept of the new DL06 engine is based on a combustion chamber employing the Ricardo TVCS concept to improve homogeneity of air-fuel mixing, adequate air-fuel ratio at all conditions by balancing the EGR rates and boosting system match, and high fuel injection pressures and appropriate nozzle specification for good atomization.
TVCS systems basically comprise an optimized injector nozzle and combustion chamber design; the use of a high pressure, 2000 bar common rail fuel injection system; a variable geometry turbocharger; and cooled EGR for NOx reduction.
Key elements are the shape of the piston bowl and its lip; the fuel spray cone; and the swirl generated in incoming inlet air. Essentially, Ricardo noted in its Q2 2010 Quarterly Review, the design creates two annular contra-rotating vortices in the piston bowl, one atop the other. The vortices vigorously rotate about their circumferential centerlines.
At their point of intersection the opposing rotations of these rings produce conditions leading to the highly efficient air/fuel mixing which is essential to the reduction of particulate generation during combustion. The geometry of the injected spray, in conjunction with the movement of the air charge, avoids fuel being deposited on the cylinder wall, something which chills the fuel and increases soot formation and fuel dilution of the oil, reducing its lubricating properties and life.
The outer portion of the piston bowl is concave and its design increases the vertical motion of the fuel spray as it approaches the upper section of the piston. The carefully profiled lip differs from the chamfered profile used in conventional designs and which would normally spoil the shape of the main section of the bowl, disrupting the air motion necessary for good fuel/air mixing and low emissions. The result is a thoroughly mixed cloud of fuel and air extending vertically upwards and avoiding both the cylinder walls and outer areas of the combustion chamber.—Ricardo Quarterly Review (Q2 2010)
In January, Doosan Infracore held an opening ceremony for its new Compact Engine Plant in Incheon, Korea, where Tier 4 final compliant versions of its new compact engine family—in 1.8, 2.4 and 3.4 liter capacity variants—will be manufactured. Amongst the customers of these engines featuring Ricardo’s TVCS technology is Bobcat, which has announced plans for Tier 4 solutions that include Doosan-built engines powering some of its equipment line-up for 2014.
Natti, K., Sinha, A., Hoerter, C., Andersson, P. et al., (2013) “Studies on the Impact of 300 MPa Injection Pressure on Engine Performance, Gaseous and Particulate Emissions,” SAE Int. J. Engines 6(1):336-351 doi: 10.4271/2013-01-0897
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