Smoke emissions produced by turbocharged diesel engines under heavy load conditions – such as when accelerating from low engine speeds and other similar transient manoeuvres – can be all but eliminated by a relatively simple and low cost electric supercharger says automotive CO2 reduction specialist, Controlled Power Technologies (CPT).
The reduction of particulate emissions is a major issue for the off-highway segment of the commercial vehicle industry, which faces tough new international regulations in 2012, when for the first time legislators will assess the emissions of engines under transient conditions. Until now the emission testing for such engines has been steady state.
“The particulate problem is caused by the turbocharger being sized for maximum power rather than transient response,” says Nick Pascoe chief executive officer CPT. “During a transient event, the fuel injection system tries to deliver the power demanded by injecting more fuel, but the turbocharger will be a few seconds behind, with the lack of air causing over rich combustion and lots of soot. A fast-acting electric supercharger helps with the root cause of the problem by supplying more air earlier in the event. It can also help minimise the need for expensive exhaust after-treatment.”
The benefits of having a near instantaneous air supply can be achieved by CPT’s electric compressor known as VTES or ‘variable torque enhancement system’.
The technology provides an attractive solution for the industry because of its low cost, low effort of application engineering and low commercial risk. This is particularly the case when compared with twin sequential turbocharged solutions, which are unable to match the faster mass flow rate rise and corresponding torque response delivered by VTES at low engine speeds.
“VTES is a compact system with fully integrated electronics that’s easy to install,” says Pascoe. “It dramatically increases the engine air charge density over the first few critical combustion cycles of a low speed transient operation, enabling real improvements in both torque and emissions performance.”
As well as reducing particulate emissions, VTES technology can also be applied for NOX control. As part of a low pressure exhaust gas recirculation system it can deliver sufficient EGR flow even with a low pressure difference across the engine and rapid purging of EGR in the ducts and intercooler during high load transients.
“Future emission controls will require increased use of exhaust gas recirculation even under higher engine load conditions,” says Morris. “Traditional high pressure EGR systems result in poor driveability, which is an issue that can also be addressed with VTES technology.”
CPT’s VTES supercharger benefits from almost a decade of research and continuous product development resulting in a robust and cost-effective system. For further information on emission control experts, CPT visit the website, www.cpowert.com .
