Perkins' power alliance
By Steve Skinner03 November 2008
Perkins is confident that its Stage IIIB compliant engines will offer a +3% improvement in fuel economy and a +10% increase in power output over current Stage IIIA variants, although initial purchase costs of Stage IIIB compliant units could rise by over +30%.
“Stage IIIB compliant engines will represent a step-change for the industry,” said Oliver Lythgoe, Stage IIIB marketing manager at Perkins. “The implementation of these engines requires an entirely different kind of engineering and totally new ways of working with OEMs to integrate the engine.”
“In order to meet Stage IIIB legislation and attain certification, engines will have to pass scrutiny in the field, regardless of ambient or operating temperature or even altitude,” said Julia Boorman, senior legislation engineer. “Stage IIIB also means that we’ll have to measure oil mist from the crankcase, which means the crankcase will likely need to be sealed - a fundamental change in engine design.”
Further changes in design include heavier engines as tolerances are increased, the universal use of turbochargers, and the introduction of sizeable diesel particulate filters (DPF) for post burn treatment of exhaust gases.
“The engines themselves are the most compact we’ve ever designed, but with the necessary filter systems the physical characteristics of the whole package represents a considerable increase,” said Allister Denis, product marketing manager. “In fitting the new engines, the collaboration between us and the OEMs is essential as end products will need to be modelled at the same time as the engines in order to meet the packaging needs of the Stage IIIB compliant units.”
In order to meet legislation, engine manufacturers are looking at two primary systems to reduce Nitrogen Oxide (NOx). One centres on reducing NOx through cooling the ignition process via exhaust gas recirculation (EGR), while the second - selective catalytic reduction (SCR) - is based on injecting urea into the exhaust stream so that a catalyst filters NOx as an after treatment.
“We looked at both systems and believe that EGR offers our customers the most effective and fuel efficient solution,” said Ben Reed, Stage IIIB product engineering manager.
Further to NOx reductions, and in order to reduce particulate emissions in keeping with legislation, all manufacturers are developing after-burn filtration systems. “To achieve a -95% reduction in particulate matter, we have developed a ceramic diesel particulate filter (DPF) made from cordierite,” said Mr Reed. “In conjunction with this initial filter, we also have a through-flow diesel oxidation catalyst to reduce carbon monoxide and hydrocarbons.”
“One of the issues with filtration is that filters block and thus require regeneration,” said Mr Reed. “This can be achieved either through low or high temperature regeneration. Low temperature regeneration uses a catalyst to generate nitrogen dioxide that oxidises carbon at temperatures above 2500C, while high temperature regeneration uses a fuel injected 6500C blast from a turbo to burn-off the filter contents.
“For our engines over 130 kW, high temperature regeneration is our preferred method,” said Mr Reed, “while for our engines below 130 kW, we have designed the DPF to last for life.”
“We currently have 400 engineers working on the Stage IIIB project and we estimate that implementation will cost twice that which we spent implementing Stage IIIA,” said Maarten Verkiel, NPI programme manager.
“Fundamentally, the biggest single feature of Stage IIIB implementation is the collaboration that is necessary between engine manufacturers and OEMs,” said Allister Dennis. “We are already a long way down the road with OEMs, and the closer integration of our teams relating to finished products is a very positive and exciting aspect of the Stage IIIB implementation.”