ENGINES OF THE FUTURE
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IN The diesel engine of the future is going to benefit from a delayed or retarded injection system, argued Peter Wright, development supervisor at Perkins Engines.
Current engines inject fuel into the cyclinder head at about 24° before top dead centre and Perkins wants to push this back to 14°.
The company reckons that retarding the timing by 10° will give engines much better durability, reliability and cost figures.
Looking at mid-range truck engines, Wright said that Perkins' retarded combustion engines have given 4-9% more power without shortening engine Life. "The users will see higher truck loads and shorter journey times," he predicted. Torque outputs have been increased on the new retarded engines by 9-13% "with more power lower down the engine speed range."
Perkins has put a number of the test engines in UK truck fleets and they have achieved fuel economy benefits of 8% over existing engines in those fleets. "In a fleet of 140 vehicles with a fuel bill of 2600,000 this would mean an annual saving of £45,000."
On engine durability Wright said, "Peak cylinder pressures have been reduced by 7% against previous products with the attendant benefits on engine stresses."
Brian Sexton, an applications engineer with Delco Remy, looked at diesel engines with spark ignition assistance in another engine technology paper at the conference. Increasing compression pressures in the cylinder has been the traditional technique of improving a diesel engine's cold-starting performance, said Sexton, but higher pressures require stronger and heavier engine blocks. Spark ignition techniques can help keep engine weights down.
Glow plugs are a severe drain on a truck's electrical system and their usual minimum starting limit is —35°C. Spark ignition concept engines have gone down to —45°C said Sexton.