Development of a Modern Diesel Engine with Ultra-Low Bore Distortion to Reduce Friction, Blowby, Oil Consumption and DPF Ash Loading 2020-28-0344
The stringent emission regulations coupled with tighter CO2 targets demand extreme optimization of the diesel engines. In this context, it is important to minimize the cylinder bore distortions in cold and hot conditions. The cold bore distortion in primarily due to the assembly forces applied by the cylinder head bolts whereas the hot distortion is a resultant of the metal temperature and structural rigidity. The present work describes the extreme optimization techniques used to reduce the bore distortion of a modern high power-density (60 kW / lit) diesel engine, Moreover, the benefits of reducing the bore distortion is quantified in terms of cylinder system friction, blowby rate, oil consumption and ash loading rate of the diesel particulate filter (DPF).
An optimised torque plate honing was used to reduce the bore distortion in cold condition. However, an extreme optimization of the cylinder bore structure and water jacket design were needed to control the hot bore distortion. The piston and ring pack of the low bore distortion (LBR) engine could be optimised to have a reduced tangential force. The cumulative tangential force of all the piston rings could be reduced from 34 N to 24 N which could result in a significant reduction in the cylinder system friction. Moreover, the engine level measurements with and without the torque plate honing confirm that a significant reduction in blowby rate (~20%) and oil consumption (~25%) could be achieved with the torque plate honing. The results were found to be consistent with the vehicle level results in which the oil consumption (g/km) was assessed in detail. Furthermore, the reduction in the oil consumption could benefit the ash loading behaviour of the DPF. With the LBR engine, the ash loading rate of the DPF is reduced significantly (~28%) which is extremely important to have higher regeneration interval.
Thus, the development approach to have low bore distortion has resulted in multiple benefits and hence it is found to be useful in developing diesel engines with compliance to future regulations.
Vikraman Vellandi, Prasad NAMANI, S. Suresh Bagavathy, Madhu Chalumuru