Experimental Valve Motion Measurement Study for Mid-Range Diesel Engine 2022-01-0629

The valve train is one of the most important part of engine , and its function is fresh charge inlet and exhaust exit according to order of engine based on intake and exhaust valve [1].The compression relief brake mechanism is one of the integrated brake technologies in Internal Combustion Engines (ICE) which not only reduces engine speed during downhill under overspeed condition by opening of one of the exhaust valves before the power stroke but also helpful to reduce brake pad wear by assisting in vehicle braking. The clearance between exhaust valve and piston during compression relief brake event is important aspect for overall valve train dynamic perspective. Valve motion study included this valve to piston clearance measurement in engine testing as mandate during product development phase. Looking at new products in future and to improve system level valve train dynamics in integrated brake design hardware, it is required to validate the design changes, a valve lift experimental test was performed to understand valve train dynamics during engine running condition. This valve motion measurement study has been performed for the first time for mid-range diesel engines in Cummins Technical Center India (CTCI).

The displacement sensors were used for valve lift measurement. Special instrumentation was done on the valve cover to integrate sensor setup. Also, modification was done in exhaust valve spring retainers to incorporate displacement sensors for data acquisition. Steady state measurement data was taken for 50 cycles at various engine operating conditions such as motoring and firing. Peak Cylinder Pressure (PCP) sensor was installed in one cylinder and valve displacement data was acquired in the angle domain. Piston Profile was measured offline with 5-degree resolution in static condition.

Upon test completion, all recorded valve displacement data was compared graphically with piston profile to evaluate valve to piston clearances for final validation. Also, there was no contact observed between valve and piston considering compression relief brake event for all Rotation Per Minute (RPM) data captured for firing and motoring conditions. Results are satisfactorily meeting the requirements. Post teardown of engine, all the valves and piston contact regions were found free from any kind of contact marks thereby validating the valve motion study.