Question 3: A Diesel Particulate Filter (DPF) is an aftertreatment device used to reduce Particulate emissions from the vehicle tailpipe. The DPF collects the particulate matter and needs to be cleaned periodically. This cleaning process is called a 'regeneration'. a) Answer the following questions: 1) Describe how a typical engine control system decides when to regenerate a DPF and how the regeneration is implemented using the fuel injection system. Include comments on some of the difficulties in working out when to initiate a DPF regeneration. 2) Fuel in oil and thermal runaway are two potential issues caused by DPF regeneration. Describe what these issues are and how they should be avoided or minimised. [12 marks] b) A Diesel truck is being developed with a Diesel Particulate Filter (DPF) and NOx aftertreatment. The DPF needs to be sized to allow a time between regeneration events of 15 hours at an engine load of 120 (kW). The engine has been developed with the NOx versus soot trade-off curve in Figure Q3-1. Engine out emissions from a typical heavy duty truck 0.1 0.08 0.06 Particulates (g/kWh) 0.04 0.02 0 0 1 2 5 6 7 3 4 NOx (g/kWh) Figure Q3-1: A NOx - Particulates engine out emissions The target tailpipe NOx emissions are 0.25 (g/kWh). Assuming the truck meets this target and has NOx aftertreatment with 93% conversion efficiency. What are the Particulate Emissions from the engine? (Use Figure Q3-1) The backpressure characteristics of the DPF are shown in Figure Q3-2. Calculate the minimum size of the filter assuming the filter is regenerated when the backpressure at full load exceeds 0.12 (bar). 50 45 40 35 30 Back Pressure [kPa] 25 20 15 10 5 0 0 2 3 5 Soot Loading (g/litre) Figure Q3-2: Backpressure versus soot loading at full load [8 marks] Question 3: A Diesel Particulate Filter (DPF) is an aftertreatment device used to reduce Particulate emissions from the vehicle tailpipe. The DPF collects the particulate matter and needs to be cleaned periodically. This cleaning process is called a 'regeneration'. a) Answer the following questions: 1) Describe how a typical engine control system decides when to regenerate a DPF and how the regeneration is implemented using the fuel injection system. Include comments on some of the difficulties in working out when to initiate a DPF regeneration. 2) Fuel in oil and thermal runaway are two potential issues caused by DPF regeneration. Describe what these issues are and how they should be avoided or minimised. [12 marks] b) A Diesel truck is being developed with a Diesel Particulate Filter (DPF) and NOx aftertreatment. The DPF needs to be sized to allow a time between regeneration events of 15 hours at an engine load of 120 (kW). The engine has been developed with the NOx versus soot trade-off curve in Figure Q3-1. Engine out emissions from a typical heavy duty truck 0.1 0.08 0.06 Particulates (g/kWh) 0.04 0.02 0 0 1 2 5 6 7 3 4 NOx (g/kWh) Figure Q3-1: A NOx - Particulates engine out emissions The target tailpipe NOx emissions are 0.25 (g/kWh). Assuming the truck meets this target and has NOx aftertreatment with 93% conversion efficiency. What are the Particulate Emissions from the engine? (Use Figure Q3-1) The backpressure characteristics of the DPF are shown in Figure Q3-2. Calculate the minimum size of the filter assuming the filter is regenerated when the backpressure at full load exceeds 0.12 (bar). 50 45 40 35 30 Back Pressure [kPa] 25 20 15 10 5 0 0 2 3 5 Soot Loading (g/litre) Figure Q3-2: Backpressure versus soot loading at full load [8 marks]