Session: 01-03 Advanced Engine Components and Future Propulsion Systems

Paper Number: 195120

195120 - Can Existing Tier 4 Hardware Meet Tier 5? Emission Compliance Study on a 56 kW Off-Road Diesel Engine 

Abstract: 

Proposed Tier 5 off-highway emission regulations for the 19–56 kW engine class present significant technical and economic challenges. Unlike larger engine platforms where selective catalytic reduction (SCR) has become the standard nitrogen oxide (NO_X) control strategy, engines in this power category are subject to stringent cost and packaging constraints that limit the adoption of complex aftertreatment systems. This paper investigates whether a production Tier-4 certified diesel engine can achieve compliance with proposed Tier-5 emission limits through calibration optimization and minor hardware changes alone, without fundamental hardware redesign and while using the same Tier-4 certified aftertreatment system.

The technical approach centered on a cooled exhaust gas recirculation (EGR) strategy to reduce NO_X formation in-cylinder, in conjunction with fuel injection timing optimization to manage the inherent NOx–PM (particulate matter) trade-off. The stock diesel oxidation catalyst (DOC) and diesel particulate filter (DPF) system was leveraged to address particulate matter requirements. Engine-out and tailpipe emissions were characterized over a design of experiments (DOE) sweep of EGR rate and start of injection (SOI) timing, and the resulting NO_X–soot curves were used to identify an optimal calibration. Compliance assessment was conducted over both the Ramped Modal Cycle (RMC) and the Non-Road Transient Cycle (NRTC), as required under Title 13 California Code of Regulations (CCR) Section 2423 for certification of variable-speed engines in this power category.

Over the RMC cycle, the engine-out NO_X and non-methane hydrocarbons (NMHC) emissions were measured to be 1.95 g/kWh and 1.19 g/kWh, respectively. Engine-out soot was measured to be 0.046 g/kWh using a micro-soot sensor (MSS). Based on average expected exhaust aftertreatment conversion efficiencies for a DOC + DPF system, the calculated tailpipe out emissions were 1.95 g/kWh, 0.071 g/kWh and 0.00058 g/kWh over the RMC cycle for NO_X, NMHC and PM, respectively. Similarly, over the NRTC cycle, the composite engine-out NO_X, NMHC and soot were measured to be 2.08 g/kWh, 1.175 g/kWh and 0.05 g/kWh respectively. The tailpipe out NO_X, NMHC and PM were calculated to be 2.08 g/kWh, 0.0612 g/kWh and 0.003 g/kWh respectively. When compared to the proposed Tier 5 final limits for the 19-56 kW class of 2.5 g/kWh for NO_X, 0.19 g/kWh for NMHC and 0.008 g/kWh for PM (model year 2036), results indicate that the system can be a viable pathway of meeting upcoming Tier 5 final emissions standards. Because the system uses only minor hardware changes and engine recalibration, it does not add cost or complexity, key aspects for this engine category.

 

Presenting Author: Shubham Patil Southwest Research Institute

Presenting Author Biography: Mr. Patil is a research engineer in the powertrain engineering division at Southwest Research Institute. He specializes in end-to-end powertrain development across conventional, hybrid, and alternative fuel platforms. His work spans powertrain system modeling, controls development, and engine calibration.

Authors:

Pruthvi Bachu Southwest Research Institute
Alexander Michlberger Southwest Research Institute
Shubham Patil Southwest Research Institute
Herbert Amal Garcia Southwest Research Institute
Edward Smith Southwest Research Institute