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This paper describes a NOx aftertreatment system and control strategy for heavy-duty diesel engines to achieve US EPA 2010 emissions regulations. The NOx aftertreatment system comprises of a fuel reformer catalyst, a LNT catalyst, and a SCR catalyst. The only reductant required to operate this system is diesel fuel; hence, no urea infrastructure is required to support this approach. The fuel reformer is used to generate reformate which is a combination of hydrogen, carbon monoxide and unburned hydrocarbons. This reformate provides a more efficient feedstock to improve LNT NOx regeneration efficiency. Engine out NOx is reduced using a two-step process. First, NOx is stored in the LNT catalyst during lean operation. During rich operation, portions of the stored NOx are converted to nitrogen and ammonia. Next, the ammonia released from the LNT is captured by the downstream SCR catalyst. The stored ammonia is further used to reduce the NOx that slips past the LNT catalyst.

An advanced exhaust aftertreatment system is being developed using a fuel dosing system, mixing elements, fuel reformer, lean NOx trap (LNT), diesel particulate filter (DPF) and a selective catalytic reduction (SCR) catalyst arranged in series for both on- and off- highway diesel engines to meet the upcoming emissions regulations. This system utilizes a fuel reformer to generate hydrogen (H2) and carbon monoxide (CO) from injected diesel fuel. These reductants are used to regenerate and desulfate the LNT catalyst. NOx emissions are reduced using the combination of the LNT and SCR catalysts. During LNT regeneration, ammonia is intentionally released from the LNT and stored on the downstream SCR catalyst to further reduce NOx that passed through the LNT catalyst. This paper addresses LNT and SCR catalyst degradation as these were subjected to 150 desulfation events using a pre-production 2007 medium heavy-duty, on-highway diesel engine.

Engine braking is a supplemental retarding technology in addition to foundational friction brakes in commercial vehicles. This technology is in use in Europe & Americas for several decades now. In engine braking, the engine acts as a compressor, thus producing the required braking power. The braking power is generated by either reducing the volumetric efficiency or increasing the pressure difference across the cylinder. This is usually achieved by means of exhaust valve lift modulation. There are dominantly two types of engine brakes viz. bleeder brake and compression release brake. The present work uses GT-Power® model to study the braking performance of a 4-cylinder, medium duty diesel engine at different engine RPMs and valve lifts. The work brings out a comprehensive understanding of different lift events and their effects on braking performance.

Biodegradable hydraulic fluids have been introduced relatively recently and, initially, acceptable environmental performance and technical performance were neither well specified or controlled. Over the past few years, many standards and specifications have been written, especially in the area of biodegradability and ecotoxicity. Technical performance test requirements are emerging more slowly, however, and there is still some doubt over appropriate tests and limits for some performance areas. The proliferation of standards is confusing to both the product developer and fluid user. This paper summarizes the common biodegradability and ecotoxicity elements in the main environmental performance standards. It also discusses appropriate laboratory performance tests for oxidation stability, hydrolytic stability and wear, and sets acceptable limits in these tests, based on correlation of lab and field performance of two synthetic ester based hydraulic fluids.

Using FEM (Finite Element Method) and other analytical approaches, a systematic methodology was developed to predict an engine valve's fatigue life. In this study, a steel (SAE 21-2N) exhaust valve on an engine with a type 2 valve train configuration was used as a test case. Temperature and stress/strain responses of each major event phase of the engine cycle were analytically simulated. CFD models were developed to simulate the exhaust gas flow to generate boundary conditions for a thermal model of the valve. FEM simulations accounted for thermal loads, temperature dependent material properties, thermal stresses, closing impact stresses and combustion load stresses. An estimated fatigue life was calculated using Miner's rule of damage accumulation in conjunction with the Modified Goodman approach for fluctuating stresses. Predicted life results correlated very well with empirical tests.

This paper presents the fatigue life assessment work on an engine exhaust valve subject to specified durability test cycles. Using valve stress (or strain) data from finite element methods, material fatigue data, and fatigue prediction models (i.e. SN approach and εN approach based on multi-axial Brown-Miller critical plane method), the valve life estimates were obtained and compared with the observed test data, which were in reasonable agreement. In addition, crack growth approach was used and valve crack propagation life including early stage growth was computed. Finally, a general discussion on three life estimates (i.e. fatigue total life, strain-life and crack growth life) was provided with their governing equation, supported by three real cases.

The paper covers the NOx performance evaluation of an LNT + SCR system designed to meet the 2010 on-highway heavy-duty (HD) US EPA emission standards. The system combines a fuel reformer catalyst (REF), lean NOx trap (LNT), diesel particulate filter (DPF), and selective catalytic reduction (SCR) in series, to reduce engine-out NOx and PM. System NOx reduction performance was verified in an engine dynamometer test cell, using a 2007 7.6L medium-duty engine. System NOx performance was characterized using fresh LNT and SCR along with hydrothermal aged LNT and fresh SCR. Test results show levels consistent with EPA 2010 limits under various test conditions. Catalysts performance was characterized at eight steady engine-operating conditions (A100, B50, B75, A75, B100, C100, C75, C50, across a 13-mode Supplemental Emission Test (SET), and an on-highway Heavy Duty Federal Test Procedure (HD-FTP).

On-board measurements of fuel consumption and vehicle exhaust emissions of NOx, HC, CO, CO2, and PM are being conducted for three types of commercially available city buses in Guangzhou, China. The selected vehicles for this test include a diesel bus with Eaton hybrid electric powertrain, a conventional diesel bus with automated mechanical transmission (AMT), and a LPG powered city bus with manual transmission (MT). All of the tested vehicles were instrumented with on-board measurements. Horiba OBS-2200 was used for measuring NOx, HC, and CO emissions; ELPI (Electrical Low Pressure Impactor) was used for PM measurement. The vehicles were tested at Hainan National Proving Ground in southern China. Test data of fuel consumption and exhaust emissions were analyzed. The city bus with Eaton hybrid electric powertrain demonstrated more than 27% fuel consumption reduction over the conventional diesel powered bus, and over 68% over the LPG bus.

An advanced exhaust aftertreatment system is characterized following end-of-life catalyst aging to meet final Tier 4 off-highway emission requirements. This system consists of a fuel dosing system, mixing elements, fuel reformer, lean NOx trap (LNT), diesel particulate filter (DPF), and a selective catalytic reduction (SCR) catalyst. The fuel reformer is used to generate hydrogen (H2) and carbon monoxide (CO) from injected diesel fuel. These reductants are used to regenerate and desulfate the LNT catalyst. NOx emissions are reduced using the combination of the LNT and SCR catalysts. During LNT regeneration, ammonia (NH3) is intentionally released from the LNT and stored on the downstream SCR catalyst to further reduce NOx that passed through the LNT catalyst. This paper addresses system durability as the catalysts were aged to 500 desulfation events using an off-highway diesel engine.

Commercial vehicles require continual improvements in order to meet fuel emission standards, improve diesel aftertreatment system performance and optimize vehicle fuel economy. Aftertreatment systems, used to remove engine NOx, are temperature dependent. Variable valve actuation in the form of cylinder deactivation (CDA) has been shown to manage exhaust temperatures to the aftertreatment system during low load operation (i.e., under 3-4 bar BMEP). During cylinder deactivation mode, a diesel engine can have higher vibration levels when compared to normal six cylinder operation. The viability of CDA needs to be implemented in a way to manage noise, vibration and harshness (NVH) within acceptable ranges for today’s commercial vehicles and drivelines. A heavy duty diesel engine (inline 6 cylinder) was instrumented to collect vibration data in a dynamometer test cell.

This paper discusses the effect of torque vectoring differential on improving vehicle handling and stability performance. The torque vectoring concept has been analyzed. The vehicle discussed in this paper is an AWD vehicle with torque vectoring differential in the rear and a torque biasing center differential. First, simulation results with vehicle model in CarSim® and torque vectoring control algorithm in Matlab®/Simulink® is discussed. Then, experimental results for vehicle tested at winter and summer test facility is presented. Both simulation and experimental results demonstrate the effectiveness of torque vectoring differential on vehicle handling & stability.

A detailed study, by finite element method (FEM), was conducted on an automotive engine exhaust valve subject to various loads (i.e. spring load, combustion pressure load, temperature profile and valve impact closing velocity). The 3D nonlinear (contact element and temperature-dependent) thermal-mechanical model was constructed and implicit time integration method was employed in transient dynamics under impact velocity. The predicted temperatures and maximum valve stress under impact velocity via FEM were compared with the measured test data, which were in good agreement. In addition, this study finds that the energy transfer during valve closing in normal engine operation is mainly conservative, and a linear relation exists between valve closing velocity and maximum stem stress, that was also confirmed by both test data and analytical expression presented using elastic wave and vibration theory.