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TWC exposure to extreme temperature could result in irreversible damage or thermal failure. Thus, a strategy embedded in the engine control unit (ECU) called catalyst overheating protection (COP) will be activated to prevent TWC overheating. When COP is activated, the command air-fuel ratio will be enriched to cool the catalyst monolith down. Fuel enrichment has been proven a main prerequisite for ammonia formation in hot TWCs as a by-product of NOx reduction. Hence, COP events could theoretically be a source of post-catalyst ammonia from petrol vehicles, but this theory is yet to be confirmed in published literature. This paper validated this hypothesis using a self-programmed chassis-level test. The speed of the test vehicle was set to constant while the TWC temperature was raised stepwise until a COP event was activated.

To meet the strict emission regulations for diesel engines, an advanced processing device such as a Urea-SCR (selective catalytic reduction) system is used to reduce NOx emissions. The Real Driving Emissions (RDE) test, which is implemented in the European Union, will expand the range of conditions under which the engine has to operate [1], which will lead to the construction of a Urea-SCR system capable of reducing NOx emissions at lower and higher temperature conditions, and at higher space velocity conditions than existing systems. Simulations are useful in improving the performance of the urea-SCR system. However, it is necessary to construct a reliable NOx reduction model to use for system design, which covers the expanded engine operation conditions. In the urea-SCR system, the mechanism of ammonia (NH3) formation from injected aqueous urea solution is not clear. Thus, it is important to clarify this mechanism to improve the NOx reduction model.

In the urea SCR system, urea solution is injected by injector installed in the front stage of the SCR catalyst, and NOx can be purified on the SCR catalyst by using NH3 generated by the chemical reaction of urea. NH3 is produced by thermolysis of urea and hydrolysis of isocyanic acid after evaporation of water in the urea solution. But, biuret and cyanuric acid which may cause deposit are sometimes generated by the chemical reactions without generating NH3. Spray behavior and chemical reaction of urea solution injected into the tail-pipe are complicated. The purpose of this study is to reveal the spray behavior and NH3 generation process in the tail-pipe, and to construct the model capable of predicting those accurately. In this report, the impingement spray behavior is clarified by scattered light method in high temperature flow field. Liquid film adhering to the wall and deposit generated after evaporation of water from the liquid film are photographed by the digital camera.

Dual-fuel combustion combining a premixed charge of compressed natural gas (CNG) and a pilot injection of diesel fuel offer the potential to reduce diesel fuel consumption and drastically reduce soot emissions. In this study, dual-fuel combustion using methane ignited with a pilot injection of No. 2 diesel fuel, was studied in a single cylinder diesel engine with optical access. Experiments were performed at a CNG substitution rate of 70% CNG (based on energy) over a wide range of equivalence ratios of the premixed charge, as well as different diesel injection strategies (single and double injection). A color high-speed camera was used in order to identify and distinguish between lean-premixed methane combustion and diffusion combustion in dual-fuel combustion. The effect of multiple diesel injections is also investigated optically as a means to enhance flame propagation towards the center of the combustion chamber.

Radial flow Variable Nozzle Turbine (VNT) enables better matching between the turbocharger and engine. At partial loading or low-end engine operating points, the nozzle vane opening of the VNT is decreased to achieve higher turbine efficiency and transient response, which is a benefit for engine fuel consumption and emission. However, under certain small nozzle opening conditions (such as nozzle brake and low-end operating points), strong shock waves and strong nozzle clearance flow are generated. Consequently, strong rotor-stator interaction between turbine nozzle and impeller is the key factor of the impeller high cycle fatigue and failure. In present paper, flow visualization experiment is carried out on a linear turbine nozzle. The turbine nozzle is designed to have single-sided clearance, and the Schlieren visualization method is used to describe the formation and development process of clearance flow and shock wave under different clearance and expansion ratio configurations.

Exhaust gas recirculation (EGR) has been proven an effective strategy for the ignition and combustion control in homogeneous charge compression ignition (HCCI) engines. Carbon dioxide (CO2), a major constituent in EGR, was found to pose a coupled effect on engine combustion: reduced intake oxygen concentration (dilution effect), increased gas heat capacity (thermal effect) and participation of CO2 in chemical reactions (chemical effect). In this paper, a numerical study using a detailed chemical kinetic model was conducted, aiming to isolate the dilution, thermal and chemical effects of CO2 on the two-stage auto-ignition process of n-heptane at engine-like pressure conditions. Four different initial temperatures were selected in this study, representing the low-temperature dominant region, the boundary between the low-temperature region and the negative temperature coefficient (NTC) region, the NTC region and the high temperature region, respectively.

The concept of regulated two-stage turbocharging system is proposed to provide high boost pressure level over a wide range of engine speed by regulating the energy distribution of two turbochargers. However, the control strategy of turbine bypass valve becomes more complicated due to the frequently changing working of vehicle diesel engines. In this paper, a two-stage turbocharging system was matched for D6114 diesel engine to improve the low-speed torque. The effect of valve opening on the steady-state and transient performance was analyzed, and two different regulating laws were determined according to the different optimum aims. Then the transient response characteristics of two different regulating laws were studied and optimized at three speeds with the transient loading test. For steady-state performance, the output power and fuel efficiency were increased with the matched turbocharging system.

Numerous studies describe the fuel consumption benefits of changing the powertrain temperature based on vehicle operating conditions. Actuators such as electric water pumps and active thermostats now provide more flexibility to change powertrain operating temperature than traditional mechanical-only systems did. Various control strategies have been proposed for powertrain temperature set-point regulation. A characteristic of powertrain thermal management systems is that the operating conditions (speed, load etc) change continuously to meet the driver demand and in most cases, the optimal conditions lie on the edge of the constraint envelope. Control strategies for set-point regulation which rely purely on feedback for disturbance rejection, without knowledge of future disturbances, might not provide the full fuel consumption benefits due to the slow thermal inertia of the system.

It is found that biodiesel has a great potential to reduce the nitrogen oxides (NOx) and soot emissions simultaneously in low temperature combustion (LTC) mode. The objective of this study is to investigate the combustion and emission characteristics of 20% biodiesel blend diesel fuel (B20) under several exhaust gas recirculation (EGR) conditions for LTC application. An experimental investigation of B20 was conducted on a four-stroke common rail direct injection diesel engine at 2000rpm and 25% load condition. The EGR ratio was adjusted from 10% to 66%, and the injection pressure was tuned from 100MPa to 140MPa. The result showed that B20 generated less soot emission than conventional diesel with increasing EGR ratio, especially when the EGR ratio was beyond 30%. Soot emission increased with increasing EGR ratio up to 50% EGR, after which there is a steep decrease in particular matter (PM).

Because of its cleanness and renewability, biodiesel has a great potential as the alternative of diesel fuel to confront with the increasing energy crisis and environment pollution. In this study, diesel oxidation catalyst (DOC) was used to reduce the typical regulated emission and particulate emission. The combined method of fuel design concept with diesel oxidation catalyst was applied in this study. DOC with Pt catalyst was equipped in the engine test bench in this study. The effects of DOC on diesel engine particulate emission fueled with Euro V diesel fuel, biodiesel and ethanol-biodiesel blends were investigated in this study. It was found that DOC seemed have no effects on NOx emission, while it could improve the oxidation reaction from NO to NO2. In the section of particulate emission, DOC could reduce the particulate mass and number concentration, especially in the range of smaller diameter particles. The SOF could be reduced effectively with DOC.

This paper studies the effect of cooled EGR on fuel consumption and anti-knock performance of a boosted port fuel injection (PFI) SI engine. Experimental results show that the cooled EGR increases the thermal efficiency by 2%∼18% depending on the operation conditions. Compared to low load operations, more improvements of the thermal efficiency are obtained at higher loads, primarily owing to the enhanced anti-knock performance, advanced combustion phasing, elimination of fuel-rich operations as well as reduced heat transfer loss with cooled EGR. The anti-knock performance of cooled EGR provides further potential to improve the thermal efficiency by increasing the compression ratio. To this end, a 1-D thermodynamic model of the engine is built and calibrated using the GT-Power code. A knock prediction correlation considering EGR is developed and validated with the experimental data.

NOx are the only harmful emissions of hydrogen internal combustion engine. EGR is one of the effective methods to reduce NOx. The traditional EGR is not suitable for hydrogen internal combustion engine. Therefore, the study of influence of hot EGR on hydrogen internal combustion engine is important. A 2.0L hydrogen internal combustion engine with hot EGR system model is employed to optimize the diameter and position of hot EGR based on a simulation analysis. The result shows that both of the combustion temperature and NOx increase as EGR increases due to the rise of intake temperature for low load condition, for heavy load, with the increase of EGR rate, NOx emissions decreases slightly before the mixture equivalence ratio comes to 1and then dropped significantly after the mixture equivalence ratio greater than 1. Unburned hydrogen in TWC has the effect of reducing NOx after catalysts decrease largely.

The NOx conversion efficiency of vanadium-based SCR catalyst is lower under low temperature. Utilizing an exhaust analyzer, the effects of electrically heated catalyst on the performance of vanadium-based SCR catalyst under low temperature was studied on the engine test bench. The inlet temperature of SCR catalyst without the electrically heated catalyst were in the range of 150°C∼270°C under various steady engine modes, and the NSR (Normalized Stoichiometric Ratio) was set as 0.4,0.6,0.8,1.0. The results showed that under the space velocity of 20000h−1, with the application of the electrically heated catalyst, the inlet temperature of SCR increased about 19.9°C on average and the NOx conversion efficiency improved about 8.0%. The NOx conversion efficiency increased 1.7%∼8.6% at the temperatures of 150°C∼174°C, and 1.0%∼15.9% at the temperatures of 186°C∼270°C.

Nowadays, the world is facing severe energy crisis and environment problems. Development of hydrogen fuel vehicles is one of the best ways to solve these problems. Due to the difficulties of infrastructures, such as the hydrogen transport and storage, hydrogen fuel vehicles have not been widely used yet. As a result, Hydrogen-gasoline dual-fuel vehicle is a solution as a compromise. In this paper, three way catalytic converter (TWC) was used to reduce emissions of hydrogen-gasoline dual-fuel vehicles. On wide open throttle and load characteristics, the conversion efficiency of TWC in gasoline engine was measured. Then the TWC was connected to a hydrogen internal combustion engine. After switching the hydrogen and gasoline working mode, emission data was measured. Experiment results show that the efficiency of a traditional TWC can be maintained above 85%., while it works in a hydrogen-gasoline dual-fuel alternative working mode.

In order to meet more stringent evaporative emissions requirements, multiple advancements in vehicle fuel system and carbon canister technologies have been made. Regardless of technological advancements, the vapor pressure of the fuel remains a vital property in controlling evaporative emissions. A series of tests were performed to explore the effects of vapor pressure on multiday diurnal evaporative emissions for 9 and 10 psi Reid Vapor Pressure (RVP) 10% ethanol (E10) gasoline-blend fuels, followed by tests with 7 psi RVP E10 gasoline on a subset of the same vehicles. A test procedure was developed to monitor evaporative emissions, canister loading profiles and breakthrough emissions for each of the fuels. A total of five vehicles were tested on all 3 fuels, blended to represent 7, 9, and 10 psi at sea level. Tests were run over 14 days using the United States (U.S.)

For spark-ignition gasoline engines operating under the wide speed and load conditions required for light duty vehicles, ignition quality limits the ability to minimize fuel consumption and NOx emissions via dilution under light and part load conditions. In addition, during transients including tip-outs, high levels of dilution can occur for multiple combustion events before either the external exhaust gas can be adjusted and cleared from the intake or cam phasing can be adjusted for correct internal dilution. Further improvement and a thorough understanding of the impact of the ignition system on combustion near the dilution limit will enable reduced fuel consumption and robust transient operation. To determine and isolate the effects of multiple parameters, a variable output ignition system (VOIS) was developed and tested on a 3.5L turbocharged V6 homogeneous charge direct-injection gasoline engine with two spark plug gaps and three ignition settings.

As a renewable energy source, the ethanol fuel was employed with a diesel fuel in this study to improve the cylinder charge homogeneity for high load operations, targeting on ultra-low nitrogen oxides (NOx) and smoke emissions. A light-duty diesel engine is configured to adapt intake port fuelling of the ethanol fuel while keeping all other original engine components intact. High load experiments are performed to investigate the combustion control and low emission enabling without sacrificing the high compression ratio (18.2:1). The intake boost, exhaust gas recirculation (EGR) and injection pressure are independently controlled, and thus their effects on combustion and emission characteristics of the high load operation are investigated individually. The low temperature combustion is accomplished at high engine load (16~17 bar IMEP) with regulation compatible NOx and soot emissions.

Alkali and alkaline earth metal impurities found in diesel fuels are potential poisons for diesel exhaust catalysts. Using an accelerated aging procedure, a set of production exhaust systems from a 2011 Ford F250 equipped with a 6.7L diesel engine have been aged to an equivalent of 150,000 miles of thermal aging and metal exposure. These exhaust systems included a diesel oxidation catalyst (DOC), selective catalytic reduction (SCR) catalyst, and diesel particulate filter (DPF). Four separate exhaust systems were aged, each with a different fuel: ULSD containing no measureable metals, B20 containing sodium, B20 containing potassium and B20 containing calcium. Metals levels were selected to simulate the maximum allowable levels in B100 according to the ASTM D6751 standard. Analysis of the aged catalysts included Federal Test Procedure emissions testing with the systems installed on a Ford F250 pickup, bench flow reactor testing of catalyst cores, and electron probe microanalysis (EPMA).

Chrysler, Ford, General Motors, the U.S. Environmental Protection Agency (EPA) and the California Air Resources Board (CARB) have collaborated over the past two years to develop an efficiency test for mobile air conditioner (MAC) systems. Because the effect of efficiency differences between different MAC systems and different technologies is relatively small compared to overall vehicle fuel consumption, quantifying these differences has been challenging. The objective of this program was to develop a single dynamic test procedure that is capable of discerning small efficiency differences, and is generally representative of mobile air conditioner usage in the United States. The test was designed to be conducted in existing test facilities, using existing equipment, and within a sufficiently short time to fit standard test facility scheduling. Representative ambient climate conditions for the U.S. were chosen, as well as other test parameters, and a solar load was included.

In-line hydrocarbon (HC) traps are not widely used to reduce HC emissions due to their limited durability, high platinum group metal (PGM) concentrations, complicated processing, and insufficient hydrocarbon (HC) retention temperatures required for efficient conversion by the three-way catalyst component. New trapping materials and system architectures were developed utilizing an engine dynamometer test equipped with dual Fourier Transform Infrared (FTIR) spectrometers for tracking the adsorption and desorption of various HC species during the light-off period. Parallel laboratory reactor studies were conducted which show that the new HC trap formulations extend the traditional adsorption processes (i.e., based on physic-sorption and/or adsorption at acid sites) to chemical reaction mechanisms resulting in oligomerized, dehydro-cyclization, and partial coke formation.