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Diesel dual fuel (DDF) operated under moderate load condition emits a lot of CH4 and CO. Even these emissions have been improved significantly by Dual Fuel Premixed Charge Compression Ignition: DF-PCCI [3] combustion control technique which was proposed by the authors. However, the emission was still high as compared to diesel emissions. To overcome this problem, the new combustion control concept so called Cylinder Selective Combustion (CSC) has been proposed. From the fact that at low load condition, diesel combustion has lower CH4 and CO emissions than DDF combustion and DDF emissions can be improved significantly by DF-PCCI concept at higher load. So, in the new concept, some cylinder was selected to run with very low IMEP diesel combustion and some cylinder was selected to run with higher IMEP DF-PCCI combustion. The IMEP ratios between DF-PCCI and diesel have been optimized for each engine speed and engine load.

The diesel dual fuel engine emits CH4 in the exhaust gas. This makes the exhaust gas more difficult to treat comparing to the exhaust gas from the conventional engine since CH4 requires high exhaust temperature to oxidize. In addition, another parameter such as exhaust flow rate, specie concentrations, especially CO, C3H8, and H2O have tremendous impact on Diesel Oxidation Catalyst performance on reducing CH4. This research is aimed to propose a kinetic model based on Langmuir Hinshelwood mechanisms that includes several terms such as CH4, C3H8, CO, O2, and H2O concentrations in order to gain a better understanding on the catalytic reaction and to provide a simulation with an accurate prediction. The model’s kinetic parameters are determined from the experiment by using synthetic gas. The composition of synthetic gas is simulated to be similar to the real exhaust gas from diesel dual fuel engines.

End of line test (EOL) of Engine Control Units (ECU) is the process of ECU functions validation before releasing ECUs to the car assembly process. Examples of ECU function that need to be validated are idle control, air path control and faults manager function. To perform EOL, a vehicle and a chassis dynamometer are used to enable control functions validation inside the ECU. However, this poses high operating cost and long setup time. This paper presents the development of Hardware-in-the-Loop (HiL) system, which imitates real vehicle behavior on a chassis dynamometer. The diesel high pressure pump model was developed using an empirical dynamic modeling approach. The engine model was developed using AVL BOOST RT software, an engine cycle simulation modeling approach. The vehicle model was developed using AVL CRUISE software. In order to interface the engine and vehicle models with the ECU, HiL system was implemented.

Towards the effort of using natural gas as an alternative fuel for a diesel engine, the concept of Diesel Dual Fuel (DDF) engine has been shown as a strong candidate. Typically, DDF's engine-out emission species such as soot and nitrogen oxides are decreased while carbon monoxide and hydrocarbons are increased. The aftertreatment system is required in order to reduce these pollutant emissions from DDF engines. Additionally, DDF engine exhaust has a wide temperature span and is rich in oxygen, which makes HC emissions, especially methane (CH₄), difficult to treat. Until now, it is widely accepted that the key parameter influencing methane oxidation in a catalytic converter is high exhaust temperature. However, a comprehensive understanding of what variables in real DDF engine exhausts most influencing a catalytic converter performance are yet to be explored.

The current study examined diesel dual fuel (DDF) operations in a four-cylinder turbocharged diesel engine under low load conditions. Experiments were performed to investigate effects of diesel injection timings and exhaust valve timing advance for DDF operations under high levels of natural gas utilization. Results showed that diesel injection timings played an important role in DDF combustion. Increasing the ratio of natural gas to total fuel resulted in greater amounts of HC and CO emissions. Advancing the exhaust valve timing increased the internal EGR, raised the in-cylinder temperature at IVC, and improved the combustion efficiency. To maximize the ratio of natural gas to total fuel, a combination of proper exhaust valve timing advance and a tuned timing of diesel injection should be employed to avoid excessive HC and CO emissions.

Knock behavior in diesel-dual-fuel (DDF) engine is more complex, more severe, and different than those of traditional engines. We investigate a type of diesel-dual-fuel engines, where CNG is multipoint-injected at the intake ports as main fuel and diesel is directly injected in smaller amount, mainly for ignition purpose, resulting in lower fuel cost. Because of the mixed behaviors between the spark ignited and compression ignited engines, a more sophisticated control system is needed to properly control knock in the DDF engine. In this paper, a novel control system based on fuzzy logic is presented to regulate knock intensity at an appropriate level. The control system comprises a fuzzy controller and a fuzzy decision maker. The fuzzy controller controls several pertaining actuators using rule-base from human experience, while the fuzzy decision maker adapts the magnitude of each actuator action to various operating points.

In diesel-dual-fuel engine, CNG is injected at the intake ports and diesel fuel is injected at the cylinders. As a result of using CNG as main fuel, smaller amount of diesel is used mainly for ignition, resulting in lower fuel cost. However, stricter air path control is required because the engine now operates partly as a port fuel injection engine and partly as a diesel engine. As is evident from engine calibration, desired MAP and MAF have more abrupt change with wider range than those of diesel engine. In typical commercial truck, MAP and MAF are controlled separately using traditional controller such as PID with marginal control performance. Recently, more researchers have combined the control of MAP and MAF together as multivariable problem because both quantities reflect the behavior of the air path. In this paper, multivariable sliding mode control (SMC) is implemented in two-approaches, a model-reference-based and an integrator-augmented based.

From our experiences in converting diesel engine into diesel-dual-fuel engine with natural gas as primary fuel, accurate air/fuel ratio control is vital to the high engine performance, good vehicle drivability, and low emissions. Two components enter in calculating the air/fuel ratio, namely, the amount of fresh air and the amount of diesel and natural gas. Throttle and EGR valve are two actuators directly affect the amount of air, and the desired total fuel determines how much fuel should be injected at an instance. As opposed to inactive, fully opened throttle in typical diesel engine, the throttle in diesel-dual-fuel engine is regulated to cover wider range of desired air/fuel ratio. As a result, the problem of controlling the amount of air in diesel-dual-fuel engine becomes that of multi variables in which both throttle and EGR valve are involved. We present a novel algorithm that breaks the multi-variable control problem into two single-variable problems.

In this paper, we investigate a multivariable control of air path of a diesel-dual-fuel (DDF) engine. The engine is modified from a CI engine by injecting CNG in intake ports. The engine uses CNG as its primary fuel and diesel as its secondary fuel, mainly for initiation of combustion. The modification is economically attractive because CNG has lower price than diesel and the modification cost is minimal. However, for DDF engine, control of the air path becomes more difficult because the engine now has combined characteristics of the CI and the SI engines. The combined characteristics come from the fact that diesel is still directly injected into cylinders (CI engine) while CNG is injected at the intake ports (SI engine.) In pure CI engine, throttle is normally fully opened for maximum air intake, while EGR valve is actively actuated to obtain low emissions. In pure SI engine, however, throttle is an active actuator, driven by pedal.

Accurate air-fuel ratio control is required for good engine performance and low emission in diesel dual fuel engine. Two actuators directly affect the ratio are the air throttle and the EGR valve. Maximum air throttle opening is favorable to minimize pumping loss, and the EGR valve opening should follow closely the values in a well-tuned map to minimize emission. In the past, the two actuators were either controlled separately or simultaneously to achieve the air-fuel ratio set point without much consideration on the actuators' opening positions. We proposed a logic that alternated between actuating the air throttle and the EGR valve to maintain optimum air throttle opening. Since each actuator was controlled one at a time, the overall control system was simplified, yet any advanced controller could be applied to increase the accuracy of each actuator.

Accurate common-rail pressure control is vital to good engine performance and low emission. Injection strategy of diesel-dual-fuel engine varies more greatly with speed and load than its diesel engine predecessor, and so does the common-rail pressure set point. Along with this swift set point change, other control challenges exist; they are speed-and-load variation, model uncertainty, sensor noise, actuator nonlinearity, and pressure disturbance from injection. Traditional control such as the PID was proved to be only marginally effective because of the swift set point change. We proposed integrating an integrator-augmented sliding-mode control with gain scheduling and feed-forward term. The sliding-mode control has fast action and is low sensitive to model uncertainty and disturbance. The augmented integrator ensures zero steady-state error. The gain scheduling handles the speed-and-load variation. The feed-forward term helps with the actuator nonlinearity.

In the skyrocketing fuel price situation, using natural gas by means of a diesel dual fuel (DDF) conversion technique is a promising technology as it is flexible for diesel trucks. However, DDF engines suffer from low engine efficiency and poor emission characteristics at low-to-medium load operations. In this study, two DDF concepts were proposed by using five operating parameters including 1) the number of injection pulses, 2) duration of each injection pulse, 3) injection timing, 4) throttle position, and 5) EGR. The first three parameters were varied in the first concept whereas all parameters were varied in the second one. Results from these two DDF conversion concepts were compared to the simple conversion where the operating parameters for diesel injections were fixed by the standard ECU of the OEM. At light load (2000 rpm, 3.1-bar IMEP), the brake efficiencies in the first and the second concepts were improved from the simple conversion by 21% and 35%, respectively.

Despite promising future, the diesel-dual-fuel engine, with diesel as pilot and natural gas as main, abounds with challenges from high NOx emission and knock especially at high speed and low load. To cope with these challenges, variation of common-rail pressure provides another desirable degree of freedom. Nevertheless, crippling with complicated dynamics, pressure wave inside the transporting rail, disturbance from varying of injections, engine speed variation, and actuator limitation, common-rail pressure control has relied on the simple PID to deliver only marginally satisfactory result. Some attempts to achieve better control have resulted in either too complicated or not too robust control system. We devise a controller from the quantitative feedback theory.

Diesel Dual Fuel (DDF) operation is a promising alternative engine operating mode. Previous research studies have reported a DDF engine operating under low load conditions suffers from high HC emissions, mostly Methane. The current study investigated the use of a multiple direct injection strategy for improvement of low-load DDF operation in a commonrail direct injection single-cylinder diesel engine. Natural gas was supplied at 70% of energy replacement ratio. Results indicated that depending on engine conditions, a double-pulse injection had potential for combustion control and provided an effective way to reduce NOx and methane emissions. Moreover, the double-pulse injection helped improve the combustion stability, reduce the pressure rise rate, and decrease the maximum cylinder pressure, compared to DDF operation with a single pulse injection.

The diesel/natural gas engine configuration provides a potential alternative solution for PM and NOx emissions reduction from typical diesel engine operations. However, their engine operations suffer from high NMHC/methane emissions and poor engine performance, especially at light loads. By increasing the diesel pilot quantity, the performance and reduction of NMHC/methane emissions can be improved but the emission levels are still very high. Clearly, a typical DOC is not good enough to treat NMHC/methane emissions. Methane has been known as one of most stable species that is difficult to catalytically oxidize in lean burn environment and low exhaust temperatures. An aftertreatment system exclusively designed for treating methane emissions from DDF operations is therefore necessary. The current work is aimed to establish an effective computational tool in order to study the newly proposed catalytic converter system concept on treating methane from DDF operations.