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The use of exhaust gas recirculation (EGR) in internal combustion engines has significant impacts on combustion and emissions. EGR can be used to reduce in-cylinder NOx production, reduce emitted particulate matter, and enable advanced forms of combustion. To maximize the benefits of EGR, the exhaust gases are often cooled with on-engine liquid to gas heat exchangers. A common problem with this approach is the build-up of a fouling layer inside the heat exchanger due to thermophoresis and condensation, reducing the effectiveness of the heat exchanger in lowering gas temperatures. Literature has shown the effectiveness to initially drop rapidly and then approach steady state after a variable amount of time. The asymptotic behavior of the effectiveness has not been well explained. A range of theories have been proposed including fouling layer removal, changing fouling layer properties, and cessation of thermophoresis.

A bi-fuel (Compressed Natural Gas [CNG] and gasoline) pickup truck has been developed using the Ford Alternative Fuel Qualified Vehicle Modifier (QVM) process. The base vehicle's 4.9L engine has been specially modified for improved durability on gaseous fuels. The base vehicle's configuration has been designed for conversion to bi-fuel CNG operation. A complete CNG fuel system has been designed and qualified, including fuel tanks, fuel system, and electrical interface. The completed vehicle has been safety and emission certified, demonstrating CARB Low Emission Vehicle (LEV) emissions in MY95. This paper details the design objectives, development process, CNG components, and integration of the two fuel systems.

In this paper, we present the results of a series of experiments to determine the exhaust particulate size distributions from a number of diesel, gasoline and compressed natural gas (CNG) fuelled vehicles. The results show that all three types of vehicle produce significant populations of particulates under certain operating conditions. Particulates produced by gasoline and CNG engines tend to be smaller than for diesel engines. At low loads, there is a significant particulate distribution for diesel engines but much lower particulate numbers for both gasoline and CNG vehicles. Under these conditions, the gasoline particulate distribution has little structure but the CNG distribution is clearly bimodal. At higher loads, the number of particulates produced by diesel vehicles increases by an order of magnitude from idle and both the CNG and gasoline distributions are comparable in peak height. The diesel vehicle produces a much larger particulate volume than gasoline or CNG.

The idea of using a single electrical machine for both starting the engine and generating electrical power is not new. However, the real benefits, that justify the higher cost of a combined starter-alternator, become apparent when it is used as part of a hybrid powerplant. This powerplant allows a substantial improvement in fuel economy by a variety of methods (i.e. the engine shut-down during deceleration and idle, regenerative braking, etc.), as well as enhancements to engine performance, emissions, and vehicle driveability. This paper describes the analysis of the structure supporting the starter-alternator on the end of the engine crankshaft (Figure 1). It deals with the requirement to maintain a small radial gap between the rotor and stator, and it discusses how the rotor affects the loading on the crankshaft. In addition, thermal deformations of the rotor/clutch assembly are analyzed with three light-weight materials.

This paper questions whether the application of steady speed volumetric efficiency data to transient SI engine operation under WOT is a valid one. A state-of-the-art computer simulation model is used to compare steady speed volumetric efficiency with instantaneous values. A baseline engine model is first correlated with measured volumetric efficiency data to establish confidence in the engine model's predictions. A derivative of the baseline model, complete with variable geometry inlet manifold, is then subjected to a transient excursion simulating typical, in-service, maximum rates of engine speed change. Instantaneous volumetric efficiency, calculated over discrete engine cycles forming the sequence, is then compared with its steady speed counterpart at the corresponding speed. It is shown that the engine volumetric efficiency responds almost quasi-steadily under transient operation thus justifying the assumption of correlation between steady speed and transient data.

The combustion phasing of Homogeneous Charge Compression Ignition combustion is incredibly sensitive to intake temperature. Controlling the intake temperature on a cycle-to-cycle basis is one-way to control combustion phasing, however accomplishing this with an intake air heater/intercooler is unfeasible. One possible way to control the intake temperature is through the direct injection of fuel. The direct injection of fuel during the intake stroke cools the charge via evaporative cooling. Some heat is absorbed from the incoming air, lowering the in-cylinder temperature, while some heat is absorbed from the piston/cylinder walls if the spray reaches the walls. The amount of heat that is absorbed from the air vs. the walls depends on the spray penetration length. The available spray penetration length can be controlled by the injection timing during the intake stroke.