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Motor vehicle emission testing during on-road driving is important to assess a vehicle’s exhaust emission control design, its compliance with Federal regulations and its impact on air quality. The U.S. Environmental Protection Agency (EPA) has been developing new approaches to screen the characteristics of vehicle dynamic emission control behaviors (its operating signature) while driving both on-road and on-dynamometer. The so-called “signature device” used for this testing is equipped with an O2/NOx sensor, thermocouple and GPS to record dynamic exhaust NOx concentration, air fuel ratio-controlled tailpipe lambda (λ), tailpipe temperature and vehicle speed (acceleration). In the early EPA research, signature screening was used to characterize a vehicle’s PCM control behaviors (cause/effect bijectivity), which help distinguish operation in normal control state-space and abnormal state-space.

To meet US EPA light-duty vehicle emission standards, the vehicle powertrain has to be optimally controlled in addition to maintaining very high catalyst system efficiency. If vehicles are operated outside the bounds of a standard laboratory exhaust emission test (e.g., on-road or off-cycle) the operating control strategy may shift to optimize other desirable parameters such as fuel economy and drivability. Under these circumstances. The engine control system could be operating in a different state space from an emission control stand point. This control state-space can be observed based on four principal parameters: NOx, Lambda and exhaust temperature (measured at the tailpipe) and vehicle acceleration. These vehicle emission control patterns can be characterized by their corresponding emission control signatures, such as cold start, transient fuel control, and high speed/high load open loop. These emission control signatures are unique to a variety of engine technologies as well.

Modern light-duty vehicles require well-controlled engine-out feed-gas and very high catalyst efficiencies to meet the US Environmental Protection Agency (EPA) Tier 2 & 3 standards. When a vehicle with either a gasoline or diesel engine is operating within its controlled state-space the exhaust emissions present at the tailpipe are extremely low. When it is not operating within its controlled state-space the combustion process and therefore its exhaust emissions characteristics will be different. This may occur when an emission control device fails or if a defeat device is employed. Moreover, different control technologies each have unique characteristics or signatures that could assist in identifying either emission control device failure or an existing defeat device.

After initial trials on Homogeneous Charge Compression Ignition (HCCI) engine design and tests pursuing feedback control to avoid misfire and knocking over wide transient operation ranges, Engineers at the US Environmental Protection Agency's (EPA) National Vehicle Fuel and Emissions Laboratory identified the crucial engine state variable, MRPR (Maximum Rate of Pressure Rise) and successfully controlled a 1.9L HCCI engine in pure HCCI mode [1]. This engine was used to power a hybrid Ford F-150 truck which successfully ran FTP75 tests in 2004. In subsequent research, efforts have been focused on practical issues such as improving transient rate, system simplification for controllability and packaging, application of production grade in-cylinder pressure sensors, cold start, idling and calibration for ambient conditions as well as oxidation catalyst applications for better turbine efficiency and HC and CO emissions control.

To make an HCCI engine as a useful commercial product, the engine has to be capable of performing quick transients in a large operating range, especially in vehicle applications. HCCI combustion is kinetically controlled and has to be operated properly between two limits: misfire and knock. To achieve the correct state, the right amount of fuel/air/EGR has to be inducted into the cylinder. The amounts and ratios of the three components are highly dependent on other variables as operating conditions change. It is unrealistic and unreliable to predict the right combination of these variables without principal component analysis. Thus, the optimal response control path has to be based on the quality of the previous combustion event as well as the direction and the rate of transition.

IC engines have been the dominant automotive powertrain in the 20th century because of their advantages in power density, thermal efficiency, simplicity, durability and mobility. Condensing 100 years of information on automotive engine system technology evolution shows five different development stages: “bone and muscle”, “instinct”, “nerve and brain”, “intelligence”, and “system optimization”. Currently, the last step is facing the pressure of the “clean revolution” plus the “e-commerce revolution”. To meet future emission requirements and reduce CO2 emissions, the conventional engine system will be pushed to new physical limits, leading to higher cost and reduced durability. Therefore, the automobile industry should consider re-engineering or system optimization of the engines, including configuring the system architecture to be as transparent as possible to suit the fast changing environment of e-commerce.

Hydrogen Internal Combustion Engine (H2ICE) powered vehicles have been considered a low emission, low cost, practical method to help establish a hydrogen fueling infrastructure. However, the naturally aspirated H2ICE operating lean has performance issues requiring either increased displacement or induction boost to have comparable power to the modern gasoline powered IC engine. Ford Scientific Research Laboratory has continued its H2ICE system investigation, conducting dynamometer engine-boosting experiments utilizing a 2.0 L Zetec engine (with compression ratios of 14.5:1 and 12.5:1), and a 2.3L Duratec HE-4 engine (with a compression ratio of 12.2:1) with boosted manifold air pressure up to 200 kPa. Test data of brake torque and exhaust emissions are reported at various boost pressures. Results of a detailed NOx study, conducted at University of California - Riverside, with EGR and aftertreatment for a naturally aspirated 2.0L Zetec engine are also reported.

In late 1997 Ford Motor Company Scientific Research Laboratory started the project to design and develop a practical, low-cost hydrogen fueled internal combustion engine (H2ICE) vehicle. This type of vehicle could serve as an interim step to drive the development of the hydrogen infrastructure before the widespread use of fuel cell vehicles. This paper will discuss the design and development approach and results for a dedicated engine optimized for operation on hydrogen, the unique and custom instrumentation necessary when working with hydrogen, the engine dynamometer development program, the unique triple-redundant vehicle safety system, and the final implementation into the Ford P2000 experimental vehicle.

As part of the P2000 hydrogen fueled internal combustion engine (H2ICE) vehicle program, an engine dynamometer research project was conducted in order to systematically investigate the unique hydrogen related combustion characteristics cited in the literature. These characteristics include pre-ignition, NOx emissions formation and control, volumetric efficiency of gaseous fuel injection and related power density, thermal efficiency, and combustion control. To undertake this study, several dedicated, hydrogen-fueled spark ignition engines (compression ratios: 10, 12.5, 14.5 and 15.3:1) were designed and built. Engine dynamometer development testing was conducted at the Ford Research Laboratory and the University of California at Riverside. This engine dynamometer work also provided the mapping data and control strategy needed to develop the engine in the P2000 vehicle.

For future hydrogen fueled ground vehicle research, Ford Motor Company has installed the first hydrogen fueling station in North America with gaseous and cryogenic hydrogen and two dedicated hydrogen fueled engine laboratory dynamometer test cells. Hydrogen, as a fuel for internal combustion engines (ICE), requires unique approaches to assure safety and accuracy in an engine-testing lab because of hydrogen's molecular size, compressibility, and reactivity. Ford Scientific Research Lab has accumulated useful experiences during the P2000 hydrogen internal combustion engine and vehicle development program. This paper presents the safety measures used in the hydrogen lab, including gas leakage sensing and warning system, hydrogen flame detecting device, cell fresh air ventilation conventions, and hydrogen fueling and purging system.

The AFR control accuracy in the cold start is crucial to lowering emissions from IC-engine vehicles. An artificial UEGO “sensor” for estimating the real-time AFR during the engine cold start has been developed on the basis of a fuel-perturbation algorithm at Ford Scientific Research Labs. The AFR values calculated by the artificial UEGO sensor have been used in the closed-loop fuel control. Considering that the engine cold start AFR is an uncertain, non-linear problem, some other techniques for optimizing the input stimulation signal and the output-filtering model are integrated together with the fuel perturbation. This artificial sensor was realized and its performance was tested on a Ford vehicle for EPA75 cold 505 test. The assessment of the artificial sensor was quite different in comparison with that of a real UEGO sensor.

Oscillating heat transfer is a fundamental phenomenon occurring in Stirling machines and IC engines. A group of relevant dimensionless numbers which characterize this problem is identified by dimensional analysis. The convective heat transfer coefficient, or Nusselt number, is a function of the Reynolds number, the Prandtl number, plus the dynamic Reynolds number and the dimensionless amplitude, when compressibility is not considered. The case for compressible fluid is more complicated. An experiential study confirms above analysis and results in a nonlinear longitudinal fluid temperature distribution in the pipe. The history effect is found to affect the heat transfer rate remarkably. A correlation equation for Nusselt number is obtained by multivariate analysis.

A new method to estimate instantaneous A/F ratio and use the estimation as a feedback signal to control AFR during cold transients, before the oxygen sensor is functional, has been realized by a on-board PCM for a vehicle with a 4.6L, V8, PFI engine [4, 6]. Different AFRs cause variations in flame propagation, causing fluctuations in the effective torque. When a known AFR disturbance is induced into an engine system, a corresponding crankshaft angular velocity fluctuation can be detected. A variable derived from this physical phenomenon can be used to characterize the problem. The optimal fuel perturbation signal is designed by a relaxation concept, and the system model is determined by employing a dual-direction screening multivariate stepwise regression analysis. The estimated AFR is used by the PCM in a closed loop control to correct the fuel during cold transients.