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This session focuses on kinetically controlled combustion. Experimental and simulation studies pertaining to various means of controlling combustion are welcome. Examples are research studies dealing with temperature and composition distribution inside the cylinder and their impact on heat release process. Studies clarifying the role of fuel physical and chemical properties in autoignition are also welcome. Presenter Hanho Yun, General Motors Company

Gasoline turbocharged direct injection (GTDI) engines, such as EcoBoost™ from Ford, are becoming established as a high value technology solution to improve passenger car and light truck fuel economy. Due to their high specific performance and excellent low-speed torque, improved fuel economy can be realized due to downsizing and downspeeding without sacrificing performance and driveability while meeting the most stringent future emissions standards with an inexpensive three-way catalyst. A logical and synergistic extension of the EcoBoost™ strategy is the use of E85 (approximately 85% ethanol and 15% gasoline) for knock mitigation. Direct injection of E85 is very effective in suppressing knock due to ethanol's high heat of vaporization - which increases the charge cooling benefit of direct injection - and inherently high octane rating. As a result, higher boost levels can be achieved while maintaining optimal combustion phasing giving high thermal efficiency.

Internal combustion (IC) engines fueled by hydrogen are among the most efficient means of converting chemical energy to mechanical work. The exhaust has near-zero carbon-based emissions, and the engines can be operated in a manner in which pollutants are minimal. In addition, in automotive applications, hydrogen engines have the potential for efficiencies higher than fuel cells.[1] In addition, hydrogen engines are likely to have a small increase in engine costs compared to conventionally fueled engines. However, there are challenges to using hydrogen in IC engines. In particular, efficient combustion of hydrogen in engines produces nitrogen oxides (NOx) that generally cannot be treated with conventional three-way catalysts. This work presents the results of experiments which consider changes in direct injection hydrogen engine design to improve engine performance, consisting primarily of engine efficiency and NOx emissions.

New emissions certification requirements for medium duty vehicles (MDV) meeting chassis dynamometer regulations in the 8,500 lb to 14,000 lb weight classes as well as heavy duty (HD) engine dynamometer certified applications in both the under 14,000 lb and over 14,000 lb weight classes employing large diameter exhaust pipes (up to 4″) have created new exhaust stream sampling concerns. Current On-Board-Diagnostic (OBD) dyno certified particulate matter (PM) requirements were/are 7x the standard for 2010-2012 applications with a planned phase in down to 3x the standard by 2017. Chassis certified applications undergo a similar reduction down to 1.75x the standard for 2017 model year (MY) applications. Failure detection of a Diesel Particulate Filter (DPF) at these low detection limits facilitates the need for a particulate matter sensor.

During the 1980s, the U.S. Environmental Protection Agency (EPA) incorporated the R factor into fuel economy calculations in order to address concerns about the impacts of test fuel property variations on corporate average fuel economy (CAFE) compliance, which is determined using the Federal Test Procedure (FTP) and Highway Fuel Economy Test (HFET) cycles. The R factor is defined as the ratio of the percent change in fuel economy to the percent change in volumetric heating value for tests conducted using two differing fuels. At the time the R-factor was devised, tests using representative vehicles initially indicated that an appropriate value for the R factor was 0.6. Reassessing the R factor has recently come under renewed interest after EPA's March 2013 proposal to adjust the properties of certification gasoline to contain significant amounts of ethanol.

A single-cylinder Direct Injection Spark Ignition (DISI) engine with optical access was used to investigate the effects of ethanol/gasoline blends on in-cylinder formation of particulate matter (PM) and fuel spray characteristics. Indolene was used as a baseline fuel and two blends of 50% and 85% ethanol (by volume, balance indolene) were investigated. Time resolved thermal radiation (incandescence/natural luminosity) of soot particles and fuel spray characteristics were recorded using a high speed camera. The images were analyzed to quantify soot formation in units of relative image intensity as a function of important engine operating conditions, including ethanol concentration in the fuel, fuel injection timing (250, 300 and 320° bTDC), and coolant temperature (25°C and 90°C). Spatially-integrated incandescence was used as a metric to quantify the level of in-cylinder PM formed at the different operating conditions.

Engine dynamometer testing was performed comparing fuels having different octane ratings and ethanol content in a Ford 3.5L direct injection turbocharged (EcoBoost) engine at three compression ratios (CRs). The fuels included midlevel ethanol “splash blend” and “octane-matched blend” fuels, E10-98RON (U.S. premium), and E85-108RON. For the splash blends, denatured ethanol was added to E10-91RON, which resulted in E20-96RON and E30-101 RON. For the octane-matched blends, gasoline blendstocks were formulated to maintain constant RON and MON for E10, E20, and E30. The match blend E20-91RON and E30-91RON showed no knock benefit compared to the baseline E10-91RON fuel. However, the splash blend E20-96RON and E10-98RON enabled 11.9:1 CR with similar knock performance to E10-91RON at 10:1 CR. The splash blend E30-101RON enabled 13:1 CR with better knock performance than E10-91RON at 10:1 CR. As expected, E85-108RON exhibited dramatically better knock performance than E30-101RON.

This paper presents engine dynamometer testing and modeling analysis of ethanol compared to gasoline at part load conditions where the engine was not knock-limited with either fuel. The purpose of this work was to confirm the efficiency improvement for ethanol reported in published papers, and to quantify the components of the improvement. Testing comparing E85 to E0 gasoline was conducted in an alternating back-to-back manner with multiple data points for each fuel to establish high confidence in the measured results. Approximately 4% relative improvement in brake thermal efficiency (BTE) was measured at three speed-load points. Effects on BTE due to pumping work and emissions were quantified based on the measured engine data, and accounted for only a small portion of the difference.

A single-cylinder, spark-ignited engine was run on a certification test gasoline to saturate the oil in the sump with fuel through exposure to blow-by gas. The sump volume was large relative to production engines making its absorption-desorption time constant long relative to the experimental time. The engine was motored at 1500 RPM, 90° C coolant and oil temperature, and 0.43 bar MAP without fuel flow. Exhaust HC concentrations were measured by on-line FID and GC analysis. The total motoring HC emissions were 150 ppmC1; the HC species distribution was heavily weighted to the low-volatility components in the gasoline. No high volatility components were visible. The engine was then fired on isooctane fuel at the above conditions, producing a total engine-out HC emission of 2300 ppmC1 for Φ = 1.0 and MBT spark timing.

Automotive fuel injectors have been adapted with electrodes that enable negative electric charge to be inserted into the fuel flowing through the injector. Because the fuel is electrically very insulating and flowing rapidly, a significant amount of charge is retained in the fuel as it issues from the injector. Once exposed to the atmosphere, the charge laden fuel both atomizes and spatially disperses due to electrostatic forces. By varying the amount of inserted charge, the spray pattern can be varied significantly. This added variability allows the possibility of changing the fuel presentation when fuel is injected into the intake port of a typical spark ignited engine. A variable presentation may be useful for optimizing fuel evaporation within the port, with a corresponding reduction of exhaust emissions, during the cold start period of the engine when those parameters affecting evaporation are changing both temporally and spatially.

Ford Motor Company is researching and developing multiple propulsion strategies which include advanced gasoline engines, clean diesel, flexible fuel (ethanol blends up to E-85), hybrids and hydrogen propulsion, both in internal combustion (IC) engines and fuel cells. Hydrogen utilized as a transportation fuel is viewed as a long term solution as it is sustainable and clean when derived from renewable resources. The development and use of hydrogen IC engine (H2ICE) technology can readily be utilized to drive the transition strategy from the petroleum economy to the hydrogen economy. Because the “more conventional” H2ICE systems can be brought to market more quickly and in higher volume, business initiatives for hydrogen fueling infrastructure and other hydrogen complimentary required technologies can be realized sooner. To that end Ford has fully re-engineered a 6.8L Triton V-10 engine to run on hydrogen and power an E-450 shuttle van.

Fuel-air mixing in a direct-injection SI engine was studied to further improve full-load torque output. The fuel-injection location of DI vs. PFI results in different heat sources for fuel evaporation, hence a DI engine has been found to exhibit higher volumetric efficiency and lower knocking tendency, resulting in higher full-load torque output [1]. The ability to change injection timing of the DI engine affects heat transfer and mixture temperature, hence later injection results in lower knocking tendency. Both the higher volumetric efficiency and the lower knocking tendency can improve engine torque output. Improving volumetric efficiency requires that the fuel is injected during the intake stroke. Reducing knocking tendency, in contrast, requires that the fuel is injected late during the compression stroke. Thus, a strategy of split injection was proposed to compromise the two competing requirements and further increase direct-injection SI engine torque output.

Gasoline direct injection is one of the main issues of actual worldwide SI engine development activities. It requires a comprehensive system approach from the basic considerations on optimum combustion system configuration up to vehicle performance and driveability. The general characteristics of currently favored combustion system configurations are discussed in this paper regarding both engine operation and design aspects. The engine performance, especially power output and emission potential of AVL's DGI engine concept is presented including the interaction of advanced tools like optical diagnostics and 3D-CFD simulation in the combustion system development process. The application of methods like tomographic combustion analysis for investigations in the multicylinder engine within further stages of development is demonstrated. The system layout and operational strategies for fuel economy in conjunction with exhaust gas aftertreatment requirements are discussed.

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.

In the past application of alternative fuels was mostly concentrated to special markets - e.g. for ethanol and ethanol blends Brazil or Sweden. Now an increasing sensitivity towards dependency on crude oil significantly enhances the interest in alternative fuels. With spark ignited engines, ethanol and gasoline / ethanol blends are the most promising alternative fuels - besides CNG. The high octane number of ethanol and the resulting excellent knock performance gives significant benefits, especially with highly boosted engines. However, the evaporation characteristics of ethanol result in challenges regarding cold start and oil dilution with GDI application. This paper deals with investigations on a turbocharged DI engine operated on ethanol fuel in order to improve challenges of ethanol fuel, such as oil dilution and cold start. Cold start can be improved by injecting fuel late in the compression stroke (high pressure start) based on a refined engine design and operation strategies.

The occurrence of flash boiling in the fuel spray of a Port Fuel Injected (PFI) spark ignition engine has been observed and photographed during normal automotive vehicle operating conditions. The flash boiling of the PFI spray has a dramatic affect on the fuel spray characteristics such as droplet size and spray cone angle which can affect engine transient response, intake valve temperature and possibly hydrocarbon emissions. A new method of correlating the spray behavior using the equilibrium vapor/liquid (V/L) volume ratio of the fuel at the measured fuel temperature and manifold pressure is introduced.

A review of flame kernel growth in SI engines and the regimes of premixed turbulent combustion showed that a misfire model based on regimes of premixed turbulent combustion was warranted[1]. The present study will further validate the misfire model and show that it has captured the dominating physics and avoided extremely complex, yet inefficient, models. Results showed that regimes of turbulent combustion could, indeed, be used for a concept-simple model to predict misfire limits in SI engines. Just as importantly, the entire regimes of premixed turbulent combustion in SI engines were also mapped out with the model.

Robust on-board diagnosis of emission catalyst performance requires the development of artificially damaged "threshold" catalysts that accurately mimic the performance of damaged catalysts in customer use. The threshold catalysts are used by emissions calibrators to determine fore-aft exhaust oxygen sensor responses that indicate catalyst failure. Rather than rely on traditional trial-and-error processes to generate threshold catalysts, we have used a DFSS (Design For Six-Sigma) approach that explores, at a research level, the relationship between oxygen storage capacity (OSC) of the catalyst (i.e., the fundamental property dictating the response of the aft oxygen sensor) and key process input variables: high-temperature exposure, phosphorus poisoning, and catalyst "recovery."

Gasoline direct injection and turbocharging enable the progress of clean and fuel efficient SI engines. Accessing potential efficiency benefits requires very high power density to be achieved across a broad rpm range. This imposes risks which in conventional engines are rarely met. However, at torque levels exceeding 25 bar BMEP, the thermal in-cylinder conditions together with chemical reactivity of any ignitable matter, require major efforts in combustion system development. The paper presents a methodology to identify and locate sporadic self ignition events and it demonstrates non contact surface temperature measurement techniques for in-cylinder and exhaust system components.

Exhaust gas temperature is often measured with a device such as thermocouple or RTD (Resistance Temperature Detector). An alternative method to determine the gas temperature would be to use an existing gas sensor heating mechanism to perform as a temperature sensor. A planar type FLOH (Fast Light Off HEGO-Heated Exhausted Gas Oxygen) sensor under transient vehicle speed/load conditions is suited to this function and was modeled to predict the exhaust gas temperature. The numerical input to the model includes exhaust flow rate, heater voltage, and heater current. Laboratory experiments have been performed to produce an equation relating the resistance of the heater and the temperature of the sensor (heater), which provides a method to indirectly determine HEGO sensor temperature.