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A global, systems-level model which characterizes the thermal behavior of internal combustion engines is described in this paper. Based on resistor-capacitor thermal networks, either steady-state or transient thermal simulations can be performed. A two-zone, quasi-dimensional spark-ignition engine simulation is used to determine in-cylinder gas temperature and convection coefficients. Engine heat fluxes and component temperatures can subsequently be predicted from specification of general engine dimensions, materials, and operating conditions. Emphasis has been placed on minimizing the number of model inputs and keeping them as simple as possible to make the model practical and useful as an early design tool. The success of the global model depends on properly scaling the general engine inputs to accurately model engine heat flow paths across families of engine designs. The development and validation of suitable, scalable submodels is described in detail in this paper.

Expansion work recovery by two-phase ejector is known to be beneficial to vapor compression cycle performance. However, one of the biggest challenges with ejector vapor compression cycles is that the ejector cycle performance is sensitive to working condition changes which are common in automotive applications. Different working conditions require different ejector geometries to achieve maximum performance. Slightly different geometries may result in substantially different COPs under the same conditions. The ejector motive nozzle throat diameter (motive nozzle restrictiveness) is one of the key parameters that can significantly affect ejector cycle COP. This paper presents a new two-phase nozzle restrictiveness control mechanism which is possibly applicable to two-phase ejectors used in vapor compression cycles.

Compared to conventional injection techniques, Gasoline Direct Injection (GDI) has a lot of advantages such as increased fuel efficiency, high power output and low emission levels, which can be more accurately controlled. Therefore, this technique is an important topic of today's injection system research. Although the operating conditions of GDI injectors are simpler from a numerical point of view because of smaller Reynolds and Weber numbers compared to Diesel injection systems, accurate simulations of the breakup in the vicinity of the nozzle are very challenging. Combined with the complications of experimental techniques that could be applied inside the nozzle and at the nozzle exit, this is the reason for the lack of understanding the primary breakup behavior of current GDI injectors.

With the development of advanced ABE fermentation technology, the volumetric percentage of acetone, butanol and ethanol in the bio-solvents can be precisely controlled. To seek for an optimized volumetric ratio for ABE-diesel blends, the previous work in our team has experimentally investigated and analyzed the combustion features of ABE-diesel blends with different volumetric ratio (A: B: E: 6:3:1; 3:6:1; 0:10:0, vol. %) in a constant volume chamber. It was found that an increased amount of acetone would lead to a significant advancement of combustion phasing whereas butanol would compensate the advancing effect. Both spray dynamic and chemistry reaction dynamic are of great importance in explaining the unique combustion characteristic of ABE-diesel blend. In this study, a semi-detailed chemical mechanism is constructed and used to model ABE-diesel spray combustion in a constant volume chamber.

Local nonlinearities can affect the global dynamics of their linear host structures. In the context of fixed-wing aircraft, failure of store mounting can result in strong local nonlinearities. In this work, we experimentally mimic store mounting failure conditions in a model airplane subject to harmonic excitation. Two identical stores are mounted under the wings and are placed symmetrically opposite each other. The configuration where both stores are “locked”, i.e., mounting is very stiff, serves as the baseline linear system. The second configuration involves unlocking one of the stores, enabling a geometrically nonlinear flexure connection between the unlocked store and the wing. The flexure lets the store interact with the first flexible mode of the airplane, resulting in large relative displacements between the store and wing. In addition, the configuration allows for vibro-impacts between the wing and store.

Expansion work recovery by two-phase ejector is known to be beneficial to vapor compression cycle performance. However, one of the biggest challenges with ejector vapor compression cycles is that the ejector cycle performance is sensitive to working condition changes which are common in automotive applications. Different working conditions require different ejector geometries to achieve maximum performance. Slightly different geometries may result in substantially different COPs under the same conditions. The ejector motive nozzle throat diameter (motive nozzle restrictiveness) is one of the key parameters that can significantly affect ejector cycle COP. This paper presents the experimental results of the application of a new two-phase nozzle restrictiveness control mechanism to an automotive transcritical R744 ejector cycle.

In the new combustion strategies such as RCCI and dual-fuel combustion, the diesel pilot injection plays a pivotal role as it determines the ignition characteristics of the mixture and ultimately the combustion and emission performance. In this regard, equivalence ratio distribution resulted from the pilot injection becomes very important. In this work, computation study is carried out using KIVA-3V to simulate the engine compression stroke from intake valve close (IVC) to close to TDC so as to investigate the impact of piston geometry, injection start timing and flow initialization on the equivalence ratio distribution from a pilot injection in HSDI engine.

Ejector as a work recovery device offers potential for developing energy efficient heating and cooling systems based on vapor compression technology. For applications like automobile air conditioning, the operating conditions vary significantly which can lead to considerable performance degradation when the system is operated in off-design conditions. Therefore, system designing warrants development of accurate ejector performance models for a wide range of operating conditions. In this paper, a novel methodology for ejector performance maps is proposed using ejector efficiency as performance parameter and volumetric entrainment ratio as characterization parameter. The proposed performance map is developed after conducting experiments to find appropriate performance representation where ejector driven flow can be characterized using ejector motive flow. The developed performance map can predict ejector pressure lift within an accuracy of 20% using an iterative solver.

Due to the increasing consumption of fossil fuels, alternative fuels in internal combustion engines have attracted a lot of attention in recent years. Ethanol is the most common alternative fuel used in spark ignition (SI) engines due to its advantages of biodegradability, positively impacting emissions reduction as well as octane number improvement. Meanwhile, acetone is well-known as one of the industrial waste solvents for synthetic fibers and most plastic materials. In comparison to ethanol, acetone has a number of more desirable properties for being a viable alternative fuel such as its higher energy density, heating value and volatility.

This paper presents the experimentally obtained performance characteristics of an air conditioning-heat pump system that uses heat exchangers from a commercially available Nissan Leaf EV. It was found that refrigerant charge needed for cooling operation was larger than that for heating function with the test setup. The effects of: a). indoor air flow rate, b). outdoor air flow rate, and c). compressor speed on heating capacity and energy efficiency were explored and presented. Appropriate opening size of expansion valve that controlled subcooling for better energy efficiency was discussed and results were presented. Expansion valve opening size also strongly affected charge migration. Warm-up tests at different ambient conditions showed the necessity of a secondary heater to be reserved for very low ambient temperature.

To face the challenges of fossil fuel shortage and air pollution problems, there is growing interest in the potential usage of alternative fuels such as bio-ethanol and bio-butanol in internal combustion engines. The literature shows that the acetone in the Acetone-Butanol-Ethanol (ABE) blends plays an important part in improving the combustion performance and emissions, owing to its higher volatility. In order to study the effects of acetone addition into commercial gasoline, this study focuses on the differences in combustion, performance and emission characteristics of a port-injection spark-ignition engine fueled with pure gasoline (G100), ethanol-containing gasoline (E30) and acetone-ethanol-gasoline blends (AE30 at A:E volumetric ratio of 3:1). The tests were conducted at 1200RPM with the default calibration (for gasoline), at 3 bar and 5 bar BMEP under various equivalence ratios.

This paper develops a model for a parallel microchannel evaporator that incorporates quality variation at the tube inlets and variable mass flow rates among tubes. The flow distribution is based on the equal pressure drop along each flow path containing headers and tubes. The prediction of pressure drop, cooling capacity, and exit superheat strongly agree with 48 different experimental results obtained in four configurations using R134a. Predicted temperature profiles are very close to infrared images of actual evaporator surface. When compared to the uniform distribution model (that assumes uniform distribution of refrigerant mass flow rate and quality) results from the new model indicate superior prediction of cooling capacity, and exit superheat. Model results indicate maldistribution of refrigerant mass flow rate among the parallel tubes, caused primarily by pressure drop in the outlet header.

A single-cylinder, 4-1/2 in. by 5-1/2 in. diesel engine was modified to direct injection. It was supercharged, simulating turbocharging with aftercooling to 89.6 in. Hg absolute manifold pressure and 200 F manifold air temperature. The maximum bmep was 302 psi at 2400 rpm, which gave an output of 0.915 bhp/cu in. of piston displacement. In order to achieve 1 hp/cu in., a manifold pressure of 98.5 in. Hg absolute would be required at 2400 rpm. The economy was found to improve with high supercharging. The maximum gas pressure encountered was 2700 psi. This could be moderated by changing either the combustion system or the compression ratio. Changing the compression ratio affected the brake specific fuel consumption only slightly.

Air source heat pumps as the heating system for full electric vehicles are drawing more and more attention in recent years. Despite the high energy efficiency, frost accumulation on the heat pump evaporator is one of the major challenges associated with air source heat pumps. The evaporator needs to be actively defrosted periodically and heat pump heating will be interrupted during defrosting process. Proper defrost control is needed to obtain high average heat pump energy efficiency. In this paper, a new method for generating air source heat pump defrost control policy using reinforcement learning is introduced. This model-free method has several advantages. It can automatically generate optimal defrost control policy instead of requiring manually determination of the control policy parameters and logics.

A significant fraction of hydrocarbon (HC) emissions occurs during the cold-start phase of an engine's operating cycle. Fuel drop sizes in the cylinder and impingement of fuel on the cylinder wall are two factors which can affect the HC emissions during this period. Therefore, measurements of in-cylinder drop sizes and wall fuel impingement were made on a steady flow bench at flow rates and manifold vacuum conditions which simulated desired engine operating conditions. Experimental variables included three injector types, two cylinder head geometries, three valve lifts, and two simulated engine speeds. Injector performance was assessed prior to the flow bench studies. Fuel injector performance was found to affect in-cylinder drop size and wall fuel impingement. The dual-jet injector produced two liquid streams which were not atomized into drops at a distance of 10 cm (a typical injector to valve distance) from the injector tip.

Expansion work recovery by two-phase ejector is known to be beneficial to vapor compression cycle performance. However, one of the biggest challenges with ejector vapor compression cycle is that the ejector cycle performance is sensitive to working condition changes which are common in many applications, including automotive AC systems. Different working conditions require different ejector geometries to achieve maximum performance. Slightly different geometries may result in substantially different COPs under the same conditions. Ejector motive nozzle throat diameter (motive nozzle restrictiveness) is one of the key parameters that can significantly affect COP. This paper presents the experimental investigation of a new motive nozzle restrictiveness control mechanism for two-phase ejectors used in vapor compression cycles, which has the advantages of being simple, potentially less costly and less vulnerable to clogging.

This paper presents an experimental study of lubricant effect on the performance of microchannel evaporators in a typical MAC system. R134a is used as the refrigerant with PAG46 lubricant. The increase of oil circulation rate elevates the pressure drop of the evaporator. The specific enthalpy change in evaporator decreases with increasing oil circulation rate, while refrigerant distribution appears to be more uniform as indicated by infrared images of the evaporator surface temperatures. Thus mass flow rate increases.

Lubricant in compressor usually flows out with refrigerant. Thus, it is evitable for lubricant to be present in the heat exchanger, which significantly affects the heat exchanger performance. This paper is to investigate the effects of PAG oil on R134a distribution in the microchannel heat exchanger (MCHX) with vertical headers and to provide a tool to model R134a (with oil) distribution and its effects on MCHX capacity. The flow configuration in MCHX under the heat pump mode of the reversible system is mimicked in the experimental facility: refrigerant-oil mixture is fed into the test header from the bottom pass and exits through the top pass. It is found that a small amount of oil (OCR=0.5%) worsen the distribution. But further increasing OCR to 2.5% and 4.7%, the distribution becomes better.

Inlet valve deposits in gasoline engines have a significant effect on engine operation with particular reference to cold starting and driveability. Present methods of quantifying these deposits by weighing them or rating them with the aid of a visual rating scale are recognized as not being reliable indices of the detrimental effect of these deposits. A valve deposit quantification system was developed that relied on the use of machine vision. Algorithms were formulated to track the silhouetted edge profile of a backlit valve from which a valve volume was determined. The valve deposit volume was calculated as the difference in volume between the valve in its clean and coked states. The system was able to detect a minimum coke deposit level of 0.06g at the 95% confidence limit, the accuracy being based on the correlation between the volume as determined by the vision system and the mass of the deposit.

This paper describes the University of Illinois machining system research program. This program focuses on the development of mechanistic models for machining process simulation and the use of these models for the simultaneous engineering of products and processes. Models are presented for end milling, face milling, and cylinder boring which take into account the cutting conditions, tool geometry, workpiece geometry, and system element dynamics. Furthermore, these models explicitly recognize the presence of machining process noise factors such as cutter runout and tool wear. Representative applications for these models are given. A methodology is described for the simultaneous engineering of products and manufacturing processes which incorporates models for the unit manufacturing processes, the manufacturing system, and the product to be produced.