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In the air conditioning system, flow-induced noise is very disturbing, including the noise generated in the expansion device and the heat exchangers. In the past few decades, most researches related to flow-induced noise focused on the relationship between the flow regimes near the expansion device and the amplitude of flow-induced noise when the measurements are not synched. In this paper, an experimental approach is used to explore the simultaneous relationships between flow-induced noise characteristics and flow regimes at the inlet of TXV of evaporators used in automobiles. A pumped R134a loop with microphones and transparent visualization sections is used to simulate the vapor compression system. Also, the paper evaluates the severity of flow-induced noise from not only the amplitude of noise but also the frequency of noise with a parameter called psychoacoustic annoyance (PA).

This article presents basic separation mechanisms with coalescing/impinging separators studied as the add-on to current popular centrifugal designs. The coalescence and impingement of oil on wire mesh and wave-plates are visualized and tested to investigate the impact of geometry and flow conditions on oil separation efficiency. Re-entrainment phenomenon is explained based on the mass balance. Oil mist flow at the swashplate reciprocating compressor discharge is quantified by video processing method to provide detailed information of the oil droplets. The physics behind oil separator is illustrated by visualization and measurement in this study, which gives useful guidelines for oil separator design and operation. The flow visualization shows the details of oil passing through different oil separation structures. Videos are quantified to provide information like droplet size distribution and liquid volume fraction.

Carbon dioxide (CO2 or R744) is a promising next-generation refrigerant for mobile air-conditioning applications (MAC), which has the advantages of good heating performance in cold climates and environmental-friendly properties. This paper presents a simulation model of an integrated internal heat exchanger (IHX) and accumulator (Acc) using the finite volume method. The results are validated by a group of experimental data collected with different transcritical R744 mobile air-conditioner and heat pump (MHP) systems, and the error was within ±10%. The impacts of refrigerant mass flow rate and operating temperatures on the heat transfer rate of the IHX, improvement on refrigeration capacity and the liquid level in the Acc were studied. Results show that the net benefits of IHX are significant in AC mode, while it helps preventing flooding of the compressor in MHP mode.

High costs and extreme risks prevent the life testing of NASA hardware. These unavoidable limitations prevent the determination of sound reliability bounds for NASA hardware; thus the true risk assumed in future missions is unclear. A simulation infrastructure for determining these risks is developed in a configurable format here. Positive preliminary results in preparation for validation testing are reported. A stochastic filter simulates non-deterministic output from the various unit processes. A maintenance and repair module has been implemented with several levels of complexity. Two life testing approaches have been proposed for use in future model validation.

BioSim is a simulation tool which captures many basic life support functions in an integrated simulation. Conventional analyses can not efficiently consider all possible life support system configurations. Heuristic approaches are a possible alternative. In an effort to demonstrate efficacy, a validating experiment was designed to compare the configurational optima discovered by heuristic approaches and an analytical approach. Thus far, it is clear that a genetic algorithm finds reasonable optima, although an improved fitness function is required. Further, despite a tight analytical fit to data, optimization produces disparate results which will require further validation.

Camless actuation offers programmable flexibility in controlling engine valve events. However, a full range of engine benefits will only be available, if the actuation system can control lift profile characteristics within a particular lift event. Control of the peak value of valve lift is a first step in controlling the profile. The paper presents an adaptive feedback control of valve lift for a springless electrohydraulic valvetrain. The adaptive control maintains peak value of lift in presence of variations in engine speed, hydraulic fluid temperature and manufacturing variability of valve assemblies. The control design includes a reduced-order model of the system dynamics. Experimental results show dynamic behavior under various operating and environmental conditions and demonstrate advantages of adaptive control over the non-adaptive type.

A reconfigurable control system is an intelligent control system that detects faults within the system and adjusts its performance automatically to avoid mission failure, save lives, and reduce system maintenance costs. The concept was first successfully demonstrated by NASA between December 1989 and March 1990 on the F-15 flight control system (SRFCS), where software was integrated into the aircraft's digital flight control system to compensate for component loss by reconfiguring the remaining control loop. This was later adopted in the Boeing X-33. Other applications include modular robotics, reconfigurable computing structure, and reconfigurable helicopters. The motivation of this work is to test such control system designs for future long term space missions, more explicitly, the automation of life support systems.

This paper describes a ‘toolbox’ for modeling liquid cooling system networks within vehicle thermal management systems. Components which can be represented include pumps, coolant lines, control valves, heat sources and heat sinks, liquid-to-air and liquid-to-refrigerant heat exchangers, and expansion tanks. Network definition is accomplished through a graphical user interface, allowing system architecture to be easily modified. The elements of the toolbox are physically based, so that the models can be applied before hardware is procured. The component library was coded directly into MATLAB / SIMULINK and is intended for control system development, hardware-in-the-loop (HIL) simulation, and as a system emulator for on-board diagnostics and controls purposes. For HIL simulation and on-board diagnostics and controls, it is imperative that the model run in real-time.

This paper presents a mapping of developing adiabatic two-phase R134a flow directly after the expansion valve until the flow is “fully developed” in a 15.3mm inner diameter pipe. Flow characteristics of separation distance, flow type in the homogenous region, void fraction as a function of tube length, and fully developed flow region void fraction and regime were quantified and described.

Environmental control and life support systems are usually associated with high demands for performance robustness and cost efficiency. However, considering the complexity of such systems, determining the balance between those two design factors is nontrivial for even the simplest space missions. Redundant design is considered as a design optimization dilemma since it usually means higher system reliability as well as system cost. Two coupled fundamental questions need to be answered. First, to achieve certain level of system reliability, what is the corresponding system cost? Secondly, given a budget to improve system reliability, what is the most efficient design for component or subsystem redundancy? The proposed analysis will continue from previous work performed on series systems by expanding the scope of the analysis and testing parallel systems. Namely, the online and offline redundancy designs for a Lunar Outpost Mission are under consideration.

The purpose this paper is to delineate why there exists a trade-off between biomechanical realism and algorithmic efficiency for human motion simulation models, and to illustrate how empirical human movement data and findings can be integrated with novel modeling techniques to overcome such a realism-efficiency tradeoff. We first review three major classes of biomechanical models for human motion simulation. The review of these models is woven together by a common fundamental problem of redundancy—kinematic and/or muscle redundancy. We describe how this problem is resolved in each class of models, and unveil how the trade-off arises, that is, how the computational demand associated with solving the problem is amplified as a model evolves from small scale to large scale, or from less realism to more realism.

Aircraft incidents and accidents in icing are often the result of degradation in performance and control. However, current ice sensors measure the amount of ice and not the effect on performance and control. No processed aircraft performance degradation information is available to the pilot. In this paper research is reported on a system to estimate aircraft performance and control changes due to ice, then use this information to automatically operate ice protection systems, provide aircraft envelope protection and, if icing is severe, adapt the flight controls. Key to such a safety system would be he proper communication to, and coordination with, the flight crew. This paper reviews the basic system concept, as well as the research conducted in three critical areas; aerodynamics and flight mechanics, aircraft control and identification, and human factors.

The detailed mechanisms by which oxygenated diesel fuels reduce engine-out soot emissions are not well understood. The literature contains conflicting results as to whether a fuel's overall oxygen content is the only important parameter in determining its soot-reduction potential, or if oxygenate molecular structure or other variables also play significant roles. To begin to resolve this controversy, experiments were conducted at a 1200-rpm, moderate-load operating condition using a modern-technology, 4-stroke, heavy-duty DI diesel engine with optical access. Images of broadband natural luminosity (i.e., light emission without spectral filtering) from the combustion chamber, coupled with heat-release and efficiency analyses, are presented for three test-fuels. One test-fuel (denoted GE80) was oxygenated with tri-propylene glycol methyl ether; the second (denoted BM88) was oxygenated with di-butyl maleate. The overall oxygen contents of these two fuels were matched at 26% by weight.

This paper presents the study of refrigerant charge imbalance between A/C (cooling) mode and HP (heating) mode of a mobile reversible system. Sensitivities of cooling and heating capacity and energy efficiency with respect to refrigerant charge were investigated. Optimum refrigerant charge level for A/C mode was found to be larger than that for HP mode, primarily due to larger condenser size in A/C mode. Refrigerant charge retention in components at both modes were measured in the lab by quick close valve method. Modeling of charge retention in heat exchangers was compared to experimental measurements. Effect of charge imbalance on oil circulation was also discussed.

With market share of electric vehicles continue to grow, there is an increasing demand of mobile heat pump for cabin climate control, as it has much higher energy efficiency when compared to electric heating and helps to cut drive range reduction. One big challenge of heat pump systems is that their heating capacities drop significantly when operating at very low ambient temperature, especially for those with low pressure refrigerants. This paper presents a way to improve low ambient temperature heating performance by using intermediate vapor bypass with the outdoor heat exchanger, which works as an evaporator in heat pump mode. The experimental results show a 35% increase of heating capacity at −20 °C ambient with the improved system as compared to the baseline, and heating performance factor also slightly increased when the system is working at higher ambient temperature to reach the same heating capacity as the baseline.

Ignition location is one of the important factors that affect the thermal efficiency, exhaust emissions and knock sensitivity in premixed-charge ignition engines. However, the ignition initiation locations of pre-chamber generated turbulent jet ignition, which is a promising ignition enhancement method, are not clearly understood due to the complex physics behind it. Motivated by this, the ignition initiation location of a transient turbulent jet in a constant volume combustor is analyzed by the use of computational fluid dynamics (CFD) simulations. In the CFD simulations of this work, commercial codes KIVA-3 V release 2 and an in-house-developed chemical solver with a detailed mechanism for H2/air mixtures are used. Comparisons are performed between simulated and experimental ignition initiation locations, and they agree well with one another. A detailed parametric study of the influence of in-cylinder temperature on the ignition initiation location is also performed.

A prediction model for hand prehensile movements was developed and validated. The model is based on a new approach that blends forward dynamics and a simple parametric control scheme. In the development phase, model parameters were first estimated using a set of hand grasping movement data, and then statistically analyzed. In the validation phase, the model was applied to novel conditions created by varying the subject group and size of the object grasped. The model performance was evaluated by the prediction errors under various novel conditions as compared to the benchmark values with no extrapolation. Analyses of the model parameters led to insights into human movement production and control. The resulting model also offers computational simplicity and efficiency, a much desired attribute for digital applications.

Cylinder head combustion chamber and piston temperatures and heat fluxes were measured in a 2.2 L 4 cylinder spark ignition engine. Measurements for the combustion chamber were made at wide open throttle conditions, 1400 rpm to 5000 rpm at 600 rpm increments, additional measurements were made on the combustion chamber at part throttle conditions at 3200 RPM. Piston temperature and heat flux measurements were made at WOT conditions from 1400 to 3200 RPM in 600 RPM increments. Average combustion chamber surface temperatures ranged from 130 deg. C to 248 deg. C, while peak combustion chamber surface temperatures ranged from 142 deg. C to 258 deg. C for WOT conditions. Peak heat flus at the surface for WOT conditions in the combustion chamber ranged from 1.2 MW/m2to 5.0 MW/m2. Central region heat fluxes were 2.3 to 2.8 times greater than those in the end gas regions of the combustion chamber.

Neural networks are massively parallel computational models for knowledge representation and information processing. The capabilities of neural networks, namely learning, noise tolerance, adaptivity, and parallel structure make them good candidates for application to a wide range of engineering problems including diagnostics problems. The general approach in developing neural network based diagnostic methods is described through a case study. The development of an acoustic wayside train inspection system using neural networks is described. The study is aimed at developing a neural network based method for detection defective wheels from acoustic measurements. The actual signals recorded when a train passes a wayside station are used to develop a neural network based wheel defect detector and to study its performance. Signal averaging and scoring techniques are developed to improve the performance of the constructed neural inspection system.

Air flow through the passages of a Chrysler LH platform ventilated brake rotor is measured. Modifications to the production rotor's vent inlet geometry are prototyped and measured in addition to the production rotor. Vent passage air flow is compared to existing correlations. The inlet modifications show significantly improved vent air flow, over the production rotor. The result improvement in heat transfer and rotor cooling is reported. These benefits in performance should be attainable at very low increases in production cost.