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Component sound quality is an important factor in the design of competitive diesel engines. One component noise that causes complaints is the gear rattle that originates in the front-of-engine gear train which drives the fuel pump and other accessories. The rattle is caused by repeated tooth impacts resulting from fluctuations in differential torsional acceleration of the driving gears. These impacts generate a broadband, impulsive noise that is often perceived as annoying. In most previous work, the overall sound quality of diesel engines has been considered without specifically focusing on predicting the perception of gear rattle. Gear rattle level has been quantified based on angular acceleration measurements, but those measurements can be difficult to perform. Here, the emphasis was on developing a metric based on subjective testing of the perception of gear rattle.

An experiment has been developed to investigate the ignition characteristics of ultra-lean premixed H2/air mixtures by a supersonic hot jet. The hot jet is generated by combustion of a stoichiometric mixture in a small prechamber. The apparatus adopted a dual-chamber design in which a small-volume (1% of the main chamber by volume) prechamber was installed within a large-volume main chamber. A small orifice (nozzle) connects the two chambers. Spark initiated combustion inside the prechamber causes a pressure rise and pushes the gases though the nozzle, resulting in a hot jet that would ignite the lean mixture in the main chamber. Simultaneous high-speed Schlieren photography and OH* Chemiluminescence were applied to visualize the jet penetration and the ignition processes inside the main chamber. Hot Wire Pyrometry (HWP) was used to measure temperature distribution of the transient hot jet.

The most common and lethal weapons against military vehicles are the improvised explosive devices (IEDs). In an explosion, critical cabin’s penetrations and high accelerations can cause serious injuries and death of military personnel. This investigation uses single and multi-fidelity Bayesian optimization (BO) to design sandwich composite armors for blast mitigation. BO is an efficient methodology to solve optimization problems that involve black-box functions. The black-box function of this work is the finite element (FE) simulation of the armor subjected to blast. The main two components of BO are the surrogate model of the black-box function and the acquisition function that guides the optimization. In this investigation, the surrogate models are Gaussian Process (GP) regression models and the acquisition function is the multi-objective expected improvement (MEI) function. Information from low and high fidelity FE models is used to train the GP surrogates.

Nowadays, the increasing number of structural high pressure die casting (HPDC) aluminum parts need to be joined with high strength steel (HSS) parts in order to reduce the weight of vehicle for fuel-economy considerations. Self-Pierce Riveting (SPR) has become one of the strongest mechanical joining solutions used in automotive industry in the past several decades. Joining HPDC parts with HSS parts can potentially cause joint quality issues, such as joint button cracks, low corrosion resistance and low joint strength. The appropriate heat treatment will be suggested to improve SPR joint quality in terms of cracks reduction. But the heat treatment can also result in the blister issue and extra time and cost consumption for HPDC parts. The relationship between the microstructure of HPDC material before and after heat treatment with the joint quality is going to be investigated and discussed for interpretation of cracks initiation and propagation during riveting.

Deep-hole drilling is among the most critical precision machining processes for production of high-performance discrete components. The effects of drilling with superimposed, controlled low-frequency modulation - Modulation-Assisted Machining (MAM) - on the surface textures created in deep-hole drilling (ie, gun-drilling) are discussed. In MAM, the oscillation of the drill tool creates unique surface textures by altering the burnishing action typical in conventional drilling. The effects of modulation frequency and amplitude are investigated using a modulation device for single-flute gun-drilling on a computer-controlled lathe. The experimental results for the gun-drilling of titanium alloy with modulation are compared and contrasted with conventional gun-drilling. The chip morphology and surface textures are characterized over a range of modulation conditions, and a model for predicting the surface texture is presented. Implications for production gun-drilling are discussed.

This paper presents a simulation model for the analysis of internal gear ring pumps. The model follows a multi domain simulation approach comprising sub-models for parametric geometry generation, fluid dynamic simulation, numerical calculation of characteristic geometry data and CAD/FEM integration. The sub-models are interacting in different domains and relevant design and simulation parameters are accessible in a central, easy to handle graphical user interface. The potentials of the described tool are represented by simulation results for both steady state and transient pump operating conditions and by their correlation with measured data. Although the presented approach is suitable to all applications of gear ring pumps, a particular focus is given to hydraulic actuation systems used in automotive drivetrain applications.

Excessive vibration and poor controllability occur in many mobile fluid power applications, with negative consequences as concerns operators' health and comfort as well as machine safety and productivity. This paper addresses the problem of reducing oscillations in fluid power machines presenting a novel control technique of general applicability. Strong nonlinearities of hydraulic systems and the unpredictable operating conditions of the specific application (e.g. uneven ground, varying loads, etc.) are the main challenges to the development of satisfactory general vibration damping methods. The state of the art methods are typically designed as a function of the specific application, and in many cases they introduce energy dissipation and/or system slowdown. This paper contributes to this research by introducing an energy efficient active damping method based on feedback signals from pressure sensors mounted on the flow control valve block.

The four-microphone standing wave tube system has proven useful for measuring the absorption and transmission loss of various fibrous and non-fibrous absorbers. The system is fast, repeatable, accurate and compact. This paper discusses the advantages of the four-microphone system for measuring the transmission loss in lateral-flow absorber systems. The original four-microphone round impedance tube system and the migration to a four-microphone square tube system are discussed. The four-microphone square tube system allows effective study of filled and partially filled cavities.

Notched spoilers may be used to suppress flow-induced cavity resonance in vehicles with open sunroofs or side windows. The notches are believed to generate streamwise vortices that break down the structure of the leading edge cross-stream vortices predominantly responsible for the cavity excitation. The objectives of the present study were to gain a better understanding of the buffeting suppression mechanisms associated with notched spoilers, and to gather data for computational model verification. To this end, experiments were performed to characterize the surface pressure field downstream of straight and notched spoilers mounted on a rigid wall to observe the effects of the notches on the static and dynamic wall pressure. Detailed flow velocity measurements were made using hot-wire anemometry. The results indicated that the presence of notches on the spoiler reduces drag, and thus tends to move the flow reattachment location closer to the spoiler.

The new devices and missions to achieve the aims of NASA's Science Mission Directorate (SMD) are creating increasingly demanding thermal environments and applications. In particular, the low conductance of metal-to-metal interfaces used in the thermal switches lengthen the cool-down phase and resource usage for spacecraft instruments. During this work, we developed and tested a vacuum-compatible, durable, heat-conduction interface that employs carbon nanotube (CNT) arrays directly anchored on the mating metal surfaces via microwave plasma-enhanced, chemical vapor deposition (PECVD). We demonstrated that CNT-based thermal interface materials have the potential to exceed the performance of currently available options for thermal switches and other applications.

There has always been, from the very first UAV, a need for providing cost-effective methods of deploying unmanned aircraft systems at high altitudes. Missions for UAVs at high altitudes are used to conduct atmospheric research, perform global mapping missions, collect remote sensing data, and establish long range communications networks. The team of Gevers Aircraft, Technology Management Group, and Purdue University have designed an innovative balloon launched UAV for these near space applications. A UAV (Payload Return Vehicle) with a nested morphing wing was designed in order to meet the challenges of high altitude flight, and long range and endurance without the need for descent rate control with rockets or a feathering mode.

Helmholtz resonator has been used in industry for a long time to reduce the noise from exhaust system in vehicle or machinery. Numerous investigations have been done in the past to study the effect of a Helmholtz resonator connected to a pipeline. A general procedure for the analysis of curved or flat, thin two dimensional gas cavities such as thin compressor or engine manifolds or so-called thin shell type muffler elements, which can efficiently utilize the limited space of hermetically sealed compressors or small engine compartments, has been developed by the authors, as long as the thickness of the cavities is substantially small compared to the shortest wavelength of interest. However, to the authors' knowledge, a Helmholtz resonator attached to a rectangular thin muffler element, which is similar to a refrigeration compressor muffler, has not been analyzed.

This paper presents in-process monitoring and control based on a novel ultrasonic sensing technique. The developed ultrasonic system provides non-contact measurement of surface roughness, which is applicable to wet machining environments. The utility and robustness of the technique are demonstrated through applications to different processes and materials. In-process surface roughness monitoring capability of the system is also shown along with its potential to monitor flank wear conditions. The result of in-process surface roughness control implementation based on the developed technique shows the control scheme is able to maintain consistent surface roughness values regardless of the tool wear state.

Numerical computations of combusting transient jets are performed under diesel-like conditions. Discussions of the structure of such jets are presented from global and detailed points of view. From a global point of view, we show that the computed flame heights agree with deductions from theory and that integrated soot mass and heat release rates are consistent with expected trends. We present results of several paramaters which characterise the details of the jet structure. These are fuel mass fractions, temperature, heat release rates, soot and NO. Some of these parameters are compared with the structure of a combusting diesel spray as deduced from measurements and reported in the literature. The heat release rate contours show that the region of chemical reactions is confined to a thin sheet as expected for a diffusion flame. The soot contour plots appear to agree qualitatively with the experimental observations.

The method of multiple reference frames is employed in the development of a state variable model for brushless DC drives with non-sinusoidal back emf waveforms. This model has the desirable features of being valid for transient and steady-state analysis as well as having state variables that are constant in the steady-state. The model facilitates both nonlinear and linear system analysis and control design. Computer simulation and experimental data are included to validate the analysis.

A low-cost hydrostatic absorption dynamometer has been developed for small to medium sized engines. The dynamometer was designed and built by students to support student projects and educational activities. The availability of such a dynamometer permits engine break-in cycles, performance testing, and laboratory instruction in the areas of engines, fuels, sensors, and data acquisition. The dynamometer, capable of loading engines up to 60kW at 155Nm and 3600rpm, incorporates a two-section gear pump and an electronically operated proportional pressure control valve to develop and control the load. A bypass valve permits the use of only one pump section, allowing increased fidelity of load control at lower torque levels. Torque is measured directly on the drive shaft with a strain gage. Torque and speed signals are transmitted by an inductively-powered collar mounted to the dynamometer drive shaft. Pressure transducers at the pump inlet and pump outlet allow secondary load measurement.

This paper presents hydraulic topographies using a network of valves to achieve better energy efficiency, reliability, and performance. The Topography with Integrated Energy Recovery (TIER) system allows the valves and actuators to reconfigure so that flow from assistive loads on actuators can be used to move actuators with resistive loads. Many variations are possible, including using multiple valves with either a single pump/motor or with multiple pump/motors. When multiple pump/motors are used, units of different displacements can be chosen such that units are controlled to minimize time operating at low displacement, thus increasing overall system efficiency. Other variations include configurations allowing open loop or closed loop pump/motors to be used, the use of fixed displacement pump/motors, or the ability to store energy in an accumulator. This paper gives a system level overview and summarizes the hydraulic systems using the TIER approach.

This paper describes the numerical modeling of the hydraulic circuit of a self-moving boom lift. Boom lifts consist of several hydraulic actuators, each of them performs a specific movement. Hydraulic systems for lifting applications must ensure consistent performance no matter what the load and how many users are in operation at the same time. Common solutions comprise a fixed or a variable displacement pump with load-sensing control strategy. Instead, the hydraulic circuit studied in this paper includes a fixed displacement pump and an innovative (patented) proportional valve assembly. Each proportional valve (one for each user) permits a flow regulation for all typical load conditions and movement simultaneously. The study of the hydraulic system required a detailed modeling of some components such as: the overcenter valves, for the control of the assistive loads; the proportional valve, which keeps a constant flow independently of pressure drop across itself.

In this paper, a wall-modified interactive flamelet model is developed for improving the modeling of Diesel combustion. The objective is to include the effects of wall heat loss on the transient flame structure. The essential idea is to compute several flamelets with several representative enthalpy defects which account for wall heat loss. Then, the averaged flamelet profile can be obtained through a linear fit between the flamelets according to the enthalpy defect of the local gas which results from the wall heat loss. The enthalpy defect is estimated as the difference between the enthalpy in a flamelet without wall heat loss, which would correspond to the enthalpy in the gas without wall heat loss, and the gas with wall heat loss. The improved model is applied to model combustion in a Diesel engine. In the application, two flamelets, one without wall heat loss and one with wall heat loss, are considered.

Experimental modal analysis (EMA) provides many parameters that are required in numerical modeling of dynamic and vibratory behavior of structures. This paper discusses EMA on an exhaust system of an off-road car. The exhaust structure is tested under three boundary conditions: free-free, supported with two elastomeric mounts, and mounted to the car. The free-free modal parameters are compared to finite element results. The two-mount tests are done with the mounts fixed to a rigid and heavy frame. The rigidity of the frame is verified experimentally. The on-car test is done with realistic boundary conditions, where the exhaust structure is fixed to the engine manifold as well as the two elastomeric mounts. The two-mount and the on-car tests result in highly complex mode shapes.