Pump Pressure Control in Hydraulic Systems - Modeling and Simulation of Dynamic Behavior

<div class="htmlview paragraph">In February of 1987, Dresser introduced a pair of new mechanical drive, off-highway trucks designed to operate in the 35 to 60 ton, rear-dump, classes. These trucks, designated 140M and 210M, replaced three previous models while covering the same payload range. One distinctive feature of these new vehicles was their hydraulic system and in particular the brake control portion of this system.</div> <div class="htmlview paragraph">This new hydraulic brake control system can be described as a closed-center arrangement using a pressure-compensated, variable displacement pump as an energy source with accumulator-based energy reserves for independent and redundant circuits. In the basic version, a pair of pressure regulating valves are used to control system pressure at the brakes. These valves can be actuated in</div> <div class="htmlview paragraph"> <figure id="F1" class="figure"> <div class="graphic-wrapper"><img class="article-figure figure" src="911834_fig0001.jpg" alt="No Caption Available"/></div> </figure> </div> <div class="htmlview paragraph">tandem by a treadle (foot pedal) or separately by hydraulic pilot pressure. A single, filtered hydraulic fluid is used throughout the system and is stored in a single reservoir vented to atmosphere.</div> <div class="htmlview paragraph">The basic system is capable of accommodating multiple-axle (i.e. more than two) arrangements but was originally applied to a two-axle vehicle using dry, disc-type (caliper and rotor) brakes on all wheels. In February of 1990, the Model 140M and 210M trucks were revised to offer rear axle oil-cooled brakes as an option. The brake control system was subsequently modified to provide for this change primarily by the use of an additional pressure regulating valve and redundant circuitry.</div> <div class="htmlview paragraph">Both the original and latest versions of this system are characterized by their use of a unique emergency brake control system. Through the use of logic-type control valves, a loss of hydraulic pressure in one circuit is used to force the remaining high pressure circuits into actuating the brakes. This paper will describe the arrangement and operation of this hydraulic brake control system and its function as an integral part of the overall vehicle hydraulic system.</div>

Dynamic recrystallization (DRX) occurring during hot rolling significantly affects the microstructural evolution and final mechanical properties of steel. In this study, single hot compression tests are performed at temperatures between 1000 and 1300 °C with strain rates between 0.01 and 15 s−1 to investigate dynamic recrystallization behavior of a 15V38 steel. Critical strains for initiation of dynamic recrystallization and peak strains are identified through the analysis of work hardening rate from the measured stress–strain results. Dynamic recrystallization is identified by the softening in the flow stress during plastic deformation and quantified as the difference between a calculated dynamic recovery curve and the measured stress–strain curve. Dynamic recrystallization is modeled using calculated critical strain, peak strain, Zener‐Hollomon (Z) parameter, and volume fraction of dynamic recrystallization. Subroutines accounting for dynamic recrystallization are developed and implemented into a three‐dimensional finite element model for hot rolling of a round bar. Simulation results show that dynamic recrystallization is distributed throughout the bar and exhibits a positive relationship with equivalent plastic strain. Temperature effects on dynamic recrystallization are also investigated using different rolling temperatures, and results show that the fraction of dynamic recrystallization is significantly increased as rolling temperature increases.

<div class="section abstract"><div class="htmlview paragraph">In an automotive suspension, the shock absorber plays a significant role to enable the vehicle performances, especially in ride, handling and Noise-Vibration-Harshness (NVH). Understanding its physical characteristics is of great importance, as it has a main influence on the overall vehicle performance.</div><div class="htmlview paragraph">Within this research project simulation models for different passive monotube shock absorber systems have been created in a 1-D system simulation software. The simulation models are designed and parameterized physically.</div><div class="htmlview paragraph">To validate the simulation models measurements on different hydropulse-shaker with specially designed control signals to investigate the response during high frequency excitation, have been done. A detailed discussion of the several models and results of a simulation to measurement comparison is given. After detailed investigation the shock absorber simulation models are now adaptable to the multi body simulation.</div><div class="htmlview paragraph">As a result nearly equal experimental and simulated response of the different shocks was found. Some deviations are remaining during high frequency (>30Hz) operation of the damper. Dominant parameters to influence the damper response have been found. A sensitivity analysis shows the influences of these parameters. An analytical model to approach the shim stack stiffness was designed. For a validation detailed Finite-Element-Method (FEM) models of the shim stack have been developed and compared with load cases up to 100 bar hydraulic pressure. Additionally an FEM-model of the shock absorber and detailed modal analysis have been made to calculate and validate the natural frequencies of the shock. Limitations of this current study are the investigated monotube shock absorber systems, not including and including stroke-dependent-damping.</div><div class="htmlview paragraph">The presented novelty is the method of the configuration of the shock absorber simulation models only with geometric data. The shim stack models to calculate its stiffness instead of fatigue calculation are new as well. The new configuration approach increases the possibility to design automotive shock absorbers in advance of having a prototype. With the multi-body simulations of the chassis forecasts of the cars behaviour are possible at earlier stages during the development cycle. As OEM it is possible to simulate the behavior of the shock absorber in detailed car models.</div></div>

<div class="section abstract"> <div class="htmlview paragraph">This SAE Standard covers complete general and dimensional specifications for 37 degree flared and flareless types of hydraulic tube fittings and O-ring plugs. Also included are pipe fittings and adapter unions for use in conjunction with these tube fittings. These fittings are intended for general application in hydraulic systems on industrial equipment and commercial products.</div> <div class="htmlview paragraph">These fittings are capable of providing leak-proof, full-flow connections in hydraulic systems operating at working pressures as specified in SAE J1065, “Pressure Ratings for Hydraulic Tubing and Fittings.”</div> <div class="htmlview paragraph">Since many factors influence the pressure at which a hydraulic system will or will not perform satisfactorily, the values shown in SAE J1065 should not be construed as a guaranteed minimum.</div> <div class="htmlview paragraph">For any application, it is recommended that sufficient testing be conducted and reviewed by both the user and fitting manufacturer to assure that performance levels will be safe and satisfactory.</div> <div class="htmlview paragraph">The standard is divided into six sections as follows:</div> </div>

<div class="htmlview paragraph">The present work concerns the analysis of a concept for a new variable valve actuation system for internal combustion engines, denoted HVC (Hydraulic Valve Control system). The system is an electro-hydraulic device which aims at minimizing the power consumption required for the valve actuation. Unlike lost motion devices, where the excess pumped oil is wasted in order to control the lift profile, the HVC system uses a reduced quantity of energy to ensure the actual lift profile. For that reason interesting potentialities to increase the global fuel conversion efficiency of the engine are expected, in addition to the benefits deriving from the control flexibility.</div> <div class="htmlview paragraph">The HVC system has been modeled by means of an hydraulic simulation tool, useful for the dynamic analysis of mechanical and hydraulic systems. In this work the main elements of the device will be described and their relevant modeling parameters will be discussed. The model has been validated by means of experimental lift data obtained in a prototype test bench. In order to properly tune the numerical model various operating conditions have been concerned.</div> <div class="htmlview paragraph">The system shows a high flexibility in the control of the lift and timing. The predicted power consumption is very attractive. The main effects of the oil pressure and of the oil temperature are discussed.</div>

<div class="htmlview paragraph">Automatic transmissions require that the transition or shift quality between the various gears be smooth and uniform. Driveability is improved by optimizing the shift time of certain gear changes. An added benefit of improved shift quality is reduced clutch wear.</div> <div class="htmlview paragraph">During the investigation of an electronic transmission control system for agricultural, off highway and, heavy duty on highway vehicles, it became apparent that a key element in the hydraulic system was the need to accurately regulate oil pressure to the various clutches in the gear train.</div> <div class="htmlview paragraph">The valve described herein accurately regulates oil pressure at low levels and progressively increases pressure, with respect to time, by means of an electronically programmable pressure vs time control to any level up to supply pressure.</div>

<div class="htmlview paragraph">The use of closed center hydraulic systems on new U. S. agricultural tractors has increased significantly in recent years. Most of these tractors use variable delivery pumps, with either constant pressure or load sensitive systems.</div> <div class="htmlview paragraph">In its new Series 10 tractors, Ford Tractor chose to develop and produce a closed center hydraulic system using fixed displacement pumps. This system is both flexible and energy conserving. It also has many of the advantages of open center hydraulic systems and can utilize some of these components.</div>

<div class="section abstract"><div class="htmlview paragraph">High pressure EGR provides NO<sub>x</sub> emission reduction even at low exhaust temperatures. To maintain a safe EGR system operation over a required lifetime, the EGR cooler fouling must not exceed an allowable level, even if the engine is operated under worst-case conditions.</div><div class="htmlview paragraph">A reliable fouling simulation model represents a valuable tool in the engine development process, which validates operating and calibration strategies regarding fouling tendency, helping to avoid fouling issues in a late development phase close to series production.</div><div class="htmlview paragraph">Long-chained hydrocarbons in the exhaust gas essentially impact the fouling layer formation. Therefore, a simulation model requires reliable input data especially regarding mass flow of long-chained hydrocarbons transported into the cooler.</div><div class="htmlview paragraph">There is a huge number of different hydrocarbon species in the exhaust gas, but their individual concentration typically is very low, close to the detection limit of standard in-situ measurement equipment like GC-MS.</div><div class="htmlview paragraph">Therefore, a new measurement and analysis approach has been developed, where the exhaust gas is guided to a metal foam collector, in which HC`s are deposited. The probe is then analyzed in a suited thermogravimetrical system (TGA) in nitrogen atmosphere, temperature range 25°C to 650°C. Analyzing the TGA curve, HC concentration data for 6 different boiling temperature ranges are obtained, provided to an adapted 1-d fouling simulation model.</div><div class="htmlview paragraph">Using these data along with further input parameters like cooler geometry, gas temperature, pressure, flow, particle size distribution and coolant temperature, the simulation model has proven as a suitable tool to predict the fouling and identify engine settings for fouling reduction.</div></div>

The concept of using piezoelectric actuators and sensors to identify damages in advanced structural systems has drawn considerable interest among the research community due to its importance in preventing catastrophic failures. Recent progress in piezoelectric technologies and manufacturing has made it possible to manufacture smart multilayered multifunctional piezoelectric fibers. When these fibers are used in the health monitoring of smart structures, they are generally under dynamic loads. However, the modeling and simulation of these fibers is even more complicated by the fact that they are generally characterized by electromechanical coupling, anisotropy in the transverse plane, and the possible bonding imperfection between their layers. With this in mind, the current research program was undertaken to investigate the dynamic behavior of multiple multilayered piezoelectric fibers in smart structure applications. Four aspects of the work were accordingly examined. The first is the development of an analytical model of the anisotropic layer in the multilayered piezoelectric fiber, which is capable of predicting stress variations in the anisotropic layer, under dynamic loads. The model is necessary for determining the overall behavior of a layered anisotropic piezoelectric fiber. The analytical formulation is based on the use of Fourier expansion and the separation of variables to reduce the original problem to a set of linear equations in terms of Bessel functions. The resulting set of linear equations are normalized to reduce the numerical ill-conditioning then solved for different boundary conditions. The significance of this newly developed model is manifested by its versatility and application with different material combination, loading frequencies and geometry.The second is extending and applying the developed anisotropic layer model to analyze the performance of the electromechanical behavior of a multilayered piezoelectric fiber as an actuator or a sensor. The analytical formulation is based on the use of a newly developed piezoelectric layer model with a transfer matrix representation, which can represent multiple layers including imperfectly bonded layers. The third is concerned with the development of a general method for the interaction between multilayered piezoelectric fibers and other scatterers. The theoretical formulations are based upon the consistent use of the superposition procedure and cylindrical function coordinate transformations using Graf’s theorem. This reduces the original interaction problem to the solution of a set of a single multilayered piezoelectric fiber and embedded scatterer problems. By using this single multilayered piezoelectric fiber solution as the building block, this method provides a general approach to deal with interactions involving complex boundary/interfacial conditions. The fourth is concerned with the numerical simulation of applying the developed models for the identification of multiple damages using both global and local optimization algorithms. This problem is formulated as an inverse problem which uses optimization techniques to minimize the error between the observed voltage readings induced by damages from a numerical experiment and the calculated voltage predictions induced by trial damages from theoretical simulations on an array of sensors. The models and techniques developed previously are applied to determine the size and location of damages using a newly developed optimization algorithm. The algorithm converges faster than conventional algorithms for single and multiple damages with two types of damages investigated: a circular void and a curved crack.The methods proposed in this thesis can be used to understand the dynamic behavior of multiple multilayered piezoelectric fibers interacting with damages for the general design of smart structures and the applications of smart structural health monitoring.

<div class="section abstract"><div class="htmlview paragraph">In order to illustrate the constant development of the automatic transmission controls area, this paper describes how the garage shift calibration works in vehicles with transverse front wheel drive powertrains.</div><div class="htmlview paragraph">A garage shift (GS) is the turbine speed transient commanded by the shift lever movement from Park to Drive or Reverse, from Neutral to Drive or Reverse, from Drive to Reverse, from Reverse to Drive, or from Drive or Reverse to Neutral [<span class="xref">1</span>].</div><div class="htmlview paragraph">A usual metric to verify the garage shift comfort is the data acquisition of the fore-aft acceleration on the seat track, but also the shift time should be considered, as well as the clutch energy and the repeatability of the shift feeling for different temperatures and engine idle speed levels.</div><div class="htmlview paragraph">This paper demonstrates the transmission calibration strategies to determine a sensitive and a non-sensitive garage shift and its interactions with the engine calibration.</div><div class="htmlview paragraph">Many factors may affect the garage shift calibration, like hardware controls (software and calibration), hydraulic system (fluid and actuators), clutches (design and friction material) step ratios, and non-transmission factors such as idle control and engine torque signal accuracy [<span class="xref">2</span>]. The vehicle’s sensitivity to torsional driveline inputs and the powertrain mounts configuration also influence the shift quality perception.</div></div>

<div class="htmlview paragraph">Presenting a brand new approach to heat exchangers for engines, transmissions, hydraulic systems, etc.</div> <div class="htmlview paragraph">This new heat exchanger is made of only two pieces of circular extruded aluminum profiles: Core and shell. No soldering: The core and the shell is assembled by a minimum of automated work.</div> <div class="htmlview paragraph">In an oil to water cooling application, the active surface on the oil side of the core is enlarged by fins 0.2 mm thick, 0.3 mm spacing, and 3 mm high. The fins are made in unique production machines and enlarge the active surface area approximately five times compared to a conventional heat exchanger of the same dimensions.</div> <div class="htmlview paragraph">The principle utilizes the low pressure drop at laminar flow and avoids the disadvantage of low heat transfer after a certain laminar flow length. The result is approximately three times higher oil heat dissipation, combined with very low oil pressure drop, compared to conventional technique.</div> <div class="htmlview paragraph">The inner surface of the core, the water side, is extremely tolerant to dirty water and gives negligible pressure drop.</div> <div class="htmlview paragraph">This new heat exchanger is made of only one metal, aluminum. The characteristics of corrosion are therefore easy to define.</div>

Article Propulsion / Aircraft Integration of Hypersonic Vehicles with Active Thrust-Vectoring and Real-Time Simulation of Dynamic Engine Behaviour was published on December 1, 1999 in the journal International Journal of Turbo & Jet-Engines (volume 16, issue 4).

<div class="htmlview paragraph">Controlled Auto-Ignition (CAI) combustion, also known as HCCI or PCCI, has recently emerged as a viable alternative combustion process to the conventional spark ignition (SI) or compression ignition (CI) process for internal combustion (IC) engines, owing to its potential for high efficiency and extremely low emissions. One of the most effective and practical means of achieving CAI combustion in an engine is to retain or recycle the burnt gases. In order to understand better the effects of recycled burnt gases on CAI combustion, detailed analytical and experimental studies have been carried out. The analytical studies were performed using an engine simulation model with detailed chemical kinetics.</div> <div class="htmlview paragraph">The five effects of the recycled burned gases studied include:</div> <div class="htmlview paragraph"> <ol class="list nostyle"> <li class="list-item"><span class="li-label">(1.)</span><div class="htmlview paragraph">Charge heating effect: higher intake charge temperature due to hot burned gases;</div></li> <li class="list-item"><span class="li-label">(2.)</span><div class="htmlview paragraph">Dilution effect: the reduction of oxygen due to the presence of the burned gases;</div></li> <li class="list-item"><span class="li-label">(3.)</span><div class="htmlview paragraph">Heat capacity effect: due to higher specific heat capacity of burned gases;</div></li> <li class="list-item"><span class="li-label">(4.)</span><div class="htmlview paragraph">Chemical effect: chemical reactions involving CO<sub>2</sub> and H<sub>2</sub>O in the burned gases</div></li> <li class="list-item"><span class="li-label">(5.)</span><div class="htmlview paragraph">Stratification effect: recycled burned gases are stratified from the fuel/air mixture.</div></li> </ol> </div> <div class="htmlview paragraph">And the main conclusions are:</div> <div class="htmlview paragraph"> <ol class="list nostyle"> <li class="list-item"><span class="li-label">(1.)</span><div class="htmlview paragraph">The charge heating effect is mainly responsible for the advanced AI timing due to hot burned gases. It increases the heat release rate and shortens the combustion duration.</div></li> <li class="list-item"><span class="li-label">(2.)</span><div class="htmlview paragraph">The dilution effect does not affect AI timing, but it extends combustion duration. Its slows down the heat release rate only when large amount of burned gases is present.</div></li> <li class="list-item"><span class="li-label">(3.)</span><div class="htmlview paragraph">The heat capacity effect is mainly responsible for the reduction in the heat release rate, and it has a similar effect to extend the combustion duration as the dilution effect.</div></li> <li class="list-item"><span class="li-label">(4.)</span><div class="htmlview paragraph">The chemical effect does not affect AI timing and heat release rate. It reduces the combustion duration slightly at high concentrations of burned gases.</div></li> <li class="list-item"><span class="li-label">(5.)</span><div class="htmlview paragraph">The stratified burned gases facilitate the CAI combustion due to the presence of higher temperature region at the boundary between of the hot burned gases and combustible charge.</div></li> </ol> </div>

<div class="section abstract"><div class="htmlview paragraph">This paper details testing for torque converter clutch (TCC) characterization during steady state and dynamic operation under controlled slip conditions on a dynamometer setup. The subject torque converter under test is a twin plate clutch with a dual stage turbine damper without a centrifugal pendulum absorber. An overview is provided of the dynamometer setup, hydraulic system and control techniques for regulating the apply pressure to the torque converter and clutch. To quantify the performance of the clutch in terms of control stability, pressure to torque relationship and the dynamic behavior during apply and release, a matrix of oil temperatures, output speeds, input torques, and clutch apply pressures were imposed upon the torque converter. The torque capacity of the clutch is estimated with the dimensions of the friction surfaces and pressure plate and an enhanced lookup data of K-factor obtained through testing of the hydrodynamics at input torques from 10 to 200 Nm over a speed ratio range consistent with controlled slip. The influence of controlled operating point parameters is reported as TCC apply pressure verse estimated TCC torque. The effect of temperature, output speed and the sign of input torque are shown to a departure from the normally assumed linear relationship between pressure and torque. The results and procedures presented can be utilized to improve in vehicle control schemes through more accurate pressure to torque gain scheduling.</div></div>

<div class="htmlview paragraph">The Columbus laboratory module, developed by Astrium Bremen as prime contractor and Alenia Spazio as co-prime, is the European contribution to the International Space Station (ISS) program and as such it will support, once in orbit, micro-gravity and space based research activities of the member states.</div> <div class="htmlview paragraph">Columbus Environmental Control System (ECS) employs an Environmental Control and Life Support System (ECLSS) providing atmosphere pressure, cabin ventilation and temperature humidity control inside the module in conjunction with an autonomous Active Thermal Control System (ATCS) that provides the heat collection capability. The ATCS, based on software controlled water loop, provides also the cooling capability for Payloads and Subsystem equipment. The ECS is completed with the Passive Thermal Control System based on software controlled shell heating system plus passive fixtures such as Multi-Layers Insulation (MLI) blankets.</div> <div class="htmlview paragraph">Generally, both, the Columbus ATCS as well as the ECLSS are qualified via simplified but representative tests and concluding analyses. Complete verification of the module thermal and environmental control design however, will be performed via analysis supported by ECS System Level Integrated Test as well as the predictions for flight.</div> <div class="htmlview paragraph">With respect to responsibility sharing, Alenia is responsible for all verification by test related to thermal/environmental aspects, i.e. Alenia will define the test requirements and cases to be performed via the establishment of a dedicated test specification. On the other side, definition and production of the test set-up as well as the performance of the test is assigned to the Columbus prime Astrium SI Bremen.</div> <div class="htmlview paragraph">In order to get confidence on the functional performance of the Columbus ECS and to validate the Integrated Overall Thermal Mathematical Model (IOTMM) on system level the module will be subjected to an Integrated System Test (IST).</div> <div class="htmlview paragraph">Purpose of the ECS IST is to provide the first verification of the thermal/environmental interrelation between the active cooling (ATCS) and environmental control system (ECLSS) hardware and software and to collect as much characteristic thermal data as possible for the validation of the flight configuration IOTMM. This test will represent the second and last test in series on the flight configuration of the Columbus module.</div> <div class="htmlview paragraph">Previous tests, for verification of the functional interfaces of the ATCS and ECLSS, have been performed already in the frame of the Electrical Test Model (ETM) utilization. However, this test did not provide information on environmental and thermal parameters of the system but rather on the functional interrelations of the relevant units of the subsystems. Presently, the subject test will be performed in the integration hall of Astrium SI Bremen (Class 100.000 clean room conditions) and the pressurized shell is planned to be covered by the flight multi-layer insulation only located beneath the meteoroid debris panels (MDPS) of the module. However, in order to get as much as possible characteristic data of the system not only the test cases have to be selected very carefully but also additional test supporting equipment (TSE) has to be evaluated.</div> <div class="htmlview paragraph">The present paper summarizes the efforts generated to establish the Environmental/Thermal test in the frame of the system level IST of the Columbus module, describes the interrelation aspects of the thermal/environmental subsystem verification by test and analysis and presents the derived methodologies and expected results.</div>