Browse Topic: Chokes

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Using Monolithic Filters to Address EMI in Medical DevicesTBMG-351009/1/2019
Many factors are conspiring to increase the amount of “noise” or interference that can disturb the functionality and even damage electronic devices, starting with the sheer number used in our vicinity at any given time. Today’s Wi-Fi or Bluetooth-enabled medical instruments and even medical implants provide a prime example.
Analysis and Development of Compact Models for Mass Flows through Butterfly Throttle Valves2018-01-08764/3/2018
Throttles and wastegates are devices used in modern engines for accurate control of the gas flows. It is beneficial, for the control implementation, to have compact and accurate models that describe the flow behavior. The compressible isentropic restriction is a frequently used model, it is simple and reasonable accurate but it has some issues. One special issue is that it predicts that the choking occurs at too high pressure ratios, for example the isentropic model predicts choking at a pressure ratio of 0.52, while experimental data can have choking at 0.4 or even lower. In this work, experimental data is acquired from throttles tested both in a flow bench and mounted as main throttle on a turbocharged gasoline engine. To analyze the flow behavior several flow characterizations are performed at different throttle openings. For the engine installation a special test procedure is adopted and the results show that the engine and the flow bench give the same characteristic behavior of the throttle. In particular, both installations show choking pressure ratios that are significantly lower than what the compressible isentropic restriction predicts. To remedy this and capture the behavior, different modifications of the isentropic model are investigated. Some promising model modifications are analyzed; one that uses the conservation of momentum, energy, and mass to derive a compact expression for the mass flow, and another that uses an ellipse model. All modifications analyzed give lower pressure ratios at choking.
Holmbom, Robin, Eriksson, Lars
Fabrication of an Integrated Photonic Waveguide Joint in Micromachined SiliconTBMG-242554/1/2016
High-aspect-ratio silicon structures are necessary components in many MEMS (microelectromechanical systems). Aspect ratio is defined as the ratio of the height of the structure to its lateral width. The structures are typically fabricated through bulk micromachining steps such as deep reactive ion etching. In some cases, multiple levels of high-aspect-ratio structures are required. For instance, one may want to etch completely through a silicon wafer to thermally isolate a bolometer or provide waveguide coupling to an antenna defined on an insulating membrane, and at the same time have integrated high-topology structures required for microwave coupling or filtering. Definition of the structures typically uses photolithographic technology. But for high-aspect-ratio structures, spin cast resist becomes difficult to incorporate due to the non-uniform thickness of the resist around tall structures. One can cast very thick layers of photoresist, but this limits the minimum feature size, and additionally, very thick layers of photoresist are difficult to work with due to solvent release and moisture that can cause the resist to crack or swell. For electromagnetic reasons, the structures would preferably be made from conductive material such as metal or degeneratively doped silicon. The objective of this work was to incorporate multiple levels of conductive high-aspectratio structures with standard micromachining processes.
Multipath, Multistage, Erosion-Resistive Valve for Downhole Flow ControlTBMG-238712/1/2016
Multipath, multistage, erosion-resistant flow control valves have been developed that can sustain the extremely high pressure of deep oil wells. Fitting in the restricted available space and operating using limited power with a long lifetime are challenges for choke valves in the downhole environment of oil wells. These valves must control the flow rate from high-pressure oil reservoirs in the presence of fluids that have non-zero sand concentrations. This design consists of a digitized flow control valve with multipath and multistage pressure reduction structures. Specifically, the valve is configured as a set of parallel flow paths from the inlet to the outlet.
Experimental Investigation of Variable Geometry Compressor for Highly Boosted Gasoline Engines2015-01-12894/14/2015
A key technology for further improving the efficiency of gasoline engines lies in downsizing in combination with turbocharging. Decreasing the engine displacement greatly increases the demands on the turbocharging system. The charging of the engine with a single-stage turbocharger leads to a compromise to fulfill the requirements of the nominal power of the engine and the low-end torque. To avoid the use of complex two-stage boosting systems, it is necessary to increase the pressure ratio and the air flow rate at the same time. The wide speed and airflow range of gasoline engines intensify this trade-off. The use of a variable geometry turbine (VGT), additionally equipped with a wastegate bypass, offers great potential to meet the requirements on the turbine side. The range of stable operation of the compressor is limited by choke at high mass flow rates and surge at low mass flow rates. The variable geometry compressor (VGC) is one promising approach to extend the compressor map. A variable charging system consisting of VGC and VGT offers great potential to meet the future requirement for highly boosted engines. The present paper shows experimental investigations of the potential of a variable geometry turbine with an additional wastegate on a small sized gasoline engine. To reach the torque and nominal power characteristic of a 2-stage boosted reference engine, the test engine is additionally equipped with a camshaft phasing system on the exhaust side. In addition two different variable geometry compressors are investigated.
Herbst, Fabian, Eilts, Peter
Cloud Security & ComplianceTBMG-218834/1/2015
Not too many years ago, network security was a relatively low level priority in most organizations. That has changed today due to such high level failures as the recent breaches at Sony and Target. Closer to home, the University of Maryland is now incurring large expenses for all students due to the recent leak of personally identifiable student information.
Simulation of Tractor Operation in Threshing Field by Creating a Dust Environment to Study the Operational Behavior of Tractor2015-26-01451/14/2015
The objective of this project is “Bringing Field to Lab”. Normally in field, tractors are utilized for various applications like harvesting and threshing operation in a dusty environment which consists of paddy, sand, straw etc. These dusts would affect the tractor performance and often cause problem like engine choking at severe condition. Field data on threshing acquired from north Indian places like Jaitsar, Jalandhar where threshing done in summer at a temperature around 50°C. Also during threshing full tractor power is used through (PTO) power take off and this load fluctuates according to manual loading of paddy in thresher. Many iterations are carried out to simulate the real time loading of tractor in lab level and from the results concepts like, a) Forced dust blowing arrangement with spray quantity control - Simulates Threshing environment, b) Room heaters with controllers for maintaining room temperature-Simulates North India environment, c) DYNO arrangement for PTO loading - Simulates thresher loading of tractor and d) Time controlled dust flow to maintain a dust environment similar to field are developed. A test up is developed with normal dust throw of 250 grams / min and PTO loading which simulates the tractor operation in field condition and also give close correlation between field and lab level. The parameters like Engine coolant temperature (IN and OUT), Engine oil temperature, Transmission oil temperature and Engine suction pressure (due to dust block in inlet air filter the pressure get vary) can be mapped. This become our standard test and it is followed now for our new projects and by that field failures during initial phase of development are identified.
Arthanathan, Sankaranarayanan
Hydraulic High-Pressure Valve Controller Using the In Situ Pressure DifferenceTBMG-2095411/1/2014
Various applications exist where high-pressure valves are required, but the problem for control of such valves lies in that they have to move against a strong pressure differential that may require significant force, energy, and large actuators. The solution to this problem is to take advantage of the in situ pressure differential to operate valves by opening small valves to change the pressure on either chamber of a hydraulic cylinder that is connected to the valve’s moving element.
Analyzing 6-Pulse Drive Harmonic Mitigation Techniques for Industrial AutomationTBMG-2065110/1/2014
Contemporary industrial automation control systems are employing variable frequency drives (VFDs) in ever-increasing numbers. VFDs give control engineers flexibility to precisely regulate the speed and torque of motors in a wide array of applications. The proliferation of these VFDs has brought increased attention to harmonic distortion created by these drives and their effects on the power system. A standard-pulse drive with no built-in harmonic mitigation controls may interfere with neighboring equipment, reduce equipment life, and create a serious negative impact on the quality of utility power. Looking at the theory of operation for the following harmonic mitigation techniques and their typical performance levels may help take the guesswork out of harmonic reduction for these power systems.
Numerical Flow Analysis of a Centrifugal Compressor with Ported and without Ported Shroud2014-01-16554/1/2014
Turbochargers are commonly used in automotive engines to increase the internal combustion engine performance during off design operation conditions. When used, a most wide operation range for the turbocharger is desired, which is limited on the compressor side by the choke condition and the surge phenomenon. The ported shroud technology is used to extend the operable working range of the compressor, which permits flow disturbances that block the blade passage to escape and stream back through the shroud cavity to the compressor inlet. The impact of this technology on a speed-line at near optimal operation condition and near surge operation condition is investigated. A numerical study investigating the flow-field in a centrifugal compressor of an automotive turbocharger has been performed using Large Eddy Simulation. The wheel rotation is handled by the numerically expensive sliding mesh technique. In this analysis, the full compressor geometry (360 deg) is considered. Numerical solutions with and without ported shroud for a near optimal operation condition and near-surge operation condition. The flow-field of the different cases is analyzed to elucidate the functionality of the ported shroud. In agreement with previous observations, it was found that the ported shroud reduces the flow disturbances in the blade passage for all operating conditions. However, the compressor efficiency for the off-design operation condition was found to be higher without the ported shroud, supporting the findings reported recently by an experimental investigation. The computational results are validated with experimental measurements in terms of the performance parameters and available Particle Image Velocimetry data.
Semlitsch, Bernhard, V, JyothishKumar, Mihaescu, Mihai, Fuchs, Laszlo, Gutmark, Ephraim, Gancedo, Matthieu
Process for Patterning Indium for Bump BondingTBMG-1526312/1/2012
An innovation was created for the Cosmology Large Angular Scale Surveyor for integration of low-temperature detector chips with a silicon backshort and a silicon photonic choke through flip-chip bonding. Indium bumps are typically patterned using liftoff processes, which require thick resist. In some applications, it is necessary to locate the bumps close to high-aspect-ratio structures such as wafer through-holes. In those cases, liftoff processes are challenging, and require complicated and time-consuming spray coating technology if the high-aspect-ratio structures are delineated prior to the indium bump process. Alternatively, processing the indium bumps first is limited by compatibility of the indium with subsequent processing. The present invention allows for locating bumps arbitrarily close to multiple-level high-aspect-ratio structures, and for indium bumps to be formed without liftoff resist.
912iS Fuel Injected Aircraft Engine2012-32-004910/23/2012
The 912 engine is a well known 4-cylinder horizontally opposed 4-stroke liquid-/air-cooled aircraft engine. The 912 family has a strong track record: 40 000 engines sold / 25 000 still in operation / 5 million flight hours annually. 88% of all light aircraft OEMs use Rotax engines. The 912iS is an evolution of the Rotax 912ULS carbureted engine. The “i” stands for electronic fuel injection which has been developed according to flight standards, providing a better fuel efficiency over the current 912ULS of more than 20% and in a range of 38% to 70% compared to other competitive engines in the light sport, ultra-light aircraft and the general aviation industry. BRP engineers have incorporated several technology enhancements. The fully redundant digital Engine Control Unit (ECU) offers a computer based electronic diagnostic system which makes it easier to diagnose and service the engine. The modern fuel system consists of two fuel rails and two injectors per cylinder, pressure regulator and a return line. Redundant Sensors monitor air box vacuum, exhaust gas temperature, ambient air pressure, inlet air temperature, coolant temperature and throttle position. The injection system ensures optimal fuel and air mixture at any altitude for longer flight range and lower operating costs. This makes the engine more environmentally friendly due to lower CO2 emission levels. Other advantages for the pilots are no manual choke, no carburetor icing, and no requirement for synchronising carburetors. The three-year development period included more than 10,000 hours on the test bench and 700 test hours in the air to ensure 2,000 hours time between overhauls (TBO); the same TBO as the 912 engine. At 63,6kg (140, 2 lbs), the Rotax 912 iS engine delivers the best power-to-weight ratio in its category.
Dopona, Michael, Foxhall, Nigel, Dutzler, Christoph
Engine Speed Control with a Choke Valve based on the Adaptive Control Approach - Mechanism to Drive both the Throttle Valve and the Choke Valve with a Single Motor2010-32-01169/28/2010
Research on an electrically controlled system which can stably maintain a constant engine speed, while carrying out choke operations using a choke valve when starting the engine, was carried out with the objective of constructing an electrically controlled auto choke system for a general purpose engine that can control both choke mechanism and engine speed with a single motor. Research was also carried out on a mechanism that could drive both the throttle and choke valves with a single motor. First, the throttle valve was fixed in the fully open position and the relationship between the choke valve mechanism and engine speed was analyzed. The relationship between the opening angle of the choke valve and engine speed could be formulated by second order transfer function. However, it became clear that transfer function parameters drastically changed depending on ambient temperature and plug seat temperature. Therefore, instead of using a proportional-integral-derivative (PID) controller, which is stable only under limited conditions, a self-tuning regulator was used to maintain a constant engine speed using a choke valve. By this, a constant engine speed could be controlled with a choke valve regardless of temperature change during operation. A mechanical part for an electrically controlled carburetor to drive both throttle and choke valves with a single motor was designed. This drives the gear, which holds the cam structure, with a single motor. The gear drives the throttle valve, and then drives the choke valve connected to the linkage system by the cam. In this way, the choke valve and throttle valve could be successfully operated without being affected by the other. From these results, an electrically controlled auto choke system for a general purpose engine, which could control both choke mechanism and engine speed with a single motor, was possible.
Shimamura, Hideaki, Kasai, Akihito, Arai, Tetsuya
An Optimization Design of Throttle Body for EFI Motorcycle Engine2008-01-15376/23/2008
This paper studied the optimization design of throttle body for electronic control motorcycle engine FY156FMI. It was studied the influence of the inner diameter, configuration of valve and its axis and inner configuration of the pipe of throttle body on the engine performance. The inner diameter of throttle body was designed on the basis of resonance theory. And the prototypes of throttle body designed were manufactured and tested by engine experiment. Results showed that the power of the engine applied with the throttle body, which has been optimization designed with a thinner throttle valve and a taper inlet port, and the size of inner diameter of throttle body increased from 26mm to 28mm and the thickness of the axis decreased, was improved effectively. The optimization throttle body can meet the design target.
Han-rui, Peng, Mei-chun, Peng, Lin-li, Zheng, Xu-bing, Deng, Yi-qing, lin, Xing-wen, Xie
Routines for Computing Pressure Drops in VenturisTBMG-17502/1/2004
A set of computer- program routines has been developed for calculating pressure drops and recoveries of flows through standard venturis, nozzle venturis, and orifices. Relative to prior methods used for such calculations, the method implemented by these routines offers greater accuracy because it involves fewer simplifying assumptions and is more generally applicable to wide ranges of flow conditions. These routines are based on conservation of momentum and energy equations for real nonideal fluids, the properties of which are calculated by curve-fitting subroutines based on empirical properties data. These routines are capable of representing cavitating, choked, non-cavitating, and unchoked flow conditions for liquids, gases, and supercritical fluids. For a computation of flow through a given venturi, nozzle venturi, or orifice, the routines determine which flow condition occurs: First, they calculate a throat pressure under the assumption that the flow is unchoked or non-cavitating, then they calculate the throat pressure under the assumption that the flow is choked or cavitating. The assumption that yields the higher throat pressure is selected as the correct one.
Development of a New Variable Venturi Carburetor8306172/1/1983
A new variable venturi carburetor has been developed, in order to achieve high metering accuracy, fuel economy, higher power and good driveability of the vehicle. This carburetor is a down-draft-type, and has better characteristics compared with the fixed venturi carburetor, such as better fuel atomization, lower cycle-to-cycle variation of combustion in lean mixture, faster response, and higher power. For this carburetor, a new type venturi and a new cold enrichment system has been developed. This venturi type has an exponential-profile with a nearly constant increasing rate of venturi opening area to the suction piston stroke. The new cold enrichment system controls the airfuel ratio in all conditions by changing air bleed quantities using the thermo-wax. With this system, cold drive-ability is improved greatly.
Morino, Toshiharu, Nakamura, Norihiko, Itoh, Takaaki
The Positive Displacement Supercharger and its Place in Aircraft Pressurization6503792/1/1965
Pressurization is a relatively new requirement for smaller utility, business and private aircraft. The necessity for simplicity and low cost in this market dictates the need for new equipment based on these principles. A range of positive displacement superchargers has been developed and is in service proving its reliability. The construction and performance of one type of positive displacement supercharger is discussed and associated air conditioning systems are studied. Particular reference is made to the advantages to be gained in driving a supercharger rather than using bleed air for pressurization in the case of turboprop engines.
Mayo, A. G. K.
CARBURETOR DESIGN AND CALIBRATION5302791/1/1953
Bolton, H. G.
TEE ECONOMY FALLACY3400081/1/1934
Shepard, E. H.
RECENT COOPERATIVE FUEL-RESEARCH PROGRESS2500011/1/1925
This report deals with further progress in the cooperative fuel-research. General factors underlying starting ability are discussed and experiments showing the effect of changes in spark character and of gas leakage are described. The probable mechanism of crankcase-oil dilution is treated, and further experiments with reference to this subject are explained. One experiment deals with operation with oil as a cooling medium to obtain high jacket-temperatures. Other experiments show the effect of change in piston clearance and in the number of piston-rings employed. Factors influencing the rate at which the diluent is eliminated from the diluted oil are shown to be of importance, and methods of examining these factors are stated.
SPARROW, S W, EISINGER, J O
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