Showing papers on "Secondary air injection published in 2013"

Experimental Investigation of Centrifugal Compressor Stabilization Techniques

Abstract: Results from a series of experiments to investigate techniques for extending the stable flow range of a centrifugal compressor are reported. The research was conducted in a high-speed centrifugal compressor at the NASA Glenn Research Center. The stabilizing effect of steadily flowing air-streams injected into the vaneless region of a vane-island diffuser through the shroud surface is described. Parametric variations of injection angle, injection flow rate, number of injectors, injector spacing, and injection versus bleed were investigated for a range of impeller speeds and tip clearances. Both the compressor discharge and an external source were used for the injection air supply. The stabilizing effect of flow obstructions created by tubes that were inserted into the diffuser vaneless space through the shroud was also investigated. Tube immersion into the vaneless space was varied in the flow obstruction experiments. Results from testing done at impeller design speed and tip clearance are presented. Surge margin improved by 1.7 points using injection air that was supplied from within the compressor. Externally supplied injection air was used to return the compressor to stable operation after being throttled into surge. The tubes, which were capped to prevent mass flux, provided 9.3 points of additional surge margin over the baseline surge margin of 11.7 points.

System and method of recirculating exhaust gas for use in a plurality of flow paths in a gas turbine engine

Abstract: A method includes generating an exhaust gas from combustion gases with a turbine; recirculating the exhaust gas along an exhaust recirculation flow path; reducing moisture within the exhaust gas along the exhaust recirculation path with an exhaust gas processing system; providing the exhaust gas to a first exhaust gas inlet of an exhaust gas compressor for compression; and providing the exhaust gas from the exhaust recirculation path to a second exhaust gas inlet separate from the first exhaust gas inlet for cooling, preheating, sealing, or any combination thereof.

High-Pressure Air Injection for Improved Oil Recovery: Low-Temperature Oxidation Models and Thermal Effect

Abstract: High-pressure air injection into light oil reservoirs is an effective technique for improved oil recovery (IOR), and this technique mainly depends upon a spontaneous low-temperature oxidation (LTO), which occurs at original reservoir temperatures. During the LTO process of air injection, oxygen in the injected air is consumed and carbon dioxide can be produced in the reservoir, leading to flue gas flooding and producing a significant amount of heat. In this paper, the mechanisms of the LTO reaction are analyzed and an improved LTO reaction model is established to facilitate reaction mechanism and reservoir simulation studies. A series of high-pressure LTO experiments using typical light oils were carried out in a temperature range from 70 to 170 °C to measure the reaction rates and to reveal the exothermic behavior of the LTO reactions. Heat-transfer analysis in the experimental process was conducted to examine the exothermic characteristics of the reaction using different reactors and at various experime...

System and method for protecting components in a gas turbine engine with exhaust gas recirculation

Abstract: A system includes a gas turbine engine that includes a combustor section having one or more combustors configured to generate combustion products, a turbine section having one or more turbine stages between an upstream end and a downstream end, an exhaust section disposed downstream from the downstream end of the turbine section, and a fluid supply system coupled to the exhaust section. The one or more turbine stages are driven by the combustion products. The exhaust section has an exhaust passage configured to receive the combustion products as an exhaust gas. The fluid supply system is configured to route a cooling gas to the exhaust section. The cooling gas has a temperature lower than the exhaust gas. The cooling gas includes an extracted exhaust gas, a gas separated from the extracted exhaust gas, carbon dioxide, carbon monoxide, nitrogen oxides, or a combination thereof.

Method and system for vacuum control

Abstract: Methods and systems are provided for controlling and coordinating control of a post-catalyst exhaust throttle and an EGR valve to expedite catalyst heating By closing both valves during an engine cold start, an elevated exhaust backpressure and increased heat rejection at an EGR cooler can be synergistically used to warm each of an engine and an exhaust catalyst The valves may also be controlled to vary an amount of exhaust flowing through an exhaust venturi so as to meet engine vacuum needs while providing a desired amount of engine EGR

Potential of spray-guided gasoline direct injection for reduction of fuel consumption and simultaneous compliance with stricter emissions regulations

Abstract: The combination of gasoline direct injection and turbocharging is a promising method to reduce the fuel consumption of internal combustion engines through engine downsizing, which leads to increased engine efficiencies and a reduction of CO2 emissions at a comparable power output. Spray-guided direct injection allows overall lean and unthrottled operation, which is realized with a highly stratified mixture at part load. However, exhaust gas aftertreatment with conventional three-way catalysts is currently not possible. Furthermore, insufficient mixture preparation, especially at the upper load limit of stratified charge operation, causes increased particulate matter emissions. This paper discusses the advantages of engine downsizing, by gasoline direct injection in combination with turbocharging, to reduce fuel consumption and presents the results of experimental and numerical investigations of stratified exhaust gas recirculation in a single-cylinder gasoline engine to reduce nitrogen oxide emissions. Th...

System and method for reducing back pressure in a gas turbine system

Abstract: In a first embodiment, a system, including an exhaust duct configured to flow an exhaust gas, and an air injection system coupled to the exhaust duct, wherein the air injection system comprises a first air injector configured to inject air into the exhaust duct to assist flow of the exhaust gas through the exhaust duct.

Method and system for catalyst temperature control

Abstract: Methods and systems are provided for controlling and coordinating control of a post-catalyst exhaust throttle and an EGR valve to expedite catalyst heating. By closing both valves during an engine cold start, an elevated exhaust backpressure and increased heat rejection at an EGR cooler can be synergistically used to warm each of an engine and an exhaust catalyst. The valves may also be controlled to vary an amount of exhaust flowing through an exhaust venturi so as to meet engine vacuum needs while providing a desired amount of engine EGR.

Enhanced vapor injection air-conditioning circulating system and control method thereof

Abstract: The invention relates to a central air-conditioning system, in particular to a duct air conditioner, namely an enhanced vapor injection air-conditioning circulating system. A vapor injection side electronic expansion valve of the system is subject to discharge superheat control instead of vapor injection superheat control; high discharge superheat is guaranteed, and heating capacity of the system can be further improved by vapor injection; the system is especially applicable to variable frequency compressors; high heating capacity is kept even under different operating frequencies; the system operates stably and fluctuates little. The enhanced vapor injection air-conditioning circulating system comprises a controller, a compressor, a four-way valve, a vapor-liquid separator, an economizer, a solenoid valve and a coolant pipe. The compressor is a variable frequency compressor. The economizer is a plate economizer. The electronic expansion valve controls vapor injection. The vapor injection electronic expansion valve is subject to discharge superheat control instead of vapor injection superheat control; accordingly, high discharge superheat is guaranteed, and heating capacity of the system is further improved by vapor injection. The system is especially applicable to variable frequency compressors; the heating capacity is kept even under different operating frequencies; the system operates stably and fluctuates little.

On the combination of high-pressure and low-pressure exhaust gas recirculation loops for improved fuel economy and reduced emissions in high-speed direct-injection engines

Abstract: In this paper, an experimental study of the combination of low-pressure and high-pressure exhaust gas recirculation architectures has been carried out. In the first part of the paper, the effects of both high-pressure and low-pressure exhaust gas recirculation architectures on engine behaviour and performance are analysed by means of a series of steady tests. In the second part, the effects of the combination of both architectures are addressed. The results show that the low-pressure configuration improves high-pressure exhaust gas recirculation results in brake-specific fuel consumption, nitrogen oxides and exhaust gas opacity; nevertheless, hydrocarbon emissions are increased, especially during the engine warm up. In addition, the exhaust gas recirculation rate achieved with low-pressure systems is limited by the pressure difference between diesel particulate matter outlet and compressor inlet; therefore, the high-pressure system can be used to achieve the required exhaust gas recirculation levels witho...

Power source device, electric vehicle provided with same, and electricity storage device

Abstract: In a power supply device, the gas exhaust valve is integrally coupled to the outer can at the time of opening the gas exhaust valve, and the connecting portion between the outer can and the gas exhaust valve is partially broken at the time of opening the gas exhaust valve by an internal pressure of the outer can, and the gas duct further comprises a joining aperture being connected airtight to the gas exhaust valve, and a duct exhaust portion being connected to the external gas exhaust duct, and the inner diameter d inside the gas duct is at least partially smaller than the outer diameter a of the gas exhaust valve between the joining aperture and the duct exhaust portion.

Continuous spin detonation of a coal-air mixture in a flow-type plane-radial combustor

Abstract: Regimes of continuous spin detonation of coal particles in an air flow in a flow-type plane-radial combustor 500 mm in diameter are studied. The tested substance is fine-grained cannel coal from Kuzbass having a particle size of 1–7 µm and containing 24.7% of volatiles, 14.2% of ashes, and 5.1% of moisture. A certain amount of hydrogen is added for coal transportation into the combustor and promotion of the chemical reaction on the surface of solid particles. To reduce air pressure losses in channels connecting the manifold and the combustor, their cross section is increased to limiting values (25 cm2), whereas the combustor exit diameter is reduced. The angle of the air flow direction and the combustor geometry are also varied. The minimum pressure difference in the air injection channels (16%) is reached with stability of continuous spin detonation in the combustor being retained. The domain of continuous spin detonation regimes in the coordinates of the fuel flow rate and specific flow rate of the mixture is constructed. The results of studying detonation burning of solid fuels can find applications in power engineering, chemical industry, and environmental science, in particular, contamination by combustion products.

Electric heating assisted passive and active regeneration for efficient emission controls of diesel engines

Abstract: A method of heating an exhaust gas in an exhaust after treatment system including a Diesel Oxidation Catalyst (DOC) and a diesel particulate filter (DPF) is provided. The method includes heating the exhaust gas to a predetermined temperature to increase N02 generation in the DOC when the DPF is not actively regenerated, and heating the exhaust gas to reduce an exhaust temperature gradient when the DPF is actively regenerated. The exhaust temperature gradient is reduced by providing more heat proximate a wall of an exhaust conduit and less heat proximate a center of the exhaust conduit.

Two-stroke uniflow engine

Abstract: A two-stroke uniflow engine is provided with: a cylinder; a piston; an exhaust valve that is opened and closed in order to discharge exhaust gas that is generated inside the cylinder; a scavenging port that takes active gas into the interior of the cylinder in accordance with a sliding movement of the piston; a fuel injection port that is provided in the internal circumferential surface of the cylinder; a fuel injection valve that injects fuel gas into the fuel injection port; and a fuel injection control unit that executes control of the injection of the fuel gas in the fuel injection valve, wherein the fuel injection control unit decides at least one of an injection pressure and an injection time of the fuel injection valve based on a change in pressure inside the cylinder that is caused by a reciprocating movement of the piston.

Using Compressed Air Injection to Control Seawater Intrusion in a Confined Coastal Aquifer

Abstract: Seawater intrusion into groundwater is an important problem in many coastal regions. Freshwater injection has been widely used to avoid seawater contaminating freshwater systems, but is not an attractive solution where freshwater is limited. We investigated the effects of injecting compressed air on seawater movement in a confined coastal aquifer using a numerical simulation. We used TOUGH2/EOS7 software to analyze the effects of injecting compressed air in preventing seawater intruding into a hypothetical confined coastal aquifer (Henry’s problem), simulating steady-state initial conditions and comparing the results with the literature sources. We then performed a transient-state numerical simulation to quantify the seawater intrusion control efficiency achieved by injecting air. The results showed that injecting compressed air can mitigate seawater intrusion: Saltwater was ejected from the aquifer and the seawater circulation disappeared. The injected air flowed upward and spread laterally near the top of the aquifer because of the groundwater and air densities. Injecting air significantly increased the groundwater and gas pressures near the air injection zone and at the top of the aquifer. The air injection rate increased rapidly, then increased gradually. Freshwater injection was also simulated using settings similar to those used for air injection, and this showed that seawater intrusion is prevented more efficiently by freshwater injection than air injection. However, freshwater resources are valuable, whereas air is readily available, so injecting air to mitigate seawater intrusion has great potential. The modeling approach that we used will be used as a foundation for future work.

Active control of compressor extraction flows used to cool a turbine exhaust frame

Abstract: A gas turbine (10) includes at least one combustor (14) and an exhaust frame (18); a compressor (12) adapted to supply air to the combustor (14) and to supply bleed air to the exhaust frame (18). A cooling air supply duct (22) is arranged to supply ambient air to the exhaust frame (18) and at least one ejector (20) is arranged to supply the bleed air to the cooling air supply duct (22) upstream of the exhaust frame (18). A control valve (30) is configured to control the supply of compressor bleed air to the cooling air supply duct (22) and to the exhaust frame (18) as a function of turbine exhaust temperature and/or turbine load conditions and cooling requirements at the various turbine load conditions.

Octane separation system and operating method

Abstract: An engine method, comprising delivering high octane fuel to a high octane fuel tank and delivering low octane fuel to a low octane fuel tank and injecting atmospheric air into an exhaust system for secondary air injection in response to delivering low octane fuel to an engine.

Simulation of Dynamic Two-Phase Flow During Multistep Air Sparging

Abstract: Air sparging is an in situ soil/groundwater remediation technology, which involves the injection of pressurized air through air sparging well below the zone of contamination. To investigate the rate-dependent flow properties during multistep air sparging, a rule-based dynamic two-phase flow model was developed and applied to a 3D pore network which is employed to characterize the void structure of porous media. The simulated dynamic two-phase flow at the pore scale or microscale was translated into functional relationships at the continuum-scale of capillary pressure–saturation (P c–S) and relative permeability—saturation (K r–S) relationships. A significant contribution from the air injection pressure step and duration time of each air injection pressure on both of the above relationships was observed during the multistep air sparging tests. It is observed from the simulation that at a given matric potential, larger amount of water is retained during transient flow than that during steady flow. Shorter the duration of each air injection pressure step, there is higher fraction of retained water. The relative air/water permeability values are also greatly affected by the pressure step. With large air injection pressure step, the air/water relative permeability is much higher than that with a smaller air injection pressure step at the same water saturation level. However, the impact of pressure step on relative permeability is not consistent for flows with different capillary numbers (N ca). When compared with relative air permeability, relative water permeability has a higher scatter. It was further observed that the dynamic effects on the relative permeability curve are more apparent for networks with larger pore sizes than that with smaller pore sizes. In addition, the effect of pore size on relative water permeability is higher than that on relative air permeability.

Flow reversing exhaust gas mixer

Abstract: An exhaust mixing device for mixing an exhaust produced by an engine with a reagent exhaust treatment fluid that is dosed into the exhaust from a dosing module. The exhaust mixing device includes a decomposition tube having a first end and a second end. The first end of the decomposition tube is configured to receive the exhaust and the reagent exhaust treatment fluid. A flow reversing device is positioned at the second end of the decomposition tube. The flow reversing device includes a plurality of deflecting members that intermix the exhaust and reagent exhaust treatment fluid, and direct the exhaust and reagent exhaust treatment fluid in predetermined directions, wherein the flow reversing device reverses a flow direction of the exhaust back towards the first end of the decomposition tube.

Devices and methods for exhaust gas recirculation operation of an engine

Abstract: An engine is provided that includes an exhaust gas recirculation (EGR) conduit in fluidic communication with a first exhaust valve in a cylinder and an intake system, an exhaust conduit in fluidic communication with a second exhaust valve in the cylinder and an emission control device. During operation with the first valve active and the second valve deactivated, a fixed EGR level can be provided. However, during operation with the first valve deactivated and the second valve active, increased engine output can be achieved with reduced EGR without requiring additional exhaust throttling or switching valves.

Intelligent bag filling for exhaust sampling system

Abstract: An exhaust sampling system for an engine is provided. The exhaust sampling system may include a source of exhaust gas, an exhaust collection unit including at least one collection bag that selectively receives the exhaust gas, and a first sample probe in fluid communication with the source of exhaust gas that selectively supplies the at least one collection bag with the exhaust gas. The exhaust sampling system may also include a controller that permits flow of the exhaust gas from the first sample probe to the at least one collection bag in a first state and prevents flow of the exhaust gas from the first sample probe to the at least one collection bag in a second state. The controller may determine an extraction rate of the first sample probe based on an ON time of the engine during a sampling period.

Recovery of Light Oil by Medium Temperature Oxidation

Abstract: We study one aspect of combustion in porous media for the recovery of light oil. We assume that there is a temperature range above low temperature combustion where oxygen is added to the aliphatic oils to form oxygenated compounds and below the temperature where cracking and coke formation occurs. In the intermediate range oil is combusted to form small combustion products like water, CO $$_2$$ , or CO. We call this medium temperature oxidation (MTO). Our simplified model considers light oil recovery when it is displaced by air at medium pressures in linear geometry, for the case when water is absent. The resulting MTO combustion displaces all the oil. There are adjacent vaporization and combustion zones, traveling with the same speed. The MTO reaction is assumed to be slow, so that vaporization is much faster. The solution of the model equations leads to a thermal wave upstream, a MTO wave in the middle and a cold isothermal Buckley–Leverett gas displacement process downstream. One of the unexpected results is that vaporization occurs upstream of the combustion zone. In the initial period the recovery curve is typical of gas displacement, but after a critical amount of air has been injected the cumulative oil recovery increases linearly until all oil has been recovered. In our model, the oil recovery is independent of reaction rate parameters, but the recovery is much faster than for gas displacement. Finally, the recovery is slower for higher boiling point and higher oil viscosity, but faster at higher injection pressure. We give a simple engineering procedure to compute recovery curves for a variety of different conditions.