Cold Flow Tests Research Articles

Design and Testing of Fiber-Optic Wall Shear Gauge for Hot Flows

This investigation details the design, analysis, and testing of a new, two-component wall shear gauge for three-dimensional, high-temperature flows. This gauge is a direct-measuring, nonnulling design with a round head surrounded by a small gap. Two flexure rings are used to allow small motions of the floating head. Strain gauges are mounted on the flexures, and fiber-optic displacement sensors measure how far polished faces of counterweights move in relation to a fixed housing. The strain gauges are for validation of the newer fiber optics. The sensor is constructed of Haynes® 230®, a high-temperature nickel alloy. All components, in pure fiber-optic form, can survive to a temperature of 1073 K. The dynamic range of the sensor is from 0-500 Pa. Higher shear forces can be measured by changing the floating head size. No damping or water cooling of the sensor is required. Finite element modeling was used during the design and analysis of the sensor. Static structural, modal, and thermal analyses were performed using the ANSYS finite element package. Repeated cold-flow tests at Mach 2.4 and Mach 4.0 under high-Reynolds-number conditions have been accomplished in the Virginia Tech Supersonic Wind Tunnel. Experimental results are in excellent agreement with semiempirical prediction methods.

KINETICS OF FAST PYROLYSIS OF RICE HUSKS USING AN EXTERNALLY PLASMA-HEATED LAMINAR ENTRAINED FLOW REACTOR

A plasma-heated laminar entrained flow reactor (LEFR) was developed for studying the kinetics of fast pyrolysis of biomass particles at rapid heating rates. In order to achieve a controllable, stable, and uniform high-temperature gas flow in the reactor, a plasma jet was used as the primary heating source for the LEFR, and an electric heater was used as an auxiliary heating source. Reynolds number was used as the principle of similitude to determine the flow distribution in the reactor through a series of cold flow tests. Comprehensive temperature measurements were taken, and corresponding temperature profiles were obtained. Experiments using rice husk were conducted in the LEFR. The results showed that biomass particles below 100 .m could be pyrolyzed sufficiently, and thus the pyrolysis kinetics of biomass could be studied in this reactor. Based on the experimental data, a kinetic model for rice husk was proposed, and the kinetic parameters (i.e., activation energy and frequency factor) were determined.

Industrial Development and Operation of an Efficient Riser Separation System for FCC Units

With over 300 units in operation, Fluid Catalytic Cracking (FCC) is currently the dominant refinery conversion process. Over the last years, rapid separation of hydrocarbon vapors and catalyst at the riser outlet has been put forward to limit non-selective decomposition of reaction products, thus enhancing product selectivities.A new riser separator system, called RS², was developed to minimize post-riser cracking, while maintaining flexibility of operation. The development included cold flow testing, CFD and pilot plant testing, and aimed at minimizing both thermal degradation and catalytic overcracking. Cold flow testing was conducted at a representative scale (scale 1/10th) on a large cold flow mock-up. Testing various riser separator configurations provided a thorough understanding, both through visual observations, pressure drop measurements and tracer studies. Hot pilot plant testing was conducted to investigate the effect on yields of the riser separation system in the reactor-stripper under adiabatic operation as a function of operating conditions. The separator had a significant impact on the FCC heat balance and a large reduction of dry gas yield was observed.The resulting technology was successfully implemented on an industrial resid catalytic cracking unit. Operation of the separator was proven smooth and flexible with enhanced performance, while the industrial observations confirm the R&D conclusions. This paper therefore summarizes the R&D study and the industrial operation trends. In particular, the impact of stripper bed level on operation is discussed and explained based on the flow phenomena and design aspects.

Cold-Flow Testing of Subscale Model Exhaust System for Space-Based Laser

Covers advancements in spacecraft and tactical and strategic missile systems, including subsystem design and application, mission design and analysis, materials and structures, developments in space sciences, space processing and manufacturing, space operations, and applications of space technologies to other fields.

외부혼합 와류분사기를 장착한 액체로켓엔진용 축소형 연소기 개발

본 논문에서는 와류분사기를 가진 액체로켓엔진용 축소형 연소기의 설계/제작/시험에 대해 기술하였다. 와류분사기는 내부에 액체산소 외부에 케로신을 공급하여 노즐 외부에서 혼합하는 구조를 가지고 있다. 축소형 연소기는 분사기 헤드, 삭마 냉각방식의 내열재 연소실 그리고 물냉각 노즐로 구성되어 있다. 분사기 헤드는 18 개의 주 분사기, 하나의 중앙 분사기, 연료 메니폴드, 산화제 메니폴드 그리고 추진제 분배기 등으로 구성되어 있다. 축소형 연소기 제작 후 수류시험 및 점화시험을 거쳐 설계점 및 탈설계점에서의 연소시험을 성공적으로 수행하였다. 연소시험결과 분사기 차압은 수류시험시의 값과 비슷하였고 연소효율은 목표치보다 높게 나왔으며, 정상연소시 동압의 진폭은 규격조건을 만족하였고 고주파 연소 불안정은 발생하지 않았다. The procedure of design and manufacture of sub-scale combustor using bipropellant swirl injector with external mixing for a liquid rocket engine are described. The results of cold flow test, ignition test and combustion test of the sub-scale combustor are also given in this paper. The sub-scale combustor uses liquid oxygen(LOx) and kerosene as propellants and has a injector head, an ablative material combustor wall and a water cooled nozzle. The injector head has LOx manifold, fuel manifold, fire face plate, one center swirl injector and 18 main swirl injectors. The cold flow, ignition and combustion tests were successfully performed without damage of combustor. Results of hot firing tests show that combustion efficiency meets the target of design and operations of start and stop cyclogram are stable and high frequency combustion instability does not occur.

Flow maldistribution measurements in wall-flow diesel filters

Understanding the flow maldistribution phenomena inside porous ceramic diesel particulate filters and their effects on the pressure drop and regeneration characteristics is important for the successful design and modelling of this class of exhaust aftertreatment system. In this paper the results from an experimental study of flow distribution in wall-flow diesel filters are presented. The experiments were performed on a specially designed cold flow test rig, under steady state flow conditions. The flow distribution at the exit of cordierite and SiC filters were measured with a hot film velocity sensor under low and medium mass flowrate conditions. The system configuration was varied to incorporate tests with and without the installation of an oxidation catalyst before the filter in order to investigate the effect of the catalyst honeycomb structure to the measured flow distribution. Flow distribution in filters loaded with various levels of particulate mass was also measured using the same device. The filters were loaded in a modern diesel engine run on catalyst-doped fuel up to different backpressure levels. A flow uniformity index was adopted in order to quantify the measured flow maldistribution by a single number for each case. The velocity distribution at the exit of the filters is found to be significantly affected by certain design and operating parameters of the system: diffuser-catalyst-filter. The results of this work aim to give a better assessment of the magnitude of flow maldistribution in diesel filters, which severely distort their pressure drop characteristics and affect the distribution of collected soot mass. In this way, a previously neglected aspect of the complex three-dimensional filter regeneration behaviour is better understood.

Orifice Diameter Ratio Effect on the Mixing Performances for Split Triplet Injectors

The effect of orifice diameter ratio on the mixing qualities of unlike-doublet and split-triplet impinging elements is experimentally studied. The quality of mixing was checked by performing cold-flow tests with nonreacting immiscible simulant liquids. The local volume fractions are determined by direct measurement of the volume of each liquid. The test matrix comprises combinations of the orifice diameter ratios from 1 to 1.5, with the jet momentum ratios (oxidizer/fuel) in the range of 0.5-6. Results show that impinging elements of unequal orifice diameters exhibit substantially different mixing qualities. Maximum mixing efficiency occurs at higher momentum ratios with increasing diameter ratio. Relative jet velocity ratio for optimum mixing ranges from 0.65 to 0.78 and from 0.87 to 0.92 for unlike-doublet and split-triplet elements, respectively. The split-triplet element is superior to the unlike-doublet element in both the mixing efficiency and the mixing-controlled characteristic velocity in the test range of interest. The diameter ratio effect on the mixing of split-triplet element is less significant than that on the unlike-doublet element mixing. The mixing factor of the split-triplet element for maximum mixing efficiency is 0.75.

이중 충돌제트의 혼합 성능 연구

이중 충돌형(unlike doublet impinging) 분사기의 직경변화에 따른 혼합특성을 모사 추진제에 의한 실험적인 방법으로 연구하였다. 분사유동은 레이놀즈수 2,500부터 12,000 사이의 난류제트를 사용하였으며, 분사공 직경 비를 1부터 1.5까지 확대시켜 직경변화에 따른 혼합특성을 고찰하였다. 분사공의 형상변수는 최적의 혼합특성을 갖는 설계치로 고정하였으며, 대기압 하의 분사유동장의 공기역학적 영향은 배제하였다. 매개변수로서 운동량비를 사용하여 혼합효율의 변화(mixing doublet impinging)를 고찰하였으며, 패터네이터(patternater)를 사용하여, 연료와 산화제의 국소 질량분포 측정 및 혼합비 분포를 측정하였다. 운동량비와 혼합효율의 상관성을 침투정도로 고려하여 연료와 산화제의 속도비와 혼합효율의 상관성을 고찰하였다. 분사공 직경이 증가됨에 따라 최대 혼합효율점이 운동량비가 증가되는 방향으로 이동함을 보였으며, 연료와 산화제의 속도 비 0.65~0.7영역에서 분사공 직경변화와 무관하게 혼합효율이 최대가 되었다. 또한 혼합효율은 추진제의 분사 충돌 시 상대제트의 침투 깊이 정도에 따라 큰 영향을 받는 것으로 나타났다. Experiments to investigate the mixing performance of unlike doublet impinging jets are conducted. Reynolds number of simulants used in this study rages from 1.0 to 1.5 Cold flow test is performed to investigate the hydrodynamic effect and spray of the impinging jets are collected locally and calculated by using Rupe's mixing efficiency equation. Momentum exchanges and relative velocity ratio between two jets are taken as the main parameter to represent the effect of enlargement of the orifice diameter. As diameter ratio increases, the corresponding momentum ratio where maximum mixing efficiency occurs and relative velocity at the maximum mixing efficiency ranges 0.6 to 0.7, respectively. Penetration depth can be taken as a prominent parameter to estimate the mixing efficiency.

Influence of blade passing on the stator wake in a transonic turbine stage investigated by particle image velocimetry and laser vibrometry

The aerodynamic behaviour of stator and rotor interaction in axial flow turbines is complex and highly unsteady. Particle image velocimetry (PIV) and laser vibrometry (LV) were used to investigate the phenomena observed in a transonic turbine stage operated continuously in a cold-flow test rig. While LV gave basic information on the frequency behaviour of the density fluctuations in the stator wake, stereoscopic PIV was used for investigations of the flowfield vorticity during rotor blade passing. Phase locking of the vortex shedding to the seventh and eighth harmonics of the blade passing frequency was observed.

Determination of Cyclogram for Liquid-Propellant Rocket Engine

A vertical test stand based on launcher propulsion system was constructed and several tests for the determination of cyclogram were carried out. To make an accurate estimation, static and dynamic pressures were measured and analyzed. Especially, static pressure measurements using fast response sensors without extension tubes were used to determine operation sequence more evidently. The standard operation times of final valves were determined in cold flow tests with an engine head, and fire formation time in combustion chamber was checked in an ignition test with an ignitor only. On the basis of these tests, ignition sequence was established and combustion test cyclogram was finally determined. According to combustion test, test results were well matched with the determined cyclogram within 0.05 sec.

Boundary Layer Development in the BR710 and BR715 LP Turbines—The Implementation of High-Lift and Ultra-High-Lift Concepts

This paper describes a detailed study into the unsteady boundary layer behavior in two high-lift and one ultra-high-lift Rolls-Royce Deutschland LP turbines. The objectives of the paper are to show that high-lift and ultra-high-lift concepts have been successfully incorporated into the design of these new LP turbine profiles. Measurements from surface mounted hot film sensors were made in full size, cold flow test rigs at the altitude test facility at Stuttgart University. The LP turbine blade profiles are thought to be state of the art in terms of their lift and design philosophy. The two high-lift profiles represent slightly different styles of velocity distribution. The first high-lift profile comes from a two-stage LP turbine (the BR710 cold-flow, high-lift demonstrator rig). The second high-lift profile tested is from a three-stage machine (the BR715 LPT rig). The ultra-high-lift profile measurements come from a redesign of the BR715 LP turbine: this is designated the BR715UHL LP turbine. This ultra-high-lift profile represents a 12 percent reduction in blade numbers compared to the original BR715 turbine. The results from NGV2 on all of the turbines show “classical” unsteady boundary layer behavior. The measurements from NGV3 (of both the BR715 and BR715UHL turbines) are more complicated, but can still be broken down into classical regions of wake-induced transition, natural transition and calming. The wakes from both upstream rotors and NGVs interact in a complicated manner, affecting the suction surface boundary layer of NGV3. This has important implications for the prediction of the flows on blade rows in multistage environments.

Effect of Momentum Ratio on the Mixing Performance of Unlike Split Triplet Injectors

Experimental investigation of mixing and mixing-controlled combustion efficiencies for sprays formed by unlike impinging split triplet injector elements was carried out. The quality of mixing was checked by performing cold-flow tests with inert simulant liquids. Measurements of local mass and mixture ratio distributions were made for different injection configurations and different jet momentum ratios. Results show that the quality of macroscopic mixing can be effectively characterized by the jet momentum ratio. The unlike split triplet element with lateral fuel injection is superior in mixing to either unlike doublet or unlike split triplet elements with central fuel injection. Secondary impingement appears to play a significant role in the extent of mixing. Mixing characteristics of the unlike split triplet element and its contribution to the promotion of macroscopic mixing efficiencies are discussed in detail.

スクラムジェットエンジンの混合・燃焼形態に関する考察 弱燃焼から強燃焼への遷移過程

The main purpose of this study is to reveal a transition mechanism between two typical combustion modes called ‘weak-combustion’ and ‘intensive-combustion’ observed in the firing tests of scramjet engines at Mach 4, 6 and 8 conditions of Ramjet Engine Test Facility (RJTF). For this purpose, flow structures in the combustor and their changes during the transition of the combustion mode are investigated by cold flow tests as well as numerical simulations. These results and the firing test results led us to conclude 1) that transition from ‘weak mode’ to ‘intensive mode’ is the consequence of the mutual interaction between enhancement of fuel/air mixing as well as combustion within the boundary layer and the growth of the boundary layer separation area and 2) that in the present engine principal fuel/air mixing and combustion strongly depend on the occurrence of large-scale boundary layer separation, thus the resulting principal combustion is characterized to be subsonic combustion within the separated boundary layer.

剥離泡を伴うロケットノズル流れの剪勇断応力感応液晶による可視化

Recently, an extraordinary nozzle flow pattern which contains separation bubbles was found in some types of rocket nozzles. Such flow pattern causes large side-load and high heat load to the nozzle surface. To investigate such flow pattern, cold-flow test was conducted using gaseous nitrogen. Flow on the nozzle surface was visualized by using shear sensitive liquid crystal. As a result, separation bubbles on the nozzle surface was visualized at first time in the world. Visualized images were reasonable compared with shear stress distributions obtained by CFD.

スクラムジェットエンジンのマッハ４燃焼・不始動遷移模擬実験 エンジン内流れ場の観察

Combustion and unstart processes of a scramjet engine in Mach 4 flight condition were investigated experimentally focusing on the changes of the engine internal flow structures under the ‘weak’ and ‘intensive’ combustion modes. Cold flow tests were carried out using a 1/5-scale model of the scramjet engine examined in the firing tests at Ramjet Engine Test Facility (RJTF). Pressure rise due to combustion was successfully simulated by a flow-plug installed in the engine nozzle section to demonstrate good agreement with the wall pressure distributions of the engine under ‘weak’ and ‘intensive combustion’ modes. Especially, upper limit of the combustor maximum pressure at which engine fell into unstart was exactly simulated. This limit value was revealed to be the separation pressure of the turbulent boundary layer in the isolator. Shadowgraph visualization demonstrated that in the intensive combustion mode large-scale boundary layer separation was formed over the isolator, backward facing step and constant area combustor.

Numerical and Experimental Investigation of Unsteady Flow Interaction in a Low-Pressure Multistage Turbine

This paper presents results of unsteady viscous flow calculations and corresponding cold flow experiments of a three-stage low-pressure turbine. The investigation emphasizes the study of unsteady flow interaction. A time-accurate Reynolds-averaged Navier–Stokes solver is applied for the computations. Turbulence is modeled using the Spalart–Allmaras one-equation turbulence model and the influence of modern transition models on the unsteady flow predictions is investigated. The integration of the governing equations in time is performed with a four-stage Runge–Kutta scheme, which is accelerated by a two-grid method in the viscous boundary layer around the blades. At the inlet and outlet, nonreflecting boundary conditions are used. The quasi-three-dimensional calculations are conducted on a stream surface around midspan, allowing a varying stream tube thickness. In order to study the unsteady flow interaction, a three-stage low-pressure turbine rig of a modern commercial jet engine is built up. In addition to the design point, the Reynolds number, the wheel speed, and the pressure ratio are also varied in the tests. The numerical method is able to capture important unsteady effects found in the experiments, i.e., unsteady transition as well as the blade row interaction. In particular, the flow field with respect to time-averaged and unsteady quantities such as surface pressure, entropy, and skin friction is compared with the experiments conducted in the cold air flow test rig. [S0889-504X(00)02004-3]

Improvement of Combustion Stability at Low Load for Low NOx Pulverized Coal Burner

To improve the combustion stability at lower load for a specific low NOx burner, which enabled to reduce both NOx and unburned carbon extremely, an adjustment method to raise local concentration of coal particle was invented. Coal parti-cle was concentrated at outside of primary air nozzle by using centrifugal force and coal concentration was controlled by a ring. At the outlet of nozzle, the swirl of primary air was prevented by straightener, because this swirl disturbed the forming of the reduction flame for NOx decomposition. So, the influence of straightener length and number on re-ducing the swirl was examined by cold flow test with a primary air nozzle model. Secondary, the coal concentrating effects in changing the ring position was investigated with a nozzle of combustion test burner. Finally, the combustion stability at low load was tested with the coal combustion test furnace.The swirl at the outlet decreased with the increase of the coefficient of straightener, which was defined by the ratio of the gross area of straightener to the cross section area of primary air nozzle. The swirl number was decreased to zero when the straightener coefficient is greater than 1.2. The ring placed close to the outlet concentrated coal particle most efficiently and the local pulverized coal concentration rose 1.5 times as high as the mean coal concentration in primary air. With this arrangement, the combus-tion state at lower load became stable and the minimum load was improved to 20% as same as an oil burner. At lower load, the coal concentrating was very effective to re-duce the unburned carbon with little increase of the NOx emission. On the other hand, the coal concentration was excessive when the ring was close to the outlet at higher load. So, the ring was placed far from the outlet and the coal concentrating was modified so that the emission characteristics of NOx and unburned carbon in fly ash of the burner with coal concentration adjustment was the same as the characteristics of the burner without these instruments.

97/05161 Development of the moving granular bed filter: Haas, J. C. et al. Proc. Annu. Int. Pittsburgh. Coal Conf., 1996, 13, (2), 1290–1295

The moving bed granular is being developed under the auspices of the US Dept. of Energy. Recent activity focused on three areas: the development of chemically reactive filter media for the removal of alkali and particulate from high temperature, high pressure coal gas streams; cold flow tests of filter components; and the design and fabrication of a filter for testing at DOE`s Power Systems Development Facility. Screening test of clay sorbents for alkali and selected trace metals have identified the most promising sorbents. Extrusion and disk pelletization are used to produce sorbent pellets. Results on pellet strength and reactivity are presented. Cold flow tests addressed filter scale-up issues of gas distribution, filter medium flow and filter medium size. Results from the cold flow tests have been incorporated in the design of the filter to be test at the Power System Development Test Facility.

Fluidized-bed combustion for energy production from olive cake

We present an experimental combustion study of olive-oil mill waste (olive cake, OC) in a fluidized bed combustor. Tests were performed in a 13.2-cm i.d. reactor. Cold-flow tests included investigations of the effects of particle-size distribution, fluidization velocity, and bed height. Combustion was carried out by feeding the OC in a bed of sand particles. The temperature distribution was found to become fairly uniform 12 cm above the distributor plate. The combustion intensity was about 812 kg/m 2-h and increased with bed height between 0.1 and 0.15 m. The combustion efficiency ranged from 86 to 95% and increased with air-flow rate.

Study for a Secondary Air Affecting Fluid Flow in a Solid Waste Incinerator

As the environmental pollution can be greatly reduced and the waste heat can be also recovered through a combustion of municipal solid waste, the incineration begins to be highlighted recently in our country. But it is very difficult to be operated with constant combustion conditions for a long time as the domestic waste is composed of various components, contains a large percentage of water, and has a low heating value. Therefore, the cold flow test and partial hot flow test were conducted in the incinerator by use of injection angles of a secondary air affecting fluid flow as the first action to maintain the optimum combustion conditions. A model to a scale of 1:10 was designed and manufactured through the similarity of model and prototype flows. Velocities and temperatures were measured through the experiment. From the results, fluid flows of secondary air obtained from partial hot flow test correspond almost well with those of main flow obtained from cold flow test. Consequently, injection angles of secondary air are proved to affect main flow decisively.