Engine Test Facility Research Articles

A scale model study of an engine test facility for alleviating low-frequency howl

A scale model experimental study is conducted addressing howl occurring during engine tests in the Propulsion Systems Laboratory (PSL) of NASA Glenn Research Center. The aim is to understand the sources of the howling noise and find possible remedies. It is shown that a jet discharged into the model of the PSL entrance duct gives rise to high levels of low frequency noise. This occurs apparently due to duct acoustic modes randomly excited by the jet. Wire-mesh screens of various mesh size and configuration as well as tabs, placed at the end of the model duct, are shown to affect the noise. Comparative effects of these configurations are studied, and some are found to alleviate the low-frequency noise significantly. Based on these results, the equivalent of a 4-mesh screen is recommended as the end treatment for the duct of the PSL facility.

Vibroacoustic Real Time Fuel Classification in Diesel Engine

Five models and methodology are discussed in this paper for constructing classifiers capable of recognizing in real time the type of fuel injected into a diesel engine cylinder to accuracy acceptable in practical technical applications. Experimental research was carried out on the dynamic engine test facility. The signal of in-cylinder and in-injection line pressure in an internal combustion engine powered by mineral fuel, biodiesel or blends of these two fuel types was evaluated using the vibro-acoustic method. Computational intelligence methods such as classification trees, particle swarm optimization and random forest were applied.

AUTOMATION OF TESTING AND FAULT DETECTION FOR ROCKET ENGINE TEST FACILITIES WITH MACHINE LEARNING

The German Aerospace Center (DLR) Institute of Space Propulsion has unique expertise in operating test facilities for rocket engine testing and development in Europe since 1959. However, essential elements of the test site were designed up to half a century ago. In order to ensure a futureproof and intelligent digital test infrastructure, the potential of test automation, advanced control, and monitoring systems is investigated based on machine learning. Such intelligent control systems are expected to reduce engine development and test preparation times, thereby lowering the associated costs. Additionally, advanced monitoring systems are anticipated to increase the safety and reliability of the test infrastructure. This paper presents the results of two pilot projects: the first project uses reinforcement learning to automatically generate test sequences based on test requirements, while the second project develops a feed-forward forecasting model to predict deviations from expected behavior in the feed-line of a rocket engine test facility.

EXPERIMENTAL STUDY OF THE ACOUSTIC INTERACTION OF A SUBSCALE ROCKET NOZZLE EXHAUST JET AND DIFFERENT GUIDE TUBES

The noise emission of rocket engine test facilities and their impact on the environment comes more and more into focus. The key drivers are the engine exhaust jet itself, and its interaction or even coupling with a subsequent guide tube. To increase understanding of the interaction, and in preparation of future test facility design, a cold gas subscale test campaign was conducted with a reference guide tube. It was found that the main influencing parameter is the distance between the nozzle exit and guide tube inlet. This article is published with the permission of the authors granted to 3AF - Association Aéronautique et Astronautique de France (www.3AF.fr) organizer of the Space Propulsion International Conference.

New Testbed Helps Drive Sustainable Future for Aviation

Abstract With the opening of Testbed 80, the largest engine testing facility in the world, Rolls-Royce plans to use its unique capabilities to accelerate the journey toward sustainable aviation technologies supported by the intelligent use of materials.

Analysis for design optimization of high thrust liquid engine hot test facility

A high thrust liquid oxygen-kerosene fuelled engine is being developed for future launch vehicle applications. Comprehensive hot testing of engine at sea level conditions is required for qualification and acceptance of flight engine and launch vehicle stage. The engine and stage will be tested in a specialized rocket engine and stage hot test facility which deflects the flame safely to avoid any hazard to engine and adjoining mechanical structures. The facility is equipped with water jets to sufficiently cool the rocket plume before impinging on deflector pit walls. The high temperature and high-pressure rocket exhaust jet is cooled with sufficient quantity of water to maintain the impingement wall temperature within safe working limits.In this study, a multi-phase computational fluid dynamics (CFD) methodology is developed for design of water-cooling jet configuration of deflector facility. Multi-phase model validation study using full phase treatment and droplet assumption for water injection is performed prior to water jet optimization analysis of high thrust LOX-kerosene test facility. Validation studies based on simulation and analysis of existing test stand is developed. A discrete particle (DPM) based two phase methodology is chosen to model water injection in RANS framework. The optimum cooling configuration is determined iteratively through numerous multi-phase simulations. The multi-phase analysis showed ineffectiveness of initial water injection scheme which results in facility wall temperature above safe limit. A multi-plane water injection scheme is devised there on with provision of water injection at two axial locations from the nozzle exit. A detailed parametric multi-phase analysis is carried out for design optimization of multi-plane water injection scheme and to determine thermal condition of the test facility. Analysis showed effective rocket plume cooling and lower facility wall temperature with two plane water injection schemes in comparison to initial single plane design configuration. The study highlights the role of CFD based methodology to formulate an engineering solution for design optimization of LOX-kerosene engine hot test facility.

Influence of inlet swirl on pattern factor and pressure loss in an aero engine combustor

The effect of compressor exit swirl angle (θsw) at the intake of an aero engine combustor on the exit temperature non-uniformity (pattern factor) and combustor total pressure loss is investigated. Experiments are conducted in the engine test rig, measuring the gas temperature and pressure at the inlet and exit planes of the combustor. These parameters are measured at distinct locations along the circumferential and radial directions in the engine test facility. Simulations are carried out using RANS based turbulence modeling and reacting flow approach with Ansys CFX commercial code. The predicted results are validated with experimental data at 5° swirl angle. The swirl angle at the combustor intake is further varied from 0° to 15° and 4 cases (0°, 5°, 10° and 15°) has been considered to predict the effect on the combustor pattern factor and pressure loss. The changes in the flow structure inside the combustion chamber for all these 4 cases are reported in detail. The pattern factor varies from 0.34 to 0.49 as swirl angle changes from 0° to 15°. The lowest pattern factor of 0.34 occurs at 10° swirl angle. However a linear increase in combustor total pressure loss from 5.85% to 6.53% is predicted with the change in swirl angle from 0° to 15°.

Elevated Alu retroelement copy number among workers exposed to diesel engine exhaust

BackgroundMillions of workers worldwide are exposed to diesel engine exhaust (DEE), a known genotoxic carcinogen. Alu retroelements are repetitive DNA sequences that can multiply and compromise genomic stability. There is...

A Specifically Designed Injector for Controlled Lube Oil Addition in View of Investigation of Pre-Ignition Phenomena in Dual–Fuel/Gas Engines

Internal combustion engines will continue to play a role during a transitional phase, especially in heavy-duty or marine applications. In this context, lean-burn gas/dual-fuel combustion is an attractive concept to reduce CO2, combined with considerably lower particulate and NOX pollution, and with efficiencies comparable to diesel combustion. However, ignition processes still pose considerable challenges, with pre-ignition in particular being a major issue. The underlying mechanisms are probably based on self-ignition of lube oil in hot zones. In order to investigate fundamentals of such phenomena in optically accessible test rigs, a novel injector was specifically developed to induce pre-ignitions artificially. The so-called “PieZo-Droplet-Injector” (PZDI) enables dosing of minor amounts of lubricating oil or even the injection of single droplets with diameters in the range of 100–200 µm. The working principle relies on a needle actuated with a piezo stack, which pushes a certain amount of lube oil in a bore so that (even single) droplets can be ejected through an adjustable nozzle. To confirm the PZDI functionality and to investigate droplet characteristics based on adjustable operating parameters, tests were performed under ambient conditions as well as in a constant volume combustion chamber under reasonable pressure and temperature conditions. Overall, the PZDI showed an excellent behavior in terms of capabilities to inject small amounts or even single droplets of lube oil. At last, this specially developed injector allows selective lube oil addition in an optically accessible engine test facility for upcoming examination of pre-ignition phenomena under real operating conditions.

Artificial neural network (ANN) assisted prediction of transient NOx emissions from a high-speed direct injection (HSDI) diesel engine

The understanding and prediction of NOx emissions formation mechanisms during engine transients are critical to the monitoring of real driving emissions. While many studies focus on the engine out NOx formation and treatment, few studies consider cyclic transient NOx emissions due to the low time resolution of conventional emission analysers. Increased computational power and substantial quantities of accessible engine testing data have made ANN a suitable tool for the prediction of transient NOx emissions. In this study, the transient predictive ability of artificial neural networks where a large number of engine testing data are available has been studied extensively. Significantly, the proposed transient model is trained from steady-state engine testing data. The trained data with 14 input features are provided with transient signals which are available from most engine testing facilities. With the help of a state-of-art high-speed NOx analyser, the predicted transient NOx emissions are compared with crank-angle resolved NOx measurements taken from a high-speed light duty diesel engine at test conditions both with and without EGR. The results show that the ANN model is capable of predicting transient NOx emissions without training from crank-angle resolved data. Significant differences are captured between the predicted transient and the slow-response NOx emissions (which are consistent with the cycle-resolved transient emissions measurements). A particular strength is found for increasing load steps where the instantaneous NOx emissions predicted by the ANN model are well matched to the fast-NOx analyser measurements. The results of this work indicate that ANN modelling could strongly contribute to the understanding of real driving emissions.

The ACONIT project: an innovative design approach of active flow control for surge prevention in gas turbines

The objective of the ACONIT project is to design, manufacture and test actuators for flow control for an implantation in an aircraft engine. The actuators will fulfil aeronautics requirement in order to increase the Technology Readiness Level (TRL) in this domain. In particular, for the present proposal, one plans to focus on the extension of the stable operating range of axial compressor, allowing thus a reduction of the surge margin through postponing the stall onset. To do so, the first objective of the work is to improve the knowledge of the flow physics of an efficient flow control system by joint numerical and experimental analyses performed in a low speed, single stage axial compressor. The results of this analysis will be used to derive the fluidic specifications for high-TRL actuators and control systems. These specifications will be the base for the design and manufacturing of amplified piezo-electric actuator prototypes whose fluidic performance and operational performance in an environment with vibration and controlled level of temperature will be precisely evaluated before manufacturing final actuators that will be integrated in a full-scale engine test facility. Their performance will be evaluated in terms of Surge Margin Improvement (SMI) as well as in terms of energy balance between the induced consumption and the machine performance improvements. The consortium grouped for carrying out this project is composed of a SME (CTEC), two academic institutions (Bundeswehr University Munich and ENSAM) and a Research Centre (ONERA). It groups skills ranging from internal flow analysis in turbomachinery, to flow control or actuators design, manufacturing and characterisations.

Alcohol Fuels for Spark-Ignition Engines: Performance, Efficiency, and Emission Effects at Mid to High Blend Rates for Ternary Mixtures

This paper follows on from an earlier publication on high-blend-rate binary gasoline-alcohol mixtures and reports results for some equivalent ternary fuels from several investigation streams. In the present work, new findings are presented for high-load operation in a dedicated boosted multi-cylinder engine test facility, for operation in modified production engines, for knock performance in a single-cylinder test engine, and for exhaust particulate emissions at part load using both the prototype multi-cylinder engine and a separate single-cylinder engine. The wide variety of test engines employed have several differences, including their fuel delivery strategies. This range of engine specifications is considered beneficial with regard to the “drop-in fuel” conjecture, since the results presented here bear out the contention, already established in the literature, that when specified according to the known ternary blending rules, such fuels fundamentally perform identically to their binary equivalents in terms of engine performance, and outperform standard gasolines in terms of efficiency. However, in the present work, some differences in particulate emissions performance in direct-injection engines have been found at light load for the tested fuels, with a slight increase in particulate number observed with higher methanol contents than lower. A hypothesis is developed to explain this result but in general it was found that these fuels do not significantly affect PN emissions from such engines. As a result, this investigation supplies further evidence that renewable fuels can be introduced simply into the existing vehicle fleet, with the inherent backwards compatibility that this brings too.

지상 및 고도 모사 입구 압력조건에서의 마이크로 터보젯 엔진 성능시험평가 연구

The present study investigated the performance of micro turbojet engine experimentally at various engine inlet pressure conditions, which covers the altitude up to 3.0 km. A test rig for engine performance measurements was built and installed in the altitude engine test facility located in Korea Aerospace Research Institute, and the performance tests were conducted under the altitude conditions obtained by reducing the engine inlet pressure. In this study, commercially available micro turbojet engine, Jetcat P300-RX, was used and the performance parameters, such as thrust, fuel flow rate, exhaust gas temperature, were measured for various PLA conditions at altitude simulating inlet pressure values. The results showed that as the inlet pressure becomes reduced, which means the altitude increases, the thrust and fuel flow rate of the engine decreases monotonously. For example, the thrust is 257.7N at sea level condition while it decreases to 183.7N at 3.0 km altitude condition. When the corrected performance parameters are introduced, those corrected values present single curve regardless of operating conditions. Those results will be used as the reference data not only for performance improvement of the component but also for indigenous engine development program.

Investigations of Combustor Inlet Swirl on the Liner Wall Temperature in an Aero Engine Combustor

Abstract Experimental and numerical investigations are carried out on an annular, straight flow, swirl-stabilized aero engine combustor. In this work, the effect of degree and direction of swirl at the inlet of combustion chamber is examined on the liner wall temperature and hot spots. This is carried out by experimentally measuring the liner outer wall temperature at discrete positions along the circumferential and axial directions of the combustor liner in the engine test facility. The RANS based turbulence modeling with reacting flow approach is used to simulate the flow domain. Conjugate heat transfer analysis is used to estimate the liner wall temperature using Ansys CFX frame work. The degree and direction of swirl at the inlet of combustion chamber is found to alter the velocity and temperature profiles inside the combustor and hence found to have a significant effect on the liner hot spots and its location. Hotspot with 43 % increase in temperature near the secondary zone is observed with the increase in swirl angle from 5° to 15° at the combustor inlet. The location of the hotspot is found to be dependent on the swirl direction.

Assessment of the air flowrate measurement in altitude engine tests by the national measurement standards system

The air flowrate in the engine inlet is an important parameter used to calculate common performance metrics such as the thrust and specific fuel consumption of a gas turbine engine. In the Korea Aerospace Research Institute (KARI) altitude engine test facility, air flowrates are calculated by measuring the static pressure, total pressure and temperature in an engine inlet duct. In the present study, in order to verify the air flowrate measurements at the engine inlet duct of the KARI altitude engine test facility, inlet flow measurement devices which are a total pressure rake, total temperature rake, and boundary layer rake were tested in the national measurement standards system for high pressure gas flow of the Korea Research Institute of Standards and Science (KRISS). Sonic nozzles, calibrated for flows rate up to 10000 m3/h and pressure range up to 50 bar (with an uncertainty = 0.18 %), were used as reference meters. We compared the air flowrates obtained by the area-weighted average duct Mach number in the inlet flow measurement devices of the KARI engine inlet duct to the reference flowrates of sonic nozzles at KRISS up to a Mach number of 0.15.

Genomic instability reflected by elevated Alu retroelement copy-number among workers exposed to diesel engine exhaust

OPS 44: Occupational health studies with environmental implications, Room 411, Floor 4, August 27, 2019, 4:30 PM - 5:30 PM Background/Aim: Millions of transportation and industrial workers worldwide are exposed to diesel engine exhaust (DEE), an established lung carcinogen that contains DNA-damaging constituents. Alu retroelements are repetitive DNA sequences that can multiply, insert throughout the genome, and disrupt gene expression and genomic architecture. Site-specific DNA strand breaks activate Alu retrotransposition and altered Alu repeats have been linked to cancer and mortality risk. However, whether Alu retroelements are influenced by environmental pollutants is largely unexplored. In an occupational setting with high levels of DEE, we investigated associations between personal exposure and Alu copy-number. Methods: A cross-sectional study was conducted in China with 54 DEE-exposed male workers from an engine testing facility and 55 unexposed male controls. Personal air samples were measured for elemental carbon (EC), a DEE surrogate, using NIOSH Method 5040. Leukocyte DNA was extracted from blood samples and quantitative polymerase chain reaction was used to measure Alu copy-number relative to albumin (Alb) single gene copy-number. The unitless Alu/Alb ratio reflects the average Alu copy-number. Linear regression models were used to test for differences in Alu/Alb ratio between controls and DEE-exposed workers, and to evaluate exposure–response relationships across DEE-exposure groups (i.e., controls and EC-tertiles: 6.1–39.0, 39.1–54.5, and 54.6–107.7 µg/m3) adjusted for age and smoking status. Results: DEE-exposed workers had a higher Alu/Alb ratio than unexposed controls (p=0.03). Further, we found a positive exposure-response relationship with EC (p-trend=0.02). The Alu/Alb ratio was largest among DEE-exposed workers in the highest EC-tertile versus controls (1.12+/-0.08 SD versus 1.06+/-0.07 SD, p=0.01). Age, body mass index, smoking, and work years were not associated with Alu/Alb ratio. Conclusions: Our findings suggest that increased levels of DEE exposure may contribute to genomic instability, possibly reflected by Alu copy-number. Further studies are needed to evaluate the influence of environmental pollutants on Alu copy-number in relation to carcinogenesis.

Performance Evaluation of a Rake Used for Measuring Total Pressure and Total Temperature Inside an Engine Inlet Duct

The Korea Aerospace Research Institute runs the ground-based Altitude Engine Test Facility (AETF) for simulating high-altitude environments. This facility is widely used to test the performance of gas turbine engines at ground level to high altitudes. When engine performance is tested in the AETF, total pressure and total temperature of airflow can be measured using rakes in a duct directly connected to the engine inlet. The total pressure and total temperature of airflow into an engine are the main factors affecting the thrust and specific fuel consumption rate of the engine. Furthermore, the total pressure and total temperature at the engine inlet are used as the main reference values when operating test equipment to determine the airflow rate and temperature corresponding to the performance test conditions of the engine. The performance evaluation of the rake used to measure this is crucial. Accordingly, in this study, to improve the accuracy of the total pressure and total temperature values measured using rakes, their total pressure coefficient and total temperature recovery factor are measured, and the measurement uncertainty of the total temperature recovery factor is evaluated.

A Custom, High-Channel Count Data Acquisition System for Chemical Species Tomography of Aero-Jet Engine Exhaust Plumes

The fiber-laser imaging of gas turbine exhaust species project aims to provide a video-rate imaging (100 frames/s) diagnostic tool for application to the exhaust plumes of the largest civil aero-jet engines. This remit, enabled by chemical species tomography (CST) currently targeting carbon dioxide (CO2), requires system design that facilitates expansion of multiple parameters. Scalability is needed in order to increase imaging speeds and spatial resolutions and extends the system toward other pertinent gases such as the oxides of nitrogen and sulfur and unburnt hydrocarbons. This paper presents a fully scalable, noninvasive instrument for installation in a commercial engine testing facility, technical challenges having been tackled iteratively through bespoke optical and mechanical design, and it specifically presents the high-speed data acquisition (DAQ) system required. Measurement of gas species concentration is implemented by tunable diode laser absorption with wavelength modulation spectroscopy (TDLAS-WMS) using a custom, high-speed 10–40-MS/s/channel 14-bit DAQ. For CO2 tomography, the system uses six angular projections of 21 beams each. However, the presented DAQ has capacity for 192 fully parallel 10-Hz–3-MHz differential inputs, achieving a best-case signal-to-noise ratio (SNR) of 56.5 dB prior to filtering. A 12 Ethernet-connected digitization nodes based on field-programmable gate array technology with software control are distributed around a 7-m-diameter mounting “ring.” Hence, the high data rates of 8.96-Gb/s per printed circuit board and 107.52 Gb/s for the whole system can be reduced by using local digital lock-in amplifiers. We believe that this DAQ system is unique in both the TDLAS and CST literatures.

Development of treatment media for advanced stormwater treatment at an industrial site

Abstract The Santa Susana Field Laboratory (SSFL) occupies about 2,850 acres and is located in Ventura County, California. The site is jointly owned by the Boeing Company and the federal government (the National Aeronautics and Space Administration administers the federal portion of the property). Much of the site was historically used as a rocket engine testing and energy research facility from 1949 to 1998. The site stormwater discharges are permitted by the Los Angeles Regional Water Quality Control Board through an individual industrial NPDES permit that includes numeric effluent limits for a wide range of constituents, including dioxins and metals. A large portion of the site uses distributed source stormwater controls with natural treatment systems utilizing chemically active media. As part of this approach, extensive research was conducted to develop a robust media for use in these controls to meet the discharge objectives. This paper describes the development of the media and its characteristics.

A physics-based model for real-time prediction of ignition delays of multi-pulse fuel injections in direct-injection diesel engines

Real-time prediction of in-cylinder combustion parameters is very important for robust combustion control in any internal combustion engine. Very little information is available in the literature for modeling the ignition delay period of multiple injections that occur in modern direct-injection diesel engines. Knowledge of the ignition delay period in diesel engines with multiple injections is of primary interest due to its impact on pressure rise during subsequent combustion, combustion noise and pollutant formation. In this work, a physics-based ignition delay prediction methodology has been proposed by suitably simplifying an approach available in the literature. The time taken by the fuel-spray tip to reach the liquid length is considered as the physical delay period of any particular injection pulse. An equation has been developed for predicting the saturation temperature at this location based on the temperature and pressure at the start of injection. Thus, iterative procedures are avoided, which makes the methodology suitable for real-time engine control. The chemical delay was modeled by assuming a global reaction mechanism while using the Arrhenius-type equation. Experiments were conducted on a fully instrumented state-of-the-art common-rail diesel engine test facility for providing inputs to develop the methodology. The thermodynamic condition before the main injection was obtained by modeling the pilot combustion phase using the Wiebe function. Thus, the ignition delays of both pilot and main injections could be predicted based on rail pressure, injection timing, injection duration, manifold pressure and temperature which are normally used as inputs to the engine control unit. When the methodology was applied to predict the ignition delays in three different common-rail diesel engines, the ignition delays of pilot and main combustion phases could be predicted within an error band of ±25, ±50 and ±80 µs, respectively, without further tuning. This method can hence be used in real-time engine controllers and hardware-in-the-loop systems.