Inyoung Yang

Effect of Combustor Configuration on Flow and Combustion in a Scramjet Engine

O PERATION of a scramjet engine involves many gas dynamic and combustion phenomena. The components of a scramjet engine, such as the intake, isolator, fuel injector, and flame holder, interact with each other in a complicated manner and may result in successful engine operation or fall into intake unstart, misfire, blowout, or thermal choking. Much of the previous experimental research on scramjets focuses on a single component, and examples of experimental research on the integrated intake, isolator, and combustor are fewer.Moreover, much research uses impact facilities, i.e., shock tubes or shock tunnels, and sometimes they cannot represent real operational conditions of the scramjet engine. For an example, some research shows that the scramjet intake starts more easily in impact facilities than in continuous facilities [1]. In this study, the effect of the combustor configuration on the flow and combustion in a scramjet engine is explored experimentally. A blowdown freejet-type continuous facility is used.A scramjet engine, in an integrated form of an intake, isolator, and combustor, is used as the test model. Fuel injector, cavity flame holder, and combustor configurations are changed for respective experiments. Through this experiment, some aspects of the relationships between the scramjet engine injector, cavity, and combustor configuration and the operational characteristics such as intake starts and unstarts, supersonic combustion, and combustion-driven unstarts are brought to light.

Uncertainty Analysis and ANOVA for the Measurement Reliability Estimation of Altitude Engine Test

The altitude engine test is carried out to measure the performance of the engine of flight vehicle at the high altitude environment prior to the flight test. During the test, The measured pressures and temperatures at various positions, air flow rate, fuel flow rate, thrust of the engine are measured. These measured values are used to calculate the representative performance values such as the net thrust and the specific fuel consumption. Hence each of the measured parameter has effects on the total uncertainly of the performance values. In this paper, the combined standard uncertainties of the net thrust and the specific fuel consumption were estimated from the uncertainties of the various measured values. Also, by estimating the repeatability and the reproducibility, the confidence levels of the altitude engine test were validated by the analysis of variation on the repeated test data by different tester groups.

Uncertainty Assessment using Monte Carlo Simulation in Net Thrust Measurement at AETF

In this paper, Monte Carlo Simulation (MCS) method was used as an uncertainty assessment tool for air flow, net thrust measurement. Uuncertainty sources of the net thrust measurement were analyzed, and the probability distribution characteristics of each source were discussed. Detailed MCS methodology was described including the effect of the number of simulation. Compared to the conventional sensitivity coefficient method, the MCS method has advantage in the uncertainty assessment. The MCS is comparatively simple, convenient and accurate, especially for complex or nonlinear measurement modeling equations. The uncertainty assessment result by MCS was compared with that of the conventional sensitivity coefficient method, and each method gave different result. The uncertainties in the net thrust measurement by the MCS and the conventional sensitivity coefficient method were 0.906% and 1.209%, respectively. It was concluded that the first order Taylor expansion in the conventional sensitivity coefficient method and the nonlinearity of model equation caused the difference. It was noted that the uncertainty assessment method should be selected carefully according to the mathematical characteristics of the model equation of the measurement.

Conceptual Design of Short-Range Two-Stage Scramjet Vehicle

§A conceptual design is carried out for a two-stage expendable scramjet cruise vehicle flying at Mach 4 to investigate its feasibility. The design goal is to deliver a payload of 225 kg and to fly a range of about 500 km. It is accelerated to its cruising speed by the first stage using an expendable rocket of 52.9 kN thrust, 3.59 m in length. The second stage cruises using a kerosene-burning scramjet engine of 6.85 kN thrust, the vehicle being 7.55 m in length and 508 mm in width. The vehicle has a take-off weight of 2.1 tons, flies a distance of 501 km in 8 minutes at 17 km altitude, and crashes at the destination. The combustor entrance Mach number is below 1.5, and flame is held by injecting silane. The airframe is made of inconel, and the skin temperature remains at a level tolerable by the material. Turn radius is sufficiently small to ensure reaching the intended destination with accuracy. Thus this vehicle is feasible with current technology.

Development of a Plate-Fin Type Gas Turbine Recuperator

A plate-fin type recuperator for a gas turbine/fuel cell hybrid power generation system was designed, manufactured, and tested. Performance analysis shows that the performance of the system is directly affected by the performance of the recuperator. Therefore, the recuperator should be designed and manufactured carefully, and its performance should be tested and verified before it is integrated into the system. In this paper, the developing procedure including designing, manufacturing, and testing of a cross flow plate-fin type recuperator was presented. Performance test results showed that the design requirements of the recuperator were almost satisfied. Based on the test results, improved design to reduce the size of the recuperator was suggested.

Uncertainty Assessment Using Monte Carlo Simulation in Gas Flow Measurement

Monte Carlo simulation(MC) method was used as an uncertainty assessment tool for gas flow measurement in this paper. Uncertainty sources for gas flow measurement were analyzed, and probability distribution characteristics of each source were discussed. Detailed MC methodology was described including the effect of the number of simulation. The uncertainty result was compared with that of the conventional sensitivity coefficient method, and it was revealed that the results were different from each other for this particular gas flow measurement case of which the modelling equation was nonlinear. The MC was comparatively simple, convenient and accurate as an uncertainty assessment method, especially in cases of complex, nonlinear measurement modelling equations. It was noted that the uncertainty assessment method should be selected carefully according to the mathematical characteristics of the measurement.

Improving the Measurement Uncertainty of Altitude Test Facility for Gas Turbine Engines

An Altitude Engine Test Facility(AETF) was built at the Korea Aerospace Research Institute in October 1999 and has been being operated for altitude testing of gas turbine engines of 3,000 Ibf class or less. The AETF has been calibrated using several engines such as J69 of Teledyne Co. as a facility checkout engine. Uncertainty analyses on the air flow rate and thrust were performed using the test results, according to ASME PTC 19.1-1998. Several modifications on the facility and test method were made in order to improve the measurement uncertainty to a satisfactory level over the whole operating envelop. Spatial distributions of pressure and temperature were measured, sensors were substituted by more accurate ones, inlet duct was modified to refine the flow quality, and pressure control logic was revised to remove the cell pressure fluctuation. As a result, the uncertainty of the air flow measurement was improved by 0.1% over all the test conditions, and the net thrust measurement by up to 3%. The improved measurement uncertainties of air flow and thrust are 0.68～O.73% and 0.4～1.3%, respectively.

Measurement Uncertainty Analysis of a Turbine Flowmeter for Fuel Flow Measurement in Altitude Engine Test

Measurement uncertainty analysis of fuel flow using turbine flowmeter was performed for the case of altitude engine test. SAE ARP4990 was used as the fuel flow calculation procedure, as well as the mathematical model for the measurement uncertainty assessment. The assessment was performed using Sensitivity Coefficient Method. 11 parameters involved in the calculation of the flow rate were considered. For the given equipment setup, the measurement uncertainty of fuel flow was assessed in the range of 1.19~1.86 % for high flow rate case, and 1.47~3.31 % for low flow rate case. Fluctuation in frequency signal from the flowmeter had the largest influence on the fuel flow measurement uncertainty for most cases. Fuel temperature measurement had the largest for the case of low temperature and low flow rate. Calibration of K-factor and the interpolation of the calibration data also had large influence, especially for the case of very low temperature. Reference temperature, at which the reference viscosity of the sample fuel was measured, had relatively small contribution, but it became larger when the operating fuel temperature was far from reference temperature. Measurement of reference density had small contribution on the flow rate uncertainty. Fuel pressure and atmospheric pressure measurement had virtually no contribution on the flow rate uncertainty.

Uncertainty Analysis and Improvement of an Altitude Test Facility for Small Jet Engines

The verification and improvement of the measurement uncertainty have been performed in the altitude test facility for small gas turbine engines, which was built at the Korea Aerospace Research Institute (KARl) in October 1999. This test is performed with a single spool turbojet engine at several flight conditions. This paper discusses the evaluation and validation process for the measurement uncertainty improvements used in the altitude test facility. The evaluation process, defined as tests before the facility modification, shows that the major contributors to the measurement uncertainty are the flow meter discharge coefficient, the inlet static and total pressures, the cell pressure and the fuel flow rate. The measurement uncertainty is focused on the primary parameters of the engine performance such as airflow rate, thrust and specific fuel consumption (SFC). The validation process, defined as tests after the facility modification, shows that the measurement uncertainty, in seal level condition, is improved to the acceptable level through the facility modification. In altitude test conditions, the measurement uncertainties are not improved as much as the uncertainty in sea level condition.

Small Turbojet Engine Test and Uncertainty Analysis

The Altitude Engine Test Facility(AETF) was built at the Korea Aerospace Research Institute and has been being operated for the gas turbine engines in the class of 3,000 lbf thrust. To enhance the confidence level of AETF to the international level, a series of studies and facility modification have been conducted to improve the measurement uncertainty and reliability. In this paper, some part of the facility evaluation tests performed with a single spool turbojet engine are introduced. Tests were performed simulating the flight conditions as steady state, sea level for various flight speeds (i.e., Mn