Jet Ignition for Super-Efficient Power Generation and Propulsion

poster abstractJet Ignition for Super-Efficient Power Generation and Propulsion Global environmental concerns and energy price hikes compel more efficient transport and power generation with disruptively different technologies. Wave rotor technology developed at IUPUI employs new combustion and ignition processes that develop high pressure and increased power resulting in enormous energy and cost savings. The wave rotor combustor (WRC) uses pressure wave compression and confined combustion in multiple rotating chambers. For ignition, partially combusted gas in a transient jet from a pre-chamber penetrates and ignites the main chamber lean mixture, over multiple ignition points. This intense ignition overcomes mixture non-uniformity and improves efficiency and emission. Chemically active radicals and fast turbulent mixing in the jets create an explosion two orders more energetic than a spark. Jet ignition offer the advantage of fast ignition and rapid complete combustion of leaner and stratified mixtures, mitigate heat losses to the walls and minimize pollutant emissions, while enabling higher engine efficiency

Wave Rotor Combustor Aerothermodynamic Design and Model Validation

poster abstractWave Rotor Combustor Aerothermodynamic Design and Model Validation based on Initial Testing. Tests of combustion in a wave-rotor constant-volume combustor (WRCVC) provided a demonstration of the potential of pressure-gain combustion using a wave rotor. Experimental data showed good agreement with numerical model predictions, validating the aerothermodynamic design of the combustor and the numerical model used. A time-dependent, one-dimensional gas dynamic and combustion model used for design of the WRCVC is shown to capture major features and trends of the measured gas dynamic and combustion processes. Experimental test cases with different configurations are shown and the results are analyzed and compared to the numerical simulations to calibrate the numerical model. Simulations discussed in the paper illustrate the likely explanations for test cases with and without evidence of combustion, and give insights into spillage during the filling process and mixture requirements for consistent torch ignition

Longitudinally Stratified Combustion in Wave Rotors

A wave rotor may be used as a pressure-gain combustor, effecting wave compression and expansion, and intermittent confined combustion, to enhance gas-turbine engine performance. It will be more compact than an equivalent pressure-exchange wave-rotor system, but will have similar thermodynamic and mechanical characteristics. Because the allowable turbine blade temperature limits overall fuel-air ratio to subftammable values, premixed stratification techniques are necessary to burn hydrocarbon fuels in small engines with compressor discharge temperatures well below autoignition conditions. One-dimensional, nonsteady numerical simulations of stratified-charge combustion are performed using an eddy-diffusivity turbulence model and a simple reaction model incorporating a flammability limit temperature. For good combustion efficiency, a stratification strategy is developed that concentrates fuel at the leading and trailing edges of the inlet port. Rotor and exhaust temperature profiles and performance predictions are presented at three representative operating conditions of the engine: full design load, 40% load, and idle. The results indicate that peak local gas temperatures will cause excessive temperatures in the rotor housing unless additional cooling methods are used. The rotor temperature will be acceptable, but the pattern factor presented to the turbine may be of concern, depending on exhaust duct design and duct-rotor interaction

Thermodynamic Limits of Work and Pressure Gain in Combustion and Evaporation Processes

Combustion and evaporation processes occurring in a closed chamber can result in significant pressure rise and direct work transfer. The pressure and volumetric changes that accompany such processes allow substantial work potential to be achieved in cyclic nonsteady devices, such as internal combustion engines and pulsed combustion or detonation engines. The ideal pressure gain or work production is a function of the prescribed inflow and outflow conditions, volumetric confinement, fluid properties, and other parameters. The generalized thermodynamic limits of pressure gain and work production in such devices are investigated. Analytic and iterative methods are provided to evaluate cyclic combustion and evaporation processes for enhancing airbreathing combustion engine performance

Pressure-Gain Combustion Clean Efficient Jet Engines and Power Plants

poster abstractThe gas turbine has been an enormously successful power plant for aircraft and marine propulsion, and electric power generation, due to its light weight, smooth and reliable operation, low emissions, and varied applications. Nevertheless, it is not very efficient in converting fuel energy to useful work, due to fundamental thermodynamic limitations imposed by turbomachinery technology. I am investigating potential alternative thermodynamic cycles and pulsed combustion systems for propulsion and gas turbine applications, developing a key new component called a wave rotor combustor

Assessment of Combustion Modes for Internal Combustion Wave Rotors

Combustion within the channels of a wave rotor is examined as a means of obtaining pressure gain during heat addition in a gas turbine engine. Three modes of combustion are assessed: premixed autoignition (detonation), premixed deflagration, and non-premixed autoignition. The last two will require strong turbulence for completion of combustion in a reasonable time in the wave rotor. The autoignition modes will require inlet temperatures in excess of 800 K for reliable ignition with most hydrocarbon fuels. Examples of combustion mode selection are presented for two engine applications

Numerical Study of Stratified Charge Combustion in Wave Rotors

A wave rotor may be used as a pressure-gain combustor effecting non-steady flow, and intermittent, confined combustion to enhance gas turbine engine performance. It will be more compact and probably lighter than an equivalent pressure-exchange wave rotor, yet will have similar thermodynamic and mechanical characteristics. Because the allowable turbine blade temperature limits overall fuel/air ratio to sub-flammable values, premixed stratification techniques are necessary to burn hydrocarbon fuels in small engines with compressor discharge temperature well below autoignition conditions. One-dimensional, unsteady numerical simulations of stratified-charge combustion are performed using an eddy-diffusivity turbulence model and a simple reaction model incorporating a flammability limit temperature. For good combustion efficiency, a stratification strategy is developed which concentrates fuel at the leading and trailing edges of the inlet port. Rotor and exhaust temperature profiles and performance predictions are presented at three representative operating conditions of the engine: full design load, 40% load, and idle. The results indicate that peak local gas temperatures will result in excessive temperatures within the rotor housing unless additional cooling methods are used. The rotor itself will have acceptable temperatures, but the pattern factor presented to the turbine may be of concern, depending on exhaust duct design and duct-rotor interaction

Preliminary assessment of combustion modes for internal combustion wave rotors

Combustion within the channels of a wave rotor is examined as a means of obtaining pressure gain during heat addition in a gas turbine engine. Several modes of combustion are considered and the factors that determine the applicability of three modes are evaluated in detail; premixed autoignition/detonation, premixed deflagration, and non-premixed compression ignition. The last two will require strong turbulence for completion of combustion in a reasonable time in the wave rotor. The compression/autoignition modes will require inlet temperatures in excess of 1500 R for reliable ignition with most hydrocarbon fuels; otherwise, a supplementary ignition method must be provided. Examples of combustion mode selection are presented for two core engine applications that had been previously designed with equivalent 4-port wave rotor topping cycles using external combustion

Thermal-Boundary-Layer Response to Convected Far-Field Fluid Temperature Changes

Fluid flows of varying temperature occur in heat exchangers, nuclear reactors, nonsteady-flow devices, and combustion engines, among other applications with heat transfer processes that influence energy conversion efficiency. A general numerical method was developed with the capability to predict the transient laminar thermal-boundary-layer response for similar or nonsimilar flow and thermal behaviors. The method was tested for the step change in the far-field flow temperature of a two-dimensional semi-infinite flat plate with steady hydrodynamic boundary layer and constant wall temperature assumptions. Changes in the magnitude and sign of the fluid-wall temperature difference were considered, including flow with no initial temperature difference and built-up thermal boundary layer. The equations for momentum and energy were solved based on the Keller-box finite-difference method. The accuracy of the method was verified by comparing with related transient solutions, the steady-state solution, and by grid independence tests. The existence of a similarity solution is shown for a step change in the far-field temperature and is verified by the computed general solution. Transient heat transfer correlations are presented, which indicate that both magnitude and direction of heat transfer can be significantly different from predictions by quasisteady models commonly used. The deviation is greater and lasts longer for large Prandtl number fluids

EXPERIMENTAL MEASUREMENTS OF FLAME TRANSFER FUNCTION

poster abstractIn order to conform to pollutant-related legislations and minimize NOx emissions, modern household boilers and central heating systems are mov-ing towards premixed combustors. These combustors have been very suc-cessful with regards to emissions along with thermal efficiency. However, there implementation has been associated with acoustical instability prob-lems that are best solved through precise design optimization rather than trial and error experimentation. This poster introduces an experimental setup which is designed to inves-tigate and study, acoustic instability at the flame level. The methodology is an experimental determination of the Flame Transfer Function and compari-son of the experimental data with a theoretical model of the flame-burner. A procedure is designed to diagnose the origins of the combustion instabilities by measurement of the Flame Transfer Function experimentally. The exper-imental setup provides an improved assessment of the acoustic instability problem for industrial applications