Philip K. Panicker

Application of a Pulsed Detonation Engine for Electric Power Generation

A compact sized PDE with an i.d. of 0.75 in. and length of 1 m was paired with an automotive turbocharger. The turbine-compressor shaft was used to drive a small ac generator by means of speed reduction wheels. The PDE was tested with propane-oxygen mixture at 15 Hz for a period of about 20 s. The turbine spun up to a speed of 127,000 rpm, whilst the generator produced electric power at 27 W and the compressor pumped air at a rate of 0.055 kg/s. The exhaust of the turbine was measured to be 800 C, which implies that the exhaust has enough enthalpy to drive a few more turbine stages. The radial turbine results in more losses as it diverts the flow by 90 and its housing also creates hot spots. Axial turbines are better suited for application with PDEs and also enable better speed reduction gearing mechanisms to be applied, allowing larger and heavier generators to be used with turbines. The turbocharger did not exhibit any signs of damage after several minutes of testing. In subsequent tests with the PDE, detonations were observed for H2-O2 mixtures, but H2-Air mixtures failed to detonate.

Experimental study on Deflagration-to-Detonation Transition Enhancement Methods in a PDE

An experimental investigation was carried out to study the performance of a pulse detonation engine platform incorporating commercial, off-the-shelf solenoid valve gas injectors and non-conventional deflagration-to-detonation transition enhancing devices. The study made use of stoichiometric propane-oxygen mixtures with low-energy ignition sources. The gas injectors were observed to be sufficiently robust and operated reliably under the high working temperature and pressure conditions normally associated with pulsed detonation operations provided appropriate preventive measures were taken. One of the major motivations in utilizing these gas injectors lies in the ease and accuracy in controlling their injection operations electronically, which allows for tight integration with auxiliary electronic control and measurement systems. This paper reports on the initial success of integrating these gas injectors into a moderate-frequency pulsed detonation engine system as well as the effectiveness of the deflagration-to-detonation transition enhancing devices which included Shchelkin spiral, circumferential and helical grooves, as well as convergentdivergent throats. Lastly, operational insights in the practical use of gas injectors and the impact on pulse detonation operations are highlighted.

Supersonic blowdown wind tunnel control using LabVIEWTM

A computer-based, proportional-integral control system for supersonic blowdown wind tunnels was developed in a LabVIEW environment. The control algorithm is based on numerically integrating the differential equations used to model a supersonic blowdown wind tunnel in which the proportional and integral control terms were added and tuned in a simulation to determine their appropriate values. Values for these control terms can be obtained using a spreadsheet allowing for variation of the test section Mach number, test section area, stagnation pressure and plenum chamber volume as well as the pressure, temperature and volume of the storage tank. Accounting for the variation of many terms allows the control terms and resulting LabVIEW program to be easily integrated across different facilities. Experimental verification is provided along with a discussion of control valve calibration, optimization of control constants and additional capabilities of LabVIEW.

Operational Issues Affecting the Practical Implemenatation of Pulse Detonation Engines

Pulsed detonation engines are slated to be the engines of the future promising better efficiencies and high Mach number applications. There are presently many centers of experimental PDE studies around the world. Most of the studies involve single shot and very short duration test runs. This paper looks at some of the issues faced by engineers studying PDEs, including issues that prevent longer duration testing, and offers some solutions that were developed during several years of PDE study. Some of the concerns investigated include the possibility of damage to the combustion chamber, auxiliary components, diagnostic devices, valves, ignition plugs and DDT enhancing devices, such as Shchelkin spirals, due to the innate extreme conditions of high heat and pressures found in PDEs. Viable solutions are offered that may help overcome these difficulties. Commercial solenoid valves and electronic fuel injectors are presented as the means to achieving higher operational frequencies. In addition, their modularity, low costs and their ability for precision digital control are clear advantages over heavier, more complex rotary or mechanical valving systems. Issues concerning data acquisition, such as proper implementing procedures for pressure transducers and choosing the appropriate sampling rates are discussed. A common concern during the data acquisition is the management of large amounts of data. Some simple and cost effective answers are proposed, such as implementing RAID for computing. EMI is a big concern for engineers in PDE studies because the instruments and devices used in the laboratories are sources of noise. Several solutions are pointed out to mitigate the effects of noise on the signals. Noise control should be looked at proactively during the design stage of the experimental set up because failing to do so can mean retroactive and sometimes costly modifications to experimental setup. Finally, some steps to improve safety during PDE studies are presented.

PRACTICAL ISSUES IN GROUND TESTING OF PULSED DETONATION ENGINES

Pulsed detonation engines can potentially revolutionize aerospace propulsion and they are the subject of intense study. However, most of the studies involve single shot and very short duration test runs. Some of the practical issues in developing PDEs are discussed from the viewpoint of developing ground-based demonstrators. This represents only the beginning of a roadmap toward the successful development of flightweight engines. Viable solutions are offered that may help overcome the difficulties posed by the high temperature and pressures on the test rig and instrumentation. Commercial solenoid valves and electronic fuel injectors are presented as means to achieving higher operational frequencies. Issues concerning data acquisition, such as proper implementing procedures for pressure transducers and choosing the appropriate sampling rates are discussed. Methods for mitigating electromagnetic interference are discussed.Copyright

Introducing Modern Laboratory Experiences to Mechanical and Aerospace Engineering Students

Amongst some of the more challenging aspects of engineering education is in imparting hands-on experience for the students. Despite the fact that engineering requires practical know-how, this challenge is in itself being compromised as the engineering curriculum over the past few decades increasingly moves away from workshops and laboratories toward classroom lectures and dependence on computer-based training. This paper describes a laboratory experience early in a mechanical and aerospace engineering student’s career which provides an adequate preparation for understanding all aspects of modern digital data acquisition systems. This laboratory experience is coupled with classroom lectures and projects. The laboratories comprise of modules that cover a variety of topics which expose the students to digital data acquisition techniques, data processing and analysis, uncertainty analysis and comparison with theory. Moreover, instead of generic experiments, most of the experiments were built around ordinary items and processes. The laboratory experience is based around National Instruments hardware, controlled via LabVIEW™. Data processing is via MS EXCEL. These platforms are ubiquitous and provide good exposure to similar hardware and software.Copyright

Acquiring Torque and Rotational Speed Data From a Stationary Bicycle for Undergraduate Teaching

A laboratory module was recently developed for an introductory experimental course for sophomore mechanical and aerospace engineering students. The goal of this laboratory is to provide the students with an understanding of digital data acquisition systems for measuring torque and angular velocity in real time. The laboratory comprises of a stationary exercise bicycle, adapted to house a torquemeter on its front axle, an optical tachometer, the data acquisition system and software which converts a computer into a virtual instrument. A group of two or three students is rotated through the laboratory as part of a larger number of laboratory modules. The students access the experiment via the virtual instrument. The experiment requires a student to ride the bicycle. The data acquired are then subsequently analyzed by the students who are required to write individual laboratory reports.Copyright